42,693 research outputs found
Emissivity measurements of reflective surfaces at near-millimeter wavelengths
We have developed an instrument for directly measuring the emissivity of reflective surfaces at near-millimeter wavelengths. The thermal emission of a test sample is compared with that of a reference surface, allowing the emissivity of the sample to be determined without heating. The emissivity of the reference surface is determined by one’s heating the reference surface and measuring the increase in emission. The instrument has an absolute accuracy of Δe = 5 x 10^-4 and can reproducibly measure a difference in emissivity as small as Δe = 10^-4 between flat reflective samples. We have used the instrument to measure the emissivity of metal films evaporated on glass and carbon fiber-reinforced plastic composite surfaces. We measure an emissivity of (2.15 ± 0.4) x 10^-3 for gold evaporated on glass and (2.65 ± 0.5) x 10^-3 for aluminum evaporated on carbon fiber-reinforced plastic composite
Fluids with quenched disorder: Scaling of the free energy barrier near critical points
In the context of Monte Carlo simulations, the analysis of the probability
distribution of the order parameter , as obtained in simulation
boxes of finite linear extension , allows for an easy estimation of the
location of the critical point and the critical exponents. For Ising-like
systems without quenched disorder, becomes scale invariant at the
critical point, where it assumes a characteristic bimodal shape featuring two
overlapping peaks. In particular, the ratio between the value of at
the peaks () and the value at the minimum in-between ()
becomes -independent at criticality. However, for Ising-like systems with
quenched random fields, we argue that instead should be observed, where is the
"violation of hyperscaling" exponent. Since is substantially non-zero,
the scaling of with system size should be easily detectable in
simulations. For two fluid models with quenched disorder, versus
was measured, and the expected scaling was confirmed. This provides further
evidence that fluids with quenched disorder belong to the universality class of
the random-field Ising model.Comment: sent to J. Phys. Cond. Mat
Balancing Company Policies And Employee Needs: A Human Resource Management Case Study
An HRM case dealing with problems encountered as employee lifestyles conflict with organizational necessity. Discussion concerns how the case is used to exhibit the alignment between HRM and business strategy
Identifying strongly correlated supersolid states on the optical lattice by quench-induced \pi-states
We consider the rapid quench of a one-dimensional strongly correlated
supersolid to a localized density wave (checkerboard) phase, and calculate the
first-order coherence signal following the quench. It is shown that unique
coherence oscillations between the even and odd sublattice sites of the
checkerboard are created by the quench, which are absent when the initial state
is described by a Gutzwiller product state. This is a striking manifestation of
the versatility of the far-from-equilbrium and nonperturbative collapse and
revival phenomenon as a microscope for quantum correlations in complex
many-body states. For the present example, this opens up the possibility to
discriminate experimentally between mean-field and many-body origins of
supersolidity.Comment: 6 pages of EPL2 style, 5 figure
Eluate derived by extracorporal antibody-based immunoadsorption elevates the cytosolic Ca2+ concentration in podocytes via B-2 kinin receptors
Background/Aim: Patients with idiopathic focal segmental glomerulosclerosis (FSGS) often develop a recurrence of the disease after kidney transplantation. In a number of FSGS patients, plasmapheresis and immunoadsorption procedures have been shown to transiently reduce proteinuria and are thought to do this by eliminating a circulating factor. Direct cellular effects of eluates from immunoadsorption procedures on podocytes, the primary target of injury in FSGS, have not yet been reported. Methods: Eluates were derived from antibody-based immunoadsorption of a patient suffering from primary FSGS, a patient with systemic lupus erythematosus, and a healthy volunteer. The cytosolic free Ca2+ concentration ({[}Ca2+](i)) of differentiated podocytes was measured by single-cell fura-2 microfluorescence measurements. Free and total immunoreactive kinin levels were measured by radioimmunoassay. Results: FSGS eluates increased the {[}Ca2+](i) levels concentration dependently (EC50 0.14 mg/ml; n = 3-19). 1 mg/ml eluate increased the {[}Ca2+](i) values reversibly from 82 +/- 12 to 1,462 +/- 370 nmol/l, and then they returned back to 100 16 nmol/l (n = 19). The eluate-induced increase of {[}Ca2+](i) consisted of an initial Ca2+ peak followed by a Ca2+ plateau which depended on the extracellular Ca2+ concentration. The eluate-induced increase of {[}Ca2+](i) was inhibited by the specific B-2 kinin receptor antagonist Hoe 140 in a concentration-dependent manner (IC50 2.47 nmol/l). In addition, prior repetitive application of bradykinin desensitized the effect of eluate on {[}Ca2+](i). A colonic epithelial cell line not reacting to bradykinin did not respond to eluate either (n = 6). Similar to FSGS eluates, the eluate preparations of both the systemic lupus patient and the healthy volunteer led to a biphasic, concentration-dependent {[}Ca2+](i) increase in poclocytes which again was inhibited by Hoe 140. Free kinins were detected in all eluate preparations. Conclusion: The procedure of antibody-based immunoadsorption leads to kinin in the eluate which elevates the {[}Ca2+](i) level of podocytes via B-2 kinin receptors. Copyright (C) 2002 S. Karger AG, Basel
Comparing PyMorph and SDSS photometry. II. The differences are more than semantics and are not dominated by intracluster light
The Sloan Digital Sky Survey pipeline photometry underestimates the
brightnesses of the most luminous galaxies. This is mainly because (i) the SDSS
overestimates the sky background and (ii) single or two-component Sersic-based
models better fit the surface brightness profile of galaxies, especially at
high luminosities, than does the de Vaucouleurs model used by the SDSS
pipeline. We use the PyMorph photometric reductions to isolate effect (ii) and
show that it is the same in the full sample as in small group environments, and
for satellites in the most massive clusters as well. None of these are expected
to be significantly affected by intracluster light (ICL). We only see an
additional effect for centrals in the most massive halos, but we argue that
even this is not dominated by ICL. Hence, for the vast majority of galaxies,
the differences between PyMorph and SDSS pipeline photometry cannot be ascribed
to the semantics of whether or not one includes the ICL when describing the
stellar mass of massive galaxies. Rather, they likely reflect differences in
star formation or assembly histories. Failure to account for the SDSS
underestimate has significantly biased most previous estimates of the SDSS
luminosity and stellar mass functions, and therefore Halo Model estimates of
the z ~ 0.1 relation between the mass of a halo and that of the galaxy at its
center. We also show that when one studies correlations, at fixed group mass,
with a quantity which was not used to define the groups, then selection effects
appear. We show why such effects arise, and should not be mistaken for physical
effects.Comment: 15 pages, 17 figures, accepted for publication in MNRAS. The PyMorph
luminosities and stellar masses are available at
https://www.physics.upenn.edu/~ameert/SDSS_PhotDec
The spherical 2+p spin glass model: an analytically solvable model with a glass-to-glass transition
We present the detailed analysis of the spherical s+p spin glass model with
two competing interactions: among p spins and among s spins. The most
interesting case is the 2+p model with p > 3 for which a very rich phase
diagram occurs, including, next to the paramagnetic and the glassy phase
represented by the one step replica symmetry breaking ansatz typical of the
spherical p-spin model, other two amorphous phases. Transitions between two
contiguous phases can also be of different kind. The model can thus serve as
mean-field representation of amorphous-amorphous transitions (or transitions
between undercooled liquids of different structure). The model is analytically
solvable everywhere in the phase space, even in the limit where the infinite
replica symmetry breaking ansatz is required to yield a thermodynamically
stable phase.Comment: 21 pages, 18 figure
Improving broadband displacement detection with quantum correlations
Interferometers enable ultrasensitive measurement in a wide array of
applications from gravitational wave searches to force microscopes. The role of
quantum mechanics in the metrological limits of interferometers has a rich
history, and a large number of techniques to surpass conventional limits have
been proposed. In a typical measurement configuration, the tradeoff between the
probe's shot noise (imprecision) and its quantum backaction results in what is
known as the standard quantum limit (SQL). In this work we investigate how
quantum correlations accessed by modifying the readout of the interferometer
can access physics beyond the SQL and improve displacement sensitivity.
Specifically, we use an optical cavity to probe the motion of a silicon nitride
membrane off mechanical resonance, as one would do in a broadband displacement
or force measurement, and observe sensitivity better than the SQL dictates for
our quantum efficiency. Our measurement illustrates the core idea behind a
technique known as \textit{variational readout}, in which the optical readout
quadrature is changed as a function of frequency to improve broadband
displacement detection. And more generally our result is a salient example of
how correlations can aid sensing in the presence of backaction.Comment: 17 pages, 5 figure
- …