It can be difficult to achieve efficient transformation of many strains of bacterial cells due in part to the presence of one or more restriction and modification (R-M) systems in the cells that restricts unmodified transforming DNA. Phage T7 OCR protein is a potent inhibitor of Type I R-M systems. Methods are disclosed for improving transformation efficiency of Eubacterial and Archaebacterial cells having an R-M system by introducing into the cells an inhibitor of the restriction activity. For example, addition of 1–5 micrograms of T7 OCR protein to 50 microliters of electrocompetent cells having a Type I R-M system prior to electroporation significantly increased transformation efficiency by unmodified plasmids, fosmid clones, and artificial transposons comprising synaptic complexes. Other inhibitors or restriction activity, such as phage-encoded proteins and proteins encoded by conjugative plasmids, as well as other disclosed inhibitors, also can be used to improve transformation (and transposition) efficiency. Host cells with heritable improved transformation efficiency can be made by transforming a cell having an R-M system with an expressible gene which encodes an inhibitor of the restriction activity, which gene can be conditionally expressible. Transient expression of a gene on an unmodified transforming DNA can also be improved by in vivo inhibition of restriction in host cells having an R-M system. Kits and compositions for carrying out the methods of the invention and host cells made using the methods are also disclosed.

1. Field of the Invention
This invention relates to methods and compositions for improving DNA transformation efficiency of host strains by inhibiting host cell restriction activity.
2. Prior Art
DNA transformation is an important process in molecular biology. Transformation is the process of contacting a cell with a DNA molecule under conditions so that the DNA is taken up and incorporated into the cell so has to produce a heritable genotype. The cell into which the DNA is introduced is commonly referred to a "host cell." Host cells used for DNA transformation include, but are not limited to, bacterial cells. A host cell can be a cell comprising any organism. Many aspects of transformation, including some methods and information for different types of host cells, have been described in a review [Smith, H. O., et al., "Genetic Transformation," In: Ann. Rev. Biochem., 50: 41–68, 1981), incorporated herein by reference.
One purpose for transformation, the process of which is also referred to as "transforming a host cell," is to clone a DNA molecule comprising natural or synthetic DNA. In order to clone a DNA molecule, the DNA is joined to a replicable vector, such as a plasmid or bacteriophage vector, which is capable of replicating autonomously in the host cell. Once the DNA is joined to the vector, the resulting "recombinant DNA" is used to transform a suitable host cell. Then the host cell is grown in a culture medium in order to multiply the number of cells, which are descendents of the host cell, each of which contains one or more copies of the recombinant DNA. This process of "DNA cloning" or "molecular cloning" thus enables one to obtain multiple copies of a single recombinant DNA molecule. Many cloning vectors and methods related to cloning and transformation are described or cited by Joseph Sambrook and David W. Russell [Molecular Cloning—A Laboratory Manual Volumes 1–3, Third Edition, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 2001], incorporated herein by reference.
To maintain the plasmid vector in the cell, the vector DNA typically contains a selectable marker. Any selectable marker known in the art can be used. For an E. coli vector, any gene that conveys resistance to any antibiotic effective in the cell, or any gene that conveys a readily identifiable or selectable phenotypic change can be used. Preferably, antibiotic-resistance markers, including, but not limited to, genes that confer resistance to kanamycin or other aminoglycoside antibiotics such as dihydrostreptomycin, gentamycin, neomycin, paromycin, or streptomycin, or to amphenicols, such as chloramphenicol (for which the gene is known as chloramphenicol transacetylase or CAT), are used. Those with skill in the art will know or know how to find other antibiotic-resistance genes and non-antibiotic selection methods to select for maintenance of a plasmid or other vector. A host cell can also be transformed by natural or synthetic DNA which is not joined to (or "cloned in") a replicable vector. For example, it is known in the art that if at least a portion of the transforming DNA has homology with DNA in the host cell, the transforming DNA can be incorporated into a host cell that has a "homologous recombination system" [e.g.s, See: Camerini, R. D., and Hsieh, P., "Homologous recombination proteins in prokaryotes and eukaryotes," Annual Rev. Genetics, 29: 509–552, 1995; Kowalczykowski, S. C., et al., "Biochemistry of homologous recombination in Escherichia coli," Microbiol. Rev., 58: 401–465, 1994; Heyer, W. D., and Kohli, J., "Homologous recombination," Experientia, 50: 189–191, 1994; Smith, G. R., "Homologous recombination in prokaryotes," Microbiol. Rev., 52: 1–28, 1988]. A homologous recombination system is comprised of enzymes which catalyze various reactions so as to bring about incorporation of foreign DNA which has at least some homology to DNA in the host cell into the DNA of the host cell.
Recently, researchers demonstrated that a host cell also can be transformed with a synaptic complex consisting of a DNA molecule comprising an artificial transposon and a transposase enzyme which recognizes the ends of the transposon [Goryshin and Reznikoff, U.S. Pat. No. 6,294,385]. Following transformation of the host cell with the synaptic complex, the transposase in the complex is activated by intracellular magnesium ions in the host cell so as to catalyze transposition of the transposon into the cellular DNA of the transformed host cell. In this case, the transforming DNA is introduced into the host cell's DNA and therefore, the transforming DNA does not require the capability for autonomous replication in the host cell.
A variety of methods and conditions are known in the art for improving the efficiency of transformation of a given host cell. These methods and conditions vary for different organisms and even for different strains of a particular organism. The efficiency of transformation is usually measured by stating the number of independently-transformed host cells that are obtained using a certain quantity of a transforming DNA under defined conditions of transformation. In most cases in which the transformation efficiency is determined, the transforming DNA encodes at least one gene, such as an antibiotic resistance gene, which can be used as a selectable marker. It is commonly stated in the art, for example, that 10.sup.2. up to about 10.sup.10. colony forming units (cfu) of a transformed Escherichia coli host strain (which is resistant to the antibiotic in the medium because of the presence of the antibiotic-resistance gene in the transforming DNA) are obtained per microgram of transforming DNA under the specified conditions, which would be described. In most experiments in which the transformation efficiency is determined using transforming DNA that encodes an antibiotic resistance gene, equal quantities of host cells which have been treated with transforming DNA are plated on two different media; one medium contains the antibiotic for which the transforming DNA encodes resistance and the other medium does not contain this antibiotic. Thus, the number of colonies which grow on the antibiotic-containing medium is used to calculate the cfu per quantity of transforming DNA under the conditions used, and the number of cfu on the antibiotic-containing plates divided by the number of cfu on the medium without antibiotic indicates the relative proportion of the host cells that were transformed by the transforming DNA.
One method to increase the uptake of a DNA molecule, or the efficiency of transformation, is to treat the host cell so as to increase its ability (or "competence") to take up DNA under transformation conditions. For example, treatment of bacterial cells with calcium chloride increases the cells' ability to take up DNA (Mandel, M. and Higa, A., "Calcium-dependent bacteriphage DNA infection," J. Mol. Biol., 53: 159–162, 1970; Cohen, S. N. et al., "Construction of biologically functional bacterial plasmids in vitro," Proc. Natl. Acad. Sci. USA, 73: 3240–3244, 1973). Many other variations have been described for increasing the competence of the cells by treating them with chemicals (e.g., Hanahan, D. "Studies on transformation of Escherichia coli with plasmids," Gene, 24: 317–326, 1983; Hanahan, D., et al., "Plasmid transformation of E. coli and other bacteria," Methods, Enzymol. 204: 63–113, 1991). This process is commonly referred to in the art as "making the cells chemically competent". Alternatively, a preferred method of transformation employs pulses of electric current to introduce the DNA into host cells, a process referred to as electroporation. The cells used for electroporation are usually grown and treated so as to make them more capable of transformation by electroporation and such cells are referred to in the art as "electrocompetent cells". Electroporation of prokaryotic cells with DNA material is typically achieved by the subjecting host cells with high-intensity electric pulses to make the cell walls "porous", as described by U.S. Pat. No. 4,910,140. Other methods for transformation of host cells are known by those with skill in the art, such as, but not limited to, introducing transforming DNA into the host cells by means of microinjection. or by encapsidation in a bacteriophage or viral coat, or in a liposome.
Transformation of various types of cells, including different strains of bacterial cells, can be difficult to achieve or very inefficient. The various factors that influence the efficiency of transformation are poorly understood. In order to study and manipulate various types of cells, it is therefore critical to find methods to increase the efficiency of DNA transformation of these cells.
The presence of a restriction and modification system ("R-M system") in a host cell is well known in the art to be an important factor in preventing or reducing the efficiency of transformation by transforming DNA that is unmodified with respect to the R-M system in the host cell. Type I, Type II, and Type III R-M systems are described and discussed and citations are given in review articles by Noreen E. Murray ["Type I Restriction Systems: Sophisticated Molecular Machines (a Legacy of Bertany and Weigle)." Microbiol. Molec. Biol. Rev., 64: 412–434, 2000; "Immigration control of DNA in bacteria: self versus non-self," Microbiology, 148: 3–20, 2002] and Robert Yuan ["Structure and Mechanism of Multifunctional Restriction Endonucleases," Ann. Rev. Biochem., 50: 285–315, 1981], and in the 3rd edition of Sambrook and Russell's Molecular Cloning—A Laboratory Manual, all of which are incorporated herein by reference. Thus, as discussed by Murray [op cif], the DNA in a prokaryotic host cell that has an R-M system is modified so that the cell's own DNA is protected from digestion (or "restriction") by an endonuclease (also referred to as a "restriction enzyme") that is present in the cell, but transforming DNA from another cell which lacks the modification system is not protected from digestion by the endonuclease (if the transforming DNA has one or more sequences which are recognized by the endonuclease as sites for digestion by the endonuclease). The modification enzymes that protect the DNA from digestion are generally DNA methyltransferases which catalyze methylation of specific nucleic acid bases within the target sequence that is digested by the endonuclease. Thus, the modification enzymes block endonuclease digestion of the methylated (or "modified") DNA. As stated by Murray [Microbiol. Molec. Biol. Rev., 64: p. 413, 2000], "Classically, a restriction enzyme is accompanied by it's cognate modification enzyme, and the two comprise a restriction and modification (R-M) system. Most restriction systems conform to this classical pattern. There are, however, some restriction endonucleases that attack DNA only when their target sequence is modified; such modification-dependent restriction enzymes do not, therefore, coexist with a cognate modification enzyme . . . The classical R-M systems and the modification-dependent restriction enzymes share the potential to attack DNA derived from different strains and thereby restrict DNA transfer."
DNA which lacks methyl groups or other modifications which block digestion by the restriction activity portion of an R-M system is referred to as "unmodified" DNA with respect to that R-M system. Unmodified DNA molecules introduced into host cells are often attacked by R-M systems that recognize specific sequences in the DNA and rapidly cleave the DNA into fragments. For example, Type I R-M enzymes are thought to exist in a high percentage of Eubacteria and Archaebacteria, and pose a barrier for entry and establishment of foreign DNA [Murray, N. E., ibid; and Titherage, A. J. B., et al., Nucl. Acids Res., 29: 4195–4205, 2001]. There are many situations in which the modification state of transforming DNA leads to restriction in the recipient host cell [Ando, T. et al., Molec. Microbiol., 37: 1052–1065, 2000]. It would be highly desirable to improve transformation efficiency of such strains having R-M systems.
Many R-M systems are encoded by multiple genes. By way of example, but not of limitation, Type I R-M systems are generally encoded by three genes hsdR, hsdM, and hsdS—which encode three protein subunits, colloquially referred to as "R" (for "restriction"), "M" (for "modification"), and "S" (for "specificity"). These subunits can exist in two kinds of functional complexes in bacteria. An R-M complex with all three subunits (R.sub.2., M.sub.2., S.sub.1.) comprises an R-M system. Another complex, which has only methyltransferase activity and no restriction activity, comprises only two kinds of subunits (M.sub.2., S.sub.1.) and lacks R subunits [See: Murray, N. E., Microbiology, 148: 3–20, 2002]. Type III R-M system have similarities to Type I systems with respect to their molecular structure and other characteristics, whereas Type II R-M systems have separate restriction enzymes (which are the common commercial enzymes used in molecular biology) and methyltransferase modification enzymes [ibid].
Because R-M systems present a barrier to transformation of unmodified DNA, special bacterial strains have been developed for a limited number of organisms which are devoid of the known R-M systems for use in cloning and other applications in which unmodified DNA is used for transformation. Such strains are commonly referred to in the art as being "restriction minus" and the specific genotype of a strain is often presented so as to indicate which R-M system has been deleted or inactivated by mutation in the strain. These restriction minus strains are used as host cells because they do not digest or restrict the unmodified transforming DNA that enters the cells during transformation. By way of example, but not of limitation, an electrocompetent form of an E. coli strain for use in cloning when electroporation is used for transformation is commercially available under the trademarked name of E. coli TransforMax.sup.TM. EC100.sup.TM. (EPICENTRE); this strain is restriction minus and the genotype with respect to the R-M systems is described as "mcrA delta(mrr—hsdRMS—mcrBC)." Since E. coli strain TransforMax.sup.TM. EC10.sup.TM. is restriction minus, and also because the cells have been prepared so as to maximize the electrocompetence of the cell, very high transformation efficiencies are obtained when unmodified transforming DNA is used to transform the cells by electroporation. On the other hand, if unmodified DNA molecules, including, for example, plasmids or other replicons, or transposons, are taken from non-modifying cells or prepared synthetically or by PCR or by other means, and then used to transform competent cells which have an R-M system, such as, for example, cells having a Type I R-M system, the transformation will either be impossible or the transformation efficiency will be greatly reduced. Since it is highly desirable to be able to study and to be able to transform many cells which have an R-M system, including many pathogens and other strains of medical or commercial interest, there is a great need in the art to develop methods for improving transformation of such cells with unmodified DNA. It is therefore highly desirable in the art to find methods to overcome the barrier to transformation of host cells which have an R-M system which digests unmodified transforming DNA.
Many examples are known in which the R-M system barrier to transformation by unmodified phage and conjugative plasmid DNA is overcome by natural means. By way of example, but not of limitation, bacteriophages T7 and T3, which infect enteric bacterial cells, have evolved natural mechanisms to defeat host R-M systems. These bacteriophages produce a polypeptide encoded by the 0.3 ocr gene early in infection, before the remainder of the phage genome is internalized in the host cell, that mimics a DNA molecule; this polypeptide binds to the R-M system and prevents it from binding to DNA substrates, thereby inhibiting restriction activity of the R-M system [Bandyopadhhay, P. K., et al., J. Mol. Biol., 182: 567–578, 1985]. It has been shown that this polypeptide, referred to as "Overcomes Classical Restriction" or "OCR," has a conformation resembling the bent structure of unmodified DNA when it binds to Type I R-M complexes, and that OCR binds the restriction complexes tightly [Atanasiu, O., et al., Nucl. Acids Res., 29: 3059–3068,12, 2001 and Walkinshaw, M. D., et al., Molec. Cell, 9: 187–194, 2002]. Thus, by acting as a molecular "decoy", OCR protein inhibits restriction and prevents destruction of entering bacteriophage DNA.
In addition to phage-encoded inhibitors of restriction activity like the OCR proteins, inhibitors of the restriction activity of R-M systems have also been identified in bacteria which contain naturally-occurring transmissible plasmids, meaning plasmids which can be transferred from one bacterial strain to another by conjugation. By way of example, but not of limitation, it has been reported that certain transmissible plasmids have genes designated ardA, or ardB, or ardC that encode polypeptides called "Ard" for "alleviation of restriction of DNA" which provide general protection against restriction by all Type I R-M systems [Belogurov, A. A., et al, "IncN plamid pKM101 and Incl1 plasmid Col1b-P9 encode homologous anti-restriction proteins in their leading regions," J. Bacteriol., 174: 5079–5085, 1992; Belogurov, A. A., et al., "Plasmid pKM101 encodes two non-homologous anti-restriction proteins (ArdA and ArdB) whose expression is controlled by homologous regulatory sequences," J. Bacteriol., 175: 4843–4850, 1993; Belogurov, A. A., et al., "Antirestriction protein Ard (Type C) encoded by IncW plasmid pSa has a high similarity to the 'protein transport' domain of TraC1 primase of promiscuous plasmid RP4," J. Mol. Biol., 296: 969–977, 2000]. Belogurov et al. reported that, in addition to inhibiting Type I R-M systems, ArdA also inhibits the Type II enzyme EcoRI. Recently, it was reported that, as with T3- and T7-encoded OCR Protein, the ard gene is in the leading edge of the DNA that is transferred into the host cell during conjugation, and, by a using special promoters within secondary structures of single-stranded DNA, it is transcribed into Ard protein prior to entrance of the remaining plasmid DNA into the host cell [Althorpe, N. J., et al., "Transient transcriptional activation of the Incl1 plasmid anti-restriction gene (ardA) and SOS inhibition gene (psiB) early in conjugation," Mol. Microbiol. 31: 133–142, 1999; Bates, S. R., et al., "Expression of leading region genes on Incl1 plasmid Col1b-P9: genetic evidence for single-stranded DNA transcription," Microbiology, 145: 2655–2662, 1999]. It has been proposed that Ard Proteins alleviate restriction of DNA by mimicking the sequences of the specificity ("S") subunits of Type I R-M systems and displace this S subunit from the R-M complex [Belogurov, A. A., and Delver, E. P., "A motif conserved among the type I restriction-modification enzymes and antirestriction proteins: a possible basis for mechanism of action fo plasmid-encoded antirestriction functions," Nucleic Acids Res., 23: 785–787, 1995], but it is also possible that the mechanism is similar to that of OCR Protein.
Other natural mechanisms by which unmodified forms of phages, plasmids and at least one conjugative transposon avoid restriction in host cells having an R-M system in which they would otherwise be degraded are described, discussed and referenced [Murray, N. E., Microbiol. Molec. Biol. Rev., 64: 412–434, 2000 (especially the section entitled "Mechanisms by Which Plasmids and Phages Avoid Restriction" on pp. 425–426); Bickle, T. A. and Kruger, D. H., "Biology of DNA restriction," Microbiol. Rev. 57: 434–450, 1993; and Kruger, D. H. and Bickle, T. A. "Bacteriophage survival: multiple mechanisms for avoiding the deoxyribonucleic acid restriction systems of their hosts," Microbiol. Rev. 47: 345–360,1983], all of which are incorporated herein by reference.
Although it is known in the art that one can increase the transformation efficiency of transforming DNA for a host cell having an R-M system by modifying the restriction sites on the transforming DNA prior to transformation, this is not practical in many cases. For example, one might not know what restriction sites are present on the DNA, what sites on the DNA must be modified to protect it, or how to achieve the desired modification. Also, although some of the R-M systems that are present in a number of E. coli strains have been identified, this is not the case for many other strains of E. coli and definitely is not the case for most other strains of eubacteria and archaebacteria. Noreen Murray has discussed the detection, distribution and diversity of R-M systems [Microbiol. Molec. Biol. Rev., 64: 412–434, 2000 (especially, see pp. 426–430)], incorporated herein by reference. As discussed therein, at least about half of the bacteria in a sequence database had genes that appeared to be Type I-specific R-M genes. More than 1% of the small genome of the medically important bacterium Helicobacter pylori encoded R-M systems, three of which were Type I [Tomb, J. F., et al., "The complete genome sequence of the gastric pathogen Helicobacter pylori," Nature, 388: 539–547, 1997]. It would be difficult to overcome the complex R-M systems of H. pylori by modifying a transforming DNA in order to avoid its restriction by such a host cell. The R-M systems present in most other bacteria of medical, commercial and food importance are not yet defined. Even more challenging is the fact that the actual restriction sites on the DNA of Type I and Type III R-M systems are very difficult to define and identify even after the presence of a R-M system has been shown to be present by screening for R-M genes. Further, the modification enzymes comprising R-M systems from many organisms have not been purified, making it difficult to modify transforming DNA using in vitro treatment with modifying enzymes.
It would be highly desirable to be able to increase the transformation efficiency of many host cells in which the R-M systems have not yet been defined, even if the sequence of the transforming DNA is not known. The present invention provides new and powerful methods for achieving transformation and increasing the transformation efficiency by unmodified DNA for many host cells having an R-M system. These methods do not require prior knowledge of the restriction sites on the unmodified transforming DNA or the restriction specificity of the R-M system. They can be used to increase transformation efficiency of a variety of host cells having R-M systems which restrict unmodified transforming DNA at different sites. The present invention also provides methods for genetically modifying host cells which have an R-M system so they can be transformed by unmodified transforming DNA with higher efficiency. The invention also discloses kits and compositions for carrying out the methods of the invention, or which are made using these methods.

DNA transformation efficiency by inhibiting host cell restriction


A method of generating check matrixes for Low-Density Parity-Check codes includes determination steps of determining a maximum value of a column weight, basic Euclid geometric codes, and a coding rate respectively; a weight searching step of searching an optimum ensemble of a row weight and a column weight at one time according to a linear programming method in a state of a fixed coding rate, and so as to maximize a Gaussian noise; an information calculation step of calculating an information length based on a predetermined block length and the coding rate; a row deletion step of deleting a predetermined row based on the information length using the Euclid geometric codes; and a division step of dividing at random a row or a column of the matrixes after the row deletion in a predetermined order.

FIG. 27 is an illustration of an LDPC encoding/decoding system. This LDPC encoding/decoding system includes an encoder 101, a modulator 102, a channel 103, a demodulator 104, and a decoder 105. Prior to explaining a conventional method of generating check matrixes for LDPC codes, encoding and decoding using LDPC codes will be explained first.
At the sending side, the encoder 101 generates a check matrix H using a certain method, which will be described later, and generates a generator matrix G based on the following conditions:
G: k×n matrix (where k: information length, n: code-word length),
GHT=0 (T denotes transposition).
The encoder 101 then receives a message (m1 m2 . . . mk) of an information length k, and generates a code-word C using the generator matrix G as follows:
                    C        =                                              (                                          m                1                                                          m                2                                                                                …                                                                                m                k                                      )                              G                                        =                                              (                                          c                1                                                          c                2                                                                                …                                                                                c                n                                      )                                                                                (                                          where                                                                                H                                                              (                                                                        c                          1                                                                                c                          2                                                                                …                                                                                c                          n                                                                    )                                                        T                                            =              0                        )
The modulator 102 subjects the generated code-word C to a digital modulation such as BPSK, QPSK or multi-valued QAM and transmits the resultant modulated signal.
At the receiving side, the demodulator 104 receives the modulated signal via the channel 103, and subjects it to a digital demodulation such as BPSK, QPSK or multi-valued QAM. The decoder 105 then subjects the LDPC-coded, demodulated result to an iterative decoding by "Sum-Product Algorithm" and provides an estimated result (corresponding to the original m1 m2 . . . mk).
Conventionally, check matrixes for the LDPC codes are generated as explained below. The check matrix proposed by Gallager, the proposer of the LDPC, is shown in FIG. 28, as an example.
This matrix is a binary matrix of "1" and "0". Parts of "1" are hatched and parts of "0" are white. There are four "1"s in one row (hereinafter, "row weight"), and there are three "1"s in one column (hereinafter, "column weight"). All columns and rows have respective uniform weights. Thus, it is generally called "Regular-LDPC Code". In the Gallager's codes, as shown in FIG. 28, the matrix is divided into three blocks, for example, and the second and third blocks are subjected to random permutation.
Because the random permutation has no certain rule, it is required to execute a time-consuming search by computer to find codes with a better characteristic.
Euclid geometric codes are such LDPC codes that exhibit a relatively stable and nice characteristic and can definitely generate a matrix without the use of the computer search. Y. Kou et al. (Y. Kou, S. Lin, and M. P. C. Fossorier, "Low Density Parity Check Codes Based on Finite Geometries: A Rediscovery," ISIT 2000, pp. 200, Sorrento, Italy, Jun. 25 to 30, 2000. ) have proposed a method using such Euclid geometric codes. This method explains "Regular-LDPC Codes" consisting of regular ensembles.
A method of generating a check matrix for LDPC codes is herein proposed using Euclid geometric codes EG (2, 26) or a kind of finite geometric codes. This method achieves a characteristic that is located closely but 1.45 decibels away from the Shannon limit at an error rate of 10−4. FIG. 29 is an illustration of the Euclid geometric codes EG (2, 22), which has a structure of "Regular-LDPC Codes" with row and column weights of 4, 4.
Euclid geometric codes EG (m, 2s) have a characteristic defined as follows:
Code length: n=22s−1
Redundant bit length: n−k=3s−1
Information length: k=22s−3s
Minimum distance: dmin=2s+1
Density: r=2s/(22s−1)
As can be seen from FIG. 29, the Euclid geometric codes have a structure with a location of "1" in each row shifted periodically from that in an adjacent row. It is a characteristic of this structure that it can configure codes easily and definitely.
The method of generating check matrix proposed by Y. Kou et al. further includes changing row and column weights based on the Euclid geometric codes to extend rows and columns, if required. For example, when a column weight in EG (2, 22) is separated into halves, in the method of Y. Kou et al., every other one of four weights located in one column is separated into two groups. FIG. 30 is an illustration of an exemplary regular separation of the column weight from 4 into 2.
Ludy et al. (M. G. Luby, M. Mitzenmacher, M. A. Shokrollahi, and D. A. Spielman, "Improved Low-Density Parity-Check Codes Using Irregular Graphs and Belief Propagation," Proceedings of 1998 IEEE International Symposium on Information Theory, pp. 171, Cambridge, Mass., Aug. 16 to 21, 1998. ) have reported that "Irregular-LDPC Codes" have a better characteristic than that of "Regular-LDPC Codes". The "Irregular-LDPC Codes" represent such LDPC codes that have non-uniformity in either or both of row and column weights.
Richardson et al. (T. J. Richardson and R. Urbanke, "The capacity of low-density parity-check codes under message-passing decoding," IEEE Trans. Inform. Theory, vol. 47, No. 2, pp. 599 to 618, February 2001. ) have analyzed it theoretically as well as Chung et al. (S.-Y. Chung, T. J. Richardson, and R. Urbanke, "Analysis of Sum-Product Decoding of Low-Density Parity-Check Codes Using a Gaussian Approximation," IEEE Trans. Inform. Theory, vol. 47, No. 2, pp. 657 to 670, February 2001. )
In particular, Chung et al. have analyzed a "Sum-Product Algorithm" for LDPC codes, on the assumption that a Log Likelihood Ratio (hereinafter, "LLR") between an input and an output at an iterative decoder can be approximated in a Gaussian distribution, to derive a nice ensemble of row and column weights.
In the conventional method of generating check matrixes for LDPC codes by Chung et al., however, the number of "1" points in a row (corresponding to a degree distribution of variable nodes later described) and the number of "1" points in a column (corresponding to a degree distribution of check nodes later described) are both employed as variables to derive the degree distribution of variable nodes and the degree distribution of check nodes that can maximize the following equation (1) (rate: coding rate). In a word, a linear programming is employed to search an ensemble that minimizes a Signal to Noise Ratio (hereinafter, "SNR").
                    rate        =                  1          -                                                    ∫                0                1                                                          ρ                                                  (                  x                  )                                                                                ∫                0                1                                                          λ                                                  (                  x                  )                                                                                (        1        )
Therefore, a problem arises because a check matrix derived from the maximum of the "rate" has a flux and unstable characteristic. In addition, the conventional method of generating check matrixes for LDPC codes iteratively executes the derivation of the degree distribution of variable nodes and the derivation of the degree distribution of check nodes over certain times. Therefore, a problem arises that it takes a time to some extent for searching.
It is an object of the present invention to solve at least the problems in the conventional technology.

LDPC code inspection matrix generation method and inspection matrix generation device


A single program descriptor is assigned to each program in electronic programming guide (EPG) data which is transmitted to home communications terminals in a communications network. A relationship is then separately established between these descriptors and criteria which may be used by a subscriber to search the EPG data for programs of interest to that subscriber. Data for defining this relationship is also stored in the home communications terminal. The subscriber may then provide one or more of the above-mentioned criteria to search the EPG data for programs meeting the criteria. The programs which are determined to meet the criteria may be displayed on the television of the subscriber.

1. Technical Field
The present invention generally relates to methods and apparatus for organizing and searching a database and, more particularly, to methods and apparatus for organizing and searching an electronic programming guide.
2. Description of Related Art
It is known in the art to provide an electronic program guide (EPG) which provides the viewer with an on-screen listing of the upcoming television programs on television channels available to the viewer. In one implementation, the EPG is provided by an EPG data service and the EPG data is converted into a video signal at the cable head end and transmitted to the viewer's television via a dedicated cable television channel. After tuning to the dedicated cable television channel, the viewer must then passively wait until the program information for the desired time period and/or channel is displayed. This technique provides no mechanism for allowing the viewer to scroll through the EPG to the desired listing. Moreover, this technique also requires the cable head end operator to dedicate a separate cable television channel to the EPG data and to create video signals from the EPG data provided by the EPG service provider.
In another implementation, the EPG data is transmitted to subscribers using either in-band or out-of-band signaling. The subscriber's home communication terminal recovers the EPG data and stores the data until the subscriber requests presentation of the EPG data on his/her television. Upon selection of the EPG data, the EPG is displayed on the subscriber's television overlaid on or in place of the video programming. Since the EPG is stored locally at the subscriber's television, the subscriber may scroll through the program information in the EPG until the desired listing is reached.
When implementing such an EPG, it is useful to attach descriptors to each program. Typical descriptors (also referred to as "categories") include "movies", "sports", "comedy", and "western", as well as many others. The subscriber may display a list of programs which is limited to those programs matching a specified descriptor. FIG. 1 is a list of categories which includes "movies", "sports", and "comedy". Each of these categories has one or more subcategories. For example, "all", "action", "comedy", and "western" are subcategories of the main category "movies" and "all", "movie", and "sitcom" are subcategories of the main category "comedy". A program such as "Blazing Saddles" would appear under the categories movies:all; movies:comedy; movies:western; comedy:all; and comedy:movies. This may be implemented by assigning to "Blazing Saddles" the descriptors "movies", "comedy" and "western", and then placing the program in those categories which intersect with one of the descriptors. However, assigning each program to a plurality of categories increases the amount of data which must be transmitted to subscribers. While the data to be transmitted can be reduced by requiring that each program be assigned to at most one category, such an arrangement limits the flexibility with which a subscriber may search the EPG to find programs of interest. Accordingly, it would be desirable to provide methods and apparatus which minimize the amount of information which must be transmitted to subscribers, but nonetheless provides flexibility for searching the EPG to find programs.

Methods and apparatus for organizing and searching an electronic programming guide


Methods and apparatuses are disclosed that determine whether to feedback, and the amount of feedback, with respect to eigenbeam information based upon channel resources. Additionally, methods and apparatuses are disclosed that determine whether to feedback, and the amount of feedback, with respect to eigenbeam information based upon channel information and changes in channel information.

I. Field
The present document relates generally to wireless communication and amongst other things to eigen-beam forming for wireless communication systems.
II. Background
An orthogonal frequency division multiple access (OFDMA) system utilizes orthogonal frequency division multiplexing (OFDM). OFDM is a multi-carrier modulation technique that partitions the overall system bandwidth into multiple (N) orthogonal frequency subcarriers. These subcarriers may also be called tones, bins, and frequency channels. Each subcarrier is associated with a respective sub carrier that may be modulated with data. Up to N modulation symbols may be sent on the N total subcarriers in each OFDM symbol period. These modulation symbols are converted to the time-domain with an N-point inverse fast Fourier transform (IFFT) to generate a transformed symbol that contains N time-domain chips or samples.
In a frequency hopping communication system, data is transmitted on different frequency subcarriers during different time intervals, which may be referred to as "hop periods." These frequency subcarriers may be provided by orthogonal frequency division multiplexing, other multi-carrier modulation techniques, or some other constructs. With frequency hopping, the data transmission hops from subcarrier to subcarrier in a pseudo-random manner. This hopping provides frequency diversity and allows the data transmission to better withstand deleterious path effects such as narrow-band interference, jamming, fading, and so on.
A problem in most communication systems is that the receiver is located in a specific portion of an area served by the access point. In such cases, where a transmitter has multiple transmit antennas, the signals provided from each antenna need not be combined to provide maximum power at the receiver. In these cases, there may be problems with decoding of the signals received at the receiver. One way to deal with these problems is by utilizing beamforming.
Beamforming is a spatial processing technique that improves the signal-to-noise ratio of a wireless link with multiple antennas. Typically, beamforming may be used at either the transmitter or the receiver in a multiple antenna system. Beamforming provides many advantages in improving signal-to-noise ratios which improves decoding of the signals by the receiver.
Certain types of OFDMA systems are frequency division duplexed (FDD) OFDMA systems. In these FDD OFDMA systems, the transmission from the access point to the access terminal and from the access terminal to the access point occupy different distinct frequency bands. In FDD OFDMA systems feedback to perform beamforming generally requires knowledge of the channel at the transmitter, e.g. access point, which is not available without substantial feedback. This feedback, generally in the form of the actual beamforming weights or vectors, requires a large amount of resources on control or signaling channels. This reduces data rates and increases the overhead required.
Therefore, it is desired that systems provide feedback for more accurate beamforming while minimizing the resources needed to provide the feedback from the receiver to the transmitter.

Systems and methods for beamforming feedback in multi antenna communication systems


The present invention relates to a heat exchanger system for incorporation in a deodorizer. The heat exchanger system comprises longitudinal heat transfer means, inlet distribution headers, outlet collector headers, spacers having holes to support the longitudinal heat transfer means, a compensator, and two or more support devices. The longitudinal heat transfer means are guided through the holes of the spacers and arranged in bundles, and each of the bundles is attached to an inlet distribution header as well as to an outlet collector header, and at least some of the spacers are mounted on at least one support device. The present invention relates also to a semi-continuous deodorizer having one or more of such heat exchanger systems, and to a use of the deodorizer.

Deodorizing of edible fats and oils is an important step in the refining process. One deodorizer design class includes a vacuum vessel containing a plurality of vertically stacked trays, in which the oil consecutively is transferred from tray to tray. A sub class of the tray-based deodorizer type is operating in semi-continuous mode where the batch of oil residing in a tray is kept as a separate entity during the transferring to other trays. This semi-continuous mode allows for stock change without interrupting the operation, but induces instantaneous and significant material temperature changes at the time of batch-switch.
In deodorizers of tray-based semi-continuous type the heating or cooling of the oil is suitably executed in dedicated trays where heat exchanging coils are arranged in zones for heating and cooling. The heat exchanger coils of the current state of art are either of helical or of serpentine design. The spiral coil design inevitably leads to an empty space in the centre, in which no heat transfer area exist, this is negatively affecting which total heat transfer surface area which can be installed. Furthermore, the structure of the heat exchanger is quite rigid, leading to material fatigue and eventually coil crack due to the thermally induced expansion or contraction derived from frequent switching of oil batches of different temperatures.


According to an exemplary embodiment, a circuit includes a power amplifier configured to generate an RF output signal. The circuit further includes a pulse shaping circuit coupled to the power amplifier, where the pulse shaping circuit is configured to receive a digital input signal and generate an analog output signal at a first node, and where the analog output signal controls the RF output signal. The analog output signal has a ramp-up portion having a first shape, where the first shape corresponds to a piece-wise-linear approximation of a sinusoid. The analog output signal also has a ramp-down portion having a second shape, where the second shape corresponds to the piece-wise-linear approximation of a sinusoid. The pulse shaping circuit does not require a clock reference to generate the analog output signal.

1. Field of the Invention
The present invention is generally in the field of electrical circuits. More specifically, the invention is in the field of power amplifiers.
2. Related Art
Wireless communication devices, such as wireless communication system using time-division multiplexing ("TDM") communication standard, transmit information in power bursts, which are generated by pulsing a power amplifier. These systems require pulse shaping to minimize undesirable switching transients, which can occur when the power amplifier output is abruptly ramped up to a high power level at the beginning of the power burst and abruptly ramped down at the end of the power burst. The shape of the transmit pulse, i.e. the power burst, can be controlled by adjusting the gain of the power amplifier as a function of time, for example.
In a typical conventional approach, a digital-to-analog converter ("DAC") is used to control the power amplifier gain and construct a desired pulse shape. However, since the DAC control is digital in nature, it, i.e. the DAC control, requires memory space and clocked reference signals, which can generate undesirable harmonic energy that can interference with radio frequency ("RF") signals in the power amplifier. Also, the DAC generates a stepped output that must be filtered to eliminate undesirable spectrum content, which is caused by the discrete nature of the DAC output waveform.
Additionally, significant differences exist in the gain control characteristics of power amplifiers provided by different vendors as well as from different generations of power amplifiers. Also, since the DAC and power amplifier are typically provided by a different vendor than the power amplifier, the waveform that comes out of the DAC is not necessarily compatible with the waveform required to drive the power amplifier. As a result, the DAC output waveform must be modified to meet the particular requirements of each power amplifier.
Thus, there is a need in the art for an effective pulse shaping circuit for a power amplifier in a wireless communication system, such as a TDM system.

Clockless pulse shaping circuit for controlling a power amplified output


Embodiments of the invention control a recovery procedure effectively in accordance with write conditions. In one embodiment, the data to be written into a sector includes not only user data but also recording condition data, which indicates the temperature prevalent during a write. If a data read is not accurately performed, a recovery procedure is executed. If a data read is accomplished by a retry and the temperature prevalent during a write is lower than predetermined, it is concluded that the employed medium is nondefective. Thus, the read data is rewritten into the same sector without being stored in a spare area. This prevents the spare area from being unnecessarily consumed.

The present invention relates to a media drive, a processing method for recording data onto a medium, a processing method for data read from a medium, and a method for controlling a process for reading data from a medium, and more particularly to a magnetic disk recording/reproducing apparatus.
Various devices using optical disks, magnetic tapes, and other media are known as information recording/reproducing apparatus devices. Among others, a hard disk drive is now widely used as a storage device for use with a computer and considered an essential storage device for a present-day computer system. Due to its excellent characteristics, the hard disk drive have found an increasingly wide range of applications, including not only a computer but also a motion picture recording/reproducing apparatus, a car navigation system, a removable memory for use with a digital camera, and the like.
A magnetic disk or other recording medium for use with a hard disk drive contains a plurality of concentric tracks. Each track is divided into a plurality of sectors. Each sector stores the sector's address information and user data. A head of the hard disk drive accesses a target sector in accordance with the sector's address information so that data can be written into the sector and read from the sector.
In a process for reading a medium, for instance, data may not accurately be read at all times. If the hard disk drive cannot accurately read data in a normal read mode, it initiates a recovery procedure. The recovery procedure changes a parameter for a read process and then retries a read. The retry operation is repeated while the parameter value is varied. The retry operation terminates if the data cannot accurately be read after it has been repeated a predetermined number of times. The parameter to be changed may be, for instance, a head position, an amplifier gain for A/D conversion on a channel, or a digital filter parameter value.
In a conventional hard disk drive, parameter changes for a retry operation are made according to pre-established rules. For example, the parameter change rules are determined as described below. For a first retry operation, the first parameter is changed by a specified amount. For a second retry operation, the second parameter is changed by a specified amount. To reduce the number of retry operations, a conventional, typical recovery procedure uses statistical data.
In an assurance test for an outgoing inspection, for example, a retry operation is repeated while all the parameter values are varied to acquire statistical data about the retry count. When retry conditions under which an accurate read operation is performed with a statistically high probability are used initially for recovery procedure execution purposes, it can be expected that the retry count may be decreased to a certain extent. However, the optimum read conditions vary with the write conditions for a data write into the target sector. Therefore, it is difficult for the above retry control, which is based on statistical data, to produce a satisfactory effect.
If, on the other hand, the recovery procedure concludes that a target sector is defective, the data in that sector is rewritten in a spare area of the magnetic disk. The spare area has a plurality of spare sectors for storing user data in place of a defective user sector. A defective sector is reassigned to one spare sector. Spare sector management is exercised by referencing a management table, which is called a defect map.
Various data registration methods are proposed for the use of a defect map (refer, for instance, to Japanese Patent Laid-open No. 2002-268829. Typically, the defect map has data that associates defective sector numbers with spare sector numbers. In a process, for instance, for generating CHS numbers (cylinder number, head number, and sector number), which constitute the parameter information for specifying a sector position from a logical address for a data read, firmware references the defect map so that a logical address corresponding to a defective sector is converted to a corresponding spare address. A spare sector can then be accessed using the logical address corresponding to the defective sector.
If a predetermined retry count is exceeded for data read purposes, the target sector is generally classified as defective so that a spare process is performed. However, spare sectors are formed in an area different from an area for normal user sectors. Therefore, spare sectors are accessed with a delay so as to lower the read/write transfer rate of the hard disk drive. This may result, for instance, in a decrease in the data read speed and deterioration in display quality for motion picture playback.
If a retry operation needs to be repeated multiple times due to incompletely recorded data, the problem may be attributable to a defect in the employed medium or data write conditions such as the temperature and head position for a data write. If the problem is caused by such data write conditions and not caused by the employed medium, spare sectors, which are held in reserve for a specific purpose, are used by an unnecessary spare process although the medium itself has no problem at all.

Media drive, processing method for recording data onto a medium, processing method for data read from a medium, and method for controlling a process for reading data from a medium

Hitachi Global Storage Technologies Netherlands B.V.


A method, a device, and a storage medium having instructions stored thereon to obtain usage data that indicates a usage of a downloading service and a streaming service of programs, in which the programs are provided to user devices via unicast delivery. The usage data is analyzed to determine whether a multicast offloading or a broadcast offloading is to be invoked on behalf of a program designated for unicast delivery. Additionally, a method, a device, and a storage medium obtain usage data, analyze the usage data, and generate a recommendation for an infrastructural change of a content delivery network based on the analysis.

Streaming and downloading of programs is a popular delivery mechanism for providing programs to users. A content delivery network (CDN) (also known as a content distribution network) is typically used for streaming and/or downloading programs. The content delivery network includes a server that stores programs and services other servers. The other servers cache programs and stream and/or download the programs to users.

Broadcast/multicast offloading and recommending of infrastructural changes based on usage tracking


The present invention provides a light-emitting organic platinum complex, a light-emitting material containing with complex, and a functional device containing this complex. The light-emitting organic platinum complex is represented the following structural formula or other formulae as described herein.

An organometallic complex emits phosphorescent light that can be, in organic EL (electroluminescence), theoretically higher in quantum efficiency than fluorescent light. This makes organometallic complexes promising as a material (specifically, as a material for an organic EL display) for a functional device such as an organic light-emitting element, which represents a next-generation technique. Currently, however, there is a demand for improvement in such aspects of organometallic complexes as life, heat resistance, and efficiency achieved when there has been an increase in current. Further, an organometallic complex, in order to be used in a functional device, needs to produce all the three primary colors (red, green, and blue) of light.
Recent years have witnessed various organometallic complexes being proposed each of which is useful as a material for a functional device. Patent Literature 1, for example, discloses a metalloporphyrin complex including a metal such as platinum and having a cross-linked structure. Patent Literature 2 discloses an organometallic complex including (i) a metal such as iridium and platinum and (ii) a heterocyclic compound as a ligand.

Light-emitting organic platinum complex, light-emitting material containing this complex and functional device


The invention relates to novel 7ß-hydroxysteroid dehydrogenase mutants, to the sequences which encode these enzyme mutants, to processes for the preparation of the enzyme mutants and to their use in enzymatic reactions of cholic acid compounds, in particular in the preparation of ursodeoxycholic acid (UDCS). The invention also relates to novel processes for the synthesis of UDCS using the enzyme mutants; and to the preparation of UDCS using recombinant, multiply-modified microorganisms.

The active substances ursodeoxycholic acid (UDCA) and the related diastereomer chenodeoxycholic acid (CDCA), among others, have been used for many years for the drug treatment of gallstone disease. The two compounds differ only in the configuration of the hydroxyl group on carbon atom 7 (UDCA: β-configuration, CDCA: α-configuration). Various processes are described in the prior art for the preparation of UDCA, which are carried out purely chemically or consist of a combination of chemical and enzymatic process steps. The starting point is in each case cholic acid (CA) or CDCA prepared from cholic acid.
Thus, the classical chemical method for UDCA preparation can be represented schematically as follows:

A serious disadvantage is, among other things, the following: as the chemical oxidation is not selective, the carboxyl group and the 3α and 7α-hydroxyl group must be protected by esterification.
An alternative chemical/enzymatic process based on the use of the enzyme 12α-hydroxysteroid dehydrogenase (12α-HSDH) can be represented as follows and is for example described in PCT/EP2009/002190 of the present applicant.

The 12α-HSDH oxidizes CA selectively to 12-keto-CDCA. The two protection steps required according to the classical chemical method are then omitted.
Furthermore, Monti, D., et al., (One-Pot Multienzymatic Synthesis of 12-Ketoursodeoxycholic Acid: Subtle Cofactor Specificities Rule the Reaction Equilibria of Five Biocatalysts Working in a Row. Advanced Synthesis & Catalysis, 2009) describe an alternative enzymatic-chemical process, which can be represented schematically as follows:

The CA is first oxidized from 7α-HSDH from Bacteroides fragilis ATCC 25285 (Zhu, D., et al., Enzymatic enantioselective reduction of -ketoesters by a thermostable 7-hydroxysteroid dehydrogenase from Bacteroides fragilis. Tetrahedron, 2006. 62(18): p. 4535-4539) and 12α-HSDH to 7,12-diketo-LCA. These two enzymes are each NADH-dependent. After reduction by 7β-HSDH (NADPH-dependent) from Clostridium absonum ATCC 27555 (DSM 599) (MacDonald, I. A. and P. D. Roach, Bile induction of 7 alpha- and 7 beta-hydroxysteroid dehydrogenases in Clostridium absonum. Biochim Biophys Acta, 1981. 665(2): p. 262-9), 12-keto-UDCA is formed. The end product is obtained by Wolff-Kishner reduction. This method has the drawback that owing to the position of the equilibrium of the catalyzed reaction, a complete reaction is not possible, and that for the first step of the reaction it is necessary to use two different enzymes, which makes the process more expensive. For cofactor regeneration, lactate dehydrogenase (LDH; for regeneration of NAD+) and glucose dehydrogenase (GlcDH or GDH, for regeneration of NADPH) are used. A disadvantage with the cofactor regeneration used there is that the resultant co-product can only be removed from the reaction mixture with great difficulty, so that the reaction equilibrium cannot be influenced positively, which results in incomplete reaction of the educt.
A 7β-HSDH from the strain Collinsella aerofaciens ATCC 25986 (DSM 3979; formerly Eubacterium aerofaciens) was described in the year 1982 by Hirano and Masuda (Hirano, S. and N. Masuda, Characterization of NADP-dependent 7 beta-hydroxysteroid dehydrogenases from Peptostreptococcus productus and Eubacterium aerofaciens. Appl Environ Microbiol, 1982. 43(5): p. 1057-63). Sequence information for this enzyme was not disclosed. The molecular weight determined by gel filtration was 45 000 Da (cf. Hirano, page 1059, left column). Furthermore, for the enzyme there, the reduction of the 7-oxo group to the 7β-hydroxyl group was not observed (cf. Hirano, page 1061, Discussion 1st paragraph). A person skilled in the art can therefore see that the enzyme described by Hirano et al. is not suitable for catalysis of the reduction of dehydrocholic acid (DHCA) in position 7 to 3,12-diketo-7β-CA.
The applicant's earlier international patent application PCT/EP2010/068576 describes a novel 7β-HSDH from Collinsella aerofaciens ATCC 25986, which among other things has a molecular weight (in SDS-gel electrophoresis) of about 28-32 kDa, a molecular weight (in gel filtration, in nondenaturing conditions, such as in particular without SDS) from about 53 to 60 kDa, and the capacity for stereoselective reduction of the 7-carbonyl group of 7-keto-LCA to a 7β-hydroxyl group.
In addition, in PCT/EP2010/068576, a process is provided for the preparation of UDCA, which can be represented schematically as follows:

In this case the oxidation of CA takes place simply, by a classical chemical route. DHCA is reduced by the pair of enzymes 7β-HSDH and 3α-HSDH individually in succession or in one pot to 12-keto-UDCA. Combined with Wolff-Kishner reduction, UDCA can therefore be synthesized from CA in just three steps. 7β-HSDH is dependent on the cofactor NADPH, whereas 3α-HSDH requires the cofactor NADH. The availability of pairs of enzymes with dependence on the same cofactor or extended dependence (e.g. on the cofactors NADH and NADPH) would be advantageous, because this could simplify cofactor regeneration.
The problem to be solved by the invention is to provide further improved 7β-HSDHs. In particular, enzyme mutants should be provided, which can be used even more advantageously for enzymatic or microbial preparation of UDCA via the stereospecific reduction of DHCA in 7-position to 3,12-diketo-7β-CA, and in particular have reduced substrate inhibition and/or have altered cofactor usage (increased, altered specificity or extended dependence).
Another problem is to provide novel enzymatic and microbial synthesis routes, which in particular are also characterized by simplified cofactor regeneration in the reductive preparation of UDCA via DHCA.

This patent is subject to a terminal disclaimer.

7Beta-hydroxysteroid dehydrogenase mutants and process for the preparation of ursodeoxycholic acid


A pad part of a semiconductor device includes a semiconductor substrate having a pad forming region; a plurality of dot type stack patterns with a dielectric layer and a conductive layer for option capacitors, formed in the pad forming region and arranged at regular intervals; a first interlayer dielectric formed on the semiconductor substrate to cover the stack patterns; first metal lines formed on the first interlayer dielectric to be connected to the stack patterns arranged in diagonal directions; a second interlayer dielectric formed on the first interlayer dielectric to cover the first metal lines; second metal lines formed on the second interlayer dielectric to be brought into contact with the first metal lines; a pad formed on the second interlayer dielectric; and option metal lines formed on the second interlayer dielectric to connect the second metal lines and the pad to each other.

The present invention relates to a pad part of a semiconductor device, and more particularly, to a pad part of a semiconductor device that has option capacitors for the fine adjustment of capacitance between pins.
In general, a pin in a semiconductor package indicates a lead, which is connected to a pad of a semiconductor chip, and functions to electrically connect the semiconductor chip to an external substrate.
A typical example of a semiconductor package generally known in the conventional art is shown in FIG. 1.
FIG. 1 is a cross-sectional view illustrating a conventional semiconductor package. Referring to FIG. 1, a semiconductor chip 10 is attached to a die paddle 12 by an adhesive (not shown), and inner leads 14a are electrically connected to the pads 11 of the semiconductor chip 10 by metal wires 13. The semiconductor chip 10, the die paddle 12, the metal wires 13, and the inner leads 14a are molded using a molding material (not shown), such as an epoxy molding compound (EMC). Outer leads 14b, which project out of the molding material, are connected to the electrode terminals of the substrate, such as a printed circuit board (PCB). The reference numeral 15 designates a lead frame.
In the semiconductor package, the leads 14a and 14b connected to the pads 11 of the semiconductor chip 10 have different capacitance values due to: first, a difference in the doping concentration between junction areas, and a difference in the thickness between gate electrodes, etc.; and, second, a difference in the lengths and widths of the metal wires 13 and the leads 14a and 14b connected to the respective pads 11.
The different capacitance between pins creates variances in signal transmission times, and this problem is regarded as significant impediment against the trend toward high speed operations of the highly integrated components of the semiconductor device.
Therefore, the development of new manufacturing methods has focused on methods of reducing the capacitance-difference between pins. In the conventional art, option transistors are formed adjacent to the pads or option capacitors are formed under the pads.
Separate transistors can be formed in electrostatic discharge (ESD) elements connected to pads to function as option transistors. The capacitance values between pins can be adjusted by varying the number of option transistors that are connected to the respective pads.
Regarding the option capacitors formed under the pads, a gate oxide layer pattern acting as a dielectric layer and a gate conductive layer pattern acting as an upper electrode are sequentially formed in the pad region of the semiconductor substrate when forming gates in a cell region. The option capacitors, each of which comprising a stack of substrate, gate oxide layer, and gate conductive layer, are formed. The capacitance values between pins is adjusted by connecting the requisite number of option capacitors to the respective pads in the same manner as described above.
The methods of forming the option transistors and forming the option capacitors may be used together. In general, the capacitance change rate by the option capacitors is relatively finer when compared to a capacitance change rate by the option transistors.
FIG. 2 shows a layout of a conventional semiconductor device in which option capacitors are formed under pads.
Referring to FIG. 2, conventional stack patterns 250 for option capacitors are formed under the pad 280 of a semiconductor device. Each stack pattern 250 has the sectional shape of a bar with the major axis extending in the direction of the "X-axis" as shown in FIG. 2. The stack patterns 250 are parallel to each other and spaced at regular intervals. The stack patterns 250 for option capacitors are connected to the pad 280 through first metal lines M1, second metal lines M2, and option metal lines O/M. The second metal lines M2, the option metal lines O/M and the pad 280 are formed on the same layer.
In FIGS. 2-3, reference numeral 200 designates a quadrangular semiconductor substrate; M1C designates first contacts that connect the stack patterns 250 for option capacitors and the first metal lines M1 to each other; M2C designates second contacts that connect the first metal lines M1 and the second metal lines M2 to each other; and 220 designates a pick-up that is shaped like a picture frame and surrounds the quadrangular pad part. The pick-up 220 is connected to a ground line (VSS) and functions to apply a bias to the pad part of the semiconductor device although this connection is not shown in FIG. 3.
FIG. 3 is a cross-sectional view taken along the line a-a′ of FIG. 2. The pad part of the semiconductor device having the conventional option capacitors includes the semiconductor substrate 200 with a pad forming region; an isolation structure 210 located in the pad forming region of the semiconductor substrate 200; the stack patterns 250 for option capacitors, each of which is shaped like a bar and comprises a stack of a gate insulation layer 230 and a gate conductive layer 240; a first interlayer dielectric 260 that covers the stack patterns 250 for option capacitors' the first contacts M1C, which are formed in the first interlayer dielectric 260, that contact the stack patterns 250 for option capacitors; the first metal lines M1 formed on the first interlayer dielectric 260 and connected to the first contacts M1C; a second interlayer dielectric 270 formed on the first interlayer dielectric 260 that covers the first metal lines M1; the second contacts M2C formed in the second interlayer dielectric 270 that contact the first metal lines M1; the second metal lines M2 formed on the second interlayer dielectric 270 that connect to the second contacts M2C; and the option metal lines O/M that connect the second metal lines M2 and the pad 280 to each other.
In the pad part of the semiconductor device constructed as described above, if a bias is applied to the gate conductive layer 240 and the pick-up 220, the semiconductor substrate 200, the isolation structure 210, the gate insulation layer 230, and the gate conductive layer 240 serve as a capacitor. At this time the capacitance value varies depending upon the number of stack patterns 250 for option capacitors that are connected to the pad 280 by the option metal lines O/M and the size of each stack pattern 250 for option capacitors.
In this regard, a finely tuned method for adjusting capacitance between pins is needed for a highly-integrated and high-speed semiconductor device due to the decrease in the desired pin capacitance and delta capacitance (ΔC).
However, in the conventional method for adjusting capacitance between pins, which uses the option capacitors as described above, since the capacitance adjustment rate by the option capacitors reaches several tens farads (F), it is difficult to finely adjust capacitance.

Pad part of semiconductor device having optimal capacitance between pins


A laminated nozzle assembly is provided. The laminated nozzle includes a first end plate having a first fluid inlet and a second fluid inlet, a second end plate, a plurality of nozzle plates positioned and clamped between the first end plate and the second end plate, a first fluid conduit in fluid communication with the first fluid inlet formed in one or more of the nozzle plates, a second fluid conduit in fluid communication with the second fluid inlet formed in one or more of the nozzle plates, a first orifice in fluid communication with the first fluid conduit formed in one of the nozzle plates, and a second orifice in fluid communication with the second fluid conduit formed in the same nozzle plate as the first orifice. The laminated nozzle assembly minimizes the number of nozzle plates and includes no more than eight, and preferably no more than five nozzle plates.

The following description relates to a laminated nozzle assembly having one or more thick plates.
A laminated nozzle assembly may be used to discharge a hot melt adhesive onto a substrate. The substrate may be, for example, a layer of material, such as a nonwoven fabric, or a strand of material, such as an elastic strand to be applied on an article, such as a disposable hygiene product. The laminated nozzle assembly may include one or more first orifices for discharging the hot melt adhesive and one or more second orifices configured to discharge air. The discharged air causes the discharged hot melt adhesive to oscillate or vacillate during application to the substrate.
FIG. 1 shows a partial exploded view of a conventional laminated nozzle assembly 10. Referring to FIG. 1, a conventional laminated nozzle assembly 10 includes a plurality of plates having internal conduits formed therein allowing flow of the hot melt adhesive and air therethrough. FIG. 2 is a plan view of the individual plates forming the conventional laminated nozzle assembly 10. Referring to FIGS. 1 and 2, the conventional laminated nozzle assembly may include eleven plates 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32 secured between a first end plate 34 and a second end plate 36. A first internal conduit 38 may be formed through a plurality of the plates for delivering the hot melt adhesive to a first orifice 40. The first conduit 38 is formed by a plurality of aligned openings in the plates. A second internal conduit 42 may also be formed through a plurality of the plates for delivering the air to a second orifice 44. The second conduit 42 is formed by a plurality of aligned openings in the plates.
However, in the conventional laminated nozzle assembly 10, the fluid may collect in various portions of the conduits 38, 42, and in the case of the hot melt adhesive, may lead to plugging of the first conduit. Fluid collection may be the result of narrow or small flow paths, indirect flow paths that cause the velocity of a fluid to be reduced, or excess contact with the sidewalls of a conduit (i.e., the portions of the plates surrounding the openings forming the conduits).
Moreover, when the chemistry and manufacturing of the discharged material (e.g., the adhesive) is not well controlled, contaminants may be present in the material and charring may occur at what are otherwise normal operating temperatures. The existence of contaminants, char products and residue can further exaggerate the plugging of the conduits.
Accordingly, it is desirable to provide a laminated nozzle assembly having an internal conduit or conduits allowing for increased passageway size, higher fluid velocity, and more direct flow paths to the discharge orifices.