3,702 research outputs found
Variables influencing the frictional behaviour of in vivo human skin
In the past decades, skin friction research has focused on determining which variables are important to affect the frictional behaviour of in vivo human skin. Until now, there is still limited knowledge on these variables.
This study has used a large dataset to identify the effect of variables on the human skin, subject characteristics and environmental conditions on skin friction. The data are obtained on 50 subjects (34 male, 16 female). Friction measurements represent the friction between in vivo human skin and an aluminium sample, assessed on three anatomical locations.
The coefficient of friction increased significantly (p<0.05) with increasing age, increasing ambient temperature and increasing relative air humidity. A significant inversely proportional relationship was found between friction and both the amount of hair present on the skin and the height of the subject. Other outcome variables in this study were the hydration of the skin and the skin temperatur
The pion form factor on the lattice at zero and finite temperature
We calculate the electromagnetic form factor of the pion in quenched lattice
QCD. The non-perturbatively improved Sheikoleslami-Wohlert lattice action is
used together with the consistently O(a) improved current. We calculate the
pion form factor for masses down to m_pi = 360 MeV, extract the charge radius,
and extrapolate toward the physical pion mass. In the second part, we discuss
results for the pion form factor and charge radius at 0.93 T_c and compare with
zero temperature results.Comment: Invited talk at the Lightcone 2004 conference, Amsterdam, 16-20
August, 200
Helicity Amplitudes for Single-Top Production
Single top quark production at hadron colliders allows a direct measurement
of the top quark charged current coupling. We present the complete tree-level
helicity amplitudes for four processes involving the production and
semileptonic decay of a single top quark: W-gluon fusion, flavor excitation,
s-channel production and W-associated production. For the first three processes
we study the quality of the narrow top width approximation. We also examine
momentum and angular distributions of some of the final state particles.Comment: 27 pages, 7 figures, final versio
Current driven switching of magnetic layers
The switching of magnetic layers is studied under the action of a spin
current in a ferromagnetic metal/non-magnetic metal/ferromagnetic metal spin
valve. We find that the main contribution to the switching comes from the
non-equilibrium exchange interaction between the ferromagnetic layers. This
interaction defines the magnetic configuration of the layers with minimum
energy and establishes the threshold for a critical switching current.
Depending on the direction of the critical current, the interaction changes
sign and a given magnetic configuration becomes unstable. To model the time
dependence of the switching process, we derive a set of coupled Landau-Lifshitz
equations for the ferromagnetic layers. Higher order terms in the
non-equilibrium exchange coupling allow the system to evolve to its
steady-state configuration.Comment: 8 pages, 2 figure. Submitted to Phys. Rev.
Enzymatic synthesis of the coenzyme a ester of o-succinylbenzoic acid, an intermediate in menaquinone (vitamin K2) biosynthesis
Linearizing nonlinear optics
In the framework of linear optics, light fields do not interact with each
other in a medium. Yet, when their field amplitude becomes comparable to the
electron binding energies of matter, the nonlinear motion of these electrons
emits new dipole radiation whose amplitude, frequency and phase differ from the
incoming fields. Such high fields are typically achieved with ultra-short,
femtosecond (1fs = 10-15 sec.) laser pulses containing very broad frequency
spectra. Here, the matter not only couples incoming and outgoing fields but
also causes different spectral components to interact and mix through a
convolution process. In this contribution, we describe how frequency domain
nonlinear optics overcomes the shortcomings arising from this convolution in
conventional time domain nonlinear optics1. We generate light fields with
previously inaccessible properties because the uncontrolled coupling of
amplitudes and phases is turned off. For example, arbitrary phase functions are
transferred linearly to the second harmonic frequency while maintaining the
exact shape of the input power spectrum squared.
This nonlinear control over output amplitudes and phases opens up new avenues
for applications based on manipulation of coherent light fields. One could
investigate c.f. the effect of tailored nonlinear perturbations on the
evolution of discrete eigenmodes in Anderson localization2. Our approach might
also open a new chapter for controlling electronic and vibrational couplings in
2D-spectroscopy3 by the geometrical optical arrangement
Decoupling frequencies, amplitudes and phases in nonlinear optics
In linear optics, light fields do not mutually interact in a medium. However, they do mix when their field strength becomes comparable to electron binding energies in the so-called nonlinear optical regime. Such high fields are typically achieved with ultra-short laser pulses containing very broad frequency spectra where their amplitudes and phases are mutually coupled in a convolution process. Here, we describe a regime of nonlinear interactions without mixing of different frequencies. We demonstrate both in theory and experiment how frequency domain nonlinear optics overcomes the shortcomings arising from the convolution in conventional time domain interactions. We generate light fields with previously inaccessible properties by avoiding these uncontrolled couplings. Consequently, arbitrary phase functions are transferred linearly to other frequencies while preserving the general shape of the input spectrum. As a powerful application, we introduce deep UV phase control at 207 nm by using a conventional NIR pulse shaper
Regional Economic growth and accessibility: The case of the Netherlands
Shift-share is a popular, relatively easy to apply, tool in spatial analysis. Upon its initial development and use in the 1970s the literature has shown that serious drawbacks of the shift-share technique should be noted (e.g., lack of theoretical basis, sensitivity to level of aggregation). But several solutions have been proposed, and besides, when a technique is simple and apparently useful, it will be both widely used and heavily criticized. The aim of this paper was to apply a shift- share analysis for the labour volume and value added. This was done for 40 so-called COROP-regions in the Netherlands over several subperiods of the most recent decades (1973-1993). It was shown that the development over time of the three shift-share effects for labour volume and value added were much the same. This was not only shown by means of a Geographic Information System but also statistically proved. Other relationships between the outcomes of the shift-share analysis and a few, more or less, economic variables were investigated as well. And lastly, an interesting aspect was the course of the regional growth of value added and employment over time. This development was illustrated by using a concentration-coefficient.
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