スプライン関数とそのディジタル信号処理・画像処理への 応用に関する研究

本稿では, 2つの異なる関数基底を用いて信号を補間する手法として一般化区分的線形補間法を提案し, こうした関数系の信号処理・画像処理における有用性を検証した結果について報告する。 提案する関数系は, 線形近似と同様に近似オーダー(approximation order)が2であり, 階段関数や折れ線を正 確に再構成できる。関数基底は2つの実パラメータ τ と α によって特徴付けられる。パラメータ τ は関数基底の座標に対応するシフトパラメータであり, もう一方のパラメータaは関数の非対称性をあらわすパラメータである。これらのパラメータを変化させることで, 入力信号・画像に関係なく, 近似精度を向上させ最適化を図ることが可能となることを示す。 この補間手法では, 2つのパラメータを, τ=0.21, α=1 と設定することで, シフト線形補間 (shifted-linear interpolation) を再現することができる。ここでは, このパラメータの組み合わせ以外に, τ=0.21, α=0.58 と設定した場合に, シフト線形補間と同様の精度で信号の補間を行うことができることに注⽬する。シフト線形補間では分解プロセスにおいて IIR フィルタを必要としていたが, 後者のパラメータを設定した場合は FIR フィルタのみで構成可能である。これにより, 後者のパラメータはシフト線形補間におけるギブス (発振) 現象を大いに低減できる。 こうしたパラメータを設定した場合の有効性を, 補間操作を用いてディジタル画像を回転した場合のピーク SN 比 (原画像と回転した画像の信号・ノイズ比), 補間後の画像の最大振幅などを検証することを通して評価する

Observation of Spin-Dependent Charge Symmetry Breaking in ΛN\Lambda N Interaction: Gamma-Ray Spectroscopy of Λ4^4_{\Lambda }He

The energy spacing between the ground-state spin doublet of $^4_\Lambda$He(1$^+$,0$^+$) was determined to be $1406 \pm 2 \pm 2$ keV, by measuring $\gamma$ rays for the $1^+ \to 0^+$ transition with a high efficiency germanium detector array in coincidence with the $^4$He$(K^-,\pi^-)$ $^4_\Lambda$He reaction at J-PARC. In comparison to the corresponding energy spacing in the mirror hypernucleus $^4_\Lambda$H, the present result clearly indicates the existence of charge symmetry breaking (CSB) in $\Lambda N$ interaction. It is also found that the CSB effect is large in the $0^+$ ground state but is by one order of magnitude smaller in the $1^+$ excited state, demonstrating that the $\Lambda N$ CSB interaction has spin dependence

Plasmid pP62BP1 isolated from an Arctic Psychrobacter sp. strain carries two highly homologous type II restriction-modification systems and a putative organic sulfate metabolism operon

The complete nucleotide sequence of plasmid pP62BP1 (34,467 bp), isolated from Arctic Psychrobacter sp. DAB_AL62B, was determined and annotated. The conserved plasmid backbone is composed of several genetic modules, including a replication system (REP) with similarities to the REP region of the iteron-containing plasmid pPS10 of Pseudomonas syringae. The additional genetic load of pP62BP1 includes two highly related type II restriction-modification systems and a set of genes (slfRCHSL) encoding enzymes engaged in the metabolism of organic sulfates, plus a putative transcriptional regulator (SlfR) of the AraC family. The pP62BP1 slflocus has a compact and unique structure. It is predicted that the enzymes SlfC, SlfH, SlfS and SlfL carry out a chain of reactions leading to the transformation of alkyl sulfates into acyl-CoA, with dodecyl sulfate (SDS) as a possible starting substrate. Comparative analysis of the nucleotide sequences of pP62BP1 and other Psychrobacter spp. plasmids revealed their structural diversity. However, the presence of a few highly conserved DNA segments in pP62BP1, plasmid 1 of P. cryohalolentis K5 and pRWF-101 of Psychrobacter sp. PRwf-1 is indicative of recombinational shuffling of genetic information, and is evidence of lateral gene transfer in the Arctic environment

Conflicts Targeting Epigenetic Systems and Their Resolution by Cell Death: Novel Concepts for Methyl-Specific and Other Restriction Systems

Epigenetic modification of genomic DNA by methylation is important for defining the epigenome and the transcriptome in eukaryotes as well as in prokaryotes. In prokaryotes, the DNA methyltransferase genes often vary, are mobile, and are paired with the gene for a restriction enzyme. Decrease in a certain epigenetic methylation may lead to chromosome cleavage by the partner restriction enzyme, leading to eventual cell death. Thus, the pairing of a DNA methyltransferase and a restriction enzyme forces an epigenetic state to be maintained within the genome. Although restriction enzymes were originally discovered for their ability to attack invading DNAs, it may be understood because such DNAs show deviation from this epigenetic status. DNAs with epigenetic methylation, by a methyltransferase linked or unlinked with a restriction enzyme, can also be the target of DNases, such as McrBC of Escherichia coli, which was discovered because of its methyl-specific restriction. McrBC responds to specific genome methylation systems by killing the host bacterial cell through chromosome cleavage. Evolutionary and genomic analysis of McrBC homologues revealed their mobility and wide distribution in prokaryotes similar to restriction–modification systems. These findings support the hypothesis that this family of methyl-specific DNases evolved as mobile elements competing with specific genome methylation systems through host killing. These restriction systems clearly demonstrate the presence of conflicts between epigenetic systems

Enteric YaiW is a surface-exposed outer membrane lipoprotein that affects sensitivity to an antimicrobial peptide

yaiW is a previously uncharacterized gene found in enteric bacteria that is of particular interest because it is located adjacent to the sbmA gene, whose bacA ortholog is required for Sinorhizobium meliloti symbiosis and Brucella abortus pathogenesis. We show that yaiW is cotranscribed with sbmA in Escherichia coli and Salmonella enterica serovar Typhi and Typhimurium strains. We present evidence that the YaiW is a palmitate-modified surface exposed outer membrane lipoprotein. Since BacA function affects the very-long-chain fatty acid (VLCFA) modification of S. meliloti and B. abortus lipid A, we tested whether SbmA function might affect either the fatty acid modification of the YaiW lipoprotein or the fatty acid modification of enteric lipid A but found that it did not. Interestingly, we did observe that E. coli SbmA suppresses deficiencies in the VLCFA modification of the lipopolysaccharide of an S. meliloti bacA mutant despite the absence of VLCFA in E. coli. Finally, we found that both YaiW and SbmA positively affect the uptake of proline-rich Bac7 peptides, suggesting a possible connection between their cellular functions