A bolus feeding device is disclosed that provides for more effective and convenient G-Tube feeding. The device includes a chassis that houses a chamber for storing the bolus, a trigger-piston assembly for compressing the bolus, a chamber hatch for accessing the chamber, and a dispensing unit for transferring the bolus into a G-Tube. The dispensing unit includes a port connector that connects to an enteral feeding system. The dispensing unit is configured to allow the port connector to rotate about the vertical and horizontal axes in order to minimize twisting, kinking or pulling of the G-Tube during feeding. The device also includes a collapsible funnel unit that reversibly attaches to the device for enhanced filling of the chamber.

For many, enteral tube feeding is a necessary last resort for meeting basic nutritional needs. It is a common practice for those requiring home tube feeding via a gastrostomy tube, or G-Tube, to depend on a feeding procedure carried out by a caregiver, with four to seven feeding sessions a day. This practice is referred to as bolus feeding. There are two common delivery methods for bolus delivery: gravity gavage and syringe depression ("push-method"). Both of these methods currently use identical medical equipment and suffer from numerous disadvantages. The experience of assisted G-Tube feeding involves a cumbersome, often messy technique of pouring a fluid bolus into a syringe and channeling the bolus/fluid into a tube that is connected to the patient using standardized connective components. Both methods typically use limited capacity 60 ml irrigation syringes (2 oz.). The current syringes need to be refilled 5-6 times during a feeding session in order to deliver the requisite bolus volume, with even more refills for the greater caloric needs of adults. The current G-Tube feeding experience is often very demanding for the caregiver due to a poor ergonomic configuration. In particular, the caregiver commonly suffers joint injury (e.g., carpometacarpal or ulnocarpal joint injury) from the repeated motion of holding the syringe while manipulating the plunger. The current process lacks the necessary flexibility, control, and ergonomics necessary to prevent repetitive stress injuries.
The problem of food spillage during syringe filling is a common and unpleasant aspect of the feeding process. Moreover, the repeated twisting or kinking of the G-Tube can impede bolus flow, damage equipment or cause disengagement of the G-Tube from the syringe or the patient. Importantly, the patient currently suffers the consequences of poor movement stabilization at the G-Tube connection site because they feel every movement from the caregiver as they try to remain stationary. This unavoidable movement often leads to skin irritation and early G-Tube failures. In short, current methods generally require cumbersome manipulation, cause joint injury, and are prone to messy accidents that diminish the quality of life for both the patient and caregiver. There is a need in the art for an alternative method of enteral tube feeding, one that is more convenient, controlled, and reduces the number of requisite devices and steps for feeding.


The subject invention provides R(+)-N-propargyl-1-aminoindan and pharmaceutically acceptable salts thereof, as well as pharmaceutical compositions containing same. The subject invention also provides methods of treating a subject afflicted with Parkinson's disease, a memory disorder, dementia, depression, hyperactive syndrome, an affective illness, a neurodegenerative disease, a neurotoxic injury, brain ischemia, a head trauma injury, a spinal trauma injury, schizophrenia, an attention deficit disorder, multiple sclerosis, or withdrawal symptoms, using R(+)-N-propargyl-1-aminoindan or the pharmaceutically acceptable salt of the subject invention. The subject invention further provides a method of preventing nerve damage in a subject. Finally, the subject invention provides methods of preparing R(+)-N-propargyl-1-aminoindan, a salt thereof, and racemic N-propargyl-1-aminoindan.

I.
The subject invention is in the field of selective irreversible inhibitors of the enzyme monoamine oxidase (hereinafter MAO) and provides the [R](+)enantiomer of N-propargyl-1-aminoindan (also referred to herein as PAI) which is a selective irreversible inhibitor of the B-form of monoamine oxidase enzyme (hereinafter MAO-B). The subject invention also provides pharmaceutical compositions containing [R](+)PAI which are particularly useful for the treatment of Parkinson's disease, a memory disorder, dementia, depression, hyperactive syndrome, an affective illness, a neurodegenerative disease, a neurotoxic injury, brain ischemia, a head trauma injury, a spinal trauma injury, schizophrenia, an attention deficit disorder, multiple sclerosis, and withdrawal symptoms.

Esylate and sulfate salts of R(+)-N-propargyl-1-aminoindan

Technion Research and Development Foundation, Ltd.


The present invention relates to the conjugation of Factor VII polypeptides with heparosan polymers. The resultant conjugates may be used to deliver Factor VII, for example in the treatment or prevention of bleeding disorders.

An injury to a blood vessel activates the haemostatic system that involves complex interactions between cellular and molecular components. The process that eventually causes the bleeding to stop is known as haemostasis. An important part of haemostasis is coagulation of the blood and the formation of a clot at the site of the injury. The coagulation process is highly dependent on the function of several protein molecules. These are known as coagulation factors. Some of the coagulation factors are proteases which can exist in an inactive zymogen or an enzymatically active form. The zymogen form can be converted to its enzymatically active form by specific cleavage of the polypeptide chain catalyzed by another proteolytically active coagulation factor. Factor VII is a vitamin K-dependent plasma protein synthesized in the liver and secreted into the blood as a single-chain glycoprotein. The Factor VII zymogen is converted into an activated form (Factor VIIa) by specific proteolytic cleavage at a single site, i.e. between R152 and I153 of the Factor VII sequence (wild type human coagulation Factor VII) resulting in a two chain molecule linked by a single disulfide bond. The two polypeptide chains in Factor VIIa are referred to as light and heavy chain, corresponding to residues 1-152 and 153-406, respectively, of the Factor VII sequence. Factor VII circulates predominantly as zymogen, but a minor fraction is on the activated form (Factor VIIa).
The blood coagulation process can be divided into three phases: initiation, amplification and propagation. The initiation and propagation phases contribute to the formation of thrombin, a coagulation factor with many important functions in haemostasis. The coagulation cascade starts if the single-layered barrier of endothelial cells that line the inner surface of blood vessels becomes damaged. This exposes subendothelial cells and extravascular matrix proteins to which platelets in the blood will stick to. If this happens, Tissue Factor (TF) which is present on the surface of sub-endothelial cells becomes exposed to Factor VIIa circulating in the blood. TF is a membrane-bound protein and serves as the receptor for Factor VIIa. Factor VIIa is an enzyme, a serine protease, with intrinsically low activity. However, when Factor VIIa is bound to TF, its activity increases greatly. Factor VIIa interaction with TF also localizes Factor VIIa on the phospholipid surface of the TF bearing cell and positions it optimally for activation of Factor X to Xa. When this happens, Factor Xa can combine with Factor Va to form the so-called "prothombinase" complex on the surface of the TF bearing cell. The prothrombinase complex then generates thrombin by cleavage of prothrombin. The pathway activated by exposing TF to circulating Factor VIIa and leading to the initial generation of thrombin is known as the TF pathway. The TF:Factor VIIa complex also catalyzes the activation of Factor IX to Factor IXa. Then activated Factor IXa can diffuse to the surface of platelets which are sticking to the site of the injury and have been activated. This allows Factor IXa to combine with FVIIIa to form the "tenase" complex on the surface of the activated platelet. This complex plays a key role in the propagation phase due to its remarkable efficiency in activating Factor X to Xa. The efficient tenase catalyzed generation of Factor Xa activity in turn leads to efficient cleavage of prothrombin to thrombin catalyzed by the prothrombinase complex.
If there are any deficiencies in either Factor IX or Factor VIII, it compromises the important tenase activity, and reduces the production of the thrombin which is necessary for coagulation. Thrombin formed initially by the TF pathway serves as a pro-coagulant signal that encourages recruitment, activation and aggregation of platelets at the injury site. This results in the formation of a loose primary plug of platelets. However, this primary plug of platelets is unstable and needs reinforcement to sustain haemostasis. Stabilization of the plug involves anchoring and entangling the platelets in a web of fibrin fibres.
The formation of a strong and stable clot is dependent on the generation of a robust burst of local thrombin activity. Thus, deficiencies in the processes leading to thrombin generation following a vessel injury can lead to bleeding disorders e.g. haemophilia A and B. People with haemophilia A and B lack functional Factor VIIIa or Factor IXa, respectively. Thrombin generation in the propagation phase is critically dependent of tenase activity, i.e. requires both Factor VIIIa and FIXa. Therefore, in people with haemophilia A or B proper consolidation of the primary platelet plug fails and bleeding continues.
Replacement therapy is the traditional treatment for hemophilia A and B, and involves intravenous administration of Factor VIII or Factor IX. In many cases, however, patients develop antibodies (also known as inhibitors) against the infused proteins, which reduce or negate the efficacy of the treatment. Recombinant Factor VIIa (Novoseven®) has been approved for the treatment of hemophilia A or B patients that have inhibitors, and also is used to stop bleeding episodes or prevent bleeding associated with trauma and/or surgery. Recombinant Factor VIIa also has been approved for the treatment of patients with congenital Factor VII deficiency. It has been proposed that recombinant FVIIa operates through a TF-independent mechanism. According to this model, recombinant FVIIa is directed to the surface of the activated blood platelets by virtue of its Gla-domain where it then proteolytically activates Factor X to Xa thus by-passing the need for a functional tenase complex. The low enzymatic activity of FVIIa in the absence of TF as well as the low affinity of the Gla-domain for membranes could explain the need for supra-physiological levels of circulating FVIIa needed to achieve haemostasis.
Recombinant Factor VIIa has a pharmacological half-life of 2-3 hours which may necessitate frequent administration to resolve bleedings in patients. Further, patients often only receive Factor VIIa therapy after a bleed has commenced, rather than as a precautionary measure, which often impinges upon their general quality of life. A recombinant Factor VIIa variant with a longer circulation half-life would decrease the number of necessary administrations and support less frequent dosing thus hold the promise of significantly improving Factor VIIa therapy to the benefit of patients and care-holders.
In general, there are many unmet medical needs in people with coagulopathies. The use of recombinant Factor VIIa to promote clot formation underlines its growing importance as a therapeutic agent. However, recombinant Factor VIIa therapy still leaves significant unmet medical needs, and there is a need for recombinant Factor VIIa polypeptides having improved pharmaceutical properties, for example increased in vivo functional half-life, improved activity, and less undesirable side effects.
Various methods have been employed in the development of a Factor VII polypeptide with prolonged circulatory half-life. Some of these methods relate to conjugation of Factor VII with water soluble polymers such as PEG (poly ethylene glycol). WO03031464 disclose an enzymatic approach where PEG groups can be attached to glycans present on the polypeptide.

This patent is subject to a terminal disclaimer.


A lift indicator assembly for a pallet truck includes a lift sensor assembly, and a lift status display for determining a lift condition of a load wheel of the pallet truck. The lift sensor assembly is to be carried by a fork of the pallet truck and includes a housing section, and a primary sensor assembly. The primary sensor assembly includes a first primary arm coupled to the housing section, and a first primary contact switch carried by the housing section and adjacent the first primary arm. The first primary contact switch has an engaged position and a disengaged position based on position of the first primary arm. The lift status display determines the lift condition of the load wheel based on position of the first primary contact switch.

Pallet trucks are commonly used to load and unload pallets from a truck. A typical pallet includes a bottom deck, a top deck and support blocks. The support blocks are coupled between the bottom and top decks and define an opening therebetween for receiving lifting members of material handling equipment, such as forks from a pallet truck.
A typical pallet truck includes a cab, a vertical load plate on a front end of the cab, and a pair of forks or tines extending outwards from a lower end of the vertical load plate in a substantially horizontal direction. A load wheel is in each fork. The load wheel may also be referred to as a lift wheel. Each load wheel is coupled to a respective load wheel linkage that is pivotally coupled to the fork. The maximum lift of the forks may vary depending on the pallet truck, but a typical lift height is about 6 inches.
When an operator of the pallet truck extends the forks into an opening of a pallet, the operator cannot readily observe the position of the load wheels because of the boards in the top deck of the pallet and any load carried on the top deck. If the load wheels come to rest on a bottom deck board of the pallet, then downward movement of the load wheels to lift the forks results in separation of the bottom deck board from the pallet.
One approach to this problem is to mount light sensors on at least one of the forks, as disclosed in U.S. Pat. No. 4,747,610. The light sensors detect the positions of the load wheels with respect to the bottom deck boards of the pallet. A disadvantage of light sensors is that they may fail to properly operate due to blockage of the light beams by dirt and debris.

Pallet truck with lift indicator assembly and associated methods


A light-emitting element mounting substrate (20) in which a surface of a core metal (21) is coated with an enamel layer (22), and a reflective concave portion (23) for mounting a light-emitting element is provided, wherein a groove (24) is provided around the reflective concave portion.

A light-emitting element is normally mounted on a substrate and moreover packaged by sealing the light-emitting element with a transparent resin in order to protect it from the external environment such as external forces and humidity and the like. In addition, a convex part of a lens is sometimes formed on the upper portion of the sealing resin in order to perform control such as converging and diffusing of light that is emitted from the light-emitting element. To form such a lens shape, for example, the resin is raised by surface tension prior to curing and subjected to heat curing or ultraviolet curing while maintaining that shape, whereby it is possible to finish the upper portion of the sealing resin in a lens shape (for example, refer to Patent Document 1).
In the method of manufacturing this kind of lens shape, the amount of raising of the resin to be raised is significantly affected by the wettability of the substrate and resin. For example, due to variations in the surface condition of the substrate and the like, when the coating amount of the sealing resin is excessive or the wettability of the substrate surface is high, the resin may flow out on the upper surface of the substrate prior to curing. Removing his resin takes time and effort, and sometimes the resin that has flowed out may cover electrodes that are provided on the substrate side face. In the case of attempting to anchor the substrate by soldering, the resin that has become attached to the electrodes may act as an electrical insulating film, leading to the problem of poor electrical conduction.
In recent years, the application of LEDs has advanced to lighting uses and traffic signals, and further improvements in luminescence intensity are demanded. By increasing the amount of electrical current that is impressed, it is possible to increase the luminescence intensity of an LED. However, in this case, it is necessary for the light-emitting element to efficiently dissipate the heat because the light-emitting element accompanies the heat generation simultaneously. In the case of the heat dissipation being insufficient, the light-emitting element reaches a high temperature when lit. As a result, the light-emitting efficiency falls and so the target luminescence intensity is no longer obtained. Also, when used over a long period, the reliability of the LED falls, and the possibility of malfunction such as non-lighting increases.
In addition, in order to efficiently emit the light forward that is radiated from the light-emitting element, it is preferable to provide a reflective concave portion as shown in FIG. 4. The package structure of the light-emitting element shown in FIG. 4 uses a package 1 that has a reflective concave portion 2 with a mortar-like shape, electrodes 3 of which a portion thereof extends into the reflective concave portion 2, and a light-emitting element 4 such as an LED mounted on one electrode 3 in the reflective concave portion 2 of this package 1. The light-emitting element 4 and the other electrode 3 are electrically connected by a gold wire 5, and a sealing resin 6 is filled in the reflective concave portion 2 so that the upper portion rises upward, and then cured so as to form a lens shape. In the light source of this package structure, the light-emitting element 4 is lit up by electrical conduction between the electrodes 3, and a portion of the light that is generated from the light-emitting element 4 is directly emitted while the other portion is emitted by being reflected by the reflective concave portion 4. Therefore, it is possible to efficiently emit the light that is generated from the light-emitting element 4 to the front of the package.
Patent Document 1: Japanese Unexamined Patent Application, First Publication No. H09-153646

Light-emitting element mounting substrate, light source, lighting device, display device, traffic signal, and method of manufacturing light-emitting element mounting substrate


A brachytherapy system includes a brachytherapy applicator. The brachytherapy applicator includes an applicator tube and a radiation source configured to deliver radiation to a tumor. At least a portion of the applicator tube is configured to conform to at least a portion of a patient's anatomy. At least one ultrasound element or probe is coupled to or embedded with the applicator tube.

Brachytherapy is a type of radiation therapy that has proven efficacy for treating a variety of types of cancers, such as cervical cancer. In brachytherapy procedures, radiation is delivered to cancerous regions by positioning a radiation source in close proximity to a tumor, typically by using a physical applicator equipped with a radiation source. Brachytherapy procedures may offer advantages over external beam radiation therapies by enabling improved targeting of cancerous cells, thus reducing the likelihood that healthy cells are radiated during treatment.
Development of a conformal dose plan for cervical cancer patients receiving brachytherapy is typically guided by images obtained via one or more imaging modalities. For example, in some instances, two-dimensional (2D) X-ray imaging may be chosen for treatment planning due to its low cost and minimal impact on the workflow. However, since the information available through 2D X-ray imaging is inherently limited due to its 2D nature (e.g., it may be possible to visualize the applicator but not the patient's anatomy), many dose plans are based on one or more types of three-dimensional (3D) imaging modalities. For instance, magnetic resonance imaging (MRI) and computed tomography (CT) may be used to gain a greater depth of information than would be acquired with 2D X-ray imaging.
However, image-guided 3D conformal dose planning with MRI and/or CT introduces significant monetary costs, accessibility difficulties, and lengthened procedure times. For example, the imaging department in a hospital is typically located in a different area than the treatment department, thus requiring time and expenses associated with patient transport and facilities planning. In an attempt to overcome these difficulties, trans-abdominal ultrasound (TAUS) and trans-rectal ultrasound (TRUS) modalities have been developed. Unfortunately, TAUS does not enable visualization of the anatomy of interest since the rectum, bowel, applicator, and needles may not be visible in the acquired images. Similarly, TRUS may not enable visualization of the bladder, bowel, and applicator. Further, combining TAUS and TRUS presents alignment and calibration difficulties, in addition to introducing undesirable workflow complexity in the operating room. Additionally, air present in the field of view complicates the use of ultrasonic modalities.
Accordingly, there exists a need for improved imaging systems that enable image-guided brachytherapy treatment of cervical cancer while addressing one or more of these drawbacks.

Brachytherapy applicators having ultrasound elements


Novel fabric conditioners based on pyridine carboxylic acid esters or amides are described. The compounds are effective fabric conditioners and are biodegradable. Compositions including the compounds and a method of using the compositions are also described.

Quaternary ammonium salts such as N,N-di(tallowoyl-oxy-ethyl)-N,N,-dimethylammonium chloride and 1,2 ditallowyl oxy-3-trimethylammino propane chloride have been developed as described in U.S. Pat. Nos. 4,137,180; 4,767,547 and 4,789,491.
Because of softening properties and ease of processing, a preferred biodegradable quaternary ammonium salt is a diester compound of the formula described in Column 1 of U.S. Pat. No. 4,137,180.
It has been discovered, however, that many of the diester compounds described above degrade to a monoester form which in certain levels can be aquatically toxic. Moreover, when the diester compounds are processed with relatively large quantities of alcohol the obtained compounds are more likely to form monoester degradation intermediates.
Therefore, there is a need for novel molecules which are both effective fabric conditioners and which are biodegradable.
There is further a need for a fabric conditioning molecule which is formed from compounds having a natural rather than a synthetic source.

Fabric conditioners derived from pyridine carboxylic acids

Lever Brothers Company, Division of Conopco, Inc.


An industrially feasible method of grinding silicon nitride ceramics is disclosed and provides a sufficiently smooth surface. Namely, the surface has a maximum height-roughness Rmax of 0.1 microns or less and a ten-point mean roughness Rz of 0.05 micron. Further, with this method, surface damage can be repaired while grinding. The vertical cutting feed rate of a grinding wheel into a workpiece should be within the range of 0.005-0.1 micron for each rotation of the working surface of the wheel and change linearly or stepwise. The cutting speed of the grinding wheel in a horizontal (rotational) direction should be within the range of 25 to 75 m/sec. With this arrangement, the contact pressure and grinding heat that is generated between the workpiece and the hard abrasive grains during grinding are combined. In other words, mechanical and thermal actions are combined.

The present invention relates to a method of machining silicon nitride ceramics and silicon nitride ceramic products, specifically sliding parts which are brought into frictional contact with metal parts at high speed, such as adjusting shims, rocker arms, roller rockers, cams, piston rings, piston pins and apex seals, and bearing parts such as slide bearings and roller bearings.
Silicon nitride ceramics are known to have excellent mechanical properties in hardness, strength, heat resistance, etc. and possess a big potential as materials for mechanical structures. But silicon nitride ceramics are typically hard but brittle materials. Therefore, it is required to select an appropriate machining method for providing a geometric shape as required by the end products and also to improve the strength and durability of the finished products.
At the present time, the best-used method for machining silicon nitride ceramics is grinding with a diamond grinding wheel. But this method tends to leave damage such as cracks on the machined surface, which will lower the strength and reliability. This has been a major obstacle to the application of these materials.
For example, as Ito points out (in a book titled "Recent Fine Ceramics Techniques", page 219, published by Kogyo Chosakai in 1983), there is a correlation between the surface roughness of silicon nitride ceramics machined by grinding and the bending strength and it is required to keep the surface roughness below 1 micrometer to ensure reliability in strength. Also, as has been pointed out by Yoshikawa (FC report, vol 8, No. 5, page 148, 1990), the depth of cracks formed when grinding depends on the grain size of the diamond grinding wheel used. Such cracks formed in silicon nitride ceramics materials may be as deep as 20-40 micrometers (or microns). Cracks of this order can make the end product totally useless.
As shown in Japanese Patent Unexamined Publication 63-158070, silicon nitride ceramics having a bending resistance of 100 kg/mm.sup.2 or more under JIS R1601 are especially difficult to grind with an ordinary diamond grinding wheel. Also, the possibility of causing surface damage increases.
It is known to finish a surface damaged by normal grinding with a diamond grinding wheel by polishing or lapping with abrasive grains to remove any damaged surface and thus to increase the strength of the product. But such a method is extremely problematic from an economical viewpoint.
But the grinding method using a diamond grinding wheel is superior in flexibility of machining facility and machining cost. Thus, it is essential to establish a method of grinding silicon nitride ceramics with a diamond grinding wheel without the fear of surface damage. One way to remove the influence of surface damage was disclosed Kishi et al ("Yogyo Kyokai Shi", vol. 94, first issue, page 189, 1986), in which after grinding .beta.-Sialon, a silicon nitride ceramic, it is subjected to heat treatment at 1200.degree. C. in the atmosphere to form an oxide layer on its surface to fill the damaged parts with the layer and improve the strength. It is known that this method can increase the bending strength, its reliability and the Weibull modulus of the material ("Yogyo Kyokai Shi", vol. 95, sixth issue, page 630, 1987).
But in this method, since the heat treatment is carried out after finishing the material into a final shape, the dimensional accuracy tends to decrease. Also, as pointed out by Kishi et al ("Yogyo Kyokai Shi", vol. sixth issue, page 635, 1987), this method has a problem in that it is difficult to keep down variations, depending upon the size of the damage on the material before heat treatment. Thus, it is difficult to use this method in the actual production.
In order to solve these problems, it is necessary to develop a machining method which provides a sufficiently smooth surface roughness (e.g. Rmax<0.1 micrometer) and by which the surface damage such as cracks can be repaired after grinding or even during grinding.
One method of this type is disclosed by Ichida et al ("Yogyo Kyokai Shi", vol. 94, first issue, page 204, 1986), in which a mirror finish is obtainable by grinding a .beta.-Sialon sintered body with a fine-grained diamond grinding wheel while forming flow type chips. Also, Ito shows that it is possible to form a mirror finish by grinding silicon nitride ceramics with an ordinary alumina grinding wheel ("Latest Fine Ceramics Techniques", published by Kogyo Chosakai, page 219, 1983).
The finished surfaces obtained by these techniques show a maximum height-roughness Rmax of 0.03 micrometer. Considering the fact that the crystal grain diameters of silicon nitride and .beta.-Sialon are both several micrometers, it appears the statements of Ichida and Ito, that is, "removal of material by forming flow type chips chiefly by plastic deformation" and "removal of material mainly by abrasion and microscopic crushing" cannot fully explain the above phenomenon. Further, in the former literature, the work is a pressureless sintered body. It is somewhat inferior in mechanical properties compared with silicon nitride ceramics, which are expected to be widely used for precision machining parts in the future. In this respect, the mechanism of material removal is dependent upon the properties of the material.
It is an object of the present invention to provide an industrially feasible grinding method which can provide a sufficiently smooth finished surface, i.e. a surface having a maximum height-surface roughness Rmax of 0.1 micrometer or less and a ten-point mean roughness Rz of 0.05 micrometer and which can repair any surface damage during grinding.

Facility for grinding silicon nitride ceramic workpiece


Use of 13C glucose in an analytical assay to monitor glucose metabolism by measurement of labeled exhaled CO2 is provided. A breath test and kit for performing the breath test are described for the diagnosis of diabetic indications and monitoring of glycemic control. The breath test utilizes the measurement of expired 13C-labeled CO2 following the ingestion of a 13C-enriched glucose source.

Use of 13C glucose in an analytical assay to monitor glucose metabolism by measurement of labeled exhaled CO2 is provided. A breath test and kit for performing the breath test are described for the diagnosis of diabetic indications and monitoring of glycemic control. The breath test utilizes the measurement of expired 13C-labeled CO2 following the ingestion of a 13C-enriched glucose source.
The following references are referred to by their numbers in parenthesis in this specification.
1. Martin B C, Warram J H, Krolewski A S, et al. Role of glucose and insulin resistance in development of type 2 diabetes mellitus: results of a 25-year follow-up study. Lancet 1992; 340: 925-9.
2. Lillioja S, Mott D M, Spraul M, et al. Insulin resistance and insulin secretory dysfunction as precursors of non-insulin-dependent diabetes mellitus; prospective studies of Pima Indians. N Engl J Med 1993; 329: 1988-92.
3. Beck Nielsen H, Groop L C. Metabolic and genetic characterization of pre-diabetic states. Sequence of events leading to non-insulin-dependent diabetes mellitus. J Clin Invest 1994; 94: 1714-21.
4. Matthaei S, Stumvoll M, Kellerer M, et al. Pathophysiology and pharmacological treatment of insulin resistance. Endocr Rev 2000; 21: 585-618.
5. The Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Report of the expert committee on the diagnosis and classification of diabetes mellitus. Diabetes Care 2001; 24(suppl 1).
6. Harris M I. Undiagnosed NIDDM: clinical and public health issues. Diabetes Care 1993, 16: 642-52.
7. World Health Organization. Prevention of diabetes mellitus; report of a WHO study group. Geneva: WHO, 1994; technical report series No. 844.
8. Meltzer S, Leiter L, Daneman D, et al. 1998 clinical practice guidelines for the management of diabetes in Canada. Can Med Assoc J 1998; 159 (suppl 8): S1-29.
9. Matthews D R, Hosker J P, Rudenski A S, et al. Homeostasis model assessment: insulin resistance and beta-cell function from fasting plasma glucose and insulin concentrations in man. Diabetologia 1985; 28: 412-19.
10. Haffner S M, Gonzales C, Miettinene H, et al. A prospective analysis of the HOMA model: the Mexico City Diabetes Study. Diabetes Care 1996; 19: 1138-41.
11. Bonora E, Targher G, Alberiche M, et al. Homeostasis model assessment closely mirrors the glucose clamp technique in the assessment of insulin sensitivity. Diabetes Care 2000; 23: 57-63.
12. World Health Organization. Definition, diagnosis and classification of diabetes mellitus and its complications: Report of a WHO Consultation. Part 1. Diagnosis and classification of diabetes mellitus. Geneva: WHO, 1999.
13. Ganda O P, Day J L, Soeldner J S, et al. Reproducibility and comparative analysis of repeated intravenous and oral glucose tolerance tests. Diabetes 1978; 27:715-25.
14. Riccardi G, Vaccaro O, Rivellese A, et al. Reproducibility of the new diagnostic criteria for impaired glucose tolerance. Am J Epidemiol 1985; 121: 422-9.
15. Ko G T C, Chan J C N, Woo J, et al. Use of the 1997 American Diabetes Association Diagnostic criteria for diabetes in a Hong Kong Chinese population. Diabetes Care 1998; 21: 2094-7.
16. Ko G T C, Chan J C N, Woo J, et al. The reproducibility and usefulness of the oral glucose tolerance test in screening for diabetes and other cardiovascular risk factors. Ann Clin Biochem 1998; 35: 62-7.
17. Gabir M M, Hanson R L, Diabelea D, et al. The 1997 American Diabetes Association and 1999 World Health Organization criteria for hyperglycemia in the diagnosis and prediction of diabetes Diabetes Care 2000; 23: 1108-12.
18. Radziuk J. Insulin sensitivity and its measurement: structural commonalities among the methods. J Clin Endocrinol Metab 2000; 85: 4426-33.
19. CDC Diabetes Cost-Effectiveness Study Group. The cost-effectiveness of screening for type 2 diabetes. JAMA 1998; 280: 1757-63.
20. Hosker J P, Matthews D R, Rudneski A S, et al. Continuous infusion of glucose with model assessment: measurement of insulin resistance and xcex2-cell function in man. Diabetologia 1985; 28: 401-11.
21. Emoto M, Kawagishi T, Nishizawa Y, et al. Homeostasis model assessment as a clinical index of insulin resistance in type 2 diabetic patients treated with sulfonylureas. Diabetes Care 1999; 22:818-22.
The entire disclosure of each of the above-referenced publications, patents and patent applications is incorporated herein in its entirety.
Glucose tolerance is defined as the ability to properly utilize glucose. Diabetes is not a single disease, but an array of diseases that exhibit the common symptom of glucose intolerance, an impairment in glucose utilization.
The prevalence of diabetes in the general population is approximately 6-7%. Only about half of diabetics are actually diagnosed. Studies have shown that rates for persons with glucose intolerance are equal by sex and greater for blacks than for whites.
In general, the following types of diabetes have been recognized: type I diabetes mellitus, type II diabetes mellitus, secondary diabetes mellitus, impaired glucose tolerance and gestational diabetes mellitus. The general characteristics of the symptoms of diabetes include the following:
Polyuria (excretion of large quantities of urine)
Hyperglycemia (high blood glucose levels)
Glucosuria (abnormal presence of glucose in urine)
Polydipsia (excessive thirst)
Polyphagia (excessive hunger)
Sudden weight loss.
It has been observed that complications resulting from diabetes mellitus are the third leading cause of death in most developed countries. Diabetes is a risk factor for a variety of conditions including coronary heart disease, cerebrovascular stroke, neuropathy (nerve damage), nephropathy (kidney damage), retinopathy (eye damage), hyperlipidemia (excessive blood lipids), angiopathy (damage to blood vessels) and infection.
A number of different methods exist for determining a condition of intolerance for glucose. These include postprandial blood glucose, oral glucose tolerance test (OGTT), O""Sullivan glucose tolerance test (gestational test), hemoglobin Alc (Hb Al, Hb Alc), islet cell antibodies, glutamic acid decarboxylase (GAD) antibodies and insulin antibodies. Diabetes, however, is most readily detected when the carbohydrate metabolic capacity is tested. This is done by stressing the system with a defined glucose load as in the oral glucose tolerance test (OGTT).
The OGTT has been criticized, however, because many of the variables affecting test results are difficult to control. For instance: patients must be on a standardized carbohydrate diet at least three days before the test; the test requires an 8 to 16 hour fast; the test should only be performed on ambulatory patients; stress should be avoided; exercise should be avoided; various hormone imbalances can affect validity such as with: thyroxine, growth hormone, cortisol and catecholamines; various drugs and medications can affect validity such as: oral contraceptives, salicylates, nicotinic acid, diuretics and hypoglycemics; and evaluation should normally be corrected for age. The greatest disadvantage of the OGTT is that it is poorly reproducible and this limits its diagnostic usefulness.
Type 2 diabetes is a common condition, associated with significant morbidity and mortality. It is generally acknowledged that overt type 2 diabetes is preceded by a period of glucose intolerance which itself is preceded by a significant period of insulin resistance (1-5). It is now further recognized that typical diabetic complications can begin to develop during this xe2x80x9cpre-diabeticxe2x80x9d phase (3,6). The identification of persons at risk of developing overt type 2 diabetes has therefore taken on even greater importance. It has been suggested that if such persons could be easily identified, a lifestyle modification strategy could be implemented which might prevent their progression to type 2 diabetes with its attendant morbidities.
Because of the public health importance of type 2 diabetes, regular screening for this condition is now advocated (5,7,8). However, such screening programs, whether by fasting plasma glucose or by the 75-g OGTT, only identify diabetic or glucose-intolerant patients. The homeostasis model assessment (HOMA) index has been advocated as a method of detecting persons with insulin resistance and therefore presumably at risk of progressing to overt type 2 diabetes (9-11). However, the HOMA index requires a serum insulin measurement and, some argue, the use of a computer program. Thus, this index is not as simple or accessible as a fasting blood glucose level. Similarly, the gold standard euglycemic, hyperinsulinemic clamp is clearly not appropriate for mass screening campaigns.
The current methods of diagnosing diabetes involve either invasive testing (i.e., repeated blood collections), or use blood-borne markers (i.e., glycosylated proteins, or antibodies) which offer an indirect assessment of glucose regulation. Accordingly, it is an object of the present invention to avoid the need for invasive testing or the use of blood-borne markers in determinations of glucose regulation.
The above and other objects of the invention are attained by a 13C breath test and a kit for determining glucose regulation in a patient in need thereof.
Based on our experience in the use of 13C breath tests, we propose a simple, sensitive test of insulin resistance. In normal individuals, in the presence of insulin, glucose is taken up by cells where it undergoes glycolysis and then enters the citric acid cycle or is shunted to fat synthesis. In either case, CO2 is produced as a metabolic by-product. This CO2 then re-enters the circulation and is eliminated in the lungs. We found that if glucose was labeled with 13C, the resultant CO2 could be detected in the expired air. In type 2 diabetes and other states of insulin resistance, glucose uptake is impaired and the generation of 13CO2 is likewise blunted. Accordingly, we have developed a 13C-glucose breath test for the diagnosis of type 2 diabetes and insulin resistance. In particular, the test provides a means to detect insulin resistance when blood glucose levels are still in the normal range and before xcex2-cell destruction leading to diabetes has occurred. Early detection of insulin resistance will allow intervention in time to prevent the development of type 2 diabetes. In addition, the test allows the success of intervention therapies, including diet and exercise to be monitored.
An analytical assay is described that is based on the use of non-radioactive 13C. Labeled expired 13CO2 is measured in the present assay. Isotope ratio mass spectroscopy (IRMS) is used as a detection method for 13C, a non-radioactive isotope that occurs naturally in food and animal tissues. Non-dispersive infrared spectroscopy (NDIRS) analysis and analysis methods known in the art may be employed. The test protocol is as follows: after an overnight fast, the oral dose of 13C uniformly labeled glucose (containing about 25 mg of 13C glucose in combination with about 15 g of unlabeled glucose in 100 ml of tap water) is administered. Breath samples will be collected before the dose and then 1xc2xd hours after 13C glucose ingestion. Levels of 13CO2 in expired air will be measured by an IRMS method.
Advantages of this test are the following:
it is practical, sensitive and specific;
the validity of the test is not influenced by stress, exercise, hormone imbalances, or some drugs and medications;
it is a non-invasive method;
it is simple to perform and can be readily used in physicians"" offices or medical laboratories;
it is safe since 13C is a naturally occurring isotope found in all carbon-containing substances;
it involves no radioactivity, and may be used in children and women.
The 13C glucose test is safe, reliable, and specific in diagnosis of diabetes and measurement of the severity of insulin resistance in patients. The invention is also preferred to diagnose gestational diabetes and to monitor glycemic control in diabetes patients. A preferred embodiment of the invention is a kit containing the necessary material for performing the described method. This kit may contain, but is not limited to, a source of 13C enriched glucose (preferably uniformly labeled D-glucose); a source of unenriched glucose; and a breath collection device. The kit may also contain a set of patient instructions for its use. In another embodiment, the kit may additionally contain a blood collection device, such as a lancet or hypodermic needle and vacutainer for the additional determination of blood glucose levels.
Accordingly, in one aspect the invention provides diagnostic kits for the determination of glycemic control in a subject comprising: a predetermined quantity of 13C-enriched glucose; and a breath collection container. A plurality of breath containers and/or instructions for use may be included. The kits may be used for the diagnosis of diabetes, insulin resistance, gestational diabetes, and the like or to determine the adequacy of antihyperglycemic therapy.
In a further aspect, the invention provides a use of 13C-enriched glucose for the determination of glycemic control in a subject.
In another aspect, the invention provides 13C-enriched glucose for use in the manufacture of diagnostic kits for the determination of glycemic control in a subject. The kits may be used for the diagnosis of diabetes, insulin resistance, gestational diabetes, and the like or to determine the adequacy of antihyperglycemic therapy.
In yet a further aspect, the invention provides diagnostic kits for the determination of glycemic control in normal, diabetic and insulin resistant subjects by comparing blood glucose levels with breath levels of 13C-enriched CO2
In a still further aspect, the invention provides method of diagnosing a condition in a subject, said condition selected from the group consisting of diabetes, insulin resistance impaired glucose tolerance, impaired fasting glucose and gestational diabetes, said method comprising collecting a first breath sample from said subject in a first breath collection container; administering 13C-enriched glucose to said subject; collecting a second breath sample from said subject in a second breath container at a time point after administration of said 13C-enriched glucose; measuring the 13CO2 in each of said first and second breath samples; and comparing the amount of 13CO2 in said second breath sample with the amount of 13CO2 in said first breath sample to obtain a delta value, wherein the presence of less 13CO2 in said second breath sample compared to normal control values indicates the presence of said condition. Using an ROC curve, a delta cutoff is chosen wherein the sensitivity and specificity are such as to maximize diagnostic accuracy. In particular, when the condition is insulin resistance, a range of deltas from 8 to 10 is preferred. A delta of 9 is most preferred.
In yet an additional aspect, the invention provides method of predicting a subject""s risk of developing diabetes, said method comprising collecting a first breath sample from said subject in a first breath collection container; administering 13C-enriched glucose to said subject; collecting a second breath sample from said subject in a second breath container, at a time point after administration of said 13C-enriched glucose; measuring the 13CO2 in each of said first and second breath samples; and comparing the amount of 13CO2 in said second breath sample with the amount of 13CO2 in said first breath sample, wherein the presence of less 13CO2 in said second breath sample compared to normal control values indicates risk of developing diabetes. The comparison may be made by choosing a cutoff of ROC values wherein the sensitivity and specificity are such as to maximize diagnostic accuracy. In particular, a range of ROC""s from 8 to 10 is preferred. An ROC of 9 is most preferred.
The 13C-glucose breath test is superior to currently used laboratory criteria in the diagnosis of type 2 diabetes. Its predictive value for clinical status, as well as its correlation with the HOMA index, make it a simple but useful test for detecting early evidence of insulin resistance and hence, risk for type 2 diabetes.

13C glucose breath test for the diagnosis of diabetic indications and monitoring glycemic control


To accommodate computer graphics delays, the future position and orientation of a simulated vehicle are predicted in an operating sequence by separate coordinated models that are fed data signals indicating the operator's control actions. The control actions are extrapolated to provide further data signals. A suspension model and a nonlinear chassis model operate sequentially with a road model to provide one reference-state input to a prediction model. Other inputs to the prediction model are from the drive train and steering extrapolation units controlled by driver inputs.

For a number of years, a need has been recognized for vehicle simulators that can be operated by a driver manipulating conventional controls to be shown the results of his action as by a simulated display. For example in training activities, simulators are widely used with respect to airplanes, helicopters and ground vehicles. In addition to training uses, vehicle simulators have been found useful in test and design work.
In the current state of technology, a visual display is considered a necessary component of a vehicle simulator. Accordingly, as the pilot or driver of a simulated vehicle manipulates the controls, he is provided with a responsive display showing the driver's view as the vehicle simulates movement in a programmed environment. Contemporary simulators utilize computer graphics techniques to provide a dynamic display. An environment is programmed and positional signals are developed to indicate the position and orientation of the vehicle in the environment. Representative simulator data is then supplied to a computer graphics system to attain a dynamic display.
Typically, the operation of the computer graphics system to provide image display signals from simulator data involves a relatively large time delay that often presents a problem. Consider an example. A high performance automobile may respond to the controls with a delay of only thirty milliseconds (30 ms). Simulator models for such an automobile are capable of approaching such response times in providing simulator electrical signals to indicate the position and orientation of the car. However, the utilization of such simulator signals by a computer graphics system (image generator) to provide signals for a visual display is likely to take much longer, e.g. sixty milliseconds (60 ms). Thus, accepting the inherent delay of the qraphics system introduces a response delay that is intolerable for many simulator applications.
Techniques have been used in previous vehicle simulators to compensate for the delay of the graphics system or image generator. Generally, the compensation has involved extrapolating from the current motion of the vehicle to predict future positional data for the display. Specifically, polynomial extrapolation, as well as feedback techniques and moving average techniques have been proposed for compensating time delays in prior systems. However, such arrangements tend to be inaccurate and typically impose the limitation that linear dynamics models be employed in the system. Because vehicle dynamics are not linear, in some instances a severe constraint is imposed on model fidelity if operation is restricted to motion extrapolation or linear prediction. Accordingly, a need exists for an improved vehicle simulation system that is relatively economical, enables the use of non-linearity in models and enables realistic time approximation of the motion characteristics of an actual vehicle.
In general, the system of the present invention incorporates simultaneous separate, but coordinated, dynamics models, each performing a specialized function in real time. In accordance with the invention, nonlinearity can be built into the models as needed. At least one simulation model simulates the complete vehicle movement to provide reference positional signals indicative of current position and orientation. As disclosed, the prediction model in the system utilizes the positional reference signals from the simulation model along with extrapolation representations (solely from control actions) to predict the positional state of the vehicle at a time approximating the time of display. In the disclosed embodiment, model fidelity is insured by periodically updating predictions with initial reference conditions provided from a full chassis simulation model. Also, in the disclosed embodiment, the simulation model involves two separate units, one in the form of a nonlinear suspension unit with relatively large bandwidth for full road and handling inputs. The other unit is the nonlinear full vehicle dynamics model with some or all of the nonlinear effects simulated.


A circuit interrupter uses a dielectric liquid such as sulphur hexachloride to extinguish arcs in an interrupter. The liquid is injected at a relatively high pressure by a pump piston with a relatively high mass and an accumulator acts as a pressure fly wheel to effectively reduce high pressure maximums and increase low pressure minimums because of the much lower mass of the accumulator piston. In addition, a double fluid flow interrupter is provided.

The present invention is directed to a circuit interrupter using dielectric liquid with energy storage.
Liquified gas circuit interrupters are well-known one being disclosed in U.S. Pat. No. 3,150,245 to W. M. Leeds et al. as inventors. Leeds discloses a fluid such as sulphur hexafluoride and provides driving means for forcing the liquified gas at high pressure toward the arc zone when the contacts of the interrupter are parted. One of the problems pointed out in Leeds is maintaining a high enough pressure especially during the low temperature ambient operation for effective arc extinguishing. In order to maintain an adequate injection pressure, Leeds proposes three techniques which are (1) the use of a mechanically operated impulse device, (2) the use of an accumulator with gas such as nitrogen in one end and sulphur hexachloride in the other, and (3) the use of sulphur hexachloride and a heater to maintain a high enough temperature.
A problem with the Leeds design is the remarkable rise in the fault current interrupting requirements in the past decade. For example, Leeds is directed to interrupting perhaps 50,000 amperes with pressures which are generally less than 1,000 psi. In contrast with a current of for example 120,000 amperes, as much as 2,000 psi may be required. With the required high pressure two problems are presented. One is that when an arc is formed upon separation of the contacts the arc in essence shuts off the flow of interrupting fluid and causes an incipient high pressure maximum. This pressure may be much higher in fact than the required arc extinguishing pressure and subjects the entire interrupter device to severe mechanical stress. On the other hand, when the arc is near current zero, the arc diameter reduces thus allowing the liquid to flow out the orifices more rapidly. This tends to reduce the pressure below an acceptable level in which an arc might be re-established. In other words, a low pressure minimum may be produced by rapidly increasing flow area while the pump has a slow response to these changing conditions.
Fischer U.S. Pat. No. 3,406,269 discloses in FIGS. 5 and 6 techniques (including an accumulator) for maintaining sufficient pressures. However, since the systems are closed there is no pressure minimum problem.

Circuit interrupter using dielectric liquid with energy storage


The present invention relates to a synthetic method comprising contacting at least one diaryl carbonate with one or more dihydroxy aromatic compounds in the presence of a transesterification catalyst under melt polymerization conditions to afford a product polycarbonate. The transesterifcation catalysts used according to the method of the present invention are alkali metal salts and alkaline earth metal salts of organic polyacids in combination with tetraalkyl ammonium or tetraalkyl phosphonium compounds which serve as co-catalysts. The transesterification catalysts are derived from polyacids containing both CO2H groups and SO3H groups and from polyacids containing exclusively CO2H groups or exclusively SO3H groups. The catalysts employed according to the method of the present invention provide polycarbonates having reduced levels of Fries rearrangement product relative to conventionally employed catalysts such as sodium hydroxide.

This invention relates to salts of organic polyacids useful as transesterification catalysts in melt polymerization reactions of dihydroxy aromatic compounds with diaryl carbonates. Suitable salts of organic polyacids include alkali and alkaline earth metal salts of polycarboxylic acids; alkali and alkaline earth metal salts of polysulfonic acids; and salts of polyacids incorporating both carboxylate and sulfonate groups. The invention further relates to a method for the preparation of polycarbonates using the alkali and alkaline earth metal salts of these organic polyacids. The method provides a product polycarbonate comprising a lower level of Fries product than is provided by other known methods employing conventional melt transesterification catalysts.
Increasingly, polycarbonate is being prepared by the melt reaction of a diaryl carbonate with a dihydroxy aromatic compound in the presence of a transesterification catalyst, such as sodium hydroxide. In this xe2x80x9cmeltxe2x80x9d process, reactants are introduced into a reactor capable of stirring a viscous polycarbonate melt at temperatures in excess of 300xc2x0 C. Typically, the reaction is run at reduced pressure to facilitate the removal of by-product hydroxy aromatic compound formed as the diaryl carbonate reacts with the dihydroxy aromatic compound and growing polymer chains.
The Fries rearrangement is a ubiquitous side reaction taking place during the preparation of polycarbonate using the melt process. The resultant xe2x80x9cFries productxe2x80x9d serves as a site for branching of the polycarbonate chains thereby affecting flow and other properties of the polycarbonate. Although, a low level of Fries product may be tolerated in the product polycarbonate produced by the melt process, the presence of higher levels of Fries product may negatively impact performance characteristics of the polycarbonate, such as moldability and toughness. Currently, alkali metal hydroxides, such as sodium hydroxide, are employed as catalysts in the preparation of polycarbonate using the melt process. Alkali metal hydroxides, although effective catalysts in terms of rates of conversion of starting materials to product polycarbonate, tend to produce relatively high levels of Fries rearrangement product. Thus, melt polymerization methodology useful for the preparation of polycarbonate in which the formation of Fries product has been minimized represents a long sought goal among those wishing to practice such methodology.
It would be a significant advantage to prepare polycarbonate by a melt polymerization method which provides high rates of polymerization while minimizing the amount of Fries product formation.
The present invention provides a method for the preparation of polycarbonate said method comprising contacting at least one diaryl carbonate with at least one dihydroxy aromatic compound in the presence of a transesterification catalyst comprising at least one alkali metal or alkaline earth metal salt of an organic polyacid and optionally a co-catalyst, under melt polymerization conditions to afford a product polycarbonate.
In one aspect the method of the present invention affords a product polycarbonate having a lower level of Fries rearrangement product than polycarbonate prepared using a conventional melt transesterification catalyst.
The present invention further relates to a method of preparing polycarbonate by the melt reaction of at least one dihydroxy aromatic compound with at least one diaryl carbonate in the presence of at least one transesterification catalyst having structure I
(xe2x88x92O3S)nxe2x80x94R1xe2x80x94(CO2xe2x88x92)m (M)pxe2x80x83xe2x80x83I
wherein R1 is an aliphatic radical, a cycloaliphatic radical, or an aromatic radical, n and m are an integers between 0 and about 10 wherein the sum of n plus m is at least 2, M is independently at each occurrence an alkali metal cation, or an alkaline earth metal cation , and p is an integer between 1 and about 20.
The present invention may be understood more readily by reference to the following detailed description of preferred embodiments of the invention and the examples included therein. In the following specification and the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings:
The singular forms xe2x80x9caxe2x80x9d, xe2x80x9canxe2x80x9d and xe2x80x9cthexe2x80x9d include plural referents unless the context clearly dictates otherwise.
xe2x80x9cOptionalxe2x80x9d or xe2x80x9coptionallyxe2x80x9d means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
As used herein the term xe2x80x9cpolycarbonatexe2x80x9d refers to polycarbonates incorporating structural units derived from at least one dihydroxy aromatic compounds and includes copolycarbonates and polyester carbonates.
As used herein, the term xe2x80x9cmelt polycarbonatexe2x80x9d refers to a polycarbonate made by a process comprising the transesterification of a diaryl carbonate with a dihydroxy aromatic compound in the presence of a transesterification catalyst.
xe2x80x9cBPAxe2x80x9d is herein defined as bisphenol A or 2,2-bis(4-hydroxyphenyl)propane.
xe2x80x9cCatalyst systemxe2x80x9d as used herein refers to the catalyst or catalysts that catalyze the transesterification of the dihydroxy aromatic compound with the diaryl carbonate in the preparation of melt polycarbonate.
xe2x80x9cCatalytically effective amountxe2x80x9d refers to the amount of the catalyst at which catalytic performance is exhibited.
As used herein the term xe2x80x9cFries productxe2x80x9d is defined as a structural unit of the product polycarbonate which upon hydrolysis of the product polycarbonate affords a carboxy-substituted dihydroxy aromatic compound bearing a carboxy group adjacent to one or both of the hydroxy groups of said carboxy-substituted dihydroxy aromatic compound. For example, in bisphenol A polycarbonate prepared by a melt reaction method in which Fries reaction occurs, the Fries product affords carboxy bisphenol A, II, upon complete hydrolysis of the product polycarbonate.
The terms xe2x80x9cFries productxe2x80x9d and xe2x80x9cFries groupxe2x80x9d are used interchangeably herein.
The terms xe2x80x9cFries reactionxe2x80x9d and xe2x80x9cFries rearrangementxe2x80x9d are used interchangeably herein.
As used herein the term xe2x80x9chydroxy aromatic compoundxe2x80x9d means a phenol, such as phenol, p-cresol or methyl salicylate, comprising a single reactive hydroxy group and is used interchangeably with the term xe2x80x9cphenolic by-productxe2x80x9d.
As used herein the term xe2x80x9caliphatic radicalxe2x80x9d refers to a radical having a valence of at least two comprising a linear or branched array of carbon atoms which is not cyclic. Examples of aliphatic radicals include methylene; ethylene; 1,2-dimethylethylene; hexamethylene; and the like.
As used herein the term xe2x80x9caromatic radicalxe2x80x9d refers to a radical having a valence of at least two, said radical comprising at least one aromatic group. The aromatic radical may be composed entirely of carbon and hydrogen atoms, or may comprise heteroatoms such as nitrogen, oxygen and sulfur. Aromatic radicals include the divalent radicals III, IV and V below wherein the dashed lines indicate the points
of attachment of CO2xe2x88x92 and SO3xe2x88x92 groups.
The following are excluded from the definition of the term xe2x80x9caromatic radicalxe2x80x9d as used herein: derivatives of phenanthroline, for example the structure VI, and derivatives of 2,2xe2x80x2-isoquinoline, for example structure VII. Also excluded from
the definition of the term xe2x80x9caromatic radical as used herein are radicals comprising porphine heterocycles, for example as in 5, 10, 15, 20-tetraphenyl-21H, 23H-porphine. Also excluded from the definition of the term xe2x80x9caromatic radical as used herein are radicals comprising phthalocyanine heterocycles, for example as in 2, 9, 16, 23-tetraphenoxy-29H, 31H-phthalocyanine. Also excluded from the definition of the term xe2x80x9caromatic radicalxe2x80x9d as used herein, are radicals comprised exclusively of triazinyl
and pyridyl groups, triazinyl and phenyl groups, and triazinyl together with pyridyl and phenyl groups, for example as in structure VIII. In specifying that certain radicals comprising triazinyl groups are excluded from the definition of the term xe2x80x9caromatic radicalxe2x80x9d as used herein, it is understood that both unsubstituted derivatives and substituted derivatives comprising triazines are intended to be excluded. By xe2x80x9csubstitutedxe2x80x9d it is meant that the radical comprising the triazinyl group bears a substituent commonly understood to be a halogen atom, a C1-C20 alkyl group and the like. By xe2x80x9ccomprised exclusively of triazinyl and pyridyl groups, triazinyl and phenyl groups, and triazinyl together with pyridyl and phenyl groupsxe2x80x9d it is meant that no aromatic ring structures other than a substituted or unsubstituted triazinyl, phenyl or pyridyl group is present.
As used herein the term xe2x80x9ccycloaliphatic radicalxe2x80x9d refers to a radical having a valance of at least two comprising an array of atoms which is cyclic but which is not aromatic. The array may include heteroatoms such as nitrogen, sulfur and oxygen or may be composed exclusively of carbon and hydrogen. Cycloaliphatic radicals include the divalent radicals IX, X and XI below wherein the dashed lines indicate the points of attachment of CO2xe2x88x92 and SO3xe2x88x92 groups.
It should be understood that as used herein, the terms xe2x80x9caliphatic radicalxe2x80x9d, xe2x80x9caromatic radicalxe2x80x9d and xe2x80x9ccycloaliphatic radicalxe2x80x9d include both substituted and unsubstituted embodiments of said radicals. For example, a radical comprising the cyclohexane ring structure IX may be regarded as an unsubstituted cycloaliphatic radical and an analogous six membered ring structure comprising a methyl group (CH3) may be taken as an example of a substituted cycloaliphatic radical. Typical substituents according to the present invention for the substituted forms of aliphatic, aromatic, and cycloaliphatic radicals, include C1-C20 alkyl, C3-C20 cycloalkyl, C4-C20 aryl, halogen, hydroxy, carbonyl, nitro, cyano, C1-C20 alkoxy, C1-C20 alkoxycarbonyl, and the like.
It should be understood that the terms xe2x80x9cmmHgxe2x80x9d and xe2x80x9ctorrxe2x80x9d are used interchangeably herein as units of pressure.
As used herein the term xe2x80x9csodium tosylatexe2x80x9d refers to the sodium salt of toluenesulfonic acid.
It has been discovered that the use of salts of organic polyacids as polymerization catalysts in the melt transesterification reaction of a dihydroxy aromatic compound such as bisphenol A with a diaryl carbonate such as diphenyl carbonate, provides a product polycarbonate comprising a reduced level of Fries rearrangement product. This reduction in the amount of Fries rearrangement is highly desirable in that it results in increased ductility of the product polycarbonate and avoids uncontrolled branching which may occur at sites of Fries rearrangement. Uncontrolled branching may limit the utility of the product polycarbonate by reducing the ductility of the product polycarbonate. Salts of organic polyacids employed as transesterification catalysts according to the method of the present invention produced less Fries rearrangement product than did alkali metal hydroxide transesterification catalysts, such as sodium hydroxide.
In one embodiment, the present invention provides a catalyst system for the production of polycarbonate under melt polymerization conditions, wherein the polycarbonate has a number average molecular weight, Mn of at least about 8000 daltons and a reduced content of Fries products relative to a polycarbonate of comparable molecular weight prepared using an alkali metal hydroxide transesterification catalyst. In particular, it is desirable to have Fries product of less than 3000 ppm, preferably less than 2000 ppm, more preferably less than 1000 ppm, even more preferably less than 500 ppm.
The present invention relates to salts of organic polyacids useful as catalysts under melt polymerization conditions comprising contacting at least one dihydroxy aromatic compound and at least one diaryl carbonate. Dihydroxy aromatic compounds which are useful in preparing polycarbonates according to the method of the present invention may be represented by the general formula XII
wherein R2 is independently at each occurrence a halogen atom, nitro group, cyano group, C1-C20 alkyl group, C4-C20 cycloalkyl group, or C6-C20 aryl group; q and s are independently integers 0-3; and W is a bond, an oxygen atom, a sulfur atom, a SO2 group, a C1-C20 aliphatic radical, a C6-C20 aromatic radical, a C6-C20 cycloaliphatic radical or the group
wherein R3 and R4 are independently a hydrogen atom, C1-C20 alkyl group, C4-C20 cycloalkyl group, or C4-C20 aryl group; or R3 and R4 together form a C4-C20 cycloaliphatic ring which is optionally substituted by one or more C1-C20 alkyl, C6-C20 aryl, C5-C21, aralkyl, C5-C20 cycloalkyl groups or a combination thereof.
Suitable bisphenols XII according to the method of the present invention include bisphenol A; 2,2-bis(4-hydroxy-3-methylphenyl)propane; 2,2-bis(3-chloro-4-hydroxyphenyl)propane; 2,2-bis(3-bromo-4-hydroxyphenyl)propane; 2,2-bis(4-hydroxy-3-isopropylphenyl)propane; 1,1-bis(4-hydroxyphenyl)cyclohexane; 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane; and 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane.
In one aspect of the present invention, the diaryl carbonate used according to the method of the present invention has structure XIII
wherein R5 is independently at each occurrence a halogen atom, nitro group, cyano group, C1-C20 alkyl group, C1-C20 alkoxy carbonyl group, C4-C20 cycloalkyl group, or C6-C20 aryl group; and t and v are independently integers 0-5.
Diaryl carbonates XIII suitable for use according to the method of the present invention are illustrated by diphenyl carbonate, bis(4-methylphenyl) carbonate, bis(4-chlorophenyl) carbonate, bis(4-fluorophenyl) carbonate, bis(2-chlorophenyl) carbonate, bis(2,4-difluorophenyl) carbonate, bis(4-nitrophenyl) carbonate, bis(2-nitrophenyl) carbonate, and bis(methyl salicyl) carbonate (CAS No. 82091-12-1).
In one embodiment, structural units of the product polycarbonate derived from the dihydroxy aromatic compound are comprised entirely of structural units derived from bisphenol A, and structural units derived from the diaryl carbonate are derived entirely from diphenyl carbonate.
Optionally, one or more branching agents may be included during the melt polymerization reaction according to the method of the present invention as a means of effecting the controlled branching of the product polycarbonate as is sometimes desirable in applications, such as in blow molding of beverage bottles, requiring a high degree level of melt strength. Suitable branching agents include 1,1,1-tris(4-hydroxyphenyl)ethane (THPE) and 1,3,5-trihydroxybenzene.
In the process of the present invention, an endcapping agent may optionally be used. Suitable endcapping agents include hydroxy aromatic compounds such as phenol, p-tert-butylphenol, p-cumylphenol, cardanol and the like.
When an endcapping agent is employed said endcapping agent is preferably used in an amount corresponding to between about 0.001 and about 0.10 moles, preferably about 0.01 to about 0.08 moles per mole of the dihydroxy aromatic compound employed.
The catalyst system according to the present invention comprises at least one salt of an organic polyacid having structure I
xe2x80x83(xe2x88x92O3S)nxe2x80x94R1xe2x80x94(CO2xe2x88x92)m (M)pxe2x80x83xe2x80x83I
wherein R1 is an aliphatic radical, a cycloaliphatic radical, or an aromatic radical, n and m are an integers between 0 and about 10 wherein the sum of n plus m is at least 2, M is independently at each occurrence an alkali metal cation, or an alkaline earth metal cation , and p is an integer in a range from 1 to about 20.
The catalyst having structure I may comprise both CO2xe2x88x92 groups and SO3xe2x88x92 groups, as is the case when both n and m are 1 or more. Thus, in one embodiment of the present invention, the catalyst comprises a salt of an organic polyacid having structure I wherein R1 is an aliphatic radical, a cycloaliphatic radical, or an aromatic radical, n and m are an integers in a range from 1 to about 10, wherein the sum of n plus m is at least 2, M is independently at each occurrence an alkali metal cation, or an alkaline earth metal cation, and p is an integer in a range from 1 to about 20. Alternatively, the catalyst having structure I may comprise exclusively CO2xe2x88x92 groups or exclusively SO3xe2x88x92 groups.
As has been noted with respect to structure I, M is independently at each occurrence an alkali metal cation, or an alkaline earth metal cation, and p is an integer in a range from 1 to about 20. In structure I, it is understood that the positive charge associated with the alkali metal cations, or alkaline earth metal cations, or a mixture thereof, represented by letter M, is sufficient to balance the negative charges of the CO2xe2x88x92 groups and SO3xe2x88x92 groups present.
In one embodiment of the present invention the catalyst comprising structure I is the alkali metal salt of an organic polyacid, for example, the disodium salt of the organic polyacid carboxy methanesulfonic acid, said disodium salt having structure XIV.
xe2x88x92O3Sxe2x80x94CH2xe2x80x94CO2xe2x88x92(Na+)2xe2x80x83xe2x80x83XIV
Other salts of polyacids suitable for use as transesterification catalysts according to the method of the present invention are illustrated by the following salts of organic acids and mixtures thereof; disodium terephthalate, oxalomalic acid trisodium salt (structure XV),
di-isocitric acid trisodium salt, 4-sulfophthalic acid trisodium salt (structure XVI)
and 3-(2-pyridyl)-5,6-bis(2-[5-furanyl-2-sulfonic acid])-1, 2, 4-triazine trisodium salt (structure XVII).
In one embodiment of the present invention the group R1 of transesterification catalyst having structure I is an aromatic radical comprising structure XVIII
xe2x80x94xe2x80x94xe2x80x94xe2x80x94xe2x80x94(A1)rxe2x80x94Zxe2x80x94(Ar2)sxe2x80x83xe2x80x83XVIII
wherein Ar1 and Ar2 are independently at each occurrence a C4-C20 aromatic radical, r is an integer from 2 to 3, s is an integer from 0 to 1, and Z is a phosphorous or nitrogen atom. In structure XVIII the dashed lines dashed lines indicate the points of attachment of CO2xe2x88x92 and SO3xe2x88x92 groups.
Suitable examples of transesterification catalysts comprising structure XVIII include 4,4xe2x80x2(phenylphosphinidene)bis(benzenesulfonic acid) dipotassium salt (structure XIX); and 3, 3xe2x80x2, 3xe2x80x3-phosphinidenetris(benzenesulfonic acid) trisodium salt (structure XX).
The catalyst having structure I is employed in an amount corresponding to between about 1xc3x9710xe2x88x928 and 2.5xc3x9710xe2x88x924, preferably between about 1xc3x9710xe2x88x927 and 2.5xc3x9710xe2x88x925 moles of catalyst per mole of dihydroxy aromatic compound employed. When the amount of catalyst employed is less than 1xc3x9710xe2x88x928 mole of catalyst per mole of dihydroxy aromatic compound employed, reaction rates may be reduced to such an extent that no appreciable molecular weight gain is observed. Generally, it is preferred that the number average molecular weight (Mn) of the product polycarbonate be at least about 8000 daltons. When the amount of catalyst is in excess of about 2.5xc3x9710xe2x88x924 moles per mole of dihydroxy aromatic compound employed, rates of Fries rearrangement may be excessive and high levels of uncontrolled branching may occur.
The catalyst comprising at least one salt of an organic polyacid having structure I may be added in a variety of forms according to the method of the present invention. The catalyst may be added as a solid, for example a powder, or it may be dissolved in a solvent, for example water or alcohol. In one embodiment, the catalyst is added to the reaction system in the form of an aqueous solution. The pH of the aqueous solution is preferably at or near the pH of a freshly prepared solution, which varies depending on the salt of the organic polyacid which is used as the catalyst. Further, the salt of the organic polyacid may be formed prior to the introduction of the catalyst into a polymerization system, or the salt may be formed by reaction of the organic polyacid with the appropriate basic compound, for example sodium hydroxide, in the polymerization system.
If the catalyst is not soluble in water or only sparingly soluble in water, the catalyst may be dissolved in a solution comprising a quaternary ammonium compound, a quaternary phosphonium compound, or a mixture thereof, and the solution comprising the catalyst and said onium compound may be used.
The use of a quaternary ammonium compound, a quaternary phosphonium compound, or a mixture thereof, as a co-catalyst is not limited to instances in which the catalyst has low solubility and is introduced into the reaction mixture as an aqueous solution. Quaternary ammonium compounds, quaternary phosphonium compounds, and mixtures thereof, may be employed as co-catalysts and may be introduced into the reaction mixture in a variety of forms; as solids, in solution, or as a melt. Examples of suitable quaternary ammonium compounds include, but are not limited to ammonium hydroxides having alkyl groups, aryl groups and alkaryl groups, such as tetraamethylammonium hydroxide (TMAH) and tetrabutylammonium hydroxide (TBAH). Suitable phosphonium compounds include, but are not limited to tetraethylphosphonium hydroxide, tetrabutylphosphonium hydroxide, and tetrabutylphosphonium acetate.
If present, the quaternary ammonium compound, the quaternary phosphonium compound, or a mixture thereof, is preferably used in amounts of from about 1xc3x9710xe2x88x922 to about 1xc3x9710xe2x88x926, preferably about 1xc3x9710xe2x88x922 to about 1xc3x9710xe2x88x925 moles per mole of dihydroxy aromatic compound. The quaternary onium compounds are used to enhance or modify the activity of the salt of the organic polyacid employed as the primary catalyst.
In some instances the reaction mixture may further comprise a metal hydroxide, for example, an alkali metal hydroxide such as sodium hydroxide. The free metal hydroxide may be added to enhance the activity of the salt of the organic polyacid employed as the primary catalyst, or may be present as a contaminant present in the primary catalyst itself. If present, the free metal hydroxide is preferably present in an amount in an amount corresponding to between about 1xc3x9710xe2x88x928 and 2.5xc3x9710xe2x88x924 moles of catalyst per mole of dihydroxy aromatic compound employed.
The reaction conditions of the melt polymerization are not particularly limited and may be conducted in a wide range of operating conditions. Hence, the term xe2x80x9cmelt polymerization conditionsxe2x80x9d will be understood to mean those conditions necessary to effect reaction between the diaryl carbonate and the dihydroxy aromatic compound of the present invention. The reaction temperature is typically in the range of about 100 to about 350xc2x0 C., more preferably about 180 to about 310xc2x0 C. The pressure may be at atmospheric pressure, supraatmospheric pressure, or a range of pressures from atmospheric pressure to about 15 torr in the initial stages of the reaction, and at a reduced pressure at later stages, for example in the range of about 0.2 to about 15 torr. The reaction time is generally about 0.1 hours to about 10 hours.
The melt polymerization may be accomplished in one or more stages, as is known in the art with other catalysts. The catalyst and co-catalysts of the present invention may be added in the same stage or different stages, if the melt polymerization is conducted in more than one stage. The optional co-catalyst may be added at any stage, although it is preferred that it be added early in the process. When utilized, the co-catalyst is preferably utilized in an amount corresponding to between about 1 and about 500 molar equivalents, based on the moles of catalyst I utilized.
In a further preferred embodiment, the process is conducted as a two stage process. In the first stage of this embodiment, the optional co-catalyst of the present invention is introduced into the reaction system comprising the dihydroxy aromatic compound and the diaryl carbonate. The first stage is conducted at a temperature of 270xc2x0 C. or lower, preferably 80 to 250xc2x0 C., more preferably 100 to 230xc2x0 C. The duration of the first stage is preferably 0 to 5 hours, even more preferably 0 to 3 hours at a pressure from about atmospheric pressure to about 100 torr, with a nitrogen atmosphere preferred.
In a second stage, the catalyst having structure I is introduced into the product from the first stage and further polycondensation is conducted. The catalyst may be added in its entire amount in the second stage, or it may be added in batches in the second and subsequent stages so that the total amount is within the aforementioned ranges.
It is preferable in the second and subsequent stages of the polycondensation step for the reaction temperature to be raised while the reaction system is reduced in pressure compared to the first stage, thus bringing about a reaction between the dihydroxy aromatic compound and the diaryl carbonate. Thus there is formed initially a polycarbonate oligomer which upon further polycondensation reaction at 240 to 320xc2x0 C. under reduced pressure of 5 mm Hg or less, and preferably 1 mm Hg or less, affords polycarbonate having a number average molecular weight of about 8000 daltons or greater.
If the melt polymerization is conducted in more than one stage, as noted above, it is preferable to add a co-catalyst, such as tetramethylammonium hydroxide, tetrabutylammonium hydroxide, tetrabutylphosphonium hydroxide, or tetrabutylphosphonium acetate, in an earlier stage than the catalyst of the present invention. In particular, it is preferable to add the co-catalyst to the reactor before the temperature reaches 220xc2x0 C., preferably before it reaches 200xc2x0 C.
The reaction can be conducted as a batch or a continuous process. Any desired apparatus can be used for the reaction. The material and the structure of the reactor used in the present invention is not particularly limited as long as the reactor has an ordinary capability of stirring and is equipped for the removal of by-product hydroxy aromatic compound formed during the course of the polymerization. It is preferable that the reactor is capable of stirring in high viscosity conditions as the viscosity of the reaction system is increased in later stages of the reaction.
Thus, in a further embodiment, the present invention provides a method for preparing polycarbonates, which comprises the steps of
(a) heating a dihydroxy aromatic compound and a diaryl carbonate for a time period sufficient to form a melt, and thereafter introducing a catalyst composition comprising a catalytically effective amount of a compound having structure I and optionally a co-catalyst selected from tetraalkylammonium and tetraalkylphosphonium compounds;
(b) oligomerizing the melt mixture formed in step (a) in a reaction system comprising at least one continuous reactor in series, wherein said reactor is operated at a temperature of about 210xc2x0 C. to about 290xc2x0 C., and wherein the product from the reactor has a number average molecular weight of about 1000 to about 5500 daltons; and
(c) polymerizing the product from step (b) in a reaction system comprising at least one continuous polymerization reactor in series, wherein said reactor is operated at a temperature of about 280xc2x0 C. to 315xc2x0 C., wherein the product from step (c) has a number average molecular weight of at least about 8000 daltons.
Additives may also be added to the polycarbonate product as long as they do not adversely affect the properties of the product. These additives include a wide range of substances that are conventionally added to the polycarbonates for a variety of purposes. Specific examples include heat stabilizers, epoxy compounds, ultraviolet absorbers, mold release agents, colorants, antistatic agents, slipping agents, anti-blocking agents, lubricants, antifogging agents, natural oils, synthetic oils, waxes, organic fillers, flame retardants, inorganic fillers and any other commonly known class of additives.
The polycarbonate obtained in accordance with the present invention may be used after being mixed with conventional additives, such as plasticizers, pigments, lubricants, mold release agents, stabilizers and organic fillers. It is also possible to blend the polycarbonate with other polymers, including but not limited to, olefins polymers such as ABS and polystyrenes, polyesters, polyacrylates, polyethersulfones, polyamides, and polyphenylene ethers.

Salts of organic polyacids as polymerization catalysts


Curculin C of the present invention has an intrachain disulfide linkage formed between the 29th cysteine residue and the 52nd cysteine residue and interchain disulfide linkages formed between the 77th cysteine residues of two curculin C monomer chains and between the 109th cysteine residues of two curculin C monomer chains, thus giving a dimer, and the monomer has an amino acid sequence as specified in SEQ ID No: 1.

1. Field of the Invention
This invention relates to curculin C (one of curculin homologue) having a stable and potent taste-modification effect, which is obtained from Curculigo latifolia.
2. Description of the Prior Art
The present inventors formerly found out a substance serving as a taste-modifier, which was named "curculin (curculin homologue, hereinafter referred to as curculin)" by them, from Curculigo latifolia fruits growing in Western Malaysia and the southern part of Thailand and belonging to the genus Curculigo of the family Hypoxidaceae or Amaryllidaceae. Further, they found out that this curculin was a protein and that a sour material or water taken after eating it would taste sweet, and applied for a patent based on these findings (refer to Japanese- Patent Laid-Open No. 104263/1990.) Subsequently, they succeeded in highly purifying this protein curculin (one of curculin homologue, hereinafter referred to as curculin A) and applied for a patent on a taste-modifier having the amino acid sequence thereof (refer to Japanese Patent Laid-Open No. 190899/1991).
In spite of the accomplishment of these inventions, however, it has been desired to develop a substance having a more stable and potent taste-modification activity.


In an exhaust purification apparatus of an internal combustion engine having an NOx absorption and release material in an exhaust conduit, a heater is provided close to the NOx absorption and release material. When an NOx absorption operation continues for a predetermined period, the heater is switched on to raise the temperature of the NOx absorption and release material above a predetermined temperature, for example, 500.degree. C. When the temperature of the NOx absorption and release material is high, the NOx absorption and release material releases absorbed NOx and is regenerated.

1. Field of the Invention
The present invention relates to a nitrogen oxides (NOx) decreasing apparatus for an internal combustion engine. More particularly, the present invention relates to an apparatus for effectively purifying NOx included in exhaust gas from a lean burn engine, using a combination of an NOx absorption and release material and an NOx purification catalyst.
2. Description of the Prior Art
To improve fuel economy and to suppress exhaust of carbon dioxide (CO.sub.2) to thereby reduce global warming, engines capable of fuel combustion at lean air-fuel ratios (lean burn engines which include lean burn gasoline engines and diesel engines) are being developed and are partially in actual use. Since a conventional catalyst (three-way catalyst) cannot reduce and purify NOx at lean air-fuel ratios, there is a need to develop a catalyst or system that can purify NOx even at lean air-fuel ratios, that is, under oxidizing gas conditions (excess-oxygen conditions).
As an apparatus capable of purifying NOx under oxidizing gas conditions, the present applicant filed Japanese Patent Application HEI 3-289046 an Oct. 4, 1991, in which an NOx absorption and release material capable of absorbing NOx at lean air-fuel ratios and releasing the absorbed NOx at rich air-fuel ratios is installed in an exhaust conduit of a lean burn engine. The air-fuel ratio of the engine is momentarily changed to a rich air-fuel ratio before the NOx absorption and release material is saturated so that the NOx absorption and release material is regenerated.
However, NOx release operation of the NOx absorption and release material is affected not only by the amount of excess oxygen in the exhaust gas but also by exhaust gas temperature. Therefore, the NOx absorption and release material may release the absorbed NOx at some temperatures even under oxidizing gas conditions. On the other hand, the NOx absorption and release material may release little NOx at other temperatures even at rich air-fuel ratios, and therefore, the NOx release time period may have to be prolonged or the frequency of NOx release may have to be increased, which will be accompanied by degradation of driveability. Further, if it is intended to maintain the NOx absorption and release material at appropriate temperatures from the viewpoint of NOx absorption and release, location of the NOx absorption and release material will be limited and freedom of design will be restricted.

NOx decreasing apparatus for an internal combustion engine


A corrosion-resistant austenitic alloy suitable for use in heat transfer tubes for heat-recovery boilers which withstands uniform corrosion, intergranular corrosion, and stress corrosion cracking in refuse-fired boilers and black-liquor combustion boilers. The alloy consists essentially, on a weight basis, of C: not more than 0.05%, Si: not more than 4%, Mn: not more than 7.5%, Ni: 25-55%, Cr: more than 20% and not more than 35%, Mo: an amount satisfying the following inequality (1) when Mn(%).ltoreq.2.5 or inequality (2) when 2.5.ltoreq.Mn(%).ltoreq.7.5, EQU Mo(%).ltoreq.5.8--[Ni(%)/10] (1) EQU Mo(%).ltoreq.7.5--[Ni(%)/10] (2). optionally one or more of Nb, Ti, Zr, and V: 0.1-3% in total, one or more of Cu, Co, and W: 0.1-5% in total, N: 0.1-0.3%, Al: not more than 0.5%, and at least one rare earth metal: 0.01-0.1% in total, and the balance of Fe and incidental impurities in which the content of P is not more than 0.030% and that of S is not more than 0.010%.

This invention relates to a corrosion-resistant alloy for use in heat transfer tubes (boiler tubes) for heat-recovery boilers which are used in a high-temperature corrosive environment where chloride-containing fuel ash condensates are deposited on the surface of boiler tubes.
More particularly, the present invention is concerned with an austenitic high-Cr, high-Ni alloy which is particularly useful in a high-temperature corrosive environment and which is suitable for use in boiler heat transfer tubes such as superheater tubes, reheater tubes, evaporator tubes, and water-wall tubes for heat-recovery boilers installed in facilities for incinerating municipal refuse, industrial waste, sewage sludge, and the like (hereinafter referred to collectively as refuse) for energy recovery, black-liquor combustion boilers installed in paper factories, and other heat-recovery boilers.
Recently there has been much interest in utilizing energy of municipal refuse because it can take full advantage of the potential energy of waste materials. In fact, power generation by incinerating municipal refuse has already been performed in some municipal incinerators for internal use and for electricity supply to utilities. Also in the paper industry, black-liquor combustion boilers have been used for firing black liquor formed as a by-product in a pulping process in order to recover soda and generate electric power using the waste heat of combustion.
To maximize the efficiency of electricity generation in the above-described heat-recovery system, it is desirable to increase the temperature .and pressure of the steam. However, an increase in steam temperature results in an increase in the metal temperature of the boiler tubes, thereby accelerating corrosion of the tubes. An increase in steam pressure requires a material which has an improved high-temperature strength. Heat-recovery boilers presently used in municipal waste incinerators are predominantly those operated such that the metal temperature of superheater tubes is around 800.degree.-900.degree. F. However, it is expected that operating conditions with a higher metal temperature of superheater tubes which exceeds 900.degree. F. will be employed in the near future in heat-recovery boilers for refuse incinerators (hereinafter referred to as refuse-fired heat-recovery boilers), as is the case in black-liquor combustion boilers, in order to improve the power generation efficiency.
Since municipal refuse includes a large amount of plastics, the exhaust gas upon incineration of municipal refuse contains a considerable amount of hydrogen chloride. The fuel ash condensates (fuel slag in the form of fused salt) which are the residues of incineration also contain chloride compounds. Therefore, the metallic material of heat transfer tubes used in refuse-fired heat-recovery boilers suffers not only corrosion resulting from gaseous attack by hydrogen chloride but also corrosion induced by deposition thereon of chloride-containing fused fuel slags (so-called "hot corrosion"). These types of corrosion become serious problems in refuse-fired heat-recovery boilers. The same problems are also found in boiler tubes for black-liquor combustion boilers, since they are attacked by SO.sub.2 -containing combustion gases and chloride-containing fuel ash condensates, which are both corrosive.
Under the above-described circumstances, there is a need for a material for heat transfer tubes which has good high-temperature strength and improved corrosion resistance sufficient to withstand these severe corrosive environments at high temperatures.
Corrosion-resistant steels or alloys of austenitic phases which are known to have excellent high-temperature strength are desirable for use in high-temperature boiler tubes such as superheater tubes for heat-recovery boilers operated at high temperatures and high pressures.
Various materials of austenitic phases have been investigated in the United States for use in heat-recovery boiler tubes for municipal incinerators. For example, it is reported in Corrosion 87, Mar. 9-13, 1987, Paper No. 402 that tubes of Incoloy Alloy 825 (which corresponds to alloy NO8825 specified in ASTM B163 and B423) containing about 42% Ni, 22% Cr, and 3% Mo by weight were actually used as heat-recovery boiler tubes in a commercial municipal incinerator. According to that article, the high-Ni alloys exhibited improved corrosion resistance with minimum tube thinning caused by corrosion in high-temperature corrosive environments normally encountered in municipal incinerators in the United States.
Other articles dealing with corrosion of commercially-available conventional austenitic high-alloy steels in the above-described high-temperature corrosive environments include Corrosion 85, Mar. 25-29, 1985, Paper No. 12; Corrosion 89, Apr. 17-21, 1989, Papers Nos. 204, 206, 209, and 550; and P. Ganesan et al, Industrial Heating, December 1987, pp. 18-22. In "High-Temperature Corrosion of Tube Support and Attachment Materials for Refuse-Fired Boilers" by S. F. Chou et al, Proceedings of the 1985 ASME IEEE Power Generation Conference, Milwaukee, Oct. 20-24, 1985, various alloys including Incoloy Alloy 825 and Carpenter Alloy 20Cb-3 which contains 34.0% Ni, 2.5% Co, 20.0% Cr, and 2.0% Mo were tested for corrosion as a tube support and attachment material for refuse-fired heat-recovery boilers. These articles generally discuss uniform corrosion of austenitic high-alloy materials at very high temperatures in the range of 1100.degree.-1700.degree. F.
However, the maximum metal temperature of superheater tubes for refuse-fired heat-recovery boilers is estimated to be 1000.degree. F. at the highest. As described above, these boiler tubes are exposed to very severe corrosive conditions since they are attacked by chloride-containing fuel ash condensates deposited thereon in a hydrogen chloride-containing gas atmosphere. Therefore, it is necessary for such heat transfer tubes to have resistance not only to uniform corrosion but also to intergranular corrosion attack (which occurs preferentially at grain boundaries) in the temperature range of about 700.degree.-1000.degree. F. in the above-described environment. Furthermore, it is important that these tubes withstand stress corrosion cracking in such an environment, particularly in portions such as welded joints and bends where stresses are concentrated.
The present inventors investigated corrosion of various conventional austenitic alloys in the above-described high-temperature corrosion environment, including chloride-containing corrosive fused salts on the test materials as encountered in refuse-fired waste heater boilers and black-liquor combustion boilers. As a result, it was found that most of conventional high-Cr, high-Ni austenitic alloys such as Incoloy Alloy 825 have high susceptibility to stress corrosion cracking as well as uniform corrosion and intergranular corrosion under such conditions. Since boiler tubes are pressure vessels used at high temperatures and high pressures, it becomes a serious problem that conventional alloys are considerably susceptible to stress corrosion cracking in stress-concentrated portions such as weld joints and bends. This indicates a possibility of corrosion failure of tubes caused by stress corrosion cracking, and such a failure may lead to shutdown of an entire incineration plant. Therefore, it is important that a corrosion-resistant material for boiler tubes have good resistance to stress corrosion cracking.

Corrosion-resistant alloy heat transfer tubes for heat-recovery boilers