1,676 research outputs found
The Adsorption of Certain Vapors by Charcoal at Various Temperatures up to and above Their Critical Temperatures
It is perhaps safe to state that no one property of a solid substance has been more persistently studied through so long a period as has been the property of solid porous bodies to adsorb gases and vapors. The phenomenon of the adsorption of gases and vapors by charcoal was originally discovered independently by Scheele1 and by Fontana1 in 1777. In the century following much was contributed which deals with the general qualitative side of adsorption. It was not until the beginning of the present century and more particularly with the advent of poison gas warfare and the consequent demand for gas mask adsorbents that an intensive study of charcoal and its properties was undertaken. Since then many investigations have been made and a number of theories have been put forth in the attempt to explain the mechanism of adsorption and to deduce laws governing it
Parity Violation in Neutron Resonances in 107,109Ag
Parity nonconservation (PNC) was studied in p-wave resonances in Ag by measuring the helicity dependence of the neutron total cross section. Transmission measurements on natural Ag were performed in the energy range 32 to 422 eV with the time-of-flight method at the Manuel Lujan Neutron Scattering Center at Los Alamos National Laboratory. A total of 15 p-wave neutron resonances were studied in 107Ag and ninep-wave resonances in 109Ag. Statistically significant asymmetries were observed for eight resonances in 107Ag and for four resonances in109Ag. An analysis treating the PNC matrix elements as random variables yields a weak spreading width of Γw=(2.67-1.21+2.65)×10-7 eV for107Ag and Γw=(1.30-0.74+2.49)×10-7 eV for 109Ag
Parity Violation in Neutron Resonances in 115In
Parity nonconservation (PNC) was studied in p-wave resonances in indium by measuring the helicity dependence of the neutron total cross section in the neutron energy range 6.0–316 eV with the time-of-flight method at LANSCE. A total of 36 p-wave neutron resonances were studied in 115In, and statistically significant asymmetries were observed for nine cases. An analysis treating the PNC matrix elements as random variables yields a weak matrix element of M=(0.67-0.12+0.16) meV and a weak spreading width of Γw=(1.30-0.43+0.76)×10-7 eV
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[Arctic] Greenland ice sheet [in “State of the Climate in 2012”]
Melting at the surface of the Greenland Ice Sheet set new records for extent and melt index (i.e., the number of days on which melting occurred multiplied by the area where melting was detected) for the period 1979–2012, according to passive microwave observations (e.g., Tedesco 2007, 2009; Mote and Anderson 1995). Melt extent reached ~97% of the ice sheet surface during a rare, ice-sheet-wide event on 11–12 July (Fig. 5.13a; Nghiem et al. 2012). This was almost four times greater than the average melt extent for 1981–2010. The 2012 standardized melting index (SMI, defined as the melting index minus its average and divided by its standard deviation) was +2.4, almost twice the previous record of about +1.3 set in 2010
Calculation of a Deuterium Double Shock Hugoniot from Ab initio Simulations
We calculate the equation of state of dense deuterium with two ab initio
simulations techniques, path integral Monte Carlo and density functional theory
molecular dynamics, in the density range of 0.67 < rho < 1.60 g/cc. We derive
the double shock Hugoniot and compare with the recent laser-driven double shock
wave experiments by Mostovych et al. [1]. We find excellent agreement between
the two types of microscopic simulations but a significant discrepancy with the
laser-driven shock measurements.Comment: accept for publication in Phys. Rev. Lett., Nov. 2001, 4 pages, 4
figure
A review of tennis racket performance parameters
The application of advanced engineering to tennis racket design has influenced the nature of the sport. As a result, the International Tennis Federation has established rules to limit performance, with the aim of protecting the nature of the game. This paper illustrates how changes to the racket affect the player-racket system. The review integrates engineering and biomechanical issues related to tennis racket performance, covering the biomechanical characteristics of tennis strokes, tennis racket performance, the effect of racket parameters on ball rebound and biomechanical interactions. Racket properties influence the rebound of the ball. Ball rebound speed increases with frame stiffness and as string tension decreases. Reducing inter-string contacting forces increases rebound topspin. Historical trends and predictive modelling indicate swingweights of around 0.030–0.035 kg/m2 are best for high ball speed and accuracy. To fully understand the effect of their design changes, engineers should use impact conditions in their experiments, or models, which reflect those of actual tennis strokes. Sports engineers, therefore, benefit from working closely with biomechanists to ensure realistic impact conditions
Differential cross sections for pion charge exchange on the proton at 27.5 MeV
We have measured pion single charge exchange differential cross sections on
the proton at 27.5 MeV incident kinetic energy in the center of
momentum angular range between and . The extracted cross
sections are compared with predictions of the standard pion-nucleon partial
wave analysis and found to be in excellent agreement.Comment: ReVTeX v3.0 with aps.sty, 23 pages in e-print format, 7 PostScript
Figures and 4 Tables, also available via anonymous ftp at
ftp://helena.phys.virginia.edu/pub/preprints/scx.p
The Equation of State and the Hugoniot of Laser Shock-Compressed Deuterium
The equation of state and the shock Hugoniot of deuterium are calculated
using a first-principles approach, for the conditions of the recent shock
experiments. We use density functional theory within a classical mapping of the
quantum fluids [ Phys. Rev. Letters, {\bf 84}, 959 (2000) ]. The calculated
Hugoniot is close to the Path-Integral Monte Carlo (PIMC) result. We also
consider the {\it quasi-equilibrium} two-temperature case where the Deuterons
are hotter than the electrons; the resulting quasi-equilibrium Hugoniot mimics
the laser-shock data. The increased compressibility arises from hot
pairs occuring close to the zero of the electron chemical potential.Comment: Four pages; One Revtex manuscript, two postscipt figures; submitted
to PR
The Negative Feedback-Loop between the Oncomir Mir-24-1 and Menin Modulates the Men1 Tumorigenesis by Mimicking the “Knudson’s Second Hit”
Multiple endocrine neoplasia type 1 (MEN1) syndrome is a rare hereditary cancer disorder characterized by tumors of the parathyroids, of the neuroendocrine cells, of the gastro-entero-pancreatic tract, of the anterior pituitary, and by non-endocrine neoplasms and lesions. MEN1 gene, a tumor suppressor gene, encodes menin protein. Loss of heterozygosity at 11q13 is typical of MEN1 tumors, in agreement with the Knudson’s two-hit hypothesis. In silico analysis with Target Scan, Miranda and Pictar-Vert softwares for the prediction of miRNA targets indicated miR-24-1 as capable to bind to the 3′UTR of MEN1 mRNA. We investigated this possibility by analysis of miR-24-1 expression profiles in parathyroid adenomatous tissues from MEN1 gene mutation carriers, in their sporadic non-MEN1 counterparts, and in normal parathyroid tissue. Interestingly, the MEN1 tumorigenesis seems to be under the control of a “negative feedback loop” between miR-24-1 and menin protein, that mimics the second hit of Knudson’s hypothesis and that could buffer the effect of the stochastic factors that contribute to the onset and progression of this disease. Our data show an alternative way to MEN1 tumorigenesis and, probably, to the “two-hit dogma”. The functional significance of this regulatory mechanism in MEN1 tumorigenesis is also the basis for opening future developments of RNA antagomir(s)-based strategies in the in vivo control of tumorigenesis in MEN1 carriers
Trim17, novel E3 ubiquitin-ligase, initiates neuronal apoptosis
Accumulating data indicate that the ubiquitin-proteasome system controls apoptosis by regulating the level and the function of key regulatory proteins. In this study, we identified Trim17, a member of the TRIM/RBCC protein family, as one of the critical E3 ubiquitin ligases involved in the control of neuronal apoptosis upstream of mitochondria. We show that expression of Trim17 is increased both at the mRNA and protein level in several in vitro models of transcription-dependent neuronal apoptosis. Expression of Trim17 is controlled by the PI3K/Akt/GSK3 pathway in cerebellar granule neurons (CGN). Moreover, the Trim17 protein is expressed in vivo, in apoptotic neurons that naturally die during post-natal cerebellar development. Overexpression of active Trim17 in primary CGN was sufficient to induce the intrinsic pathway of apoptosis in survival conditions. This pro-apoptotic effect was abolished in Bax(-/-) neurons and depended on the E3 activity of Trim17 conferred by its RING domain. Furthermore, knock-down of endogenous Trim17 and overexpression of dominant-negative mutants of Trim17 blocked trophic factor withdrawal-induced apoptosis both in CGN and in sympathetic neurons. Collectively, our data are the first to assign a cellular function to Trim17 by showing that its E3 activity is both necessary and sufficient for the initiation of neuronal apoptosis. Cell Death and Differentiation (2010) 17, 1928-1941; doi: 10.1038/cdd.2010.73; published online 18 June 201
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