Tohoku University

About: Tohoku University is a education organization based out in Sendai, Japan. It is known for research contribution in the topics: Magnetization & Population. The organization has 72116 authors who have published 170791 publications receiving 3941714 citations. The organization is also known as: Tōhoku daigaku.

A White Paper on keV sterile neutrino Dark Matter

Abstract: We present a comprehensive review of keV-scale sterile neutrino Dark Matter, collecting views and insights from all disciplines involved—cosmology, astrophysics, nuclear, and particle physics—in each case viewed from both theoretical and experimental/observational perspectives. After reviewing the role of active neutrinos in particle physics, astrophysics, and cosmology, we focus on sterile neutrinos in the context of the Dark Matter puzzle. Here, we first review the physics motivation for sterile neutrino Dark Matter, based on challenges and tensions in purely cold Dark Matter scenarios. We then round out the discussion by critically summarizing all known constraints on sterile neutrino Dark Matter arising from astrophysical observations, laboratory experiments, and theoretical considerations. In this context, we provide a balanced discourse on the possibly positive signal from X-ray observations. Another focus of the paper concerns the construction of particle physics models, aiming to explain how sterile neutrinos of keV-scale masses could arise in concrete settings beyond the Standard Model of elementary particle physics. The paper ends with an extensive review of current and future astrophysical and laboratory searches, highlighting new ideas and their experimental challenges, as well as future perspectives for the discovery of sterile neutrinos.

Simultaneous Absolute Protein Quantification of Transporters, Cytochromes P450, and UDP-Glucuronosyltransferases as a Novel Approach for the Characterization of Individual Human Liver: Comparison with mRNA Levels and Activities

Abstract: The purpose of the present study was to determine the absolute protein expression levels of multiple drug-metabolizing enzymes and transporters in 17 human liver biopsies, and to compare them with the mRNA expression levels and functional activities to evaluate the suitability of the three measures as parameters of hepatic metabolism. Absolute protein expression levels of 13 cytochrome P450 (P450) enzymes, NADPH-P450 reductase (P450R) and 6 UDP-glucuronosyltransferase (UGT) enzymes in microsomal fraction, and 22 transporters in plasma membrane fraction were determined using liquid chromatography/tandem mass spectrometry. CYP2C9, CYP2E1, CYP3A4, CYP2A6, UGT1A6, UGT2B7, UGT2B15, and P450R were abundantly expressed (more than 50 pmol/mg protein) in human liver microsomes. The protein expression levels of CYP3A4, CYP2B6, and CYP2C8 were each highly correlated with the corresponding enzyme activity and mRNA expression levels, whereas for other P450s, the protein expression levels were better correlated with the enzyme activities than the mRNA expression levels were. Among transporters, the protein expression level of organic anion-transporting polypeptide 1B1 was relatively highly correlated with the mRNA expression level. However, other transporters showed almost no correlation. These findings indicate that protein expression levels determined by the present simultaneous quantification method are a useful parameter to assess differences of hepatic function between individuals.

Systematic errors in future weak-lensing surveys: requirements and prospects for self-calibration

Abstract: We study the impact of systematic errors on planned weak-lensing surveys and compute the requirements on their contributions so that they are not a dominant source of the cosmological parameter error budget. The generic types of error we consider are multiplicative and additive errors in measurements of shear, as well as photometric redshift errors. In general, more powerful surveys have stronger systematic requirements. For example, for a SuperNova/Acceleration Probe (SNAP)-type survey the multiplicative error in shear needs to be smaller than 1 per cent of the mean shear in any given redshift bin, while the centroids of photometric redshift bins need to be known to be better than 0.003. With about a factor of 2 degradation in cosmological parameter errors, future surveys can enter a self-calibration regime, where the mean systematic biases are self-consistently determined from the survey and only higher order moments of the systematics contribute. Interestingly, once the power-spectrum measurements are combined with the bispectrum, the self-calibration regime in the variation of the equation of state of dark energy w a is attained with only a 20‐30 per cent error degradation. Ke yw ords: cosmological parameters ‐ large-scale structure of Universe.

Soft magnetic properties of nanocrystalline bcc Fe‐Zr‐B and Fe‐M‐B‐Cu (M=transition metal) alloys with high saturation magnetization (invited)

Abstract: A mostly single bcc phase with nanoscale grain sizes of 10 to 20 nm was found to form by annealing amorphous Fe‐Zr‐B, Fe‐Hf‐B, and Fe‐M‐B‐Cu(M=Ti, Zr, Hf, Nb, and Ta) alloys for 36 ks in the range of 723 to 923 K The high permeability (μe) above 10 000 at 1 kHz combined with high saturation magnetization (Bs) above 15 T was obtained for the bcc alloys The highest μe and Bs values reach 14 000 and 17 T for Fe91Zr7B2, 20 000 and 155 T for Fe87Zr7B5Cu1, and 48 000 and 152 T for Fe86Zr7B6Cu1 Magnetostriction (λs) decreases significantly by the phase transition from amorphous to bcc phase and is measured to be 1 × 10−6 for the bcc Fe86Zr7B6Cu1 alloy The small λs as well as the small grain size is concluded to be the reason for the good soft magnetic properties The lattice parameter of this bcc phase is 02870 nm being larger than that of pure α‐Fe The small λs seems to be achieved by the dissolution of solute elements above an equilibrium solubility limit The bcc Fe86Zr7B6Cu1 alloy also shows the l

Vacancy-induced magnetism in ZnO thin films and nanowires

Abstract: Extensive calculations based on density functional theory have been carried out to understand the origin of magnetism in undoped ZnO thin films as found in recent experiments. The observed magnetism is confirmed to be due to Zn, instead of O, vacancy. The main source of the magnetic moment, however, arises from the unpaired 2p electrons at O sites surrounding the Zn vacancy with each nearest-neighbor O atom carrying a magnetic moment ranging from 0.490 to 0.740 B. Moreover, the study of vacancy-vacancy interactions indicates that in the ground state, the magnetic moments induced by Zn vacancies prefer to ferromagnetically couple with the antiferromagnetic state lying 44 meV higher in energy. Since this is larger than the thermal energy at room temperature, the ferromagnetic state can be stable against thermal fluctuations. Calculations and discussions are also extended to ZnO nanowires that have larger surface to volume ratio. Here, the Zn vacancies are found to lead to the ferromagnetic state too. The present theoretical study not only demonstrates that ZnO samples can be magnetic even without transition-metal doping but also suggests that introducing Zn vacancy is a natural and an effective way to fabricate magnetic ZnO nanostructures. In addition, vacancy mediated magnetic ZnO nanostructures may have certain advantages over transition-metal doped systems in biomedical applications.