Recombination parameters in low-resistivity gamma-irradiated η-type germanium

Studies of recombination in ～0.2 Ω-cm As- and Sb-doped Co⁶⁰ γ-irradiated Ge which yield energy levels and the temperature dependence of the electron and hole capture probabilities are reported. For Sb-doped material at 323°K, the recombination center energy level position (neglecting statistical weight) was found to be 0.361±0.005 eV above the valence band with a possible slight temperature dependence corresponding roughly to one-half the variation of band gap with temperature. The capture probability ratio at this same temperature was 740. For the Asdoped case, two different levels appear to dominate the recombination process in annealed and unannealed low resistivity material. The energy level positions relative to the valence band (neglecting statistical weight) are 0.327±0.005 eV and 0.37±0.01 eV at room temperature for the annealed and unannealed samples, respectively. The corresponding capture probability ratios are 650 and 810. As in the case of Sb-doping, the energy level appears to shift with temperature at about one-half the rate of the shift in band gap energy.     

Braid groups and Hodge theory

This paper gives an account of the unitary representations of the braid group that arise via the Hodge theory of cyclic branched coverings of ${\mathbb{P}^1}$ , highlighting their connections with ergodic theory, complex reflection groups, moduli spaces of 1-forms and open problems in surface topology.     

Global sensitivity measures from given data

Simulation models support managers in the solution of complex problems. International agencies recommend uncertainty and global sensitivity methods as best practice in the audit, validation and application of scientific codes. However, numerical complexity, especially in the presence of a high number of factors, induces analysts to employ less informative but numerically cheaper methods. This work introduces a design for estimating global sensitivity indices from given data (including simulation input–output data), at the minimum computational cost. We address the problem starting with a statistic based on the L¹-norm. A formal definition of the estimators is provided and corresponding consistency theorems are proved. The determination of confidence intervals through a bias-reducing bootstrap estimator is investigated. The strategy is applied in the identification of the key drivers of uncertainty for the complex computer code developed at the National Aeronautics and Space Administration (NASA) assessing the risk of lunar space missions. We also introduce a symmetry result that enables the estimation of global sensitivity measures to datasets produced outside a conventional input–output functional framework.     

Exponentiation of infinite dimensional Z-graded lie algebras

In this article we give a new technique for exponentiating infinite dimensional graded representations of graded Lie algebras that allows for the exponentiation of some non-locally nilpotent elements. Our technique is to naturally extend the representation of the Lie algebra g on the space V naturally to a representation on a subspace £ of the dual space V ^*. After introducing the technique, we prove that it enables the exponentiation of all elements of free Lie Algebras and afhne Kac-Moody Lie algebras.     

Photolytic Reductive Elimination of White Phosphorus from a Mononuclear cyclo‐P4 Transition Metal Complex

Elemental white phosphorus (P₄) is well recognized as a critical precursor to organophosphorus compounds. However, regulatory constraints stemming from the toxic and pyrophoric nature of white phosphorus have significantly limited its accessibility. Herein is described a new approach to white phosphorus storage and release based on a unique example of photolytic reductive elimination of the tetrahedral P₄ molecule from a mononuclear cyclo‐P₄ molybdenum complex. The latter functions as an air‐stable, chemically‐deactivated source of white phosphorus. The system features efficient photo‐release of white phosphorus using inexpensive violet LED sources. Additionally, high‐yield recapture of unspent white phosphorus by the molybdenum center can be achieved by post‐photolysis heating at convenient temperatures.     

Reduction of turbulent boundary layer induced interior noise through active impedance control

The use of a single actuator tuned to an optimum impedance to control the sound power radiated from a turbulent boundary layer (TBL) excited aircraft panel into the aircraft interior is examined. An approach to calculating the optimum impedance is defined and the limitations on the reduction in radiated power by a single actuator tuned to that impedance are examined. It is shown that there are too many degrees of freedom in the TBL and in the radiation modes of the panel to allow a single actuator to control the radiated power. However, if the panel modes are lightly damped and well separated in frequency, significant reductions are possible. The implementation of a controller that presents a desired impedance to a structure is demonstrated in a laboratory experiment, in which the structure is a mass. The performance of such a controller on an aircraft panel is shown to be effective, if the actuator impedance is similar to but not the same as the desired impedance, provided the panel resonances are well separated in frequency and lightly damped.     

Opposed type double stage cell for Mbar pressure experiment with large sample volume

ABSTRACT

A new opposed type double-stage large volume cell has been developed to compress large volume samples to more than 100?GPa (Mbar) pressure. A pair of second-stage diamond anvils is introduced into the first-stage Paris–Edinburgh press. The double-stage large volume cell allows the generation of ultrahigh pressures using a large culet diameter of the second-stage diamond anvils (diameters of 0.5–1.2?mm). Pressure generation up to 131?GPa has been achieved by using the culet diameter of 0.5?mm. Sample volume of the double-stage large volume cell can be more than ～100 times larger than that of conventional Mbar experiment using a diamond anvil cell. The double-stage large volume cell has a large opening in the horizontal plane for X-ray measurements, which is particularly suited for the multi-angle energy dispersive X-ray diffraction measurement, thus opening a new way of in situ structural determinations of amorphous materials at Mbar pressures.     

Effects of aromatic regularity on the structure and conductivity of polyimide‐poly(ethylene glycol) materials doped with ionic liquid

An understanding of the structure and properties of polymer electrolyte systems can be crucial to a variety of different applications. The current work performs a study of the composition, structure and properties of poly(ethylene glycol) (PEG)‐aromatic polyimide systems incorporating ionic liquids that are relevant to several applications especially fuel cell membranes. Composition was varied through using different aromatic dianhydrides, aromatic diamines and in some cases synthesis solvent. Properties were characterized using Fourier transform infrared spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, small‐angle x‐ray scattering, electrochemical impedance spectroscopy and cyclic voltammetry. By varying solvent, aromatic regularity and expected rigidity can be tuned, impacting average conductivity by 30%. Varying the aromatic diamine can influence the length scale and amount of aromatic regularity, which can ultimately affect the conductivity by a factor of four. The maximum conductivity reached was 83 mS/cm at 80 °C and 70 %RH. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 509–521