Antimony-Doped Tin(II) Sulfide Thin Films

Thin-film solar cells made from earth-abundant, inexpensive, and nontoxic materials are needed to replace the current technologies whose widespread use is limited by their use of scarce, costly, and toxic elements. Tin monosulfide (SnS) is a promising candidate for making absorber layers in scalable, inexpensive, and nontoxic solar cells. SnS has always been observed to be a p-type semiconductor. Doping SnS to form an n-type semiconductor would permit the construction of solar cells with p-n homojunctions. This paper reports doping SnS films with antimony, a potential n-type dopant. Small amounts of antimony (1%) were found to greatly increase the electrical resistance of the SnS. The resulting intrinsic SnS(Sb) films could be used for the insulating layer in a p-i-n design for solar cells. Higher concentrations (5%) of antimony did not convert the SnS(Sb) to low-resistivity n-type conductivity, but instead the films retain such a high resistance that the conductivity type could not be determined. Extended X-ray absorption fine structure analysis reveals that the highly doped films contain precipitates of a secondary phase that has chemical bonds characteristic of metallic antimony, rather than the antimony–sulfur bonds found in films with lower concentrations of antimony.United States. Dept. of Energy. Sunshot Initiative (Contract DE-EE0005329)National Science Foundation (U.S.) (Grant CBET-1032955

Requirements for NuMA in maintenance and establishment of mammalian spindle poles

Microtubules of the mitotic spindle in mammalian somatic cells are focused at spindle poles, a process thought to include direct capture by astral microtubules of kinetochores and/or noncentrosomally nucleated microtubule bundles. By construction and analysis of a conditional loss of mitotic function allele of the nuclear mitotic apparatus (NuMA) protein in mice and cultured primary cells, we demonstrate that NuMA is an essential mitotic component with distinct contributions to the establishment and maintenance of focused spindle poles. When mitotic NuMA function is disrupted, centrosomes provide initial focusing activity, but continued centrosome attachment to spindle fibers under tension is defective, and the maintenance of focused kinetochore fibers at spindle poles throughout mitosis is prevented. Without centrosomes and NuMA, initial establishment of spindle microtubule focusing completely fails. Thus, NuMA is a defining feature of the mammalian spindle pole and functions as an essential tether linking bulk microtubules of the spindle to centrosomes

Role of Actin C-Terminus in Regulation of Striated Muscle Thin Filament

In striated muscle, regulation of actin-myosin interactions depends on a series of conformational changes within the thin filament that result in a shifting of the tropomyosin-troponin complex between distinct locations on actin. The major factors activating the filament are Ca2+ and strongly bound myosin heads. Many lines of evidence also point to an active role of actin in the regulation. Involvement of the actin C-terminus in binding of tropomyosin-troponin in different activation states and the regulation of actin-myosin interactions were examined using actin modified by proteolytic removal of three C-terminal amino acids. Actin C-terminal modification has no effect on the binding of tropomyosin or tropomyosin-troponin + Ca2+, but it reduces tropomyosin-troponin affinity in the absence of Ca2+. In contrast, myosin S1 induces binding of tropomyosin to truncated actin more readily than to native actin. The rate of actin-activated myosin S1 ATPase activity is reduced by actin truncation both in the absence and presence of tropomyosin. The Ca2+-dependent regulation of the ATPase activity is preserved. Without Ca2+ the ATPase activity is fully inhibited, but in the presence of Ca2+ the activation does not reach the level observed for native actin. The results suggest that through long-range allosteric interactions the actin C-terminus participates in the thin filament regulation

CDK5RAP2 functions in centrosome to spindle pole attachment and DNA damage response

Two domains of centrosomal protein CDK5RAP2, CNN1 and CNN2, link centrosomes to mitotic spindle poles. CNN1 lacking centrosomes are unable to recruit pericentriolar matrix components that mediate attachment to spindle poles

Selection of the appropriate method for the assessment of insulin resistance

Insulin resistance is one of the major aggravating factors for metabolic syndrome. There are many methods available for estimation of insulin resistance which range from complex techniques down to simple indices. For all methods of assessing insulin resistance it is essential that their validity and reliability is established before using them as investigations. The reference techniques of hyperinsulinaemic euglycaemic clamp and its alternative the frequently sampled intravenous glucose tolerance test are the most reliable methods available for estimating insulin resistance. However, many simple methods, from which indices can be derived, have been assessed and validated e.g. homeostasis model assessment (HOMA), quantitative insulin sensitivity check index (QUICKI). Given the increasing number of simple indices of IR it may be difficult for clinicians and researchers to select the most appropriate index for their studies. This review therefore provides guidelines and advices which must be considered before proceeding with a study

Dimension-selective attention as a possible driver of dynamic, context-dependent re-weighting in speech processing

The contribution of acoustic dimensions to an auditory percept is dynamically adjusted and reweighted based on prior experience about how informative these dimensions are across the long-term and short-term environment. This is especially evident in speech perception, where listeners differentially weight information across multiple acoustic dimensions, and use this information selectively to update expectations about future sounds. The dynamic and selective adjustment of how acoustic input dimensions contribute to perception has made it tempting to conceive of this as a form of non-spatial auditory selective attention. Here, we review several human speech perception phenomena that might be consistent with auditory selective attention although, as of yet, the literature does not definitively support a mechanistic tie. We relate these human perceptual phenomena to illustrative nonhuman animal neurobiological findings that offer informative guideposts in how to test mechanistic connections. We next present a novel empirical approach that can serve as a methodological bridge from human research to animal neurobiological studies. Finally, we describe four preliminary results that demonstrate its utility in advancing understanding of human non-spatial dimension-based auditory selective attention

Spectroscopic and Diffraction Study of Uranium Speciation in Contaminated Vadose Zone Sediments from the Hanford Site, Washington State

Contamination of vadose zone sediments under tank BX-102 at the Hanford site, Washington, resulted from the accidental release of 7-8 metric tons of uranium dissolved in caustic aqueous sludge in 1951. We have applied synchrotron-based X-ray spectroscopic and diffraction techniques to characterize the speciation of uranium in samples of these contaminated sediments. U LIII-edge X-ray absorption fine structure (XAFS) spectroscopic studies demonstrate that uranium occurs predominantly as a uranium- (VI) silicate from the uranophane group of minerals. XAFS cannot distinguish between the members of this mineral group due to the near identical local coordination environments of uranium in these phases. However, these phases differ crystallographically, and can be distinguished using X-ray diffraction (XRD) methods. As the concentration of uranium was too low for conventional XRD to detect these phases, X-ray microdiffraction (µXRD) was used to collect diffraction patterns on ~20 µm diameter areas of localized high uranium concentration found using microscanning X-ray fluorescence (µSXRF). Only sodium boltwoodite, Na(UO2)(SiO3OH)•1.5H2O, was observed; no other uranophane group minerals were present. Sodium boltwoodite formation has effectively sequestered uranium in these sediments under the current geochemical and hydrologic conditions. Attempts to remediate the uranium contamination will likely face significant difficulties because of the speciation and distribution of uranium in the sediments