On the effects of the packet size distribution on the packet loss process

Real-time multimedia applications have to use forward error correction (FEC) anderror concealment techniques to cope with losses in today’s best-effort Internet. The efficiency of these solutions is known however to depend on the correlation between losses in the media stream. In this paper we investigate how the packet size distribution affects the packet loss process, that is, the distribution of the number of lost packets in a block, the related FEC performance and the average loss run length. We present mathematical models for the loss process of the MMPP+M/D/1/K and the MMPP+M/M/1/K queues; we validate the models via simulations, and compare the results to simulation results with an MPEG-4 coded video trace. We conclude that the deterministic packet size distribution (PSD) not only results in lower stationary loss probability than the exponential one, but also gives a less correlated loss process, both at a particular average link load and at a particular stationary loss probability as seen by the media stream.Our results show that for applications that can only measure the packet loss probability, the effects of the PSD on FEC performance are higher in access networks, where a single multimedia stream might affect the multiplexing behavior. Our results show that the effects of the PSD on FEC performance are higher in access networks, where a single multimedia stream might affect the multiplexing behavior and thus can improve the queuing performance by decreasing the variance of its PSD.     

Laboratory studies in cross-species lung transplantation

The lack of sufficient suitable human donor lungs for the many patients requiring pulmonary transplantation as life-saving therapy for end-stage lung diseases has generated extensive interest in cross-species lung transplantation. Ethical concerns and those of animal rights advocates have prompted studies of nonprimate species as potential solid organ donors for humans. This paper provides an overview of some of the laboratory studies of cross-species pulmonary transplantation performed over the past 20 years and focuses, in particular, on more recent work (from our laboratory and others) in the area of porcine-to-primate pulmonary xenotransplantation.     

Multiplexed biochemical assays with biological chips

High density peptide and oligonucleotide chips are fabricated using semiconductor-based technologies. These chips have a variety of biological applications.     

Hydrogenases, accessory genes and the regulation of [NiFe] hydrogenase biosynthesis in Thiocapsa roseopersicina

The purple (Sulphur) phototrophic bacterium, Thiocapsa roseopersicina BBS contains several [NiFe] hydrogenases, of which two are membrane bound. Mutant T. roseopersicina cells, carrying deletions in both gene clusters showed hydrogenase activity. This activity was located in the cytoplasm. The structural gene cluster hoxEFUYH was identified and sequenced. In addition, genes homologous to hupUV/hoxBC, the hydrogen sensing hydrogenase have been identified and sequenced.Regulation of hydrogenase biosynthesis was studied in detail for HydSL (renamed HynSL). A random mutagenesis system was optimised for T. roseopersicina. One of the mutations was in a gene similar to that coding for the HypF proteins in other organisms. Inactivation of the hypF gene resulted in a 60-fold increase in hydrogen evolution under nitrogen fixing conditions. In addition to hypF, the following accessory genes were identified: hydD, hupK, hypC1, hypC2, hypDE. Characterisation of the corresponding gene products and search for additional accessory genes are in progress.     

Tetracaine reports a conformational change in the pore of cyclic nucleotide-gated channels

Local anesthetics are a diverse group of clinically useful compounds that act as pore blockers of both voltage- and cyclic nucleotide-gated (CNG) ion channels. We used the local anesthetic tetracaine to probe the nature of the conformational change that occurs in the pore of CNG channels during the opening allosteric transition. When applied to the intracellular side of wild-type rod CNG channels expressed in Xenopus oocytes from the alpha subunit, the local anesthetic tetracaine exhibits state-dependent block, binding with much higher affinity to closed states than to open states. Here we show that neutralization of a glutamic acid in the conserved P region (E363G) eliminated this state dependence of tetracaine block. Tetracaine blocked E363G channels with the same effectiveness at high concentrations of cGMP, when the channel spent more time open, and at low concentrations of cGMP, when the channel spent more time closed. In addition, Ni2+, which promotes the opening allosteric transition, decreased the effectiveness of tetracaine block of wild-type but not E363G channels. Similar results were obtained in a chimeric CNG channel that exhibits a more favorable opening allosteric transition. These results suggest that E363 is accessible to internal tetracaine in the closed but not the open configuration of the pore and that the conformational change that accompanies channel opening includes a change in the conformation or accessibility of E363.     

A GPC method to determine the composition of two component copolymers

Summary The hydrolytic degradation of Kevlar 49 fibers when dissolved in H₂SO₄ is characterized from (i) Fourier transform infrared (FTIR), CNH analyses and optical microscopy studies of insoluble crystals formed in the PPTA-H₂SO₄ dope and (ii) the rates of H₂SO₄-catalyzed hydrolysis of model compound aromatic amides. After hydrolysis of a PPTA amide linkage, the amide linkage adjacent to the freshly formed-COOH macromolecular end group rapidly hydrolyses resulting in the formation of terephthalic acid which then forms insoluble crystals in the PPTA-H₂SO₄ dope.Dedicated to Professor Dragutin Fle on the occasion of his 70th birthdaySupported in part by U.S. Department of Energy, LL National Laboratory under Contract W-7405-Eng-48     

On Weakly Smooth Uninorms on Finite Chain

In this paper, we characterize all weakly smooth uninorms (i.e., uninorms with smooth underlying operators) defined on a finite chain. It is proved that any such uninorm is determined by three unary functions and vice versa. As a by‐product, we obtain the characterizations of smooth t‐norms, smooth t‐conorms through additive generators and show that on a finite chain, there exists no counterpart of the class of uninorms continuous in ]0, 1[².     

Analysis of Gasolines by FT-IR Spectroscopy

An experimental and computational protocol was established for the simultaneous determination of several key gasoline properties from a single Fourier transform infrared (FT-IR) spectrum. The study has shown that midband FT-IR spectroscopy combined with multivariate calibration analysis is a versatile, efficient, and accurate technique for the simultaneous estimation of key gasoline properties within about 1 min with less than 2 mL of sample. The FT-IR-derived values of gasoline properties include research and motor octane numbers, aromatic, olefinic, and saturated hydrocarbon content, benzene content, and concentrations of ethanol, methyl tert-butyl ether, and total oxygen. Concentrations of other oxygenated compounds are expected to be equally predictable. However, since these oxygen-containing species have not been adequately represented among the currently commercially available gasoline samples, their calibration may only be achieved using laboratory fuel blends. Midrange boiling point data may also be estimated. Fuel properties determined by minor concentrations of fuel components, e.g., flash point, sulfur content, etc., may not be modeled because the corresponding FT-IR signals are below detection limits of presented experimental protocol. The precision of this procedure was shown to be comparable to reproducibility of the standard laboratory analyses used for direct measurement of specific fuel properties, with squared correlation coefficient (R(2)) ranging from 0.94 to 0.99 between the two sets of measurements. This new methodology could increase the corresponding output of the petroleum laboratories by a factor of over 200 to 1 while maintaining data integrity and minimizing sample requirements, environmental hazards, and cost.