bluuebunny/crossref_metadata_2025 huggingface dataset:
Anthradithiophene–thiophene copolymers with broad UV–vis absorption for organic solar cells and field‐effect transistors
Authors: Kong Hoyoul , Heum Park Sung , Cho Nam Sung , Cho Shinuk , Shim Hong‐Ku
Published: June 2012

New semiconducting copolymers, poly((TIPS‐ADT)‐(4,4′‐didodecyl‐2,2′‐bithiophene)) (PTADT2) and poly((TIPS‐ADT)‐(2,2′‐(4,4′‐didodecyl‐2,2′‐bithiophene)dithiophene)) (PTADT4), produced by incorporating 5,11‐bis(triisopropylsilylethynyl) anthra[2,3‐b:7,6‐b']dithiophene (TIPS‐ADT) and alkyl‐thiophene derivatives were synthesized via Stille coupling polymerization. The optical, electrochemical, structural, field‐effect transistor, and solar cell properties of the polymers were investigated. The polymers showed good solubility at room temperature in common organic solvents due to their abundant side groups including TIPS and dodecyl side chains. Both polymers showed very broad UV absorption spectra covering the spectral range from 300 to 750 nm as a result of the combination of the different absorption ranges of the TIPS‐ADT unit (short wavelength region) and thiophene derivatives (long wavelength region). The FET device fabricated using PTADT4 containing additional unsubstituted thiophene rings as a spacer between TIPS‐ADT and thiophene derivatives showed a higher hole mobility (5.7 × 10−4 cm2/V s) than the PTADT2 device (2.8 × 10−5 cm2/V s), due to the improved intermolecular ordering caused by the reduced steric hindrance between bulky side chain groups. In addition, the PTADT4:(6,6)‐phenyl‐C70‐butyric acid methyl ester (PC70BM) device showed an enhanced power conversion efficiency (PCE) of 1.30% compared with the PTADT2:PC70BM device (PCE of 0.55%) under AM 1.5G irradiation (100 mW/cm2). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Microwave‐Assisted Synthesis of 1‐Methyl‐2,4,5‐trinitroimidazole
Authors: Ravi Pasupala , Tewari Surya P.
Published: June 2012

The synthesis of 1‐methyl‐2,4,5‐trinitroimidazole (6) in good yields starting from imidazole (1) via nitrodeiodination under microwave irradiation is reported herein. The synthesized compounds were characterized by IR and NMR spectroscopy, mass spectrometry, and CHN analyses.
Preparation of Fe/Al Composites with Enhanced Thermal Properties by Chemical Liquid Deposition Methods
Authors: Du Rong , Hu Mulin , Xie Changsheng , Zeng Dawen
Published: June 2012

Core‐shell Fe/Al composites were successfully prepared by chemical liquid deposition with iron carbonyl [Fe(CO)5] as precursor and kerosine as oil phase medium. Scanning electron microscopy (SEM), X‐ray diffractometer (XRD), and simultaneous thermogravimetry‐differential thermal analysis (TG‐DTA) were employed to characterize the samples and assess their thermal properties. The results indicated that the aluminum core was coated compactly by an iron layer and the the oxidation kinetics of the obtained composite powders showed a significant improvement compared to pure aluminum powders. The thermal reactivity of Fe/Al composites with oxygen is obviously higher than those of pure aluminum powders, which means that after coating much more heat can be released in the same temperature range and the heat release happens faster and more concentrated. On the basis of the results, a possible formation of the coating is proposed and a thermal reaction mechanism is also discussed.
A New Approach to the Application of Molecular Surface Electrostatic Potential in the Study of Detonation
Authors: Zeman Svatopluk , Friedl Zdeněk
Published: June 2012

In a sample of 22 nitramines, the simplest features of surface electrostatic potentials (SEPs), their positive (VS,max) and negative (VS,min) extremes, are related to their detonation velocities, D, at maximal theoretical densities. The relationships between the VS,min and D values logically show the nitramino group as responsible for detonation initiation for these compounds. On the other hand, the VS,max values gave complicated relationships. As a criterion of the imbalance between the VS,max and VS,min extremes their sum was derived and used as a new simple characteristic of SEPs, VS,Σ. The VS,Σ values have close relationships with the D values and the corresponding relationships uniquely determine the nitramino grouping as a reactivity center for detonation of nitramines. This new criterion is shown to be the best SEP characteristic for the study of detonation initiation. In all the relationships mentioned in this study of nitramines, the increase in potentials and/or their sum correspond with an increase in the D values (energy content of molecules).
Study on Ultrasound‐ and Spray‐Assisted Precipitation of CL‐20
Authors: Wang Jingyu , Li Junlong , An Chongwei , Hou Conghua , Xu Wenzheng , Li Xiaodong
Published: June 2012

Ultrafine hexanitrohexaazaisowurtzitane (CL‐20) samples were prepared by a ultrasound‐ and spray‐assisted precipitation method. Raw CL‐20 and ultrafine CL‐20 samples were characterized by SEM, FT‐IR spectroscopy, XRD, and particle size analysis. The impact sensitivity and thermal stability of two CL‐20 samples were also tested and compared. The results indicate that by this recrystallization process, the mean particle size of CL‐20 is 470 nm, and the particle size distribution was in the range from 400–700 nm. The particle morphology is nearly spheric with a smooth surface. Compared with raw CL‐20, the impact sensitivity of the ultrafine sample is significantely reduced and the drop height (H50) is increased from 12.8 to 37.9 cm. The critical explosion temperature of ultrafine CL‐20 decreased from 235.6 to 229.0 °C, which suggests that the thermal stability of ultrafine CL‐20 is lower than that of raw CL‐20.
Thermal and Combustion Properties of 3,4‐Bis(3‐nitrofurazan‐4‐yl)furoxan (DNTF)
Authors: Sinditskii Valery P. , Burzhava Anna V. , Sheremetev Aleksey B. , Aleksandrova Natalia S.
Published: June 2012

Thermal decomposition of melted 3,4‐bis(3‐nitrofurazan‐4‐yl)furoxan (DNTF) in isothermal conditions was studied. The burning rates of DNTF were measured in the pressure interval of 0.1–15 MPa. The thermal stability of DNTF was found to be close to the stability of HMX, while the burning rate of DNTF was close to the burning rate of CL‐20. The thermocouple measurements in the combustion wave of DNTF showed that combustion of DNTF was controlled by the gas‐phase mechanism. The DNTF vapor pressure was determined from thermocouple measurements and agreed well with data obtained at low temperatures under isothermal conditions.
Computer Simulation of Decomposition Mechanisms for CL‐20, Hydrazine, and Their Binary System
Authors: Pivina Tatyana , Korolev Vyacheslav , Khakimov Dmitriy , Petukhova Tatyana , Ivshin Victor , Lempert David
Published: June 2012

An approach to simulate thermal destruction processes of energetic materials has been developed. It is based on the classification of structural features for nitro compounds and the experimental data regarding their decomposition mechanisms. This approach consists of the mathematical simulation of thermal decomposition mechanisms to predict the likely reactions that may occur during the destruction of organic compounds. On the basis of contemporary experimental data on the decomposition of energetic materials from various chemical classes, a set of semi‐empirical rules for modeling possible reaction pathways has been formulated. These rules allow the generation of a whole set of possible decomposition mechanisms for substances at different steps of their destruction. In this study, the suggested methodology is applied to 2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane (CL‐20) and hydrazine and to their binary energetic mixture. It has been shown that thermal decomposition of the binary system consists in decompositions of the separate compounds at the initial stage with subsequent collisions and interactions of the resultant intermediates and decomposition products at different stages. In addition to some experimentally found decomposition products, our simulation showed some other possible compounds among the final products.
Synthesis and Characterization of 1‐Nitroguanyl‐3‐nitro‐5‐amino‐1,2,4‐triazole
Authors: Chavez David E. , Parrish Damon A.
Published: June 2012

The synthesis of 1‐nitroguanyl‐3‐nitro‐5‐amino‐1,2,4‐triazole (ANTA‐NQ) (1) with good yield and high purity is described. DSC analysis showed that the material displays good thermal stability. An X‐ray crystallographic analysis confirms the structure of this material, as well as displays intramolecular hydrogen bonding. A gas pycnometry density for this material was measured to be 1.79 g cm−3. The heat of formation of this material was also measured. These data, along with the molecular formula were used as inputs to calculate the detonation velocity and detonation pressure using the Cheetah thermochemical code. The sensitivity of this material towards impact, spark and friction was also measured, as well as its vacuum thermal stability. The 3‐azido derivative 2 was also prepared and its properties are described as well. The above data show that (ANTA‐NQ) may be a high performing material with low sensitivity and good thermal stability.
Primary androgen deprivation (AD) followed by active surveillance (AS) for newly diagnosed prostate cancer (PC): A retrospective study
Authors: Scholz Mark C. , Groom Meg K. , Kaddis Andrew J. , Strum Stephen B. , Jennrich Robert I. , Bahn Duke K. , Chang Patricia J. , Becker Lauren K. , Lam Richard Y.
Published: July 2012

BACKGROUND

Active surveillance (AS) is only recommended for Low‐Risk prostate cancer (PC) with <34% biopsies positive. Studies describing the long‐term outcome of men treated with androgen deprivation (AD) followed by AS are sparse.

MATERIALS AND METHODS

One hundred two men were treated with 12 months of AD in a medical oncology clinic specializing in PC between 1998 and 2007 and were followed for a median of 7.25 years. The biopsy complete response rate after AD and the incidence of disease progression while on subsequent AS was assessed. Baseline age, D'Amico risk category, PSA velocity, percentage core biopsies, and prostate volume were evaluated as potential predictors of disease progression.

RESULTS

D'Amico risk category for the 102 men: Low: n = 22, Intermediate: n = 30, and High: n = 50. Medians: Age 67.3, PSA 7.8, Gleason 3 + 4, >50% core biopsies positive, stage T1c. Seventy men had a clear biopsy and 31 of these had disease progression leading to additional treatment after a median of 52 months. D'Amico risk category of the 57 men with a positive biopsy after AD or disease progression on AS was: Low: n = 4 (18%), Intermediate: n = 16 (53%), and High: n = 37 (74%). No PC deaths occurred. Three men had clinical progression. In stepwise logistic regression analysis only higher D'Amico risk category and lower prostate volume predicted disease progression.

CONCLUSIONS

Despite a high prevalence of ≥50% core biopsies positive at baseline, AD induces durable remissions in most men with Low‐Risk and about half with Intermediate‐Risk PC. Prostate 73: 83–88, 2013. © 2012 Wiley Periodicals, Inc.
MBE growth and design of II–VI heterostructures for epitaxial lift‐off
Authors: Davidson Ian A. , Moug Richard T. , Vallance Erin C. , Tamargo Maria C. , Prior Kevin A.
Published: June 2012

Epitaxial lift‐off (ELO) is a post‐growth process that allows the active part of a semiconductor structure to be transferred from its growth substrate to a new one. This is a well established technique for III–V semiconductors, and has previously been demonstrated for ZnSe‐based alloys grown on GaAs using a metastable MgS sacrificial layer, taking advantage of the huge difference in etch rates of MgS and ZnSe.

We report here the first successful extension of this process to II–VI layers grown on InP by using a MgSe sacrificial layer. By using the correct etching conditions, MgSe has been found to work effectively as a sacrificial layer. 5 × 5 mm2 square pieces of material can be lifted and deposited on glass substrates without any deterioration in the structural or optical properties; as confirmed by optical microscopy and photoluminescence (PL) measurements.
Mechanical energy losses in plastically deformed and electron plus neutron irradiated high purity single crystalline molybdenum at elevated temperatures
Authors: Zelada Griselda I. , Lambri Osvaldo Agustin , Bozzano Patricia B. , García José Angel
Published: June 2012

Mechanical spectroscopy (MS) and transmission electron microscopy (TEM) studies have been performed in plastically deformed and electron plus neutron irradiated high purity single crystalline molybdenum, oriented for single slip, in order to study the dislocation dynamics in the temperature range within one third of the melting temperature. A damping peak related to the interaction of dislocation lines with both prismatic loops and tangles of dislocations was found. The peak temperature ranges between 900 and 1050 K, for an oscillating frequency of about 1 Hz.
The effect of synthesis parameters on transport properties of nanostructured bulk thermoelectric p‐type silicon germanium alloy
Authors: Zamanipour Zahra , Shi Xinghua , Dehkordi Arash M. , Krasinski Jerzy S. , Vashaee Daryoosh
Published: June 2012

Nanostructured silicon germanium thermoelectric materials prepared by mechanical alloying and sintering method have recently shown large enhancement in figure‐of‐merit, ZT. The fabrication of these structures often involves many parameters whose understanding and precise control is required to attain large ZT. In order to find the optimum parameters for further enhancing the ZT of this material, we have grown and studied both experimentally and theoretically different nanostructured p‐type SiGe alloys. The effect of various parameters of milling process and sintering conditions on the thermoelectric properties of the grown samples were studied. The electrical and thermal properties were calculated using Boltzmann transport equation and were compared with the data of nanostructured and crystalline SiGe. It was found that the thermal conductivity not only depends on the average crystallite size in the bulk material, but also it is a strong function of alloying, porosity, and doping concentration. The Seebeck coefficient showed weak dependency on average crystallite size. The electrical conductivity changed strongly with synthesis parameters. Therefore, depending on the synthesis parameters the figure‐of‐merit reduced or increased by ∼60% compared with that of the crystalline SiGe. The model calculation showed that the lattice part of thermal conductivity in the nanostructured sample makes ∼80% of the total thermal conductivity. In addition, the model calculation showed that while the room temperature hole mean free path (MFP) in the nanostructured sample is dominated by the crystallite boundary scattering, at high temperature the MFP is dominated by acoustic phonon scattering. Therefore, the thermal conductivity can be further reduced by smaller crystallite size without significantly affecting the electrical conductivity in order to further enhance ZT.
Effects of substrate temperature upon optical properties of ZnTe epilayers grown on (100) GaAs substrates by MOVPE
Authors: Huang Shulai , Ji Ziwu , Zhao Mingwen , Zhang Lei , Guo Hongyu , Liu Baoli , Xu Xiangang , Guo Qixin
Published: June 2012

The photoluminescence (PL) properties of the ZnTe epilayers grown on (100) GaAs substrates with various substrate temperatures have been investigated. It has been demonstrated that the PL spectra depend strongly on the substrate temperature. A too low (390 °C) or too high (440 °C) substrate temperature deteriorates the epilayer quality due to the formation of defects or/and to the inclusion of impurities. A moderate substrate temperature (around 420 °C) is suitable to obtain a high‐quality epilayer with the narrow spectral width and strong emission intensity. This is attributed to the moderate substrate temperature improving the crystallinity of the ZnTe epilayer by enhancing recrystallization of the adsorbed precursors.
Understanding and morphology control of pore modulations in nanoporous anodic alumina by discontinuous anodization
Authors: Santos Abel , Vojkuvka Lukas , Alba María , Balderrama Victor S. , Ferré‐Borrull Josep , Pallarès Josep , Marsal Lluís F.
Published: June 2012

Here, we report on an electrochemical approach so‐called discontinuous anodization (DA) for controlling the generation of pore modulations in nanoporous anodic alumina (NAA) under self‐ordering conditions. In this method, the anodization of aluminium is performed by voltage pulses under mild anodization regime and thermal‐acidic conditions. Furthermore, we perform an exhaustive and systematic study about the relationship between the pore modulation morphology and the main anodization parameters (i.e. acid electrolyte temperature and relax time between consecutive voltage pulses). The generation mechanism of the pore modulations is associated with the formation of a gel‐like layer under these thermal‐acidic conditions and its subsequent detachment during the beginning of each voltage pulse. All this makes it possible to control the pore modulation morphology in NAA at will, what is crucial for developing new nanostructures with accurately controlled geometry for such purposes as nanofluidics, magnetic nanostructures, optical biosensors, templates, selective molecular separators and so forth.

magnified image

A three‐dimensional network based on NAA with controlled geometry: The DA by voltage pulses under hydrothermal conditions yields an accurate control over the pore modulation morphology. Therefore, the structure of the resulting 3D‐NAA network can be designed at will for later applications.
Carbon‐nanotube‐based flexible devices using a mechanical transfer method
Authors: Lee Kyongsoo , Ju Byeong‐Kwon
Published: June 2012

We describe a new method for the manufacture of single‐walled carbon nanotube (SWCNT)‐based electrical devices on flexible substrates. The method involves the deposition of a SWCNT films onto polydimethylsiloxane (PDMS) substrates from rigid substrates using the adhesive property of PDMS. This method is similar to the conventional dry transfer method, which is based on surface‐energy modification, except that our method involves mechanical transfer using the adhesive property of PDMS under peculiar conditions. The gas‐sensing characteristics of the resulting transferred SWCNT films are presented, showing, for example, that typical flexible sensors exhibit a sensitivity of 17.4% for 4‐ppm NO2 in a vacuum at room temperature. The performances of the devices are slightly reduced when they are bent to a curved profile with a bending radius of 2 cm (15.9%). The field‐emission properties are also investigated. From these emitters, the SWCNTs can be turned on with a field as low as 0.9 V/µm, and an emission current density of 0.75 mA/cm2 at 1.2 V/µm can be attained. Thus, a method for the fabrication of flexible devices is established, which should find practical applications in electronic devices.
Correlation Study Using Scuffing Damage to Investigate Improved Simulation Techniques for Packaging Vibration Testing
Authors: Griffiths K. , Shires D. , White W. , Keogh P. S. , Hicks B. J.
Published: July 2012

Vibration testing of packaging is a critical part of the distribution packaging analysis process. The accuracy of simulated vibration is important for packaging optimization. Because of this, several researchers have developed improved simulation methods to produce more realistic vibration tests. Correlation studies are required to verify these methods, ideally using actual packaged products in transit. Unfortunately, cost, time and complexity issues make carrying out studies with actual product difficult.

This article uses a specially designed and proven test rig, which simulates the damage mechanism of scuffing, to carry out a correlation study. The study compares the level of damage produced when performing simulations using a range of improved techniques in comparison with the time‐history reproduction of a journey (used as a benchmark) and the established method using the average power density spectrum to create a Gaussian simulation signal.

The level of scuffing damage produced varied between the different simulation methods, with the modulated root mean square (RMS) technique and the accelerated power density spectrum (with a time compression of 5 and a k equal to 2) best reproducing the level of damage observed from the benchmark time replication test. Copyright © 2012 John Wiley & Sons, Ltd.
Longitudinal localization of tropical intraseasonal variability
Authors: Sukhatme Jai
Published: June 2012

Intraseasonal time‐scales play an important role in tropical variability. Two modes that contribute significantly to tropical intraseasonal variability (ISV) are the eastward‐propagating Madden–Julian Oscillation (MJO), and westward‐moving moist equatorial Rossby waves. This note reports on a correspondence between the longitudinal gradient of mean tropical precipitable water (PW), and the geographical regions of genesis, and convective activity, of both these large‐scale tropical systems. Our finding is based on an analysis of PW from the MERRA reanalysis product. The data indicate that the mean tropical PW has a dominant wavenumber two (three) structure in longitude in the Northern (Southern) Hemisphere. Departures from a longitudinally homogeneous state are attributed to the influence of subtropical anticyclones, and are accentuated by monsoonal regions of both hemispheres. This mean structure results in a sharply localized longitudinal gradient of PW. Remarkably, regions with positive gradients (such as the Northern and Southern Hemisphere western Indian Ocean), i.e. they have larger PW to the east, are the very zones that are implicated in the formation, and show high levels of convective activity, of the eastward‐moving MJO. On the other hand, regions with negative gradients (such as the Southern Hemisphere central Pacific) are the very regions where genesis, and maxima in variance, of westward‐moving moist equatorial Rossby waves are known to occur. Apart from providing a first‐order longitudinal footprint of the convective phase of these systems, this correspondence reinforces the role of the mean climatic state in tropical ISV. Copyright © 2012 Royal Meteorological Society
A four‐dimensional asynchronous ensemble square‐root filter (4DEnSRF) algorithm and tests with simulated radar data
Authors: Wang Shizhang , Xue Ming , Min Jinzhong
Published: June 2012

A four‐dimensional ensemble square‐root filter algorithm (4DEnSRF) is designed to assimilate high‐frequency asynchronous observations distributed over time. Given the serial nature of the EnSRF, the 4DEnSRF algorithm pre‐calculates observation priors from ensemble model states at observation times and updates the observation priors at asynchronous observational times using the filter. These updated observation posteriors are used to update model state variables at the analysis time. Such an algorithm is able to utilize more observations collected over time with fewer analysis cycles, thereby reducing computational costs and potentially improving filter performance. The 4DEnSRF algorithm is tested using simulated Doppler radar data for a convective storm. The radar data are simulated elevation‐by‐elevation, grouped into batches with different time intervals and then assimilated with analysis cycles of the same lengths. Parallel sets of experiments using 4DEnSRF and the regular EnSRF are performed for comparison, with varying data batch or cycle lengths of 1 to 20 min. For longer time intervals, EnSRF either assumes that all data collected within the time window are valid at the same analysis time, or uses only elevations collected within a shorter time interval centered at the analysis time. Results show that 4DEnSRF outperforms EnSRF when the cycle length is more than 1 min. Observation timing error is the main cause of the performance degradation with EnSRF for both analysis and forecast; the longer the cycle length, the worse the degradation. For long cycle lengths, 4DEnSRF improves the analysis by utilizing more data whereas the EnSRF performs well only when data far away from the analysis time are discarded. Assimilating only a couple of scan elevations at a time using EnSRF with very short cycles can introduce imbalances into the model state that degrades the subsequent analyses and forecasts. Copyright © 2012 Royal Meteorological Society
Comparison of zinc and magnesium clusters in their reaction with organochlorides: Toward a molecular picture of grignard reagent formation
Authors: Barsukov Yu. V. , Porsev V. V. , Tulub A. V.
Published: June 2012

The reaction channels of Znn and Mgn clusters (n = 4, 10) with RCl organochlorides are compared to the investigation of relative activity of metals in the reaction of Grignard reagent formation within a framework of quantum chemical modeling of a reaction path. R radicals are chosen from a list of alkyl (CH3, C2H5, i‐C3H7, and t‐C4H9) and residues with π‐bond (C2H3 and C6H5). Quantum chemistry calculations are made using the density function theory (DFT) approach at the B3PW91/6‐311+G(d) level. The reaction channels for both zinc and magnesium can be classified as radical and nonradical according to the nature of reaction products. The calculation of activation energies shows much similarity in their dependence on the nature of R radical but in the case of zinc, barriers are significantly higher. Both for zinc and magnesium clusters, the radical channels are more preferable in the case of alkyl residues, for vinyl and phenyl residues barriers of radical and nonradical channels are comparable. © 2012 Wiley Periodicals, Inc.
Calculations of structures and reaction energy profiles of As2O3 and As4O6 species by quantum chemical methods
Authors: da Hora Gabriel Costa A. , Longo Ricardo L. , da Silva João Bosco P.
Published: June 2012

Principal component analysis was used in the selection of the B3PW91/6‐311+G(3df) method for calculations of As2O3 molecular species. This multivariate analysis compared experimental properties (structure and ionization energy) of As4O6 molecule with several computational methods (Hartree–Fock, second‐order Møller–Plesset perturbation theory, and density functional theory) and basis sets. At the selected level of theory, we were able to calculate nine structures of As2O3 with three of them being stable ones (no negative force constants) in the following stability order: D3H (0.0), DIAMOND OUT (32.77 kJ mol−1), and GAUCHE (43.81 kJ mol−1). Several intramolecular conversions were studied with the GAUCHE → DIAMOND OUT transformation being barrierless, whereas the DIAMOND OUT structure is converted into the D3H isomer through a Gibbs free‐energy barrier of 40.83 kJ mol−1. Starting from the GAUCHE structure of As2O3 and its enantiomeric form, it was possible to obtain directly (barrierless) the As4O6 species in a spontaneous process (ΔrG = −399.92 kJ mol−1 at 298 K and 1 atm) in gas phase. Thus, the As4O6 species is probably the precursor of arsenic hydroxide through hydrolysis reactions. © 2012 Wiley Periodicals, Inc.
Vertical triple ionization with diffusion quantum monte carlo
Authors: Angelotti W. F. D. , Batista W. R. , Granato A. C.
Published: June 2012

The vertical triple ionization potential is calculated using the diffusion quantum Monte Carlo (DQMC) method for several states of the water molecule. The results are in good agreement with theoretical data presented in the literature. The results demonstrate that the DQMC method is capable of balancing the effects of relaxation and electronic correlation. © 2012 Wiley Periodicals, Inc.
Laplacian‐based models for the exchange energy
Authors: Cancio A. C. , Wagner Chris E. , Wood Shaun A.
Published: June 2012

Recent Quantum Monte Carlo data for the exchange‐correlation energy density of pseudopotential systems strongly suggest the value of using the Laplacian of the density as a variable for constructing first‐order corrections to the local density approximation of density functional theory. We report on an exchange functional built on these observations and extended to the all‐electron case. The model keeps the typical properties of constraint‐based generalized gradient approximations (GGAs) and also has a finite‐valued potential at the nucleus, unlike the GGA. Problems with oscillatory behavior in the potential due to higher order derivatives are controlled by a curvature minimization constraint. The results are tested against exact potentials for the He and Ne atom. A combination of gradient and Laplacian as suggested by a gradient expansion of the exchange hole gives the best overall results. © 2012 Wiley Periodicals, Inc.
The reduced density gradient in atoms
Authors: del Campo Jorge M. , Gázquez José L. , Alvarez‐Mendez Rodrigo J. , Vela Alberto
Published: June 2012

A study of the reduced density gradient s together with the density of s, g(s), for atoms across the periodic table (Li through Xe), following the work of Zupan et al. (Int. J. Quantum Chem. 1997, 61, 835), is presented. The results indicate that the reduced density gradient has maxima and minima related with the shell structure, and that these critical points are associated to the maxima in g(s). The behavior of the critical points in s, of the maxima in g(s) and of the average s calculated through g(s) across the rows and the columns of the periodic table is analyzed. © 2012 Wiley Periodicals, Inc.
Electronic structures and molecular structures of polyynes
Authors: Imamura Akira , Aoki Yuriko
Published: June 2012

Recently, many interesting materials made from carbon atoms have been discovered such as carbon nanotubes, fullerenes, and graphenes. In this article, we studied electronic structures and molecular structures of polyynes with sp2 carbons on both ends. Polyynes calculated were H2CCnCH2 with various number of n. These molecules have two π systems which are perpendicular to each other and these π systems have their tendency to make double bond nature by Peierls instability but for different alternating bonds. In other words, these two π systems are competing to form the double bond formations. The calculations were performed at Hartree–Fock level geometry optimization with 6‐31G, 6‐311G, and 6‐31G** basis sets. For CH2(C)2mCH2, we have found that there are two metastable structures, one of which is the bond‐alternating structure and another is nearly equi‐bond structure. The former has small highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap while the latter has relatively large gap although it is smaller in comparison with the value of polyyne with sp carbon atoms on both ends: H(C)2mH. The small highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap in bond‐alternating structure is due to the fact that HOMO and MO's near to HOMO have relatively localized electronic distribution in both end regions, and thus, the weak interaction between the both regions leads to the small HOMO–LUMO gap. The stability is larger for the former especially in long polyynes. For CH2(C)2m+1CH2, we have found only one stable structure, that is, equi‐bond structure. This type of polyyne oligomers has two terminal CH2 groups which are perpendicular with each other. It is found that the longer the length of oligomer is, the smaller the HOMO–LUMO gap is as is usually expected. By summarizing these results, we proposed a design for a single‐chain electronically conductive polymers. © 2012 Wiley Periodicals, Inc.
Implementation of a variational code for the calculation of rate constants and application to barrierless dissociation and radical recombination reactions: CH3OH = CH3 + OH
Authors: de M. Oliveira Rodrigo C. , Bauerfeldt Glauco F.
Published: June 2012

Here, a new implementation for calculating canonical variational rate constants is introduced and tested against methanol dissociation rate constants and the (high pressure) radical recombination reaction, CH3 + OH → CH3OH. Reaction paths are described at the CASSCF level, with energy corrections at MRMP2. Molecular properties for both stationary and non‐stationary points along the reaction path are used for the calculation of rate constants. Different models for the low vibrational frequencies are discussed: harmonic oscillator and free rotor models. The CH3 + OH → CH3OH recombination rate constants are determined from dissociation rate constants and equilibrium constants. Our calculated rate constants agree with previously reported data for these reactions, suggesting the good performance of our implemented code in calculating canonical variational rate constants. The rate expressions are suggested: as: kdis (T) = 8.42 × 10+16 × e−96.18/RT and krec (T) = 2.05 × 10−10 × (T/298)−0.24 × e−0.30/RT, in units s−1 and cm3 molecule−1 s−1, respectively, and over the temperature range 300–2000 K, with activation energies in kcal/mol. © 2012 Wiley Periodicals, Inc.
Exploring the conformation, charge density distribution and the electrostatic properties of galanthamine molecule in the active site of AChE using DFT and AIM theory
Authors: Renuga Parameswari Azhagesan , Kumaradhas Poomani
Published: June 2012

Quantum chemical calculations and charge density analysis were carried out to understand the geometry, charge density distribution and the electrostatic properties of isolated galanthamine molecule (form I) and for the same lifted out from the active site (form II) of AChE. The optimized geometry of isolated galanthamine was obtained from a hybrid density functional theory (B3LYP/6‐311G**) calculation. A docking analysis on galanthamine with AChE was performed, and the lowest docked energy structure was selected from the active site of AChE for the further study. A single point energy quantum chemical calculation (B3LYP/6‐311G**) was carried out for the lowest energy structure, which was lifted from the galanthamine–AChE complex from molecular docking analysis. The structural comparison between (I) and (II) helps to understand the conformational modification of the galanthamine molecule in the active site. When the molecule present in the active site, the molecular geometry is seen to be significantly altered, specifically, large changes were observed in the outer core of the molecule while the inner core geometry is intact. The bond topological and electrostatic properties of (I) and (II) were calculated. The dipole moment of the galanthamine molecule also increases from 2.09 to 2.67 D in the process. A large negative electrostatic potential region is found at the vicinity of oxygen and nitrogen atoms of the molecule, which predominantly involve strong hydrophobic and electrostatic interactions with the amino acid residues TRP84, PHE330, GLY118, TYR70, and SER122 present in the active site of AChE. © 2013 Wiley Periodicals, Inc.
The number of spanning trees in an (r, s)‐semiregular graph and its line graph
Authors: Bibak Khodakhast
Published: June 2012

For a graph G, a “spanning tree” in G is a tree that has the same vertex set as G. The number of spanning trees in a graph (network) G, denoted by t(G), is an important invariant of the graph (network) with lots of decisive applications in many disciplines. In the article by Sato (Discrete Math. 2007, 307, 237), the number of spanning trees in an (r, s)‐semiregular graph and its line graph are obtained. In this article, we give short proofs for the formulas without using zeta functions. Furthermore, by applying the formula that enumerates the number of spanning trees in the line graph of an (r, s)‐semiregular graph, we give a new proof of Cayley's Theorem. © 2013 Wiley Periodicals, Inc.
Insights for design of Trypanosoma cruzi GAPDH inhibitors: A QM/MM MD study of 1,3‐bisphospo‐D‐glyceric acid analogs
Authors: Araújo Silva José Rogério , Lameira Jerônimo , Alves Cláudio Nahum
Published: June 2012

Glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) is a key‐enzyme for design of new drugs against Chagas disease. Herein, molecular inhibition mechanism of GAPDH involving 1,3‐bisphospho‐D‐glyceric acid (1,3‐BPGA) analogs were studied using the hybrid quantum mechanical/molecular mechanical (QM/MM) approach and molecular dynamic simulations. The analysis of the binding contribution of the individual residues shows that Lys209, Asp210, Arg212, Thr167, Thr197, Thr199, Ser224, Thr226, Ser247, Arg249, water molecules, and NAD+ are responsible for stabilization of the protein‐inhibitor complexes. The results obtained suggest that Arg249 plays an important role in the GAPDH‐inhibitor complex and might induce the compression of the 1,3‐BPGA analogs inside the active site of GAPDH. In addition, analysis of QM/MM molecular dynamics simulations have shown that the extended conformation 1,3‐BPGA analogs contribute to biological activity of these compounds. © 2012 Wiley Periodicals, Inc.
Electron detachment energies of aqueous and cluster halide anions from electron propagator calculations with the polarizable continuum model
Authors: Dolgounitcheva Olga , Zakrzewski Viatcheslav G. , Ortiz Joseph Vincent
Published: June 2012

To calibrate computational studies of photoelectron spectra of dissolved anions, the vertical electron detachment energies (VEDEs) of the fluoride and chloride anions in isolation and in the presence of six coordinated water molecules have been calculated with and without the polarizable continuum model (PCM) of solvation in water. Large shifts in VEDEs and important changes in coordination geometries about the chloride anion occur with the use of the PCM. Cluster and PCM calculations confirm previous, qualitative conclusions on Dyson orbitals corresponding to the lowest VEDEs of aqueous halide anions. For the fluoride case, Dyson orbitals for the lowest VEDEs are spread over water molecules, not the anion, but for the chloride case, the Dyson orbitals for the lowest VEDEs are localized on the anion. The partial third‐order (P3) and P3+ approximations of electron propagator theory provide a reliable means to calculating VEDEs with polarized atomic basis sets. © 2012 Wiley Periodicals, Inc.
Rung 3.5 density functionals: Another step on Jacob's ladder
Authors: Janesko Benjamin G.
Published: June 2012

Applications of density functional theory (DFT) to computational chemistry and solid‐state physics rely on a “Jacob's Ladder” of progressively more complicated approximations to the many‐body exchange‐correlation (XC) density functional. Accurate, computationally tractable DFT calculations on large and periodic systems remain challenging for existing XC functionals. Simple XC functionals on the three lowest rungs of Jacob's Ladder are insufficiently accurate for many properties, while fourth‐rung hybrid functionals incorporating nonlocal information can be prohibitively expensive. This perspective presents our work toward a compromise, a new class of “Rung 3.5” functionals that incorporate a linear dependence on the nonlocal one‐particle density matrix. This work reviews these functionals' formal underpinning, numerical performance, and prospects for modeling solids and surfaces. © 2012 Wiley Periodicals, Inc.
DFT modeling of band shifts and widths in the absorption spectrum of a 9‐(diphenylamino)acridine/silica receptor center upon its interaction with gas‐phase NH3, C2H5OH, and (CH3)2CO molecules
Authors: Chashchikhin Vladimir , Rykova Elena , Scherbinin Andrei , Bagaturyants Alexander
Published: June 2012

The interaction of small analyte molecules (NH3, C2H5OH, and (CH3)2CO) in the gas phase with the 9‐(diphenylamino)acridine dye adsorbed on an amorphous silica surface is studied by density functional theory (DFT) calculations using the cluster approach. Two cluster models for the silica surface are considered: a small SiH3OH model and an extended Si10O11(OH)18 one, constructed using classical molecular dynamics simulations. The electronic absorption spectra of the adsorbed dye are calculated within the time‐dependent density functional theory (TDDFT) formalism and the effects of dye–analyte interactions are investigated. The spectral line broadening due to vibrations is estimated within the Pekar model. A computationally efficient procedure is proposed for the prediction of changes in the absorption spectra of organic dyes adsorbed on silica on their interaction with analytes. © 2012 Wiley Periodicals, Inc.
Optoelectronic properties of KDP by first principle calculations
Authors: Aliabad Hossein Asghar Rahnamaye , Fathabadi Marjan , Ahmad Iftikhar
Published: June 2012

The optoelectronic properties of KDP (KH2PO4), in orthorhombic and tetragonal phases, have been investigated by generalized gradient approximation (GGA) and mBJ‐GGA within density functional theory. The calculated fundamental indirect band gaps for orthorhombic and tetragonal KDPs are 2.83 and 4.35 eV, respectively. The calculated effective mass of electron, in this compound, is very close to the effective mass of carriers in a bilayer graphene. The electron density plots show that the covalent bonds between P and O within the PO4 tetrahedra are symmetric in tetragonal phase, whereas in the orthorhombic phase this symmetry breaks, which affects the covalent bonds among the tetrahedra. The comparison of the calculated optical spectra by GGA and mBJ‐GGA with the experimental results reveals that the optical dispersion spectra by mBJ‐GGA are in closer agreement with the experimental results. © 2012 Wiley Periodicals, Inc.
Stochastic stability and robust stabilization of semi‐Markov jump linear systems
Authors: Huang Ji , Shi Yang
Published: June 2012

The semi‐Markov jump linear system (S‐MJLS) is more general than the Markov jump linear system (MJLS) in modeling some practical systems. Unlike the constant transition rates in the MJLS, the transition rates of the S‐MJLS are time varying. This paper focuses on the robust stochastic stability condition and the robust control design problem for the S‐MJLS with norm‐bounded uncertainties. The infinitesimal generator for the constructed Lyapunov function is first derived. Numerically solvable sufficient conditions for the stochastic stability of S‐MJLSs are then established in terms of linear matrix inequalities. To reduce the conservativeness of the stability conditions, we propose to incorporate the upper and lower bounds of the transition rate and meanwhile apply a new partition scheme. The robust state feedback controller is accordingly developed. Simulation studies and comparisons demonstrate the effectiveness and advantages of the proposed methods. Copyright © 2012 John Wiley & Sons, Ltd.
The Effect of Some Fluids on Surface Oxidation and Amount of Released Iron of Stainless Steel Endodontic Files
Authors: Saghiri Mohammad Ali , García‐Godoy Franklin , Lotfi Mehrdad , Mehrvazfar Peyman , Aminsobhani Mohsen , Rezaie Samad , Asgar Kamal
Published: June 2012

Endodontic files come in contact with blood, infected pulp tissue, and irrigating solutions during root canal therapy. Some instruments such as stereomicroscopy and scanning electron microscopy are used to observe corrosion of endodontic files which are complicated and dependent on preparation methods. Having knowledge of the corrosion and ion release of endodontic files can help in drawing firm deductions as to which files would perform better in the clinical scenario. Therefore, we have used energy dispersive X‐ray analysis and an atomic absorption spectrophotometer to track oxygen on the surface and iron in the exposed media to observe the oxidative rate of the media. In this study, corrosion by blood was higher than other biological fluids, but less than with sodium hypochlorite (NaOCl). Observations of energy dispersive X‐ray analysis and atomic absorption spectrophotometer results demonstrated that after exposure the amount of oxygen on the surface and surrounding areas increased. Therefore, the files should be rinsed as soon as possible during and after use to hinder the oxidation rate, but blood may produce a different behavior and it might be considered as a decreased risk of broken stainless steel files remaining in the root canal after treatment. SCANNING 34: 309‐315, 2012. © 2012 Wiley Periodicals, Inc.
Electron Beam Induced Growth of Silver Nanoparticles
Authors: Shi Guanghua , Bao Shengxiang , Lai Weiming , Rao Zhenzhen , Zhang Xiaowen , Wang Zuwen
Published: July 2012

An electron beam inducing method for sprouting large quantities of silver nanoparticles on the surface of silver chloride particles is reported. The electron beam driven process was characterized by time‐dependent scanning electron microscope (SEM) and energy dispersive spectrum (EDS), allowing for observing several key intermediates in and characteristics of the growth process. Theoretical calculation coupled with experimental observation demonstrated that the growth of silver nanoparticles was mostly related to the current density of electron beam. Decomposition of the silver chloride on the surface of sample was under electron beam irradiation resulted in silver nanoparticles and chlorine. This phenomenon could be useful in developing a novel mechanism for preparation of nanostructures and proposing a reference to avoid image distortion during the characterization of silver compounds under SEM. SCANNING 35: 69‐74, 2013. © 2012 Wiley Periodicals, Inc.
Sustainable Architecture, Design and Housing
Authors: Keitsch Martina
Published: June 2012

This editorial article for the special issue of Sustainable Development ‘Sustainable architecture, design and housing’ introduces the main topics and reviews the following nine articles. The aim of the special issue is to discuss key concepts, methods, applications and lessons learned in sustainable architecture, design and housing. Sustainable architecture challenges new and ingenious architectural design at various levels. Examples are the following. (1) Minimizing the negative environmental impact of buildings by enhancing efficiency and moderating the use of materials, energy and development space. (2) Developing measures to relate form and adapt the design to the site, the region and the climate. (3) Establishing a harmonious, long lasting relationship between the inhabitants and their surroundings by addressing the essence of good form‐giving (Abidin et al., ). In summary, sustainable architecture shall be well built, easy to use and beautiful. The selected articles highlight special aspects of sustainability in architecture, design and housing, either due to their novel theoretical contributions or in relation to tools, measurements and strategies. A main research objective on sustainable design is to promote understanding for the particular problems that architects and designers face and to discuss solutions to solve them. This can in turn also be described as the relevance of sustainable design research for the overarching sustainable development debate. Sustainable design is dynamic and comprises both normative, strategic, designerly and technical aspects (Cross, ). Three areas are thematically highlighted in this special issue.

Overarching conception of sustainable architecture and design and their impact on a sustainable development.

Methodologies and tools and their applications to sustainable design.

Policy and strategy development to assess and implement sustainable design.

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