Photoluminescence of Gallate Glass-Ceramics: Al2O3 Influence

Glass and Ceramics - The influence of Al2O3 as an additive and the heat-treatment regime on the luminescence spectra of gallate glass-ceramics was investigated. It is shown that its luminescence...     

EPR study of Gd3+ doped lead oxide based glasses

The electron paramagnetic resonance (EPR) spectra of Gd³⁺ ions in lead germanate and lead phosphate glasses are analyzed as a function of Gd content and host composition in the temperature range between 4.2 and 300 K. The investigated samples were (40 – x)PbO·60GeO₂·xGd₂O₃ (x = 0.25, 0.5, 1, 2, 3, 4 mol%) and 97.5Pb(PO₃)₂·2.5Gd(PO₃)₃ glasses, prepared by conventional melting technique. From comparison of spectra on different samples—some of which partially crystallized—no evidence emerges of the existence of distinct types of Gd³⁺ coordination environments. The analysis of the line-broadening by increasing the Gd³⁺ content evidences that the line width of the EPR signal components is proportional to the concentration of rare earth ions, suggesting that clustering effects are negligible, at least up to 4 mol% Gd₂O₃.     

Tunable Dielectric Function in Electric‐Responsive Glass with Tree‐Like Percolating Pathways of Chargeable Conductive Nanoparticles

The design of nanostructured materials with specific physical properties is generally pursued by tuning nanoparticle size, concentration, or surface passivation. An important step forward is to realize “active” systems where nanoparticles are vehicles for controlling, in situ, some specific, tuneable features of a responsive functional material. In this perspective, this work focuses on the rational design of a nanostructured glass with electrically tuneable dielectric function obtained by injection and accumulation of charge on embedded conductive nanocrystals. This enables electrically controlled switching of semiconducting nanophases to charged polarisable states to be achieved, which could lead to smart, field‐enhancement applications in nanophotonics and plasmonics. Here, it is shown that such response switching can be obtained if a percolating charge‐transport mechanism is activated through a disordered tree‐like network, as is demonstrated to be possible in SiO₂ films where suitable dispersions of SnO₂ nanocrystals, with conductive interfaces, are obtained as a result of a new synthesis strategy.     

Time and frequency domain estimates of spontaneous baroreflex sensitivity provide early detection of autonomic dysfunction in diabetes mellitus

Diabetic autonomic dysfunction is associated with a high risk of mortality which makes its early identification clinically important. The aim of our study was to compare the detection of autonomic dysfunction provided by classical laboratory autonomic function tests with that obtained through computer assessment of the spontaneous sensitivity of the baroreceptor-heart rate reflex (BRS) by time domain and frequency domain techniques. In 20 normotensive diabetic patients (mean age +/- SD 41.9 +/- 8.1 years) with no evidence of autonomic dysfunction on laboratory autonomic testing (D0) blood pressure (BP) and ECG were continuously monitored over 15 min in the supine position. BRS was assessed as the slope of the regression line between spontaneous increases or reductions in systolic BP and linearly related lengthening or shortening in RR interval over sequences of at least 4 consecutive beats (sequence method), or as the squared ratio between RR interval and systolic BP spectral powers around 0.1 Hz. We compared the results with those of 32 age-matched normotensive diabetic patients with abnormal autonomic function tests (D1) and with those of 24 healthy age-matched control subjects with normal autonomic function tests (C). Compared to C, BRS was markedly less in D1 when assessed by both the slope of the two types of sequences (data pooled) and by the spectral method (-71.3% and -60.2% respectively, both p < 0.01). However, BRS was consistently although somewhat less markedly reduced in D0, the reduction being clearly evident for all the estimates (-57.0% and -43.5%, both p < 0.01). The effects were more evident than those obtained by the simple quantification of the RR interval variability. These data suggest that time and frequency domain estimates of spontaneous BRS allow earlier detection of diabetic autonomic dysfunction than classical laboratory autonomic tests. The estimates can be obtained by short non-invasive recording of the BP and RR interval signals in the supine patient, i.e. under conditions suitable for routine outpatient evaluation.     

Effects of caffeine on glucose tolerance: a placebo-controlled study

BACKGROUND: Leishmaniasis recidiva cutis (LRC) is rare in New World leishmaniasis. Only seven cases have been reported so far. MATERIALS AND METHODS: Four cases are reported here. Parasite diagnosis was performed by classical methods of touch preparations, histopathologic sections, and cultures. In addition, the detection of parasite DNA by the polymerase chain reaction (PCR) was performed in all cases. RESULTS: Parasites were detected by at least one of the classical methods in all primary lesions; however, only the PCR was positive in the recidivant lesions. DISCUSSION: LRC cases most likely represent a reactivation of an initial infection, probably due to the persistence of parasites in scarred tissue. Although lupoid leishmaniasis (LL) has been used as a synonym of LRC, a clear difference between LRC and LL can be defined as LL is the initial clinical presentation while LRC is a recurrent lesion. CONCLUSIONS: The results indicate that it is not appropriate to use these two denominations as synonyms. The designation of LRC should be maintained in order to define recidives occurring at the border of an old scar of cutaneous leishmaniasis, avoiding the confusion with the lupoid form of the disease.     

Structure and properties of erbium-titanium-tellurite glass

The structure of glasses of the compositions xEr₂O₃-2xTiO₂-(100-3x )TeO₂ was investigated and the glass formation region, situated in the range of 2 < x < 7 was established. The possibility of increasing the glass transition temperature and consequently the thermal stability of erbium tellurite glass by doping with titanium (IV) oxide was demonstrated.     

Structural rearrangement at the yttrium-depleted surface of HCl-processed yttrium aluminosilicate glass for Y-microsphere brachytherapy

The design of a process to create yttrium aluminosilicate microspheres with a core–shell structure is of interest in the field of cancer brachytherapy. Glass microspheres with yttrium-depleted shell may indeed reduce the risk of ⁹⁰Y release into the organism. Here we show – by means of confocal micro-Raman scattering, microfluorescence, X-ray-fluorescence analysis, and IR spectroscopy – that yttrium depletion may be achieved by etching in HCl solution (pH 2) at a rate of 1 μm day⁻¹ in bulk glass and 3 μm day⁻¹ in glass microsphere (35 μm of diameter). Importantly, the spectroscopic results – collected in confocal configuration along the processed layer – indicate a high degree of structural reconstruction of the glass network, with the formation of an interconnected silicate-rich glass that surrounds a core of unmodified yttrium aluminosilicate. We also demonstrate that the process is driven by non-bridging oxygen sites, which regulate the hydroxylation and structural reconstruction of the glass within the Y-depleted layer. The analysis gives also some insight into open fundamental questions about the short-range structure and the chemical stability of this kind of glass, which is also important in photonics and nuclear waste disposal.