56 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
Frequency-dependent magnetotransport and particle dynamics in magnetic modulation systems
We analyze the dynamics of a charged particle moving in the presence of
spatially-modulated magnetic fields. From Poincare surfaces of section and
Liapunov exponents for characteristic trajectories we find that the fraction of
pinned and runaway quasiperiodic orbits {\em vs}. chaotic orbits depends
strongly on the ratio of cyclotron radius to the structure parameters, as well
as on the amplitude of the modulated field. We present a complete
characterization of the dynamical behavior of such structures, and investigate
the contribution to the magnetoconductivity from all different orbits using a
classical Kubo formula. Although the DC conductivity of the system depends
strongly on the pinned and runaway trajectories, the frequency response
reflects the topology of all different orbits, and even their unusual temporal
behavior.Comment: Submitted to PRB - 14 figure files - REVTEX tex
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.
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
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
Transperitoneal laparoscopic right radical nephrectomy for renal cell carcinoma and end-stage renal disease: a case report
Nephron-sparing surgery (partial nephrectomy) results are similar to those of radical nephrectomy for small (<4 cm) renal tumors. However, in patients with end-stage renal disease, radical nephrectomy emerges as a more efficient treatment for localized renal cell cancer. Laparoscopic radical nephrectomy (LRN) increasingly is being performed. The objective of the present study was to present a case of a patient under hemodialysis who was submitted to LRN for a small renal mass and discuss the current issues concerning this approach. It appears that radical nephrectomy should be the standard treatment in dialysis patients even for small tumors. The laparoscopic technique is associated with acceptable cancer-specific survival and recurrence rate along with shorter hospital stay, less postoperative pain and earlier return to normal activities
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
Lessons learned from first case of Cesarean delivery in a COVID-19 positive parturient in Greek region
We report the successful anesthetic management of a 24-year-old patient, with an active COVID-19 viral infection, scheduled for elective Cesarean section at 40th week of pregnancy. This was the first case in Greek region, and we report and discuss the difficulties and safety issues regarding a COVID-19 positive patient during an elective cesarean delivery. Regional anesthesia with full protective equipment for health personnel involved, along with careful planning and adherence to guidelines achieved safe completion of the operation. © 2020 Wolters Kluwer Medknow Publications. All rights reserved
Evaluation of the Effective Hole masses in Pseudomorphic Compressively Strained GaxIn1-xAs/InP Quantum Wells
The valance band structure of metalorganic vapor phase epitaxy (MOVPE) grown strained GaxIn1 � xAs/InP single quantum well structures is experimentally verified by the determination of the effective in-plane hole masses. The masses are obtained by performing magnetotransport experiments. Mobilities up to 8700 cm2/V s for gallium content of x=0.3 were reached. The effective heavy hole masses of compressively strained GaInAs are drastically reduced compared to bulk material in excellent agreement to calculations using the k · p-perturbation theory, whereas the masses of the uppermost valence band of tensile strained material appear to be rather high. Consequently, no experimental determination was possible in the latter case. A precise analysis of the Shubnikov�de Haas oscillation patterns of compressively strained quantum wells shows a spin splitting of the uppermost heavy hole band, containing two different effective masses
An Integrated Framework of Environmental Physics and Epidemiology: The Biometeorological Aspect of Thermal Environment and Health Project (BeAT Heat)
This article presents the Biometeorological Aspect of Thermal environment and Health (BeAT Heat) project, an integrated framework for the assessment of thermal perception that could assist in developing successful public health measures by local authorities and policymakers. BeAT Heat is conducted in Cyprus, a country of the eastern Mediterranean region. The study focuses on identifying models that best simulate thermal sensation, evaluating the spatial distribution of the state of the thermal environment and by means of this the thermal burden using satellite remote sensing methods, and determining the impact of thermal environment on the health of general and vulnerable populations. © 2021, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG
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