Domain structure in CoFeB thin films with perpendicular magnetic anisotropy

Domain structures in CoFeB-MgO thin films with a perpendicular easy magnetization axis were observed by magneto-optic Kerr-effect microscopy at various temperatures. The domain wall surface energy was obtained by analyzing the spatial period of the stripe domains and fitting established domain models to the period. In combination with SQUID measurements of magnetization and anisotropy energy, this leads to an estimate of the exchange stiffness and domain wall width in these films. These parameters are essential for determining whether domain walls will form in patterned structures and devices made of such materials

Accumulation of plutonium in mammalian wildlife tissues: comparison of recent data with the ICRP distribution models

We examined the distribution of plutonium (Pu) in the tissues of mammalian wildlife to address the paucity of such data under environmental exposure conditions. Pu activity concentrations were measured in Macropus rufus (red kangaroo), Oryctolagus cuniculus (European rabbit), and Pseudomys hermannsburgensis (sandy inland mouse)inhabiting the relatively undisturbed, semi-arid conditions at the former Taranaki weapons test site at Maralinga, Australia. Of the absorbed Pu (distributed via circulatory and lymph systems) accumulation was foremost in bone (83% ±10% SD), followed by muscle (9% ±10%), liver (7% ±7%), kidneys (0.5% ±0.3%), and heart (0.4% ±0.4%). The bone values are higher than those reported in ICRP 19 and 48 (45-50% bone), while the liver values are lower than ICRP values (30-45% liver). The ICRP values were based on data dominated by relatively soluble forms of Pu, including prepared solutions and single-atom ions produced by decay following the volatilisation of uranium during nuclear detonation (fallout Pu, ICRP 1986). In contrast, the Maralinga data relates to low-soluble forms of Pu used in tests designed to simulate accidental release and dispersal. We measured Pu in lung, GI-tract and the skin and fur as distinct from the absorbed Pu in bone, liver, muscle, and kidneys. Compared with the mean absorbed activity concentrations, the results for lung tissues were higher by up to one order of magnitude, and those in the GI tract contents and the washed skin/fur were higher by more than two orders of magnitude. These elevated levels are consistent with the presence of low-soluble Pu, including particulate forms, which pass through, or adhere upon, certain organs, but are not readily absorbed into the bloodstream. This more transitory Pu can provide dose to the lung and GI tract organs, as well as provide potential transfer of contamination when consumed in predator-prey food chains, or during human foodstuff consumption. For example, activity concentrations in O. cuniculus edible samples prepared according to traditional aboriginal methods were more than two orders of magnitude higher than in muscle alone. The increase was due to inclusion of GI tract components and contents in the traditional method. Our results provide new insights into the sequestration of Pu in mammalian tissues under environmental exposure conditions. These results contrast with those related to the specific forms of Pu and exposure conditions upon which the ICRP models were based. However, they provide data relevant to the assessment of key environmental legacy waste sites, and of potential release scenarios for the low-soluble oxide forms in the growing worldwide inventory of Pu associated with power production

Batch sorption and spectroscopic speciation studies of neptunium uptake by montmorillonite and corundum

Peer reviewe

Implications and consequences of ferromagnetism universally exhibited by inorganic nanoparticles

Occurrence of surface ferromagnetism in inorganic nanoprticles as a universal property not only explains many of the unusual magnetic features of oxidic thin films, but also suggests its possible use in creating new materials, as exemplified by multiferroic BaTiO3 nanoparticles. While the use of Mn-doped ZnO and such materials in spintronics appears doubtful, it is possible to have materials exhibiting coexistence of (bulk) superconductivity with (surface) ferromagnetism.Comment: 11 pages, 3 figures, 1 tabl

Thermal stress induces glycolytic beige fat formation via a myogenic state.

Environmental cues profoundly affect cellular plasticity in multicellular organisms. For instance, exercise promotes a glycolytic-to-oxidative fibre-type switch in skeletal muscle, and cold acclimation induces beige adipocyte biogenesis in adipose tissue. However, the molecular mechanisms by which physiological or pathological cues evoke developmental plasticity remain incompletely understood. Here we report a type of beige adipocyte that has a critical role in chronic cold adaptation in the absence of β-adrenergic receptor signalling. This beige fat is distinct from conventional beige fat with respect to developmental origin and regulation, and displays enhanced glucose oxidation. We therefore refer to it as glycolytic beige fat. Mechanistically, we identify GA-binding protein α as a regulator of glycolytic beige adipocyte differentiation through a myogenic intermediate. Our study reveals a non-canonical adaptive mechanism by which thermal stress induces progenitor cell plasticity and recruits a distinct form of thermogenic cell that is required for energy homeostasis and survival

Layer thickness dependence of the current induced effective field vector in Ta|CoFeB|MgO

The role of current induced effective magnetic field in ultrathin magnetic heterostructures is increasingly gaining interest since it can provide efficient ways of manipulating magnetization electrically. Two effects, known as the Rashba spin orbit field and the spin Hall spin torque, have been reported to be responsible for the generation of the effective field. However, quantitative understanding of the effective field, including its direction with respect to the current flow, is lacking. Here we show vector measurements of the current induced effective field in Ta|CoFeB|MgO heterostructrures. The effective field shows significant dependence on the Ta and CoFeB layers' thickness. In particular, 1 nm thickness variation of the Ta layer can result in nearly two orders of magnitude difference in the effective field. Moreover, its sign changes when the Ta layer thickness is reduced, indicating that there are two competing effects that contribute to the effective field. The relative size of the effective field vector components, directed transverse and parallel to the current flow, varies as the Ta thickness is changed. Our results illustrate the profound characteristics of just a few atomic layer thick metals and their influence on magnetization dynamics

Alcohol consumption and cigarette smoking in relation to high frequency of p53 protein accumulation in oesophageal squamous cell carcinoma in the Japanese

We investigated levels of p53 protein expression in Japanese patients with oesophageal squamous cell carcinoma. A significantly larger proportion of heavy alcohol drinkers and cigarette smokers was evident in the p53-positive group. The combination of drinking and smoking was associated with a high frequency of p53 protein accumulation. © 2000 Cancer Research Campaig

BCAA catabolism in brown fat controls energy homeostasis through SLC25A44.

Branched-chain amino acid (BCAA; valine, leucine and isoleucine) supplementation is often beneficial to energy expenditure; however, increased circulating levels of BCAA are linked to obesity and diabetes. The mechanisms of this paradox remain unclear. Here we report that, on cold exposure, brown adipose tissue (BAT) actively utilizes BCAA in the mitochondria for thermogenesis and promotes systemic BCAA clearance in mice and humans. In turn, a BAT-specific defect in BCAA catabolism attenuates systemic BCAA clearance, BAT fuel oxidation and thermogenesis, leading to diet-induced obesity and glucose intolerance. Mechanistically, active BCAA catabolism in BAT is mediated by SLC25A44, which transports BCAAs into mitochondria. Our results suggest that BAT serves as a key metabolic filter that controls BCAA clearance via SLC25A44, thereby contributing to the improvement of metabolic health

Anomalous Transport Phenomena in Fermi Liquids with Strong Magnetic Fluctuations

In many strongly correlated electron systems, remarkable violation of the relaxation time approximation (RTA) is observed. The most famous example would be high-Tc superconductors (HTSCs), and similar anomalous transport phenomena have been observed in metals near their antiferromagnetic (AF) quantum critical point (QCP). Here, we develop a transport theory involving resistivity and Hall coefficient on the basis of the microscopic Fermi liquid theory, by considering the current vertex correction (CVC). In nearly AF Fermi liquids, the CVC accounts for the significant enhancements in the Hall coefficient, magnetoresistance, thermoelectric power, and Nernst coefficient in nearly AF metals. According to the numerical study, aspects of anomalous transport phenomena in HTSC are explained in a unified way by considering the CVC, without introducing any fitting parameters; this strongly supports the idea that HTSCs are Fermi liquids with strong AF fluctuations. In addition, the striking \omega-dependence of the AC Hall coefficient and the remarkable effects of impurities on the transport coefficients in HTSCs appear to fit naturally into the present theory. The present theory also explains very similar anomalous transport phenomena occurring in CeCoIn5 and CeRhIn5, which is a heavy-fermion system near the AF QCP, and in the organic superconductor \kappa-(BEDT-TTF).Comment: 100 pages, Rep. Prog. Phys. 71, 026501 (2008

Modeling and simulation of polycrystalline ZnO thin-film transistors

Thin film transistors (TFTs) made of transparent channel semiconductors such as ZnO are of great technological importance, because their insensitivity to visible light makes device structures simple. In fact, several demonstrations are made on ZnO TFT achieving reasonably good field effect mobilities of 1-10 cm2/Vs, but reveal insufficient device performances probably due to the presence of dense grain boundaries. We have modeled grain boundaries in ZnO thin film transistors (TFTs) and performed device simulation using a two-dimensional device simulator for understanding the grain boundary effects on the device performance. Actual polycrystalline ZnO TFT modeling is commenced with considering a single grain boundary in the middle of the TFT channel formulating with a Gaussian defect distribution localized in the grain boundary. A double Shottky barrier is formed in the grain boundary and its barrier height are analyzed as functions of defect density and gate bias. The simulation is extended to the TFTs with many grain boundaries to quantitatively analyze the potential profiles developed along the channel. One of the big contrasts of polycrystalline ZnO TFT compared with a polycrystalline Si TFT is that much smaller nanoscaled grain size induces heavy overlap of double Shottky barriers. Through the simulation, we can estimate the total trap state density localized in the grain boundaries for a polycrystalline ZnO by knowing apparent mobility and grain size in the device.Comment: Submitted to Journal of Applied Physic