7,894 research outputs found
The LeChatelier principle: The long and the short of it
Using ordinary calculus techniques, we investigate the conditions under which LeChatelier effects are signable for finite changes in parameter values. We show, for example, that the short run demand for a factor is always less responsive to price changes than the long run demand, provided that the factor of production and the fixed factor do not switch from being substitutes to being complements (or vice versa) over the relevant range of the price change. The absence of a sign change in the complementarity/substitutability relation holds under conditions that are considerably more general than supermodularity of the production function.postprin
NbSe3: Effect of Uniaxial Stress on the Threshold Field and Fermiology
We have measured the effect of uniaxial stress on the threshold field ET for
the motion of the upper CDW in NbSe3. ET exhibits a critical behavior, ET ~ (1
- e/ec)^g, wher e is the strain, and ec is about 2.6% and g ~ 1.2. This
ecpression remains valid over more than two decades of ET, up to the highest
fields of about 1.5keV/m. Neither g nor ec is very sensitive to the impurity
concentraction. The CDW transition temperature Tp decreases linearly with e at
a rate dTp/de = -10K/%, and it does not show any anomaly near ec. Shubnikov
de-Haas measurements show that the extremal area of the Fermi surface decreases
with increasing strain. The results suggest that there is an intimate
relationship between pinning of the upper CDW and the Fermiology of NbSe3.Comment: 4 pages, 5 figure
Enhanced Decay, Inclusive Production, and the Gluon Anomaly
The experimental hint of large is linked to the
penguins via the gluon anomaly. Using running in the
-- coupling, the standard penguin alone seems
insufficient, calling for the need of dipole at 10% level from new
physics, which could also resolve the and charm counting
problems. The intereference of standard and new physics contributions may
result in direct CP asymmetries at 10% level, which could be observed soon at B
Factories.Comment: 12 pages, revtex, 3 figs. (version to appear in Phys. Rev. Lett.
Quantum Simulations on a Quantum Computer
We present a general scheme for performing a simulation of the dynamics of
one quantum system using another. This scheme is used to experimentally
simulate the dynamics of truncated quantum harmonic and anharmonic oscillators
using nuclear magnetic resonance. We believe this to be the first explicit
physical realization of such a simulation.Comment: 4 pages, 2 figures (\documentstyle[prl,aps,epsfig,amscd]{revtex}); to
appear in Phys. Rev. Let
X-ray absorption spectroscopy studies of Ba1-xCaxTiO3
[[abstract]]We report x-ray absorption near edge spectroscopy (XANES) of Ca and O K-edges of Ba1-xCaxTiO3 (x = 0, 0.01, 0.08, 1) and understand the spectral features related to the electronic structure of these perovskites. The XANES spectra of Ca K-edge possess a pre-edge peak similar to other 3d transition metals like Ti, Ni when present in perovskite structure and provides information about p-type or hole
doping. Presence of considerable amount of 3d states justifies the reason to consider it as a light 3d transition metal. The O K-edge spectra display characteristic spectral features assigned as eg and t2g and show strong dependence on concentration.[[notice]]補正完畢[[journaltype]]國外[[booktype]]紙本[[booktype]]電子版[[countrycodes]]US
Electric-octupole and pure-electric-quadrupole effects in soft-x-ray photoemission
Second-order [O(k^2), k=omega/c] nondipole effects in soft-x-ray
photoemission are demonstrated via an experimental and theoretical study of
angular distributions of neon valence photoelectrons in the 100--1200 eV
photon-energy range. A newly derived theoretical expression for nondipolar
angular distributions characterizes the second-order effects using four new
parameters with primary contributions from pure-quadrupole and octupole-dipole
interference terms. Independent-particle calculations of these parameters
account for a significant portion of the existing discrepancy between
experiment and theory for Ne 2p first-order nondipole parameters.Comment: 4 pages, 3 figure
Experimental evidence for the interplay between individual wealth and transaction network
We conduct a market experiment with human agents in order to explore the
structure of transaction networks and to study the dynamics of wealth
accumulation. The experiment is carried out on our platform for 97 days with
2,095 effective participants and 16,936 times of transactions. From these data,
the hybrid distribution (log-normal bulk and power-law tail) in the wealth is
observed and we demonstrate that the transaction networks in our market are
always scale-free and disassortative even for those with the size of the order
of few hundred. We further discover that the individual wealth is correlated
with its degree by a power-law function which allows us to relate the exponent
of the transaction network degree distribution to the Pareto index in wealth
distribution.Comment: 6 pages, 7 figure
Utilization and Outcomes of Patients with Colorectal Cancer Liver Metastases in the Medicare Population
Aggressive treatment of colorectal liver metastases (CRLM) after colectomy is increasing in the last two decades with reports of improved survival. Multiple treatment options are available for CRLM but their use and utility remains unknown.
Methods: Using SEER-Medicare linked database (1991-2005), we identified 7131 patients who had undergone colectomy with CRLM. Demographic, clinical and tumor factors were examined as determinants of therapy. Treatment options consisted of surgery (resection, ablation) or chemotherapy. Univariate and multivariate analyses were performed to determine predictors of overall survival after colectomy.
Results:635 patients (8.9%) underwent liver directed surgery defined as either a liver resection (n=495), ablation (n=216) or both (n=76) for CRLM. 322 patients (51%) were female and 313 (49%) were male. 147 patients (23%) were SES 1, 230 patients (36%) were SES 2, and 258 (41%) were SES 3. There was a survival advantage to receiving liver surgery or chemotherapy in selected patients with CRLM (p
Conclusion: In the Medicare population, patients with CRLM who receive potentially curative therapy such as resection, ablation or chemotherapy experience a substantial survival advantage; despite this only 8.9% of patients received directed therapy for their metastasis. Barriers to treatment and its underutilization must be identified to improve survival in patients diagnosed with CRLM after colectomy
Group descent algorithms for nonconvex penalized linear and logistic regression models with grouped predictors
Penalized regression is an attractive framework for variable selection
problems. Often, variables possess a grouping structure, and the relevant
selection problem is that of selecting groups, not individual variables. The
group lasso has been proposed as a way of extending the ideas of the lasso to
the problem of group selection. Nonconvex penalties such as SCAD and MCP have
been proposed and shown to have several advantages over the lasso; these
penalties may also be extended to the group selection problem, giving rise to
group SCAD and group MCP methods. Here, we describe algorithms for fitting
these models stably and efficiently. In addition, we present simulation results
and real data examples comparing and contrasting the statistical properties of
these methods
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