Relation between the separable and one-boson-exchange potential for the covariant Bethe-Salpeter equation

We investigate the relation between the rank I separable potential for the covariant Bethe-Salpeter equation and the one-boson-exchange potential. After several trials of the parameter choices, it turns out that it is not always possible to reproduce the phase-shifts calculated from a single term of the one-boson-exchange potential especially of the $\sigma$-exchange term, separately by the rank I separable potential. Instead, it is shown that the separable potential is useful to parameterize the total nucleon-nucleon interaction.Comment: 10 pages, 8 figures, to appear in J.Phys.

Search for long-lived massive particles in extensive air showers

Air showers containing delayed sub-showers which may be produced by a long-lived massive particle have been investigated by using twelve detectors. Ten events have been selected out as the candidates. However, a definite conclusion cannot be reached at the present time

Superconductivity in undoped T' cuprates with Tc over 30 K

Undoped cuprates have long been considered to be antiferromagnetic insulators. In this article, however, we report that superconductivity is achieved in undoped T'-RE2CuO4 (RE = Pr, Nd, Sm, Eu, and Gd). Our discovery was performed by using metal-organic decomposition (MOD), an inexpensive and easy-to-implement thin-film process. The keys to prepare the superconducting films are firing with low partial-pressure of oxygen and reduction at low temperatures. The highest Tc of undoped T'-RE2CuO4 is over 30 K, substantially higher than "electron-doped" analogs. Remarkably, Gd2CuO4, even the derivatives of which have not shown superconductivity so far, gets superconducting with Tconset as high as ~ 20 K. The implication of our discovery is briefly discussed.Comment: 22 pages, 5 figures, submitted to Physical Review Letter

Wilson ratio of a Tomonaga-Luttinger liquid in a spin-1/2 Heisenberg ladder

Using micromechanical force magnetometry, we have measured the magnetization of the strong-leg spin-1/2 ladder compound (C$_7$H$_{10}$N)$_2$CuBr$_2$ at temperatures down to 45 mK. Low-temperature magnetic susceptibility as a function of field exhibits a maximum near the critical field H_c at which the magnon gap vanishes, as expected for a gapped one-dimensional antiferromagnet. Above H_c a clear minimum appears in the magnetization as a function of temperature as predicted by theory. In this field region, the susceptibility in conjunction with our specific heat data yields the Wilson ratio R_W. The result supports the relation R_W=4K, where K is the Tomonaga-Luttinger-liquid parameter

Association of testosterone levels with socio-demographic characteristics in a sample of Ugandan men

Background: Testosterone, a male reproductive hormone, affects several physiological processes, such as sperm production, energy, strength, sexual behavior, sleep and the general well being of men. Normal levels of testosterone are necessary to effect these physiological processes. The objective of this study was to study the association between testosterone levels in a sample of Ugandan men with socio-demographic characteristics, and compare the testosterone levels of Ugandan men with that of men in other countries.Methods: Eighty men were enrolled from the medical campus at Makerere University. Blood samples were drawn from 7.00 – 8.00 a.m. and total testosterone was measured using radioimmunoassay. The free and bioavailable testosterone was calculated after measuring sex hormone binding globulin (SHBG) and albumin in the blood samples. Self-administered questionnaires were used to obtain socio-demographic characteristics of the subjects. Biometric measurements including weight, height and waist circumference were also recorded.Results: Serum testosterone levels of Ugandan men were within the normal physiological ranges. Married participants and those with dependents had lower testosterone than unmarried participants and those without dependents respectively. Sexually active participants had lower testosterone levels than those who were not sexually active.Conclusion: Testosterone levels were lower in association with several socio-demographic characteristics including being married, having dependents, and daily coital frequency. Further research is warranted into the relationship between testosterone levels and contributory sexual behavior that may be important in understanding the spread of HIV/AIDS, given its high prevalence in sub-Saharan Africa.Key Words: Testosterone, Socio-demographic Factors, Ugandan Me

Synthesis of infinite-layer LaNiO2 films by metal-organic deposition

We report the synthesis of infinite-layer LaNiO2 thin films by metal organic decomposition. Our work is aimed to synthesize perovskite-like oxides with 3d9 electronic configuration, which is common to high-Tc copper oxides. The 3d9 configuration is very rare in oxides other than cuprates. Ni1+ oxides, even though Ni1+ is an unusual oxidation state, may be one of very few candidates. One example of the Ni1+ phases is infinite-layer LaNiO2. The bulk synthesis of LaNiO2 is difficult, but we demonstrate in this article that the thin-film synthesis of LaNiO2 by metal organic decomposition is rather easy. This is due to the advantage of thin films with a large-surface-to-volume ratio, which makes oxygen diffusion prompt. Resistivity measurements indicate that LaNiO2 is essentially a metal but unfortunately with no trace of superconductivity yet.Comment: 13 pages, 4 figure

Neutron Scattering Study of Temperature-Concentration Phase Diagram of (Cu1-xMgx)GeO3

In doped CuGeO3 systems, such as (Cu1-xZnx)GeO3 and Cu(Ge1-xSix)O3, the spin-Peierls (SP) ordering (T<Tsp) coexists with the antiferromagnetic (AF) phase (T<TN<Tsp). Tsp decreases while TN increases with increasing x in low doping region. For higher x, however, the SP state disappears and only the AF state remains. These features are common for all the doped CuGeO3 systems so far studied, indicating the existence of universal T-x phase diagram. Recently, Masuda et al. carried out comprehensive magnetic susceptibility (chi) measurements of (Cu1-xMgx)GeO3, in which doping concentration can be controlled significantly better than the Zn doped systems. They found that TN suddenly jumps from 3.43 to 3.98K at the critical concentration xc sim 0.023 and that a drop in chi corresponding to the SP ordering also disappears at x>xc. They thus concluded that there is a compositional phase boundary between two distinct magnetic phases. To clarify the nature of two phases, we performed neutron-scattering measurements on (Cu1-xMgx)GeO3 single crystals with various x. Analysis of the data at fixed temperature points as a function of doping concentration has revealed sudden changes of order parameters at the critical concentration xc=0.027 +- 0.001. At finite temperatures below TN, the drastic increase of the AF moment takes place at xc. The spin-Peierls order parameter delta associated with lattice dimerization shows a precipitous decrease at all temperature below Tsp. However, it goes to zero above xc only at the low temperature limit.Comment: 9 pages, 9 figure

Effects of Disorder on the Competition between Antiferromagnetism and Superconductivity

Motivated by the observation of unusual magnetism in Ce_xCu_2Si_2 ($x\sim 1$), we study the effect of disorder, such as Ce vacancy, on the competition between superconductivity (SC) and antiferromagnetism (AF) on the basis of the phenomenological Ginzburg-Landau theory. Assuming that the AF-SC transition is of first order in clean system, we show that a single impurity in the SC state can induce staggered magnetization by suppressing the SC around it. For finite concentration of impurities, the first-order AF-SC boundary in the clean case is replaced by a finite region where the SC and the induced AF moments coexist microscopically with spatially varying order parameters. We argue that spin excitation spectrum in the coexistent state has a dual structure of SC gapped mode and the low-energy spin-wave mode. In accordance with the emergence of AF out of SC ground state, the spectral weight will be transferred from the former mode to the latter, keeping the structure of both modes basically unchanged.Comment: 5 pages, 1 figure, submitted to J. Phys. Soc. Japa

Comparison of data on Mutation Frequencies of Mice Caused by Radiation - Low Dose Model -

We propose LD(Low Dose) model, the extension of LDM model which was proposed in the previous paper [Y. Manabe et al.: J. Phys. Soc. Jpn. 81 (2012) 104004] to estimate biological damage caused by irradiation. LD model takes account of all the considerable effects including cell death effect as well as proliferation, apoptosis, repair. As a typical example of estimation, we apply LD model to the experiment of mutation frequency on the responses induced by the exposure to low levels of ionizing radiation. The most famous and extensive experiments are those summarized by Russell and Kelly [Russell, W. L. & Kelly, E. M: Proc. Natl Acad. Sci. USA 79 (1982) 539-541], which are known as 'Mega-mouse project'. This provides us with important information of the frequencies of transmitted specific-locus mutations induced in mouse spermatogonia stem-cells. It is found that the numerical results of the mutation frequency of mice are in reasonable agreement with the experimental data: the LD model reproduces the total dose and dose rate dependence of data reasonably. In order to see such dose-rate dependence more explicitly, we introduce the dose-rate effectiveness factor (DREF). This represents a sort of preventable effects such as repair, apoptosis and death of broken cells, which are to be competitive with proliferation effect of broken cells induced by irradiation.Comment: subimitting to J. Phys. Soc. Jpn, 32 pages, 8 figure