A polymer of a ring-opened functionalized epoxide is formed by the polymerization of a functionalized epoxide monomer having the structure E-CHR-G wherein E represents an epoxide group, R is hydrogen or an alkyl group, and G is a derivatizable group such as an unsaturated functionality or ester substituent.

1. Field of the Invention
The present invention relates to the synthesis of degradable polymers. More particularly, the present invention relates to degradable polymers having increased functionality.
2. Related Art
Interest in the synthesis of new degradable polymers has expanded in recent years. This increased interest stems in part from the concern that the extensive and continuing use of polymers in today""s society will result in environmental damage. The concern is that many polymers used in commercial applications are inert and thus able to withstand natural processes that cause other non-inert materials to disintegrate and decompose. As a result of this inertness, polymers have accumulated in landfills and thereby have contributed to the shortage of landfill space generally. This problem will only be exacerbated as polymers are used in more and more commercial products and services. Thus, there is a need for developing polymers for commercial applications that have an enhanced ability to degrade.
The increased interest in the synthesis of new degradable polymers also stems in part from the use of synthetic polymers in medical applications. In medical applications, not only must the polymer be able to degrade, but the degradation products also must be compatible with the human body, i.e., be nontoxic. In this situation, the polymers are termed biodegradable, indicating their ability to degrade due to biological processes occurring inside the human body. As early as the 1960s, synthetic polymers were used in the field of surgical medicine as suture material. The polymeric suture material was both biodegradable and absorbable, that is, the polymers decomposed after a period of time after implantation in the human body, and those decomposition products were absorbed by the human body without any adverse or toxic effects. The advantage of biodegradable polymer-based suture materials is the ability to fabricate fibers with varying absorption rates to match the healing profiles of the tissues they help to repair. Another advantage of such polymer-based sutures over traditional silk and gut sutures is enhanced versatility and low tissue reactivity.
In addition to use as suture material, degradable polymers have been used in other biomedical applications, such as polymer-based drug delivery systems. In such a system, degradable polymers are used as a matrix for the controlled or sustained delivery or release of biologically active agents, such as, drugs, to the human body. In addition, the development of endoscopic surgical techniques has resulted in the need for developing such degradable drug delivery systems wherein the placement of the drug delivery device is targeted for specific anatomical locations. Examples of such polymer-based drug delivery systems are described in the following U.S. patents: U.S. Pat. No. 6,183,781, entitled xe2x80x9cMethod for Fabricating Polymer-based Controlled-release Devicesxe2x80x9d; U.S. Pat. No. 6,110,503, entitled xe2x80x9cPreparation of Biodegradable, Biocompatible Microparticles Containing a Biologically Active Agentxe2x80x9d; U.S. Pat. No. 5,989,463, entitled xe2x80x9cMethods for Fabricating Polymer-based Controlled-release Devicesxe2x80x9d; U.S. Pat. No. 5,916,598, entitled xe2x80x9cPreparation of Biodegradable, Biocompatible Microparticles Containing a Biologically Active Agentxe2x80x9d; U.S. Pat. No. 5,817,343, entitled xe2x80x9cMethod for Fabricating Polymer-based Controlled-release Devicesxe2x80x9d; U.S. Pat. No. 5,650,173, entitled xe2x80x9cPreparation of Biodegradable, Biocompatible Microparticles Containing a Biologically Active Agent.xe2x80x9d Other examples of polymer-based drug delivery systems are described in U.S. Pat. No. 5,922,253, entitled xe2x80x9cProduction Scale Method of Forming Microparticlesxe2x80x9d and U.S. Pat. No. 5,019,400, entitled xe2x80x9cVery Low Temperature Casting of Controlled Release Microspheres,xe2x80x9d the technology described therein also known as Prolease(copyright). All of the above-identified patent applications are assigned to Alkermes Controlled Therapeutics, Inc. of Cambridge, Mass., and are incorporated herein by reference.
Degradable polymers have also been used in other biomedical applications, including use as polymer scaffolds for tissue engineering. In this biomedical application, porous polymer scaffolds are shaped into articles for tissue engineering and tissue guided regeneration and repair applications, including reconstructive surgery. Scaffold applications include the regeneration of tissues such as nervous, musculoskeletal, cartilaginous, tendenous, hepatic, pancreatic, ocular, integumentary, arteriovenous, urinary or any other tissue forming solid or hollow organs. Scaffolds have been used as materials for vascular grafts, ligament reconstruction, adhesion prevention and organ regeneration. In one embodiment, the polymer scaffold provides physical support and an adhesive substrate for isolated cells during in vitro culturing and subsequent in vivo implantation in the human body. An alternate use of degradable polymer scaffolds is to implant the scaffold directly into the body without prior culturing of cells onto the scaffold in vivo. Once implanted, cells from the surrounding living tissue attach to the scaffold and migrate into it, forming functional tissue within the interior of the scaffold. Regardless of whether the scaffold is populated with cells before or after implantation, the scaffold is designed so that as the need for physical support of the cells and tissue diminishes over time, the scaffold will degrade. Degradable polymer scaffolds are described, for example, in U.S. Pat. No. 6,103,255, entitled xe2x80x9cPorous polymer scaffolds for tissue engineering,xe2x80x9d and is incorporated herein by reference.
Additional biomedical applications for synthetic biodegradable polymers include use with fracture fixation, for example, as absorbable orthopedic fixation devices. In particular, such biodegradable polymers permit treatment of bone fractures through fixation, providing good tissue/material compatibility, and facile molding (into potentially complex shapes) for easy placement. Controlled degradation of the polymers permits optimum bone function upon healing. The materials can reestablish the mechanical integrity of the bone and subsequently degrade to allow new bone formation to bear load and remodel. These biodegradable polymers maintain mechanical integrity while undergoing a gradual degradation and loss in size permitting bone ingrowth. In contrast to the traditional use of steel fixation devices, the degradable polymer-based device is advantageous in those situations where the device is not needed permanently or would require removal at a later point in time. Also, metallic orthopedic devices shield stress during healing and can lead to bone atrophy. Polymers for use in such orthopedic applications are described in U.S. Pat. No. 5,902,599, entitled xe2x80x9cBiodegradable Polymer Networks for Use in Orthopedic and Dental Applications,xe2x80x9d and U.S. Pat. No. 5,837,752, entitled xe2x80x9cSemi-Interpenetrating Polymer Networks,xe2x80x9d both of which are incorporated herein by reference. U.S. Pat. No. 5,902,599 also describes synthetic biodegradable polymers for use in dental applications.
The wide variety of commercial and biomedical applications just described for synthetic degradable polymers demonstrates the need for the development of multiple types of polymers with varying degradability profiles.
Synthetic polymers for use in commercial applications are legion. For example, polyethylene, polypropylene, and polystyrene are commercially produced polymers wherein monomer units of ethylene, propylene, and styrene, respectively, are sequentially added to a growing polymer chain by a process known as addition polymerization. The incorporation of monomer units into the polymer continues until the polymerization process is terminated by the addition of a compound that reacts with the end of the polymer chain and which itself is incapable of polymerization, thus quenching the polymerization.
Dacron is a commercial polyester synthesized by the condensation polymerization reaction of dimethyl terephthalate and ethylene glycol. With condensation polymerization, monomers are heated together in order to combine or condense them, forming a polymer. In addition to the formation of the polymer, a small organic by-product is also formed and is known as an elimination by-product. To form Dacron, the dimethyl terephthalate condenses with the ethylene glycol to form the polyester polymer and methanol as the elimination by-product.
A drawback to these mechanisms of generating commercial polymers is the reaction conditions under which polymerization occurs. Typically, high temperatures and pressures are required in order to induce polymerization. Because such severe conditions are required, only monomers that are able to withstand those temperatures and pressures can be used. Such monomers generally possess limited functionality, for under the severe reaction conditions, any functionality present on the monomer in the form of substituents would most likely be eliminated or cleaved from the monomer and/or the polymer. These restrictions on incorporating functionality into polymer systems have limited the ability to synthesize polymers with certain desirable properties, such as degradability generally, and biodegradability specifically. The latter is important if the polymer is to have medical applications as discussed above.
Of course catalysts are known to be used in polymerization reactions in order to avoid the high polymerization temperatures and pressures described above. A catalyst is used to facilitate polymerization by lowering the energy barrier that reacting monomers must overcome in order to initiate polymerization. The catalyst is often a metal or organometallic compound, which reacts with the monomers, but is not itself incorporated into the final polymer structure. But while catalysts can improve polymerization reaction conditions, catalysts cannot by themselves solve the problem of increasing functionality in the resulting polymer, particularly if the monomers themselves are incapable of supporting functionality themselves. Thus, a need remains for an acceptable method of synthesizing functionalized polymers under mild conditions with desirable characteristics such as enhanced degradability.
Synthetic degradable absorbable polymers already developed to date for use in biomedical applications include, for example, poly(p-dioxanone), which is an alternating ether-ester polymer, and its copolymers; polycaprolactone; polyhydroxyalkanoates; poly(propylene fumarate); poly(ortho esters); other polyesters including poly(block-ether esters), poly(ester amides), poly(ester urethanes), polyphosphonate esters, and polyphosphoesters; polyanhydrides; polyphosphazenes; poly(alkylcyanoacrylates); and polyacrylic acids, polyacrylamides, and their hydrogels. These synthetic absorbable polymers are discussed in detail in Handbook of Biodegradable Polymers, edited by Domb, Kost, and Wiseman (Harwood Academic Pub. 1997), incorporated herein by reference. Specifically, chapter 6 discusses poly(ortho esters) and chapter 7 discusses other functionalized polyesters. However, the ability to incorporate functionality into the polyester is limited by the low reactivity of the functionalized monomers. Using as an example monomeric precursors for poly(ester amides), it is known that functionalized morpholine-2,5-diones, known as depsipeptides, can be synthesized by the condensation of xcex1-hydroxy acid with an xcex1-amino acid. These derivatized depsipeptides can be copolymerized with lactones; however, less than 1% of the functionalized depsipeptide monomers are incorporated into the resulting copolymer. Thus, there is a need for new synthetic routes to functionalized polyester polymers.
In addition, synthetic polymers based on the polymerization of caprolactone, lactic acid, and glycolic acid have become mainstays in the field of degradable polymers, in particular the field of degradable polyesters, and are available commercially. Caprolactone is the cyclic ester derivative of caproic acid, CH3(CH2)4CO2H, and can be ring-opened to form the polyester poly(caprolactone), xe2x80x94[(CH2)5CO2]xe2x80x94. It should be noted that caprolactone has two structural isomers, designated xcex5 and xcex4 caprolactone. Any discussion of caprolactone generally applies to both forms, unless specifically noted. Lactic acid- and glycolic acid-based polymers with high molecular weights are not obtained through direct condensation of the corresponding carboxylic acid due to reversibility of the condensation reaction, backbiting reactions, and the high degree of conversion required. Rather, lactic acid- and glycolic acid-based polymers are typically obtained by ring-opening polymerization of the corresponding diester dimers, lactide and glycolide, respectively, themselves. Alternatively, the reaction can be carried out as a condensation of lactic and glycolic acid. The resulting polymers of these polymerization reactions are poly(lactic acid), also referred to as poly(lactide), abbreviated PLA and poly(glycolic acid), also referred to as poly(glycolide), abbreviated PGA. Copolymers incorporating both monomers are also available and are termed poly(lactide-co-glycolides) abbreviated PLGA and poly(glycolide-co-lactides) abbreviated PGLA, or collectively PLGs. U.S. Pat. No. 5,650,173, incorporated herein by reference, describes examples of these commercially available polymers and copolymers based on lactic acid and glycolic acid. It should be noted that lactide has two structural isomers, denoted D and L. Any discussion of lactide generally is referring to a racemic mixture of both isomers, i.e., d,1-lactide, unless specifically noted.
In addition to the polymers based solely on caprolactone, lactic acid and glycolic acid, degradable polymers can be synthesized in which additional monomer units are incorporated into the backbone of poly(caprolactone), PLA, PGA, or PLGs. In particular, copolymerization with preformed polymers having a hydrophilic segment can be used. Such hydrophilic segments include any number of segments based on diol- or glycol-containing linkages, for example, polyethylene glycol (PEG), also known as polyethylene oxide (PEO), polypropylene oxide (PPO), and pluronics. The resulting copolymers, thus include lactide and/or glycolide monomer units along with the polyether hydrophilic core initiating segment as a single block in the backbone of the polymer. For example, a PEG with molecular weight of 600 would consist of a block of at least 13 monomer units. Other polymers have multiple large segments or blocks of PEG alternating with blocks of a polyester. For example, Polyactive(copyright), is a copolymer that has large blocks of PEG alternating with blocks of poly(butylene terephthalate).
All of these polymers and copolymers derived from caprolactone, lactic and glycolic acid, with or without additional hydrophilic segments, contain ester linkages in the backbone of the polymer chain. The presence of this ester linkage provides the necessary functionality to permit degradability, particularly biodegradability. As opposed to other linkages, such as amides, which require severe conditions in order to decompose, the ester linkage undergoes hydrolysis under even mildly basic conditions such as those found in vivo. In contrast, the amide linkage requires more stringent conditions and is not easily hydrolyzed even under strongly acidic or basic conditions. In vivo, the only available route for cleavage of an amide bond is enzymatic, and that cleavage is often specific to the amino acid sequence. The highly crystalline nature of polyamides, e.g., nylon, further slows degradation by preventing or blocking access to the amide bond by water molecules and enzymes.
However, all of these polyester polymer formulations just described for biomedical applications suffer from a number of disadvantages. It is true that polymerizations involving ring-opening polymerization of caprolactone, lactide, and glycolide occur under milder conditions compared to the industrial, commercial polymerizations of ethylene, propylene, styrene, and dimethyl terephthalate. Nevertheless, like those commercially generated polymers, polymers generated by ring-opening polymerization of caprolactone, lactide, and glycolide lack the ability to support a wide variety of structural functionality, which in turn restricts their functional versatility. This is because the cyclic ester caprolactone and the dimeric cyclic esters, lactide and glycolide, themselves are incapable of supporting a wide variety of functionality, thus precluding incorporation of such functionality into the polyester polymer, even though the polymerization occurs under relatively mild conditions.
The synthesis of functionalized polymers is the key to the development of a new generation of degradable polymers for commercial and biomedical applications. The ability to incorporate more varied structural features into the polymer permits increased functionality and uses for the polymer in a wider variety of applications. As the above discussion demonstrated in the context of biomedical applications, degradable polymers are presently used for matrices for delivery of bioactive substances, for use as scaffolding in tissue engineering, for use as sutures, for fracture fixation, in dental applications, as sealants, as well as in other applications. However, the full potential of this family of polymers based on cyclic ester monomers cannot be realized given the restrictions on incorporation of structural functionality into the polymer.
Control over functionality will also permit greater control over polymer degradation. Biodegradability, as well as biocompatibility, of polymers are important characteristics if the polymer is to be used for biomedical applications as discussed above. The creation of polymers in today""s society and the exponential use in all areas of society has also created environmental concerns over whether such polymers will degrade or will end up in landfills forever. Biodegradability of polyester polymers depends on the ability of the ester linkage in the polymer backbone to hydrolyze, that is, to decompose in the presence of water. The ability of that linkage to hydrolyze, and the time frame over which such decomposition occurs, is influenced by the surrounding substituents. Thus, control over the functionality introduced into the polymer through selection of appropriate substituted monomers will greatly affect the ability to control the degradation of the polymer.
Incorporation of functionality also allows greater processing options for use in various applications. Being able to control what types of substituted monomers can be incorporated into the polymer allows control over the physical characteristics of the resulting polymer. Those physical characteristics are important in determining the consistency of the polymer and what types of processing steps the polymer can withstand. This in turn will determine to what applications particular polymers will be most suited.
For example, including functionality attached to the polymer backbone that can be crosslinked, such as through photocuring, radiation, or by chemical means, will produce polymers with the desirable physical characteristics of having high mechanical strength while having a low molecular weight. Examples of such cross-linkable polymeric systems are the following: U.S. Pat. No. 5,626,863, issued to Hubbell et al., entitled xe2x80x9cPhotopolymerizable Biodegradable Hydrogels as Tissue Contacting materials and Controlled-Release Carriersxe2x80x9d; U.S. Pat. No. 5,844,016, issued to Sawhney et al., entitled xe2x80x9cRedox and Photoinitiator Priming for Improved Adherence of Gels to Substratesxe2x80x9d; U.S. Pat. No. 6,051,248, issued to Sawhney et al., entitled xe2x80x9cCompliant xe2x80x9cTissue Sealantsxe2x80x9d; U.S. Pat. No. 6,153, 211, issued to Hubbell et al., entitled xe2x80x9cBiodegradable Macromers for the Controlled Release of Biologically Active Substancesxe2x80x9d; U.S. Pat. No. 6,201,065, issued to Pathak et al., entitled xe2x80x9cMultiblock Biodegradable Hydrogels for Drug Delivery and Tissue Treatment.xe2x80x9d All of the aforementioned patents are incorporated herein by reference.
As another example, control over the functionality also permits design of polymers capable of undergoing phase transitions when in contact with physiological conditions. One type of such polymers is a liquid at room temperature but gel at body temperatures, i.e., so-called thermoresponsive polymers, which enhances ease of injection of the polymer into a human or animal body. Such polymer systems are discussed, for example, in U.S. Pat. No. 5,702,717, issued to Cha, et al., entitled xe2x80x9cThermosensitive Biodegradable Polymers Based on Poly(Ether-Ester) Block Copolymers,xe2x80x9d and U.S. Pat. No. 6,004,573, issued to Rathi et al., entitled xe2x80x9cBiodegradable Low Molecular Weight Triblock Poly(Lactide-Co-Glycolide) Polyethylene Glycol Copolymers Having Reverse Thermal Gelation Properties,xe2x80x9d both of which are incorporated herein by reference. A second type of polymer capable of undergoing such phase transitions involves injection of polymer dissolved in a solvent, which after introduction into the body, the solvent is replaced by water, resulting in solidification of the polymer. Such polymer systems are exemplified by U.S. Pat. No. 5,968,542, issued to Tipton, entitled xe2x80x9cHigh Viscosity Liquid Controlled Delivery System as a Devicexe2x80x9d; U.S. Pat. No. 6,143,314, issued to Chandrashekar et al., entitled xe2x80x9cControlled Release Liquid Delivery Compositions with Low Initial Drug Burstxe2x80x9d; and U.S. Pat. No. 5,340,849, issued to Dunn et al., entitled xe2x80x9cBiodegradable In-Situ Forming Implants and Methods for Producing the Same,xe2x80x9d all three patents incorporated herein by reference. An additional example of the benefits of control over the functionality and hence the physical properties of the polymer is the ability to have greater control over the diffusion or penetration of water into the polymer. This permits control over the degree of bulk versus surface erosion of the polymer, which is controlled in part by the hydrophilic-lipophilic balance (HLB) in a system.
Attempts have been made to incorporate epoxides into various polymer systems. Epoxides are known to undergo ring-opening polymerization, a process which takes advantage of the fact that cyclic monomers inherently have associated ring strain, which is inversely proportional to the size of the ring. The greater the ring strain, the less energy required to open the ring, and the milder the reaction conditions necessary to achieve polymerization. However, even though the ring-strain associated with epoxides facilitates ring-opening, epoxides require basic conditions in the presence of a solvent in order to effect polymerization. Any functionality on the epoxide will be removed as a result of exposure to the basic solvent system. Also, polymerization under these conditions does not permit control over the polymerization itself due to random hydrolysis of chemical bonds. Thus, even though epoxides may be functionalized with various substituents, polymerization under mild conditions to maintain that functionality in the resulting polymer remains elusive.
One example of using epoxides to produce copolymers is described in U.S. Pat. No. 4,195,167, issued to Knopf et al., entitled xe2x80x9cGradient Polymers of Two or More Cyclic, Organic, Ring-Opening, Addition Polymerizable Monomers and Methods for Making Same.xe2x80x9d This patent describes the formation of copolymers of ethylene oxide and propylene oxide using a basic catalyst, e.g., potassium hydroxide, at temperatures above 100xc2x0 C.
Another example of using epoxides to produce copolymers is described in U.S. Pat. No. 6,221,977, issued to Park et al., entitled xe2x80x9cBiodegradable Aliphatic Polyester Grafted with Polyether and a Process for Preparing the Same.xe2x80x9d This patent describes the formation of grafted polymers wherein an epoxide, i.e., epichlorohydrin, is reacted with polyethyleneglycolmethylether (PEGME), to form an epoxide substituted with a polyether linkage. That substituted epoxide is then reacted with an ester to form a polyester polymer grafted to a side chain composed of PEGME through an ether linkage.
Another example involving epoxides to produce copolymers is described in an article by Jeong et al., entitled xe2x80x9cThermogelling Biodegradable Polymers with Hydrophilic Backbones: PEG-g-PLGA,xe2x80x9d in Macromolecules, 2000, 33, 8317-22. That article describes the sequential synthesis of a copolymer using preformed PEG in the backbone grafted to side chains derived from lactide and glycolide.
Another example where epoxides have been used to form copolymers is described in U.S. Pat. No. 5,359,026, issued to Gruber, entitled xe2x80x9cPoly(Lactide) Copolymer and Process for Manufacture Thereof.xe2x80x9d That patent describes copolymerization of lactide with an epoxidized fat or oil, e.g., linseed oil, for the purpose of forming copolymers with improved processing properties. However, the epoxides disclosed in that patent are not functionalized. Moreover, those epoxides are actually multiple epoxides (polyepoxides), rather than monomeric epoxides, when reacted with lactide, requiring temperatures in excess of 180xc2x0 C.
Because at present synthesis of polymers with particular functionality is limited as a result of the conditions under which polymerization occurs and/or as a result of the limited structural functionalization possible of the reactant monomers themselves, there is a need in the art to develop synthetic methods to create polymers with a wider variety of structural functionalization. There is a further need in the art to synthesize such polymers so as to enhance the ability to control the degradation of the polymers in commercial and biomedical applications.
The present invention, the description of which is fully set forth below, solves the need in the art for development of such functionalized, degradable polymers.
The present invention provides for the synthesis of various functionalized polymers. The functionalized polymers are synthesized through the process of ring-opening polymerization. Polymerization occurs under mild conditions. The functionalization of the polymers permits control over certain properties of the polymers, in particular, the degradation of the polymers.
In one embodiment of the invention, functionalized epoxides are synthesized for use as monomers in polymerization reactions. These functionalized epoxide monomers can be viewed as having the structure Exe2x80x94CHRxe2x80x94G. In this structural representation, E represents the epoxide moiety itself, i.e.,
the three-membered cyclic ether structure typical of epoxides. R represents hydrogen or any alkyl group. G represents a derivatizable group. The derivatizable group can contain any functional group capable of bonding to the (Exe2x80x94CHR)xe2x80x94 moiety and can contain a wide variety of functionality. Such derivatizable groups can include a degradable moiety, i.e., one that is susceptible to decomposition under appropriate conditions, such as neutral, acid, or base hydrolysis.
In a further embodiment of the invention, the above-described functionalized epoxides are polymerized by ring-opening polymerization. The ring-opening polymerization occurs under mild conditions using an initiating system. The initiating system of the present invention includes any system capable of ring-opening polymerization.
The homopolymer resulting from the ring-opening polymerization of the functionalized epoxides is comprised of repeating ethoxy ether units, i.e., the ring-opened
epoxide moiety, with the functionalized side chain of the original functionalized epoxide, i.e., the derivatizable group G, appended to one of the carbon atoms of each of the repeating ethoxy ether units. Because use of the initiating systems of the present invention permits polymerization under mild conditions, the side chain can support a wide variety of structural functionalization, as noted above in the discussion of the synthesis of the functionalized monomer units. The present invention contemplates such homopolymers containing side chains linked to the backbone of the polymer through a degradable linkage.
In addition to the above-described synthesis of functionalized epoxides before subsequent polymerization to form a homopolymer, the present invention contemplates functionalizing the side chain of the epoxide after the epoxide has been ring-opened and the polymer formed. In this sense, the epoxide is functionalizable or derivatizable, rather than already functionalized or derivatized.
In still another embodiment of the invention, ring-opening polymerization is used to copolymerize the above-described functionalized epoxides with cyclic esters. The ring-opening polymerization occurs under mild conditions, using an initiating system. The initiating systems that can be used for these copolymerization reactions are the same as those described above for the homopolymerization reactions. Preferably, the initiating system comprises an organotin catalyst and an alcohol-containing species. The resulting copolymer is comprised of both the ring-opened functionalized epoxide, in the form of ethoxy ether units, and the ring-opened cyclic ester, in the form of ester units. The functionality of the epoxide monomer can be as described above. The present invention contemplates copolymers containing side chains linked to the backbone of the copolymer through a degradable linkage. The ethoxy ether units are randomly distributed throughout the polyester polymer backbone. A random distribution of ethoxy ether units in the backbone means that there are no large regions of exclusively either polyester units or polyethoxy ether units that would otherwise impart dominant physical characteristics, e.g., hydrophilicity or hydrophobicity, on a microscopic level. Rather, the ethoxy ether units are incorporated proportionally into the polymer backbone based on the amount of functionalized epoxide in the feed initially. Stated another way, no regions containing exclusively sequential ethoxy ether units are present in the backbones of the polymers of the present invention, such that an ethoxy ether unit is repeated no more than 10 times, preferably no more than 7 times, more preferably no more than 6 times, and most preferably no more than 5 times The cyclic ester monomer can be any cyclic ester susceptible to ring-opening polymerization. Preferably, the cyclic ester is either lactide, glycolide, caprolactone, 1,4-dioxan-2-one, or a cyclic carbonate.
In addition to the above-described synthesis of functionalized epoxides before subsequent polymerization to form a copolymer with cyclic esters, the present invention contemplates functionalizing the side chain of the epoxide monomer after the epoxide has been ring-opened and the copolymer with the ring-opened cyclic ester formed.
Viewed from a further aspect, the present invention provides for functionalizing the epoxide to provide for greater control over the degradation of the resultant homopolymer. Similarly, the present invention provides for functionalizing the epoxide to provide for greater control over the degradation of the resultant copolymer when the functionalized epoxide is polymerized with cyclic esters.
Viewed from yet a further aspect, the present invention relates to improved methods of preparing a pharmaceutical composition in particulate or capsule form. In one aspect of the invention, the pharmaceutical composition is designed for the controlled release of an effective amount of an active agent over an extended period of time. The methods of the present invention may be carried out using preformed particulates, or may additionally comprise the production of the particulates.
Viewed from still another aspect, the present invention relates to methods of using the functionalized homopolymers and copolymers in various applications. In one aspect of the invention, the functionalized polymers as described herein can be used for biomedical applications such as orthopedic and dental applications, prosthetic devices, tissue sealant and wound healing, tissue engineering, and bone replacement/healing. In another aspect of the invention, the functionalized polymers described herein can be used as environmentally friendly polymers.
Features and Advantages
The present invention advantageously can be used for the synthesis of functionalized degradable polymers heretofore unavailable through standard synthetic methods. The synthetic methods of the present invention are easily adaptable to existing polymer synthesis protocols. The present invention offers the ability for extensive and diverse functionalization of the parent polymer system due to the ease of synthesis of a wide variety of functionalized epoxide monomers, allowing for easy derivatization either before or after polymerization.
Another advantage of the present invention is that the functionalized epoxide monomers described herein, can aid in the solubilization of other monomers in copolymerization reactions due to the fact that the functionalized epoxides are typically liquids, thus, allowing for the use of milder polymerization conditions. Those other monomers include molecules such as lactide, glycolide, and any other monomer that requires either high temperatures to induce melting or the use of secondary solvents. The solubilization properties of the functionalized epoxides allow for mild copolymerization reaction conditions, i.e., lower reaction temperatures and pressures, and milder catalyst systems. Not requiring a separate solvent phase in which to carry out the polymerizations greatly enhances the ability to retain functionality in the resulting polymer by avoiding any possible detrimental side reactions between the solvent and the monomers as well. The solubilization by the functionalized epoxide also permits formation of copolymers in a single step, rather than sequentially involving numerous steps.
Additionally, because the result of the copolymerization of the functionalized epoxide and the cyclic ester is a polymer backbone that is a derivative of both polyethylene oxide and cyclic esters (i.e., the standard synthesis of degradable polyesters), toxicity issues should be minimal, if not nonexistent. Although polymers consisting of both polyether and polyester are known, the polyether exists as only a few higher molecular weight segments which are nondegradable, whereas the copolymers of the present invention result in ether functionality distributed throughout the polyester. This allows the copolymer to be degraded into smaller molecules, e.g., having a molecular weight less than 600, which are more easily metabolized or eliminated by the body.
Another advantage of the present invention is that the incorporation of functionalization into the polymer provides for the enhanced control over the physical characteristics of the polymer, in particular, polymer degradation. The ability to control these physical characteristics offers enhanced control over the hydrophilicxe2x80x94lipophilic balance (HLB) in a given polymer system, which can affect the rate of water uptake, which is one of the parameters that plays a role in the trade off between bulk degradation and surface degradation of a polymer.
Also, control over functionalization provides for improved polymer processing and use in a greater diversity of potential applications. The functionalized polymers of the present invention can be processed to form particulates for delivery of active agents in pharmaceutical applications. Certain functionalized polymers with unsaturated substituents can be crosslinked, even in vivo, to form polymer networks for high strength applications. Other functionalized polymers can be synthesized to form thermoresponsive polymer gels, so that a liquid polymer at room temperature becomes a gel or a solid once it is injected into a human or animal body, facilitating the ease of injection.

Degradable polymers from derivatized ring-opened epoxides


A method for designing a circuit layout which includes the steps of supplying a predictive capacitance value for at least one net of a circuit layout, and placing and routing all nets of the circuit layout using at least one predictive capacitance value as a layout design constraint.

1. Field of the Invention
The present invention generally relates to methods for laying out integrated circuits.
2. State of the Art
It is well known to use computerized systems for laying out integrated circuits such as application-specific integrated circuits that include a number of functional blocks or "cells." A standard cell within an application-specific integrated circuit may comprise, for example, one or more random access memories (RAMs), read-only memories (ROMs), or arithmetic logic units. During the design of integrated circuits, it is usually necessary to determine the signal delays. Although signal delays can be determined by testing prototype of integrated circuits, prototypes are usually expensive. Accordingly, it is desirable to develop techniques for calculating signal delays prior to laying out integrated circuits.
In practice, however, it is difficult to calculate signal delays in integrated circuits. In part, the difficulties arise because the computational techniques, to be of practical and convenient, must be capable of computing all interconnect delays in integrated circuits having, for example, one-hundred thousand transistors by using a desk-top work station over a time period less than about one hour.
In integrated circuits, signal delays can arise from various sources, including the resistance and capacitance of wires that connect elements within the circuits. Also, delays through gates in integrated circuits depend upon the loads driven by the gates drive and upon the quantity of interconnecting logic. Signal delays increase as integrated circuits become denser (i.e., contain increased numbers of elements).
Computer-based simulations are often used for estimating signal delays in integrated circuits during design. In one common simulation method, a computer program solves systems of nonlinear differential equations that are derived from the state equations which describe an integrated circuit. Such simulation programs require substantial computational time and data storage and, therefore, are impractical for routine analysis of most integrated circuits of the LSI and VLSI class.
A technique called "macro-modelling" has also been used by circuit designers for simulating LSI and VLSI integrated circuits. According to this technique, macro-cells of an integrated circuit design are modelled as a small number of "standard" blocks, each of whose electrical characteristics are pre-characterized by, for example, circuit simulation. A block in a macro-modelled circuit might be, for example, a NAND gate. In this example, the pre-characterization of the block might provide a simple rule for calculating the delay at the block output as a function of the driven capacitance and of the signals arriving at input pins of the block. Using the pre-characterization rule, a system such as a logic simulator or timing verifier can predict the delay through the block.
In current practice, most logic simulators employ macro-modelling to compute delays through integrated circuits as functions of total capacitive load. These logic simulators typically perform their functions without explicitly accounting for the resistance of interconnecting paths in the simulated circuits.
Because the length of interconnecting paths in an integrated circuit normally are not known until after a physical design of the circuit has been completed, standard design practice is to use "predictive" capacitance to approximate timing delays caused by interconnecting wires in the circuit nets. (In this context, the term "nets" refers to sets of two or more circuit nodes, such as the inputs or outputs of a gate, which are joined by an interconnection.) The term "fanout one net" refers to a circuit layout net wherein a single output node of a circuit net directly drives only one other circuit net.
One problem with using conventional techniques using predictive capacitance for estimating interconnect timing delays in integrated circuits is that, after placing and routing an integrated circuit, some nets in the circuit may have capacitances substantially larger than the predicted values. In fact, the actual capacitances may exceed the predicted values even if the majority of the nets in a circuit have capacitances that are substantially smaller than their predicted values. In such cases, the majority of nets in the circuit may run faster than expected while some of the nets run much slower. Such operating speed differentials can cause timing problems which, in turn, require either manual rerouting or redesign of a circuit.
To avoid the above-discussed drawbacks, "timing-driven layout" techniques can be used. In such techniques, timing constraints are employed while placing and routing an integrated circuit. This usually involves determining timing requirements between input and output signals, and using a timing analysis tool to convert the timing requirements into layout constraints. The layout constraints can be revised as more information becomes available concerning the layout appearance. Timing-driven layout techniques are described by Michael Burnstein and Mary N. Youssef in an article entitled "Timing Influenced Layout Design" IEEE Paper 9.2, 22nd Design Automation Conference, 1982, pages 124-130.
Timing driven layout techniques cannot, however, simultaneously satisfy a large number of critical paths in an integrated circuit. Because of this limitation, circuit designers cannot specify all critical paths in large circuits without causing the timing analysis tools (which specify maximum lengths for nets) to be too slow for practical use. Consequently, timing driven layout techniques have not achieved widespread use.

Predictive capacitance layout method for integrated circuits


An image is formed in a photographic element by a process comprising a step of heating a heat-developable photosensitive material in the presence of a specific compound which typically releases a phenylmercaptotetrazole having a substituted benzene ring and serving as a development retarder.

This invention relates to an image forming process including a heating step, and more particularly, to a process for forming images by heating using a precursor of a development retarder.
Heat developable photosensitive materials and their image forming processes are well known in the art and described in the literature, inter alia, "Fundamentals of Photographic Engineering", Corona Publishing K.K., Tokyo, Japan (1979), pages 553-555; "Image Information", April 1978, page 40; and Nebletts Handbook of Photography and Reprography, 7th ed., Van Nostrand Reinhold Company, pages 32-33.
A number of methods have been proposed for producing color images through heat development, for example,
a process for forming color images using a coupler as a dye-providing substance (see U.S. Pat. Nos. 3,531,286; 3,761,270; and 4,021,240; Belgian Patent No. 802,519; and Research Disclosure, September 1975, pages 31-32),
a process of forming images using a dye having a nitrogen-containing heterocyclic group incorporated in its dye moiety as a dye-providing substance (see Research Disclosure, May 1978, pages 54-58, RD-16966),
a process based on silver dye bleaching (see Research Disclosure, April 1976, pages 30-32-, RD-14433; ibid, December 1976, pages 14-15, RD-15227; and U.S. Pat. No. 4,235,957), and
a process for forming a color image using a leuco dye (see U.S. Pat. Nos. 3,985,565 and 4,022,617).
These color image forming processes, however, have their own drawbacks and commonly suffer from the insufficient shelf storage of photosensitive material that the material deteriorates with a lapse of time as exemplified by increasing fog. Proposed as a solution of this problem is the use of a reducing dye-providing substance capable of releasing a hydrophilic dye as disclosed in Japanese Patent Application Kokai No. 58-58543. This proposal has succeeded in significantly overcoming the technical problems of the prior art processes.
Nevertheless, because of the absence of development inhibiting or retarding means, the aforementioned image forming processes based on heat development cannot avoid such problems as increasing fog due to overdevelopment and varying photographic performance due to varying heating temperature, and thus they are still difficult to always produce consistent images.
On the other hand, several development inhibiting techniques are known in the conventional diffusion transfer photography. For example, development inhibitor precursors and color diffusion transfer photographic materials using same are described in Japanese Patent Publication Nos. 60-19498 and 60-29709. These patents describe or suggest nowhere the application to heat developable photosensitive material. Quite unsatisfactory results could be obtained when the compounds disclosed in these patents are added to heat developable photosensitive material.

Image forming process including heating step


The present invention provides a material for a molded resin as a material for a semiconductor light-emitting device that can yield a highly durable (light resistance and heat resistance) molded resin and can also improve the LED output through an excellent reflectivity. The present invention also provides an easily moldable material for a molded resin for a semiconductor light-emitting device. The material for a molded resin for a semiconductor light-emitting device is a resin composition, comprising (A) a polyorganosiloxane, (B) a white pigment, and (C) a curing catalyst, wherein the white pigment (B) has the following characteristics (a) and (b):    (a) an aspect ratio 1.2 or more and 4.0 or less, and    (b) a primary particle diameter 0.1 μm or more and 2.0 μm or less.

As shown in FIG. 1, a semiconductor light-emitting device made by mounting a semiconductor light-emitting element is composed of, for example, a semiconductor light-emitting element 1, a molded resin 2, a bonding wire 3, an encapsulant 4, and a lead frame 5. The structure comprising the electroconductive metal interconnects, e.g., the lead frame, and the insulating molded resin is referred to as the package.
Insulating materials provided by incorporating a white pigment in a thermoplastic resin, e.g., a polyamide, have already entered into general use as insulating materials used for molded resins (refer, for example, to Patent Document 1). In the case of semiconductor light-emitting devices where directionality is required of the emitted light, the light-emitting efficiency is required not just by the light emitted in the desired direction from the semiconductor light-emitting element, but also by causing light emitted in undesired directions to be reflected from, e.g., the molded resin, metal interconnects such as the lead frame, and reflectors, into the desired direction. Since thermoplastic resins such as polyamides are light permeable, the light-emitting efficiency of a semiconductor light-emitting device can be raised by incorporating—when light is to be reflected by the molded resin—a white pigment in the resin and reflecting the light emitted from the semiconductor light-emitting element by utilizing the difference in the refractive indices between the resin and white pigment.
Even when a white pigment is used in Patent Document 1, its reflection efficiency may not be satisfactory depending on the particular type of white pigment, and light absorbed in the molded resin and light penetrating through the molded resin also ultimately escape. Due to this, it has not been possible in some cases to concentrate the light from the semiconductor light-emitting element in the desired direction and the light-emitting efficiency of the semiconductor light-emitting device has been reduced as a result.
In addition, there is currently a trend toward higher reflow temperatures due to a strong trend toward the use of higher melting lead-free solders brought on by environmental concerns. Polyamides are thermoplastic resins, and polyamides are thus softened by this heat and the heat resistance of the package then becomes a problem in the case of packages that use polyamide. Furthermore, polyamides are subject to photodegradation and thermal degradation by ultraviolet radiation and heat, and degradation by light has become a problem in particular when light-emitting elements are used that have a light-emission range that extends into high-energy wavelength regions, such as the blue to near-ultraviolet semiconductor light-emitting elements whose commercialization has been ongoing in the recent years. Moreover, thermal degradation and photodegradation have become even more significant problems due to the heat and high luminous flux light generated by the semiconductor light-emitting element as a result of contemporary demands for brighter light-emitting elements.
Otherwise, an alumina-containing sintered ceramic may be used as the insulating material in those cases in which heat resistance is required (refer, for example, to Patent Document 2). A package that uses this ceramic does have a good heat resistance, but its production requires a high-temperature sintering step post-molding. This sintering step has posed the following problems: cost problems due, for example, to electricity costs; the ease of appearance of defective products due to changes in the size and shape of the molding caused by sintering; and an impaired productivity.
In contrast to the preceding, a case has also recently been introduced that is provided by molding a silicone resin composition that uses an organopolysiloxane for the resin and uses titanium oxide for the white pigment (refer, for example, to Patent Document 3). The use of the organopolysiloxane for the resin is intended to improve the heat resistance over that for the use of polyamide.
Patent Document 1: Japanese Patent Application Laid-open No. 2002-283498
Patent Document 2: Japanese Patent Application Laid-open No. 2004-288937
Patent Document 3: Japanese Patent Application Laid-open No. 2009-155415

Material for a molded resin for use in a semiconductor light-emitting device


The present invention is directed to a method and system for installing and programming a network interface module within a security system. A security programming system may be implemented from a computing device connected over a network with the network interface module. The computing device may communicate with a server storing components of the security programming system. The security programming system may include user interface components located on the server and accessible through a browser of the computing device to enable selection of a network interface module participating in the security system and selection of a security system application program. The system may additionally include one or more programming applications located on the server for programming the selected network interface module to operate within the security system, wherein the programming application is selectable from the user browser of the computing device.

Currently, in the field of security systems, network interface modules require installation and programming in order to function within the security systems. The field of security systems may include, but should not be limited to intrusion detection systems, fire alarm systems, and access restriction systems. Installation and programming of network interface modules within these systems require individuals to have knowledge of network terminology, network tools, and network functions. Accordingly, only trained individuals are capable of installing and programming network interface modules within security systems.
Specifically, FIGS. 9-17 illustrate a currently available installation and programming technique. The screen displays shown in these FIGs illustrate the fact that no icon-based user-friendly operating system is available for the installation and programming of network interface modules. FIG. 9 illustrates an initial screen 900 that requires entry of a Media Access Control (MAC) address and an Internet Protocol (IP) address. The MAC address is a hardware address that identifies nodes within a network. Accordingly in order to proceed, individuals must be aware of these addresses.
FIG. 10 illustrates a display 1000 including an Address Resolution Protocol (ARP) table that is subsequently produced. The ARP is used to convert an IP address into a physical address. The installer is required to verify that the entered information appears in the ARP table. Subsequently, as shown in FIG. 11, a display 1100 requires the installer to open a Telnet prompt and attempt to connect to the IP address. The Telnet program connects a computing device to a server on the network such that commands will be executed as if they had been entered directly onto a server console.
FIG. 12 includes a screen display 1200 that shows a failure to connect. An attempt to connect to the IP address on an alternate port 9999 is shown by screen 1300 in FIG. 13. If the connection is successful, the installer may be prompted to enter setup mode as shown by screen 1400 in FIG. 14.
FIGS. 15 and 16 provide screens 1500 and 1600 respectively that require the installer to select entries from the menu and enter related parameters. In FIG. 15, the installer selects "0" and in FIG. 16, the installer enters the parameter "1". FIG. 17 illustrates a screen display 1700 showing that the installer has selected "6" from the menu because the installer is using encryption. The installer is also required to enter the parameters as shown.
Accordingly, the current model requires knowledge of network terminology, network tools and network functions. These include IP addressing, subnets, MAC addresses, ARP, and TELNET. This requirement makes it difficult for individuals who have not been trained on the network to install or program a network device. Thus, a solution is needed that facilitates installation and programming of network interface modules and provides user-friendly interfaces that can be utilized without extensive network training.

System and method for installation of network interface modules


A method for releasing a micromechanical structure. A substrate is provided. At least one micromechanical structural layer is provided above the substrate, wherein the micromechanical structural layer is sustained by a sacrificial layer of a silicon material. An amine-based etchant is provided to etch the silicon material. That is, during performing a post-cleaning procedure with an amine-based etchant, polymer residue and the sacrificial layer of silicon can be simultaneously removed without any additional etching processes.

1. Field of the Invention
The present invention relates to a method for releasing a micromechanical structure, and more particularly, to a method of etching an amorphous silicon layer during the microelectromechanical structure (MEMS) process.
2. Description of the Related Art
The use of selective etchants to remove sacrificial layers or regions in a multilayer structure without removal of an adjacent layer or region is a common step in the manufacture of semiconductor devices and MEMS. MEMS have found applications in inertial measurement, pressure sensing, thermal measurement, micro-fluidics, optics, and radio frequency communications, and the range of applications for these structures continues to grow. One example of such a structure is a reflective spatial light modulator, which is a device consisting of a planar array of electrostatically deflectable mirrors, each microscopic in size. The device is used as a micro-display system for high resolution and large screen projection. The sacrificial layer in such a device is the layer over which the mirror material is deposited. Once the mirror structure is formed, the sacrificial layer is removed to leave gaps below the mirrors and microhinge along one edge of each mirror to join the mirror to the remainder of the structure. The gap and the microhinge provide the mirror with the freedom of movement needed for its deflection. Devices of this type are described in, for example, U.S. Pat. No. 6,356,378.
The success of a manufacturing procedure for structures involving sacrificial layers depends on the selectivity of the etching process. The thickness and lateral dimensions of the layers, and in the case of the deflectable mirror structures, the width of the gap and the integrity of the microhinges, are all critical to achieve uniform microstructure properties and a high yield of defect-free product. One of the critical factors is the quality of the etching process. Performance, uniformity and yield can all be improved with increases in the etch selectivity of the sacrificial layer relative to the adjacent functional layers.
Among the etchants that are used for the removal of sacrificial layers or regions in etching procedures are noble gas fluorides and halogen fluorides. These materials, used in the gas phase, selectively etch silicon relative to other materials such as silicon-containing compounds, metallic elements, and compounds of metallic elements. The selectivity is not infinite, however, and would vary widely with the specific equipment, process, materials and reaction conditions. Xenon difluoride (XeF2), for example, has demonstrated selectivity as high as 400:1 to 500:1. Nevertheless, the XeF2 etcher is a special and expensive facility for current semiconductor processes, thereby increasing additional equipment and material costs. In addition, when the sacrificial layer is very thick (e.g. above 2000 Å), XeF2 etching requires longer etching time, thereby reducing manufacturing efficiency.
In U.S. Patent Application No. 20020197761, Patel et al disclose a method for releasing a micromechanical structure. The method performs a first etch to remove a portion of the sacrificial material, wherein the first etch provides an etchant of CH4 or C4H8 so as to allow the etchant to physically, or chemically and physically, remove the portion of the sacrificial material. Then, a second etch is performed to remove additional sacrificial material, wherein the second etch provides an etchant of XeF2, IF5, IF7 or BrF3 that chemically but not physically etches the additional sacrificial material. Though effective, this method nevertheless requires special and expensive dry etchers, such as the XeF2 etcher.
In U.S. Pat. No. 6,290,864, Patel et al disclose a gas-phase etching procedures for the manufacture of MEMS. The method, utilizing etchant gases that are noble gas fluorides or halogen fluorides, is performed with greater selectivity toward the silicon portion relative to other portions of the microstructure by the addition of non-etchant gaseous additives to the etchant gas. Thus, this method still requires special and expensive dry etchers, such as the XeF2 etcher.
In U.S. Pat. No. 6,396,619, Huibers et al disclose a deflectable spatial light modulator (SLM). The patent does not teach how to etch the sacrificial layer of amorphous silicon.

Method for releasing a micromechanical structure

Taiwan Semiconductor Manufacturing Co., Ltd.


A method for pushing a list element onto a linked list without locking the linked list. The linked list includes a head element having a pointer to a first list element. The method includes the steps of (a) reading the pointer, (b) writing the pointer to a list element address field, and (c) atomically comparing the pointer written to the list element address field with the pointer to the first list element and exchanging an address of the list element for the pointer if the values compared are equal, else repeating steps (a) through (c). A non-blocking pop operation is also disclosed.

1. Field of the Invention
The invention relates generally to the field of computer algorithms and more particularly to a system and method for managing concurrent operations on linked lists.
2. Description of the Related Art
A linked list is a collection of elements, such as data elements, that are accessed in an explicitly ordered fashion. Common list access operations include a write or push operation which adds an element onto the list, and a read or pop operation which removes an element from the list.
Such list operations take a discrete interval of time to complete and often include more than one sequential step. With concurrent, a synchronous list operations taking place, a new list operation may be executed while the sequential steps of a currently-executing list operation are in progress. To avoid such a possibility and the consequent list inconsistencies and errors, prior art list management systems and methods have required that the list be locked for the duration of the list operation, whether pushing an element onto the list or popping an element from the list.
In the systems and methods of the prior art, consistency is improved at the expense of system performance. For example, new list operations are prevented from executing while the list is locked thereby reducing the throughput of the entire system.
What is needed then is a system and method for managing concurrent operations on linked lists that improves system performance. Such a system and method preferably increases system throughput by eliminating the need to lock the list under certain conditions.
A method for pushing a list element onto a linked list without locking the linked list is disclosed. The linked list includes a head element having a pointer to a first list element. The method includes the steps of (a) reading the pointer, (b) writing the pointer to a list element address field, and (c) atomically comparing the pointer written to the list element address field with the pointer to the first list element and exchanging an address of the list element for the pointer if the values compared are equal, else repeating steps (a) through (c).
An alternative embodiment of the invention includes a pop operation which polls a pop lock and takes ownership of the pop lock before popping an element from the linked list. This embodiment is preferably employed in a first condition in which the frequency of push operations dominates the frequency of pop operations and the likelihood of synchronous operations is high.
Yet another embodiment of the invention includes a method for popping a list element from a linked list, the list element including a next list element address and a list element counter. The linked list includes a head element having a pointer to the list element and a head counter equal to the list element counter, the next list element address and list element counter being stored in contiguous memory, and the pointer and head counter being stored in contiguous memory. The method includes (a) reading the pointer and head counter, (b) writing the pointer and head counter to a temporary head, (c) reading the next list element address and the list element counter from the list element, (d) incrementing the list element counter, (e) atomically comparing the pointer and head counter with the pointer and head counter written to the temporary head and exchanging the next list element address and the list element counter for the pointer and head counter if the values compared are equal, else repeating steps (a) through (e), and (f) decrementing the head counter.
This embodiment is preferably employed in a second condition in which the frequency of pop operations dominates the frequency of push operations and the likelihood of synchronous operations is low. A push operation in this embodiment operate in similar fashion to the push operation described above.
The invention includes a method by which an preferred method of pushing and popping list elements to the linked list is selected based upon the frequency of pop operations relative to push operations and the likelihood of synchronous operations.

System and method of managing concurrent operations on linked lists


Described is a method of constructing prize structures that are particularly useful in gaming systems which can be used to implement various games such as bingo and poker. In particular the described pay structures and game systems can have sufficient granularity such that the outcome or payoff of the game being played can be expanded to provide higher payout amounts as well as closely replicate the payoff of a second game. Included are methods and apparatus for playing bingo games and determining which bingo cards are winners. In addition, methods and apparatus for evaluating or checking each card in a bingo game using a bit marked card technique and vector operations are described.

In the gaming industry in general and in casino environments as well as internet applications in particular it is desirable to provide gaming systems including bingo apparatus and systems that are attractive for customers to play while providing an acceptable return to the proprietor of the gaming systems. It is also desirable to provide multiplayer card gaming systems that are attractive for customers to play while providing an acceptable return to the proprietor of the gaming systems.
Regarding bingo games, most electronic bingo games are played in a similar manner to conventional bingo games where a player pays for and plays one or more bingo cards. Balls having marks or symbols corresponding to squares on the cards are sequentially drawn, or in the case of electronic systems, randomly generated. The first card in which a predetermined patterns of squares, such as columns, diagonals, rows or corners, is filled by symbols on the drawn balls is the winner. Typically, the prize is paid to the player with the winning card or if two or more cards have one of the predetermined patterns, the prize can be split. There are a number of variations on this approach especially in electronic implementations of bingo. For example, after the initial purchase of one or more cards, the game requires the players to pay a predetermined amount per card for the next ball or series of balls and thus the player has the option of only paying for cards that appear to be close to winning.
However, the bingo games as described above have a number of disadvantages. For example, since the games normally pay out only one large prize to the player having a winning pattern, a player playing a bingo game, especially with a large number of players, can play for a long time without winning anything and hence become discouraged.
Also, a number of problems can arise in implementing the bingo games as described above in an electronic format, or especially in internet based games. For example, since an internet based bingo game can have thousands of players playing a game where in addition each player can have a number of cards, the marking and evaluating each of what can be thousands of cards for a winning bingo pattern after each ball is drawn in a rapid and efficient manner can be a challenge.
Regarding multiplayer poker gaming systems, one approach to such a system involves each player playing on his own terminal or personal computer where under control of a central computer or internet website the players play against each other. The terminals can have displays showing the hands as dealt, winning hands and other game information. The game can be played using the central computer to deal each player a hand from one or more simulated card decks corresponding to casino type games where a dealer deals hands from one or more card decks. However, this approach tends to be effectively limited to about ten players (10 players×5 cards per player=50 cards from a 52 card deck). For such a system with more than ten players, it becomes difficult to construct a prize structure when dealing is done from a single deck or even a combination of multiple decks and especially for internet games which might have thousands of players in a single game. As a result, poker type games with very high payouts based, for example, on the number of players in the game become especially difficult to construct.
One example of an attempt to provide enhanced player appeal is to structure a multiplayer gaming system such that each individual gaming machine includes a set of player controls in which a game such as bingo, keno or poker can be played and a first display for displaying the game as it is played and further includes a second display for displaying the outcome of the game in a different game format. The second display can for example display the outcome and indicate the payout of a bingo game in the form of spinning slot machine reels. Examples of these types of gaming systems are shown in U.S. Pat. Nos. 7,322,886 and 7,641,552.
However, the dual game display approach as described above does not address the problem of providing prize structures, especially where one type of game is played and the outcome is displayed in a different game format, such that the prize structures are sufficiently flexible to allow game designers to optimize payoff tables for maximum player appeal while providing a specified return to the game system proprietor.


Used in a mobile robotic vacuum cleaner, a dust collector is disclosed to include a dust collection box, and a chips collection box connected to the dust collection box. The chips collection box comprises two openings respectively disposed adjacent to one respective roller brush of the mobile robotic vacuum cleaner and adapted for receiving chips directed by the roller brush for enabling the directed chips to be gathered in the chips collection box. Thus, dust sucked by the mobile robotic vacuum cleaner and chips directed by the roller brushes are respectively collected in the dust collection box and the chips collection box, and any non-dust articles that are accidentally directed into the chips collection box can be discovered and cleaned easily by the user.

1. Field of the Invention
The present invention relates to mobile robotic vacuum cleaner technology and more specifically, to a dust collector for mobile robotic vacuum cleaner.
2. Description of the Related Art
A conventional mobile robotic vacuum cleaner is known comprising a dust collector that has an inlet for letting air in, an outlet for letting air out, and a wire gauze filter mounted in the outlet for removing dust from air passing out of the outlet and keeping filtered dust in the dust collector. Further, the autonomous floor-cleaning robot as disclosed in U.S. Pat. No. 6,883,201, includes continuously rotatable brush means for moving heavy particles from the floor into the inside of the dust collection box therein.
However, during operation of the aforesaid prior art autonomous floor-cleaning robot, non-dust articles may be brushed from the floor into the inside of the dust collection box. When the user is cleaning the dust collection box, the non-dust articles have already mixed with dust and are difficult to be cleaned. These non-dust articles may be directly discarded with the dust by the user without being viewed. Therefore, an improvement in this regard is necessary.

Dust collector for mobile robotic vacuum cleaner


The present invention can suppress the generated code quantity for each image increment so as not to exceeding the target code quantity without having a usage quantizing factor deviate greatly in a sure manner.

Heretofore, with a system or the like for transmitting a moving image or recording this in a recording medium, high-efficiency encoding has been carried out to take advantage of a transmission path or recording capacity effectively. With an image encoding device for realizing this, the encoding bit rate of a bit stream generated at an encoder is set to be a certain rate according to the transfer rate of a transmission medium, and under this restriction, a data generated quantity, i.e., the quantizing step of quantization at the encoder is controlled. That is to say, the image encoding device suppresses the data generated quantity by increasing the quantizing step, for example, when images having a complicated picture pattern continue, and conversely, when picture images having a simple picture pattern continue, a fixed rate is held so as not to cause overflow or underflow of buffer memory by reducing the quantizing step and increasing a data generated quantity.
Accordingly, with an image encoding device according to such a conventional technique, when complicated images continue, the quantizing step increases, and image quality deteriorates, and when simple images continue, the quantizing step decreases, and uniform image quality is not available as a whole. In the light of this problem, for example, with Patent Document 1, an image encoding device has been disclosed wherein an assigned code quantity to be assigned to each GOP itself in accordance with the ratio of sum of encoding difficulty for each GOP (Group Of Pictures), and encoding difficulty for multiple GOPs, is assigned more to a GOP including an image having a complicated picture pattern, and is assigned less to a GOP including an image having a simple picture pattern.
On the other hand, as a method for adding a generated code quantity to the target code quantity given to one picture, for example, the step 2 of TM5 (test model 5) has been known well. This is a technique wherein the code quantity assigned to a picture distributed to macro blocks (MB; Macro block) is taken as the target code quantity of the MBs, and feedback control is applied within the picture.
Also, with the encoding processing of a redundant compressing method such as MPEG or the like, the image encoding device executes quantization processing after subjecting to orthogonal transform such as DCT (Discrete Cosine Transform) or the like, thereby executing processing for reducing information volume. Subsequently, the image encoding device controls the value of this quantization to execute control of code quantity. At this time, a monotonous reduction relationship holds between the quantization parameters and the generated code quantity. Therefore, the image encoding device computes a code quantity with the quantizing value of an appropriate interval, and subjects the predictive value of the code quantity positioned in the intermediated thereof to linear interpolation, or the like, whereby the generated code quantity can be predicted (binary search or the like to be executed with intra VTR such as DV or the like).
This method may be applied to not only an encoding method using a fixed table such as MPEG2 or the like but also a context adaptive encoding method used for AVC or the like.
Patent Document 1: Japanese Patent No. 3358620
However, with the above method in the step 2 of TM5, with encoding of a first picture in a sequence or a picture immediately after change in scenes, the initial value of the quantizing step is unmatched with the picture pattern of the picture thereof, and accordingly, there are cases where image quality deteriorates.
For example, with the method in the step 2 of TM5, with the image encoding device, in the case that the quantizing step of a portion up to where feedback follows the picture pattern is too great, the image quality of the portion thereof will be deteriorated as compared to other portions, and in the case that the quantized value is too small, the code quantity is excessively used at this portion, which may affect other portions.
Also, with the image encoding device, the target code quantity of MBs is set to be a certain code quantity constantly, and accordingly, inappropriate code quantity distribution is caused when there is a deviation regarding image difficulty within the screen, or the like.
Accordingly, it is an object of the present invention to suppress the generated code quantity for each image increment below the target code quantity in a sure manner without the usage quantizing factor, serving as the basis of the quantizing step, deviating greatly.

Image processing device and image processing method with feedback control

Abstract: An image encoding device (200) determines a basic quantization parameter (QPMB) serving as a basic quantizing factor to be predicted in the case that the main encoding generated code comes near the target code quantity at the time of encoding an input image (91). The image encoding device (200) encodes the input image (91) for each feedback control increment by executing quantization using an adapted quantization parameter (QPt) based on an average quantization parameter BaseQP serving as a usage quantizing factor determined based on at least the basic quantization parameter (QPMB). The image encoding device (200) confirms the generated code quantity of the encoded input image (91) for each feedback control increment, and in the case of predicting that the generated code quantity for each image increment will exceed the target code quantity, increases the value of the adapted quantization parameter (QPt) by increasing the average quantization parameter BaseQP.


A three-dimensional printing system for manufacturing three-dimensional articles includes an apparatus, a filtration system, and a controller. The apparatus is a fabrication system that generates ignitable powder dust in an inert atmosphere fluid stream. The filtration system receives the fluid stream and has a plurality of filter units in a parallel arrangement including at least a first filter unit and a second filter unit. The controller is configured to control the filtration unit and to thereby individually operate the plurality of filter units in two states including a filtration state and an oxidation state. When one of the plurality of filter units is operating in the filtration state another of the plurality of filter units is operating in the oxidation state.

Three dimensional (3D) printing systems are in rapidly increasing use for purposes such as prototyping and manufacturing. One type of three dimensional printer utilizes a layer-by-layer process to form a three dimensional article of manufacture from ignitable powdered materials. One example of ignitable powdered materials are powdered metals such as titanium powder in a generally unoxidized state. A three dimensional (3D) article is formed by (1) dispensing a layer of the powder, (2) selectively melting the layer of powder with an energy beam (e.g., high powered laser beam or electron beam), and (3) repeating the dispensing and selective melting to complete formation of the 3D article. Due to the ignitability of the powder, the process and powder handling are performed within an inert gas such as argon. During the processing and powder handling a powder dust can be generated which is then removed with a filter system. One danger is that the filter system can ignite and create a fire when the powder oxidizes.

Three-dimensional printer with two state filter for powdered metal


A light guide for interfacing between a light source having a light emitting surface with a first shape and a light receiver with a light receiving surface of a second shape. The light guide has a light emitting end having a first shape of substantially the same size as the first shape of the light emitting surface. A light receiving end has a second shape of substantially the same size as the second shape of the light receiving surface. A free form body between the light emitting end and the light receiving end causes a transition between the first and second shape.

Fiber-optic light sources are generally well known and are used in a broad range of applications. For example, in the medical field, fiber-optic illuminators such as various light sources, fiber-optics, and endoscopes are widely used in endoscopy. Bulb-based medical fiber sources are currently manufactured by Stryker, Smith-Nephew, Storz, Olympus, and others. Light sources and fiber-optics are commonly used for microscopy illumination, with lamp-based products offered by Zeiss, Welch-Allyn, Dolan-Jenner, and others. Fiber-optic illumination systems are also used with industrial boroscopes and machine vision systems. While the preceding devices primarily provide 'white' light for illumination, other fiber-optic light sources providing 'blue' light in the wavelength range 420-490 nm are used in photodynamic therapy for pediatric hyperbilirubinemia.
Systems having light sources and fiber-optics for light transmission can also provide one or more defined wavelengths of light for fluorescent excitation in biological and other research fields. For many applications, a round beam spot is desired, for example, an exam light, a spot light and a fiber optic light. In the case of a fiber optic light, the goal is to deliver more light through a fiber bundle. A fiber bundle is comprised of numerous fiber strands tightly packed together. All the fiber strands end at a cylindrical metal ferell. The fiber strands are then bound and polished. Light comes in from one end of the fiber bundle and is emitted out from the other end of the fiber bundle. When the fiber bundle end is round, the effective light transmission area is round. If the incoming light beam is from a rectangular or square shaped light source, depending on the size, only portion of the light is transmitted or portion of the fiber strands are utilized resulting in inefficiency.
For example, the emitting area inside an LED package is the footprint of the die or die cluster, which usually has a square or rectangular shape. When a lens system is used to collect light from LED(s), the output beam is the image of the LED die and is thus square or rectangular. This square or rectangular output beam therefore does not match the round fiber end and causes inefficiency because some light is lost in the transition. For many applications, it is desirable that the output light in a range of wavelength or color different than the source. Some manufacturers use additional filters to achieve that, increasing system complexity and cost. With the inventive light guide, filters can be integrated with the light guide by film deposition or color doping. The output beams currently use devices such as LEDs that are closely tied to the fiber optics. However, the shape of the LEDs still results in some inefficiencies. Another light guide is a thin plate for a surface light source that generates a highly uniform light. Such a light guide still creates inefficiencies as light is lost between the light source and the light guide.

Light guide for coupling differently shaped light source and receiver


A stator shaft is press-fitted and secured to the inner peripheral surface of a pump cover positioned between a torque converter and a automatic transmission mechanism section. Bushings are fitted to a part opposing the press-fit section with reference to the outer peripheral surface of an input shaft fabricated with a uniform diameter with the exception of the rear end part, and to a part slightly forward of the above-mentioned part, respectively, and an oil channel for the torque converter feed pressure is formed between the two bushings. As a result, the forward end section of the input shaft is supported in a freely rotatable manner by the bushings which are relatively close to each other. The torque converter feed pressure is fed from an oil channel formed in the pump cover to an oil channel between the two bushings, and through the cross hole and the center hole formed in the input shaft to the torque converter. The stator shaft is press-fitted into the pump cover and secured to it, and back-up is provided to the press-fit section by bushings.

1. Field of the Invention
The present invention relates to an automatic transmission with a fluid torque converter, and, in particular, to a support structure for an input shaft and to an oil channel structure for providing pressurized oil to a torque converter.
2. Description of the Prior Art
Conventionally, front end section of an automatic transmission, as shown in FIG. 5, comprises a one-way clutch 195 which supports a stator 194 of a torque converter 109, and a stator shaft 113 secured to the inner peripheral surface of an inner race 195a of the one-way clutch. The stator shaft 113 extends toward the rear and is pressed into and secured to a pump cover 120, and bears the stator reaction. In addition, the stator shaft 113 is formed as a hollow shaft in which an input shaft 103 is free rotationally supported by means of bushings 110, 111. The input shaft 103 is formed as a stepped structure with a small diameter at the front end. An annular indented groove 101 is formed in a large diameter stepped section 103a and a seal ring 102 is installed in the groove 101. A torque converter feed pressure oil channel 116 is formed between the inner peripheral surface of the stator shaft 113 and the outer circumference of the small diameter section 103b of the input shaft between the seal ring and the front bushing 111. Also, the feed pressure in the oil channel is transmitted between a cross-hole 103d formed in the input shaft 103 and a center hole 103b, as well as between a converter front cover 191 and a turbine hub 196 and is fed into the torque converter 109.
However, in this automatic transmission, because the torque converter feed pressure oil channel 116 is formed by the seal ring 102 and the bushing 101, when the input shaft 103 is installed, scuffing of the seal ring 102 occurs, and the structure of the oil channel becomes defective. In addition, it is necessary to machine the groove 101 for the seal ring and in order to ensure the proper thickness for the groove it is necessary to provide a stepped structure for the input shaft 103. This increased machining and installation are troublesome.
The first busing 111 is positioned on the front end section and the rear bushing 110 on the rear end section of the stator shaft 103, so that the input shaft is lacking in flexibility, and excessive force applied to one bushing is a drawback from the aspect of wear. In addition, because the press-fit section where the stator shaft 103 is pressed into the pump cover 120 is not provided with back-up at the bushing, whirling of the input shaft causes the insufficient strength of the press-fit strength of the stator shaft. Especially in the case where the pump cover 120 is formed from an aluminum alloy, it may cause idling of the stator shaft 113.

Automatic transmission with stator shaft mounting structure


A system and method for retrieving certificates and/or verifying the revocation status of certificates. In one embodiment, when a user opens a digitally signed message, a certificate that is required to verify the digital signature on the message may be automatically retrieved if it is not stored on the user's computing device (e.g. a mobile device), eliminating the need for users to initiate the task manually. Verification of the digital signature may also be automatically performed by the application after the certificate is retrieved. Verification of the revocation status of a certificate may also be automatically performed if it is determined that the time that has elapsed since the status was last updated exceeds a pre-specified limit.

Electronic mail ("e-mail") messages may be encoded using one of a number of known protocols. Some of these protocols, such as Secure Multiple Internet Mail Extensions ("S/MIME") for example, rely on public and private encryption keys to provide confidentiality and integrity, and on a Public Key Infrastructure (PKI) to communicate information that provides authentication and authorization. Data encrypted using a private key of a private key/public key pair can only be decrypted using the corresponding public key of the pair, and vice-versa. The authenticity of public keys used in the encoding of messages may be validated using certificates. In particular, if a user of a computing device wishes to encrypt a message before the message is sent to a particular individual, the user will require a certificate for that individual. That certificate will typically comprise the public key of the individual, as well as other identification-related information. Similarly, if a user of a computing device receives a message that has been digitally signed by a particular individual, the user will require the proper certificate (comprising a public key) for that individual if the user wishes to verify the digital signature on the message. In some variant systems, a Pretty Good Privacy (PGP) key or some other object that serves to bind the sender's identity and a public key would be required to verify the digital signature of a message.
Typically, in known e-mail applications, if the certificate that is required to verify the digital signature of a signed message received by a user is not stored at the user's computing device, the user may attempt to search for and retrieve the requisite certificate (e.g. from a remote certificate server) by manually opening a different application to initiate the search and retrieval of the certificate. The user may then initiate a verification of the digital signature with the retrieved certificate through the e-mail application.
Furthermore, even if the certificate required to verify the digital signature of a signed message received by a user is already stored on the user's computing device, the user may wish to determine an up-to-date revocation status for that certificate. Typically, in known e-mail applications, the user may initiate a verification of the revocation status of certificates in order to retrieve such information manually, by identifying a specific certificate and selecting a corresponding menu option, for example.

This patent is subject to a terminal disclaimer.

System and method for retrieving certificates associated with senders of digitally signed messages


Various systems and methods for capturing media moments are described herein. An autonomous camera system for capturing media moments includes a configuration module to receive configuration parameters; a flight control module to autonomously maneuver the autonomous camera system over a crowd of people; a search module to search for a subject in the crowd of people based on the configuration parameters; and a control module to perform an action when the subject is found in the crowd of people.

In film and video, a cutaway shot is an interruption of a continuously captured shot. Cutaway shots may be inserted in post-production or during a live broadcast. Cutaway shots may be used to maintain the audience's attention, add flavor or context to the continuous shot, or capture an interesting event occurring away from the main action. Examples of cutaway shots include scenes of a players' bench during a timeout, scenes of couples on a "kiss cam," scenes of people laughing in response to a speaker's remarks, or scenes of fans after a game is decided.

Capturing media moments of people using an aerial camera system


A vacuum system for cleaning the base of a control blade guide tube comprises a vacuum source and a novel vacuum head. The vacuum source includes a conventional vacuum pump and filter, for trapping matter entrained in water driven by the pump. The vacuum head is disk-shaped and has an off-axis vacuum port which can scan the guide tube base when the disk is rotated 360.degree.. Elongated slots in the disk admit water down through the disk. Guide fins separate the slots from the vacuum port. The guide fins are shaped to provide a clearance over the guide tube base, effecting a highventuri action which helps sweep up debris on the guide tube base. An annular ridge on the disk surrounds a similar annular ridge on the base, isolating a control rod drive tube housing below the base from the vacuum. This prevents control rod drive components from being disturbed by the vacuum.

This invention relates to nuclear reactors and, more particularly to a vacuum for a control rod guide tube of a boilingwater nuclear reactor. A major objective of the present invention is to provide for more thorough and convenient evacuation of particles and objects from the base of a control rod guide tube.
Fission reactors rely on fissioning of fissile atoms such as uranium isotopes (U233, U235) and plutonium isotopes (Pu239, Pu241). Upon absorption of a neutron, a fissile atom can disintegrate, yielding atoms of lower atomic weight and high kinetic energy along with several high-energy neutrons. The kinetic energy of the fission products is quickly dissipated as heat, which is the primary energy product of nuclear reactors. Some of the neutrons released during disintegration can be absorbed by other fissile atoms, causing a chain reaction of disintegration and heat generation. The fissile atoms in nuclear reactors are arranged so that the chain reaction can be self-sustaining.
To facilitate handling, fissile fuel is typically maintained in fuel elements. Typically, these fuel elements have a corrosionresistant cladding. The fuel elements can be grouped together at fixed distances from each other in a fuel bundle. A sufficient number of these fuel bundles are combined to form a reactor core capable of a self-sustaining chain reaction. Neutron-absorbing control rods are inserted into the core to control the reactivity of the core. The reactivity of the core can be adjusted by incremental insertions and withdrawals of the control rod.
Each control rod is housed within a vertical guide tube which ensures the vertical orientation and motion of the control rod. The control rod is moved using a control rod drive mechanism which is at least partially housed in a stub tube which also serves to support the base of the guide tube. The base of the guide tube has a diameter greater than the diameter of the stub tube so that the guide tube base can be a disk with a central hole through which the control rod drive uncoupling rod is mechanically coupled to the control rod.
Given that the control rods are the primary means for regulating reactor output, it is essential that the control rod drives remain fully functional. However, dust, sediment and various foreign objects falling into a drive mechanism housed in a stub tube can impair control rod drive functioning. Potentially, the control rod mechanism could jam, preventing control rod insertion and withdrawal. Alternatively, the foreign material can prevent the control rod drive mechanism from being removed for maintenance.
In the course of the present invention, foreign material, including rust particles, oxide dust, water impurities, and occasionally larger items, were found at the base of guide tubes. Turbulence, especially during removal and insertion of control rods could disturb these materials causing them to fall into the stub tubes, where they could impair control rod drive mechanisms. It was determined that sweeping was not an effective method of removing these materials from the guide tube base. Vacuums were problematic because they were difficult to position. Also, if the vacuum were great enough to remove the bulk of the material on the guide tube base, it could also remove control rod drive components from the stub tubes. For example, a control rod drive uncoupling rod could be pulled into the vacuum. What is needed is a system for cleaning control rod guide tubes which removes the bulk of material deposited on the base without disturbing the control rod drive mechanism.

Vacuum system for nuclear reactor guide tube