1,603 research outputs found
Ultrasonic Evaluation in the Management of Postpartum Infection
To evaluate the effectiveness of ultrasound in the management of postpartum problems, ultrasonographic examination was performed on 98 patients with suspected postpartum infection. The study includes only those patients who did not respond to antibiotic treatment for at least 48 hours and those patients who were readmitted to the hospital with suspected postpartum infection. Echogenic tissue was found in the uterine cavity in 12 patients, and significant fluid collection was found in 24 patients. Gas collection appeared in the uterine cavity in five patients and around the uterine incision in four patients. Fluid collection was found around the uterine incision in five patients, and abscess formation under the abdominal incision was found in 11 patients. Although ultrasound was nondiagnostic in 31 of the 98 patients, information obtained by ultrasound could be used to reduce the duration of the infectious morbidity
An age-period-cohort analysis of obesity and incident esophageal adenocarcinoma among white males
The incidence of esophageal adenocarcinoma (EAC) has increased in recent decades. Increases in incidence have been attributed to changes in the prevalence of risk factors for EAC; however, the extent to which these changes explain increases in EAC incidence has not been studied in detail. We used age-period-cohort analysis to estimate changes in the incidence of EAC among white males by age, time period, and birth cohort. Incidence rates per 100,000 individuals were analyzed from 1973 to 2012. Hierarchical Poisson models were used to estimate age, period, and cohort effects, whereby age-specific incidence rates were nested within periods and cohorts. The prevalence of obesity for each time period and birth cohort was included in the model as a fixed-effect. Incidence increased with advancing age (β = 0.12, P <0.01). There were significant period and birth cohort effects, although the period effect was much larger than the cohort effect. The period effect decreased dramatically when obesity was included as a fixed effect, while the small cohort effect remained unchanged. Results suggest much of the increase in the incidence of EAC can be attributed to a period effect, which may be due to changes in the prevalence of obesity over time
The UN in the lab
We consider two alternatives to inaction for governments combating terrorism, which we term Defense and Prevention. Defense consists of investing in resources that reduce the impact of an attack, and generates a negative externality to other governments, making their countries a more attractive objective for terrorists. In contrast, Prevention, which consists of investing in resources that reduce the ability of the terrorist organization to mount an attack, creates a positive externality by reducing the overall threat of terrorism for all. This interaction is captured using a simple 3×3 “Nested Prisoner’s Dilemma” game, with a single Nash equilibrium where both countries choose Defense. Due to the structure of this interaction, countries can benefit from coordination of policy choices, and international institutions (such as the UN) can be utilized to facilitate coordination by implementing agreements to share the burden of Prevention. We introduce an institution that implements a burden-sharing policy for Prevention, and investigate experimentally whether subjects coordinate on a cooperative strategy more frequently under different levels of cost sharing. In all treatments, burden sharing leaves the Prisoner’s Dilemma structure and Nash equilibrium of the game unchanged. We compare three levels of burden sharing to a baseline in a between-subjects design, and find that burden sharing generates a non-linear effect on the choice of the efficient Prevention strategy and overall performance. Only an institution supporting a high level of mandatory burden sharing generates a significant improvement in the use of the Prevention strategy
Direct Neutron Capture for Magic-Shell Nuclei
In neutron capture for magic--shell nuclei the direct reaction mechanism can
be important and may even dominate. As an example we investigated the reaction
Ca(n,Ca for projectile energies below 250\,keV in a direct
capture model using the folding procedure for optical and bound state
potentials. The obtained theoretical cross sections are in agreement with the
experimental data showing the dominance of the direct reaction mechanism in
this case. The above method was also used to calculate the cross section for
Ca(n,Ca.Comment: REVTeX, 7 pages plus 3 uuencoded figures, the complete uuencoded
postscript file is available at ftp://is1.kph.tuwien.ac.at/pub/ohu/calcium.u
Persistent current of two-chain Hubbard model with impurities
The interplay between impurities and interactions is studied in the gapless
phase of two-chain Hubbard model in order to see how the screening of impurity
potentials due to repulsive interactions in single-chain model will be changed
by increasing the number of channels. Renormalization group calculations show
that charge stiffness, and hence persistent current, of the two-chain model are
less enhanced by interactions than single chain case.Comment: 4 Pages, RevTeX, No figures, Submitted to PR
Electron transport in a quantum wire with realistic Coulomb interaction
Electron transport in a quantum wire with leads is investigated with actual
Coulomb interaction taken into account. The latter includes both the direct
interaction of electrons with each other and their interaction via the image
charges induced in the leads. Exact analytical solution of the problem is found
with the use of the bosonization technique for one-dimensional electrons and
three-dimensional Poisson equation for the electric field. The Coulomb
interaction is shown to change significantly the electron density distribution
along the wire as compared with the Luttinger liquid model with short-range
interactions. In DC and low frequency regimes, the Coulomb interaction causes
the charge density to increase strongly in the vicinity of the contacts with
the leads. The quantum wire impedance shows an oscillating behavior versus the
frequency caused by the resonances of the charge waves. The Coulomb interaction
produces a frequency dependent renormalization of the charge wave velocity.Comment: 10 two-colomn revtex pages, 6 postscript figures; one figure changed,
some typos corrected, to be published in Phys.Rev.
Energy Engineering and Consulting: New Challenges and Reality
This article presents the results of studies that the authors conducted proceeding from a hypothesis that an increase of crises phenomena in the global economy, uncertainty, and higher risk along with the growing use of digital smart technology apply radically new requirements on knowledge-intensive services in the energy sector. The sector of management consulting and engineering services, which constitute the backbone of knowledge-intensive services, is faced with a new role of providing a mix of services addressing the tasks of devising anticipatory actions amid uncertainty and crisis based on forecasting. Analysis of changes in business models and the content of services indicate their strong capacity for smart logistics of complex projects, knowledge transfer in cooperation with universities and innovation institutions, managing the development of flexible technological and product solutions, and competency development in network teams. This article offers a detailed elaboration of an up-todate conceptual framework of engineering and management consulting; provides an overview of global trends; and presents a case study of collaboration problems that emerge in cross-disciplinary teams working on smart grid projects and projects of energy supply in cities based on smart grid technology. A model of proactive management and anticipatory personnel training in energy companies is proposed. This article describes the skillset needed for implementing a concept of integrated knowledge-intensive services for technological modernization and digitalization of the energy sector.The work was supported by Act 211 of the Government of the Russian Federation, contract
No. 02.A03.21.0006
Quasi-particles in Fractional Quantum Hall Effect Edge Theories
We propose a quasi-particle formulation of effective edge theories for the
fractional quantum Hall effect. For the edge of a Laughlin state with filling
fraction \nu=1/m, our fundamental quasi-particles are edge electrons of charge
-e and edge quasi-holes of charge +e/m. These quasi-particles satisfy exclusion
statistics in the sense of Haldane. We exploit algebraic properties of edge
electrons to derive a kinetic equation for charge transport between a \nu=1/m
fractional quantum Hall edge and a normal metal. We also analyze alternative
`Boltzmann' equations that are directly based on the exclusion statistics
properties of edge quasi-particles. Generalizations to more general filling
fractions (Jain series) are briefly discussed.Comment: 20 pages, 2 eps figures, revtex, references updated, Phys. Rev. B in
pres
Interactions and Disorder in Multi-Channel Quantum Wires
Recent experiments have revealed that the temperature dependence of the
conductance of quasi-ballistic quantum wires bears clear features of the
Luttinger-liquid state. In this paper, the conductance of an N-channel quantum
wire is calculated within the model of N coupled Luttinger liquids and under
the assumption of weak disorder. It is shown that as the number of channels
increases, a crossover from the Luttinger-liquid to the Fermi-liquid behavior
occurs. This crossover manifests itself in the 1/N decrease of the scaling
exponent of the temperature dependence. An exact expression for the scaling
exponent for the case of N coupled Luttinger chains is obtained, and the large
N limit is studied for the case of a quantum wire. The case of N=2 for
electrons with spin is analyzed in detail, and a qualitative agreement with the
experiment is achieved.Comment: 9 pages, REVTex with 1 Postscript figur
Theory of neutral and charged exciton scattering with electrons in semiconductor quantum wells
Electron scattering on both neutral () and charged () excitons in
quantum wells is studied theoretically. A microscopic model is presented,
taking into account both elastic and dissociating scattering. The model is
based on calculating the exciton-electron direct and exchange interaction
matrix elements, from which we derive the exciton scattering rates. We find
that for an electron density of in a GaAs QW at ,
the linewidth due to electron scattering is roughly twice as large as
that of the neutral exciton. This reflects both the larger interaction
matrix elements compared with those of , and their different dependence on
the transferred momentum. Calculated reflection spectra can then be obtained by
considering the three electronic excitations of the system, namely, the
heavy-hole and light-hole 1S neutral excitons, and the heavy-hole 1S charged
exciton, with the appropriate oscillator strengths.Comment: 18 pages, 12 figure
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