Microstructure and luminescence properties of the high pressure high temperature sintered AlN–TiN ceramics

Composite ceramics of titanium nitride grains incorporated in an aluminium nitride matrix have been synthesized by high pressure high temperature treatment of a mechanical mixture of AlN–TiN (3 mol % TiN) powders. The microstructure of the samples analysed by means of electron beam microanalysis and Raman spectroscopy shows that the formation of cubic AlN in the composite begins near titanium nitride grains. The areas of mixed chemical composition, which can be assigned to the formation of the solid solutions Al_1?xTi_xN, have been observed at the phase interfaces. The luminescence properties of AlN–TiN ceramics have been considered focusing on the choice of high pressure and high temperature treatment conditions. Three main components at 2.0 eV, 2.4 eV and 3.1 eV are revealed in the cathodoluminescence spectra analysed quantitatively. The observed emission originates from the radiative transitions with participation of valence band states, oxygen-vacancy centres (V_Al–O_N), nitrogen vacancies V_N, and shallow donors which form a complex system of energy levels in the bandgap of the wurtzite-type AlN.     

CSF Biomarkers Reflecting Protein Pathology and Axonal Degeneration Are Associated with Memory,Attentional, and Executive Functioning in Early-Stage Parkinson′s Disease

In early-stage Parkinson′s disease (PD), cognitive impairment is common, and a variety of cognitive domains including memory, attention, and executive functioning may be affected. Cerebrospinal fluid (CSF) biomarkers are potential markers of cognitive functioning. We aimed to explore whether CSF α-synuclein species, neurofilament light chain, amyloid-β₄₂, and tau are associated with cognitive performance in early-stage PD patients. CSF levels of total-α-synuclein and phosphorylated-α-synuclein, neurofilament light chain, amyloid-β₄₂, and total-tau and phosphorylated-tau were measured in 26 PD patients (disease duration ≤5 years and Hoehn and Yahr stage 1–2.5). Multivariable linear regression models, adjusted for age, gender, and educational level, were used to assess the relationship between CSF biomarker levels and memory, attention, executive and visuospatial function, and language performance scores. In 26 early-stage PD patients, attention and memory were the most commonly affected domains. A higher CSF phosphorylated-α-synuclein/total-α-synuclein ratio was associated with better executive functioning (sβ = 0.40). Higher CSF neurofilament light was associated with worse memory (sβ = −0.59), attentional (sβ = −0.32), and executive functioning (sβ = −0.35). Reduced CSF amyloid-β₄₂ levels were associated with poorer attentional functioning (sβ = 0.35). Higher CSF phosphorylated-tau was associated with worse language functioning (sβ = −0.33). Thus, CSF biomarker levels, in particular neurofilament light, were related to the most commonly affected cognitive domains in early-stage PD. This indicates that CSF biomarker levels may identify early-stage PD patients who are at an increased risk of developing cognitive impairment.     

Welcher molekulare Gefrierpunktswert des Wassers soll der Gefrierpunktsbestimmung der Milch zugrunde gelegt werden?

Ohne Zusammenfassung     

Evaluating the potential cost-effectiveness of stenting as a treatment for symptomatic single-vessel coronary disease. Use of a decision-analytic model

BACKGROUND: Coronary stenting appears to provide more predictable immediate results and lower rates of restenosis than conventional balloon angioplasty for selected lesion types, but its hospital costs are significantly higher. This study was designed to evaluate the potential cost-effectiveness of Palmaz-Schatz coronary stenting relative to conventional balloon angioplasty for the treatment of patients with symptomatic, single-vessel coronary disease. METHODS AND RESULTS: We developed a decision-analytic model to predict quality-adjusted life expectancy and lifetime treatment costs for patients with symptomatic, single-vessel coronary disease treated by either Palmaz-Schatz stenting (PSS) or conventional angioplasty (PTCA). Estimates of the probabilities of overall procedural success (PTCA, 97%; PSS, 98%), abrupt closure requiring emergency bypass surgery (PTCA, 1.0%; PSS, 0.6%), and angiographic restenosis (PTCA, 37%; PSS, 20%) were derived from review of the literature published as of September 1993. Procedural costs were based on the true economic (ie, variable) costs of each procedure at Boston's Beth Israel Hospital. On the basis of these data, coronary stenting was estimated to result in a higher quality-adjusted life expectancy than conventional angioplasty but to incur additional costs as well. Compared with conventional angioplasty, stenting had an estimated incremental cost-effectiveness ratio of $23,600 per quality-adjusted life year gained. Although the cost-effectiveness ratio for stenting changed with variations in assumptions about the relative costs and restenosis rates, it remained less than $40,000 per quality-adjusted year of life gained--and thus was similar to many other accepted medical treatments--unless the stent angiographic restenosis rate was > 23%, the angioplasty restenosis rate was < 34%, or the cost of stenting (including vascular complications) exceeded that of conventional angioplasty by more than $3000. The alternative strategy of secondary stenting (initial angioplasty followed by stenting only for symptomatic restenosis) was estimated to be both less effective and less cost-effective than primary stenting over a wide range of plausible assumptions and thus does not appear to be cost-effective when primary stenting is also an option. CONCLUSIONS: Decision-analytic modeling can be used to evaluate the potential cost-effectiveness of new coronary interventions. Our analysis suggests that despite its higher cost, elective coronary stenting may be a reasonably cost-effective treatment for selected patients with single-vessel coronary disease. Primary stenting is unlikely to be cost-effective for lesions with a low probability of restenosis (eg, < 30%) or for patients for whom the cost of stenting is expected to be much higher than usual (eg, because of a high risk of vascular complications). Given the sensitivity of the cost-effectiveness ratios to even modest variations in the relative restenosis rates and cost estimates, future studies will be necessary to determine more precisely the cost-effectiveness of coronary stenting for specific patient and lesion subsets.     

The cascade EM algorithm

The estimate-maximize (EM) algorithm is an iterative method for finding maximum-likelihood parameter estimates from incomplete data. The authors develop an extension of the EM algorithm that may be useful in accelerating the algorithm and in simplifying the computations involved. The extension works with an intermediate complete data specification, and performs intermediate steps at some iterations. The authors consider the problem of parameter identification of a continuous-time linear dynamic system given discrete-time observations, and show that the proposed algorithm accelerates the convergence of the EM algorithm and simplifies the computations involved     

The precaution adoption process.

Presents a critique of current models of preventive health behavior and discusses a variety of factors, including the appearance of costs and benefits over time, the role of cues to action, the problem of competing life demands, and the ways that actual decision behavior differs from the rational ideal implicit in expectancy-value and utility theories. The framework of a model that is able to accommodate these additional factors is described. This alternative model portrays the precaution adoption process as an orderly sequence of qualitatively different cognitive stages. It emphasizes the development over time of the beliefs and intentions that lead to action. (PsycINFO Database Record (c) 2010 APA, all rights reserved)