Structural origin of set-reset processes in Ge15Te83Si2 glass investigated using in situ Raman scattering and transmission electron microscopy

We report here that the structural origin of an easily reversible Ge15Te83Si2 glass can be a promising candidate for phase change random access memories. In situ Raman scattering studies on Ge15Te83Si2 sample, undertaken during the amorphous set and reset processes, indicate that the degree of disorder in the glass is reduced from off to set state. It is also found that the local structure of the sample under reset condition is similar to that in the amorphous off state. Electron microscopic studies on switched samples indicate the formation of nanometric sized particles of c-SiTe2 structure. ©2009 American Institute of Physics

Characterization of protoporphyrin as the physiological regulator of delta-aminolevulinate dehydratase in Neurospora crassa

In Neurospora crassa, the activity of δ-aminolevulinate dehydratase, the second and rate-limiting enzyme of the heme-biosynthetic pathway, is low in normal cells compared to the activity detected in plants, animals and bacteria. The activity is almost undetectable when Neurospora crassa is grown under iron-deficient conditions. The enzyme activity increases strikingly on addition of iron to iron-deficient cultures. This increase can be blocked by the addition of protoporphyrin, the penultimate product of the heme-biosynthetic pathway, to the cultures. The question whether iron directly acts at the genetic level or acts merely by removing protoporphyrin, converting the latter into heme prosthetic groups of hemoproteins, has been investigated by studying the effect of inhibition of heme synthesis on the induction of δ-aminolevulinate dehydratase. It has been found that treatments with levulinic acid or cyanide which inhibit the formation of the porphyrin moiety, induce δ-aminolevulinate dehydratase, whereas treatments which inhibit at a step after protoporphyrin formation (iron-deficiency and cobalt treatment) repress the enzyme. The endogenous levels of protoporphyrin are strictly controlled: a decrease below the optimum level causing induction and an increase above the optimum level leading to repression of δ-aminolevulinate dehydratase. Levulinic acid and cyanide can induce the enzyme in iron-deficient cultures in the absence of added iron, indicating that the metal iron acts only by converting protoporphyrin to heme fixed in hemoproteins in Neurospora crassa. Therefore it is suggested that protoporphyrin is the physiological regulator of δ-aminolevulinate dehydratase in Neurospora crassa.

Curing And Thermal Cycling Processes In Pvc Graphite Thick-Films

Abstract is not available.

On a generalized dynamic model of bi-state social interaction processes

A non-linear model, construed as a generalized version of the models put forth earlier for the study of bi-state social interaction processes, is proposed in this study. The feasibility of deriving the dynamics of such processes is demonstrated by establishing equivalence between the non-linear model and a higher order linear model.

An analytical approach to the study of a class of bi-state social interaction processes

Sufficient conditions for obtaining an equivalent linear model to classes of non-linear, bi-state, social interaction processes are derived. These parametric constraints, when satisfied, permit analytical determination of the dynamics of the non-linear process of social interaction.

Unitary Processes with Independent Increments and Representations of Hilbert Tensor Algebras

The aim of this article is to characterize unitary increment process by a quantum stochastic integral representation on symmetric Fock space. Under certain assumptions we have proved its unitary equivalence to a Hudson-Parthasarathy flow.

Two-temperature accretion around rotating black holes: a description of the general advective flow paradigm in the presence of various cooling processes to explain low to high luminous sources

We investigate viscous two-temperature accretion disc flows around rotating black holes. We describe the global solution of accretion flows with a sub-Keplerian angular momentum profile, by solving the underlying conservation equations including explicit cooling processes self-consistently. Bremsstrahlung, synchrotron and inverse Comptonization of soft photons are considered as possible cooling mechanisms. We focus on the set of solutions for sub-Eddington, Eddington and super-Eddington mass accretion rates around Schwarzschild and Kerr black holes with a Kerr parameter of 0.998. It is found that the flow, during its infall from the Keplerian to sub-Kepleria transition region to the black hole event horizon, passes through various phases of advection: the general advective paradigm to the radiatively inefficient phase, and vice versa. Hence, the flow governs a much lower electron temperature similar to 10(8)-10(9.5) K, in the range of accretion rate in Eddington units 0.01 less than or similar to (M) over dot less than or similar to 100, compared to the hot protons of temperature similar to 10(10.2)-10(11.8) K. Therefore, the solution may potentially explain the hard X-rays and gamma-rays emitted from active galactic nuclei (AGNs) and X-ray binaries. We then compare the solutions for two different regimes of viscosity. We conclude that a weakly viscous flow is expected to be cooling dominated, particularly at the inner region of the disc, compared to its highly viscous counterpart, which is radiatively inefficient. With all the solutions in hand, we finally reproduce the observed luminosities of the underfed AGNs and quasars (e. g. Sgr A*) to ultraluminous X-ray sources (e. g. SS433), at different combinations of input parameters, such as the mass accretion rate and the ratio of specific heats. The set of solutions also predicts appropriately the luminosity observed in highly luminous AGNs and ultraluminous quasars (e. g. PKS 0743-67).

A distinct physiological role of MutY in mutation prevention in mycobacteria

Oxidative damage to DNA results in the occurrence of 7,8-dihydro-B-oxoguanine (8-oxoG) in the genome. In eubacteria, repair of such damage is initiated by two major base-excision repair enzymes, MutM and MutY. We generated a MutY-deficient strain of Mycobacterium smegmatis to investigate the role of this enzyme in DNA repair. The MutY deficiency in M. smegmatis did not result in either a noteworthy susceptibility to oxidative stress or an increase in the mutation rate. However, rifampicin resistant isolates of the MutY-deficient strain showed distinct mutations in the rifampicin-resistance-determining region of rpoB. Besides the expected C to A (or G to T) mutations, an increase in A to C (or T to G) mutations was also observed. Biochemical characterization of mycobacterial MutY (M. smegmatis and M. tuberculosis) revealed an expected excision of A opposite 8-oxoG in DNA. Additionally, excision of G and T opposite 8-oxoG was detected. MutY formed complexes with DNA containing 8-oxoG: A, 8-oxoG: G or 8-oxoG: T but not 8-oxoG : C pairs. Primer extension reactions in cell-free extracts of M. smegmatis suggested error-prone incorporation of nucleotides into the DNA. Based on these observations, we discuss the physiological role of MutY in specific mutation prevention in mycobacteria.

Differential Mechanisms of Binding of Anti-Sigma Factors Escherichia coli Rsd and Bacteriophage T4 AsiA to E. coli RNA Polymerase Lead to Diverse Physiological Consequences

Anti-sigma factors Escherichia coli Rsd and bacteriophage T4 AsiA bind to the essential housekeeping sigma factor, sigma(70), of E. coli. Though both factors are known to interact with the C-terminal region of sigma(70), the physiological consequences of these interactions are very different. This study was undertaken for the purpose of deciphering the mechanisms by which E. coli Rsd and bacteriophage T4 AsiA inhibit or modulate the activity of E. coli RNA polymerase, which leads to the inhibition of E. coli cell growth to different amounts. It was found that AsiA is the more potent inhibitor of in vivo transcription and thus causes higher inhibition of E. coli cell growth. Measurements of affinity constants by surface plasmon resonance experiments showed that Rsd and AsiA bind to or 70 with similar affinity. Data obtained from in vivo and in vitro binding experiments clearly demonstrated that the major difference between AsiA and Rsd is the ability of AsiA to form a stable ternary complex with RNA polymerase. The binding patterns of AsiA and Rsd with sigma(70) studied by using the yeast two-hybrid system revealed that region 4 of sigma(70) is involved in binding to both of these anti-sigma factors; however, Rsd interacts with other regions of sigma(70) as well. Taken together, these results suggest that the higher inhibition of E. coli growth by AsiA expression is probably due to the ability of the AsiA protein to trap the holoenzyme RNA polymerase rather than its higher binding affinity to sigma(70).

Effects of compressibility and heat release on entrainment processes in mixing layers

Characteristics of the process of entrainment in plane mixing layers, and the changes with compressibility and heat release, were studied using temporal DNS with simultaneous fluid packet tracking. Convective Mach numbers of the simulations are 0.15, 0.7 and 1.1. The Reynolds number is quite high (between 11 000 and 37 000 based on layer width and velocity difference), and is above the mixing transition. The study agrees with recent findings in round jets: first, engulfed fluid volume and its growth rate are both very small compared with the volume of the turbulent region and its growth rate, respectively. Secondly, most often, the process occurs close to the turbulent-nonturbulent boundaries. A new finding is that both compressibility and heat release retard the entrainment process so that it takes an O(1) time for vorticity or scalar levels to grow even after growth has been initiated. This delay is manifested as the fall in mixing layer growth rates as compressibility and heat release levels increase.

Electrical switching and in situ Raman scattering studies on the set-reset processes in Ge-Te-Si glass

Bulk Ge15Te83Si2 glass has been found to exhibit memory-type switching for 1 mA current with a threshold electric field of 7.3 kV/cm. The electrical set and reset processes have been achieved with triangular and rectangular pulses, respectively, of 1 mA amplitude. In situ Raman scattering studies indicate that the degree of disorder in Ge15Te83Si2 glass is reduced from off to set state. The local structure of the sample under reset condition is similar to that in the off state. The Raman results are consistent with the switching results which indicate that the Ge15Te83Si2 glass can be set and reset easily. (C) 2007 American Institute of Physics.

Dynamic simulation of activated sludge based wastewater treatment processes: Case studies with Titagarh Sewage Treatment Plant, India

STOAT has been extensively used for the dynamic simulation of an activated sludge based wastewater treatment plant in the Titagarh Sewage Treatment Plant, near Kolkata, India. Some alternative schemes were suggested. Different schemes were compared for the removal of Total Suspended Solids (TSS), b-COD, ammonia, nitrates etc. A combination of IAWQ#1 module with the Takacs module gave best results for the existing scenarios of the Titagarh Sewage Treatment Plant. The modified Bardenpho process was found most effective for reducing the mean b-COD level to as low as 31.4 mg/l, while the mean TSS level was as high as 100.98 mg/l as compared to the mean levels of TSS (92 62 mg/l) and b-COD (92.0 mg/l) in the existing plant. Scheme 2 gave a better scenario for the mean TSS level bringing it down to a mean value of 0.4 mg/l, but a higher mean value for the b-COD level at 54.89 mg/l. The Scheme Final could reduce the mean TSS level to 2.9 mg/l and the mean b-COD level to as low as 38.8 mg/l. The Final Scheme looks to be a technically viable scheme with respect to the overall effluent quality for the plant. (C) 2009 Elsevier B.V. All rights reserved.