Medium Access Control Game with An Enhanced

Abstract-We consider distributed medium access control in a wireless network where each link layer user (transmitter) is equipped with multiple transmission options as opposed to the classical binary options of transmitting/idling. In each time slot, a user randomly chooses a transmission option according to a "transmission probability vector". Packets sent by the users are either received or lost depending on whether reliable decoding is supported by the communication channel. We propose a game theoretic model for distributed medium access control where each user adapts its transmission probability vector to maximize a utility function. Condition under which the medium access control game has a unique Nash equilibrium is obtained. Simulation results show that, when multiple transmission options are provided, users in a distributed network tend to converge to channel sharing schemes that are consistent with the well-known information theoretic understandings

Relating the composition of continental margin surface sediments from the Ross Sea to the Amundsen Sea, West Antarctica, to modern environmental conditions

Investigating the multiple proxies involving productivity, organic geochemistry, and trace element (TE) enrichment in surface sediments could be used as paleoenvironment archives to gain insights into past and future environmental conditions changes. We present redox-sensitive TEs (Mn, Ni, Cu, U, P, Mo, Co, V, Zn, and Cd), productivity-related proxies (total organic carbon and opal), and total nitrogen and CaCO3 contents of bulk surface sediments of this area. The productivity proxies from the shelf and coastal regions of the Ross and the Amundsen seas showed that higher productivity was affiliated with an area of nutrient-rich deep water upwelling. The upwelling of weakly corrosive deep water may be beneficial for preserving CaCO3, while highly corrosive dense water, if it forms on the shelf near the coastal region (coastal polynya), could limit the preservation of CaCO3 in modern conditions. There were no oxic or anoxic conditions in the study area, as indicated by the enrichment factors of redox-sensitive TEs (Mn, Co, and U). The enrichment factor of Cd, which is redox-sensitive, indicated suboxic redox conditions in sediment environments because of high primary productivity and organic matter preservation/decomposition. The enrichment factors of other redox-sensitive TEs (P, Ni, Cu, V, and Zn) and the correlations between the element/Ti ratio with productivity and nutrient proxies indicated that the organic matter decomposed, and there was massive burial of phytoplankton biomass. There was variation in the enrichment, such that sediments were enriched in P, Mo, and Zn, but depleted in Ni, Cu, and V

RNAi-directed downregulation of OsBADH2 results in aroma (2-acetyl-1-pyrroline) production in rice (Oryza sativa L.)

<p>Abstract</p> <p>Background</p> <p>Aromatic rice is popular worldwide because of its characteristic fragrance. Genetic studies and physical fine mapping reveal that a candidate gene (<it>fgr</it>/<it>OsBADH2</it>) homologous to <it>betaine aldehyde dehydrogenase </it>is responsible for aroma metabolism in fragrant rice varieties, but the direct evidence demonstrating the functions of <it>OsBADH2 </it>is lacking. To elucidate the physiological roles of <it>OsBADH2</it>, sequencing approach and RNA interference (RNAi) technique were employed to analyze allelic variation and functions of <it>OsBADH2 </it>gene in aroma production. Semi-quantitative, real-time reverse transcription-polymerase chain reaction (RT-PCR), as well as gas chromatography-mass spectrometry (GC-MS) were conducted to determine the expression levels of <it>OsBADH2 </it>and the fragrant compound in wild type and transgenic <it>OsBADH2</it>-RNAi repression lines, respectively.</p> <p>Results</p> <p>The results showed that multiple mutations identical to <it>fgr </it>allele occur in the 13 fragrant rice accessions across China; <it>OsBADH2 </it>is expressed constitutively, with less expression abundance in mature roots; the disrupted <it>OsBADH2 </it>by RNA interference leads to significantly increased 2-acetyl-1-pyrroline production.</p> <p>Conclusion</p> <p>We have found that the altered expression levels of <it>OsBADH2 </it>gene influence aroma accumulation, and the prevalent aromatic allele probably has a single evolutionary origin.</p

Waterfowl as the main reservoir of avian influenza A (H5N6) virus in wet markets

published_or_final_versio

Western Pacific physical and biological controls on atmospheric CO2 concentration over the last 700 kyr

We present new geochemical evidence of changes in the vertical dissolved inorganic carbon (DIC) distribution in the western tropical Pacific over the last 700 kyr, derived from stable carbon isotope (ä13C) signals recorded in epifaunal benthic (Cibicidoides wuellerstorfi) and thermocline-dwelling planktonic (Pulleniatina obliquiloculata) foraminifera extracted from the Calypso Core MD06-3047. We further analyse the results of a transient numerical experiment of the Last Glacial Maximum (LGM) and the last deglaciation performed with the carbon isotope-enabled earth system model LOVECLIM, to understand the deglacial changes in DIC distribution and verify the proxy-based hypothesis. During glacial periods of the past 700 kyrs, the distinct negative deep water ä13CDIC values obtained from the benthic foraminifera suggest a carbon increase in the deep ocean, which could have been caused by weakening of deep Southern Ocean (SO) ventilation and enhanced marine biological productivity driven by dust-induced iron fertilization. During glacial terminations, a decrease of thermocline ä13CDIC associated with an increase in deep water ä13CDIC indicate a reduced vertical DIC gradient and the net transmission of 12C from the deep waters to the thermocline, caused mainly by the physical process (enhanced SO ventilation). On longer time scales, the largest increase in the Pacific deep carbon reservoir ä13CDIC during the marine isotope stage (MIS) 12/11 transition coincided with the mid-Brunhes climatic shift, which implies that the extent of oceanic carbon release during this interval was much larger than that during other deglaciations since 700 ka B.P. We infer that this could have been caused by reorganization of the oceanic carbon system. These findings provide new insights into the Pleistocene evolution of the carbon-cycle system in the Pacific Ocean

Expression and significance of SDF-1 and its receptor CXCR4 in the retina of pregnant rats after optic nerve injury

Stromal cell–derived factor 1 (SDF-1) and its receptor CXCR4 have shown to play a role in embryonic development process, regulation of hematopoiesis, mediating immunology response, inflammatory reaction, and metastasis of malignant tumor. Recently, SDF-1 and CXCR4 are also closely related to retinal neovascularization. This study was to investigate the expression of SDF-1 and CXCR4 in the retina after optic nerve injury in pregnant rats so as to reveal its significance. A total of 12 pregnant rats were randomly divided into normal group and experimental group (after 5 days of optic nerve injury), six rats in each group; expressions of SDF-1 as well as CXCR4 in rat retina were detected by immunofluorescence staining and western blot assay. The result of immunofluorescence staining showed that the relative gray scale values of SDF-1 and CXCR4 in the experimental group were significantly higher than those in the normal group ( P  < 0.05), and the result of Western blot assay showed that the expression levels of SDF-1 and CXCR4 in the experimental group were significantly higher than those in the normal group ( P  < 0.05). In conclusion, SDF-1 and its receptor CXCR4 have abnormal expression in the retina of pregnant rats after optic nerve injury, which may be involved in the occurrence and development of optic nerve injury