2,060 research outputs found
Phonons in Nanocrystalline 57Fe
We measured the phonon density of states (DOS) of nanocrystalline Fe by resonant inelastic nuclear γ-ray scattering. The nanophase material shows large distortions in its phonon DOS. We attribute the high energy distortion to lifetime broadening. A damped harmonic oscillator model for the phonons provides a low quality factor, Qu, averaging about 5, but the longitudinal modes may have been broadened most. The nanocrystalline Fe also shows an enhancement in its phonon DOS at energies below 15 meV. The difference in vibrational entropy of the bulk and nanocrystalline Fe was small, owing to competing changes in the nanocrystalline phonon DOS at low and high energies
Coordinated inventory replenishment and outsourced transportation operatoins
Cataloged from PDF version of article.We consider a one-warehouse N retailers supply chain with stochastic demand. Inventory is managed in-house whereas transportation is outsourced to a 3PL provider. We develop analytical expressions for the operating characteristics under both periodic and continuous joint replenishment policies. We identify the settings where a periodic review policy is comparable to a continuous review one. In our numerical test-bed, the periodic policy performed best in larger supply chains operating with larger trucks. We also observed that if the excess utilization charge is less than 25%, outsourcing becomes beneficial even if outsourcing cost is 25% more than the in-house fleet costs
A general moment NRIXS approach to the determination of equilibrium Fe isotopic fractionation factors: application to goethite and jarosite
We measured the reduced partition function ratios for iron isotopes in
goethite FeO(OH), potassium-jarosite KFe3(SO4)2(OH)6, and hydronium-jarosite
(H3O)Fe3(SO4)2(OH)6, by Nuclear Resonant Inelastic X-Ray Scattering (NRIXS,
also known as Nuclear Resonance Vibrational Spectroscopy -NRVS- or Nuclear
Inelastic Scattering -NIS) at the Advanced Photon Source. These measurements
were made on synthetic minerals enriched in 57Fe. A new method (i.e., the
general moment approach) is presented to calculate {\beta}-factors from the
moments of the NRIXS spectrum S(E). The first term in the moment expansion
controls iron isotopic fractionation at high temperature and corresponds to the
mean force constant of the iron bonds, a quantity that is readily measured and
often reported in NRIXS studies.Comment: 38 pages, 2 tables, 8 figures. In press at Geochimica et Cosmochimica
Acta. Appendix C contains new derivations relating the moments of the iron
PDOS to the moments of the excitation probability function measured in
Nuclear Resonant Inelastic X-ray Scatterin
Systematic X-ray absorption study of hole doping in BSCCO - phases
X-ray absorption spectroscopy (XAS) on the O 1s threshold was applied to
Bi-based, single crystalline high temperature superconductors (HTc's), whose
hole densities in the CuO2 planes was varied by different methods. XAS gives
the intensity of the so-called pre-peak of the O 1s line due to the unoccupied
part of the Zhang-Rice (ZR) singlet state. The effects of variation of the
number n of CuO2 - planes per unit cell (n = 1,2,3) and the effect of
La-substitution for Sr for the n = 1 and n = 2 phase were studied
systematically. Furthermore the symmetry of the states could be probed by the
polarization of the impinging radiation.Comment: 4 pages, 2 figures, to appear in the proceedings of SCES2001, Ann
Arbor, August 6-10, 200
Urologist burnout: Frequency, causes, and potential solutions to an unspoken entity
Physician burnout has been linked to decreased job performance, increased medical errors, interpersonal conflicts, and depression. Recent multispecialty studies suggest that urologists have higher rates (up to 63.6%) of burnout compared to physicians in other specialties; however, these reports were limited by low sample sizes.1 We aimed to evaluate the prevalence of urologist burnout, verify risk factors, and recommend preventative measures and solutions for colleagues at risk or suffering from burnout. Urologist burnout is a true entity that transcends level of training and nationality. Its roots appear to be deep-seated in our tireless efforts to strive for excellence in care for our patients, our growing academic and research pursuits, and surmounting administrative responsibilities; these virtues, which are regarded as the foundations of our career successes, are often obtained at the expense of personal health and wellbeing, as well as family sacrifice. Various other medical societies have become increasingly vocal about the issue of physician burnout and have actively initiated successful strategies to minimize its impact on their members. As an organization with a strong national presence, the Canadian Urological Association (CUA) should promote tools to prevent and interventions to assist those at risk for and suffering from burnout. Increased awareness in the general medical community has led to strategies and tools that can help prevent, identify, or assist physicians in their recovery from burnout. The CUA should develop and facilitate access to information and offer comprehensive support for urologists struggling with burnout
Improved Bounds on Quantum Learning Algorithms
In this article we give several new results on the complexity of algorithms
that learn Boolean functions from quantum queries and quantum examples.
Hunziker et al. conjectured that for any class C of Boolean functions, the
number of quantum black-box queries which are required to exactly identify an
unknown function from C is ,
where is a combinatorial parameter of the class C. We
essentially resolve this conjecture in the affirmative by giving a quantum
algorithm that, for any class C, identifies any unknown function from C using
quantum black-box
queries.
We consider a range of natural problems intermediate between the exact
learning problem (in which the learner must obtain all bits of information
about the black-box function) and the usual problem of computing a predicate
(in which the learner must obtain only one bit of information about the
black-box function). We give positive and negative results on when the quantum
and classical query complexities of these intermediate problems are
polynomially related to each other.
Finally, we improve the known lower bounds on the number of quantum examples
(as opposed to quantum black-box queries) required for -PAC
learning any concept class of Vapnik-Chervonenkis dimension d over the domain
from to . This new lower bound comes
closer to matching known upper bounds for classical PAC learning.Comment: Minor corrections. 18 pages. To appear in Quantum Information
Processing. Requires: algorithm.sty, algorithmic.sty to buil
Interleukin-1 regulates multiple atherogenic mechanisms in response to fat feeding
Background: Atherosclerosis is an inflammatory process that develops in individuals with known risk factors that include hypertension and hyperlipidaemia, influenced by diet. However, the interplay between diet, inflammatory mechanisms and vascular risk factors requires further research. We hypothesised that interleukin-1 (IL-1) signaling in the vessel wall would raise arterial blood pressure and promote atheroma.
Methodology/Principal Findings: Apoe(-/-) and Apoe(-/-)/IL-1R1(-/-) mice were fed high fat diets for 8 weeks, and their blood pressure and atherosclerosis development measured. Apoe(-/-)/IL-R1(-/-) mice had a reduced blood pressure and significantly less atheroma than Apoe(-/-) mice. Selective loss of IL-1 signaling in the vessel wall by bone marrow transplantation also reduced plaque burden (p<0.05). This was associated with an IL-1 mediated loss of endothelium-dependent relaxation and an increase in vessel wall Nox 4. Inhibition of IL-1 restored endothelium-dependent vasodilatation and reduced levels of arterial oxidative stress.
Conclusions/Significance: The IL-1 cytokine system links atherogenic environmental stimuli with arterial inflammation, oxidative stress, increased blood pressure and atherosclerosis. This is the first demonstration that inhibition of a single cytokine can block the rise in blood pressure in response to an environmental stimulus. IL-1 inhibition may have profound beneficial effects on atherogenesis in man
Temperature and Pressure Dependence of the Fe-specific Phonon Density of States in Ba(Fe(1-x)Co(x))2As2
The {57}Fe-specific phonon density of states of Ba(Fe(1-x)Co(x))2As2 single
crystals (x=0.0, 0.08) was measured at cryogenic temperatures and at high
pressures with nuclear-resonant inelastic x-ray scattering. Measurements were
conducted for two different orientations of the single crystals, yielding the
orientation-projected {57}Fe-phonon density of states (DOS) for phonon
polarizations in-plane and out-of-plane with respect to the basal plane of the
crystal structure. In the tetragonal phase at 300 K, a clear stiffening was
observed upon doping with Co. Increasing pressure to 4 GPa caused a marked
increase of phonon frequencies, with the doped material still stiffer than the
parent compound. Upon cooling, both the doped and undoped samples showed a
stiffening, and the parent compound exhibited a discontinuity across the
magnetic and structural phase transition. These findings are generally
compatible with the changes in volume of the system upon doping, increasing
pressure, or increasing temperature, but an extra softening of high-energy
modes occurs with increasing temperature. First-principles computations of the
phonon DOS were performed and showed an overall agreement with the experimental
results, but underestimate the Grueneisen parameter. This discrepancy is
explained in terms of a magnetic Grueneisen parameter, causing an extra phonon
stiffening as magnetism is suppressed under pressure
Temperature and pressure dependence of the Fe-specific phonon density of states in Ba(Fe_(1−x)Co_x)_2As_2
The ^(57)Fe-specific phonon density of states (DOS) of Ba(Fe_(1−x)Co_x)_2As_2 single crystals (x=0.0,0.08) was measured at cryogenic temperatures and at high pressures with nuclear-resonant inelastic x-ray scattering. Measurements were conducted for two different orientations of the single crystals, yielding the orientation-projected ^(57)Fe-phonon density of states for phonon polarizations in-plane and out-of-plane with respect to the basal plane of the crystal structure. In the tetragonal phase at 300 K, a clear stiffening was observed upon doping with Co. Increasing pressure to 4 GPa caused a marked increase of phonon frequencies, with the doped material still stiffer than the parent compound. Upon cooling, both the doped and undoped samples showed a stiffening and the parent compound exhibited a discontinuity across the magnetic and structural phase transitions. These findings are generally compatible with the changes in volume of the system upon doping, increasing pressure, or increasing temperature, but an extra softening of high-energy modes occurs with increasing temperature. First-principles computations of the phonon DOS were performed and showed an overall agreement with the experimental results, but underestimate the Grüneisen parameter. This discrepancy is explained in terms of a magnetic Grüneisen parameter, causing an extra phonon stiffening as magnetism is suppressed under pressure
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