Anomalous grain refinement trends during mechanical milling of Bi2Te3

The structural evolution of nanocrystalline bismuth telluride (Bi2Te3) during mechanical milling is investigated under different milling energies and temperatures. After prolonged milling, the compound evolves toward a steady-state nanostructure that is found to be unusually strongly dependent on the processing conditions. In contrast to most literature on mechanical milling, in Bi2Te3 we find that the smallest steady-state grain sizes are attained under the lowest energy milling conditions. An analysis based on the balance between refinement and recovery in the steady state shows that two regimes of behavior are expected based on the thermo-physical properties of the milled powder. Bi2Te3 lies in a relatively unusual regime where greater impact energy promotes adiabatic heating and recovery more than it does defect accumulation; hence more intense milling leads to larger steady-state grain sizes. Implications for other materials are discussed with reference to a “milling intensity map” that delineates the set of material properties for which this behavior will be observed.United States. Dept. of Energy. Office of Basic Energy Sciences (Award Number DE-SC0001299

Microwave Dielectric Heating of Drops in Microfluidic Devices

We present a technique to locally and rapidly heat water drops in microfluidic devices with microwave dielectric heating. Water absorbs microwave power more efficiently than polymers, glass, and oils due to its permanent molecular dipole moment that has a large dielectric loss at GHz frequencies. The relevant heat capacity of the system is a single thermally isolated picoliter drop of water and this enables very fast thermal cycling. We demonstrate microwave dielectric heating in a microfluidic device that integrates a flow-focusing drop maker, drop splitters, and metal electrodes to locally deliver microwave power from an inexpensive, commercially available 3.0 GHz source and amplifier. The temperature of the drops is measured by observing the temperature dependent fluorescence intensity of cadmium selenide nanocrystals suspended in the water drops. We demonstrate characteristic heating times as short as 15 ms to steady-state temperatures as large as 30 degrees C above the base temperature of the microfluidic device. Many common biological and chemical applications require rapid and local control of temperature, such as PCR amplification of DNA, and can benefit from this new technique.Comment: 6 pages, 4 figure

Metropolitan Public Library Planning Throughout the World (Book Review)

published or submitted for publicatio

Gestational diabetes in a rural setting.

Women who are already diabetic and become pregnant, as well as women who develop gestational diabetes, have increased risks of complications to both fetus and mother. These risks in gestational diabetes mellitus (GDM) can be reduced to near that of a non-diabetic mother by normalizing the blood sugar. The current recommended standards are reviewed. Utilizing a team approach, care was provided to patients with GDM in a rural primary care setting in order to attempt to normalize the blood sugar to the recommended level. Review of the outcomes of these pregnancies supports the conclusion that acceptable care for patients with GDM can be provided away from the tertiary care centers and in the primary care setting

Strategies for screening young stock for antibodies - optimising numbers to test, cut-points & predictive values for bovine viral diarrhoea virus

AbstractThe antibody seroprevalence of young stock can be a useful indicator of recent or current infection in a herd. We examine the factors that contribute to the assessment of herd exposure to disease, via spot testing for antibody, using bovine viral diarrhoea virus (BVDv) as an example. A statistical distribution of seroprevalences for BVDv in beef herds identified three groups of herds: low, intermediate and high within-herd BVDv antibody seroprevalence. We tested two assumptions –the intermediate seroprevalence group of herds is assumed to be negative for BVDv at the herd level and alternatively if this group is assumed to be positive. We found that: The herd-level sensitivity and specificity are sensitive to the assumption regarding the herds with intermediate seroprevalence. If an appropriate cut-point is chosen, reducing the sample size from ten to five does not produce a large drop in herd-level test performance. Increasing the cut-point may be valuable at the outset of an eradication programme. Increasing the sample size and decreasing the cut-point is advantageous towards the end of an eradication programme, to minimise the risk of positive herds being misclassified. The framework presented here illustrates how seroprevalence screening may be understood and assessed.</jats:p

Thermophysical properties of Co-free WC-FeCr hardmetals

Fe-Cr alloys can potentially replace carcinogenic Co as the binder system in WC-hardmetals. Furthermore, they may be used in emerging applications such as nuclear fusion reactor shielding, where use of Co is forbidden due to the formation of hazardous activated species. In such applications, a good understanding of thermophysical properties is critical to predicting high temperature performance. By combining several thermal analysis techniques (dilatometry, laser flash and calorimetry) we have determined the thermal conductivity and thermal expansivity of several grades of WC-FeCr hardmetals between room temperature and 1200 °C. In these materials the WC grain size was varied between 0.2 and 5 microns. The binder content was kept constant at 10 wt.%, and the nominal binder composition was Fe-8 wt.% Cr. The room temperature thermal conductivities of these materials varied between about 50 and 110 W/m-K, which are similar values to analogous WC-Co materials. Thermal expansion curves exhibited discontinuous shrinkage events at about 850 °C, due to an allotropic phase transition within the FeCr binder between its BCC and FCC structures. The magnitude of the shrinkage was about a third that predicted by the rule-of-mixtures, suggesting significant internal stresses could be generated during the transformation. Such internal stresses could affect the properties of WC-FeCr hardmetals when operating at high temperature