284 research outputs found
A reconfigurable TDMP decoder for raptor codes
No full textA Raptor code is a concatenation of a fixed rate precode and a Luby-Transform (LT) code that can be used as a rateless error-correcting code over communication channels. By definition, Raptor codes are characterized by irregularity features such as dynamic rate, check-degree variability, and joint coding, which make the design of hardware-efficient decoders a challenging task. In this paper, serial turbo decoding of architecture-aware Raptor codes is mapped into sequential row processing of a regular matrix by using a combination of code enhancements and architectural optimizations. The proposed mapping approach is based on three basic steps: (1) applying systematic permutations on the source matrix of the Raptor code, (2) confining LT random encoding to pseudo-random permutation of messages and periodic selection of rowsplitting scenarios, and (3) developing a reconfigurable parallel check-node processor that attains a constant throughput while processing LT- and LDPC-nodes of varying degrees and count. The decoder scheduling is, thus, made simple and uniform across both LDPC and LT decoding. A serial decoder implementing the proposed approach was synthesized in 65 nm, 1.2 V CMOS technology. Hardware simulations show that the decoder, decoding a rate-0.4 code instance, achieves a throughput of 36 Mb-s at SNR of 1.5 dB, dissipates an average power of 27 mW and occupies an area of 0.55 mm 2. © Springer Science+Business Media, LLC 2012.Elias P, 1955, 3 LOND S, P61; Etesami O, 2006, IEEE T INFORM THEORY, V52, P2033, DOI 10.1109-TIT.2006.872855; Fossorier MPC, 1999, IEEE T COMMUN, V47, P673, DOI 10.1109-26.768759; Gallager R., 1963, LOW DENSITY PARITY C; Kai Zhang X. H., 2009, IEEE T VERY LARGE SC, V27, P985; Luby M, 2002, ANN IEEE SYMP FOUND, P271; Mansour MA, 2006, IEEE T SIGNAL PROCES, V54, P4376, DOI 10.1109-TSP.2006.880240; Mansour MM, 2003, IEEE T VLSI SYST, V11, P976, DOI 10.1109-TVLSI.2003.817545; Palanki R., 2004, Proceedings. 2004 IEEE International Symposium on Information Theory (IEEE Cat. No.04CH37522); Shokrollahi A, 2006, IEEE T INFORM THEORY, V52, P2551, DOI 10.1109-TIT.2006.874390; TANNER RM, 1981, IEEE T INFORM THEORY, V27, P533, DOI 10.1109-TIT.1981.1056404; Xiang B, 2010, IEEE T VLSI SYST, V18, P1447, DOI 10.1109-TVLSI.2009.2025169; Zeineddine H, 2011, IEEE T SIGNAL PROCES, V59, P2943, DOI 10.1109-TSP.2011.21146550
A turbo-decoding message-passing algorithm for sparse parity-check matrix codes
No full textA turbo-decoding message-passing (TDMP) algorithm for sparse parity-check matrix (SPCM) codes such as low-density parity-check, repeat-accumulate, and turbo-like codes is presented. The main advantages of the proposed algorithm over the standard decoding algorithm are 1) its faster convergence speed by a factor of two in terms of decoding iterations, 2) improvement in coding gain by an order of magnitude at high signal-to-noise ratio (SNR), 3) reduced memory requirements, and 4) reduced decoder complexity. In addition, an efficient algorithm for message computation using simple max operations is also presented. Analysis using EXIT charts shows that the TDMP algorithm offers a better performance-complexity tradeoff when the number of decoding iterations is small, which is attractive for high-speed applications. A parallel version of the TDMP algorithm in conjunction with architecture-aware (AA) SPCM codes, which have embedded structure that enables efficient high-throughput decoder implementation, are presented. Design examples of AA-SPCM codes based on graphs with large girth demonstrate that AA-SPCM codes have very good error-correcting capability using the TDMP algorithm. © 2006 IEEE.BAHL LR, 1974, IEEE T INFORM THEORY, V20, P284, DOI 10.1109-TIT.1974.1055186; Bangerter B., 2003, INTEL TECHNOL J, V7; BENES VE, 1964, ATandT TECH J, V43, P1641; BERROU C, 1993, IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS 93 : TECHNICAL PROGRAM, CONFERENCE RECORD, VOLS 1-3, P1064, DOI 10.1109-ICC.1993.397441; Blanksby AJ, 2002, IEEE J SOLID-ST CIRC, V37, P404, DOI 10.1109-4.987093; Brink S. T., 2001, IEEE T COMMUN, V49, P1727; Divsalar D., 1998, Proceedings. Thiry-Sixth Annual Allerton Conference on Communication, Control, and Computing; FAN J, LDPC EFFICIENT ALTER; Gallager R., 1963, LOW DENSITY PARITY C; Gross WJ, 2001, IEEE T CIRCUITS-II, V48, P904, DOI 10.1109-82.974777; GUILLOUD F, 2004, THESIS ENST PARIS; Hocevar D. E., 2003, P IEEE INT C COMM, P2708; HU XY, 2001, P IEEE GLOB TEL C IE, pE1036; Jin H., 2001, THESIS CALTECH PASAD; Jin H., 2000, P 2 INT S TURB COD R, P1; Kschischang FR, 1998, IEEE J SEL AREA COMM, V16, P219, DOI 10.1109-49.661110; Lan CF, 2004, IEEE T COMMUN, V52, P1092, DOI 10.1109-TCOMM.2004.831406; Lin S., 2004, ERROR CONTROL CODING; LUBOTZKY A, 1988, COMBINATORICA, V8, P261, DOI 10.1007-BF02126799; Mansour M. M., 2002, P INT S LOW POW EL D, P284; MANSOUR MM, 2002, P IEEE GLOB TEL C 20, P1383; Mansor M, 2003, PASOH: ECOLOGY OF A LOWLAND RAIN FOREST IN SOUTHEAST ASIA, P215; MANSOUR MM, 2005, 39 ANN C INF SCI SYS; Mansour MM, 2003, IEEE T VLSI SYST, V11, P976, DOI 10.1109-TVLSI.2003.817545; MANSOUR MM, 2003, P IEEE INT S CIRC SY, V2, P57; MANSOUR MM, 2002, ANN C INF SCI SYST C; MARGULIS GA, 1982, COMBINATORICA, V2, P71, DOI 10.1007-BF02579283; MCLIECE RJ, 1998, IEEE J SEL AREA COMM, V16, P140; Pearl J., 1988, PROBABILISTIC REASON; RASHI Y, EFFICIENT ALTERNATIV; Richardson TJ, 2001, IEEE T INFORM THEORY, V47, P619, DOI 10.1109-18.910578; Rosenthal J., 2000, P 38 ALL C COMM CONT, P248; Roumy A, 2004, IEEE T INFORM THEORY, V50, P1711, DOI 10.1109-TIT.2004.831778; Royle G., CUBIC CAGES; SONG H, 2002, JPN J APPL PHYS, P1749; TANNER RM, 1981, IEEE T INFORM THEORY, V27, P533, DOI 10.1109-TIT.1981.1056404; Tanner R. M., 1999, P 37 ALL C COMM CONT; TANNER RM, 2001, P INT S COMM THEOR A, P1; Tanner RM, 2004, IEEE T INFORM THEORY, V50, P2966, DOI 10.1109-TIT.2004.838370; TUCHLER M, 2002, C INF SCI SYST PRINC; Vasic B, 2003, J LIGHTWAVE TECHNOL, V21, P438, DOI 10.1109-JLT.2003.808769; Yang M, 2004, IEEE T COMMUN, V52, P564, DOI 10.1109-TCOMM.2004.826367; YEO E, 2001, P IEEE GLOBECOM, P3019; Zhang JT, 2005, IEEE T COMMUN, V53, P209, DOI 10.1109-TCOMM.2004.84198252453
Kernel method and system of functional equations
No full textAbstractIntroduced by Knuth and subsequently developed by Banderier et al., Prodinger, and others, the kernel method is a powerful tool for solving power series equations in the form of F(z,t)=A(z,t)F(z0,t)+B(z,t) and several variations. Recently, Hou and Mansour [Q.-H. Hou, T. Mansour, Kernel Method and Linear Recurrence System, J. Comput. Appl. Math. (2007), (in press).] presented a systematic method to solve equation systems of two variables F(z,t)=A(z,t)F(z0,t)+B(z,t), where A is a matrix, and F and B are vectors of rational functions in z and t. In this paper we generalize this method to another type of rational function matrices, i.e., systems of functional equations. Since the types of equation systems we are interested in arise frequently in various enumeration questions via generating functions, our tool is quite useful in solving enumeration problems. To illustrate this, we provide several applications, namely the recurrence relations with two indices, and counting descents in signed permutations
Computational study of the deamination reaction of cytosine
No full textThe decomposition reaction of formamidine yielding hydrogen cyanide and ammonia has been studied first as a simple model for the intramolecular and intermolecular hydrogen rearrangement of cytosine. The gas phase decomposition of formamidine predicted a high activation energy of 259 kJ mol⁻¹ at the G3 level of theory. Adding one and two water molecules catalysed the reaction by forming a cyclic hydrogen bonded transition state, reducing the barrier to 169 and 151 kJ mol⁻¹ at the G3 level, respectively. The PCM solvent model predicts a significant lowering of the free energy of activation. -- The mechanism for the deamination reaction of cytosine with H₂O, OH-, and H₂O/OH- to produce uracil was investigated using ab initio (HF and MP2) levels and B3LYP DFT calculations. All pathways in the cytosine deamination produce an initial tetrahedral intermediate followed by several conformational changes. The final intermediate for all pathways dissociates to products via a 1 - 3 proton shift. Two pathways for the deamination reaction of cytosine with H₂O and OH- were found. The activation energy for the rate determining steps of deamination of cytosine with H₂O for pathways A and Bare 221 and 260 kJ mol⁻¹ at the G3MP2 level of theory, respectively. The deamination of cytosine with H₂O by either pathway is therefore unlikely because of the high barriers involved. Deamination with OH⁻ through pathway C resulted in the lowest activation energy, 203 kJ mol⁻¹ at the G3MP2 level of theory. -- The deamination with H₂O/OH- and 2H₂O/OH- in which the water molecules acted as a solvent and a catalyst was also investigated. Seven pathways for the deamination reaction for these systems were found. We found that the barrier for the water-mediated 1-3 proton shift is reduced by 46 kJ mol⁻¹ at the G3MP2 level of theory. We also found that the addition of the second water molecule reduces the barriers for both rate-determining steps by 31 kJ mol⁻¹. The activation energy for the rate-determining step, the formation of tetrahedral intermediate for pathway D is 115 kJ mol⁻¹ at the G3MP2 level of theory, in excellent agreement with the experimental value. This work shows, for the first time, a plausible mechanism for the deamination of cytosine and accounts for the observed experimental activation energy (117 ± 4 kJ mol⁻¹)Includes bibliographical references
Construction and hardware-efficient decoding of raptor codes
No full textRaptor codes are a class of concatenated codes composed of a fixed-rate precode and a Luby-transform (LT) code that can be used as rateless error-correcting codes over communication channels. These codes have the atypical features of dynamic code-rate, highly irregular Tanner graph check-degree distribution, random LT-code structure, and LT-precode concatenation, which render a hardware-efficient decoder implementation achieving good error-correcting performance a challenging task. In this paper, the design of hardware-efficient Raptor decoders with good performance is addressed through joint optimizations targeting 1) the code construction, 2) decoding schedule, and 3) decoder architecture. First, random encoding is decoupled by developing a two-stage LT-code construction scheme that embeds structural features in the LT-graph that are amenable to efficient implementation while guaranteeing good performance. An LT-aware LDPC precode construction methodology that ensures architectural-compatibility with the structured LT code is also proposed. Second, a decoding schedule is optimized to reduce memory cost and account for processing workload-variability caused by the varying code rate. Third, to address the problems of check-degree irregularity and hardware underutilization, a novel reconfigurable check unit that attains a constant throughput while processing a varying number of LT and LDPC nodes is presented. These design steps collectively are employed to generate serial and partially-parallel decoder architectures. A Raptor code instance constructed using the proposed method having LT data-block length of 1210 is shown to outperform or closely match the performance of conventional LDPC codes over the code-rate range [0.4,2\3. The corresponding hardware serial decoder is synthesized using 65-nm CMOS technology and achieves a throughput of 22 Mb-s at rate 0.4 for a BER of 10-6 , dissipates an average power of 222 mW at 1.2 V, and occupies an area of 1.77 mm2. © 2011 IEEE.[Anonymous], SYN DES COMP; [Anonymous], 2009, 802162009 IEEE; BAHL LR, 1974, IEEE T INFORM THEORY, V20, P284, DOI 10.1109-TIT.1974.1055186; Chen JH, 2002, IEEE COMMUN LETT, V6, P208, DOI 10.1109-4234.1001666; Chen JH, 2005, IEEE T COMMUN, V53, P1288, DOI 10.1109-TCOMM.2005.852852; DORE JB, 2007, P 18 ANN IEEE INT S, P1; Elias P., 1955, P 3 LOND S INF THEOR, P61; Etesami O, 2006, IEEE T INFORM THEORY, V52, P2033, DOI 10.1109-TIT.2006.872855; Forney Jr G., 1966, CONCATENATED CODES; Fossorier MPC, 1999, IEEE T COMMUN, V47, P673, DOI 10.1109-26.768759; Gallager R., 1963, LOW DENSITY PARITY C; GUNNAM K, 2007, P IEEE INT C COMM IC, P4542; Howland CJ, 2001, P 2001 IEEE INT S CI, P742; HU XY, 2001, P IEEE INT GLOB COMM; Jiang N, 2009, IEEE T BROADCAST, V55, P251, DOI 10.1109-TBC.2008.2012359; Kim S, 2011, IEEE T VLSI SYST, V19, P1099, DOI 10.1109-TVLSI.2010.2043965; Liu CH, 2008, IEEE J SOLID-ST CIRC, V43, P684, DOI 10.1109-JSSC.2007.916610; Luby M., 2002, Proceedings 43rd Annual IEEE Symposium on Foundations of Computer Science, DOI 10.1109-SFCS.2002.1181950; Mansour MA, 2006, IEEE T SIGNAL PROCES, V54, P4376, DOI 10.1109-TSP.2006.880240; Mansour MM, 2006, IEEE J SOLID-ST CIRC, V41, P684, DOI 10.1109-JSSC.2005.864133; Mansour MM, 2003, IEEE T VLSI SYST, V11, P976, DOI 10.1109-TVLSI.2003.817545; MURALIMANOHAR N, 2007, P 40 ANN IEEE ACM IN, P3, DOI DOI 10.1109-MICRO.2007.33; Palanki R., 2004, Proceedings. 2004 IEEE International Symposium on Information Theory (IEEE Cat. No.04CH37522); ROVINI M, 2007, P IFIP INT C VER LAR, P236; Shokrollahi A, 2006, IEEE T INFORM THEORY, V52, P2551, DOI 10.1109-TIT.2006.874390; TANNER RM, 1981, IEEE T INFORM THEORY, V27, P533, DOI 10.1109-TIT.1981.1056404; TOWNSEND RL, 1967, IEEE T INFORM THEORY, V13, P183, DOI 10.1109-TIT.1967.1053974; Xiang B, 2010, IEEE T VLSI SYST, V18, P1447, DOI 10.1109-TVLSI.2009.2025169; Zhang K, 2009, IEEE J SEL AREA COMM, V27, P985, DOI 10.1109-JSAC.2009.09081622
Insight into 8 patients with nonarteritic anterior ischemic optic neuropathy following anti-VEGF injections
No full text[No abstract available]Mansour AM, 2012, CLIN OPHTHALMOL, P343; Prescott CR, 2012, J NEURO-OPHTHALMOL, V13, P5130
Molecular dynamics simulation of N-octyl-N-quaternized chitosan derivatives as a drug carrier
No full text The dynamic amphiphilic behavior of N-octyl-N-quaternized chitosan derivatives in aqueous solution is investigated using molecular dynamics (MD) simulations. It is found that quaternization decreases the intra-chain hydrogen bond formation which leads to reduced rigidity of the chitosan backbone. The effect of octyl substitution is much less pronounced. Analysis of hydrogen bonding reveals the presence of a hydrogen bond within the quaternized glucosamine unit, which causes the distortion of the usual chair conformation. Also, H-bond formation with the solvent water molecules was found to stabilize the intra-chain HO3-O5 hydrogen bond. Additionally, an aqueous solution containing the 10%-N-octyl-50%-N-quaternized chitosan derivative (1O5QCS) and the anti-cancer drug 10-hydroxycamptothecin (10-HCPT) was also investigated using MD simulations. It was found that van der Waals and electrostatic forces have virtually equal contributions to the nonbonded interactions responsible for complexation. Furthermore, H-bond formation between drug and drug carrier contributes to lactone ring stability and subsequent bioavailability. </jats:p
Protective effects of thymoquinone and desferrioxamine against hepatotoxicity of carbon tetrachloride in mice
No full textThe effects of thymoquinone (TQ) and desferrioxamine (DFO) against carbon
tetrachloride (CCU)-induced hepatotoxicity were investigated. A single dose of CCU
(20 ul/kg, i.p.) induced hepatotoxicity, manifested biochemically by significant
elevation of activities of serum enzymes, such as alanine transaminase (ALT, EC:
2.6.1.2 ) , aspartate transaminase (AST, EC: 2.6.1.1 ) and lactate dehydrogenase
(LDH, EC: 1.1.1.27). Hepatotoxicity was further evidenced by significant decrease of
total sulfhydryl (-SH) content, and catalase (EC: 1.11.1.6) activity in hepatic tissues
and significant increase in hepatic lipid peroxidation measured as malondialdhyde
(MDA). Pretreatment of mice with DFO (200 mg/kg i.p.) 1 h before CCU injection or
administration of TQ (16 mg/kg/day, p.o.) in drinking water, starting 5 days before
CCU injection and continuing during the experimental period, ameliorated the
hepatotoxicity induced by CCI4, as evidenced by a significant reduction in the
elevated levels of serum enzymes as well as a significant decrease in the hepatic
MDA content and a significant increase in the total sulfhydryl content 24 h after CCU
administration. In a separate in vitro assay, TQ and DFO inhibited the non-enzymatic
lipid peroxidation of normal mice liver homogenate induced by Fe3 +/ascorbate in a
dose-dependent manner. These results indicate that TQ and DFO are efficient
cytoprotective agents against CCU-induced hepotoxicity, possibly through inhibition
of the production of oxygen free radicals that cause lipid peroxidation.Corresponding Author:
Dr. Mahmoud Mansour, Professor, Department of Pharmacology, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh-11451, Saudi Arabia. Email: [email protected]
Decomposition of ethylamine through bimolecular reactions
No full textEthylamine (EA) often serves as a surrogate species to represent aliphatic amines that occur in biofuels. This contribution reports, for the first time, the thermochemical and kinetic parameters for bimolecular reactions of EA with three prominent radicals that form in the initial stages of biomass decomposition; namely, H, CH3 and NH2. Abstraction of a methylene H atom from the EA molecule largely dominates H loss from the two other sites (i.e., methyl and amine hydrogens) for the three considered radicals. We demonstrate that, differences in bond dissociation enthalpies of methylene C–H bonds among EA, ethanol and propane reflect their corresponding HOMO/LUMO energy gaps. At low and intermediate temperatures, the rate of H abstraction from the methylene site in EA exceeds the corresponding values for propane and ethanol. As the temperature rises, matching entropic factors induce comparable rate constants for the three molecules
Hardware-oriented construction of a family of rate-compatible raptor codes
No full textA family of architecture-aware Raptor codes is constructed. The proposed construction scheme is targeted to design rate-compatible structured codes that span a wide range of rates and block sizes while still having hardware-efficient decoder implementations. The codes match the corresponding fixed-rate LDPC codes in error-correcting performance, decoding convergence speed, and message-memory requirements. Three novel steps are incorporated in the scheme: 1) a new group-based design of the code source matrix; 2) an architecture-aware row splitting-after-merging technique to construct irregular precodes; and 3) structured LT row-encoding. A code instance was designed accordingly and compared to standardized LDPC codes. The error-rate performance closely matches that of LDPC, whereas the convergence speed and message count gaps are narrowed down to values between [1.1×, 1.8×] and [1.1×, 1.3×], respectively. © 2014 IEEE.[Anonymous], 2012, 80216 IEEE; Chen T., 2011, P IEEE GLOBECOM, P1; Dolinar S., 2005, P IEEE INT S INF THE, P1627, DOI 10.1109-ISIT.2005.1523620; Etesami O, 2006, IEEE T INFORM THEORY, V52, P2033, DOI 10.1109-TIT.2006.872855; Ha J, 2004, IEEE T INFORM THEORY, V50, P2824, DOI 10.1109-TIT.2004.836667; Luby M, 2002, ANN IEEE SYMP FOUND, P271; Nguyen TV, 2012, IEEE T COMMUN, V60, P2841, DOI 10.1109-TCOMM.2012.081012.110010; Soljanin E., 2006, P IEEE INF THEOR WOR, P155; Venkiah A., 2008, P IEEE SARN S APR 20, P1; Venkiah A, 2007, 2007 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY PROCEEDINGS, VOLS 1-7, P421, DOI 10.1109-ISIT.2007.4557262; Zeineddine H, 2011, IEEE T SIGNAL PROCES, V59, P2943, DOI 10.1109-TSP.2011.21146550
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