Localised states and their capture characteristics in amorphous phase-change materials.

As phase-change materials are poised to play a key role in next-generation computing systems, improving the current understanding of electrical transport in their amorphous phase can further strengthen their technological competitiveness. Even though the interaction of charge carriers with disorder-induced localised states largely affect the field-dependent conductivity, a clear link between electrical transport and specific features of the electronic density of states (DOS) could not be established yet due to a lack of knowledge of the capture characteristics of trap states. Here, we address this knowledge gap and employ modulated photocurrent spectroscopy (MPC) to investigate localised states in the frequently studied amorphous phase of Ge2Sb2Te5. Additionally, we present results on the DOS in the bandgap of amorphous AgIn-doped Sb2Te, which has not been subject to high-resolution DOS spectroscopy before. We find experimental evidence for clearly non-constant capture coefficients among a continuous spectrum of localised states in both studied materials. According to this observation especially in AgIn-doped Sb2Te, where no pronounced defect can be detected as main channel for carrier emission, we point out the necessity of modifying the current Poole-Frenkel-based transport modelling.

Correlation between CHA2DS2-VASc Score and Glaucoma Treatment and Prognosis.

PURPOSE: To find if CHA2DS2-VASc scale can accurately predict the treatment, prognosis, and outcome for primary open-angle glaucoma (POAG). PATIENTS AND METHODS: A survey of 250,000 patient years was taken, using the records of the Ophthalmology Department at Ziv Medical Center. Data was collected regarding the retinal nerve fiber layer (RNFL), visual field (VF), line of treatment (LOT) of glaucoma, and all the data needed to accurately calculate CHA2DS2-VASc score for each patient. RESULTS: Sixty-seven patients were included in the statistical analysis. The mean age was 72.5 years. The mean CHA2DS2-VASc score was 3.27 + -1.7. Positive Pearson's correlation coefficients were found for LOT and CHA2DS2-VASc score, 0.35, and for RNFL grade and CHA2DS2-VASc score, 0.37. The correlation was negative for RNFL width and CHA2DS2-VASc score, -0.35. CONCLUSIONS: CHA2DS2-VASc score was shown to be correlated with glaucoma. This correlation was manifested positively by the LOT needed to stop glaucoma progression, with higher CHA2DS2-VASc scores correlated with more aggressive treatment. Since glaucoma is a disease with a progressing nature, it is important to treat patients aggressively on one hand, while offering the most benign treatment as possible on the other hand. Modification of the CHA2DS2-VASc score could achieve an even higher correlation.

Projected phase-change memory devices.

Nanoscale memory devices, whose resistance depends on the history of the electric signals applied, could become critical building blocks in new computing paradigms, such as brain-inspired computing and memcomputing. However, there are key challenges to overcome, such as the high programming power required, noise and resistance drift. Here, to address these, we present the concept of a projected memory device, whose distinguishing feature is that the physical mechanism of resistance storage is decoupled from the information-retrieval process. We designed and fabricated projected memory devices based on the phase-change storage mechanism and convincingly demonstrate the concept through detailed experimentation, supported by extensive modelling and finite-element simulations. The projected memory devices exhibit remarkably low drift and excellent noise performance. We also demonstrate active control and customization of the programming characteristics of the device that reliably realize a multitude of resistance states.

Crystal growth within a phase change memory cell.

In spite of the prominent role played by phase change materials in information technology, a detailed understanding of the central property of such materials, namely the phase change mechanism, is still lacking mostly because of difficulties associated with experimental measurements. Here, we measure the crystal growth velocity of a phase change material at both the nanometre length and the nanosecond timescale using phase-change memory cells. The material is studied in the technologically relevant melt-quenched phase and directly in the environment in which the phase change material is going to be used in the application. We present a consistent description of the temperature dependence of the crystal growth velocity in the glass and the super-cooled liquid up to the melting temperature.

A cluster-randomized trial of enhanced labor ward-based PMTCT services to increase nevirapine coverage in Lusaka, Zambia.

OBJECTIVE: Determine whether enhanced labor ward-based services for prevention of mother-to-child transmission of HIV (PMTCT) would improve nevirapine (NVP) coverage. DESIGN: Cluster-randomized trial at 12 public-sector delivery centers in Lusaka, Zambia. METHODS: Following a baseline surveillance period, 12 labor wards were randomized, six to offer opt-in HIV testing to women of unknown serostatus (with NVP administration as indicated) and to assess NVP adherence among known HIV-infected women. The six control labor wards provided the standard of care. The NVP coverage endpoint was defined as the proportion of HIV-infected/exposed women/infant pairs with confirmed NVP ingestion. We used generalized estimating equations (GEE) to determine the odds of coverage associated with the intervention and ultimately used the parameters for the estimated GEE model to estimate relative risk. RESULTS: Between October 2005 and January 2006, 7664 women gave birth at participating clinics. We collected anonymous-linked blood from 7592 (99%) umbilical cords; tested 7438 (97%) for HIV, 1618 (22%) were seropositive, and of these, 1279 (79%) were tested for NVP. At baseline (preintervention), the probability of HIV-infected/exposed women/infant pairs receiving NVP in treatment clinics (42%) was 0.89 times the probability of being covered in control clinics (53%) whereas during the intervention period the probability of treatment clinic coverage (52%) was 1.22 the probability control clinic coverage (43%), representing a multiplicative effect of 1.37 upon the RR at baseline (ratio of relative risks 1.37, bootstrapped 95% CI, 1.04-1.77). CONCLUSION: Labor ward-based PMTCT programs are feasible and can have a significant, positive impact on NVP coverage.

Predictors of rapid HIV testing acceptance and successful nevirapine administration in Zambian labor wards.

BACKGROUND: Provision of HIV testing in labor provides an opportunity to reach susceptible women and infants. METHODS: As part of a cluster randomized trial of labor ward-based prevention of mother-to-child transmission services in Lusaka, Zambia, we determined predictors of testing acceptance and nevirapine (NVP) administration in labor. HIV counseling and testing were offered to women unaware of their HIV status. NVP was administered to women who tested positive, and an inert (calcium) tablet was provided to women who tested negative, to avoid stigmatization. RESULTS: Among the 2435 women who presented in labor, 393 (16%) were unaware of their HIV status, of whom 278 (71%) met eligibility criteria. We offered counseling to 217 (78%) of eligible women: 146 (67%) agreed, 82 (56%) of those counseled were tested for HIV, and 23 (28%) were seropositive. Testing rates were higher among primigravida women [adjusted odds ratio (AOR) 1.5; 95% confidence interval (CI): 1.1 to 2.1] and among those not offered HIV testing during their pregnancy (AOR 3.7; 95% CI: 2.8 to 5.1). Cervical dilation 1 hour (AOR 11.5; 95% CI: 4.5 to 29.2) and >2 hours (AOR 11.4; 95% CI: 4.7 to 27.5) before delivery. CONCLUSION: Labor ward HIV testing is feasible in this resource-limited setting.