Computation of Posterior Marginals on Aggregated State Models for Soft Source Decoding

Optimum soft decoding of sources compressed with variable length codes and quasi-arithmetic codes, transmitted over noisy channels, can be performed on a bit/symbol trellis. However, the number of states of the trellis is a quadratic function of the sequence length leading to a decoding complexity which is not tractable for practical applications. The decoding complexity can be significantly reduced by using an aggregated state model, while still achieving close to optimum performance in terms of bit error rate and frame error rate. However, symbol a posteriori probabilities can not be directly derived on these models and the symbol error rate (SER) may not be minimized. This paper describes a two-step decoding algorithm that achieves close to optimal decoding performance in terms of SER on aggregated state models. A performance and complexity analysis of the proposed algorithm is given.     

Robust multiplexed codes for compression of heterogeneous data

Compression systems of real signals (images, video, audio) generate sources of information with different levels of priority which are then encoded with variable-length codes (VLCs). This paper addresses the issue of robust transmission of such VLC encoded heterogeneous sources over error-prone channels. VLCs are very sensitive to channel noise: when some bits are altered, synchronization losses can occur at the receiver. This paper describes a new family of codes, called multiplexed codes, that confine the de-synchronization phenomenon to low-priority data while reaching asymptotically the entropy bound for both (low- and high-priority) sources. The idea consists of creating fixed-length codes for high-priority information and of using the inherent redundancy to describe low-priority data, hence the name multiplexed codes. Theoretical and simulation results reveal a very high error resilience at almost no cost in compression efficiency.     

Cloning of the cDNA encoding the urotensin II precursor in frog and human reveals intense expression of the urotensin II gene in motoneurons of the spinal cord

Urotensin II (UII) is a cyclic peptide initially isolated from the caudal neurosecretory system of teleost fish. Subsequently, UII has been characterized from a frog brain extract, indicating that a gene encoding a UII precursor is also present in the genome of a tetrapod. Here, we report the characterization of the cDNAs encoding frog and human UII precursors and the localization of the corresponding mRNAs. In both frog and human, the UII sequence is located at the C-terminal position of the precursor. Human UII is composed of only 11 amino acid residues, while fish and frog UII possess 12 and 13 amino acid residues, respectively. The cyclic region of UII, which is responsible for the biological activity of the peptide, has been fully conserved from fish to human. Northern blot and dot blot analysis revealed that UII precursor mRNAs are found predominantly in the frog and human spinal cord. In situ hybridization studies showed that the UII precursor gene is actively expressed in motoneurons. The present study demonstrates that UII, which has long been regarded as a peptide exclusively produced by the urophysis of teleost fish, is actually present in the brain of amphibians and mammals. The fact that evolutionary pressure has acted to conserve fully the biologically active sequence of UII suggests that the peptide may exert important physiological functions in humans.     

Hepatic and extra-hepatic transcription of inter-alpha-inhibitor family genes under normal or acute inflammatory conditions in rat

A physician may be called upon to evaluate disability in the roles of impartial judge of impairment, expert witness in a legal case, or treating physician. Critical to these processes are discernment between disability and impairment, an understanding of legal responsibilities, and knowledge of the elements of examinations and reports.     

Study of the reactivity and <Emphasis Type="Italic">in vitro</Emphasis> bioactivity of Sr-substituted α-TCP cements

In this study the effect of strontium substitution on the hydrolysis of α -tricalcium phosphate (α -TCP) toward the formation of calcium deficient hydroxyapatite (CDHA) was investigated. For that purpose substituted α -TCP powders with 1, 5 and 10 mol% Sr substitution for Ca were synthesized by reacting at 1500 ^∘C stoichiometric amounts of CaCO₃, SrCO₃, and Ca₂P₂O₇, followed by rapid quenching in air. XRD analysis of the powders revealed the presence of α-TCP (traces of β-TCP) with enlarged unit cell volume at increased Sr contents, indicating the incorporation of Sr in the crystal structure. Strontium was also incorporated in the apatite phase as revealed by XRD analysis of the set cements. The hydrolysis of milled α-SrTCP powders and a pure α-TCP (control) was monitored by isothermal calorimetry and the compressive strength of set cements was tested. The results showed a decrease in the reactivity with increasing Sr content and similar final mechanical strength within the Sr series, though lower than the control. The in vitro bioactivity of the set cements after soaking in simulated body fluid for 4 weeks was also tested. The formation of a bone-like apatite layer on the surface of the set cements indicated a potential in vivo bioactivity.     

Ionic liquid ion sources for silicon reactive machining

In this article the authors report on ionic liquid ion sources (ILISs) for silicon reactive machining and direct microfabrication of silicon structures. The authors have developed a specific source geometry using the ionic liquid EMI-BF4 to obtain stable emission currents up to the 10 μA regime. ILIS EMI-BF4 engraving properties were then investigated in low and high current regime showing very different etching characteristics. The results and the chemical analysis of the patterned substrates suggest that reactive ion species can be generated from ILIS. This possibility is of major interest to allow decisive advances in the field of focused ion beam applications.     

Phase transformations and induced volume changes in a nitrided ternary Fe–3%Cr–0.345%C alloy

Phase transformations during nitriding of a ternary carbon iron-based alloy Fe–3%Cr–0.345%C were studied, aiming for a better understanding of residual stresses generation and evolution. The relationship between the precipitation of Cr₇C₃ carbides and CrN nitrides, the induced volume change and the mechanical properties were investigated at three distinct depths of the diffusion zone. The relaxation of residual stresses arose through phase transformations according to the diffusion of nitrogen but also of carbon.     

Entropy Coding With Variable-Length Rewriting Systems

This paper describes a family of codes for entropy coding of memoryless sources. These codes are defined by sets of production rules of the form almacr rarr bmacr, where a is a source symbol, and lmacr, bmacr are sequences of bits. The coding process can be modeled as a finite-state machine (FSM). A method to construct codes which preserve the lexicographic order in the binary-coded representation is described. For a given constraint on the number of states for the coding process, this method allows the construction of codes with a better compression efficiency than the Hu-Tucker codes. A second method is proposed to construct codes such that the marginal bit probability of the compressed bitstream converges to 0.5 as the sequence length increases. This property is achieved even if the probability distribution function is not known by the encoder