Opportunistic Scheduling and Beamforming for MIMO-OFDMA Downlink Systems with Reduced Feedback

Opportunistic scheduling and beamforming schemes with reduced feedback are proposed for MIMO-OFDMA downlink systems. Unlike the conventional beamforming schemes in which beamforming is implemented solely by the base station (BS) in a per-subcarrier fashion, the proposed schemes take advantages of a novel channel decomposition technique to perform beamforming jointly by the BS and the mobile terminal (MT). The resulting beamforming schemes allow the BS to employ only {\em one} beamforming matrix (BFM) to form beams for {\em all} subcarriers while each MT completes the beamforming task for each subcarrier locally. Consequently, for a MIMO-OFDMA system with $Q$ subcarriers, the proposed opportunistic scheduling and beamforming schemes require only one BFM index and $Q$ supportable throughputs to be returned from each MT to the BS, in contrast to $Q$ BFM indices and $Q$ supportable throughputs required by the conventional schemes. The advantage of the proposed schemes becomes more evident when a further feedback reduction is achieved by grouping adjacent subcarriers into exclusive clusters and returning only cluster information from each MT. Theoretical analysis and computer simulation confirm the effectiveness of the proposed reduced-feedback schemes.Comment: Proceedings of the 2008 IEEE International Conference on Communications, Beijing, May 19-23, 200

Organization of Ty retrotransposons in the Saccharomyces cerevisiae genome

We have completed a genome-wide survey of all retrotransposon insertions in S. cerevisiae. We identified 333 total insertions, including 218 Tyl, 34 Ty2, 41 Ty3, 31 Ty4 and 7 Ty5 elements. 85% of these were solo LTRs or LTR fragments. Overall, retrotransposon sequences account for 2.9% of the genome. Phylogenetic analysis of LTR sequences from Tyl and Ty2 elements was able to distinguish between these closely related families; we identified a single-base pair insertion/deletion shared among all Ty2 LTRs. Relationships among Tyl and Ty2 LTRs further revealed ancient and relatively new lineages of these families. In contrast, Ty3 and Ty4 LTRs are all highly similar and share greater than 86% and 96% nucleotide identity, respectively. TyS is an extinct family with high sequence divergence, and no full-length elements were found. Ty1-Ty4 elements are predominantly found near genes transcribed by RNA polymerase Ill; this includes 89% of Tyl, 94% of Ty2, 98% of Ty3 and 94% of Ty4 insertions. TyS in contrast is found near telomeres or the HMR mating locus on chromosome III. tRNA genes, therefore, appear to be the primary determinant in the genome organization of yeast retrotransposons, and there are on average 1.2 insertions per tRNA gene. Local sequences also appear to bias integration sites. Analysis of target site duplications indicates all element families prefer the consensus 5' N, A/T, A/T, A/T, N 3'. Evidence for recombination is found near many Ty insertion sites, particularly those that are not associated with pol ill targets. 5' and 3' sequences flanking these elements are duplicated or rearranged among multiple chromosomes. S. cerevisiae offers the first opportunity to view the organization of retrotransposons at the genome level and will likely serve as a reference for comparison with other, more complex organisms

RNAase III-Type Enzyme Dicer Regulates Mitochondrial Fatty Acid Oxidative Metabolism in Cardiac Mesenchymal Stem Cells

Cardiac mesenchymal stem cells (C-MSC) play a key role in maintaining normal cardiac function under physiological and pathological conditions. Glycolysis and mitochondrial oxidative phosphorylation predominately account for energy production in C-MSC. Dicer, a ribonuclease III endoribonuclease, plays a critical role in the control of microRNA maturation in C-MSC, but its role in regulating C-MSC energy metabolism is largely unknown. In this study, we found that Dicer knockout led to concurrent increase in both cell proliferation and apoptosis in C-MSC compared to Dicer floxed C-MSC. We analyzed mitochondrial oxidative phosphorylation by quantifying cellular oxygen consumption rate (OCR), and glycolysis by quantifying the extracellular acidification rate (ECAR), in C-MSC with/without Dicer gene deletion. Dicer gene deletion significantly reduced mitochondrial oxidative phosphorylation while increasing glycolysis in C-MSC. Additionally, Dicer gene deletion selectively reduced the expression of β-oxidation genes without affecting the expression of genes involved in the tricarboxylic acid (TCA) cycle or electron transport chain (ETC). Finally, Dicer gene deletion reduced the copy number of mitochondrially encoded 1,4-Dihydronicotinamide adenine dinucleotide (NADH): ubiquinone oxidoreductase core subunit 6 (MT-ND6), a mitochondrial-encoded gene, in C-MSC. In conclusion, Dicer gene deletion induced a metabolic shift from oxidative metabolism to aerobic glycolysis in C-MSC, suggesting that Dicer functions as a metabolic switch in C-MSC, which in turn may regulate proliferation and environmental adaptation

Fermentation characteristics of Korean pear (Pyrus pyrifolia Nakai) puree by the Leuconostoc mesenteroides 51-3 strain isolated from Kimchi

A lactic acid bacterial strain showing fast growth and high acid production when cultured in Korean pear puree was isolated from Kimchi. This strain was analyzed by using the API 50 CHL kit and 16S rRNA sequencing and was thus identified as Leuconostoc mesenteroides 51-3. Korean pear puree was fermented with the L. mesenteroides 51-3 strain at 30°C for 12 h. The changes in pH, titratable acidity and viable cell count during fermentation were investigated. The pH and titratable acidity of the pear puree were 4.06 and 0.66%, respectively, after 12 h of fermentation. The viable cell count of L. mesenteroides 51-3 rapidly increased to 3.7 × 109 CFU/g after 12 h of cultivation. The content of lactic acid and acetic acid was determined to be 0.138 and 0.162%, respectively, after 12 h of fermentation. When the fermented pear puree was stored at 4°C, the pH, titratable acidity and viable cell count remained fairly constant for 14 days.Keywords: Fermentation, Korean pear puree, Leuconostoc mesenteroides.African Journal of Biotechnology Vol. 9(35), pp. 5735-5738, 30 August, 201

Temperature-dependent evolutions of excitonic superfluid plasma frequency in a srong excitonic insulator candidate, Ta2_2NiSe5_5

We investigate an interesting anisotropic van der Waals material, Ta$_{2}$NiSe$_{5}$, using optical spectroscopy. Ta$_{2}$NiSe$_{5}$ has been known as one of the few excitonic insulators proposed over 50 years ago. Ta$_{2}$NiSe$_{5}$ has quasi-one dimensional chains along the $a$-axis. We have obtained anisotropic optical properties of a single crystal Ta$_{2}$NiSe$_{5}$ along the $a$- and $c$-axes. The measured $a$- and $c$-axis optical conductivities exhibit large anisotropic electronic and phononic properties. With regard to the $a$-axis optical conductivity, a sharp peak near 3050 cm$^{-1}$ at 9 K, with a well-defined optical gap ($\Delta^{EI} \simeq$ 1800 cm$^{-1}$) and a strong temperature-dependence, is observed. With an increase in temperature, this peak broadens and the optical energy gap closes around $\sim$325 K($T_c^{EI}$). The spectral weight redistribution with respect to the frequency and temperature indicates that the normalized optical energy gap ($\Delta^{EI}(T)/\Delta^{EI}(0)$) is $1-(T/T_c^{EI})^2$. The temperature-dependent superfluid plasma frequency of the excitonic condensation in Ta$_{2}$NiSe$_{5}$ has been determined from measured optical data. Our findings may be useful for future research on excitonic insulators.Comment: 17 pages, 5 figure