Momentum dependence of spin polarization for beta emitting nuclei produced through charge exchange reaction at intermediate energy

Hyperfine interactions were studied in the intermetallic compound GdRh₂Si₂ by perturbed angular correlation (PAC) technique using ¹⁸¹Hf(¹⁸¹Ta) probe nuclei. The measurements were performed in the temperature range 15–285 K. The PAC spectra above the antiferromagnetic ordering temperature of the GdRh₂Si₂ compound (T _N ～ 106 K), were analyzed using a model that included only electric quadrupole interactions. The observed major fraction was assigned to the ¹⁸¹Hf(¹⁸¹Ta) probe substituting the Gd atoms. The PAC spectra below Néel temperature were analyzed using combined electric quadrupole and magnetic dipole interactions. The B_hf value at Gd, measured at 15 K was found to be 1.4(1) T which, is smaller, when compared with the values obtained in this compound using other nuclear probes, ¹⁵⁵Gd (B_hf ～ 30 T) and ¹⁴⁰Ce (B_hf ～ 26 T). The present result using ¹⁸¹Hf(¹⁸¹Ta) probe is quite interesting since it shows that the contribution to B_hf at Gd due the host is smaller than other components which contribute to the hyperfine field. The temperature dependence of B_hf shows an anomalous behavior.     

Direct Monitoring of Initiation Factor Dynamics through Formation of 30S and 70S Translation–Initiation Complexes on a Quartz Crystal Microbalance

Translation initiation is a dynamic and complicated process requiring the building a 70S initiation complex (70S‐IC) composed of a ribosome, mRNA, and an initiator tRNA. During the formation of the 70S‐IC, initiation factors (IFs: IF1, IF2, and IF3) interact with a ribosome to form a 30S initiation complex (30S‐IC) and a 70S‐IC. Although some spectroscopic analyses have been performed, the mechanism of binding and dissociation of IFs remains unclear. Here, we employed a 27 MHz quartz crystal microbalance (QCM) to evaluate the process of bacterial IC formation in translation initiation by following frequency changes (mass changes). IFs (IF1, IF2, and IF3), N‐terminally fused to biotin carboxyl carrier protein (bio‐BCCP), were immobilized on a Neutravidin‐covered QCM plate. By using bio‐BCCP‐IF2 immobilized to the QCM, three steps of the formation of ribosomal initiation complex could be sequentially observed as simple mass changes in real time: binding of a 30S complex to the immobilized IF2, a recruitment of 50S to the 30S‐IC, and formation of the 70S‐IC. The kinetic parameters implied that the release of IF2 from the 70S‐IC could be the rate‐limiting step in translation initiation. The IF3‐immobilized QCM revealed that the affinity of IF3 for the 30S complex decreased upon the addition of mRNA and fMet‐tRNA^fMet but did not lead to complete dissociation from the 30S‐IC. These results suggest that IF3 binds and stays bound to ICs, and its interaction mode is altered during the formation of 30S‐IC and 70S‐IC and is finally induced to dissociate from ICs by 50S binding. This methodology demonstrated here is applicable to investigate the role of IFs in translation initiation driven by other pathways.     

Feruloyl,caffeoyl, and flavonol glucosides from <Emphasis Type="Italic">Equisetum hyemale</Emphasis>

Feruloyl, caffeoyl, and flavonol glucosides were isolated from the stems of Equisetum hyemale L. The structures of the compounds were elucidated as trans-feruloyl-4-β-glucoside (1), cis-feruloyl-4-β-glucoside (2), trans-caffeoyl-3-β-glucoside (3), kaempferol-3-sophoroside (4), kaempferol-3-sophoroside-7-β-glucoside (5), and herbacetin-3-sophoroside-8-β-glucoside (6) based on the spectral evidence.     

Emission characteristics of the dielectronic recombination line of atomic Cu and selectively excited ionic Cu line by resonance charge-transfer collision in a low-pressure laser-induced plasma.

Emisson spectra and time-resolved two-dimensional (2D) emission images of the electron-ion dielectronic recombination (i.e. a reversal process of auto-ionization) line of neutral Cu atoms, the selectively excited Cu ionic line, and normal Cu atomic line were observed for understanding the excitation mechanisms of Cu neutral and ionic lines in a low-pressure laser-induced plasma (LP-LIP) of Ar. From the observations, the number of charged particles around the emitting species seems to increase with increasing Ar pressure. Different time-resolved 2D emission images were observed among the selectively excited Cu ionic line and other Cu emission lines resulting from the different excitation mechanisms of the respective emission lines. Collisions of the second kind and electron-ion recombinations were found to be one of the major excitation mechanisms of Cu in Ar LP-LIP.     

Emission intensity modulation of radio-frequency helium glow-discharge emission source by laser ablation.

A novel emission excitation source comprising a high repetition rate diode-pumped Q-switched Nd:YAG laser and a Grimm-style glow-discharge lamp is described. Laser-ablated atoms are introduced into the He glow discharge plasma, which then give emission signals. By using phase-sensitive detection with a lock-in amplifier, the emission signal modulated by the pulsed laser can be detected selectively. It is possible to estimate only the emission intensity of sample atoms ablated by laser irradiation with little interference from the other species in the plasma.     

85MeV19 F重离子辐照α-Al2O3的空洞研究

5.28×1016cm-2 85MeV 19 F辐照的α-Al2O3中,在其热退火过程中采用正电子湮没方法首次观察到了空洞. 450℃退火开始产生空洞,550℃到750℃空洞半径约为0.29nm不随温度变化,但浓度随温度增加而增加;高于750℃,空洞半径随温度升高迅速增大,1050℃时空洞的半径达1.10nm.     

β–NMR和β–NQR谱仪的建立

介绍了在中国原子能科学研究院建成的我国第一台βNMR及βNQR谱仪.进行了¹²B的寿命、磁矩和极化度的测量,实验结果表明谱仪工作可靠     

Comparison of the background corrected valence band XPS spectra of Fe and Co aluminides and silicides with their electronic structures

The background corrected valence band XPS spectra and the electronic structures of FeAl, FeSi, CoAl and CoSi were studied. Clean surfaces of the polycrystalline samples were obtained by in situ fracturing of the samples in an XPS spectrometer. The energy loss parts of the Fe 2p, Co 2p and valence band spectra were removed by the deconvolution method using Al 2s or Si 2s spectra as response functions. CoAl exhibited a satellite peak in the Co 2p region, but the other compounds had no clear satellite peaks in the Co 2p and Fe 2p regions. The experimentally background corrected valence band spectra were compared with the calculated spectra using the first-principle band calculation. There were large discrepancies between the spectra above the binding energy of 5 eV. These indicated that the experimental spectra could not be explained by the electronic structures of the ground states alone.     

3‐Benzyl­oxy‐16‐[(N‐methyl‐N‐phenyl­amino)­methyl­idene]­estra‐1,3,5(10)‐trien‐17‐one

In the title compound, C₃₃H₃₅NO₂, the five‐membered ring adopts a half‐chair conformation. The N‐methyl‐N‐phenyl‐substituted keto–enamine moiety shows a comparatively long Csp²—N bond.     

Production of Nuclear Polarization of Na Isotopes at ISAC/TRIUMF and its Hyperfine Interaction

Hyperfine interactions of Na isotopes in single crystals have been studied using highly nuclear polarized ^{20,21,26,27,28}Na beams provided by ISAC/TRIUMF. The degree of polarization kept in the crystals, the spin-lattice relaxation times, the electric quadrupole coupling constants and the initial distribution of the populations were measured. Such knowledge is indispensable for the application of the hyperfine interactions in the study of precision measurements such as the nuclear structure through nuclear moments and the fundamental symmetries.