Superconducting ceramics in the Bi1.5SrCaCu2O sub x system by melt quenching technique

Bi sub 1.5 SrCaCu sub 2 O sub x has been prepared in the glassy state by rapid quenching of the melt. The kinetics of crystallization of various phases in the glass have been evaluated by a variable heating rate differential scanning calorimetry method. The formation various phases on thermal treatments of the glass has been investigated by powder X-ray diffraction and electrical resistivity measurements. Heating at 450 C formed Bi sub 2 Sr sub 2 CuO sub 6, which disappeared on further heating at 765 C, where Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8 formed. Prolonged heating at 845 C resulted in the formation of a small amount of a phase with T sub c onset of approx. 108 K, believed to be Bi sub 2 Sr sub 2 Ca sub 2 Cu sub 3 O sub 10. This specimen showed zero resistivity at 54 K. The glass ceramic approach could offer several advantages in the fabrication of the high-T sub c superconductors in desired practical shapes such as continuous fibers, wires, tapes, etc

Wealth, weather risk, and the composition and profitability of agricultural investments

Despite the growing evidence that farmers in low-income environments are risk-averse, there has been little empirical evidence on the importance of risk in shaping the actual allocation of production resources among farmers differentiated by wealth. The authors use panel data on investments in rural India to examine how the composition of productive and nonproductive asset holdings varies across farmers with different levels of total wealth and across farmers facing different degrees of weather risk. Income variability is a prominent feature of the experience of rural agents in low-income countries. The authors report evidence, based on measures of rainfall variability, that the agricultural investment portfolio behavior of farmers in such settings reflects risk aversion, due evidently to limitations on consumption-soothing mechanisms such as crop insurance or credit markets. The authors'results suggest that uninsured weather risk is a significant cause of lower efficiency and lower average incomes: a one-standard-deviation decrease in weather risk (measured by the standard deviation of the timing of the rainy season) would raise average profits by up to 35 percent among farmers in the lowest wealth quartile. Moreover, rainfall variability induces a more unequal distribution of average incomes for a given distribution of wealth. Wealthier farmers are willing to absorb significant risk without giving up profits to reduce production risk. Smaller farmers have to invest their limited wealth in ways that reduce their exposure to risk at the cost of lower profit rates. The authors found that at high levels of rainfall variability, differences in rates of profit per unit of agricultural assets were similar across classes of wealth. But over the sample range of rainfall variability, these rates of profit were always higher for the poorer farmers than for the wealthier ones, suggesting that the disadvantages of small farmers in risk diffusion are more than offset by their labor cost advantage.International Terrorism&Counterterrorism,Economic Theory&Research,Environmental Economics&Policies,Health Economics&Finance,Financial Intermediation

Wealth, Weather Risk and the Composition and Profitability of Agricultural Investments

Farm Management,

Real Exchange Rates Over the Past Two Centuries : How Important is the Harrod-Balassa-Samuelson Effect?

Using data since 1820 for the US, the UK and France, we test for the presence of real effects on the equilibrium real exchange rate (the Harrod-Balassa-Samuelson, HBS effect) in an explicitly nonlinear framework and allowing for shifts in real exchange rate volatility across nominal regimes. A statistically signifcant HBS effect for sterling-dollar captures its longrun trend and explains a proportion of variation in changes in the real rate that is proportional to the time horizon of the change. There is signifcant evidence of nonlinear reversion towards long-run equilibrium and downwards shifts in volatility during &xed nominal exchange rate regimes.purchasing power parity ; real exchange rate ; nonlinear dynamics ; Harrod-Balassa-Samuelson effect ; productivity differentials

Evaluation of FRAX® score use in Maltese osteoporosis management guidelines

Objectives: Recent years have brought a shift towards evidence-based fracture risk engines. Fracture Risk Assessment Tool (FRAX®) is one such diagnostic tool used to evaluate the ten-year probability of osteoporotic fracture risk. The aim of this study was to evaluate the Maltese FRAX® score-based osteoporosis management guidelines and identify the suitability of using such a risk factor engine-based protocol. Study design: Data from 702 patients presenting for bone mineral density (BMD) estimation in 2010- 2011 were collected. In this period, local guidelines were devised but not yet put into practice so all referred patients underwent BMD estimation. These patients were below 65 years of age and above the minimum age for FRAX® use: 40 years. Data included Age, Weight, Height, BMI and the presence of any risk factor components of the FRAX® score tool. BMD was assessed using Norland/Hologic densitometers. FRAX® scores (excluding BMD) for each patient were calculated using the online tool www.shef.ac.uk/FRAX as accessed in 2014. The resulting major osteoporotic fracture risk was compared to age-specific assessment thresholds as set by Kanis et al. (2013). Thus the appropriateness (or otherwise) of densitometry measurements as dictated by local guidelines was determined. Main outcome measures: The main outcome measures in this study were the femoral neck and vertebral body BMD. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of using the FRAX®-based guidelines in under 65 year olds were calculated. Results: Local guidelines for managing <65 year olds were found to have a PPV of 11.26% and a NPV of 94.38 % Conclusion: FRAX®-guided local guidelines are well suited at excluding non-osteoporotic patients (False omission rate of 5.62 %). Positive likelihood ratio for the protocol was found to be 1.27. This means that 1 in every 8.8 patients that would have been referred for BMD estimation were actually osteoporotic.peer-reviewe

Glottal-synchronous speech processing

Glottal-synchronous speech processing is a field of speech science where the pseudoperiodicity of voiced speech is exploited. Traditionally, speech processing involves segmenting and processing short speech frames of predefined length; this may fail to exploit the inherent periodic structure of voiced speech which glottal-synchronous speech frames have the potential to harness. Glottal-synchronous frames are often derived from the glottal closure instants (GCIs) and glottal opening instants (GOIs). The SIGMA algorithm was developed for the detection of GCIs and GOIs from the Electroglottograph signal with a measured accuracy of up to 99.59%. For GCI and GOI detection from speech signals, the YAGA algorithm provides a measured accuracy of up to 99.84%. Multichannel speech-based approaches are shown to be more robust to reverberation than single-channel algorithms. The GCIs are applied to real-world applications including speech dereverberation, where SNR is improved by up to 5 dB, and to prosodic manipulation where the importance of voicing detection in glottal-synchronous algorithms is demonstrated by subjective testing. The GCIs are further exploited in a new area of data-driven speech modelling, providing new insights into speech production and a set of tools to aid deployment into real-world applications. The technique is shown to be applicable in areas of speech coding, identification and artificial bandwidth extension of telephone speec

EVOLUTION OF IR-SELECTED GALAXIES IN Z~0.4 CLUSTERS

Wide-field optical and near--IR ($JHK$) imaging is presented for two rich galaxy clusters: Abell~370 at $z=0.374$ and Abell~851 (Cl0939+47) at $z=0.407$. Galaxy catalogs selected from the near--IR images are 90\% complete to approximately 1.5 mag below $K^\ast$ resulting in samples with $\sim$100 probable member galaxies per cluster in the central $\sim$2 Mpc. Comparison with $HST$ WFPC images yields subsamples of $\sim$70 galaxies in each cluster with morphological types. Analysis of the complete samples and the $HST$ subsamples shows that the $z\sim 0.4$ E/S0s are bluer than those in the Bower et al.\ (1992) Coma sample in the optical$-K$ color by $0.13$~mag for Abell~370 and by $0.18$~mag for Abell~851. If real, the bluing of the E/S0 populations at moderate redshift is consistent with that calculated from the Bruzual and Charlot (1993) models of passive elliptical galaxy evolution. In both clusters the intrinsic scatter of the known E/S0s about their optical$-K$ color--mag relation is small ($\sim 0.06$ mag) and not significantly different from that of Coma E/S0s as given by Bower et al.\ (1992), indicating that the galaxies within each cluster formed at the same time at an early epoch.Comment: uuencoded gzipped tar file containing latex files of manuscript (42 pages) plus tables (9 pages); figures available by anonymous ftp at ftp://ipac.caltech.edu//pub/pickup/sed ; accepted for publication in the Ap

On the Groenewold-Van Hove problem for R^{2n}

We discuss the Groenewold-Van Hove problem for R^{2n}, and completely solve it when n = 1. We rigorously show that there exists an obstruction to quantizing the Poisson algebra of polynomials on R^{2n}, thereby filling a gap in Groenewold's original proof without introducing extra hypotheses. Moreover, when n = 1 we determine the largest Lie subalgebras of polynomials which can be unambiguously quantized, and explicitly construct all their possible quantizations.Comment: 15 pages, Latex. Error in the proof of Prop. 3 corrected; minor rewritin