bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of the rate of force development scaling factor for the hip muscles
Authors: Casartelli Nicola C. , Lepers Romuald , Maffiuletti Nicola A.
Published: March 2014

Introduction: The aim of this study was to evaluate test feasibility, validity, and reproducibility of the rate of force development scaling factor (RFD‐SF) for the hip muscles. Methods: Feasibility was assessed as the testing compliance, validity as the ability to compute the RFD‐SF from a linear regression, and reproducibility with a test–retest design in 20 healthy subjects. Reliability and agreement (reproducibility) were evaluated using intraclass correlation coefficient (ICC3,1) and percent standard error of measurement (SEM), respectively. Results: The RFD‐SF testing protocol was completed successfully by all subjects, although the analysis had to be modified for hip rotators. Reliability was high (ICC3,1 > 0.70) for all muscles except hip abductors (ICC3,1 = 0.69) and internal rotators (ICC3,1 = 0.58). Agreement was high for all muscles (SEM < 10%). Conclusions: Hip adductor, flexor, and external rotator RFD‐SF can be evaluated with confidence, provided the analysis is modified for external rotators, whereas hip abductor and internal rotator RFD‐SF assessment is not recommended. Muscle Nerve 50: 932–938, 2014
The Incorporation of Predictive Genomic Testing into Genetic Counseling Programs
Authors: Noss Ryan , Mills Rachel , Callanan Nancy
Published: March 2014

This study explored whether genetic counseling programs are incorporating instruction about the applications and techniques of predictive genomic testing (PGT) based on student recollection, and whether this is perceived as adequate by those students. For the purpose of this study, PGT was defined as the use of genome‐based testing to assess a person's risk, or susceptibility, of developing a disorder with either a known or suspected genetic component. Surveys from 114 graduates were analyzed. The majority of respondents indicated that PGT was covered in their curriculum including methodology, information generated, benefits, risks, limitations, and impact on the field of genetic counseling. A statistically significant increase in incorporating information about PGT as a whole from 2008 to 2011 was also reported. The majority of respondents reported that coverage of PGT prepared them for the American Board of Genetic Counseling (ABGC) board exam (80.6 %), to interpret PGT test results (60.2 %) and to identify clinical situations warranting testing (53.1 %). Although the majority of respondents indicated learning about a wide variety of aspects surrounding PGT, many recent graduates indicated their training was less likely to cover aspects essential for the clinical application of PGT. Therefore, genetic counseling programs should place a greater emphasis on these skills, and the development of continuing education opportunities aimed at increasing genetic counselors abilities to interpret and discuss PGT tests and identify clinical situations warranting such testing may be helpful.
A proneural gene controls C. elegans neuroblast asymmetric division and migration
Authors: Zhu Zhiwen , Liu Jianhong , Yi Peishan , Tian Dong , Chai Yongping , Li Wei , Ou Guangshuo
Published: March 2014

Proneural genes control the generation of neuroblasts from the neuroepithelium, but their functions in neuroblast asymmetric division and migration remain elusive. Here, we identified C
aenorhabditis elegans mutants of a proneural transcription factor (TF) lin‐32, in which Q neuroblasts are produced. We showed that LIN‐32 functions in parallel with a storkhead TF, HAM‐1, to regulate Q neuroblast asymmetric division, and that Q neuroblast migration is inhibited in lin‐32 alleles. Consistently, lin‐32 is expressed throughout Q neuroblast lineage, suggesting that LIN‐32 may promote different target gene expression. Our studies thus uncovered previously unknown functions of a proneural gene in neuroblast development.
The amyloid hypothesis, time to move on: Amyloid is the downstream result, not cause, of Alzheimer's disease
Authors: Drachman David A.
Published: March 2014

The “amyloid hypothesis” has dominated Alzheimer research for more than 20 years, and proposes that amyloid is the toxic cause of neural/synaptic damage and dementia. If correct, decreasing the formation or removing amyloid should be therapeutic. Despite discrepancies in the proposed mechanism, and failed clinical trials, amyloid continues to be considered the cause of a degenerative cascade. Alternative hypotheses must explain three features: (i) why amyloid toxicity is not the etiology of Alzheimer's disease (AD), (ii) what alternative mechanisms cause the degeneration and dementia of AD, and (iii) why increased amyloid accumulates in the brain in AD. We propose that AD, which occurs in elderly, already vulnerable brains, with multiple age‐related changes, is precipitated by impaired microvascular function, resulting primarily from decreased Notch‐related angiogenesis. With impaired microvasculature, a lack of vascular endothelial‐derived trophic factors and decreased cerebral blood flow cause the atrophy of neural structures. Therapeutic strategies should focus on supporting normal angiogenesis.
Brain tocopherols related to Alzheimer's disease neuropathology in humans
Authors: Morris Martha Clare , Schneider Julie A. , Li Hong , Tangney Christy C. , Nag Sukriti , Bennett David A. , Honer William G. , Barnes Lisa L.
Published: March 2014

Randomized trials of α‐tocopherol supplements on cognitive decline are negative, whereas studies of dietary tocopherols have shown benefit. We investigated these inconsistencies by analyzing the relations of α‐ and γ‐tocopherol brain concentrations to Alzheimer's disease (AD) neuropathology among 115 deceased participants of the prospective Rush Memory and Aging Project. Associations of amyloid load and neurofibrillary tangle severity with brain tocopherol concentrations were examined in separate adjusted linear regression models. γ‐Tocopherol concentrations were associated with lower amyloid load (β = ‒2.10, P = .002) and lower neurofibrillary tangle severity (β = ‒1.16, P = .02). Concentrations of α‐tocopherol were not associated with AD neuropathology, except as modified by γ‐tocopherol: high α‐tocopherol was associated with higher amyloid load when γ‐tocopherol levels were low and with lower amyloid levels when γ‐tocopherol levels were high (P for interaction = 0.03). Brain concentrations of γ‐ and α‐tocopherols may be associated with AD neuropathology in interrelated, complex ways. Randomized trials should consider the contribution of γ‐tocopherol.
Neural correlates of empathic impairment in the behavioral variant of frontotemporal dementia
Authors: Cerami Chiara , Dodich Alessandra , Canessa Nicola , Crespi Chiara , Marcone Alessandra , Cortese Francesca , Chierchia Gabriele , Scola Elisa , Falini Andrea , Cappa Stefano F.
Published: March 2014

Objective

Loss of empathy is a symptom of the behavioral variant of frontotemporal dementia (bvFTD), constituting a clue for early diagnosis. In this study, we directly compared two empathy components (intention attribution [IA] and emotion attribution [EA]), correlating them with possible specific patterns of gray‐matter density reduction within the mentalizing network.

Methods

We evaluated IA and EA in 18 mild bvFTD patients compared with 36 healthy controls (HCs) using a single nonverbal test. A subgroup entered a voxel‐based morphometry study.

Results

Compared with HC, bvFTD patients showed IA and EA impairments. EA performance correlated with gray‐matter reduction in the right amygdala, left insula, and posterior‐superior temporal sulcus extending into the temporoparietal junction.

Conclusion

We proved an empathic impairment, with the ability to infer emotional states showing the most severe deficit. These results provide further evidence of selective disease‐specific vulnerability of the limbic and frontoinsular network in bvFTD and highlight the usefulness of empathy assessment in early patients.
Synthesis, crystal structure and EPR spectroscopic analysis of novel copper complexes formed from N-pyridyl-4-nitro-1,8-naphthalimide ligands
Authors: Kitchen Jonathan A. , Martinho Paulo N. , Morgan Grace G. , Gunnlaugsson Thorfinnur
Published: March 2014

The synthesis of two new monodentate pyridyl based 4-nitro-1,8-naphthalimide ligands and their corresponding Cu-complexes (using various salts) is described. Of these, complexes 1–3 and 5, all gave rise to structures that were characterised by X-ray crystallography and EPR.
Sequential recognition of zinc ion and hydrogen sulfide by a new quinoline derivative with logic gate behavior
Authors: Dong Zhengping , Le Xuanduong , Zhou Panpan , Dong Chunxu , Ma Jiantai
Published: March 2014

A Schiff base-type fluorescent chemosensor L has been synthesized for Zn2+ detection, and the consequent product of L and Zn2+, L–2Zn, is an excellent indicator for H2S for displacement of Zn2+ from the complex L–2Zn.
Energy transfer from Bi3+ to Ho3+ triggers brilliant single green light emission in LaNbTiO6:Ho3+, Bi3+ phosphors
Authors: Zhang Xingshuang , Zhou Guangjun , Zhou Juan , Zhou Haifeng , Kong Peng , Yu Zhichao , Zhan Jie
Published: March 2014

LaNbTiO6:Ho3+, Bi3+ was synthesized and the remarkably enhance of photoluminescence intensity was ascribed to efficient energy transfer from Bi3+ to Ho3+.
Zeolite nanofiber assemblies as acid catalysts with high activity for the acetalization of carbonyl compounds with alcohols
Authors: Liu Taotao , Fu Wenqian , Zheng Xiang , Jiang Jun , Hu Maolin , Tang Tiandi
Published: March 2014

Acidic zeolite nanofiber assemblies with highly mesoporous structures as catalysts for the formation of a range of acetals in good yields.
Ceria co-doping: synergistic or average effect?
Authors: Burbano Mario , Nadin Sian , Marrocchelli Dario , Salanne Mathieu , Watson Graeme W.
Published: March 2014

High ionic conductivity of the electrolyte is a requisite for cheap, reliable and efficient solid oxide fuel cells. In this study we show that co-doping is not a viable approach to increase the conductivity of state-of-the-art electrolyte material, ceria.
Studying chemical reactivity in a virtual environment
Authors: Haag Moritz P. , Reiher Markus
Published: March 2014

Chemical reactivity of a set of reactants is determined by its potential (electronic) energy (hyper)surface. The high dimensionality of this surface renders it difficult to efficiently explore reactivity in a large reactive system. Exhaustive sampling techniques and search algorithms are not straightforward to employ as it is not clear which explored path will eventually produce the minimum energy path of a reaction passing through a transition structure. Here, the chemist's intuition would be of invaluable help, but it cannot be easily exploited because (1) no intuitive and direct tool for the scientist to manipulate molecular structures is currently available and because (2) quantum chemical calculations are inherently expensive in terms of computational effort. In this work, we elaborate on how the chemist can be reintroduced into the exploratory process within a virtual environment that provides immediate feedback and intuitive tools to manipulate a reactive system. We work out in detail how this immersion should take place. We provide an analysis of modern semi-empirical methods which already today are candidates for the interactive study of chemical reactivity. Implications of manual structure manipulations for their physical meaning and chemical relevance are carefully analysed in order to provide sound theoretical foundations for the interpretation of the interactive reactivity exploration.
A novel tunable Na2Ba6(Si2O7)(SiO4)2:Ce3+,Mn2+ phosphor with excellent thermal stability for white light emitting diodes
Authors: Lv Wenzhen , Jia Yongchao , Zhao Qi , Jiao Mengmeng , Shao Baiqi , Lv Wei , You Hongpeng
Published: March 2014

In this paper, Ce3+ doped and Ce3+,Mn2+ co-doped Na2Ba6(Si2O7)(SiO4)2 phosphors were synthesized via a high temperature solid-state reaction.
Solution to the multi‐machine transient stability problem and simulated validation in realistic scenarios
Authors: Casagrande Daniele , Astolfi Alessandro , Langarica Diego , Ortega Romeo
Published: March 2014

A solution to the problem of transient stabilisation for multi‐machine power systems, with transfer conductances different from zero, is given. The 3n‐dimensional (aggregated) model of the n‐generator system, with lossy transmission lines, non‐linear loads and excitation control, is considered. A non‐linear dynamic state‐feedback control law that ensures, under some conditions on the physical parameters, global asymptotic stability of the operating point is constructed. To the best of the authors’ knowledge only existence results – with the restrictive assumption of uniform inertia generators – are available to date for this problem. Simulation results on the New England benchmark system illustrate the performance of the proposed controller.
Quasi‐bridge‐type fault current limiter for mitigating fault transient phenomena
Authors: Tseng Hsu‐Ting , Chen Jiann‐Fuh
Published: March 2014

This study proposes a quasi‐bridge‐type fault current limiter (QBT‐FCL) for reducing the fault current level and the magnitude of voltage sag. Before a fault occurs, because of the voltage‐compensation effect, the equivalent impedance of the QBT‐FCL is very low, and hence it has almost no influence on the circuit. Therefore, the load seems to directly connect to the voltage source, and there is almost no distortion to the load voltage and current waveforms. When the fault occurs, the limiter automatically inserts the impedance into the circuit, and thus the magnitude of the fault current and voltage sag can be effectively reduced. After the fault is cleared, the limiter starts to freewheel and recovers to the normal operation state. As a result, the QBT‐FCL still has a negligible effect on the circuit and is ready for the next fault occurrence. Theoretical analysis for the proposed QBT‐FCL has been fully developed in this study. Finally, the feasibility and performance of the proposed limiter have been verified by the simulated and experimental results.
Real‐time transient stability assessment based on centre‐of‐inertia estimation from phasor measurement unit records
Authors: Cepeda Jaime C. , Rueda José L. , Colomé Delia G. , Echeverría Diego E.
Published: March 2014

Several smart grid applications have recently been devised in order to timely perform supervisory functions along with self‐healing and adaptive countermeasures based on system‐wide analysis, with the ultimate goal of reducing the risks associated with potentially insecure operating conditions. Real‐time transient stability assessment (TSA) belongs to this type of applications, which allows deciding and coordinating pertinent corrective control actions depending on the evolution of post‐fault rotor‐angle deviations. This study presents a novel approach for carrying out real‐time TSA based on prediction of area‐based centre‐of‐inertia (COI) referred rotor angles from phasor measurement unit (PMU) measurements. Monte Carlo‐based procedures are performed to iteratively evaluate the system transient stability response, considering the operational statistics related to loading condition changes and fault occurrence rates, in order to build a knowledge database for PMU and COI‐referred rotor‐angles as well as to screen those relevant PMU signals that allows ensuring high observability of slow and fast dynamic phenomena. The database is employed for structuring and training an intelligent COI‐referred rotor‐angle regressor based on support vector machines [support vector regressor (SVR)] to be used for real‐time TSA from selected PMUs. Besides, the SVR is optimally tuned by using the swarm variant of the mean‐variance mapping optimisation. The proposal is tested on the IEEE New England 39‐bus system. Results demonstrate the feasibility of the methodology in estimating the COI‐referred rotor angles, which enables alerting about real‐time transient stability threats per system areas, for which a transient stability index is also computed.
Carrier extraction from GaSb quantum rings in GaAs solar cells using direct laser excitation
Authors: James Juanita Saroj , Fujita Hiromi , Carrington Peter J. , Marshall Andrew R.J. , Krier Anthony
Published: March 2014

The authors report on the analysis of the hole escape mechanisms from type‐II GaSb quantum rings (QRs) embedded within the active region of a GaAs single junction solar cell. When the solar cell is excited by using a 1064 nm infrared laser with excitation energy lower than the bandgap of the GaAs matrix, photogenerated electron–hole pairs are created directly within the GaSb QRs. The QR photocurrent exhibits a linear dependence on the excitation intensity over several decades. The thermal activation energy was found to be weakly dependent on the incident light level and increased by only a few meV over several orders of excitation intensity. The magnitude of the relative absorption in the author's QRs when directly probed by using a 1064 nm laser with an incident power density of ∼ 2.6 W cm−2 is found to be ∼ 1.4 × 10−4 per layer. The thermal escape rate of the holes was calculated and found to be ∼ 1011 to 1012 s−1, which is much faster than the radiative recombination rate 109 s−1. This behaviour is promising for concentrator solar cell development and has the potential to increase solar cell efficiency under a strong solar concentration.
Efficient voltage regulation scheme for three‐phase self‐excited induction generator feeding single‐phase load in remote locations
Authors: Gao Sarsing , Bhuvaneswari Gurumoorthy , Murthy Shikaripur S. , Kalla Ujjwal
Published: March 2014

This study presents analysis, design and implementation of a microcontroller based electronic load controller (ELC) for efficient voltage regulation of a three‐phase self‐excited induction generator (SEIG) feeding single‐phase loads in remote locations. The proposed ELC has an uncontrolled rectifier, a filtering capacitor, an insulated gate bipolar transistor switch and a series dump load. The pulse‐width modulation (PWM) pulses with appropriate duty cycle are generated using the dsPIC30F6010 microcontroller. The duty ratio is determined based on the closed‐loop control scheme which decides the amount of power diverted to the dump load. The proposed SEIG–ELC system demonstrates an effective power switching between the main load and the dump load thereby providing an efficient voltage regulation at the machine terminals. The controller is modelled in Matlab/Simulink and the simulated results are validated by experimental results.
Infrared Spectrum, Force Constants, and Thermodynamic Functions of SiF2
Authors: Khanna V. M. , Hauge R. , Curl R. F. , Margrave J. L.
Published: March 2014

The infrared spectrum of gaseous SiF2 has been recorded from 1050 to 400 cm−1. Two bands centered at 872 and 855 cm−1 are, respectively, assigned to the antisymmetric stretching (ν3) and symmetric stretching (ν1) frequencies of the molecule. The symmetric bending frequency (ν2) as determined from the earlier ultraviolet absorption studies lies at 345 cm−1 and could not be observed because this was well below the low-frequency limit of the spectrometer used. The observed vibrational frequencies are combined with the available microwave data to obtain the following values of the quadratic force constants:fr=5.019 mdyn/Å, frr=0.310 mdyn/Å, fα/r2=0.440 mdyn/Å, fαr/r=0.123 mdyn/Å. Two cubic potential constants have been evaluated, K222=−9.5 cm−1 and K122=9.9 cm−1. The average structure of SiF2 in its ground state is computed and found to be 〈r〉=1.5947 Å, 〈α〉=100°53′, where r is the Si–F bond distance and α the F–Si–F angle. A table of thermodynamic functions of SiF2 is presented.
Raman Spectra of Water in Concentrated Ionic Solutions
Authors: Wall Theodore T. , Hornig Donald F.
Published: March 2014

Photoelectric Raman spectra of solutions of the four potassium halides and of Be2+, Mg2+, Cu2+, Zn2+, Sn2+, Al3+, La3+, and Pr3+ chlorides in ordinary water and in 5 mole % deuterated water show, in the region of the water stretching fundamentals, single broad bands similar to those of the pure solvents. Peak frequency shifts between solutions are small, about 1% or of the order of the available resolution, and are insensitive to the cation, except in the ZnCl2 solutions. Intensity and bandwidth changes are large, in the range 20%−100%, but these also correlate with the halide ion in the order F−<H2O<Cl−<Br−<I−. Direct cation effects are absent, even in solutions containing colored Cu2+ and Pr3+ ions near resonance with the 4358-Å exciting light, but in all of the solutions containing polyvalent cations, the molar intensity effect of Cl− is less than it is in KCl. The observed intensities can be related to anion effects when the Raman intensity behavior in solution is interpreted in terms of contribution by both components to the intermediate state of the scattering process, if complex formation is a common occurrence between chloride and polyvalent cations. Despite the strong excited-state interaction underlying intensity behavior, there is no indication that ion—water association leads to the large changes in frequencies or bandwidths of the water stretching fundamentals which are implied by a rigid hydration model of the ion in solution.
CNDO Molecular-Orbital Theory of Molecular Spectra. I. The Virtual-Orbital Approximation to Excited States
Authors: Kroto H. W. , Santry D. P.
Published: March 2014

A semiempirical theory of transition energies and molecular excited-state geometries is developed. The excited-state electronic wavefunction is approximated by a single determinant constructed using a virtual orbital obtained from the minimization of the energy of the ground-state electron configuration. This theory represents a semiquantitative study of the accepted qualitative description of molecular spectra. Results are presented for HNO, HCF, H2CO, H2C2, and NH3. The calculated bond angles, with the exception of H2CO, are in good agreement with experiment, whereas the excitation energies are in general found to be rather too high. In all cases the symmetries of the lowest predicted excited states are found to be consistent with the observed spectra. These results indicate that the qualitative description of the observed transitions of these molecules has a quantitative basis.
Energy Levels of One- and Two-Dimensional Anharmonic Oscillators
Authors: Endres Paul F.
Published: March 2014

The energy levels of the one-dimensional and the linear two-dimensional Morse oscillators have been calculated by the method of Harris, Engerholm, and Gwinn in the harmonic-oscillator representation. The method compares favorably with diagonalization of the exactly calculated Hamiltonian matrix. In the one-dimensional case the calculations can be improved by using displaced basis functions.
Ionization of Atoms by Collision with Excited Atoms. II. A Formula without the Rotating-Atom Approximation
Authors: Watanabe Tsutomu , Katsuura Kanji
Published: March 2014

A formula for the cross section of the ionization of an atom colliding with an excited atom, A*+B→A+B++e, was obtained. The calculations to the formula were restricted to the case where the transition A→A* is optically allowed and the excitation energy of A* exceeds the ionization potential of B as before. Here all degenerate states of A* and B+e were taken into account. The present formula gives a cross section which is 23% smaller than the previous result calculated by the use of the rotating-atom approximation. Besides numerical calculations, an approximation method for the basic equations of the present problem is also shown. This method gives the upper and lower bounds of the approximate cross sections obtainable from the basic equations. Other similar calculations were compared with the present results.
Crystal Structure of Dipotassium Carbonate Trihydrate
Authors: Hunter F. D. , Jeffrey G. A.
Published: March 2014

The crystal structure of 2K2CO3⋅3H2O was determined by a sign-correlation procedure using three-dimensional data and refined by anisotropic least squares. The space group is C2/c with unit cell dimensions a = 11.887, b = 13.827, c = 7.112 Å and β = 120.56°. The structure consists of columns of hydrogen-bonded carbonate ions and water molecules within and between which lie the cations. The first-neighbor oxygen coordination around the cations is eightfold and very distorted. The carbonate ion is planar with 120° angles within experimental error. The C-O distances are 1.266, 1.288, and 1.296 Å. The oxygen of the former is not involved in hydrogen bonding while the oxygens of the latter form two hydrogen bonds at 2.698 and 2.692 Å and one at 2.717 Å to water molecules, respectively.
Effect of Molecular Orientations on Vibrational-Translational Energy Transfer
Authors: Shin Hyung Kyu
Published: March 2014

An evaluation of the steric factor 1/Z0 for molecule-atom and molecule-molecule collisions has been made for the orientation-dependent Morse potential over the temperature range from 300° to 4000 °K. 1/Z0 is found to be of the order of 13 for H2-Ar, 14 for N2-Ar, 15 for O2-Ar, 1/7 for Cl2-Ar, and 19 for I2-Ar at ordinary temperatures. 1/Z0 for molecule-molecule collisions is very small compared to these values; it is of the order of 1/20 for H2-H2, 1/25 for N2-N2, 1/30 for O2-O2, 1/50 for C12-C12, and 1/55 for I2-I2. A moderately important temperature dependence of 1/Z0 is found. In the calculation of 1/Z0 we explicitly considered the importance of attractive forces and used “realistic” exponential range parameters. The temperature dependence of the parameter is discussed, and it is shown that the serious errors might occur in calculating vibrational transition probabilities if the best-fit parameter to experimental data at a particular temperature is used over a wide temperature range (>1000°).
Spin Exchange in Solutions of di-Tertiary-Butyl Nitroxide
Authors: Plachy William , Kivelson Daniel
Published: March 2014

The ESR linewidths of dilute solution of di-tertiary-butyl nitroxide (DTBN) in n-pentane and propane have been studied. Corrections have been made for (1) spin-rotational effects, (2) the variation of concentration with temperature, (3) the line-shape distortion of overlapping “strongly exchanging” lines, (4) the exchange narrowing of inhomogeneous linewidth contributions arising from proton extra hyperfine splitting, and (5) the temperature dependence of the diffusional step length λ. Existing theories of spin exchange appear adequate to explain the low-concentration data; at high concentration it is not possible to make all the corrections discussed above and the comparison of theory and experiment is not meaningful. In n-pentane we found that (zT/z).Jλ02 = 5×1012 Å2 sec−1 and JzT = 4.9×1011 sec−1, where J is minus two times the exchange integral, λ0 is the diffusional step length at the freezing point, zT is the mean total number of molecular nearest neighbors, and z is the number of new radical nearest neighbors encountered in each jump. The results for DTBN in propane are similar.
Triplet-Triplet Absorption Studies on Aromatic and Heterocyclic Molecules at 77 °K
Authors: Henry Bryan R. , Kasha Michael
Published: March 2014

Triplet-triplet absorption spectroscopy has been extended both to numerous new molecules of current spectroscopic interest and to lower energy spectral regions (to 10 000 cm−1) of previously investigated molecules. Measurements have been carried out by the method of steady cross illumination using a modified Cary 14 spectrophotometer.

Eight new T-T transitions have been found in the present research. New lower energy bands have been studied in the previously studied molecules triphenylene, phenanthrene, and phenanthrene-D10; in the latter two molecules, an evaluation was made of the absorption coefficient (ε = 675), which has established the forbidden character of the observed bands. A tentative assignment as 3Lb←3La of the new triplet-triplet transition at 12 075 cm−1 in phenanthrene has been made from theoretical considerations. Some absorptions found previously in the literature for phenanthrene and fluorene have been questioned. Triplet-triplet absorption has been verified in diphenylamine by lifetime measurements, thus resolving an earlier uncertainty, and a similar band has been discovered in triphenylamine.

Because of the relatively small attention that had been given previously to triplet-triplet absorption in heterocyclic molecules, many such molecules have been investigated and new transitions have been discovered in several, including quinoxaline, phenoxazine, phenothiazine, and carbazole. The related photochemistry of phenoxazine and phenothiazine has also been studied briefly.
Theoretical Isotherms for Adsorption on a Square Lattice
Authors: Tonks Lewi
Published: March 2014

A method which is not self-consistent has been used by J. K. Roberts to calculate the adsorption isotherm of adatoms, which are larger than the spacing of the adsorption sites on the substrate so that each adatom excludes all others from neighboring sites. It consists in completely formulating the internal statistics of a sample of the film surface and allowing for the effect of the rest of the film by introducing one or more “environmental” parameters as undetermined functions. These are determined by the requirement that each site of the sample shall be an average site. The failure of this method is traceable to the fact that these functions, when determined, are found to vary with surface concentration in a manner inconsistent with the physical requirements. The same difficulty is found to be latent in Peierls’ treatment of adsorption with interaction between adatoms and in Bethe’s treatment of superlattices. The adsorption isotherms for two cases with no interaction between neighbor adatoms are here calculated by another method. The one case is that of Roberts, the other that in which 9 sites are excluded by each adatom. The method requires separate treatment of dilute (small θ) and concentrated (θ nearly unity) films. At each extreme it involves successive approximations. For the dilute film’ the number of free sites is determined as a function of the number of adatoms by enumerating the number of ways that adatoms occur (1) without overlapping of exclusion patterns, (2) with the exclusion patterns of only two adatoms overlapping, etc. This yields the adsorption isotherm. For the concentrated film, the interactions of the free sites themselves are treated in an analogous but necessarily somewhat different manner to give the adsorption isotherm near θ = 1. Some fairing of the relations to bridge the intermediate values of θ is necessary. The results are: for the 5-site exclusion pattern θ = 2Ap[1−(5/2)θ+(3/2)θ2+3/4θ3], 0≦θ≦0.5 θ = Ap[1−θ−3(1−θ)3+5(1−θ)4], 0.5≦θ≦1 and for the 9-site exclusion pattern θ = 4AP[1−(9/4)θ+θ2], θ near zero θ = 2Ap(1−θ)2, θ near unity. These cases are compared with the limiting cases, first the 1-site exclusion pattern and second the infinity-site pattern which is the same case as adsorption on a siteless surface.
Ab initio investigation of the first hydration shell of protonated glycine
Authors: Wei Zhichao , Chen Dong , Zhao Huiling , Li Yinli , Zhu Jichun , Liu Bo
Published: March 2014

The first hydration shell of the protonated glycine is built up using Monte Carlo multiple minimum conformational search analysis with the MMFFs force field. The potential energy surfaces of the protonated glycine and its hydration complexes with up to eight water molecules have been scanned and the energy-minimized structures are predicted using the ab initio calculations. First, three favorable structures of protonated glycine were determined, and the micro-hydration processes showed that water can significantly stabilize the unstable conformers, and then their first hydration shells were established. Finally, we found that seven water molecules are required to fully hydrate the first hydration shell for the most stable conformer of protonated glycine. In order to analyse the hydration process, the dominant hydration sites located around the ammonium and carboxyl groups are studied carefully and systemically. The results indicate that, water molecules hydrate the protonated glycine in an alternative dynamic hydration process which is driven by the competition between different hydration sites. The first three water molecules are strongly attached by the ammonium group, while only the fourth water molecule is attached by the carboxyl group in the ultimate first hydration shell of the protonated glycine. In addition, the first hydration shell model has predicted most identical structures and a reasonable accord in hydration energy and vibrational frequencies of the most stable conformer with the conductor-like polarizable continuum model.
A 70 kV solid-state high voltage pulse generator based on saturable pulse transformer
Authors: Fan Xuliang , Liu Jinliang
Published: March 2014

High voltage pulse generators are widely applied in many fields. In recent years, solid-state and operating at repetitive mode are the most important developing trends of high voltage pulse generators. A solid-state high voltage pulse generator based on saturable pulse transformer is proposed in this paper. The proposed generator is consisted of three parts. They are charging system, triggering system, and the major loop. Saturable pulse transformer is the key component of the whole generator, which acts as a step-up transformer and main switch during working process of this generator. The circuit and working principles of the proposed pulse generator are introduced first in this paper, and the saturable pulse transformer used in this generator is introduced in detail. Circuit of the major loop is simulated to verify the design of the system. Demonstration experiments are carried out, and the results show that when the primary energy storage capacitor is charged to a high voltage, such as 2.5 kV, a voltage with amplitude of 86 kV can be achieved on the secondary winding. The magnetic core of saturable pulse transformer is saturated deeply and the saturable inductance of the secondary windings is very small. The switch function of the saturable pulse transformer can be realized ideally. Therefore, a 71 kV output voltage pulse is formed on the load. Moreover, the magnetic core of the saturable pulse transformer can be reset automatically.
Ionization energy shift of characteristic K x-ray lines from high-Z materials for plasma diagnostics
Authors: Słabkowska K. , Szymańska E. , Polasik M. , Pereira N. R. , Rzadkiewicz J. , Seely J. F. , Weber B. V. , Schumer J. W.
Published: March 2014

The energy of the characteristic x-rays emitted by high atomic number atoms in a plasma that contains energetic electrons depends on the atom's ionization. For tungsten, the ionization energy shift of the L-lines has recently been used to diagnose the plasma's ionization; the change in energy of a K-line has been measured for iridium and observed for ytterbium. Here, we present detailed computations of the ionization energy shift to K-lines of these and an additional element, dysprosium; for these atoms, some K-lines nearly coincide in energy with K-edges of slightly lower Z atoms so that a change in transmission behind a K-edge filter betrays a change in energy. The ionization energy shift of such high-energy K-lines may enable a unique diagnostic when the plasma is inside an otherwise opaque enclosure such as hohlraums used on the National Ignition Facility.
Study of instability formation and EUV emission in thin liners driven with a compact 250 kA, 150 ns linear transformer driver
Authors: Valenzuela J. C. , Collins G. W. , Mariscal D. , Wyndham E. S. , Beg F. N.
Published: March 2014

A compact linear transformer driver, capable of producing 250 kA in 150 ns, was used to study instability formation on the surface of thin liners. In the experiments, two different materials, Cu and Ni, were used to study the effect of the liner's resistivity on formation and evolution of the instabilities. The dimensions of the liners used were 7 mm height, 1 mm radius, and 3 μm thickness. Laser probing and time resolved extreme ultraviolet (EUV) imaging were implemented to diagnose instability formation and growth. Time-integrated EUV spectroscopy was used to study plasma temperature and density. A constant expansion rate for the liners was observed, with similar values for both materials. Noticeable differences were found between the Cu and Ni instability growth rates. The most significant perturbation in Cu rapidly grows and saturates reaching a limiting wavelength of the order of the liner radius, while the most significant wavelength in Ni increases slowly before saturating, also at a wavelength close to the liner radius. Evidence suggests that the instability observed is the well-known m = 0 MHD instability. However, upon comparing the instability evolution of Cu and Ni, the importance of the resistivity on the seeding mechanism becomes evident. A comparison of end-on and side-on EUV emission possible indicates the formation of precursor plasma, where it has been estimated using EUV spectroscopy that the precursor plasma temperature is approximately 40 eV with ion density of order 1019 cm−3, for both materials.
Absorption spectroscopy of a laboratory photoionized plasma experiment at Z
Authors: Hall I. M. , Durmaz T. , Mancini R. C. , Bailey J. E. , Rochau G. A. , Golovkin I. E. , MacFarlane J. J.
Published: March 2014

The Z facility at the Sandia National Laboratories is the most energetic terrestrial source of X-rays and provides an opportunity to produce photoionized plasmas in a relatively well characterised radiation environment. We use detailed atomic-kinetic and spectral simulations to analyze the absorption spectra of a photoionized neon plasma driven by the x-ray flux from a z-pinch. The broadband x-ray flux both photoionizes and backlights the plasma. In particular, we focus on extracting the charge state distribution of the plasma and the characteristics of the radiation field driving the plasma in order to estimate the ionisation parameter.
Kα and bremsstrahlung x-ray radiation backlighter sources from short pulse laser driven silver targets as a function of laser pre-pulse energy
Authors: Jarrott L. C. , Kemp A. J. , Divol L. , Mariscal D. , Westover B. , McGuffey C. , Beg F. N. , Suggit M. , Chen C. , Hey D. , Maddox B. , Hawreliak J. , Park H.-S. , Remington B. , Wei M. S. , MacPhee A.
Published: March 2014

Measurements of silver K-shell and bremsstrahlung emission from thin-foil laser targets as a function of laser prepulse energy are presented. The silver targets were chosen as a potential 22 keV backlighter source for the National Ignition Facility Experiments. The targets were irradiated by the Titan laser with an intensity of 8 × 1017 W/cm2 with 40 ps pulse length. A secondary nanosecond timescale laser pulse with controlled, variable energy was used to emulate the laser prepulse. Results show a decrease in both Kα and bremsstrahlung yield with increasing artificial prepulse. Radiation hydrodynamic modeling of the prepulse interaction determined that the preplasma and intact target fraction were different in the three prepulse energies investigated. Interaction of the short pulse laser with the resulting preplasma and target was then modeled using a particle-in-cell code PSC which explained the experimental results. The relevance of this work to future Advanced Radiographic Capability laser x-ray backlighter sources is discussed.
X-ray laser driven gold targets
Authors: Petrova Tz. B. , Whitney K. G. , Davis J.
Published: March 2014

The femtosecond population dynamics of gold irradiated by a coherent high-intensity (>1017 W/cm2) x-ray laser pulse is investigated theoretically. There are two aspects to the assembled model. One is the construction of a detailed model of platinum-like gold inclusive of all inner-shell states that are created by photoionization of atomic gold and decay either by radiative or Auger processes. Second is the computation of the population dynamics that ensues when an x-ray pulse is absorbed in gold. The hole state generation depends on the intensity and wavelength of the driving x-ray pulse. The excited state populations reached during a few femtosecond timescales are high enough to generate population inversions, whose gain coefficients are calculated. These amplified lines in the emitted x-ray spectrum provide important diagnostics of the radiation dynamics and also suggest a nonlinear way to increase the frequency of the coherent output x-ray pulses relative to the frequency of the driver input x-ray pulse.
Interplay of Cu and oxygen vacancy in optical transitions and screening of excitons in ZnO:Cu films
Authors: Darma Yudi , Seng Herng Tun , Marlina Resti , Fauziah Resti , Ding Jun , Rusydi Andrivo
Published: March 2014

We study room temperature optics and electronic structures of ZnO:Cu films as a function of Cu concentration using a combination of spectroscopic ellipsometry, photoluminescence, and ultraviolet-visible absorption spectroscopy. Mid-gap optical states, interband transitions, and excitons are observed and distinguishable. We argue that the mid-gap states are originated from interactions of Cu and oxygen vacancy (Vo). They are located below conduction band (Zn4s) and above valence band (O2p) promoting strong green emission and narrowing optical band gap. Excitonic states are screened and its intensities decrease upon Cu doping. Our results show the importance of Cu and Vo driving the electronic structures and optical transitions in ZnO:Cu films.
Monomer-dimer problem on random planar honeycomb lattice
Authors: Ren Haizhen , Zhang Fuji , Qian Jianguo
Published: March 2014

We consider the monomer-dimer (MD) problem on a random planar honeycomb lattice model, namely, the random multiple chain. This is a lattice system with non-periodic boundary condition, whose generating process is inspired by the growth of single walled zigzag carbon nanotubes. By applying algebraic and combinatorial techniques we establish a calculating expression of the MD partition function for bipartite graphs, which corresponds to the permanent of a matrix. Further, by using the transfer matrix argument we show that the computing problem of the permanent of high order matrix can be converted into some lower order matrices for this family of lattices, based on which we derive an explicit recurrence formula for evaluating the MD partition function of multiple chains and random multiple chains. Finally, we analyze the expectation of the number of monomer-dimer arrangements on a random multiple chain and the asymptotic behavior of the annealed MD entropy when the multiple chain becomes infinite in width and length, respectively.
Vibrational quasi-degenerate perturbation theory with optimized coordinates: Applications to ethylene and trans-1,3-butadiene
Authors: Yagi Kiyoshi , Otaki Hiroki
Published: March 2014

A perturbative extension to optimized coordinate vibrational self-consistent field (oc-VSCF) is proposed based on the quasi-degenerate perturbation theory (QDPT). A scheme to construct the degenerate space (P space) is developed, which incorporates degenerate configurations and alleviates the divergence of perturbative expansion due to localized coordinates in oc-VSCF (e.g., local O–H stretching modes of water). An efficient configuration selection scheme is also implemented, which screens out the Hamiltonian matrix element between the P space configuration (p) and the complementary Q space configuration (q) based on a difference in their quantum numbers (λpq = ∑s|ps − qs|). It is demonstrated that the second-order vibrational QDPT based on optimized coordinates (oc-VQDPT2) smoothly converges with respect to the order of the mode coupling, and outperforms the conventional one based on normal coordinates. Furthermore, an improved, fast algorithm is developed for optimizing the coordinates. First, the minimization of the VSCF energy is conducted in a restricted parameter space, in which only a portion of pairs of coordinates is selectively transformed. A rational index is devised for this purpose, which identifies the important coordinate pairs to mix from others that may remain unchanged based on the magnitude of harmonic coupling induced by the transformation. Second, a cubic force field (CFF) is employed in place of a quartic force field, which bypasses intensive procedures that arise due to the presence of the fourth-order force constants. It is found that oc-VSCF based on CFF together with the pair selection scheme yields the coordinates similar in character to the conventional ones such that the final vibrational energy is affected very little while gaining an order of magnitude acceleration. The proposed method is applied to ethylene and trans-1,3-butadiene. An accurate, multi-resolution potential, which combines the MP2 and coupled-cluster with singles, doubles, and perturbative triples level of electronic structure theory, is generated and employed in the oc-VQDPT2 calculation to obtain the fundamental tones as well as selected overtones/combination tones coupled to the fundamentals through the Fermi resonance. The calculated frequencies of ethylene and trans-1,3-butadiene are found to be in excellent agreement with the experimental values with a mean absolute error of 8 and 9 cm−1, respectively.
Construction of a parameter-free doubly hybrid density functional from adiabatic connection
Authors: Su Neil Qiang , Xu Xin
Published: March 2014

In this work, the adiabatic connection (AC) formalism, coordinate scaling relations, and the second order Görling-Levy perturbation theory (GL2) are first reviewed. Emphasis is laid upon the construction of the AC integrand ($W_{xc}^\lambda$Wxcλ), with suitable input data $\{ {W_{xc}^{0},W^{\prime 0} _{xc},W_{xc}^1 } \}${Wxc0,Wxc′0,Wxc1} and the proper asymptotic behavior on λ−1/2 as λ → ∞. This leads to a non-empirical DH functional, namely, PBE-ACDH. The PBE-ACDH functional is unique in that it explicitly considers contributions from density scaling and singles, and it utilizes density and orbital information from the PBE functional, which has a local multiplicative potential, being most compatible with the GL2 theory. Systematical tests on heats of formation, bond dissociation enthalpies, reaction barrier heights, and nonbonded interactions, using some well-established benchmarking sets, suggest that PBE-ACDH is a significant improvement over its parent functional PBE, as well as PBE0, Becke's Half-and-Half (PBE-HH), and GL2. The physical insight gained in the present work should prove useful for the further development of new functionals.