Time Reversal UWB Communication: Experimental Study for High Data Rates in Dense Multipath Propagation Channels

International audienceHigh data rate communication for a Time Reversal UWB communication system is experimentally studied using binary pulse amplitude modulation in dense multipath propagation channels. Experiments are done for inter symbol intervals ranging from 64ns to 1ns. Signal, Interference and Noise components are separated from the received signal and their bit error rates are computed. The received signals are neither processed nor equalized. It is shown that at very high data rates (>125 Mbps), the performance of the system is limited by inter symbol interference. However at high data rates (<125 Mbps), time reversal system gives good BER performance in the presence of inter symbol interferenc

A Functional Genomics Approach to Establish the Complement of Carbohydrate Transporters in Streptococcus pneumoniae

The aerotolerant anaerobe Streptococcus pneumoniae is part of the normal nasopharyngeal microbiota of humans and one of the most important invasive pathogens. A genomic survey allowed establishing the occurrence of twenty-one phosphotransferase systems, seven carbohydrate uptake ABC transporters, one sodium∶solute symporter and a permease, underlining an exceptionally high capacity for uptake of carbohydrate substrates. Despite high genomic variability, combined phenotypic and genomic analysis of twenty sequenced strains did assign the substrate specificity only to two uptake systems. Systematic analysis of mutants for most carbohydrate transporters enabled us to assign a phenotype and substrate specificity to twenty-three transport systems. For five putative transporters for galactose, pentoses, ribonucleosides and sulphated glycans activity was inferred, but not experimentally confirmed and only one transport system remains with an unknown substrate and lack of any functional annotation. Using a metabolic approach, 80% of the thirty-two fermentable carbon substrates were assigned to the corresponding transporter. The complexity and robustness of sugar uptake is underlined by the finding that many transporters have multiple substrates, and many sugars are transported by more than one system. The present work permits to draw a functional map of the complete arsenal of carbohydrate utilisation proteins of pneumococci, allows re-annotation of genomic data and might serve as a reference for related species. These data provide tools for specific investigation of the roles of the different carbon substrates on pneumococcal physiology in the host during carriage and invasive infection

Establishment and Characterization of an Anoxia-tolerant Cell Line, PSU-AL-WS4ONE, Derived from an Embryo of the Annual Killifish Austrofundulus Limnaeus

Most animal cells rely on aerobic metabolism for survival and are damaged or die within minutes without oxygen. Embryos of the annual killifish Austrofundulus limnaeus, however, survive months without oxygen. Determining how their cells survive without oxygen has the potential to revolutionize our understanding of the cellular mechanisms supporting vertebrate anoxia tolerance and the evolution of such tolerance. Therefore, we aimed to establish and characterize an anoxia-tolerant cell line from A. limnaeus for investigating mechanisms of vertebrate anoxia tolerance. The PSU-AL-WS40NE cell line of neuroepithelial identity was established from embryonic tissue of A. limnaeus using a tissue explant. The cells can survive for at least 49 d without oxygen or replenishment of growth medium, compared to only 3 d of anoxic survival for two mammalian cell lines. PSU-AL-WS40NE cells accumulate lactate during anoxia, indicating use of common metabolic pathways for anaerobic metabolism. Additionally, they express many of the same small noncoding RNAs that are stress-responsive in whole embryos of A. limnaeus and mammalian cells, as well as anoxia-responsive small noncoding RNAs derived from the mitochondrial genome (mitosRNAs). The establishment of the cell line provides a unique tool for investigating cellular mechanisms of vertebrate anoxia tolerance, and has the potential to transform our understanding of the role of oxidative metabolism in cell biology

Then and now: Use of 16S rDNA gene sequencing for bacterial identification and discovery of novel bacteria in clinical microbiology laboratories

In the last decade, as a result of the widespread use of PCR and DNA sequencing, 16S rDNA sequencing has played a pivotal role in the accurate identification of bacterial isolates and the discovery of novel bacteria in clinical microbiology laboratories. For bacterial identification, 16S rDNA sequencing is particularly important in the case of bacteria with unusual phenotypic profiles, rare bacteria, slow-growing bacteria, uncultivable bacteria and culture-negative infections. Not only has it provided insights into aetiologies of infectious disease, but it also helps clinicians in choosing antibiotics and in determining the duration of treatment and infection control procedures. With the use of 16S rDNA sequencing, 215 novel bacterial species, 29 of which belong to novel genera, have been discovered from human specimens in the past 7.years of the 21st century (2001-2007). One hundred of the 215 novel species, 15 belonging to novel genera, have been found in four or more subjects. The largest number of novel species discovered were of the genera Mycobacterium (n = 12) and Nocardia (n = 6). The oral cavity/dental-related specimens (n = 19) and the gastrointestinal tract (n = 26) were the most important sites for discovery and/or reservoirs of novel species. Among the 100 novel species, Streptococcus sinensis, Laribacter hongkongensis, Clostridium hathewayi and Borrelia spielmanii have been most thoroughly characterized, with the reservoirs and routes of transmission documented, and S. sinensis, L. hongkongensis and C. hathewayi have been found globally. One of the greatest hurdles in putting 16S rDNA sequencing into routine use in clinical microbiology laboratories is automation of the technology. The only step that can be automated at the moment is input of the 16S rDNA sequence of the bacterial isolate for identification into one of the software packages that will generate the result of the identity of the isolate on the basis of its sequence database. However, studies on the accuracy of the software packages have given highly varied results, and interpretation of results remains difficult for most technicians, and even for clinical microbiologists. To fully utilize 16S rDNA sequencing in clinical microbiology, better guidelines are needed for interpretation of the identification results, and additional/supplementary methods are necessary for bacterial species that cannot be identified confidently by 16S rDNA sequencing alone. © 2008 The Authors Journal compilation © 2008 European Society of Clinical Microbiology and Infectious Diseases.link_to_subscribed_fulltex