The E12-14-012 experiment, performed in Jefferson Lab Hall A, has collected exclusive electron-scattering data (e,e'p) in parallel kinematics using natural argon and natural titanium targets. In this ...study we report the first results of the analysis of the data set corresponding to beam energy 2222 GeV, electron scattering angle 21.5° , and proton emission angle –50° . The differential cross sections, measured with ≈4% uncertainty, have been studied as a function of missing energy and missing momentum, and compared to the results of Monte Carlo simulations, obtained from a model based on the distorted-wave impulse approximation.
We present a microelectromechanical system (MEMS) based PZT/PZT thick film bimorph vibration energy harvester with an integrated silicon proof mass. Most piezoelectric energy harvesting devices use a ...cantilever beam of a non piezoelectric material as support beneath or in-between the piezoelectric materials; it provides mechanical support but it also reduces the power output. In our device we replace the support material with another layer of the piezoelectric material. With the absence of an inactive mechanical support all stresses induced by vibrations will be harvested by the active piezoelectric elements. We show experimental results from two types PZT/PZT harvesting devices, one where the Pb(ZrxTi1−x)O3 (PZT) thick films are high pressure treated during the fabrication and the other where the treatment is omitted. We find that with the high pressure treatment prior to PZT sintering, the films become denser and the harvester efficiency increases significantly.
Accurate computation of the performance of a horizontal-axis wind turbine (HAWT) using Blade Element Momentum (BEM) based codes requires good quality aerodynamic characteristics of airfoils. This ...paper shows a numerical investigation of transitional flow over the DU 91-W2-250 airfoil with chord-based Reynolds number ranging from 3 × 106 to 6 × 106. The primary goal of the present paper is to validate the unsteady Reynolds averaged Navier-Stokes (URANS) approach together with the four-equation transition SST turbulence model with experimental data from a wind tunnel. The main computational fluid dynamics (CFD) code used in this work was ANSYS Fluent. For comparison, two more CFD codes with the Transition SST model were used: FLOWer and STAR-CCM +. The obtained airfoil characteristics were also compared with the results of fully turbulent models published in other works. The XFOIL approach was also used in this work for comparison. The aerodynamic force coefficients obtained with the Transition SST model implemented in different CFD codes do not differ significantly from each other despite the different mesh distributions used. The drag coefficients obtained with fully turbulent models are too high. With the lowest Reynolds numbers analyzed in this work, the error in estimating the location of the transition was significant. This error decreases as the Reynolds number increases. The applicability of the uncalibrated transition SST approach for a two-dimensional thick airfoil is up to the critical angle of attack.
An analytical expression relating mass and position of a particle attached on a cantilever to the resulting change in cantilever resonant frequency is derived. Theoretically, the position and mass of ...the attached particle can be deduced by combining measured resonant frequencies of several bending modes. This finding is verified experimentally using a microscale cantilever with and without an attached gold bead. The resonant frequencies of several bending modes are measured as a function of the bead position. The bead mass and position calculated from the measured resonant frequencies are in good agreement with the expected mass and the position measured.
The proton is one of the main building blocks of all visible matter in the Universe
. Among its intrinsic properties are its electric charge, mass and spin
. These properties emerge from the complex ...dynamics of its fundamental constituents-quarks and gluons-described by the theory of quantum chromodynamics
. The electric charge and spin of protons, which are shared among the quarks, have been investigated previously using electron scattering
. An example is the highly precise measurement of the electric charge radius of the proton
. By contrast, little is known about the inner mass density of the proton, which is dominated by the energy carried by gluons. Gluons are hard to access using electron scattering because they do not carry an electromagnetic charge. Here we investigated the gravitational density of gluons using a small colour dipole, through the threshold photoproduction of the J/ψ particle. We determined the gluonic gravitational form factors of the proton
from our measurement. We used a variety of models
and determined, in all cases, a mass radius that is notably smaller than the electric charge radius. In some, but not all cases, depending on the model, the determined radius agrees well with first-principle predictions from lattice quantum chromodynamics
. This work paves the way for a deeper understanding of the salient role of gluons in providing gravitational mass to visible matter.
An understanding of how mammalian stem cells produce specific neuronal subtypes remains elusive. Here we show that human embryonic stem cells generated early neuroectodermal cells, which organized ...into rosettes and expressed Pax6 but not Sox1, and then late neuroectodermal cells, which formed neural tube-like structures and expressed both Pax6 and Sox1. Only the early, but not the late, neuroectodermal cells were efficiently posteriorized by retinoic acid and, in the presence of sonic hedgehog, differentiated into spinal motoneurons. The in vitro-generated motoneurons expressed HB9, HoxC8, choline acetyltransferase and vesicular acetylcholine transporter, induced clustering of acetylcholine receptors in myotubes, and were electrophysiologically active. These findings indicate that retinoic acid action is required during neuroectoderm induction for motoneuron specification and suggest that stem cells have restricted capacity to generate region-specific projection neurons even at an early developmental stage.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The E12-14-012 experiment performed at Jefferson Lab Hall A has collected inclusive electron-scattering data for different targets at the kinematics corresponding to beam energy 2.222 GeV and ...scattering angle 15.54 deg. Here we present a comprehensive analysis of the collected data and compare the double-differential cross sections for inclusive scattering of electrons, extracted using solid targets (aluminum, carbon, and titanium) and a closed argon-gas cell. The data extend over broad range of energy transfer, where quasielastic interaction, Delta-resonance excitation, and inelastic scattering yield contributions to the cross section. The double-differential cross sections are reported with high precision (~3%) for all targets over the covered kinematic range.
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