An amperometric sensor for uric acid and a manufacturing method thereof are disclosed, in which polyacrylamide is used to fix catalase, uricase and ferrocenecarboxylic acid on a working electrode. In determining concentration of uric acid, hydrogen peroxide is produced when enzyme and uric acid react with each other and then a reduction current generated from enzyme on the electrode with an external voltage 200 mV applied is detected. In determining concentration of uric acid, a concentration range of 2.5-20 mg/dl is achieved and sensibility of the sensor in a linear portion is 5.17 uAcm−2(mg/dl)−1. In addition, reaction time required for the reaction between enzyme and uric acid is 5.17 uAcm−2(mg/dl)−1.

1. Field of the Invention
The present invention relates to an amperometric sensor for uric acid and a manufacturing method therefor. More particularly, the present invention relates to a disposable amperometric sensor for uric acid suitable for various biosensing uses and a method therefor in which a carbon electrode is fabricated by a stencil printing process, contributing to mass production of such sensor.
2. Description of the Prior Art
There are some quantitative analysis technologies set forth for organic matters in the past. Such prior art may be, for example, an article by Jian-yuan, Chen, 1993, entitled "Development and application of biosensors", Bioindustry, vol. 4, issue 3, pp. 205-212; an article by Ding-Guo, Huang, Wu-shun and Rui-qi, Zheng, 1996, entitled "Introduction to biosensors and future development therefor", Bioindustry, vol. 7, issue 4, pp. 291-298; an article by S. Zhang, G. Wright and Y. Yang, 2000, entitled "Materials and techniques for electrochemical biosensor design and construction", Biosensors and Bioelectronics 15: 273-282. However, disadvantages have been seen in practical uses with respect to these technologies. For example, complex operating processes, prolonged analysis time and pricy equipment are involved with such quantitative analyses. Further, such analysis technologies may not be applied for detection of continuous processes. Therefore, a solution capable of compensating for the disadvantages of the conventional quantitative analyses has been sought. A biosensor, which is achieved by combination of biochemistry, electronic circuits, material science, optics, among others, can be such solution and may be used in a wide range of fields.
The following will be made to introduction to development of the biosensors for the recent 30 years. The biosensors were commenced from the concept of an enzyme electrode set forth by Clark and Lycons, 1962, in which glucose oxides and an oxygen-containing electrode are combined to determine a consumed amount of the oxygen in a reaction process so as to determine concentration of the glucose. In 1967, Updike and Hicks fixed glucose oxide in polyacylamide gel to determine concentration of the glucose with the presence of the oxygen-containing electrode. Based on this principle, a current-determination based enzyme electrode was manufactured as a first generation biosensor.
As of 1975, Yellow Springs Instruments (YSI) of the United State began to render such technology into production. In 1979, a first generation sensor product, glucose determining pen, hit the market (Cass, 1989), which was used in medical examinations. For recent years, biosensors have been greatly improved with the aid of mature development of biochemistry, electrochemistry, material science and the like, and are anticipated to find more applications and values.
Currently, colorimetric and electrochemical methods are typically used for uric acid detection. The colorimetric method comprises a reducing method and a spectrophotometric method. In performing the latter method, generally used for the subject purpose, alantion and hydrogen peroxide are first obtained by oxidizing uric acid by uricase. Then, the obtained hydrogen peroxide is mixed with peroxidase and a color rendering reducing agent, such as o-dianisidine and 4-aminoantipyrine.phenol, for color rendering. Further, a suitable wavelength is selected to determine concentration of the uric acid. This method is susceptible to interferences caused by interference sources in human body, such as vitamin C, bilirubin and solved blood, and thus an error is unavoidably introduced. In addition, these conventional analyses also have the disadvantages of long detection time and troublesome operating steps. Further, no real time outputted detection data may be obtained by using these methods.
In this regard, various analysis technologies have been set forth by looking at these disadvantages, in which electrochemical principle is relied on.
In 1974, an uric acid biosensor was first set forth in an article by M. Nanjo and G. G. Guilbaut, entitled "Properties of carbon fiber micro-electrode as a basis for enzyme biosensor", Anal. Chem., Acta. 46, vol. 12, 1974, pp. 275-283. In this technology, biosensing of concentration of uric acid is conducted based on determination of a consumed amount of oxygen by fixing bovine serum albumin (BSA) on oxygen-contained electrodes with glutaraldehyde, with a linear range of up to 0.5 mM. However, since dissolubility of oxygen may vary as temperature and ambient environment vary, this method has the disadvantage of being limited by the maximum oxygen dissolubility, which is 8 ppm or 2.5×10−4 M under a pressure of 1 atm and a temperature of 25° C.
In 1991, a method for determining concentration of uric acid was proposed in an article by T. Tatsuma and T. Watanable, entitled "Oxidase/peroxidase bilayer-modified electrodes as sensor for lactate, pyruvate, cholesterol and uric acid", Anal Chim Acta, 1992, vol. 242, pp. 85-89. In this method, peroxidase is first fixed on a tin (VI) oxide electrode with glutaraldehyde through a covalent bonding mechanism and then uricase and ferrocenemonocarboxylic acid are added into a working buffer solution. As such, concentration of the uric acid may be determined in a low temperature without being interfered by vitamin C, with a linear arrange of up to 7.5 μM-1 mM achieved.
In 1992, a method for indirectly determining concentration of uric acid was proposed in an article by M. Shaolin, K. Jinqing and Z. Jianbing, entitled "Bioelectrochemical response of the polyaniline uricase electrode", Electroanal Chem, 1994, vol. 334, pp. 121-132. In this method, uricase is firmly buried within a polyanline film since such polyanline film is provided with a good stability and conductivity so that the negative-charged uricase may be successfully enclosed by the polyanline film and hard to run off therefrom. By determining peroxide hydrogen produced by uricase and uric acid, concentration of uric acid may be indirectly determined with a linear range of approximately up to 1.2 μM-1.2 mM. However, the polyanline may have a reduced conductivity as increase of pH value of the ambient environment and cannot exclude other negative-charged substance, delimiting its practical use.
In 1994, another method for indirectly determining concentration of uric acid was set forth in an article by M. T. Gilmartin and J. P. Hart, entitled "Determining with chemically and biologically modified carbon electrodes: a review", Analyst, vol. 120, 1995, pp. 1029-1045. In this method, acetic acid cellulose is first adorned on a stencil print electrode containing ferrocenemonocarboxylic acid and uricase is then fixed on the electrode. By determining peroxide hydrogen produced by reaction between uricase and uric acid, concentration of uric acid may be determined in an indirect manner. This working electrode having a multi-layered structure forms a shield and thus interferences may not be involved with the determination process.
In 1995, another method for determining concentration of uric acid is proposed in an article by O. Eleke, D. Moscone, K. Venema and J. Korf, entitled "Bi-enzyme reactor for electro-chemical detection of low concentration of uric acid and glucose", Clin Chim Acta, vol. 239, 1995, pp. 153-165. In this method, uric acid is clinically analyzed by using flow injection analysis (FIA) method. In determining concentration of the uric acid, uricase and horseradish peroxidase are fixed on a nitric acid cellulose film in a physically adsorptive manner. Further, ferrocenemonocarboxylic is also added. As such, concentration of uric acid may be determined in the presence of a low voltage through which the determination process may be prevented from interferences, with a linear arrange approximately up to 30 nM-200 μM.
In 1996, an article by E. Miland, A. J. Miranda Ordieres, P. Tunon Blanco and M. R. Smyth, entitled "Poly(o-aminophenol)-modified bienzyme carbon paste electrode for the detection of uric acid, Talanta, vol. 43, 1996, pp. 785-796. Uric acid and peroxidase bi-enzymes are mixed into a carbon paste electrode and then a single o-amino-phenol layer is electropolymerized on the electrode so that interferences may be removed. However, a huge amount of enzyme has to be involved in manufacture of the working electrode, increasing cost thereof and thus making unsuitable for hitting the market. In this technology, a linear range of 3 μM-10 mM is achieved. In the same year, another uric acid sensor is set forth in an article by Z. Gong and Z. Zhang, "A fiber optic biosensor for uric acid based on immobilized enzymes", Anal. Lett, vol. 5, 1996, pp. 695-709. In the article, concentration of uric acid is determined by a fiber optic biosensor, in which uricase, peroxidase and bovine serum albumin (BSA) are fixed on an optic fiber. First, uric acid is oxidized by uricase and hydrogen peroxide is thus produced. Then, hydrogen peroxide is catalyzed by horseradish peroxidase, turning fluorescence Thiamine into Thiochrome. By determination of intensity of fluorescence emitted from Thiochrome, concentration of uric acid may be determined, with a linear range of 3 μM-30 μM.
In 1998, another method of determining concentration of uric acid is set forth by Susumu Kuwabata, Takahiro Nakaminami, Shin-ichiro Ito and Hiroshi Yoneyama, entitled "Preparation and properties of amperometric uric acid sensors", Sensors and Actuator B, vol. 52, 1998, pp. 72-77. In this method, a self-assembled monolayer is adorned on an Au electrode and the uricase is fixed on the electrode. Further, potassium hexacyanoferrate (III) is added into a working buffer solution so as to avoid from interferences with the determination of concentration of uric acid. Then, an electrochemical method is used to determine concentration of uric acid, by which a linear range of about 0.1 mM-0.6 mM is achieved.
In 1999, another method for determining concentration of uric acid is set forth by Takahiro Nakaminami, Shinichiro Ito, Susumu Kuwabata and Hiroshi Yoneyama, "A biomimetic phospholipid/alkanethiolate bilayer immobilizing uricase and an electrode for amperometric determination of uric acid", Analytica Chemistry, vol. 71, 1999, pp. 4278-4283. In this method, a self-assembled monolayer is adorned on an Au electrode and uricase and 1-methoxy-5-mehylphenazinium are fixed on the electrode in a bi-layer configuration. Then, an electrochemical method is used to determine concentration of uric acid, by which a linear range of about 0.1 mM-0.8 mM is achieved.
In 2000, another method for determining concentration of uric acid is set forth by Shi-ting, Wen, Development and application of current-determination based uric acid biosensor, Biotechnology Institute, Chinese Culture University, Thesis for Master's degree, 2000, pp. 1-89. In this method, a carbon electrode is used as a working electrode and uricase and horseradish peroxidase are fixed on the electrode. Further, ferrocenemonocarboxylic acid is also added into a working buffer solution. By means of an electrochemical method, concentration of uric acid is determined with a linear range of 0.01-2 mg/dl.
Patent wise, the following has been disclosed.
Yen-Shih Shen et al. disclosed a disposable non-enzymatic uric acid determining electrode specimen in U.S. Pat. No. 6,258,230 "Non-enzymatic disposable uric acid detecting electrode strip, method for manufacturing the same and application therefor". With an external voltage of below 400 mV and a pH value set between 7 and 10, concentration of uric acid in solution may be directly determined. In case of concentration of uric acid in human body by the electrode specimen, interferences from other components and vitamin C in blood may be avoided. In determination of concentration of uric acid, serum or blood may be directly used for the electrode specimen. Such kind of electrode specimen is mainly manufactured by ferrocenemonocarboxylic acid dissolvable in water and easy to be carried and mass-produced.
Yen-Shih Shen et al. disclosed a disposable non-enzyme uric acid determining electrode specimen in R.O.C. Patent 00369411 "Disposable current-determination based non-enzymatic uric acid electrode specimen and manufacturing method and application therefor". With an external voltage of below 400 mV and a pH value set between 7 and 10, concentration of uric acid in solution may be directly determined. In case of concentration of uric acid in human body by the electrode specimen, interferences from other components and vitamin C in blood may be avoided. In determination of uric acid, serum or blood may be directly used for the electrode specimen. Such kind of electrode specimen is mainly manufactured by ferrocenemonocarboxylic acid dissolvable in water and easy to be carry and mass produced. In this patent, a diagnosis and reagent system is disclosed, in which alkaline tungsten phosphate and body fluid without protein contained react with each other and thus a sulfur-containing composite is produced. As such, concentration of uric acid may be determined.
In U.S. Pat. No. 4,348,208, Robert L. Long disclosed a diagnostic assay and reagent system for the determination of uric acid directly on a non-deproteinized sample of a biological fluid using an alkaline phosphotungstate reduction reaction in the presence of at least one organic sulfhydryl-containing compound.
Douglas E. Faulkner disclosed an uric acid detecting mode in U.S. Pat. No. 4,234,313 "Device and method for quantitative uric acid testing". A color indicator disposed on a substrate is used to display a specific color based on the principle that color of uric acid disappear after combination with a reagent. As such, concentration of uric acid may be directly determined. In this detecting mode, a thin film is involved to prevent from deposition of other interference sources.
E. Melvin Gindler disclosed an aqueous solution useful in connection with a redox type spectrophotometric or calorimetric determination of uric acid in a biologic fluid in U.S. Pat. No. 4,072,627 "Uric acid determination". The solution contains either a multivalent metallic ion reducible to a lower valence state by uric acid, a water soluble chelating compound capable of complex with a metallic ion after reduction by uric acid to yield, in complexes form, a colored complex, or a combination of said ion and said chelating compound. The solution also contains, as an added constituent, imidazole, an alpha-amino acid, or a combination thereof. This constituent is present in an amount such that, when said solution contains a biologic fluid containing protein and uric acid, a buffer system such that the pH of the solution is 6 to 12, and a multivalent metal ion, the protein in the fluid does not significantly reduce said multivalent ions present in the solution.
In U.S. Pat. No. 6,699,720, Tsai-Yun Lee et al. disclosed an interference-eliminating membrane for use in detecting uric acid in a sample. The patent related to the interference-eliminating membrane for use in detecting uric acid in a sample, comprising a compound for inhibiting or shading uric acid interfering substances, or derivatives thereof, and a carrier having an absorption property and permeability for the sample; and a process for preparing the interference-eliminating membrane. The present invention also provides a test strip for use in detecting uric acid in a sample, comprising a reagent reaction layer or optional interference-eliminating membranes and/or support layers, and a kit comprising the test strip of the invention.
In U.S. Pat. No. 4,379,780, Gunther Gorka and Klaus Stinshoff disclosed a method for determining the concentration of uric acid in a biological material by contacting the biological material with a reagent comprised of uricase, catalase, aldehyde dehydrogenase, a lower alkanol, and nicotinamide adenine dinucleotide or nicotinamide adenine dinucleotied phosphate, the improvement which comprises determining the uric acid content in the presence of 2-mercaptosuccinic acid.
In U.S. Pat. No. 4,317,878, Toru Nakanishi and Yoshimi Shigemasa disclosed a method for quantitative determination of uric acid in sample by using acidic uricase that is produced by fermentation of a microorganism of the genus Streptomyces.
In light of the above, there are still some shortcomings inherent in the prior art and thus improvements therefor are in an urgent need. In this regard, the Inventors have paid many efforts in the related research and finally developed successfully a amperometric sensor for uric acid and a manufacturing method therefor in the present invention.

Amperometric sensor for uric acid and method for the same


A work surface/storage system can be attached to a motor vehicle which has a passenger compartment with a driver seat, a passenger seat, a passenger restraint belt, and a dash panel in front of the passenger seat. A main body section of the system includes at least one flat surface for providing a writing support for a person in the driver seat, at least one storage bin, and a bottom surface for positioning on the passenger seat. A belt receptacle is located at a rearward end of the main body for capturing the passenger restraint belt so that tension in the passenger restraint belt loads the rearward end against the passenger seat. A front wing section extends forward and upward from the main body section to a distal end. The distal end includes an attachment tab. A bay is provided in the dash panel including a holder for capturing the attachment tab.

The present invention relates in general to interior features in a motor vehicle to facilitate mobile office tasks of a driver, and, more specifically, to a work surface/storage system to facilitate file keeping and writing tasks of a person (such as a police officer) in the driver seat of the vehicle.
Storage space and working surfaces within a typical motor vehicle are very limited. The performance of work or other activities involving office-like functions (e.g., writing on documents, using paper files and folders, or using personal items) is a challenge in a mobile environment.
Various tray systems have been proposed to provide a working surface. Some systems have deployed from the vehicle dashboard in the manner of a sliding shelf. U.S. Pat. No. 6,095,060 to Ma shoes a tray that connects by suction cups to the windshield and the dashboard. Other support structures have hung over the vehicle seat (e.g., U.S. Pat. No. 7,415,932 to Ngo).
A dual use of the passenger seating area is sometimes desirable because a vehicle may be used by only a driver (e.g., a highway patrol officer or a traveling sales representative). When no passenger is present, the space can instead be used for a storage system for the driver. Existing deployable systems, however, have suffered from the disadvantage that they lack the stability and rigidity to perform well as a solid writing support surface. Movement of the support surface not only makes writing difficult, but may cause beverages or other items spill from their associated compartments. Therefore, a system is needed that is easily mounted and yet provides a stable and rigid support surface together with storage capabilities associated with office-like functions in a motor vehicle.

Office system for motor vehicle passenger compartment


Concentrated aqueous photographic fixing compositions include a photographic fixing agent and a compound represented by Structure I

This invention relates to novel concentrated photographic fixer additive and concentrated photographic fixing compositions. It also relates to methods of using these concentrated compositions in photoprocessing. Thus, this invention relates to the photographic industry and to photochemical processing in particular.
The conventional image-forming process of silver halide photography includes imagewise exposure of a photographic silver halide recording material to actinic radiation (such as actinic light), and the eventual manifestation of a useable image by wet photochemical processing of that exposed material. A fundamental step of photochemical processing is the treatment of the material with one or more developing agents to reduce silver halide to silver metal. With black-and-white photographic materials, the metallic silver usually comprises the image. With color photographic materials, the useful image consists of one or more images in organic dyes produced from an oxidized developing agent formed wherever silver halide is reduced to metallic silver.
To obtain useful color images, it is usually necessary to remove all of the silver from the photographic element after color development. This is sometimes known as xe2x80x9cdesilveringxe2x80x9d. Removal of silver is generally accomplished by oxidizing the metallic silver, and then dissolving it and undeveloped silver halide with a xe2x80x9csolventxe2x80x9d or fixing agent in what is known as a fixing step. Oxidation is achieved with an oxidizing agent, commonly known as a bleaching agent.
Fixing is typically carried out using a fixing composition that includes one or more fixing agents such as thiosulfate salts. Both ammonium and sodium thiosulfate salts are known. Fixing solutions containing ammonium ions are preferred for providing more rapid fixing, but they present environmental concerns. Thus, fixing solutions containing sodium ions, while slower, are also advantageous.
Color photographic silver halide materials often contain various sensitizing dyes that extend the inherent photosensitivity of the photosensitive silver halide emulsions to electromagnetic radiation. One important class of such sensitizing dyes are carbocyanine sensitizing dyes that are commonly included in silver halide emulsion layers in photographic silver halide films, for example in color reversal photographic silver halide films (films normally used to provide positive color images).
Many photographic silver halide elements contain residual sensitizing dyes after photoprocessing. In some cases, the level of retained sensitizing dyes is inconsequential and thus, unobservable. In other instances, however, the high level of retained sensitizing dye results in undesirably high dye stain (or unwanted color) in the elements.
A number of solutions have been proposed for this problem, including the inclusion of water-soluble stilbene optical brighteners in the color developer solution [as described for example, in Research Disclosure, 20733, page 268, July, 1981 and U.S. Pat. No. 4,587,195 (Ishikawa et al)], the bleach-fixing solution [as described for example, in JP 1-062642 (published Mar. 9, 1989), JP 1-158443 (published Jun. 21, 1989), and U.S. Pat. No. 5,043,253 (Ishikawa)], or the stabilizing solution used at the end of the photoprocessing [as described for example in U.S. Pat. No. 4,895,786 (Kurematsu et al)].
Concentrated and working strength fixing compositions that solve the residual dye stain problem are described in U.S. Pat. No. 6,013,425 (Craver et al). These compositions contain certain triazinylstilbene compounds as stain reducing agents. While they are quite effective in this regard, keeping them in solution may require the presence of one or more water-soluble stabilizing compounds such as glycols.
The problems with residual sensitizing dyes have also been satisfactorily addressed by incorporating certain stain reducing agents into one or more working strength photographic processing compositions. These compounds are described in copending and commonly assigned U.S. Ser. No. 09/464,551 filed Dec. 16, 1999 by Goswami et al., now U.S. Pat. No. 6,153,365, and U.S. Ser. No. 09/464,961 filed Dec. 16, 1999 by Goswami et al., now U.S. Pat. No. 6,153,364, as colorless or slightly yellow compounds having an extended planar xcfx80 system that is devoid of a diaminostilbene fragment or fused triazole nuclei. While these compounds can be incorporated into various photoprocessing compositions, it is preferred to include them in concentrated photographic fixing compositions.
However, when we attempted to incorporate some of these stain reducing agents into concentrated solutions such as concentrated fixing solutions, we found that some of them did not pass our rigorous solubility tests. For example, many of them showed unacceptable solubility even when organic solvents were added, insolubility in solution at low temperature for lengthy times, or insolubility in concentrated fixing composition.
There remains a need in the photographic industry for a way to decrease the dye stains resulting from retained sensitizing dye during photoprocessing using concentrated processing compositions that meet all manufacturing, customer use, and storage stability requirements.
The problems with known photographic compositions and photoprocessing methods are overcome with the use of the present invention.
In one embodiment, the present invention provides a concentrated aqueous fixer additive composition consisting essentially of:
a) at least 0.01 mol/l of a compound having the structure I
wherein R is carboxy or sulfo, m is an integer of from 0 to 5 and n is an integer of from 2 to 7, and
b) water.
This concentrated fixer additive composition can be used to advantage to prepare the concentrated aqueous fixing composition of this invention, which composition has a pH of 8 or less and consists essentially of:
a) at least 2 mol/l of a photographic fixing agent,
b) at least 0.0001 mol/l of a compound represented by Structure I noted above, and
c) water.
Once the concentrated aqueous fixing composition is prepared, it can be used to prepare an aqueous working strength fixer or replenisher. Thus, this invention further provides a method of making an aqueous working strength fixing composition comprising the steps of:
A) preparing the concentrated aqueous photographic fixing composition noted above by mixing the concentrated fixer additive composition described above with the photographic fixing agent, and
B) diluting the resulting concentrated aqueous photographic fixing composition from about 2 to about 15 times.
This invention further provides a method for providing a color image comprising:
A) bleaching an imagewise exposed and color developed color photographic silver halide element, and
B) prior to or after step A, fixing the photographic element with an aqueous working strength photographic fixing composition prepared from the concentrated fixing composition described above.
Step B of this method can also be carried out by diluting, at least 2 times, the concentrated aqueous photographic fixing composition described above.
The advantages of this invention are several. The concentrated fixer additive composition can be manufactured, provided and stored for considerable time without precipitation of the stain reducing agent, thereby reducing the costs associated with volume and storage. The fixer additive composition volume can be small enough so as not to significantly dilute the concentrate to which it is added. Because there is no need for solvents other than water, there is no additional environmental burden. The resulting working strength fixing composition is also highly stable, and can be used to advantage to reduce stain from retained sensitizing dyes in processing photographic silver halide elements.
Only the specific stain reducing agents represented by Structure I provide the desired stability in the concentrated compositions of this invention. Thus, the compounds of Structure I meet the following minimal stability standards:
a) they are soluble at 33 g in 500 ml of water,
b) they have low temperature solubility that is determined by placing 100 ml aqueous samples of the compounds in closed containers and holding them individually it at 0xc2x0 F. (xe2x88x9218xc2x0 C.), 20xc2x0 F. (xe2x88x927xc2x0 C.), 30xc2x0 F. (xe2x88x921xc2x0 C.) 40xc2x0 C. (4xc2x0 C.), 50xc2x0 F. (10xc2x0 C.) and 70xc2x0 F. (21xc2x0 C.) for 14 days and then observing the samples 24 hours later for signs of precipitation or other observable changes (for example color, presence of haze, or phase separation), and
c) they cause no precipitation at 33 g in a 18.9 liter volume of commercially available KODAK Fixer and Replenisher Process E-6 AR at room temperature for at least 3 days (preferably at least 10 days).
Working strength fixing compositions can be prepared in several ways using the present invention. The concentrated fixer additive composition can be added directly to a working strength composition containing a suitable fixing agent, or mixed with the appropriate fixing agents in appropriate amounts to form the concentrated aqueous fixing composition. This composition can then be diluted in an appropriate manner and used for photoprocessing.
The concentrated and working strength photographic fixing compositions described herein perform only one photoprocessing function, fixing. They do not perform a bleaching function, so the compositions are not bleach-fixing compositions. The language xe2x80x9cconsisting essentially ofxe2x80x9d is intended to indicate that no photographic bleaching agents (such as iron chelates, peroxides or persulfates) are intentionally added to the fixing composition of this invention. Any small amounts of bleaching agents may be present merely because of carryover from previous photoprocessing baths.
The language xe2x80x9cconsisting essentially ofxe2x80x9d is also meant to exclude significant amounts of organic solvents such as solubilizing solvents in the fixing concentrates or fixer additive compositions of this invention. Such solvents may be present in small amounts that have no meaningful effect.
As used herein unless otherwise indicated, the term xe2x80x9cfixing compositionsxe2x80x9d refers to both the concentrated and working strength fixing compositions.
Useful fixing agents for photographic fixing compositions are well known. Examples of photographic fixing agents include, but not limited to, thiosulfates (for example sodium thiosulfate, potassium thiosulfate and ammonium thiosulfate), thiocyanates (for example sodium thiocyanate, potassium thiocyanate and ammonium thiocyanate), thioethers (such as ethylenebisthioglycolic acid and 3,6-dithia-1,8-octanediol), imides and thiourea. Thiosulfates and thiocyanates are preferred, and thiosulfates are more preferred. Ammonium thiosulfate is most preferred.
It is also known to use fixing accelerators in fixing compositions. Representative fixing accelerators include, but are not limited to, ammonium salts, guanidine, ethylenediamine and other amines, quaternary ammonium salts and other amine salts, thiourea, thioethers, thiols and thiolates. Examples of useful thioether fixing accelerators are described in U.S. Pat. No. 5,633,124 (Schmittou et al).
A critical component of the concentrated fixer additive and photographic fixing compositions of this invention is a spectral sensitizing dye stain reducing agent that is a 2,6-dinaphthylaminotriazine compound as represented by Structure I (or mixture thereof). These compounds have at least four sulfonate solubilizing groups attached to the naphthyl rings and specific substituents attached to the triazine ring.
The compounds useful in this invention can be represented by Structure I:
wherein R is carboxy (or salt thereof) or sulfo (or salt thereof), m is an integer of from 0 to 5, and n is an integer of from 2 to 7. Preferably, R is carboxy, m is an integer of 1 to 2, and n is 2.
Representative compounds within Structure I are the following Compounds I-1 to I-7:
Single compounds or mixtures thereof can also been used in the practice of this invention. Compound I-1 (or an alkali metal salt thereof) noted above is most preferred.
These 2,6-dinaphthylaminotriazine compounds can be prepared using the methods described for example in WO 97/10887. A representative synthesis of preferred Compound I-1 is provided below.
The concentrated fixer additive compositions of this invention have only two essential components: one or more compounds of Structure I and water. However, optional and nonessential components may be present if desired. Such components include buffers, sequestering agents, preservatives (such as sulfites), and other addenda that would be readily apparent to one skilled in the art.
While the concentrated fixing compositions of this invention have only three essential components: one or more fixing agents, one or more compounds of Structure I, and water, they can also include one or more of various nonessential addenda optionally but commonly used in such compositions for various purposes, including hardening agents, preservatives (such as sulfites or bisulfites), metal sequestering agents (such as polycarboxylic acids and organophosphonic acids), buffers, and fixing accelerators. The amounts of such addenda in the working strength compositions would be readily known to one skilled in the art. The amounts useful in the concentrate compositions would be readily apparent from the teaching included herein.
The desired pH of the fixing compositions of this invention is 8 or less, and can be achieved and maintained using any useful combination of acids and bases, as well as various buffers. The pH of the concentrated fixing composition can vary from that of the working strength fixing composition.
Other details of fixing compositions not explicitly described herein are considered well known in the art, and are described for example, in Research Disclosure publication 38957 (noted below), and publications noted therein in paragraph XX(B), incorporated herein by reference.
The following TABLE I shows the general and preferred pH and amounts of essential components of the concentrated additive composition and the fixing compositions of this invention. The preferred ranges are listed in parentheses ( ), and all of the ranges are considered to be approximate or xe2x80x9caboutxe2x80x9d in the upper and lower end points. During fixing, the actual concentrations can vary depending upon extracted chemicals in the composition, fixer replenishment rates, water losses due to evaporation and carryover from the preceding processing bath and carryover to the next processing bath. The working strength fixing composition concentrations are based on a dilution rate of from about 2 to about 15 of the concentrated fixing composition.
During fixing, the fixing composition in the processor may accumulate dissolved silver halide, and other substances that are extracted from the processed photographic element. Such materials, and particularly silver halide, can be removed using known means, such as ion exchange, electroysis, electrodialysis and precipitation.
Fixing can be carried out using a single working strength fixing composition bath (single stage), or multistage methods. Agitation or recirculation can also be used if desired. Fixing can also be carried out using any known method for contacting a fixing composition and the photographic element. Such methods include, but not limited to, immersing the photographic element in the working strength fixing composition, laminating a cover sheet containing the fixing composition to the photographic element, and applying the fixing composition by high velocity jet or spraying.
Since the fixing step is a separate step in an overall image-forming method, any processing sequence can be used for processing either black-and-white or color photographic elements. Representative processing sequences are described for example in Research Disclosure publication 308119, December 1989, publication 17643, December 1978, and publication 38957, September 1996. Research Disclosure is a publication of Kenneth Mason Publications Ltd., Dudley House, 12 North Street, Emsworth, Hampshire PO10 7DQ England. For example, in processing black-and-white photographic elements, fixing is usually preceded by a developing step, and may be followed with one or more washing or stabilizing steps.
Preferably, the compositions of the present invention are used to process color photographic elements, including but not limited to, color negative photographic films, color reversal photographic films, and color photographic papers. The general sequence of steps and conditions (times and temperatures) for processing are well known as Process C-41 and Process ECN-2 for color negative films, Process E-6 and Process K-14 for color reversal films, and Process RA-4 for color papers. The processing solutions used for the various processing steps in such processing sequences are also well known (except for the fixing steps carried out in this invention).
More preferably, the Compositions are used to provide positive color images in color reversal photographic films. The typical sequence of steps includes first development (black-and-white development), reversal processing step, color developing, bleaching, fixing, and stabilizing. There may be various washing steps between other steps, as well as a pre-bleach step or conditioning step before bleaching. Alternatively, stabilizing can occur between color developing and bleaching. Many details of such processes are provided in U.S. Pat. No. 5,552,264 (Cullinan et al), incorporated herein by reference. Other details are provided in Research Disclosure, publication 38957 (noted above), and references noted therein.
Color reversal films are comprised of a support having thereon a plurality of photosensitive silver halide emulsion layers that can contain any conventional silver halide (or mixture thereof). Such films generally have silver halide emulsions having at least 1 mol % iodide based on total silver.
Useful supports are well known and include polyester films, polycarbonate films and cellulose acetate films. The silver halide layers include conventional binder materials, and other conventional addenda. Some specific commercially available color reversal photographic films that can be processed using this invention include EKTACHROME Color Reversal Films (Eastman Kodak Company), FUJICHROME Color Reversal Films (Fuji Photo Film Co., Ltd.), AGFACHROME Color Reversal Films (AGFA), KONICACHROME Color Reversal Films (Konica) and SCOTCHCHROME Color Reversal Films (3M Corporation).
The first developing step is usually carried out using a conventional black-and-white developing solution that can contain black-and-white developing agents, auxiliary co-developing agents, preservatives, antifoggants, anti-sludging agents, buffers and other conventional addenda.
Color developing is generally carried out using one or more conventional color developing agents, such as primary amino color developing agents. The color developing solution can also include various other conventional addenda including preservatives (including hydroxylamine and its derivatives), fluorescent dyes, sulfites, sequestering agents, corrosion inhibitors and buffers.
Bleaching is generally carried out using one or more bleaching agents that convert metallic silver to silver ions. Binary and ternary ferric complexes of aminopolycarboxylic acids are common bleaching agents, as well as persulfates and peroxides. Other components of the bleaching solution include buffers, halides and sequestering agents.
A photographic stabilizing step can be carried out using any dye stabilizing solution known in the art. Alternatively, a final rinsing step can be used.
For the fixing step of the method of this invention, the concentrated fixing composition of this invention can be diluted up 15 times, and preferably from 2 to 15 times (more preferably from 5 to 12 times), to provide a working strength or fixing replenishing composition. Dilution can be carried out during or prior to its use in the image formation process. In addition, the concentrated fixing composition can be added to the fixing solution bath, or to the fixer replenisher.
Fixing is generally carried out for conventional times and under conventional conditions. In addition, the fixing compositions of this invention can be used in what would be considered xe2x80x9crapidxe2x80x9d processing wherein the fixing step is carried out for as few as 10 seconds.
Processing can be carried out using any suitable processing equipment, including deep tank processors, and xe2x80x9clow volume thin tankxe2x80x9d processes including rack and tank and automatic tray designs, as described for example in U.S. Pat. No. 5,436,118 (Carli et al), and publications noted therein. Rotary tube processors can also be used for processing color reversal films.
The concentrated fixing composition of this invention is prepared by mixing the fixing agent and other fixing composition components (in appropriate amounts) with the concentrated additive composition of this invention. Alternatively, the Structure I compound can be added directly to the concentrated fixing composition.
The working strength composition can be prepared either by diluting the concentrated fixing composition appropriately with water and/or buffers, or by adding the concentrated fixing composition directly to the fixing bath or fixer replenisher.
The following synthetic procedure and examples are provided to illustrate the invention, and not to be limiting in any fashion.
Cyanuric chloride (133.0 g, 0.72 mole) was dissolved in 3 liters of acetone in a 12-liter flask equipped with a mechanical stirrer. Crushed ice (3 kg) was added to it. To this cold mixture was added all at once, while stirring, a solution containing 6-amino-1,3-naphthalenedisulfonic acid disodium salt (605 g, 88% purity, 1.53 mole) in 1800 ml water and 1200 g of ice. An aqueous solution (200 ml) of sodium hydroxide (57.6 g, 1.44 mole) was added portion-wise with stirring to the resulting mixture, as the reaction pH became acidic. The first 100 ml portion was added over 15 minutes while the reaction temperature was still less than 0xc2x0 C. This reaction mixture was then heated gradually by using a steam bath. The remaining 100 ml were added gradually over the next 1.25 hours while the reaction temperature was raised to 60xc2x0 C. The reaction mixture was stirred at 60xc2x0 C. for an additional 2 hours and was then cooled to room temperature.
The resulting reaction mixture was slowly poured into a solvent mixture containing 60 liters of acetone and 6 liters of methanol, while stirring. It was then allowed to settle overnight and 40 liters of solvent was removed by decanting. The resulting solid was collected on an 11.5 inch (29.2 cm) diameter funnel using a VWR #413 filter paper. The solid was then washed with acetone and P950 ligroin, and was air-dried on the funnel. The resulting solid clumps were crushed and the powder was dried in a vacuum oven overnight, giving rise to 560 g (yield: 96.5%) of the desired chloro intermediate.
Sodium bicarbonate (118 g, 1.4 mole) was added to 2.5 liters of water in a 5-liter flask. 3-Aminobenzoic acid (92 g, 0.67 mole) was added portion-wise to this solution while being heated to 85xc2x0 C. The chloro intermediate prepared as described above (550 g, 0.68 mole) was added to this solution portion-wise over a period of 15 minutes. The resulting mixture was heated at 85-90xc2x0 C. overnight. It was then allowed to cool to room temperature overnight. Small amounts of insoluble materials were filtered off using a glass-fiber filter paper. The filtrate was poured into 11 liters of acetone. It was stirred for 5 minutes and was allowed to settle. The clear acetone supernatant was decanted off. The resulting amber oil was added to a mixture of 25 liters of acetone and 2.5 liters of methanol, and was stirred for 10 minutes. The resulting solid was collected on an 11.5 inch (29.2 cm) diameter funnel using a VWR #413 filter paper. The resulting solid was first washed with a mixture containing 10:1 acetone: methanol (5 liters), then with acetone (5 liters), and finally with P950 ligroin (5 liters). The solid was then air-dried on the funnel. The solid clumps were crushed and the powder was dried in a vacuum oven at 50xc2x0 C. for 2 days, giving rise to 547 g (yield: 87.8%) of the desired Compound I-1.

Concentrated photographic fixer additive and fixing compositions and method of photographic processing

Abstract: wherein R is carboxy or sulfo, m is an integer of from 0 to 7 and n is an integer of from 2 to 5. This compound is provided in a concentrated aqueous fixer additive composition. These compositions can be used to provide images in color photographic materials, and particularly in color reversal films, with reduced residual sensitizing dye stain.


A recording method for an optical medium having a disk-like substrate with a spiral or concentric-shaped groove structure along a track formed on the substrate. The groove structure is wobbled in a radial direction of the medium and the track is divided into a plurality of units in the track direction by at least one radial boundary line formed by a dropout portion. Identification information is disposed in the track at a head of each recording unit at the dropout portion and the medium is divided into a plurality of zones in a radial direction with a length of a circular arc being substantially the same between the zones in a circumferential direction. At least two adjacent units in the radial direction of the medium comprise one zone. The method includes providing the optical medium, and recording information on the optical medium by irradiating an optical spot thereon.

The present invention relates to information recording media, and particularly to a high-density information recording medium and a high-density optical recording medium of which the track width is smaller than a beam spot or a detecting means such as a magnetic head.
Japanese laid-open patent publication No. 6-176404, for example, describes an example of a high-density (narrow track) recording medium. This example uses as a recording medium an optical recording medium in which groove portions and land portions are formed on a substrate and information recording areas are formed on both of the groove portions and the land portions. Prepits are formed on a virtual prolonged line of a boundary portion between the groove portion and the land portion as identification information of a recording unit (sector), whereby recording information is recorded on both of the groove portions and the land portions and identification (address) information indicative of a recording area is handled by the prepits. Also, one prepit commonly uses address information for a pair of groove portion and land portion. According to this system, when the recording medium of this system is applied to a phase change type recording medium and a magneto-optical recording medium, information from the adjacent land portion or groove portion can be prevented from being mixed into the groove portion and the land portion owing to an interference effect caused within the beam spot (i.e. crosstalk can be cancelled out), and hence the tracks of the recording medium can be narrowed, thereby making a high-density recording become possible.
However, in the example according to the related art, inasmuch as information indicative of the position on the information recording medium is concentrated in the prepit portions and the prepit portions located in a discrete fashion, position information cannot be obtained from portions other than the prepit portions. As a consequence, it is difficult to control a rotational speed of a disk precisely with a high reliability. There is then presented the problem from a reliability standpoint that the recording medium according to the relate art is not persistent to, in particular, defects or the like.

This patent is subject to a terminal disclaimer.


The present invention describes methods and apparatus for reliably assuring that correct mirror currents are selected during a channel switch to achieve the desired wavelength channel, based on feedback from either internal or external means combined with a mode map obtained at a time zero calibration.

1. Field of the Invention
The invention relates to the field of widely-tunable lasers, and more particularly, to methods for robust channel switching of widely-tunable sampled grating distributed Bragg reflectors (SGDBR) lasers.
2. Description of the Related Art
(This application references publications and a patent, as indicated in the specification by a reference number enclosed in brackets, e.g., [x]. These publications and patent, along with their associated reference numbers, are identified in the section below entitled "References.")
There are a variety of semiconductor laser designs in which the wavelength can be tuned by current injection into one or more sections of the laser that have some spectral filtering characteristics. Examples include moderately-tunable devices, such as distributed Bragg reflector (DBR) lasers, and widely-tunable devices, such as sampled grating distributed Bragg reflector (SGDBR) lasers.
In each of these devices, precise control of each of the currents provided to the various sections of the laser is required to achieve a desired output wavelength. The amount of current injected into each section to achieve a given wavelength can vary with both device temperature and aging. For example, over time, as the device ages, changes in leakage current and carrier lifetime in the tuning sections cause the laser output wavelength to drift. This variation in tuning characteristics requires the use of some sort of feedback control system in order for such tunable lasers to be used in applications where precise wavelength control must be maintained, such as dense wavelength division multiplexed (DWDM) communications systems.
Therefore, there is a need in the art for improved methods of channel switching of widely-tunable lasers. Specifically, there is a need in the art for methods that assure proper channel selection in spite of long-term aging or environmental effects.

Methods for robust channel switching of widely-tunable sampled-grating distributed bragg reflector lasers


When a receiver unit receives second data composed of check bits and first data obtained by encoding information bits indicating the communication contents by way of a first generator matrix based on a first generating polynomial, and then further encoding the first data by way of a second generator matrix of an irreducible standard form based on a second generating polynomial, an error location detector decodes the second data received by way of a second check matrix that is orthogonal to the second generator matrix so as to detect errors produced in the first data. A dummy syndrome generator generates a dummy syndrome of the error produced in the information bits based on the detected error location and on the first generating polynomial. A syndrome generator takes the product of the data obtained by excluding the check bits from the second data received by the receiver unit and the first check matrix that is orthogonal to the first generator matrix so as to generate a syndrome that indicates the error syndrome produced in the information bits. Finally, an error corrector corrects errors produced in the information bits if the dummy syndrome generated by the dummy syndrome generator is the same as the syndrome generated by the syndrome generator.

1. Field of the Invention
The present invention relates in general to an error correction apparatus and method, and in particular to an error correction apparatus and method with which a plurality of error correction encodings are performed for communication contents, and error corrections are reduced.
2. Description of the Related Art
With a conventional error correction technique for correcting errors that occurred during the sending of communication contents, the transmitting station would subject the communication contents (hereinafter referred to as "information bits") to redundant encoding before transmission, and the receiving station would correct errors based on this redundant code. With this error correction technique, the encoding method and generating polynomial to be used are specified based on the length of the information bits and on the error correction capability provided, coding is performed by producing a generator matrix from this coding method and generating polynomial, and decoding is performed by using a check matrix that is orthogonal to the generator matrix.
In specific terms, at the transmitting station, an information string is produced by taking the inner product of the information bit string and the generator matrix G, and the communication data containing this information string is transmitted to the receiving station, while at the receiving station, the error syndrome is calculated by taking the inner product of the received information string and the check matrix H (G.multidot.H=0) that is orthogonal to this generator matrix G.
Here, this "syndrome" refers to data indicating whether or not there are errors in the received information string, and confirmation of this syndrome allows errors to be detected. This syndrome, however, does not directly indicate the error location, so specification of the error location requires factoring or the like to be performed based on this syndrome. In specific terms, if this syndrome is "0," it means that there are no errors in the received information string, and if it is "1," it means that some kind of error is present.
Thus, performing error correction using a syndrome allows bit errors and burst errors to be corrected automatically. Nevertheless, even when this error correction technique is used, it does not keep track of all the errors, and skipped errors and improper corrections sometimes occur.
As a result, a system that demands a high level of communication quality does not stop at using error correction by itself, but rather employs a technique for enhancing the reliability of the error correction by combining error correction with error detection. For example, information bits are multiplied by a generator matrix G1 to produce an information string having undergone error detection coding, which in turn is multiplied by a generation matrix G2 to produce data having undergone error correction coding. The transmitting station sends the data thus produced to the receiving station, while the receiving station subjects this data to error correction using a check matrix H2 that is orthogonal to the generator matrix G2, after which it confirms whether there are any errors in the data by using a check matrix H1 that is orthogonal to the generator matrix G1.
The procedure of the above prior art, which combines an error correction technique with an error detection technique, will now be described.
FIG. 9 is a flow chart illustrating the procedure at the receiving station when an error correction technique is combined with an error detection technique. As shown in FIG. 9, when an information string transmitted from the transmitting station is received by the receiving station (step 901), the first thing the receiving station does is to confirm whether there are any errors in the information string. Specifically, the receiving station computes the error correction syndrome by multiplying the received information string by the check matrix H2 (step 902), and confirms whether an error has been generated in the information string based on this syndrome (step 903).
When an error is present in the information string, the error location is specified based on the error correction syndrome (step 904), and the error location is corrected (step 905). Here, the specification of the error location in step 904 will vary with the encoding method, but in the case of a double error correction code, the error location can be specified either by factoring a polynomial having the value of the syndrome as a coefficient, or by consulting a table listing the results of this factoring.
Next, in order to verify that the error correction of steps 903 through 905 above has actually been carried out, the error detection syndrome is calculated based on the check matrix H1 (step 906), and the information string that has undergone error correction is examined to see if any errors remain (step 907).
If there are no errors in the information string that has undergone error correction, then it is determined that there are no skipped errors or improper corrections, and the process is ended normally (step 908), but if there are errors present, then it is recognized that skipped errors or improper correction has occurred, and retransmission is requested (step 909).
Thus, using prior art in which an error correction technique is combined with an error detection technique allows skipped errors and improper correction to be confirmed, and the reliability of the communication information to be improved. However, with this prior art, since the determination as to whether correction has been performed is made after the errors produced in the information string have been corrected, error detection cannot be performed until the correction has been completed. Consequently, the correction process takes longer than when error correction is performed by itself, i.e., it is longer by the amount of time it takes to determine whether the error correction is proper using an error detection technique (syndrome generation time+time required for input/output).
Therefore, prior art in which an error correction technique is combined with an error detection technique cannot be used in a real application because improved reliability is achieved at the cost of processing time.
There is a technique with which error correction can be made parallel by using dual error correction techniques, and which does not involve a combination of an error correction technique and an error detection technique. Specifically, this technique comprises detecting error locations by means of dual error correction techniques, comparing the error locations of the two, and performing error correction if the error locations are in agreement.
In this case, the generator matrix G2 used in the second error correction encoding must be in an irreducible standard form so that the transmitted information string will be in a joint data format of check bits and data encoded with G1, and so that decoding by the check matrix H1 corresponding to the generator matrix G1 can be carried out in parallel with decoding by the check matrix H2 corresponding to the generator matrix G2.
However, when this technique is used, as relates to finally confirming the correctness of errors by contrasting error locations of the two, decoding by the check matrix H1 and the check matrix H2 is insufficient with syndrome calculation, and detection of error locations must be performed in both cases.
When this error location detection is carried out in duality, not only does the number of check bits to be added increase, but error location, which is the most complicated part of error correction, must be carried out twice, which is inefficient.
As discussed above, when prior art involving a combination of an error correction code and an error detection code was used, the problem was that a processing delay was incurred because the processing had to be carried out sequentially, and with prior art in which error correction encoding was carried out in duality, the problem was that the code length increased and the complicated specification of the error location had to be carried out twice.


The present invention relates to evenly substituted polysaccharide derivatives having the general structure:

The present invention relates to new materials consisting of thermoplastic aliphatic polysaccharide carbamic acid derivatives, as well as of mixtures of such derivatives with low-molecular urea derivatives, the preparation of such derivatives and mixtures from polysaccharides or polysaccharide derivatives and aliphatic monoisocyanates in a suitable solvent. The materials according to the invention, after removal of the solvents. are preferably processed as thermoplastic material by injection moulding or extrusion. Mouldings, fibres, films, as well as foams or coatings can be produced.
It is known that thermoplastically processable materials can be produced from polysaccharides, in particular from starches or celluloses, by esterification or etherification of the free hydroxyl groups in a homogeneous reaction process (cf. Encyclopaedia of Polymer Science and Technology Vol. 3, 1985).
Thermoplastic materials are also correspondingly obtained, for example, according to EP 626 392, by esterification of polysaccharide hydroxyalkyl ethers.
JP 142938 and Macromolecules 18, 1985, 1746-1752 describe the reaction of cellulose ethers with acid chlorides or with carboxylic anhydrides.
J. Appl. Polym. Sci. 52. 1994, 755-761. and J. Env. Polym. Degr. 3, 1995, 115-118 describe the preparation of thermoplastic cellulose esters from cellulose and long-chain unsaturated fatty acids in pyridine/DMF.
The thermoplastic processability of polysaccharide derivatives is dependent on the average degree of substitution of the anhydroglucose repeat unit, referred to below as DS, which in the case of thermoplastic aliphatic cellulose ester derivatives, for example, is at least approximately 2.0.
To obtain thermoplastic processability, it is necessary to add further auxiliary substances, especially plasticisers,to these polysaccharide-derivatives (F. Mxc3xcller, Ch. Leuschke, in Becker/Braun: Kunststoff-Handbuch Vol. 3/1, Hanser Verlag, Munich, 1992).
Whereas the etherification is usually carried out by reacting alkali cellulose with epoxides such as, for example, ethylene oxide or propylene oxide, in an inert suspending medium, esterifications are usually carried out in a solvent process using acids as solvents. Here the swelling process also serves to activate the cellulose (Encyclopaedia of Polymer Science and Technology Vol. 3, 1985).
Comparably, the steady reaction of polysaccharides with substituted isocyanates or substituted isothiocyanates likewise succeeds only in the case of easy accessibility of the cellulose chains in homogeneous solution or in solvents having a very strong swelling effect.
Acta Polymerica 32, 1981, 172-176 specifies that dry cellulose does not react satisfactorily with isocyanates in the absence of solvents and further catalysts. Reactions in solvents which are not capable of at least initiating swelling in the cellulose do not produce satisfactory reactions with the cellulose (Ang. Chem., 59, 1947, 257-288).
B. Polym. J., 18, 1986. 259-262 describes the reaction of wood cellulose with alkyl monoisocyanates. The formation of urethane remains limited to the surface of the polysaccharide fibres.
DE 2358808 describes the reaction with long-chain mono- and diisocyanates, which is limited to the surface of cellulose powders.
L. Disserens, in xe2x80x9cNeueste Fortschritte und Verfahren in der chemischen Technologie der Textilfasernxe2x80x9d, Birkhxc3xa4user Verlag, Stuttgart, 1957, presents a survey of the reactions of textile fibres with mono- and diisocyanates which are limited to the surface. Long-chain alkyl isocyanates are preferably used here for the purpose of hydrophobing the textile material. GB 467 992 describes the heterogeneous reaction with isocyanates of textile fibres which have been previously reacted with alkylene oxides. In the reaction carried out in petroleum spirits, however, no significant swelling of the cellulose results.
In addition the mechanical properties of paper can be influenced by the reaction of isocyanates with the cellulose fibres (Acta Polymerica 32, 1981, 172-176). However, for this preferably multifunctional isocyanates, particularly preferably diisocyanates, are used, which are not the subject matter of the present invention.
Average degrees of conversion of cellulose with isocyanates are obtained using solvents and catalysts especially when the cellulose is in the swollen condition. This can be achieved through the use of a suitable solvent or else through the use of a derivative of the cellulose or of a polysaccharide together with a suitable solvent. The formation of the urethane bond can also be brought about here by an additional back process (Cell. Chem. Technol. 1, 1967, 23-32).
The swelling of the cellulose can be achieved by initial swelling in water and subsequent exchange for a polar aprotic solvent.
Alternatively, solvents having a strongly swelling or solvent effect on cellulose, such as DMAc, DMSO, DMAc/LiCl or DMSO/formaldehyde mixtures, can also be used directly (U.S. Pat. Nos. 4,129,451, 4,129,640, 4,097,666). Surveys of solvent systems are published in Nevell and Zeronian: Cellulose chemistry and its applications, Wiley, N.Y., 1985, Acta Polym. 36 (1985), 697-698 and Polymer News 15, (1990), 170-175.
Also described as being good swelling or dissolving systems are, for example, morpholine/piperidine mixtures (J. Appl. Polym. Sci., 22, (1978), 1243-1253, as well as amine-N-oxides (Acta Polymerica, 39, (1988), 710-714, U.S. Pat. No. 3,508,941) and metal cation/solvent systems such as Cu/NH3 or Cd/ethylenediamine (Polymer 31, (1990), 348-352).
The reaction of phenyl isocyanate with cellulose in DMSO/paraformaldehyde mixtures is described in J. AppI. Pol. Sci. 27, (1982), 673-685, J. Appl. Pol. Sci. 42, (1991), 821-827, and in Nevell and Zeronian: Cellulose chemistry and its applications, Wiley, N.Y., 1985.
High degrees of conversion are favoured especially by the addition of catalysts, by a reaction period of an appropriately chosen length or by elevated temperatures. On the other hand, the formation of isocyanurates is catalysed by means of amines in DMAc, DMSO or DMF as swelling agents or solvents (Eur. Polym. J., 26 (11), (1990), 1217-1220).
The patents and publications listed below describe the reaction of soluble cellulose acetate having degrees of substitution DS less than 3.0 with isocyanates. isocyanate prepolymers or isocyanate-functionalised polymers or oligomers in homogeneous solution. After the formation of the urethane, the acetate groups can be saponified and the urethane derivatives of the unsubstituted cellulose can be isolated.
J. Macromol. Sci. Chem. A 16 (1981) 473. Polym. Prepr. Am. Chem. Soc. Div. Poly. Chem. 20 (1979) 574, J. Poly. Sci. Polym. Lett. ed. 111 (12) (1973) 731-735, Macromol. Synth. 7, 101-105, Polymer 21 (1980) 648-650, Polym. Prepr. Am. Chem. Soc. Div. Poly. Chem. 3 (1990) 642, U.S. Pat. No. 3,950,28.
Thermoplastically processable aliphatic carbamates starting from polysaccharides or polysaccharide hydroxyalkyl ethers are not known.
The object of this invention is to identify reaction conditions for the reaction of polysaccharide derivatives. preferably those from renewable raw materials and derivatives of these, with isocyanates, such that average to high degrees of conversion are obtained. For this was required in particular a reaction under homogeneous conditions, that is. a solution of the polysaccharide derivative in the solvent, and at least a solvent having a very strong swelling effect.
Surprisingly, it has now been found that cellulose derivatives, and particularly preferably cellulose alkyl ethers which are not soluble or highly swellable in the solvents used according to the invention, pass into solution or begin to swell strongly during the reaction with alkyl monoisocyanates and consequently lead to average to high degrees of conversion.
Examples of polysaccharide components which may be mentioned in particular are hydroxypropyl cellulose and hydroxyethyl cellulose. Aprotic polar and nonpolar solvents, preferably cyclic ethers or substituted aromatics, particularly preferably dioxane and toluene, can be used as solvents in the process according to the invention.
It has also been found, surprisingly, that the products a of this process according to the invention are thermoplastically processable and especially the by-products b of the process according to the invention improve the thermoplastic processability of the products according to the invention. This surprising result of the procedure according to the invention could not have been anticipated by the person skilled in the art. The person skilled in the art had to anticipate that the by-products b would decompose during subsequent thermoplastic processing and form interfering gaseous decomposition products.
The molar ratio of the components a and b is given by the formula
0.01 less than b/(a+b) less than 0.5.
The molar ratio b/(a+b) is particularly preferably at least 0.05 and in particular 0.1 to 0.2. If the limiting value of 0.5 in the above formula is exceeded, that is, if the proportion of by-product is increased, the product no longer possesses mechanical properties which render possible its practical use.
The function according to the invention of the product b operates only if the melting temperature of B is lower than the processing temperature.
The new compounds correspond to the general structure:
polysaccharidexe2x80x94Oxe2x80x94R
wherein polysaccharide-O represents a substituted or unsubstituted polysaccharide unit and R is a substituent of a polysaccharide-OH group having either the structure
R=xe2x80x94Axe2x80x94Bxe2x80x94
or the structure
R=xe2x80x94Bxe2x80x94,
wherein A is a linear polyether chain having the following structure:
A=(xe2x80x94Dxe2x80x94Oxe2x80x94)n
wherein D denotes a linear aliphatic branched or unbranched chain having 2 to 12 C atoms, O represents an oxygen atom and n is a number equal to or greater than 1.
B represents a substituted carbamic acid having the structure
wherein E denotes a linear or branched aliphatic chain having 1 to 18 C atoms.
The invention accordingly provides thermoplastically processable urethane derivatives of polysaccharides or polysaccharide ethers which have been reacted with isocyanates or blocked isocyanates at average degrees of substitution (referred to the anhydroglucose unit) of DS equal to 0.3 to 3.0, preferably 0.6 to 2.5.
The invention also provides the mixture of the polysaccharide urethane derivatives according to the invention with low-molecular symmetrical and asymmetrical aliphatic urea derivatives, having chain lengths of 1 to 20 carbon atoms.
The invention further provides a process for the preparation of such thermoplastic polysaccharide urethanes, polysaccharide ether urethanes and mixtures of these with low-molecular urea derivatives, which is characterised in that the polysaccharide or the polysaccharide ether is introduced into a nonsolvent together with a suitable catalyst and is then converted by means of an isocyanate into the corresponding urethane, the polysaccharide urethanes or polysaccharide ether urethanes thus formed and the low-molecular urea derivative being soluble in the solvent or suspending medium used. The product can be isolated in the process according to the invention by a precipitation or by an evaporating extrusion.
For the synthesis, a cellulose derivative is refluxed in a suspending medium and, after addition of a catalyst, the isocyanate compound is added dropwise. Here it is to be regarded as surprising that the isocyanate reacts with the polysaccharide or with the polysaccharide ether in a solid-liquid two-phase reaction in standard suspending media. In suspending media such as dioxane and toluene the reaction products pass into solution during the reaction and can be isolated by distillation or precipitation in nonsolvents, for example, with water, acetone, or alkanes.
The degree of conversion of the polysaccharide derivative can be adjusted within wide limits through the stoichiometry and the progress of the reaction. In this connection a degree of substitution of greater than 0.5 is sufficient to provide a thermoplastically processable material. At normal pressure and room temperature, polysaccharides and polysaccharide derivatives may contain a small per cent by weight of water. The secondary reaction of the isocyanate compounds with water leads to the formation of by-products. among which are preferably disubstituted ureas. The extent of the formation of by-products is here highly dependent on the water content of the reaction solution. These by-products have melting temperatures  less than 200xc2x0 C. and, unless they are removed during the working-up of the polysaccharide derivatives, lead to a distinct improvement in the thermoplastic processability of the product. This outcome is surprising to the person skilled in the art and was not predictable.
Industrially available polysaccharide derivatives of any molecular weight are suitable for the synthesis.
If polysaccharide ethers and in particular cellulose ethers are used. examples of suitable cellulose ethers are methyl cellulose. ethyl cellulose or benzyl cellulose having average degrees of substitution of less than or equal to 2.5. hydroxyethyl cellulose, hydroxypropyl cellulose, dihydroxypropyl cellulose, hydroxybutyl cellulose, methylhydroxyethyl cellulose, methylhydroxypropyl cellulose, methyl-hydroxybutyl cellulose, ethylhydroxypropyl cellulose, ethylhydroxyethyl cellulose, carboxyalkyl cellulose, sulphoalkyl cellulose, cyanoethyl cellulose and mixed ethers thereof.
Suitable suspending media and solvents are ketones such as, for example, methyl ethyl ketone, ethers and cyclic ethers such as, for example, dimethoxyethane, dimethoxymethane, dimethyl ether, diethylene glycol dimethyl ether. dioxane and tetrahydrofuran, acetals, hydrocarbons and polar aprotic compounds such as dimethyl sulphoxide, dimethylformamide, dimethylacetamide, N-methylmorpholine, N-methylpyrrolidone. trialkyl phosphate, ethyl acetate as well as nonpolar aprotic solvents such as toluene. Dioxane and toluene are preferred.
Suitable isocyanate compounds are aliphatic linear and branched monoisocyanates having saturated or unsaturated alkyl chains such as, for example, methyl isocyanate, ethyl isocyanate, propyl isocyanate, isopropyl isocyanate, butyl isocyanate. pentyl isocyanate, hexyl isocyanate, heptyl isocyanate, octyl isocyanate, nonyl isocyanate, decyl isocyanate, undecyl isocyanate, dodecyl isocyanate, tetradecyl isocyanate. hexadecyl isocyanate, octadecyl isocyanate, the corresponding isothiocyanates as well as any mixtures of the above-mentioned monoisocyaniates and isothiocyanates.
Suitable catalysts for the reaction are amines, particularly sterically hindered tertiary organic amines such as trimethylamine, triethylamine, tributylamine, tetramethylene-diamine, pyridine, N,N-dimethylcyclohexyldiamine, N,N-dimethylbenzylamine, 4-pyrilidinopyridine, permethyldiethylenetriamine, 1,4-diazabicyclo[2.2.2]octane, 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5-diazabicyclo[4.3.0]non-5-ene and any mixtures thereof.
The catalysts conventional in polyurethane chemistry such as, for example, organotin compounds. are equally suitable.
During the catalysis the quantity of amine added affects the degree of derivatisation of the polysaccharide. For the reaction with the polysaccharide derivative, the amine is added in a molar ratio to the polysaccharide of from 0.01 to 3, preferably from 0.1 to 1.
The temperature of the reaction of the polysaccharide derivative with the isocyanate is 20xc2x0 C. to 150xc2x0 C., preferably 40xc2x0 C. to 130xc2x0 C., particularly preferably 50xc2x0 C. to 120xc2x0 C. The reaction times are from 0.5 to 16 hours, preferably 0.5 to 8 hours, particularly preferably 0.5 to 4 hours.
The polysaccharide ether esters obtainable by the process according to the invention are soluble or highly swellable in organic solvents such as dioxane. tetrahydrofuran, toluene, methylene chloride. chloroform.
Moreover, these compounds are thermoplastically processable after removal of the solvents and can be converted by means of the conventional processing techniques such as extrusion into, for example, injection mouldings, films or fibres.
The process according to the invention is also characterised in that by-products, particularly preferably dialkylureas, are formed during the reaction, depending on the water content of the polysaccharide component. The retention of these by-products in the product improves the thermoplastic processability of the cellulose ether urethane derivatives.
The polysaccharide derivatives and mixtures thereof with low-molecular urea derivatives according to the invention are suitable for the production of coatings, fibres, powders, films, foams and mouldings. Their properties can be varied by preparing blends of any composition with other components such as, for example, polysaccharides and polysaccharide derivatives or polyurethanes. Combination with plasticisers, fire-protecting agents, pigments and processing aids such as, for example, long-chain fatty acid amides, is also possible here. Especially the addition of plasticisers such as, for example, triethylene glycol, lactic esters or tartaric esters, improves the thermoplastic processability and renders possible processing even at low degrees of substitution such as, for example, a DS equal to 0.6.
The subject matter of the present invention is explained in more detail by means of the available Examples.

Thermoplastic material consisting of aliphatic carbamic acid derivatives of polysaccharides and low-molecular urea derivatives as well as a process for their preparation and use of the same

Abstract: wherein polysaccharidexe2x80x94O represents a substituted or unsubstituted polysaccharide unit and R is a substituent of a polysaccharide-OH group having either the structure

Abstract: or the structure

Abstract: wherein D denotes a linear aliphatic branched or unbranched chain having 2 to 12 C atoms, O represents an oxygen atom and n is a number equal to or greater than 1, and


A spool sleeve consisting of several interconnected layers formed by webs, wherein a recess in an inner layer contains an appropriately shaped transponder having a weight that is approximately equal to that of the web material removed to create the recess so that any imbalance of the sleeve with the transponder therein embedded is avoided.

The invention concerns a spool sleeve of the type known, for example, from the EP 0.170.094 B2 (Wibmer), where wound webs are glued together.
With such sleeves, a barcode along with written text beside it is applied to the rim of the sleeve on both sides during the manufacture of the sleeve. This multi-digit barcode serves to identify the sleeve and contains the production data of the material spooled on this sleeve. It frequently happens that these optical markings are covered by a layer of dirt or are damaged during the repeated use of the sleeve so that they can no longer be read by the human eye or by a barcode scanner. In that case, the sleeve needs to be replaced by a new one even though it would be sound enough to be reused many more times.
From CH 686.156 A5, a data carrier for material identification and for the transportation of data along with the material in the textile industry was previously known. In the case of a spool sleeve for yarn as material, this machine-readable data carrier is an integrated circuit, i.e. a chip with an antenna embedded in the sleeve wall in order to avoid damage during use of the sleeve. Here, however, the sleeve does not consist of a spool made up of multiple layers of which one contains a recess for embedding the transponder, and also does not provide for imbalance compensation.
It is the objective of the invention to avoid the aforesaid disadvantage and to create a sleeve of the above-mentioned type which can be used ten times as often while still allowing the marking of the sleeve itself and thus making it possible to identify the sleeve with the help of these markings.
The invention solves this problem in a spool sleeve, specifically for spooling glass fibers; with several interconnected layers, specifically layers glued to each other, consisting specifically of webs made of fleece, plastic film, or fabric-reinforced rubber, by the provision of an inner layer that has a recess into which an appropriately shaped transponder is embedded, whose weight is approximately equal to the weight of the web piece that was cut out. The transponder (microelectronic data carrier) for identifying the sleeve by means of individual data stored in the transponder which can be read with hand-held or stationary electronic reading devices does not require an unobstructed path between the sleeve surface and the eye (in case of numbers) or the sleeve surface and the scanner (in case of barcodes). This means that it can be placed below the surface of the sleeve, especially since the signal between the transponder and the reading device is transmitted by means of radio transmission, with the transponder being powered not by a battery but by the electromagnetic field of the reading device.
As a consequence, the identifying data of the sleeve that are stored in the transponder and are transmitted to the reading device upon demand are not subject to any wear even during frequent use of the sleeve so that the strength of the sleeve material alone determines the length of its useful life.
Suitable design variants of the sleeve proposed by the invention are characterized by:
the feature that the transponder consists of a microchip and a ring coil serving as an antenna surrounding the chip, with the chip and the coil arranged on the same plane; and that this relative position of the chip and the coil is secured by an electromagnetically passive film on which at least the chip and the connecting wires to the coil are located;
a double film in form of a shallow pocket whose edges are vacuum sealed and which also encloses the coil;
the feature that the film pocket is held by means of a strip of its edge in the web recess; and
by the feature that the layer with the recess is one of the center layers, and that the recess is centered between its edges.
The invention is suitable for sleeves of the type known from EP 0.170.094 B2, where fleece, plastic film, or fabric-reinforced rubber are used as web materials.
Either read-only memory (ROM) or random access memory (RAM) may be used as the transponder memory for the individual identification of the sleeve. The latter allows changes of the identification data.
Below, the invention is explained in detail with the help of a design variant of the sleeve as proposed by the invention, shown in exemplary fashion in the drawing.

Spool-collar with transponder especially for spin-spooling of glass fibers

Wibmer GmbH u. Co. Kommanditgesellschaft Papier-Formtechnik


A motor vehicle has a drive combustion engine and a power supply system for supplying electric consuming devices on-board the motor vehicle. The power supply system includes a fuel cell system and a battery coupled to the fuel cell system. The energy and/or material currents of the drive combustion engine and the fuel cell system are coupled together.

This application claims the priority of German Patent Document DE 100 54 007.4, filed Nov. 1, 2000, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a motor vehicle with a drive combustion engine and a power supply system.
The electric power, available for the electric consuming devices on-board a motor vehicle, is based in particular on the size and capacity of the electric generator, which usually exhibits a power output ranging from 1.5 to 2.5 kW. Thus, some electric consuming devices can be operated only when the internal combustion engine is on.
DE 197 03 171 A1 discloses a motor vehicle that is driven by a drive combustion engine and which contains a fuel cell system as the current generator (APU auxiliary power unit). This system supplies the electric consuming devices in the motor vehicle with energy and can be activated independently of running the internal combustion engine. The fuel cell system also supplies the drive combustion engine with electric energy. A battery is connected to the fuel cell system to release current as soon as the combustion engine is started and covers brief peak loads. Thus, the fuel cell system, comprising fuel cells and gas generating system, and the battery form a hybrid system to supply electric energy.
An object of the present invention is to improve a motor vehicle of the generally known type such that an economical, compact and efficient integration of a hybrid system comprising fuel cells-APU and battery can be achieved.
This object has been by way of a motor vehicle in which the energy and/or material currents of the engine and fuel cell system are coupled together. The terms xe2x80x9cAPUxe2x80x9d and fuel cell system are used synonymously in the following description.
In particular, the following advantages are now obtainable with the present invention:
improved efficiency;
fuel savings;
use of common modules is possible;
lower overall height;
cost reduction;
reduced the start time of the gas generating system in the fuel cell system and the exhaust gas catalyst in the exhaust gas stream of the combustion engine;
reduction in emissions, in particular the starting emission.
In an advantageous currently contemplated embodiment of the present invention, the drive combustion engine and the fuel cell system are disposed in a common cooling circuit. The result is a compact configuration because there is no need for separate cooling systems for the internal combustion engine and the fuel cell system. If necessary, the cooler that is used can be enlarged compared to the conventional cooler for a motor vehicle.
The lines to transport the coolant in the cooling system are coupled advantageously from a thermal view point to the body of the motor vehicle. The lines can run inside or outside the body, for example, in the area of the door sill. The line length between the APU (for example, placed in the rear of the motor vehicle) and the cooler (for example, placed in the front of the motor vehicle) can be used advantageously as the cooling distance. The lines can be disposed, in particular, in continuous cavities through the body of the motor vehicle, thus economizing on cost intensive fastening material on the bottom side of the motor vehicle. The APU and internal combustion engine can resort to peak cooling capacities at different operating points because the engine needs the peak cooling capacity in drive mode and the APU needs it when the vehicle is standing still.
When air conditioning the interior of the motor vehicle in standing mode, the APU can be started, with the drive combustion engine off, to generate electric energy to cool the passenger interior. At low outside temperatures, the motor vehicle can be preheated by starting the gas generating system of the APU. To this end, it is unnecessary to start up the entire fuel cell system. The requisite electric energy can be taken from the battery. Thermal energy can be obtained by burning fuel.
In another advantageous configuration of the present invention, the gas generating system of the fuel cell system is coupled thermally with the exhaust gas line of the drive combustion engine. Thus, should the APU not be used when the drive combustion engine is running, the APU can be held at the appropriate operating temperature by dissipated engine heat. Thus, if necessary, the APU can be started significantly faster. On the other hand, in the start phase of the motor vehicle the APU can preheat the exhaust gas catalyst of the engine, thus reducing the exhaust gas emission at startup because the starting temperature of the catalyst is reached faster. It is also contemplated, however that the APU will preheat the drive combustion engine by way of the cooling water when the motor vehicle is in standing mode. Thus, the start comfort is improved and the service life of the engine is extended.
Another contemplated arrangement for reducing the exhaust gas emission, in particular to reduce nitrogen oxides, is to meter hydrogen from the gas generating system into the exhaust gas stream.
In yet another advantageous embodiment of the present invention, in addition to the drive combustion engine, there is an electric motor which, in support of or as an alternative to the drive combustion engine, guarantees the drive of the vehicle. In case of engine damage, the APU can be switched such that, for example, it serves as the drive aggregate for the electric motor. The electric motor can be, for example, the crank or starter of the motor vehicle or a generator. Thus, the motor vehicle can be driven without external assistance to the closest repairshop. The results are advantages for off-road operation of the motor vehicle and with respect to safety in sparsely populated areas.
The additional electric motor has other advantages such as, for example, when motor vehicles are prohibited from driving due to smog. Then the motor vehicle can be operated with the combustion engine turned off, whereby the electric motor serves as the main drive of the motor vehicle. Furthermore, the electric motor can be used as the main drive, for example, in congested traffic or in city traffic (stop-and-go traffic). There are also additional advantages with respect to fuel savings.
It is also possible with the present invention to reduce a motor vehicle""s susceptibility to breakdowns with respect to the electrical supply. Thus, for example, the battery can be charged automatically by the protection circuit after prolonged periods of idling or in the case of leak current without having to start the engine and without the presence of the driver. Furthermore, the cooling water can be monitored by a sensor and, if necessary, heated so that in the winter, for example, frost damage to the cooler can be avoided.
Other advantages resulting from the integration of a hybrid system comprising a fuel cell system and battery into a motor vehicle occur at peak load on the system in the start phase, during which the use of the battery is quite conservative. In this respect one also speaks about peak shaving. Another advantage is the faster availability of larger quantities of electric energy.
In addition, the dynamics of the APU is improved during vehicle operation. The results are advantageous with respect to the service life of the APU and the drive combustion engine. To save fuel, the drive combustion engine can be turned off, for example, when driving downhill. The APU takes over the task of supplying, for example, the brake booster and the power steering with electrical power for safer driving.
In addition, the battery is discharged so as to conserve the battery when the motor vehicle is in standing mode and, at the same time, the electric consuming devices are operating, but not to the point of exhaustive discharge. Thus, it is now possible, for example, to integrate a plug with 220 V on board the motor vehicle. In addition, the energy of the battery can be used over a prolonged period of time.
To realize such a hybrid system, one can resort to the starter battery, which is already present in conventional motor vehicles. This starter battery is quite appropriate with respect to power and capacity to form together with the APU a hybrid system.
To optimize the water management of the APU, the liquid water, accumulated in the air conditioning system of the motor vehicle, can be used. This liquid water can be used, for example, to cool the fuel cell system or to moisten the gases, generated in the gas generating system. At high outside temperatures, more liquid water is accumulated owing to the operation of the air conditioning system, thus facilitating the APU management with respect to cooling capacity and water management, which is rendered more difficult during these operating conditions (high outside temperature).
Furthermore, when the engine is turned off, a larger number of electric consuming devices can be supplied with electric power than is possible in the state of the art. In addition, mechanically driven parts can be driven electrically (i.e. xe2x80x9cbeltless motorxe2x80x9d).

Motor vehicle with a drive combustion engine


In an implementation, an appearance of lens is displayed on a display device for a selected region of an image to magnify the selected region of the image in comparison with a portion of the image outside of the appearance of the lens. A zoomed-in view of the image is displayed on the display device by increasing magnification of the portion of the image outside the appearance of the lens successively as an animation until the magnification of the portion of the image outside of the appearance of the lens corresponds with the magnification of the selected region of the image within the appearance of the lens, at which point the appearance of the lens is no longer displayed.

Computer graphics systems are typically used to examine and perform operations on large, detailed, digital images. Examples of such tasks include an artist editing a high-resolution image for print publication, an image analyst examining an aerial photograph, and a silicon chip designer examining chip layouts. Often, users of such graphics systems may desire to zoom-in to specific regions of a particular image in order to recognize detail. When zoomed-in to a specific region of interest, the entire image may not fit on the display screen of the system and hence a large portion of the image may no longer be visible to the user. If the user, still zoomed-in, wants to navigate to a different region of the image, the user typically first zoom-outs and then zooms back in, or pans repeatedly until the new region of interest is located. Both of these operations are slow and time consuming. Thus, conventional methods of navigating large images such as panning and zooming may be inefficient. This is an example of what has been referred to as the "screen real estate problem".
U.S. Pat. No. 6,271,854 to Light discloses a method for navigating in three-dimensional graphic scenes. In Light, a user may zoom-in to an object in a scene by clicking on the object. To zoom-out to the original scene, an "opportunistic" control icon is provided. By clicking on this control, the original scene is redisplayed. The user may then select another object in the original scene to zoom-in on. However, the screen real estate problem remains evident in Light. When viewing an object which has been zoomed-in, the relationship between that object and other objects in the original scene may be lost to the user.

Navigating digital images using detail-in-context lenses