Untangling the Fundamental Electronic Origins of Non-Local Electron–Phonon Coupling in Organic Semiconductors

Organic semiconductors with distinct molecular properties and large carrier mobilities are constantly developed in attempt to produce highly-efficient electronic materials. Recently, designer molecules with unique structural modifications have been expressly developed to suppress molecular motions in the solid state that arise from low-energy phonon modes, which uniquely limit carrier mobilities through electron–phonon coupling. However, such low-frequency vibrational dynamics often involve complex molecular dynamics, making comprehension of the underlying electronic origins of electron–phonon coupling difficult. In this study, first a mode-resolved picture of electron–phonon coupling in a series of materials that are specifically designed to suppress detrimental vibrational effects, is generated. From this foundation, a method is developed based on the crystalline orbital Hamiltonian population (COHP) analyses to resolve the origins—down to the single atomic-orbital scale—of surprisingly large electron–phonon coupling constants of particular vibrations, explicitly detailing the manner in which the intermolecular wavefunction overlap is perturbed. Overall, this approach provides a comprehensive explanation into the unexpected effects of less-commonly studied molecular vibrations, revealing new aspects of molecular design that should be considered for creating improved organic semiconducting materials.     

Siderophore mediated plutonium accumulation by Microbacterium flavescens (JG-9)

Uptake of plutonium and uranium mediated by the siderophore desferrioxamine-B (DFOB) has been studied for the common soil aerobe Microbacterium flavescens(JG-9). M. flavescens does not bind or take up nitrilotriacetic acid (NTA) complexes of U(VI), Fe(III), or Pu(IV) or U(VI)-DFOB but does take up Fe(III)-DFOB and Pu(IV)-DFOB. Pu(IV)-DFOB and Fe(III)-DFOB accumulations are similar: only living and metabolically active bacteria take up these metal-siderophore complexes. The Fe(III)-DFOB and Pu(IV)-DFOB complexes mutually inhibit uptake of the other, indicating that they compete for shared binding sites or uptake proteins. However, Pu uptake is much slower than Fe uptake, and cumulative Pu uptake is less than Fe, 1.0 nmol of Fe vs 0.25 nmol of Pu per mg of dry weight bacteria. The Pu(IV)-DFOB interactions with M. flavescens suggest that Pu-siderophore complexes could generally be recognized by Fe-siderophore uptake systems of many bacteria, fungi, or plants, thereby affecting Pu environmental mobility and distribution. The results also suggest that the siderophore complexes of tetravalent metals can be recognized by Fe-siderophore uptake proteins.     

Dilute Al-Mn Alloys for Low-Temperature Device Applications

We discuss results on the superconducting, electron-transport, and tunneling properties of Al doped with Mn in the range of 1000 to 3000 ppm. We demonstrate that the critical temperature of Al can be systematically reduced to below 50 mK. Films are prepared by sputter deposition, and show values of d(ln R)/d(ln T) of ～500, indicating sharp superconducting transitions. Al-Mn/I/Al-Mn tunnel junctions show low sub-gap conductance and BCS-like characteristics. Our results in general suggest that the material is of interest for transition-edge sensors operating in the 100 mK regime and superconductor/insulator/superconductor (S/I/S) and normal/insulator/ superconductor (N/I/S) devices, in the latter case where heavily doped Al-Mn can replace the normal metal.     

High-precision sizing of nanoparticles by laser transmission spectroscopy

We describe the implementation of precision laser transmission spectroscopy for sizing and counting nanoparticles in suspension. Our apparatus incorporates a tunable laser and balanced optical system that measures light transmission over a wide (210-2300 nm) wavelength range with high precision and sensitivity. Spectral inversion is employed to determine both the particle size distribution and absolute particle density. In this paper we discuss results for particles with sizes (diameters) in the range from 5 to 3000 nm. For polystyrene particles 404 to 1025 nm in size, uncertainties of ±0.5% in size and ±4% in density were obtained. For polystyrene particles from 46 to 3000 nm in size, the dynamic range of the system spans densities from ~10(3)/ml to ~10(10)/ml (5 × 10(-8) to 0.5 vol. %), implying a sensitivity 5 orders of magnitude higher than dynamic light scattering.     

The charge collection in single side silicon microstrip detectors

The transient current technique has been used to investigate signal formation in unirradiated silicon microstrip detectors, which are similar in geometry to those developed for the ATLAS experiment at LHC. Nanosecond pulsed infrared and red lasers were used to induce the signals under study. Two peculiarities in the detector performance were observed: an unexpectedly slow rise to the signal induced in a given strip when signals are injected opposite to the strip, and a long duration of the induced signal in comparison with the calculated drift time of charge carriers through the detector thickness—with a significant fraction of the charge being induced after charge carrier arrival. These major effects and details of the detector response for different positions of charge injection are discussed in the context of Ramo's theorem and compared with predictions arising from the more commonly studied phenomenon of signal formation in planar pad detectors.     

Risk of hydrocyanic acid release in the electroplating industry

This paper suggests assessing the consequences of hydrocyanic acid (HCN) release into the air by aqueous cyanide solutions in abnormal situations such as the accidental introduction of an acid, or the insertion of a cyanide in a pickling bath. It provides a well-defined source model and its resolution by methods peculiar to mass transport phenomena. The procedure consists of four stages: calculation of the liquid phase concentration, estimate of the HCN liquid-vapour equilibrium, determination of the mass transfer coefficient at the liquid-vapour interface, evaluation of the air concentration of HCN and of the damage distances. The results show that small baths operating at high temperatures are the major sources of risk. The building up of lethal air concentrations, on the other hand, is governed by the values of the mass transfer coefficient, which is itself determined by the flow dynamics and bath geometry. Concerning the magnitude of the risk, the fallout for external emergency planning is slight in all the cases investigated.     

Self-reported compliance with diabetes self-management during pregnancy

OBJECTIVE: The current study examined regimen compliance in pregnant women with pre-existing (overt) diabetes across multiple self-care tasks at three times during the pregnancy: mid-second, early third, and late third trimesters. METHOD: Forty-nine pregnant women with Type I (68%) or Type II (32%) diabetes completed measures to assess compliance with the diabetic regimen, major and minor life stressors, and social support for the diabetic regimen. RESULTS: Pregnant women with overt diabetes generally reported being compliant with their self-care regimen. There were, however, notable differences in reported compliance levels across different regimen tasks. Specifically, 74 to 79 percent of women reported being always compliant with dietary recommendations compared to 86 to 88 percent for insulin administration, 85 to 89 percent in managing insulin reactions, and 94 to 96 percent for glucose testing. Furthermore, stress in the form of major and minor life events and regimen-related social support were significantly related to self-reported compliance with dietary recommendations. There was no relationship between compliance and blood glucose levels. CONCLUSIONS: These findings suggest that psychiatric consultants focus on ways to increase social support as one means of improving compliance in pregnant women with diabetes.