1,101 research outputs found
Impact of crop management systems on Fusarium populations in spring wheat and barley on the Canadian prairies
Non-Peer Reviewe
Long-term productivity and economic performance of spring wheat production systems in southwestern Saskatchewan
Non-Peer Reviewe
Electronic structure and band parameters for ZnX (X = O, S, Se, Te)
First-principles density-functional calculations have been performed for zinc
monochalcogenides with zinc-blende- and wurtzite-type structures. It is shown
that the local-density approximation underestimates the band gap, misplaces the
energy levels of the Zn-3d states, and overestimates the crystal-field
splitting energy. Without spinorbit coupling, the order of the states at the
top of VB is found to be normal for all the ZnX phases considered. Upon
inclusion of the spinorbit coupling in calculations, ZnO in zinc-blende- and
wurtzite-type phases become anomalous. It is shown that the Zn-3d electrons are
responsible for the anomalous order. The effective masses of electrons and
holes have been calculated and found that holes are much anisotropic and
heavier than the electrons in agreement with experimental findings. The typical
errors in calculated band gaps and related parameters originate from strong
Coulomb correlations, which are found to be highly significant in ZnO. The
LDA+U approach is found to correct the strong correlation of the Zn-3d
electrons, and thus improves the agreement with the experimentally established
location of the Zn-3d levels. Consequently, it increases significantly the
parameters underestimated in the pure LDA calculations.Comment: 7 pages, 3 figures, 2 tables, ICAM-ICMAT conference, 200
Linear Contraction Behavior of Low-Carbon, Low-Alloy Steels During and After Solidification Using Real-Time Measurements
A technique for measuring the linear contraction during and after solidification of low-alloy steel was developed and used for examination of two commercial low-carbon and low-alloy steel grades. The effects of several experimental parameters on the contraction were studied. The solidification contraction behavior was described using the concept of rigidity in a solidifying alloy, evolution of the solid fraction, and the microstructure development during solidification. A correlation between the linear contraction properties in the solidification range and the hot crack susceptibility was proposed and used for the estimation of hot cracking susceptibility for two studied alloys and verified with the real casting practice. The technique allows estimation of the contraction coefficient of commercial steels in a wide range of temperatures and could be helpful for computer simulation and process optimization during continuous casting. © 2013 The Minerals, Metals & Materials Society and ASM International
Modeling on fluid flow and inclusion motion in centrifugal continuous casting strands
During the centrifugal continuous casting process, unreasonable casting parameters can cause violent level fluctuation, serious gas entrainment, and formation of frozen shell pieces at the meniscus. Thus, in the current study, a three-dimensional multiphase turbulent model was established to study the transport phenomena during centrifugal continuous casting process. The effects of nozzle position, casting and rotational speed on the flow pattern, centrifugal force acting on the molten steel, level fluctuation, gas entrainment, shear stress on mold wall, and motion of inclusions during centrifugal continuous casting process were investigated. Volume of Fluid model was used to simulate the molten steel-air two-phase. The level fluctuation and the gas entrainment during casting were calculated by user-developed subroutines. The trajectory of inclusions in the rotating system was calculated using the Lagrangian approach. The results show that during centrifugal continuous casting, a large amount of gas was entrained into the molten steel, and broken into bubbles of various sizes. The greater the distance to the mold wall, the smaller the centrifugal force. Rotation speed had the most important influence on the centrifugal force distribution at the side region. Angular moving angle of the nozzle with 8° and keeping the rotation speed with 60 revolutions per minute can somehow stabilize the level fluctuation. The increase of angular angle of nozzle from 8 to 18 deg and rotation speed from 40 to 80 revolutions per minute favored to decrease the total volume of entrained bubbles, while the increase of distance of nozzle moving left and casting speed had reverse effects. The trajectories of inclusions in the mold were irregular, and then rotated along the strand length. After penetrating a certain distance, the inclusions gradually moved to the center of billet and gathered there. More work, such as the heat transfer, the solidification, and the inclusions entrapment during centrifugal continuous casting, will be performed
Combining web-based attentional bias modification and approach bias modification as a self-help smoking intervention for adult smokers seeking online help: Double-blind randomized controlled trial
Background: Automatically activated cognitive motivational processes such as the tendency to attend to or approach smoking-related stimuli (ie, attentional and approach bias) have been related to smoking behaviors. Therefore, these cognitive biases are thought to play a role in maintaining smoking behaviors. Cognitive biases can be modified with cognitive bias modification (CBM), which holds promise as an easy-access and low-cost online intervention. However, little is known about the effectiveness of online interventions combining two varieties of CBM. Targeting multiple cognitive biases may improve treatment outcomes because these biases have been shown to be relatively independent. Objective: This study aimed to test the individual and combined effects of two web-based CBM varieties-attentional bias modification (AtBM) and approach bias modification (ApBM)-in a double-blind randomized controlled trial (RCT) with a 2 (AtBM: Active versus sham) Ă 2 (ApBM: Active versus sham) factorial design. Methods: A total of 504 adult smokers seeking online help to quit smoking were randomly assigned to 1 of 4 experimental conditions to receive 11 fully automated CBM training sessions. To increase participants' intrinsic motivation to change their smoking behaviors, all participants first received brief, automated, tailored feedback. The primary outcome was point prevalence abstinence during the study period. Secondary outcomes included daily cigarette use and attentional and approach bias. All outcomes were repeatedly self-assessed online from baseline to the 3-month follow-up. For the examination of training effects on outcome changes, an intention-to-treat analysis with a multilevel modeling (MLM) approach was adopted. Results: Only 10.7% (54/504) of the participants completed all 11 training sessions, and 8.3% (42/504) of the participants reached the 3-month follow-up assessment. MLM showed that over time, neither AtBM or ApBM nor a combination of both differed from their respective sham training in point prevalence abstinence rates (P=.17, P=.56, and P=.14, respectively), and in changes in daily cigarette use (P=.26, P=.08, and P=.13, respectively), attentional bias (P=.07, P=.81, and P=.15, respectively), and approach bias (P=.57, P=.22, and P=.40, respectively), while daily cigarette use decreased over time across conditions for all participants (P<.001). Conclusions: This RCT pro
Pion Content of the Nucleon as seen in the NA51 Drell-Yan experiment
In a recent CERN Drell-Yan experiment the NA51 group found a strong asymmetry
of and densities in the proton at . We interpret
this result as a decisive confirmation of the pion-induced sea in the nucleon.Comment: 10 pages + 3 figures, Preprint KFA-IKP(TH)-1994-14 .tex file. After
\enddocument a uu-encodeded Postscript file comprising the figures is
appende
Local densities, distribution functions, and wave function correlations for spatially resolved shot noise at nanocontacts
We consider a current-carrying, phase-coherent multi-probe conductor to which
a small tunneling contact is attached. We treat the conductor and the tunneling
contact as a phase-coherent entity and use a Green's function formulation of
the scattering approach. We show that the average current and the current
fluctuations at the tunneling contact are determined by an effective local
non-equilibrium distribution function. This function characterizes the
distribution of charge-carriers (or quasi-particles) inside the conductor. It
is an exact quantum-mechanical expression and contains the phase-coherence of
the particles via local partial densities of states, called injectivities. The
distribution function is analyzed for different systems in the zero-temperature
limit as well as at finite temperature. Furthermore, we investigate in detail
the correlations of the currents measured at two different contacts of a
four-probe sample, where two of the probes are only weakly coupled contacts. In
particular, we show that the correlations of the currents are at
zero-temperature given by spatially non-diagonal injectivities and
emissivities. These non-diagonal densities are sensitive to correlations of
wave functions and the phase of the wave functions. We consider ballistic
conductors and metallic diffusive conductors. We also analyze the Aharonov-Bohm
oscillations in the shot noise correlations of a conductor which in the absence
of the nano-contacts exhibits no flux-sensitivity in the conductance.Comment: 17 pages, 8 figure
A Dendritic CellâSpecific Intercellular Adhesion Molecule 3âGrabbing Nonintegrin (Dc-Sign)âRelated Protein Is Highly Expressed on Human Liver Sinusoidal Endothelial Cells and Promotes HIV-1 Infection
The discovery of dendritic cell (DC)-specific intercellular adhesion molecule (ICAM)-3âgrabbing nonintegrin (DC-SIGN) as a DC-specific ICAM-3 binding receptor that enhances HIV-1 infection of T cells in trans has indicated a potentially important role for adhesion molecules in AIDS pathogenesis. A related molecule called DC-SIGNR exhibits 77% amino acid sequence identity with DC-SIGN. The DC-SIGN and DC-SIGNR genes map within a 30-kb region on chromosome 19p13.2-3. Their strong homology and close physical location indicate a recent duplication of the original gene. Messenger RNA and protein expression patterns demonstrate that the DC-SIGNârelated molecule is highly expressed on liver sinusoidal cells and in the lymph node but not on DCs, in contrast to DC-SIGN. Therefore, we suggest that a more appropriate name for the DC-SIGNârelated molecule is L-SIGN, liver/lymph nodeâspecific ICAM-3âgrabbing nonintegrin. We show that in the liver, L-SIGN is expressed by sinusoidal endothelial cells. Functional studies indicate that L-SIGN behaves similarly to DC-SIGN in that it has a high affinity for ICAM-3, captures HIV-1 through gp120 binding, and enhances HIV-1 infection of T cells in trans. We propose that L-SIGN may play an important role in the interaction between liver sinusoidal endothelium and trafficking lymphocytes, as well as function in the pathogenesis of HIV-1
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