Linear-Codes-Based Lossless Joint Source-Channel Coding for Multiple-Access Channels

A general lossless joint source-channel coding (JSCC) scheme based on linear codes and random interleavers for multiple-access channels (MACs) is presented and then analyzed in this paper. By the information-spectrum approach and the code-spectrum approach, it is shown that a linear code with a good joint spectrum can be used to establish limit-approaching lossless JSCC schemes for correlated general sources and general MACs, where the joint spectrum is a generalization of the input-output weight distribution. Some properties of linear codes with good joint spectra are investigated. A formula on the "distance" property of linear codes with good joint spectra is derived, based on which, it is further proved that, the rate of any systematic codes with good joint spectra cannot be larger than the reciprocal of the corresponding alphabet cardinality, and any sparse generator matrices cannot yield linear codes with good joint spectra. The problem of designing arbitrary rate coding schemes is also discussed. A novel idea called "generalized puncturing" is proposed, which makes it possible that one good low-rate linear code is enough for the design of coding schemes with multiple rates. Finally, various coding problems of MACs are reviewed in a unified framework established by the code-spectrum approach, under which, criteria and candidates of good linear codes in terms of spectrum requirements for such problems are clearly presented.Comment: 18 pages, 3 figure

Weight Distributions of Regular Low-Density Parity-Check Codes over Finite Fields

The average weight distribution of a regular low-density parity-check (LDPC) code ensemble over a finite field is thoroughly analyzed. In particular, a precise asymptotic approximation of the average weight distribution is derived for the small-weight case, and a series of fundamental qualitative properties of the asymptotic growth rate of the average weight distribution are proved. Based on this analysis, a general result, including all previous results as special cases, is established for the minimum distance of individual codes in a regular LDPC code ensemble.Comment: 15 pages, 5 figures, accepted for publication in IEEE Transactions on Information Theory, July 201

[N-(3-Meth­oxy-2-oxidobenzyl­idene-κO 2)alaninato-κ2 N,O]diphenyl­tin(IV)

The Sn atom of the title compound, [Sn(C6H5)2(C11H11NO4)], adopts a distorted SnNC2O2 trigonal–bipyramidal geometry with the O atoms in the axial positions. The metal atom forms five- and six-membered chelate rings with the O,N,O′-tridentate ligand

Dibut­yl[N-(5-chloro-2-oxidobenzyl­idene)-l-isoleucinato-κ3 O,N,O′]tin(IV)

The SnIV atom of the title compound, [Sn(C4H9)2(C13H14ClNO3)], adopts a distorted SnNC2O2 trigonal-bipyramidal geometry with a mean Sn—C distance of 2.105 Å and with Sn—O = 2.107 Å, and forms five- and six-membered chelate rings with the tridentate ligand. One butyl group is disordered over two positions with site occupancies of 0.65 (1):0.35 (1)

Prevalence of Kaposi’s sarcoma-associated herpesvirus in Uygur and Han populations from the Urumqi and Kashgar regions of Xinjiang, China

Kaposi’s sarcoma-associated herpesvirus (KSHV) is the infectious etiologic agent associated with Kaposi’s sarcoma (KS), primary effusion lymphoma, and multicentric Castleman disease. It has been shown that high KSHV prevalence and high incidence of both classic KS and AIDSassociated KS are found mostly among people of Uygur ethnicity in Xinjiang, while people of Han ethnicity in Xinjiang have a higher KSHV seroprevalence than those of other Han populations in mainland China. However, it is still unclear why there is such geographical and population variation in KSHV distribution in China. In this work, we focused on the populations in the Kashgar region and Urumqi area, where a total of 1294 research subjects were randomly selected to investigate the potential correlation between KSHV prevalence and different ethnicities in endemic areas of Xinjiang, and to determine risk factors that may affect KSHV infection rates or KS incidence. We identified a high seroprevalence of KSHV and high peripheral blood DNA infection in the general Uygur and Han populations in both Urumqi and Kashgar regions of Xinjiang, and determined that advancing age, low education level, and stationary population status affect KSHV infection rates. Further, KSHV-positive Uygur participants were shown to have higher prevalence of neutralizing antibodies and neutralizing antibody titers than KSHV-positive Han participants

trans-4-(1-Naphth­yl)-2-oxo-1,3-oxazolidine-5-carboxylic acid

The crystal structure of the title compound, C14H11NO4, is influenced by N—H⋯O and O—H⋯O hydrogen bonds, linking mol­ecules into one-dimensional tapes running along the [010] direction