50,518 research outputs found
Second Order Gauge Invariant Perturbation Theory -- Perturbative curvatures in the two-parameter case --
Based on the gauge invariant variables proposed in our previous paper [K.
Nakamura, Prog. Theor. Phys. vol.110 (2003), 723.], some formulae of the
perturbative curvatures of each order are derived. We follow the general
framework of the second order gauge invariant perturbation theory on arbitrary
background spacetime to derive these formulae. These perturbative curvatures do
have the same form as the definitions of gauge invariant variables for
arbitrary perturbative fields which are previously proposed. As a result, we
explicitly see that any perturbative Einstein equations are given in terms of
gauge invarinat form. We briefly discuss physical situations to which this
framework should be applied.Comment: 31 pages, 1 figure, PTPTEX (ptptex.cls ver 0.9);Some typos in the
published version are correcte
Semileptonic Lambda_b decay to excited Lambda_c baryons at order Lambda_{QCD}/m_Q
Exclusive semileptonic Lambda_b decays to excited charmed Lambda_c baryons
are investigated at order Lambda_{QCD}/m_Q in the heavy quark effective theory.
The differential decay rates are analyzed for the J^\pi=1/2^- Lambda_c(2593)
and the J^\pi=3/2^- \Lambda_c(2625). They receive 1/m_{c,b} corrections at zero
recoil that are determined by mass splittings and the leading order Isgur-Wise
function. With some assumptions, we find that the branching fraction for
Lambda_b decays to these states is 2.5-3.3%. The decay rate to the helicity \pm
3/2 states, which vanishes for m_Q \to \infty, remains small at order
Lambda_{QCD}/m_Q since 1/m_c corrections do not contribute. Matrix elements of
weak currents between a Lambda_b and other excited Lambda_c states are analyzed
at zero-recoil to order Lambda_{QCD}/m_Q. Applications to baryonic heavy quark
sum-rules are explored.Comment: 27 pages, 1 fig., minor changes, version to appear in Phys.Rev.
The numerical analysis of the rotational theory for the formation of lunar globules
The morphology of lunar globules is studied through the application of a numerical analysis of their rotation in space during cooling. It is assumed that molten rock is shot from the surface of the moon, solidifies in space above the moon and then falls back to the surface. The rotational theory studied makes the following assumptions: the volume of the molten rock does not change during cooling; the angular momentum is conserved; there are no internal motions because of the high viscosity of the molten rock, i.e., in equilibrium the globule is rotating as a rigid body; finally, the kinetic reaction of the globule to the forces is fast relative to the rate of cooling, i.e., the globule reaches equilibrium at constant energy. These assumptions are subjected to numerical analysis yielding good agreement between the actual globule shapes and the numerical results, but leaving some doubt as to the validity of the rotational theory due to the failure to establish the existence of true local minima and an incomplete understanding of the thermokentics
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Using Twitter to Support Students' Design Thinking
The goal of the short-term study abroad course
“International Perspectives on Biomedical Engineering
Design” is to enable students to consider sociotechnical
factors in designing clinically translatable solutions. In
addition, comparison of healthcare systems in Europe and
the United States enables students to see the impact of
culture on healthcare because people in these locations
have similar medical resources. Students seek to define an
actionable problem statement that summarizes the needs
and insights identified through interviews with healthcare
professionals. Methods recommended for formulating
actionable problem statements include creating a Madlib or
want ad. However, such approaches did not resonate with
our student group. In this presentation, we describe our
experiences using Twitter as a method for students to
succinctly write actionable problem statements that spur
creative problem solving.Cockrell School of Engineerin
Comparative Response of Two Hydrilla Strains to Fluridone
Experiments were conducted in a controlled-environmental
growth chamber to evaluate the response of two strains of
the invasive submersed plant
Hydrilla verticillata
(L.f.) Royle to fluridone (1-methyl-3-phenyl-5-[3-trifluoromethyl)phenyl]-
4(1H)-pyridinone). (PDF has 6 pages.
The other margin : do minimum wages cause working hours adjustments for low-wage workers?
This paper estimates the impact of the introduction of the UK minimum wage on the working hours of low-wage employees using difference-in-differences estimators. The estimates using the employer-based New Earnings Surveys indicate that the introduction of the minimum wage reduced the basic hours of low-wage workers by between 1 and 2 hours per week. The effects on total paid hours are similar (indicating negligible effects on paid overtime) and lagged effects dominate the smaller and less significant initial effects within this. Estimates using the employee-based Labour Force Surveys are typically less significant.minimum wages ; working hours ; labour demand ; difference-in-differences estimator
Construction and Calibration of a Streaked Optical Spectrometer for Shock Temperature
Here we describe the implementation and calibration of a streaked visible
spectrometer (SVS) for optical pyrometry and emission/absorption spectroscopy
on light gas gun platforms in the UC Davis Shock Compression Laboratory. The
diagnostic consists of an optical streak camera coupled to a spectrometer to
provide temporally and spectrally-resolved records of visible emission from
dynamically-compressed materials. Fiber optic coupling to the sample enables a
small diagnostic footprint on the target face and flexibility of operation on
multiple launch systems without the need for open optics. We present the
details of calibration (time, wavelength and spectral radiance) for absolute
temperature determination and present benchmark measurements of system
performance.Comment: 6 pages, 3 figures Davies, E., et al. (accepted). In J. Lane, T.
Germann, and M. Armstrong (Eds.), 21st Biennial APS Conference on Shock
Compression of Condensed Matter (SCCM19). AIP Publishin
S190 interpretation techniques development and application to New York State water resources
The author has identified the following significant results. The program has demonstrated that Skylab imagery can be utilized to regularly monitor eutrophication indices of lakes, such as chlorophyll concentration and photic zone depth. The relationship between the blue to green reflectance ratio and chlorophyll concentration was shown, along with changes in lake properties caused by chlorophyll, lignin, and humic acid using reflectance ratios and changes. A data processing technique was developed for detecting atmospheric fluctuations occurring over a large lake
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