Synthesis and electrochemical properties of LiFePO4/carbon nanocomposites in polyol medium.

LiFePO4/Carbon nanocomposites with varying amounts of carbon were synthesized using polyol process without any further heating as a post step. The X-ray diffraction patterns of all samples were indexed on the basis of orthorhombic olivine-type structure. The field emission-TEM images of composites with the amount of 3 approximately 15 wt% carbon showed the average sizes of 45 approximately 80 nm with nanorod shape surrounded by carbon. The initial discharge curves of LiFePO4/Carbon show 166, 157, 142, and 119 mAh/g capacities at a current density of 0.1 mA/cm2 in the voltage range of 2.5-4.2 V, respectively, without capacity fading and excellent cycle retentions during the 20 cycles. Especially, the sample of amount of 3 wt% carbon shows the excellent high rate performances at 15 and 30 C rates with high capacity retention compared with previously reported results of high temperature processed results, due to the existence of conductive agents such as carbon which suppresses particle growth and exhibits improved electronic conductivity and lithium ion diffusivity, simultaneously.

Synthesis and electrochemical properties of LiMPO4 (M = Fe, Mn, Co) nanocrystals in polyol medium.

Olivine structured LiMPO4 (M = Fe, Mn, Co) was synthesized by the solvothermal process using a polyol medium of diethylene glycol (DEG) without any further heating as a post procedure. The synthesized LiMPO4 nanoparticles exhibited an average length of 200 approximately 400 nm, width of 200 approximately 300 nm, and thickness of 20 approximately 50 nm, and with well dispersed plate and rod morphologies. The Rietveld-refined X-ray diffraction (XRD) pattern of LiFePO4 exhibited a good fit with an olivine structure (space group: Pnma) and no undesirable impurity phases. The LiFePO4 nanocrystals showed a reversible capacity of 167 mAh/g, equating to a utilization efficiency of 98% of its theoretical capacity, with a good cyclability over an extended range up to 40 cycles.

Parallel propagating electromagnetic waves in magnetized quantum electron plasmas with finite temperature.

We studied parallel propagating electromagnetic waves in a magnetized quantum electron plasma of finite temperature, as an extension of our previous study on a zero temperature plasma. We obtained simple analytic dispersion relations in the long wavelength limit that included the thermal effect as correction terms to the zero temperature results. As in the zero temperature case, the lower branch of the R wave showed significant damping and became ill-defined at short wavelengths. Quantum effects seemed to give qualitative changes, such as the appearance of anomalous dispersion regions, to the classical dispersion relations when v_{F}/v_{th}≤0.2 for a set of exemplary parameters of v_{F}=0.1c and ω_{ce}/ω_{pe}=0.05 was used. We also noted that introduction of the Planck constant in the quantum Vlasov equation changed the shape of the anomalous dispersion region qualitatively, by forming a normal dispersion region in the middle of the original single broad anomalous dispersion region.

Early hypomethylation of 2'-O-ribose moieties in hepatocyte cytoplasmic ribosomal RNA underlies the protein synthetic defect produced by CCl4.

Carbon tetrachloride (CCl4) treatment of rats produces an early defect in methylation of hepatocyte ribosomal RNA, which occurs concurrently with a defect in the protein synthetic capacity of isolated ribosomes. The CCl4-induced methylation defect is specific for the 2'-O-ribose position, and a corresponding proportional increase in m7G base methylation occurs in vivo. Undermethylated ribosomal subunits (rRNA) from CCl4-treated preparations can be methylated in vitro to a much greater extent than those from control preparations, and in vitro methylation restores their functional capacity. In vitro methylation of treated ribosomal subunits (which restores functional capacity) occurs at 2'-O-ribose positions (largely G residues). In contrast, in vitro methylation of control ribosomal subunits (which does not affect functional activity) represents base methylation as m7G, sites which are apparently methylated in treated preparations in vivo. Methylation/demethylation of 2'-O-ribose sites in rRNA exposed on the surface of cytoplasmic ribosomal subunits may represent an important cellular mechanism for controlling protein synthesis in quiescent hepatocytes, and it appears that CCl4 disrupts protein synthesis by inhibiting this 2'-O-ribose methylation.

Giant piezoelectric resistance in ferroelectric tunnel junctions.

The effect of an applied mechanical stress on the tunneling conductance of a ferroelectric tunnel barrier between substrates and dissimilar electrodes is studied. Using a thermodynamic model and taking into account polarization charge screening in the electrodes and the near-surface inhomogeneous polarization distribution, the tunneling conductance is calculated as a function of the applied stress. It is found that reversing an applied stress can also change the tunnel barrier sufficiently to produce an effect similar to the giant electro-resistance one due to polarization reversal, which is particularly significant near the stress-dependent paraelectric/ferroelectric phase transition. Indeed, the sensitivity is adequate for high-sensitivity electronic and mechanical sensors, memories and other nanodevices.

Parallel algorithm for spin and spin-lattice dynamics simulations.

To control numerical errors accumulated over tens of millions of time steps during the integration of a set of highly coupled equations of motion is not a trivial task. In this paper, we propose a parallel algorithm for spin dynamics and the newly developed spin-lattice dynamics simulation [P. W. Ma, Phys. Rev. B 78, 024434 (2008)]. The algorithm is successfully tested in both types of dynamic calculations involving a million spins. It shows good stability and numerical accuracy over millions of time steps (approximately 1 ns) . The scheme is based on the second-order Suzuki-Trotter decomposition (STD). The usage can avoid numerical energy dissipation despite the trajectory and machine errors. The mathematical base of the symplecticity, for properly decomposed evolution operators, is presented. Due to the noncommutative nature of the spin in the present STD scheme, a unique parallel algorithm is needed. The efficiency and stability are tested. It can attain six to seven times speed up when eight threads are used. The run time per time step is linearly proportional to the system size.

Erythrocyte catabolism by macrophages in vitro. The effect of hydrocortisone on erythrophagocytosis and on the induction of heme oxygenase.

Phagocytosis of erythrocytes was studied in vitro in an incubation system consisting of rat peritoneal macrophages and antibody-coated (59)Fe-labeled erythrocytes. The system was characterized in terms of the rate and magnitude of erythrophagocytosis, determined by the interiorization of the (59)Fe label. On incubation of 150 x 10(6) macrophages with 75 x 10(6) antibodycoated erythrocytes, erythrophagocytosis began within a few minutes and was essentially completed after 2 h when 50% of the offered red cells had been ingested by the macrophages. Heme oxygenase (HO) activity, which is very low in native macrophages, increased 4- to 10- fold in response to the ingested erythrocytes; this enzyme stimulation occurred with a delay of 3 h in relation to erythrophagocytosis. Actinomycin D or puromycin prevented the increase of HO activity without affecting erythrophagocytosis, which suggests that the enzyme stimulation was due to substrate-mediated enzyme induction. Hydrocortisone (HC) (0.1 mg/ml medium) dissociated erythrophagocytosis from HO induction, leaving the former unimpaired but completely suppressing the latter. The suppressive effect of HC on the enzyme induction was completely prevented by 5 mg glucose and 0.02 U insulin/ml of the medium. In macrophages engaged in erythrophagocytosis. HC also lowered glucose removal from the medium and reduced formation of (14)CO(2) from [1-(14)C]glucose. These results suggest that induction of HO in macrophages by the hemoglobin of ingested erythrocytes requires intact transport or metabolism of glucose. Glucose utilization appears to be impaired by HC, but is restored by additional glucose and insulin. The findings suggest that plasma steroid concentrations in the pharmacological range could reduce bilirubin formation in phagocytic cells in vivo without affecting the sequestration and degradation of erythrocytes. This provides a possible explanation for the observation that in patients with hepatogenous jaundice, steroids often lower the serum bilirubin level.

Stimulation of heme oxygenase in macrophages and liver by endotoxin.

In rat peritoneal macrophages, engaged in erythrophagocytosis in vitro, endotoxin stimulated heme oxygenase (HO) activity, which was additive to the substrate-mediated enzyme induction produced by the ingested erythrocyte hemoglobin. Endotoxin neither appeared to injure the erythrocytes, nor did it enhance the rate of erythrophagocytosis. In intact rats, HO activity in both parenchymal and sinusoidal cells of the liver was increased after treatment with endotoxin. It is likely that endotoxin directly stimulates HO activity, a process which may account for the reported rise in bilirubin formation in endotoxin-treated animals. The effect of endotoxin on HO may represent part of the general activation of phagocytic cells by endotoxin.

Intestinal absorption of hemoglobin iron-heme cleavage by mucosal heme oxygenase.

Hemoglobin and myoglobin are a major source of dietary iron in man. Heme, separated from these hemoproteins by intraluminal proteolysis, is absorbed intact by the intestinal mucosa. The absorbed heme is cleaved in the mucosal cell releasing inorganic iron. Although this mucosal heme-splitting activity initially was ascribed to xanthine oxidase, we investigated the possibility that it is catalyzed by microsomal heme oxygenase, an enzyme which converts heme to bilirubin, CO, and inorganic iron. Microsomes prepared from rat intestinal mucosa contain enzymatic activity similar to that of heme oxygenase in liver and spleen. The intestinal enzyme requires NADPH; is completely inhibited by 50% CO; and produces bilirubin IX-alpha, identified spectrophotometrically and chromatographically. Moreover, duodenal heme oxygenase was shown to release inorganic (55)Fe from (55)Fe-heme. Along the intestinal tract, enzyme activity was found to be highest in the duodenum where hemoglobin iron absorption is reported to be most active. Furthermore, when rats were made iron deficient, duodenal heme oxygenase activity and hemoglobin-iron absorption rose to a comparable extent. Upon iron repletion of iron-deficient animals, duodenal enzyme activity returned towards control values. In contrast to heme oxygenase, duodenal xanthine oxidase activity fell sharply in iron deficiency and rose towards base line upon iron repletion. Our findings suggest that mucosal heme oxygenase catalyzes the cleavage of heme absorbed in the intestinal mucosa and thus plays an important role in the absorption of hemoglobin iron. The mechanisms controlling this intestinal enzyme activity and the enzyme's role in the overall regulation of hemoglobin-iron absorption remain to be defined.

Quantum statistical effects in the mass transport of interstitial solutes in a crystalline solid.

The impact of quantum statistics on the many-body dynamics of a crystalline solid at finite temperatures containing an interstitial solute atom (ISA) is investigated. The Mori-Zwanzig theory allows the many-body dynamics of the crystal to be formulated and solved analytically within a pseudo-one-particle approach using the Langevin equation with a quantum fluctuation-dissipation relation (FDR) based on the Debye model. At the same time, the many-body dynamics is also directly solved numerically via the molecular dynamics approach with a Langevin heat bath based on the quantum FDR. Both the analytical and numerical results consistently show that below the Debye temperature of the host lattice, quantum statistics significantly impacts the ISA transport properties, resulting in major departures from both the Arrhenius law of diffusion and the Einstein-Smoluchowski relation between the mobility and diffusivity. Indeed, we found that below one-third of the Debye temperature, effects of vibrations on the quantum mobility and diffusivity are both orders-of-magnitude larger and practically temperature independent. We have shown that both effects have their physical origin in the athermal lattice vibrations derived from the phonon ground state. The foregoing theory is tested in quantum molecular dynamics calculation of mobility and diffusivity of interstitial helium in bcc W. In this case, the Arrhenius law is only valid in a narrow range between ∼300 and ∼700 K. The diffusivity becomes temperature independent on the low-temperature side while increasing linearly with temperature on the high-temperature side.

Apparent differential response of nuclear envelope cytochrome P-450 following phenobarbital induction arising from a preferential loss during gradient purification.

We have investigated the response of rat liver nuclear, nuclear envelope, and microsomal cytochrome P-450 (or P-448) to various treatments. Responses of these subcellular fractions to 3-methylcholanthrene pretreatment were generally similar. In endoplasmic reticulum preparations, we observed an increase in cytochrome P-450 content following phenobarbital pretreatment, which was reduced by subsequent thioacetamide treatment. Nuclear envelope cytochrome P-450 was apparently not modulated by these treatments, although nuclear cytochrome P-450 content was increased by phenobarbital. When endoplasmic reticulum preparations were subjected to treatments paralleling those used in nuclear envelope purification, we found a preferential loss of cytochrome P-450 from phenobarbital-pretreated preparations, with a loss of camphor-binding ability. The data point to potential problems with use of isolated nuclear envelopes as a representative model for nuclear metabolism of carcinogens, including low total recoveries and enrichments, and the potential for selective or differential recovery of cytochrome P-450 populations following various modes of induction or reduction.

Quantum statistics and anharmonicity in the thermodynamics of spin waves in ferromagnetic metals.

The average energy needed to create a magnon is high in ferromagnetic metals due to the high-strength spin stiffness, which results in strong quantization effects that could be important even at thousands of degrees. To take into account quantum statistics at such high temperatures, the associated effects of anharmonicity of the spin vibrations must be taken into account. In addition to the complex nature of such effects, anharmonicity also affects the occupation of the density of state of the vibration states in the context of quantum statistics. Thus, an unoccupied vibration state might become occupied when its spring stiffness is substantially reduced with anharmonicity. Combined effects of quantum statistics and anharmonicity are expected. In this regard, the thermodynamics of ferromagnetic metals are investigated in this paper through the example of bcc iron between 10 and 1400 K. Theoretical analysis and spin-lattice dynamic simulations are performed, through which the physics behind the complex and dramatic temperature dependence of the thermodynamic functions of bcc iron is understood.

Rapid exploration of alternatives via chaos.

Temporary chaos facilitates a rapid exploration of alternative asymptotic possibilities. The phenomenon of alternative-exploration via chaos is shown to have a finite probability of occurrence for a class of dynamical systems, the evolution of which is described by (complex) analytic maps. The ability to explore alternatives confers an adaptive advantage, and the possible relevance of temporary chaos to rapid mutations is discussed.

Necrolytic migratory erythema in glucagonoma syndrome.

A 32-year-old female Chinese presenting with typical features of necrolytic migratory erythema due to glucagonoma syndrome is reported. The clinical, biochemical, histopathological, and electron-microscopic findings are described. Various different aspects of this rare entity are discussed.

TBX21 participates in innate immune response by regulating Toll-like receptor 2 expression in Streptococcus pneumoniae infections.

Nasopharyngeal carriage of Streptococcus pneumoniae (pneumococcus) plays an important role in the development of invasive diseases, and is also critically involved in setting up respiratory bacterial and viral infections. We previously reported that pneumococcus, one of the commonly carried bacteria in the nasopharynx, regulates non-typeable Haemophilus influenzae-induced inflammation by upregulating the expression of Toll-like receptor 2 (TLR2). However, the underlying molecular mechanisms by which TLR2 expression is regulated during pneumococcal infections have not yet been well characterized. TBX21 is an important transcription factor of adaptive immunity, but there is an increasing body of evidence pointing to a role in regulating innate immunity. The expression of TBX21 was reported in epithelial cells, but the expression and role of TBX21 in respiratory epithelium, especially for regulating TLR2, has not yet been studied. In this study, we found that pneumococcus upregulates TBX21 expression in the respiratory epithelium. The effect of pneumococcus on TBX21 expression was dependent on its cytoplasmic toxin, pneumolysin. In addition, epithelial TBX21 expression was not regulated by the gram-negative bacterium non-typeable Haemophilus influenzae, peptidoglycan or endotoxin. Deficiency of TBX21 in mice or knocking down TBX21 in epithelial cells suppressed pneumococcus-induced TLR2 expression, but not that of TLR4 or TLR9. These results indicate that the adaptive immune regulator TBX21 participates in regulating innate immune responses, through regulation of TLR2 expression during pneumococcal infections.

Surveillance of enteric viruses and coliphages in a tropical urban catchment.

An assessment of the occurrence and concentration of enteric viruses and coliphages was carried out in highly urbanized catchment waters in the tropical city-state of Singapore. Target enteric viruses in this study were noroviruses, adenoviruses, astroviruses and rotaviruses. In total, 65 water samples were collected from canals and the reservoir of the Marina catchment on a monthly basis over a period of a year. Quantitative PCR (qPCR) and single agar layer plaque assay (SAL) were used to enumerate target enteric viruses and coliphages in water samples, respectively. The most prevalent pathogen were noroviruses, detected in 37 samples (57%), particularly norovirus genogroup II (48%), with a mean concentration of 3.7 × 10(2) gene copies per liter. Rotavirus was the second most prevalent virus (40%) with a mean concentration of 2.5 × 10(2) GC/L. The mean concentrations of somatic and male-specific coliphages were 2.2 × 10(2) and 1.1 × 10(2) PFU/100 ml, respectively. The occurrence and concentration of each target virus and the ratio of somatic to male-specific coliphages varied at different sampling sites in the catchment. For sampling sites with higher frequency of occurrence and concentration of viruses, the ratio of somatic to male-specific coliphages was generally much lower than other sampling sites with lower incidences of enteric viruses. Overall, higher statistical correlation was observed between target enteric viruses than between enteric viruses and coliphages. However, male-specific coliphages were positively correlated with norovirus concentrations. A multi-level integrated surveillance system, which comprises the monitoring of bacterial indicators, coliphages and selected enteric viruses, could help to meet recreational and surface water quality criteria in a complex urbanized catchment.

Controllability of vortex domain structure in ferroelectric nanodot: fruitful domain patterns and transformation paths.

Ferroelectric vortex domain structure which exists in low-dimensional ferroelectrics is being intensively researched for future applications in functional nanodevices. Here we demonstrate that adjusting surface charge screening in combination with temperature can provide an efficient way to gain control of vortex domain structure in ferroelectric nanodot. Systematical simulating experiments have been conducted to reveal the stability and evolution mechanisms of domain structure in ferroelectric nanodot under various conditions, including processes of cooling-down/heating-up under different surface charge screening conditions, and increasing/decreasing surface charge screening at different temperatures. Fruitful phase diagrams as functions of surface screening and temperature are presented, together with evolution paths of various domain patterns. Calculations discover up to 25 different kinds of domain patterns and 22 typical evolution paths of phase transitions. The fruitful controllability of vortex domain structure by surface charge screening in combination with temperature should shed light on prospective nanodevice applications of low-dimensional ferroelectric nanostructures.

Temperature for a dynamic spin ensemble.

In molecular dynamics simulations, temperature is evaluated, via the equipartition principle, by computing the mean kinetic energy of atoms. There is no similar recipe yet for evaluating temperature of a dynamic system of interacting spins. By solving semiclassical Langevin spin-dynamics equations, and applying the fluctuation-dissipation theorem, we derive an equation for the temperature of a spin ensemble, expressed in terms of dynamic spin variables. The fact that definitions for the kinetic and spin temperatures are fully consistent is illustrated using large-scale spin dynamics and spin-lattice dynamics simulations.

Pulse-loaded ferroelectric nanowire as an alternating current source.

The behavior of an uniaxially pulse-loaded ferroelectric nanowire is simulated using a Landau-Ginzburg type thermodynamic model. Our results show that under a load of suitable magnitude and frequency, an appropriately dimensioned ferroelectric nanowire can produce a sizable alternating current voltage, sufficient for applications as a nanopower source for energy harvesting, or as an effective nanomechanical sensor.