Strain-Stabilized Solid Phase Epitaxy of Si–Ge on Si.

We compare solid phase epitaxial growth of amorphous Si–Ge alloys created by Ge ion implantation into Si with and without the imposition of 0.5 GPa of externally applied biaxial tensile stress. External loading stabilizes the growth front against roughening, resulting in a doubling of the maximum reported Ge concentration for stable growth to 14 at. %. The externally applied stress appears to superpose with the intrinsic compositional stress and indicates a threshold of approximately 0.6 GPa for interface breakdown. This principle is expected to be applicable to expanding the composition range for stable growth of other semiconductor alloy combinations by other growth techniques.Engineering and Applied Science

Periodic fever syndrome and autoinflammatory diseases

The concept of autoinflammatory disease as a new disease classification has resulted in a paradigm shift in our understanding of the the broad spectrum of immunological diseases. The effectiveness of interleukin-1 blockade in a variety of disorders has resulted in a marked reduction in suffering for many of these patients

Mass Redistribution Causes the Structural Richness of Ion-Irradiated Surfaces

We show that the “sputter patterning” topographical instability is determined by the effects of ion impact-induced prompt atomic redistribution and that erosion—the consensus predominant cause—is essentially irrelevant. We use grazing incidence small angle x-ray scattering to measure in situ the damping of noise or its amplification into patterns via the linear dispersion relation. A model based on the effects of impact-induced redistribution of those atoms that are not sputtered away explains both the observed ultrasmoothening at low angles from normal incidence and the instability at higher angles.Engineering and Applied Science

Time-resolved measurements of nanoscale surface pattern formation kinetics in two dimensions on ion-irradiated Si

The nanoscale kinetics of surface topography evolution on silicon surfaces irradiated with 1 keV Ar+ ions is examined in both directions perpendicular and parallel to the projection of the ion beam on the surface. We use grazing incidence small angle x-ray scattering to measure in situ the evolution of surface morphology via the linear dispersion relation. We study the transition from surface ultra-smoothening at low angles of deviation from normal ion incidence to a pattern-forming instability at high incidence angles. A model based on the effects of impact-induced redistribution of those atoms that are not sputtered away explains both the observed ultra-smoothening at low angles from normal ion incidence and the instability at higher angles and accounts quantitatively for the measured two-dimensional dispersion relation and its dependence on incidence angle.Physic

The energy penalty of post-combustion CO2 capture & storage and its implications for retrofitting the U.S. installed base

A review of the literature has found a factor of 4 spread in the estimated values of the energy penalty for post-combustion capture and storage of CO2 from pulverized-coal (PC) fired power plants. We elucidate the cause of that spread by deriving an analytic relationship for the energy penalty from thermodynamic principles and by identifying which variables are most difficult to constrain. We define the energy penalty for CCS to be the fraction of fuel that must be dedicated to CCS for a fixed quantity of work output. That penalty can manifest itself as either the additional fuel required to maintain a power plant's output or the loss of output for a constant fuel input. Of the 17 parameters that constitute the energy penalty, only the fraction of available waste heat that is recovered for use and the 2nd-law separation efficiency are poorly constrained. We provide an absolute lower bound for the energy penalty of ~11%, and we demonstrate to what degree increasing the fraction of available-waste-heat recovery can reduce the energy penalty from the higher values reported. It is further argued that an energy penalty of ~40% will be easily achieved while one of ~29% represents a decent target value. Furthermore, we analyze the distribution of PC plants in the U.S. and calculate a distribution for the additional fuel required to operate all these plants with CO2 capture and storage (CCS).Earth and Planetary SciencesEngineering and Applied Science

Comparison of Molecular Dynamics and Binary Collision Approximation Simulations for Atom Displacement Analysis

Molecular dynamics (MD) and binary collision approximation (BCA) computer simulations are employed to study surface damage by single ion impacts. The predictions of BCA and MD simulations of displacement cascades in amorphous and crystalline silicon and BCC tungsten by $1 keV Ar^+$ ion bombardment are compared. Single ion impacts are studied at angles of $50^{\circ}, 60^{\circ} and 80^{\circ}$ from normal incidence. Four parameters for BCA simulations have been optimized to obtain the best agreement of the results with MD. For the conditions reported here, BCA agrees with MD simulation results at displacements larger than $5 \mathring{A}$ for amorphous Si, whereas at small displacements a difference between BCA and MD arises due to a material flow component observed in MD simulations but absent from a regular BCA approach due to the algorithm limitations. MD and BCA simulation results for crystalline W are found to be in a good agreement even at small displacements, while in crystalline Si there is some difference due to displacements in amorphous pockets.Engineering and Applied Science

Comparison of Structure and Properties of Femtosecond and Nanosecond Laser-Structured Silicon

We compare the optical properties, chemical composition, and crystallinity of silicon microstructures formed in the presence of SF6 by femtosecond laser irradiation and by nanosecond laser irradiation. In spite of very different morphology and crystallinity, the optical properties and chemical composition of the two types of microstructures are very similar. The structures formed with femtosecond (fs) pulses are covered with a disordered nanocrystalline surface layer less than 1 um thick, while those formed with nanosecond (ns) pulses have very little disorder. Both ns-laser-formed and fs-laser-formed structures absorb near-infrared (1.1 – 2.5 um) radiation strongly and have roughly 0.5% sulfur impurities.Engineering and Applied Science

Factors associated with anemia among women of the reproductive age group in Thatta district: Study protocol

Background: Maternal anemia is a leading public health issue placing pregnant women at higher risk of low birth weight, preterm birth, perinatal mortality, and neonatal mortality. Women in developing countries are at higher risk of anemia which could be either due to micronutrient deficiencies, hemoglobinopathies, infections or other socio-demographic factors. Thus, it is highly essential to explore the factors of anemia among women of the reproductive age group in order to design suitable interventions. The primary objective of this study is to assess the biological and socio-demographic factors that are associated with anemia among the women of the reproductive age group in Thatta district.Methods: An exploratory mixed method study using quantitative and qualitative approaches will be conducted in district Thatta Pakistan from September 2018 to January 2019. In the qualitative phase, data will be collected through focus group discussions and key informant interviews to understand the perceptions of women, their husbands and healthcare providers about anemia. In addition, a quantitative approach using cross-sectional study will be conducted to determine biological and socio-demographic factors associated with anemia. Approximately 150 non-pregnant women and their spouses will be included in the quantitative component of the study. In addition to thematic analysis for the qualitative component, Logistic regression will be done to calculate adjusted Odds ratios with their respective 95% CIs to assess the factors associated with anemia.Discussion: The better understanding of biological, socio-demographic factors and community perceptions of anemia will help us to design strategies and interventions to better address anemia during the reproductive cycle in rural areas of Pakistan. This will help the researchers and policymakers to take the appropriate action accordingly by designing suitable approaches to address the specific type of anemia in the rural population of Pakistan. This will, in turn, reduce the chances of adverse maternal and fetal outcomes associated with anemia

Crystal Growth Kinetics of Boron Oxide Under Pressure

We have measured the crystal growth rate u of B2O3-I in the amorphous phase, as it varied over five orders of magnitude with changes in temperature and pressure. We eliminated the crystal nucleation barrier by seeding the surface of boron oxide glass with crystals. u became measurable only when the pressure exceeded a threshold level near 10 kbar. Using the published thermodynamic information on the B2O3 system and a crude free-energy model for the crystal and glass phases, we account qualitatively for our results with the theory of crystal growth limited by the rate of two-dimensional nucleation of monolayers. The constants for the prefactor, activation energy, activation volume, and ledge tension are determined by fitting. By adjusting the thermodynamic parameters to a set of values that are well within the ranges delineated by their experimental uncertainties, we account quantitatively for the measured growth rates from 300 to 500 °C and from 0 to 30 kbar with the following relation: u(T,P)=(785 m/s)[||DeltaGm||/(RT)]1/6 ×exp[pi×3 Å(420 erg/cm2)2(28 cm3/mole)/(3 kTDeltaGm)]exp[−10 366 cal/mole/(RT)] ×exp[−P×16 cm3/mole/(RT)]×{1−exp[DeltaGm/(RT)]}2/3, with the driving free energy given by DeltaGm(T,P)=(13 cm3/mole) [PM(T)−P] and the melting curve given by PM(T)=(T−450 °C)/(42.6 K/kbar). The "B2O3 crystallization anomaly", that crystals have never been observed to grow at atmospheric pressure, is explained, since according to our model, the frequency of two-dimensional nucleation is negligible at all temperatures at pressures less than 10 kbarEngineering and Applied Science

Perceptions of women, their husbands and healthcare providers about anemia in rural Pakistan: Findings from a qualitative exploratory study

Background: In Pakistan, there is a dearth of literature on the perceptions of anemia among women of reproductive age (WRA). This study was undertaken to explore the perceptions of women, their husbands, and healthcare providers about anemia, its possible causes, and how anemia impacts maternal and child health in Thatta, Pakistan.Methods: A qualitative study was conducted in Thatta, Pakistan from September to December 2018. Using a pre-tested semi-structured interview (SSI), we collected data to understand their definitions of anemia through ten focus group discussions (FGDs) with women and their partners and ten primary informant interviews (KIIs) with healthcare providers. We identified six major themes: (I) Knowledge and awareness of anemia, (II) Causes and consequences of Anemia, (III) Dietary practices, (IV) Knowledge and practices regarding the use of iron-folic acid supplements, (V) Factors influencing prevention and control of anemia and (VI) Women\u27s health behavior. We analyzed the data through thematic analysis using NVivo 10 software.Results: Most community members were not aware of the term anemia but described anemia as a condition characterized by \u27blood deficiency\u27 in the body. All study participants perceived anemia as an important health problem tending to cause adverse outcomes among WRA and their children. Study participants perceived gutka (chewable tobacco) consumption as an important cause of anemia. Healthcare providers identified short inter-pregnancy intervals, lack of family planning, poor health-seeking behavior, and consumption of unhealthy food as causes of anemia in the district. Consumption of unhealthy food might not be related to related to a poorer knowledge of iron-deficient foods, but economic constraints. This was further endorsed by the healthcare providers who mentioned that most women were too poor to afford iron-rich foods. All men and women were generally well versed with the sources of good nutrition to be consumed by WRA to prevent anemia.Conclusion: The findings suggest that the government should plan to develop strategies for poverty-stricken and vulnerable rural women and plan health awareness programs to improve dietary practices, compliance with supplements, and health-seeking behavior among women of reproductive age. There is a need to develop effective counseling strategies and context-specific health education sessions to improve the health-seeking behavior of women and men in the Thatta district of Pakistan. Besides, there is need to address social determinants of health such as poverty that pushes women of poorer socioeconomic strata to eat less nutritious foods and have more anaemia. Therefore, a comprehensive and robust strategic plan need to be adopted by government that focuses not only on the awareness programs, but also aim to reduce inequities that lead to pregnant women eat iron-poor foods, which, in turn, forces them to become anemic