ALBERT

Description: The growing installation of industrial facilities for subsurface exploration worldwide requires continuous refinements in understanding both the mechanisms by which seismicity is induced by field operations and the related seismic hazard. Particularly in proximity of densely populated areas, induced low-to-moderate magnitude seismicity characterized by high-frequency content can be clearly felt by the surrounding inhabitants and, in some cases, may produce damage. In this respect we propose a technique for time-dependent probabilistic seismic-hazard analysis to be used in geothermal fields as a monitoring tool for the effects of on-going field operations. The technique integrates the observed features of the seismicity induced by fluid injection and extraction with a local ground-motion prediction equation. The result of the analysis is the time-evolving probability of exceedance of peak ground acceleration (PGA), which can be compared with selected critical values to manage field operations. To evaluate the reliability of the proposed technique, we applied it to data collected in The Geysers geothermal field in northern California between 1 September 2007 and 15 November 2010. We show that the period considered the seismic hazard at The Geysers was variable in time and space, which is a consequence of the field operations and the variation of both seismicity rate and b -value. We conclude that, for the exposure period taken into account (i.e., two months), as a conservative limit, PGA values corresponding to the lowest probability of exceedance (e.g., 30%) must not be exceeded to ensure safe field operations. We suggest testing the proposed technique at other geothermal areas or in regions where seismicity is induced, for example, by hydrocarbon exploitation or carbon dioxide storage.

Description: Questions Do composition and richness of woody plants differ between gaps and closed canopy in subtropical forests, and does this difference vary across life stages of tree species? Is tree species richness in gaps a function of regeneration density? Location Subtropical Shorea robusta Gaertn (Sal) forest, central Nepal. Methods We collected vegetation data from two old-growth S. robusta forest stands. We sampled 128 plots of 100 m 2 equally spread between the two habitats: gap and closed canopy. In each plot, we recorded the total number of woody species, number of individuals of seedlings and saplings of tree species and measured the DBH of all saplings. We compared species richness and composition of total woody species, seedlings and saplings between the two habitats. We used ordination to analyse species composition, and an individual-based species accumulation curves to illustrate the effect of density on species richness. Results The species composition of total woody species and seedlings was similar in both habitats, but species composition of saplings differed between habitats. Total woody and seedling richness were similar between habitats at one site, but were richer under closed canopy at the other site. Sapling richness was higher in gaps at both sites and was a function of stem density at one site, but not at the other site. Conclusions Gaps are not always areas of higher woody species richness and therefore may be less important than expected for the overall species richness of woody plants. Instead, they are potentially important for enhancing local tree richness by increasing sapling richness. Gap disturbance is the primary driver of structural heterogeneity in forests where topographic and edaphic gradients are negligible. We compare richness and composition of woody species between gaps and closed canopy patches in subtropical Shorea robusta forest. We did not find that gaps enhance overall woody species richness, but gaps maintain tree richness by supporting seedling to sapling transition. Higher sapling richness and occurrence of some gap-specific saplings suggest that gap provide important regeneration niches for some tree species.

Description: 〈p〉Foxp3 and its protein partners establish a regulatory T (T〈sub〉reg〈/sub〉) cell transcription profile and promote immunological tolerance. However, molecular features contributing to a T〈sub〉reg〈/sub〉-specific gene expression program are still incompletely understood. We find that the transcription factor Bcl11b is a prominent Foxp3 cofactor with multifaceted functions in T〈sub〉reg〈/sub〉 biology. Optimal genomic recruitment of Foxp3 and Bcl11b is critically interdependent. Genome-wide occupancy studies coupled with gene expression profiling reveal that Bcl11b, in association with Foxp3, is primarily responsible in establishing a T〈sub〉reg〈/sub〉-specific gene activation program. Furthermore, Bcl11b restricts misdirected recruitment of Foxp3 to sites, which would otherwise result in an altered T〈sub〉reg〈/sub〉 transcriptome profile. Consequently, T〈sub〉reg〈/sub〉-specific ablation of Bcl11b results in marked breakdown of immune tolerance, leading to aggressive systemic autoimmunity. Our study provides previously underappreciated mechanistic insights into molecular events contributing to basic aspects of T〈sub〉reg〈/sub〉 function. Furthermore, it establishes a therapeutic target with potential implications in autoimmunity and cancer.〈/p〉

Description: Nickel is a silvery-white metal mostly used to enhance the value, utility, and lifespan of industrial equipment and components by protecting them from corrosion. Nickel is commonly used in the chemical and food processing industries to prevent iron from contamination. Since the properties of nickel can be controlled and varied over broad ranges, nickel plating finds numerous applications in industries. In the present investigation, pulse current electro-deposition technique has been used to deposit nickel on a high strength low alloy (HSLA) steel substrate.Coating of nickel is confirmed by X-ray diffraction (XRD) and EDAX analysis. Optical microscopy and SEM is used to assess the coating characteristics. Electrochemical polarization study has been carried out to study the corrosion behaviour of nickel coating and the polarisation curves have revealed that current density used during pulse electro-deposition plays a vital role on characteristics of nickel coating.

Description: Energy & Fuels DOI: 10.1021/ef3009025

Description: A photovoltaic (PV) generator exhibits nonlinear voltage-current characteristics and its maximum power point varies with solar radiation. Analytical investigations of the new family of switching converters based on a parallel connection of N(=4) identical buck-boost converters employed in PV system are presented. The interleaving strategy ensures that all the converters operate at the same switching frequency. Mathematical models developed using the state-space average technique are presented in this paper. Various steady-state performance expressions are also derived. The present converter system has the advantages of reduced size of the converter, and ripple in the total inductor current. The effectiveness of the four-phase interleaved dc-dc converter combined with PV system is demonstrated through simulations carried out in MATLAB environment.

Description: Author(s): J. Cleymans, S. Kabana, I. Kraus, H. Oeschler, K. Redlich, and N. Sharma [Phys. Rev. C 84, 054916] Published Mon Nov 28, 2011

Description: The importance of understanding the molecular mechanisms of murine leukemia virus (MLV) integration into host chromatin is highlighted by the development of MLV-based vectors for human gene-therapy. We have recently identified BET proteins (Brd2, 3 and 4) as the main cellular binding partners of MLV integrase (IN) and demonstrated their significance for effective MLV integration at transcription start sites. Here we show that recombinant Brd4, a representative of the three BET proteins, establishes complementary high-affinity interactions with MLV IN and mononucleosomes (MNs). Brd4(1–720) but not its N- or C-terminal fragments effectively stimulate MLV IN strand transfer activities in vitro . Mass spectrometry- and NMR-based approaches have enabled us to map key interacting interfaces between the C-terminal domain of BRD4 and the C-terminal tail of MLV IN. Additionally, the N-terminal fragment of Brd4 binds to both DNA and acetylated histone peptides, allowing it to bind tightly to MNs. Comparative analyses of the distributions of various histone marks along chromatin revealed significant positive correlations between H3- and H4-acetylated histones, BET protein-binding sites and MLV-integration sites. Our findings reveal a bimodal mechanism for BET protein-mediated MLV integration into select chromatin locations.

Description: In this paper, we present time series photometry of 104 variable stars in the cluster region NGC 1893. The association of the present variable candidates to the cluster NGC 1893 has been determined by using ( U  – B )/( B  – V ) and ( J  – H )/( H  – K ) two colour diagrams, and V /( V  – I ) colour–magnitude diagram. 45 stars are found to be main-sequence variables and these could be B-type variable stars associated with the cluster. We classified these objects as β Cep, slowly pulsating B stars and new class variables as discussed by Mowlavi et al. These variable candidates show ~0.005 to ~0.02 mag brightness variations with periods of 〈1.0 d. 17 new class variables are located in the H  – R diagram between the slowly pulsating B stars and Scuti variables. Pulsation could be one of the causes for periodic brightness variations in these stars. The X-ray emission of present main-sequence variables associated with the cluster lies in the saturated region of X-ray luminosity versus period diagram and follows the general trend by Pizzolato et al.