10,801 research outputs found
An approach to metal fatigue
Cumulative fatigue damage based on investigation of fatigue limit associated with crack, crack propagation rate, and stress interaction cycle in metal
Nonhypnotic low-dose etomidate for rapid correction of hypercortisolaemia in cushing's syndrome
We determined the adrenostatic potential of low-dose nonhypnotic etomidate in six patients with Cushing's syndrome (ectopic Cushing's syndrome,n=2; Cushing's disease,n=3; bilateral adrenal adenoma,n=1). Etomidate was given as a continuous infusion for 32 h in a dose of 2.5 mg/h (n=5) or 0.3 mg/kg/h (n=3), respectively. Saline was given during a control period. The responsiveness to exogenous ACTH was studied during placebo and 7 and 31 h after commencing etomidate by administration of 250 µg 1–24 ACTH i.v. Etomidate (2.5 mg/h) led to a consistent decrease in serum cortisol in all patients from a mean of 39.4±13.3 to 21.1±5.7 µg/dl after 7 h (P<0.05 compared with placebo). After 24 h cortisol was reduced further to a mean steady state concentration of 12.3±5.7 µg/dl (P<0.05). At the end of the infusion period the cortisol increase in response to ACTH was reduced but not abolished. In contrast, a dose of 0.3 mg/kg/h etomidate induced unresponsiveness of serum cortisol to exogenous ACTH within 7 h. However, sedation was observed in two out of three patients at this dose, while during etomidate in a dose of 2.5 mg/h no side effects were seen. We conclude that low-dose non-hypnotic etomidate reduces serum cortisol to within the normal range in patients with Cushing's syndrome. The possibility to dissociate the adrenostatic effect of etomidate from its hypnotic action, the absence of side effects, and the i.v. route suggest that etomidate in a dose of 0.04–0.05 mg/kg/h may become the drug of choice for rapid initial control of hypercortisolism
Modelling and Measurement of Charge Transfer in Multiple GEM Structures
Measurements and numerical simulations on the charge transfer in Gas Electron
Multiplier (GEM) foils are presented and their implications for the usage of
GEM foils in Time Projection Chambers are discussed. A small test chamber has
been constructed and operated with up to three GEM foils. The charge transfer
parameters derived from the electrical currents monitored during the
irradiation with an Fe-55 source are compared with numerical simulations. The
performance in magnetic fields up to 2 T is also investigated.Comment: 21 pages, 16 figures, submitted to NIM-
Microscopic theory for the light-induced anomalous Hall effect in graphene
We employ a quantum Liouville equation with relaxation to model the recently
observed anomalous Hall effect in graphene irradiated by an ultrafast pulse of
circularly polarized light. In the weak-field regime, we demonstrate that the
Hall effect originates from an asymmetric population of photocarriers in the
Dirac bands. By contrast, in the strong-field regime, the system is driven into
a non-equilibrium steady state that is well-described by topologically
non-trivial Floquet-Bloch bands. Here, the anomalous Hall current originates
from the combination of a population imbalance in these dressed bands together
with a smaller anomalous velocity contribution arising from their Berry
curvature. This robust and general finding enables the simulation of electrical
transport from light-induced Floquet-Bloch bands in an experimentally relevant
parameter regime and creates a pathway to designing ultrafast quantum devices
with Floquet-engineered transport properties
Private schools in the People's Republic of China: Development, modalities and contradictions
Chinese private schools may come across as a contradictory phenomenon: why would an authoritarian and officially socialist government, that needs to rely on education as an instrument of national unification and ideological control, allow for private schools and profit-making in the educational sector? However, seen against the background of the far-reaching privatisation processes that have been shaping the Chinese economy and society since the 1990s, one might equally wonder why this seemingly all-pervading privatisation wave had for a long time stopped short of the educational realm. This chapter outlines the development, modalities, and contradictions of private schools in the People’s Republic of China
Electron Energy Loss Spectroscopy of strongly correlated systems in infinite dimensions
We study the electron-energy loss spectra of strongly correlated electronic
systems doped away from half-filling using dynamical mean-field theory
(). The formalism can be used to study the loss spectra in the
optical () limit, where it is simply related to the optical
response, and hence can be computed in an approximation-free way in .
We apply the general formalism to the one-band Hubbard model off , with
inclusion of site-diagonal randomness to simulate effects of doping. The
interplay between the coherence induced plasmon feature and the
incoherence-induced high energy continuum is explained in terms of the
evolution in the local spectral density upon hole doping. Inclusion of static
disorder is shown to result in qualitative changes in the low-energy features,
in particular, to the overdamping of the plasmon feature, resulting in a
completely incoherent response. The calculated EELS lineshapes are compared to
experimentally observed EELS spectra for the normal state of the high-
materials near optimal doping and good qualitative agreement is found.Comment: 5 pages, 3 figures, submitted to J. Phys. - Cond. Mat
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Theoretical Prediction of Disrupted Min Oscillation in Flattened Escherichia coli
The dynamics of the Min-protein system help Escherichia coli regulate the process of cell division by identifying the center of the cell. While this system exhibits robust bipolar oscillations in wild-type cell shapes, recent experiments have shown that when the cells are mechanically deformed into wide, flattened out, irregular shapes, the spatial regularity of these oscillations breaks down. We employ widely used stochastic and deterministic models of the Min system to simulate cells with flattened shapes. The deterministic model predicts strong bipolar oscillations, in contradiction with the experimentally observed behavior, while the stochastic model, which is based on the same reaction-diffusion equations, predicts more spatially irregular oscillations. We further report simulations of flattened but more symmetric shapes, which suggest that the flattening and lateral expansion may contribute as much to the irregular oscillation behavior as the asymmetry of the cell shapes
Floquet dynamics in light-driven solids
We demonstrate how the properties of light-induced electronic Floquet states
in solids impact natural physical observables, such as transport properties, by
capturing the environmental influence on the electrons. We include the
environment as dissipative processes, such as inter-band decay and dephasing,
often ignored in Floquet predictions. These dissipative processes determine the
Floquet band occupations of the emergent steady state, by balancing out the
optical driving force. In order to benchmark and illustrate our framework for
Floquet physics in a realistic solid, we consider the light-induced Hall
conductivity in graphene recently reported by J.~W.~McIver, et al., Nature
Physics (2020). We show that the Hall conductivity is estimated by the Berry
flux of the occupied states of the light-induced Floquet bands, in addition to
the kinetic contribution given by the average band velocity. Hence, Floquet
theory provides an interpretation of this Hall conductivity as a
geometric-dissipative effect. We demonstrate this mechanism within a master
equation formalism, and obtain good quantitative agreement with the
experimentally measured Hall conductivity, underscoring the validity of this
approach which establishes a broadly applicable framework for the understanding
of ultrafast non-equilibrium dynamics in solids
The legacy of cover crops on the soil habitat and ecosystem services in a heavy clay, minimum tillage rotation
Abstract Cover crops are grown as potential ways to improve soil fertility, soil structure, and biodiversity, while reducing weed/pest burdens. Yet, increased costs (in both time and fuel), farmer knowledge requirements, and yield uncertainty (green bridge effect and variable crop establishment) have led to hesitation among farmers. This study was conducted at the field scale (covering an area of nearly 20 hectares) to determine whether different cover crop mixtures affected soil properties and ecosystem services on a heavy clay soil. Measurements of soil chemistry, physics, biology, weed abundance, and subsequent crop performance were taken within a minimum tillage management system, across three cover crop mixtures (commonly sold to UK farmers). The cover crop mixtures included oats (Avena sativa), radish (Raphanus sativus), phacelia (Phacelia tanacetifolia), vetch (Vicia sativa), legumes, buckwheat (Fagopyrum esculentum) and a bare stubble control followed by a spring oat crop. Soil physics (penetrometer and bulk density) and chemistry (N, P, K, Mg, Ca, and organic matter) varied little across treatments, although there was significantly lower Mg in the cover crop including legumes and an increase in NO3 within this treatment. Soil biology and botanical composition were also assessed, monitoring earthworm and mesofauna abundance; and sown and unsown (weed) biomass. Epigeic earthworms were found to have significantly larger abundance in cover crop mixtures with radish present, although other meso- and macrofauna did not differ. Significant weed suppression was found during both the cover crop growing period and as a legacy in the subsequent crop, leading to significant yield increases and economic benefits in some treatments. Our study confirms that cover crops are providing benefits, even on heavy clay soils, including improvements in nutrient leaching risk reduction, weed suppression, and crop yield, coupled with wider ecosystem benefits. We therefore consider cover crops to have a role in sustainable management of arable rotations
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