Mutations in Mtr4 Structural Domains Reveal Their Important Role in Regulating tRNA\u3csub\u3ei\u3c/sub\u3e \u3csup\u3eMet\u3c/sup\u3e Turnover in \u3cem\u3eSaccharomyces cerevisiae\u3c/em\u3e and Mtr4p Enzymatic Activities \u3cem\u3eIn Vitro\u3c/em\u3e

RNA processing and turnover play important roles in the maturation, metabolism and quality control of a large variety of RNAs thereby contributing to gene expression and cellular health. The TRAMP complex, composed of Air2p, Trf4p and Mtr4p, stimulates nuclear exosome-dependent RNA processing and degradation in Saccharomyces cerevisiae. The Mtr4 protein structure is composed of a helicase core and a novel so-called arch domain, which protrudes from the core. The helicase core contains highly conserved helicase domains RecA-1 and 2, and two structural domains of unclear functions, winged helix domain (WH) and ratchet domain. How the structural domains (arch, WH and ratchet domain) coordinate with the helicase domains and what roles they are playing in regulating Mtr4p helicase activity are unknown. We created a library of Mtr4p structural domain mutants for the first time and screened for those defective in the turnover of TRAMP and exosome substrate, hypomodified tRNAiMet. We found these domains regulate Mtr4p enzymatic activities differently through characterizing the arch domain mutants K700N and P731S, WH mutant K904N, and ratchet domain mutant R1030G. Arch domain mutants greatly reduced Mtr4p RNA binding, which surprisingly did not lead to significant defects on either in vivo tRNAiMet turnover, or in vitro unwinding activities. WH mutant K904N and Ratchet domain mutant R1030G showed decreased tRNAiMet turnover in vivo, as well as reduced RNA binding, ATPase and unwinding activities of Mtr4p in vitro. Particularly, K904 was found to be very important for steady protein levels in vivo. Overall, we conclude that arch domain plays a role in RNA binding but is largely dispensable for Mtr4p enzymatic activities, however the structural domains in the helicase core significantly contribute to Mtr4p ATPase and unwinding activities

Structural reliability prediction of a steel bridge element using dynamic object oriented Bayesian Network (DOOBN)

Different from conventional methods for structural reliability evaluation, such as, first/second-order reliability methods (FORM/SORM) or Monte Carlo simulation based on corresponding limit state functions, a novel approach based on dynamic objective oriented Bayesian network (DOOBN) for prediction of structural reliability of a steel bridge element has been proposed in this paper. The DOOBN approach can effectively model the deterioration processes of a steel bridge element and predict their structural reliability over time. This approach is also able to achieve Bayesian updating with observed information from measurements, monitoring and visual inspection. Moreover, the computational capacity embedded in the approach can be used to facilitate integrated management and maintenance optimization in a bridge system. A steel bridge girder is used to validate the proposed approach. The predicted results are compared with those evaluated by FORM method

Surface Average Temperature Measurement of Cu-W Contact Material Burning in CO2: Preliminary Study

The surface average temperature and the electrode temperature distribution are key parameters to predict the electrode erosion. Experimental research on the arc erosion has been carried out in a model circuit breaker, in which CO2 is filled in the chamber and Cu-W is used as the contact material. The surface average temperatures of plug contact exposed to electric arc with sinusoidal currents of 5kA were determined by a high-speed pyroscope. In order to establish a relationship between the average temperature of the contact surface and current squared, the data statistics and fitting curves in the current-rising and current-falling stages were given. It has been found that there are two different types of arc erosion processes by comparing the temperature-current squared curves. In other words, the structure of contact surface and the electrode material change significantly after repeated arc erosions

Arc Voltage as an Indicator of Nozzle Ablation Degradation in High-voltage CO2 Gas Circuit Breakers

Energy released by electric arc during short-circuit current interruption is mostly absorbed by the surrounding cold gas and partly transferred to the arcing contacts and nozzle. The radiation is the main mode of thermal energy transfer between the electric arc and nozzle surface. Experimental research on the nozzle ablation has been carried out at a model circuit breaker, in which CO2 is filled in the chamber and poly-tetrafluoro-ethylene (PTFE) is used as the nozzle material. It is found that the arc voltage can be as an indicator of nozzle ablation degradation by comparing the voltage at current peak and arc voltage extinction peak. Under 20kA and 35kA peak current interrupting conditions, the voltage at current peak decreases with the number of operations. There are two factors that affect the arc voltage at current peak. One is the size of the arc cross section, and the other is the content of PTFE entering the arc zone, which affects its conductivity

Experimental Study of Arc Erosion in Gas-blasting and Free-burning Conditions in High-voltage Circuit Breakers

Arc erosion behavior depends on varieties of factors, such as the shape and material of contacts, the gas type and the pressure filled in the chamber. In this contribution, experimental research on the gas-blasting and free-burning conditions was carried out in a model circuit breaker to investigate the gas blowing effect on the mass loss of arcing contacts. SF6 was filled in the chamber and copper-tungsten was used as the contact material. Three different peak current amplitudes (5/20/35kA) were selected, and the average mass loss of plug contact was measured after five consecutive arcing tests. The erosion physical process between arc root and contact material is extremely complex. The mass loss was estimated with four different indexes, which include integral of current squared, thermal stress, transferred electric charge and arc energy. It has been found that the arc energy can be used to represent the degree of arc erosion to relate the gas-blasting and free-burning conditions

Estrogen and progesterone induce persistent increases in p53-dependent apoptosis and suppress mammary tumors in BALB/c-Trp53+/- mice

INTRODUCTION Treatment with estrogen and progesterone (E+P) mimics the protective effect of parity on mammary tumors in rodents and depends upon the activity of p53. The following experiments tested whether exogenous E+P primes p53 to be more responsive to DNA damage and whether these pathways confer resistance to mammary tumors in a mouse model of Li-Fraumeni syndrome. METHODS Mice that differ in p53 status (Trp53+/+, Trp53+/-, Trp53-/-) were treated with E+P for 14 days and then were tested for p53-dependent responses to ionizing radiation. Responses were also examined in parous and age-matched virgins. The effects of hormonal exposures on tumor incidence were examined in BALB/c-Trp53+/- mammary tissues. RESULTS Nuclear accumulation of p53 and apoptotic responses were increased similarly in the mammary epithelium from E+P-treated and parous mice compared with placebo and age-matched virgins. This effect was sustained for at least 7 weeks after E+P treatment and did not depend on the continued presence of ovarian hormones. Hormone stimulation also enhanced apoptotic responses to ionizing radiation in BALB/c-Trp53+/- mice but these responses were intermediate compared with Trp53+/+ and Trp-/- tissues, indicating haploinsufficiency. The appearance of spontaneous mammary tumors was delayed by parity in BALB/c-Trp53+/- mice. The majority of tumors lacked estrogen receptor (ER), but ER+ tumors were observed in both nulliparous and parous mice. However, apoptotic responses to ionizing radiation and tumor incidence did not differ among outgrowths of epithelial transplants from E+P-treated donors and nulliparous donors. CONCLUSION Therefore, E+P and parity confer a sustained increase in p53-mediated apoptosis within the mammary epithelium and suppress mammary tumorigenesis, but this effect was not retained in epithelial outgrowths.This work was supported by grants from the US Army Medical Research and Materiel Command (W81XWH0410385 to KAD and DAMD17-01-1-0315 to ACB) and the National Institutes of Health (RO1-CA095164 to DJJ)

Gonc̆arov polynomials and parking functions

AbstractLet u be a sequence of non-decreasing positive integers. A u-parking function of length n is a sequence (x1,x2,…,xn) whose order statistics (the sequence (x(1),x(2),…,x(n)) obtained by rearranging the original sequence in non-decreasing order) satisfy x(i)⩽ui. The Gonc̆arov polynomials gn(x;a0,a1,…,an−1) are polynomials defined by the biorthogonality relation:ε(ai)Dign(x;a0,a1,…,an−1)=n!δin,where ε(a) is evaluation at a and D is the differentiation operator. In this paper we show that Gonc̆arov polynomials form a natural basis of polynomials for working with u-parking functions. For example, the number of u-parking functions of length n is (−1)ngn(0;u1,u2,…,un). Various properties of Gonc̆arov polynomials are discussed. In particular, Gonc̆arov polynomials satisfy a linear recursion obtained by expanding xn as a linear combination of Gonc̆arov polynomials, which leads to a decomposition of an arbitrary sequence of positive integers into two subsequences: a “maximum” u-parking function and a subsequence consisting of terms of higher values. Many counting results for parking functions can be derived from this decomposition. We give, as examples, formulas for sum enumerators, and a linear recursion and Appell relation for factorial moments of sums of u-parking functions

The Impact of Corporate Social Responsibility on Growth of Companies

There is an upsurge of crave for ethical practices and corporate social responsibility in both policy and actions of business organizations in recent times by society and social administrators globally. This is indicative of how crucial the subject is to the very existence of mankind and the universe as a whole and calls for a further assessment of the correlation between the concept and corporate bodies. Our write-up discusses the position of corporate social responsibility in relation to core business functions of companies and whether it has an influence on the growth of organizations. Social commentators and society unambiguously agree that the main causative factors for social problems like global warming, epidemics, wild fires, flooding and environmental degradation are the repercussions of organizational activities and therefore expect that organizations should be at the fore-front in the effort to combat these multifaceted issues. Companies have however maintained the view that corporate social responsibility is not relevant to their main mandate and only see it as a favor done to society. Our study debunks this misconception and demonstrate that the place of corporate social responsibility and ethical practices in business organizations is not just a philanthropic phenomenon but has relevance to core business functions and impacts on performance and growth. Our study also discovered that going beyond ethics in the operations of a company to engage in direct community development activities increases the effect of social responsibility on the fortunes of the company. Keywords: Corporate Social Responsibility; Growth; Corporate Responsiveness; Corporate Ethics; Philanthropic Phenomeno