461 research outputs found
Continuum Extrapolation of Moments of Nucleon Quark Distributions in Full QCD
Moments of light cone quark density, helicity, and transversity distributions are calculated in unquenched lattice QCD at and using Wilson fermions on lattices. These results are combined with earlier calculations at using SESAM configurations to study the continuum limit
Phenomenological Consequences of Singlet Neutrinos
In this paper, we study the phenomenology of right-handed neutrino
isosinglets. We consider the general situation where the neutrino masses are
not necessarily given by , where and are the Dirac and
Majorana mass terms respectively. The consequent mixing between the light and
heavy neutrinos is then not suppressed, and we treat it as an independent
parameter in the analysis. It turns out that conversion is an important
experiment in placing limits on the heavy mass scale () and the mixing.
Mixings among light neutrinos are constrained by neutrinoless double beta
decay, as well as by solar and atmospheric neutrino experiments. Detailed
one-loop calculations for lepton number violating vertices are provided.Comment: Revtex file,TRI-PP-94-1,VPI-IHEP-94-1, 23 pages, a compressed for 8
figures is appende
Moments of Nucleon Light Cone Quark Distributions Calculated in Full Lattice QCD
Moments of the quark density, helicity, and transversity distributions are
calculated in unquenched lattice QCD. Calculations of proton matrix elements of
operators corresponding to these moments through the operator product expansion
have been performed on lattices for Wilson fermions at using configurations from the SESAM collaboration and at
using configurations from SCRI. One-loop perturbative renormalization
corrections are included. At quark masses accessible in present calculations,
there is no statistically significant difference between quenched and full QCD
results, indicating that the contributions of quark-antiquark excitations from
the Dirac Sea are small. Close agreement between calculations with cooled
configurations containing essentially only instantons and the full gluon
configurations indicates that quark zero modes associated with instantons play
a dominant role. Naive linear extrapolation of the full QCD calculation to the
physical pion mass yields results inconsistent with experiment. Extrapolation
to the chiral limit including the physics of the pion cloud can resolve this
discrepancy and the requirements for a definitive chiral extrapolation are
described.Comment: 53 Pages Revtex, 26 Figures, 9 Tables. Added additional reference and
updated referenced data in Table I
Manejo de la defoliación y fertilización nitrogenada en pasto llorón, Eragrostis curvula, cv. Tanganyka : 1-rendimiento de materia seca, digestibilidad in vitro y rendimiento de materia seca digestible
p.7-14En una pradera de pasto llorón ubicada en Argerich se estudió el efecto de dos tratamientos de defoliación y tres niveles de fertilización nitrogenada durante tres ciclos consecutivos. El forraje se cortó con una frecuencia de 35 cm de altura o acumulado, hasta el 20 de febrero (primavera-verano), y sus rebrotes otoñales se cortaron en invierno (diferido). En primavera-verano el corte a 35 cm, produjo en promedio más materia seca que el acumulado y en el diferido a la inversa. Sus totales anuales fueron similares. La fertilización aumentó los rendimientos promedios parciales y totales (P menor a 0,05). La digestibiüdad primavera-estival fue mayor con cortes a 35 cm que en el acumulado y ambos tratamientos de defoliación respondieron al nitrógeno pero en sus diferidos el efecto fue de pequeña magnitud. Los rendimientos de materia seca digestible siguieron la misma tendencia que los de materia seca aunque, por influencia primavera-estival, en el total anual el corte a 35 cm superó al acumulado (P menor a 0,05). El rebrote primaveral sólo mostró un efecto residual parcial del fertilizante
Nuclear Skins and Halos in the Mean-Field Theory
Nuclei with large neutron-to-proton ratios have neutron skins, which manifest
themselves in an excess of neutrons at distances greater than the radius of the
proton distribution. In addition, some drip-line nuclei develop very extended
halo structures. The neutron halo is a threshold effect; it appears when the
valence neutrons occupy weakly bound orbits. In this study, nuclear skins and
halos are analyzed within the self-consistent Skyrme-Hartree-Fock-Bogoliubov
and relativistic Hartree-Bogoliubov theories for spherical shapes. It is
demonstrated that skins, halos, and surface thickness can be analyzed in a
model-independent way in terms of nucleonic density form factors. Such an
analysis allows for defining a quantitative measure of the halo size. The
systematic behavior of skins, halos, and surface thickness in even-even nuclei
is discussed.Comment: 22 RevTeX pages, 22 EPS figures included, submitted to Physical
Review
Target 2035 - an update on private sector contributions
Target 2035, an international federation of biomedical scientists from the public and private sectors, is leveraging ‘open’ principles to develop a pharmacological tool for every human protein. These tools are important reagents for scientists studying human health and disease and will facilitate the development of new medicines. It is therefore not surprising that pharmaceutical companies are joining Target 2035, contributing both knowledge and reagents to study novel proteins. Here, we present a brief progress update on Target 2035 and highlight some of industry's contributions
The Shadow Economy in International Comparison: Options for Economic Policy Derived from an OECD Panel Analysis
The Role of Phe82 and Phe351 in Auxin-Induced Substrate Perception by TIR1 Ubiquitin Ligase: A Novel Insight from Molecular Dynamics Simulations
It is well known that Auxin plays a key role in controlling many aspects of plant growth and development. Crystal structures of Transport inhibitor response 1 (TIR1), a true receptor of auxin, were very recently determined for TIR1 alone and in complexes with auxin and different synthetic analogues and an Auxin/Indole-3-Acetic Acid (Aux/IAA) substrate peptide. However, the dynamic conformational changes of the key residues of TIR1 that take place during the auxin and substrate perception by TIR1 and the detailed mechanism of these changes are still unclear. In the present study, various computational techniques were integrated to uncover the detailed molecular mechanism of the auxin and Aux/IAA perception process; these simulations included molecular dynamics (MD) simulations on complexes and the free enzyme, the molecular mechanics Poisson Boltzmann surface area (MM-PBSA) calculations, normal mode analysis, and hydrogen bond energy (HBE) calculations. The computational simulation results provided a reasonable explanation for the structure-activity relationships of auxin and its synthetic analogues in view of energy. In addition, a more detailed model for auxin and Aux/IAA perception was also proposed, indicating that Phe82 and Phe351 played a pivotal role in Aux/IAA perception. Upon auxin binding, Phe82 underwent conformational changes to accommodate the subsequent binding of Aux/IAA. As a result, auxin enhances the TIR1-Aux/IAA interactions by acting as a “molecular glue”. Besides, Phe351 acts as a “fastener” to further improve the substrate binding. The structural and mechanistic insights obtained from the present study will provide valuable clues for the future design of promising auxin analogues
Task-Specific Effects of tDCS-Induced Cortical Excitability Changes on Cognitive and Motor Sequence Set Shifting Performance
In this study, we tested the effects of transcranial Direct Current Stimulation (tDCS) on two set shifting tasks. Set shifting ability is defined as the capacity to switch between mental sets or actions and requires the activation of a distributed neural network. Thirty healthy subjects (fifteen per site) received anodal, cathodal and sham stimulation of the dorsolateral prefrontal cortex (DLPFC) or the primary motor cortex (M1). We measured set shifting in both cognitive and motor tasks. The results show that both anodal and cathodal single session tDCS can modulate cognitive and motor tasks. However, an interaction was found between task and type of stimulation as anodal tDCS of DLPFC and M1 was found to increase performance in the cognitive task, while cathodal tDCS of DLPFC and M1 had the opposite effect on the motor task. Additionally, tDCS effects seem to be most evident on the speed of changing sets, rather than on reducing the number of errors or increasing the efficacy of irrelevant set filtering
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