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J Phys Condens Matter ; 29(32): 325502, 2017 Aug 16.
Artículo en Inglés | MEDLINE | ID: mdl-28685711


Static and time-resolved mid-infrared spectroscopy of ferromagnetic single crystal Hg0.95Cd0.05Cr2Se4 was performed below the absorption edge, in order to reveal the origin of the electronic transitions contributing to the magneto-optical properties of this material. The mid-infrared spectroscopy reveals a strong absorption peak around 0.236 eV which formerly was assigned to a transition within the selenide-chromium complexes ([Formula: see text] Se-Cr2+). To reveal the sensitivity of the transition to the magnetic order, we performed the studies in a temperature range across the Curie temperature and magnetic fields across the value at which the saturation of ferromagnetic magnetization occurs. Despite the fact that the Curie temperature of this ferromagnetic semiconductor is around 107 K, the intensity of the mid-infrared transition reduces substantially increasing the temperature, so that already at 70 K the absorption peak is hardly visible. Such a dramatic decrease of the oscillator strength is observed simultaneously with the strong red-shift of the absorption edge in the magnetic semiconductor. Employing a time-resolved pump-and-probe technique enabled us to determine the lifetime of the electrons in the excited state of this optical transition. In the temperature range from 7 K to 80 K, the lifetime changes from 3 ps to 6 ps. This behavior agrees with the phenomenon of giant oscillator strength described earlier for weakly bound excitons in nonmagnetic semiconductors.

Artículo en Ruso | MEDLINE | ID: mdl-18379476


A comparative analysis of treatment with keppra and topamax of various types of epilepsy has been carried out in 37 patients aged from 1 to 35 years. Symptomatic temporal-frontal-lobe epilepsy was diagnosed in 22 patients, symptomatic temporal lobe epilepsy in 15 including "urgent aid" cases with previous antiepileptic therapy being ineffective. Effect of the drugs on the cerebral blood flow was studied with the single proton emission CT. Keppra treatment was assigned to 20 patients in dosages varying from 500 to 2,500 mg (30-50 mg/kg/daily) for single intake. Then the patients received the drug two times daily under the clinical and EEG control. The drug was tested for using in the "urgent care mode". The clinical effect by 43% decreasing (p<0,001) of seizures was observed in the first 12 h. The "stability state" was 80% after 8 months of the treatment. Topamax was administered to 17 patients in two dosages depending on patient's age and weight starting with 25-50 mg (from 3 to 12,5 mg/kg/daily) with the dose adjustment during 2 days. The latter was depended on the dynamics of clinical data and EEG. For the first 2 days, patients revealed changes in seizures quality: the seizure structure became less complex, without generalized seizures, and period of a seizure was shorter. Reduction of seizures frequency was observed on the 7-10th day and made up on average 73,9% (p<0,01). Comparing to keppra, topamax did not cause signs of autonomic and psychological discomfort. Generalized seizures became less frequent by the 3rd day.

Anticonvulsivantes/uso terapéutico , Electroencefalografía/métodos , Epilepsia/tratamiento farmacológico , Fructosa/análogos & derivados , Fármacos Neuroprotectores/uso terapéutico , Piracetam/análogos & derivados , Tomografía Computarizada de Emisión de Fotón Único/métodos , Adolescente , Adulto , Anticonvulsivantes/administración & dosificación , Velocidad del Flujo Sanguíneo/efectos de los fármacos , Circulación Cerebrovascular/efectos de los fármacos , Niño , Preescolar , Relación Dosis-Respuesta a Droga , Quimioterapia Combinada , Epilepsia/diagnóstico , Epilepsia/fisiopatología , Femenino , Estudios de Seguimiento , Fructosa/administración & dosificación , Fructosa/uso terapéutico , Humanos , Lactante , Levetiracetam , Masculino , Fármacos Neuroprotectores/administración & dosificación , Piracetam/administración & dosificación , Piracetam/uso terapéutico , Topiramato , Resultado del Tratamiento