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

Neutrino Properties Studied with a Triton Source Using Large TPC Detectors

The purpose of the present paper is to study the neutrino properties as they may appear in the low energy neutrinos emitted in triton decay, with maximum neutrino energy of 18.6 KeV. The technical challenges to this end can be summarized as building a very large TPC capable of detecting low energy recoils, down to a few 100 eV, within the required low background constraints. More specifically We propose the development of a spherical gaseous TPC of about 10-m in radius and a 200 Mcurie triton source in the center of curvature. One can list a number of exciting studies, concerning fundamental physics issues, that could be made using a large volume TPC and low energy antineutrinos:1) The oscillation length involving the small mixing angle in the electronic neutrino disappearancei experiment is comparable to the length of the detector. Measuring the counting rate of neutrino-electron elastic scattering will give a precise measurement of the oscillation parameters free of systematic errors. First estimations show that a sensitivity of a few percent for the measurement of the above angle. 2) The low energy detection threshold offers a unique sensitivity for the neutrino magnetic moment which is about two orders of magnitude beyond the current experimental limit. 3) Scattering at such low neutrino energies has never been studied and any departure from the expected behavior may be an indication of new physics beyond the standard model. We present results of theoretical calculation and studies of possible measurements.Comment: 30 LaTex pages and 9 figure

Gamma decay of pygmy states in 90,94Zr from inelastic scattering of light ions

We performed experiments to study the low-energy part of the E1 response (Pygmy Dipole Resonance) in 90,94Zr nuclei, by measuring the (p,p'γ) and (α,α'γ) inelastic scattering reactions at energies Ebeam,p = 80 MeV and Ebeam,α = 130 MeV respectively. The inelastically scattered particles were measured by employing the high-resolution spectrometer Grand Raiden. The gamma-rays emitted following the de-excitation of the Zr target nuclei were detected using both the clover type HPGe detectors of the CAGRA array and the large volume LaBr3:Ce scintillation detectors from the HECTOR+ array. Some preliminary results are presented here

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

Search for in-band transitions in the candidate superdeformed band in Si 28

Background: Superdeformed (SD) bands are suggested by theory around Ca40 and in lighter alpha-conjugate nuclei such as Mg24, Si28, and S32. Such predictions originate from a number of theoretical models including mean-field models and antisymmetrized molecular dynamics (AMD) calculations. While SD bands have been identified in Ca40 and its near neighbors, evidence of their existence in the lighter, midshell nuclei is circumstantial at best. The key evidence of superdeformation would be the observation of transitions with high B(E2) transition strengths connecting states in a rotational sequence. This is challenging information to obtain since the bands lie at a high excitation energy and competition from out-of-band decay is dominant. Purpose: The purpose of the present study is to establish a new methodology to circumvent the difficulties in identifying and quantifying in-band transitions through directly populating candidate states in the SD band in Si28 through inelastic alpha scattering, selecting such states with a spectrometer, and measuring their gamma-ray decay with a large array of high-purity germanium detectors, allowing direct access to electromagnetic transition strengths. Methods: Excited states in Si28 were populated in the Si28(α,α′) reaction using a 130-MeV He4 beam from the K140 AVF cyclotron at the Research Center for Nuclear Physics. Outgoing alpha particles were analyzed using the Grand Raiden spectrometer positioned at an angle of 9.1° to favor the population of states with J≈4. Coincident gamma rays were detected with the CAGRA array of 12 HPGe clover detectors augmented by a set of four large LaBr3 detectors. Results: Data analysis showed that it was possible to identify additional low-energy transitions in competition with high-energy decays from excited states in Si28 in the vicinity of 10 MeV. However, while the candidate 4+ SD state at 10.944 MeV was populated, a 1148-keV transition to the candidate 2+ SD state at 9.796 MeV was not observed, and only an upper limit for its transition strength of B(E2)<43 W.u. could be established. This contradicts AMD predictions of ≈200 W.u. for such a transition. Conclusion: The present study strongly rejects the hypothesis that the candidate set of states identified in Si28 represents an SD band, which demonstrates the potential of the methodology devised here