Showing papers by "University of Modena and Reggio Emilia published in 1987"

Electrical transport properties of transition‐metal disilicide films

Abstract: Electrical resistivity in the temperature range of 2–1100 K and Hall‐effect measurements from 10 to 300 K of CoSi2, MoSi2, TaSi2, TiSi2, and WSi2 polycrystalline thin films were studied. Structure, composition, and impurities in these films were investigated by a combination of techniques of Rutherford backscattering spectroscopy, x‐ray diffraction, transmission electron microscopy, and Auger electron spectroscopy. These silicides are metallic, yet there is a remarkable difference in their residual resistivity values and in their temperature dependence of the intrinsic resistivities. For CoSi2, MoSi2, and TiSi2, the phonon contribution to the resistivity was found to be linear in temperature above 300 K. At high temperatures, while a negative deviation from the linearity followed by a quasisaturation was observed for TaSi2, the resistivity data of WSi2 showed a positive deviation from linearity. It is unique that the residual resistivity, ρ(2 K), of the WSi2 films is quite high, yet the temperature depend...

Subpicosecond dynamics of electron injection into GaAs/AlGaAs quantum wells

Abstract: We model the subpicosecond evolution of a nonthermal electron distribution injected into a GaAs/AlGaAs quantum well using an ensemble Monte Carlo simulation which includes electron‐electron scattering. The calculated results are in good agreement with the experimental time dependence of the carrier distribution function from recent bleaching experiments with carrier‐carrier scattering the dominant mechanism contributing to band filling.

In situ resistivity measurement of cobalt silicide formation

Abstract: In situ resistivity measurements have been utilized to study the reaction and silicide formation between cobalt and amorphous silicon thin films from room temperature to 800 °C. In conjunction, structure and composition changes were analyzed by x‐ray diffraction and Rutherford backscattering spectrometry. Formation of Co2Si, CoSi, and CoSi2 were observed. Interfacial reaction to form Co2Si occurs at approximately 400 °C. In bilayers of excess silicon, CoSi forms at approximately 520 °C and, if free silicon is still present, CoSi2 forms at about 550 °C. In the case of excess cobalt, Co2Si forms first and is followed by a cobalt‐rich solid solution. Co3Si silicide was not observed.

Quantitative structure-activity analysis in dihydropteroate synthase inhibition by sulfones. Comparison with sulfanilamides

Abstract: A set of 25 4'-, eight 2',4'-, and five 2',4',6'-substituted 4-aminodiphenyl sulfones were tested for their inhibitory activity on dihydropteroate synthase of Escherichia coli. Linear regression analysis shows that enzymic inhibition indices correlate well with both quantum chemical and spectroscopic descriptors of the electronic structure of the common moiety 4-NH2-C6H4-SO2 of the sulfones (the above descriptors being expressed in relation to the electronic structure of the enzyme substrate, p-aminobenzoate). Therefore, the biological activity of the sulfones can be related to the electronic structural resemblance between these inhibitors and the substrate of the target enzyme. Since a similar result was previously obtained for a wide series of sulfanilamides in their different (amidic, imidic, and anionic) forms, it appears possible to consider the antibacterial sulfones and sulfanilamides as a congeneric chemical series. On the basis of the present results, the classical theory of antimetabolites would appear to take on a quantitative and sound rationale.

Ritanserin, a Serotonin-S2 Receptor Antagonist, Does Not Prevent 5-Hydroxytryptophan-Induced β-EP, β-LPH and Cortisol Secretion

Abstract: Ritanserin, a new serotonin antagonist selective upon S2 receptor subclass is available. Thus, in order to better define the positive control of serotoninergic pathway on proopiomelanocortin (POMC)-related peptide release, a group of 7 healthy male volunteers has been submitted to a 5-hydroxytryptophane (5-OH-TP) test (200 mg p.o.) before and after 4 days Ritanserin pretreatment. Plasma β-endorphin (β-EP), β-lipotropin (β-LPH) and cortisol levels were measured hourly for 4 h after each 5-OH-TP loading. Hormonal levels were measured by specific RIAs on extracted (cortisol) and chromatographed (β-EP and β-LPH) plasma samples. Basal plasma concentrations of the three hormones were unchanged by Ritanserin pretreatment. Similarly, the integrated areas of β-LPH, β-EP and cortisol release in response to 5-OH-TP remained unaffected by the receptor blockade. These data confirm that serotonin-acting drugs are able to stimulate POMC-related peptide release and indicate that such interaction is not mediated through S2 receptor subclass.

Value and limitations of computerized tomography in the study of benign tumors of the bone

Abstract: In order to stress the role of CT in the evaluation of benign tumors of the bone the authors studied by means of a high-resolution CT scanner 74 patients that later underwent surgery (70 cases) and histological examination (all cases). CT findings were compared with the surgical and histological data. The results prove that the diagnostic contributions of CT are less important in the evaluation of benign than in malignant bone tumors. The major contributions of CT were:--the capability of detecting the presence of osteoid osteoma not found by means of conventional radiographic techniques;--differentiation between benign osteochondroma and peripheral chondrosarcoma by measurement of the peripheral cartilaginous cap: this criterion, on the other hand, does not seem to be always reliable and useful;--differential diagnosis of different types of cystic and fibrocystic diseases (simple and aneurysmal bone cyst, fibrous dysplasia);--evaluation of soft-tissue tumoral masses and of their extra-osseus extent in giant cell tumor and chondroblastoma; this allows us to establish the real extension of the tumor and to plan surgery more accurately.

Abnormal pro-opiomelanocortin processing in Alzheimer's disease. A case report.

Abstract: Several authors have reported reduced levels of pro-opiomelanocortin (POMC)-related peptides in the cerebrospinal fluid (CSF) of patients with Alzheimer's disease (AD), but the mechanisms regulating the CSF content of these substances are still debated. In this case report the processing of POMC peptides has been investigated post-mortem (HPLC and RIA methods) at the pituitary and hypothalamic level in an AD patient and in a control subject. From the results obtained it seems likely that defects of axonal transport and/or secretion rather than synthesis could account for the abnormalities of POMC peptides in the CSF.