71 research outputs found
Microwave-induced magnetotransport phenomena in two-dimensional electron systems: Importance of electrodynamic effects
We discuss possible origins of recently discovered microwave induced
photoresistance oscillations in very-high-electron-mobility two-dimensional
electron systems. We show that electrodynamic effects -- the radiative decay,
plasma oscillations, and retardation effects, -- are important under the
experimental conditions, and that their inclusion in the theory is essential
for understanding the discussed and related microwave induced magnetotransport
phenomena.Comment: 5 pages, including 2 figures and 1 tabl
The possibility of a metal insulator transition in antidot arrays induced by an external driving
It is shown that a family of models associated with the kicked Harper model
is relevant for cyclotron resonance experiments in an antidot array. For this
purpose a simplified model for electronic motion in a related model system in
presence of a magnetic field and an AC electric field is developed. In the
limit of strong magnetic field it reduces to a model similar to the kicked
Harper model. This model is studied numerically and is found to be extremely
sensitive to the strength of the electric field. In particular, as the strength
of the electric field is varied a metal -- insulator transition may be found.
The experimental conditions required for this transition are discussed.Comment: 6 files: kharp.tex, fig1.ps fig2.ps fi3.ps fig4.ps fig5.p
Edge and bulk effects in the Terahertz-photoconductivity of an antidot superlattice
We investigate the Terahertz(THz)-response of a square antidot superlattice
by means of photoconductivity measurements using a
Fourier-transform-spectrometer. We detect, spectrally resolved, the cyclotron
resonance and the fundamental magnetoplasmon mode of the periodic superlattice.
In the dissipative transport regime both resonances are observed in the
photoresponse. In the adiabatic transport regime, at integer filling factor
, only the cyclotron resonance is observed. From this we infer that
different mechanisms contribute to converting the absorption of THz-radiation
into photoconductivity in the cyclotron and in the magnetoplasmon resonances,
respectively.Comment: 15 pages, 4 figures, submitted to Phys. Rev.
Metal-insulator transitions in cyclotron resonance of periodic nanostructures due to avoided band crossings
A recently found metal-insulator transition in a model for cyclotron
resonance in a two-dimensional periodic potential is investigated by means of
spectral properties of the time evolution operator. The previously found
dynamical signatures of the transition are explained in terms of avoided band
crossings due to the change of the external electric field. The occurrence of a
cross-like transport is predicted and numerically confirmed
Targeting the MAPK7/MMP9 axis for metastasis in primary bone cancer
Metastasis is the leading cause of cancer related death. This multistage process involves contribution from both tumour cells and the tumour stroma to release metastatic cells into the circulation. Circulating tumour cells (CTCs) survive circulatory cytotoxicity, extravasate and colonise secondary sites effecting metastatic outcome. Reprogramming the transcriptomic landscape is a metastatic hallmark but detecting underlying master regulators that drive pathological gene expression is a key challenge, especially in childhood cancer. Here we used whole tumour plus single cell RNA sequencing in primary bone cancer and CTCs to perform weighted gene co-expression network analysis to systematically detect coordinated changes in metastatic transcript expression. This approach with comparisons applied to data collected from cell line models, clinical samples and xenograft mouse models revealed MAPK7/MMP9 signalling as a driver for primary bone cancer metastasis. RNAi knockdown of MAPK7 reduces proliferation, colony formation, migration, tumour growth, macrophage residency/polarisation and lung metastasis. Parallel to these observations were reduction of activated interleukins IL1B, IL6, IL8 plus mesenchymal markers VIM and VEGF in response to MAPK7 loss. Our results implicate a newly discovered, multidimensional MAPK7/MMP9 signalling hub in primary bone cancer metastasis that is clinically actionable
Simulation of an oxic-settling-anaerobic pilot plant operated under real conditions using the activated sludge model no.2d
Oxic-settling-anaerobic (OSA) process has been introduced into the treatment line of wastewater in order to upgrade activated sludge processes and to reduce the production of excess sludge. The aim of the present study was to simulate the performance of an OSA pilot plant by implementing the Activated Sludge Model No.2d (ASM2d) into a mathematical modelling software (BioWin). The stepwise calibration, performed both by off-line experiments and software dynamic calibration, was carried out in a heuristic way, adjusting the parameters values that showed a major influence to the effluent and internal concentrations. All the reduction factors introduced into ASM2d to simulate the processes occurring in anoxic and anaerobic conditions were lowered in order to reproduce the concentrations of interest. In addition, the values of parameters of the PAOs (polyphosphate accumulating organisms)-related process (namely qPHA and YPO4 ) were found lower than those usually adopted. In general, theoretical results were in good agreement with the experimental data obtained from plant’s operation, showing an accurate predictive capacity of the model. Good performance was achieved considering the phosphorus removal related process, while some failures were detected in COD and ammonia simulations
Factors associated with back pain in nursing staff: A survey in Athens, Greece
Factors associated with self-reported back pain were investigated using questionnaire data on 407 female nurses from a large hospital in Athens, Greece. Factor analysis was used to construct indices of pain and its impact on normal life, and also to summarize work load descriptions. Pain factors were examined in relation to work load and personal characteristics by logistic regression. Statistically significant items, in relation both to pain and impact, were the existence of previous back injury, self-reported headaches and the 'carrying and lifting' factor of work load which principally included moving equipment. Age, height and weight were not associated with back pain. Compared to a similar study by Harber and colleagues in California, United States of Amercia, the factors associated with back pain were quite similar in this study even though the prevalence of back pain was much higher among Greek nurses and their work load was physically much more demanding
Combined effects of smoking and hypercholesterolemia on inflammatory process, thrombosis/fibrinolysis system, and forearm hyperemic response.
The combined effects of smoking and hypercholesterolemia on the inflammatory process, the thrombosis/fibrinolysis system, and forearm hyperemic response were investigated. It was shown that smokers with hypercholesterolemia (n = 25) had a reduced and delayed forearm hyperemic response compared with healthy smokers (n = 24), patients with hypercholesterolemia (n = 26), and healthy controls (n = 75; p <0.01 for all). This phenomenon was associated with a respective increase in the inflammatory process and changes in the thrombosis/fibrinolysis system
Combined effects of smoking and hypercholesterolemia on inflammatory process, thrombosis/fibrinolysis system, and forearm hyperemic response
The combined effects of smoking and hypercholesterolemia on the
inflammatory process, the thrombosis/fibrinolysis system, and forearm
hyperemic response were investigated. It was shown that smokers with
hypercholesterolemia (n = 25) had a reduced and delayed forearm
hyperemic response compared with healthy smokers (n = 24), patients with
hypercholesterolemia (n 26), and healthy controls (n = 75; p < 0.01 for
all). This phenomenon was associated with a respective increase in the
inflammatory process and changes in the thrombosis/fibrinolysis system.
(C) 2004 by Excerpta Medica, Inc
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