Spin coherence generation in negatively charged self-assembled (In,Ga)As quantum dots by pumping excited trion states

Spin coherence generation in an ensemble of negatively charged (In,Ga)As/GaAs quantum dots was investigated by picosecond time-resolved pump-probe spectroscopy measuring ellipticity. Robust coherence of the ground-state electron spins is generated by pumping excited charged exciton (trion) states. The phase of the coherent state, as evidenced by the spin ensemble precession about an external magnetic field, varies relative to spin coherence generation resonant with the ground state. The phase variation depends on the pump photon energy. It is determined by (a) pumping dominantly either singlet or triplet excited states, leading to a phase inversion, and (b) the subsequent carrier relaxation into the ground states. From the dependence of the precession phase and the measured g factors, information about the quantum dot shell splitting and the exchange energy splitting between triplet and singlet states can be extracted in the ensemble.

Self-consistency in non-extensive thermodynamics of highly excited hadronic states

The self-consistency of a thermodynamical theory for hadronic systems based on the non-extensive statistics is investigated. We show that it is possible to obtain a self-consistent theory according to the asymptotic bootstrap principle if the mass spectrum and the energy density increase q-exponentially. A direct consequence is the existence of a limiting effective temperature for the hadronic system. We show that this result is in agreement with experiments. (C) 2012 Elsevier B.V. All rights reserved.

Non-neoplastic bulky mediastinal mass presentation in an adolescent patient: a case report

Abstract : Introduction Mediastinal masses in pediatric patients are very heterogeneous in origin and etiology. In the first decade of life, 70% of the mediastinal masses are benign whereas malignant tumors are more frequent in the second decade of life. Among the mediastinal masses, lymph nodes are the most common involved structures and could be enlarged due to a lymphoma, leukemia, metastatic disease, or due to infectious diseases as sarcoidosis, tuberculosis and others. Case presentation. We report a case of a 13-year-old Caucasian girl who came to the emergency room with a history of intermittent fever, weight loss and night sweating for at least 1 month. A radiologic image work-up presented an anterior and posterior mediastinal mass. The 18F-fluorodeoxyglucose positron emission tomography presented a high maximum standard uptake value, which directed our decision for mediastinal biopsy for diagnostic elucidation. Histologic examination described the mass as granulomatous tuberculosis. The patient was treated with anti-tuberculosis therapy and developed a full clinical recovery. Conclusions . The present case report demonstrates that a bulky mediastinal lymphadenopathy detected on 18F-fluorodeoxyglucose positron emission tomography is not always a malignant lesion, and in countries where tuberculosis is endemic, this etiology should not be forgotten during clinical investigations. There is a need for more accurate cut-off values for this technology; meanwhile, the further investigation of patients with bulky mediastinal masses with procedures such as the open biopsy is indispensable.