84 resultados para Rare Earths


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Tin dioxide (SnO2) thin films doped with Eu3+, are deposited by the sol-gel-dip-coating process on top of GaAs films, which is deposited by resistive evaporation on glass substrate. This heterojunction assembly presents luminescence from the rare-earth ion, unlike the SnO2 deposition directly on a glass substrate, where emissions from the Eu3+ transitions are absent. The Eu3+ transitions are clearly identified and are similar to the observation on SnO2 pressed powder (pellets), thermally treated at much higher temperatures. However, in the form of heterojunction films, the Eu emission comes along a broad band, located at higher energy compared to Eu3+ transitions, which is blue-shifted as the thermal annealing temperature increases. The size of nanocrystallites points toward quantum confinement or electron transfer between oxygen vacancies, originated from the disorder in the material, and trivalent rare-earth ions, which present acceptor-like character in this matrix. This electron transfer may relax for higher temperatures in the case of pellets, and the broad band is eliminated.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Lithium intercalation into double rare earth chromates was carried out. It was found that the compounds NaxLi1-xLa(CrO4)2 belong to the NaLa(CrO4)2 structural type and may be recommended as fast ionic conductors. At small values of x a third polymorphous modification of LiLa(CrO4)2 can be stabilized. Attempts to intercalate lithium into CsLa(CrO4)2 lead to collapse of the lamellar network with the formation of LaCrO4 and alkaline chromates. Ion exchange Li+/H+ data are consistent with these considerations. © 1994.

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We study the potential effects of anomalous couplings of the third generation quarks to gauge bosons in rare B decays. We focus on the constraints from flavor changing neutral current processes such as b→sγ and b →sl+l-. We consider both dimension-four and dimension-five operators and show that the latter can give large deviations from the standard model in the still unobserved dilepton modes, even after the bounds from b→sγ and precision electroweak observables are taken into account. ©2000 The American Physical Society.

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A 25-year-old hypertensive female patient was referred to our institution. Initial workup exams demonstrated a 2.8 cm cortical lower pole tumor in the right kidney. She underwent laparoscopic partial nephrectomy without complications. Histopathologic examination revealed a rare juxtaglomerular cell tumor known as reninoma. After surgery, she recovered uneventfully and all medications were withdrawn. Case hypothesis: Secondary arterial hypertension is a matter of great interest to urologists and nephrologists. Renovascular hypertension, primary hyperadosteronism and pheocromocytoma are potential diagnosis that must not be forgotten and should be excluded. Although rare, chronic pyelonephritis and renal tumors as rennin-producing tumors, nephroblastoma, hypernephroma, and renal cell carcinoma might also induce hypertension and should be in the diagnostic list of clinicians. Promising future implications: Approximately 5% of patients with high blood pressure have specific causes and medical investigation may usually identify such patients. Furthermore, these patients can be successfully treated and cured, most times by minimally invasive techniques. This interesting case might expand knowledge of physicians and aid better diagnostic care in future medical practice.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Pulmonary artery sarcomas (PAS) are rare and probably incurable tumours. The clinical manifestations are non-specific and very similar to that of patients with thromboembolic disease, resulting in delay of the correct diagnosis and proper treatment. We report the case of a 66-year-old woman with PAS diagnosed by computed tomography guided biopsy. Chemotherapy treatment was initiated but the patient died 11 months after diagnosis.

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Considered rare tumors, gangliogliomas account for 0.4% - 0.9% of intracranial neoplasms. The peak of its incidence occurs between 10 and 20 years of age. These tumors are composed of glial and ganglion cells and they are relatively low-grade neoplasms associated with good prognoses. We report a case of an atypical calcified ganglioglioma in an 18-year-old woman with history of four months of stabbing right-sided parietal headache, paroxysmal. On image studies were noted the presence of thick wall calcification in gangliogliomas. Although rare, this atypical ganglioglioma should be included in the differential diagnosis of lesions occurring in this area of the brain.

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Background: More than half of women present nipple discharge during reproductive age. Case: This case is about a 36 years old woman with unilateral spontaneous hyaline nipple discharge associated with breast pain. The study of scintimammography was compatible with multifocal proliferative lesion in situ. It was performed cytological smear of nipple discharge. It was paucicellular smear represented by cluster of ductal cells in three-dimensional design with hyperchromatic nuclei in the presence of myoepithelial cells. Red cells and signs of necrosis were not observed. The diagnosis of in situ ductal carcinoma was confirmed in biopsy and mastectomy specimen through the expression of calponin in myoepithelial cells at immunohistochemistry. It is known that the cytological examination of nipple discharge has low sensitivity and specificity. However, it is an easy and inexpensive procedure. Suspicious or positive results, may be important for guidance workup of patients in order to perform earlier diagnosis of malignancy. Conclusion: this case demonstrates that in situ ductal carcinoma can be characterized by positive nipple discharge, and cytology sample is an important tool for the diagnosis of suspicion of malignancy and further diagnostic investigation.