Rabi oscillations, coherent properties, and model qubits in two-level donor systems under terahertz radiation

Quantum confinement, magnetic-field effects, and laser coupling with the two low-lying states of electrons bound to donor impurities in semiconductors may be used to coherently manipulate the two-level donor system in order to establish the appropriate operational conditions of basic quantum bits (qubits) for solid-state based quantum computers. Here we present a theoretical calculation of the damped Rabi oscillations and time evolution of the 1s and 2p(+) donor states in bulk GaAs under an external magnetic field and in the presence of terahertz laser radiation, and their influence on the measured photocurrent. We also discuss the possible experimental conditions under which decoherence is weak and qubit operations are efficiently controlled.682

Dressed-band approach and Coulomb corrections to the light-induced exciton Stark shift

In the present work, we perform a comparison of theoretical approaches involving Coulomb-interaction corrections within the Hartree-Fock approximation and the renormalized dressed-band scheme in the large detuning limit. We focus on the well-studied optical Stark shift of the exciton peak in bulk and GaAs-(Ga,Al)As semiconductor quantum wells. It is argued that the Hartree-Fock scheme has severe limitations concerning its application to real experimental situations, even in the simplest laser field-perturbative regime. It is also shown, through a comparison between experiments and a three-band Kane-dressed GaAs-(Ga,Al)As quantum well calculation, that a proper treatment of band structure and confinement effects due to the quantum well is of fundamental importance in a theoretical understanding of Stark shift experimental measurements, and that the renormalized dressed-band approach is a very convenient tool to treat, in the large detuning limit, processes involving the laser-semiconductor interaction in low-dimensional heterostructures. (C) 2003 American Institute of Physics.9495742574

INERT-GAS ATOM-MOLECULE COLLISIONS IN A LASER FIELD - VIBRATIONAL EXCITATIONS IN HOMOPOLAR MOLECULAR-IONS

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Fast-growing pancreatic neuroendocrine carcinoma in a patient with multiple endocrine neoplasia type 1: a case report

<p>Abstract</p> <p>Introduction</p> <p>Predictive genetic screening and regular screening programs in patients with multiple endocrine neoplasia type 1 are intended to detect and treat malignant tumors at the earliest stage possible. Malignant neuroendocrine pancreatic tumors are the most frequent cause of death in these patients. However, the extent and intervals of screening in patients with multiple endocrine neoplasia type 1 are controversial as neuroendocrine tumors are usually slow growing. Here we report the case of a patient who developed a fast-growing neuroendocrine carcinoma within 15 months of a laparoscopic distal pancreatic resection.</p> <p>Case presentation</p> <p>We followed a group of 45 patients with multiple endocrine neoplasia type 1 by an annual screening program in the Department of Visceral, Thoracic, and Vascular Surgery at the University Hospital Marburg in cooperation with the Department of Radiology and the Division of Endocrinology. A man with multiple endocrine neoplasia type 1 who was diagnosed with a recurrent primary hyperparathyroidism underwent a distal pancreatic resection for a non-functional neuroendocrine tumor. In the context of our regular screening program, a large non-functional neuroendocrine tumor was diagnosed in the pancreatic head 15 months after the first pancreatic surgery. Therefore, we performed an enucleation and regional lymph node resection. At histology, the diagnosis of a neuroendocrine carcinoma with one lymph node metastasis was established. There was no evidence of recurrence 9 months after re-operation.</p> <p>Conclusion</p> <p>Fast-growing neuroendocrine tumors are rare in patients with multiple endocrine neoplasia type 1. The intervals, both postoperative and in newly diagnosed pancreatic lesions, in patients with multiple endocrine neoplasia type 1 should be reduced to 6 months to establish the early diagnosis of rapidly progressive disease in a small subset of patients.</p

Exciton properties in zincblende InGaN-GaN quantum wells under the effects of intense laser fields

ABSTRACT: In this work, we study the exciton states in a zincblende InGaN/GaN quantum well using a variational technique. The system is considered under the action of intense laser fields with the incorporation of a direct current electric field as an additional external probe. The effects of these external influences as well as of the changes in the geometry of the heterostructure on the exciton binding energy are discussed in detail

Asbestos: a hidden player behind the cholangiocarcinoma increase? Findings from a case–control analysis

PURPOSES: We conducted a case–control analysis to explore the association between occupational exposure to asbestos and cholangiocarcinoma (CC). METHODS: The study was based on historical data from 155 consecutive patients with CC [69 intrahepatic CC (ICC) and 86 extrahepatic CC (ECC)] referred to Sant’Orsola-Malpighi University Hospital between 2006 and 2010. The cases were individually matched by calendar period of birth, sex, and region of residence to historical hospital and population controls. Occupational exposure to asbestos was retrospectively assessed considering job titles obtained from work histories. Separate conditional logistic regression models were applied for ECC and ICC. Estimates were adjusted for smoking status and socioeconomic class. RESULTS: We matched 149 controls (median birth year: 1947; males: 56 %) to 41 cases of ICC (median birth year: 1946; males: 56 %) and 212 controls (median birth year: 1945; males: 48 %) to 59 cases of ECC (median birth year: 1945; males 51 %); 53 cases were not matched due to residence or birth year. We found an increased risk of ICC in workers exposed to asbestos (adjusted OR 4.81, 95 % CI 1.73–13.33); we also observed suggestive evidence that asbestos exposure might be associated with ECC (adjusted OR 2.09, 95 % CI 0.83–5.27). Sensitivity analysis restricted to patients from the Province of Bologna produced confirmatory figures. CONCLUSIONS: Our findings suggest that ICC could be associated with asbestos exposure; a chronic inflammatory pathway is hypothesized. Exposure to asbestos could be one of the determinants of the progressive rise in the incidence of ICC during the last 30 years

Regulation of MicroRNA Biogenesis: A miRiad of mechanisms

microRNAs are small, non-coding RNAs that influence diverse biological functions through the repression of target genes during normal development and pathological responses. Widespread use of microRNA arrays to profile microRNA expression has indicated that the levels of many microRNAs are altered during development and disease. These findings have prompted a great deal of investigation into the mechanism and function of microRNA-mediated repression. However, the mechanisms which govern the regulation of microRNA biogenesis and activity are just beginning to be uncovered. Following transcription, mature microRNA are generated through a series of coordinated processing events mediated by large protein complexes. It is increasingly clear that microRNA biogenesis does not proceed in a 'one-size-fits-all' manner. Rather, individual classes of microRNAs are differentially regulated through the association of regulatory factors with the core microRNA biogenesis machinery. Here, we review the regulation of microRNA biogenesis and activity, with particular focus on mechanisms of post-transcriptional control. Further understanding of the regulation of microRNA biogenesis and activity will undoubtedly provide important insights into normal development as well as pathological conditions such as cardiovascular disease and cancer

Laser dressing effects in low-dimensional semiconductor systems

A study of the effects of a laser field on the energy spectra of low-dimensional GaAs-(Ga,Al)As semiconductor systems is presented by using a Kane band-structure model for the GaAs bulk semiconductor. For a laser tuned far below any resonances, the effects of the laser-semiconductor interaction correspond to a renormalization or dressing of the semiconductor energy gap and conduction/valence effective masses. This renormalized approach may be used to give an adequate indication of the laser effects on any semiconductor heterostructures for which the effective-mass approximation provides a good physical description. As an application, it is shown that dressing effects on the donor and exciton peak energies in quantum-well heterostructures may be quite considerable and readily observable. (C) 2000 Elsevier Science Ltd. All rights reserved.1172838

Laser-dressed-band approach to shallow-impurity levels of semiconductor heterostructures

We present a simple theoretical approach to treat the interaction of a laser field with a semiconductor system, in which the effect of the laser field is incorporated within a renormalization of the semiconductor effective mass. As an application, we discuss the effects of laser dressing on the transition energies between the 1s- and 2p(+/-)-like states of hydrogenic donors in GaAs-Ga1-xAlxAs QWs, in the presence of an external homogeneous magnetic field. It is shown that the modifications on the intradonor transitions due to weak intensity-laser dressing may be as important as the effects of a strongly applied magnetic field. (C) 1998 Elsevier Science Ltd. All rights reserved.1071313