bluuebunny/crossref_metadata_2025 huggingface dataset:
Cannabis or alcohol first? Differences by ethnicity and in risk for rapid progression to cannabis-related problems in women
Authors: Sartor C. E. , Agrawal A. , Lynskey M. T. , Duncan A. E. , Grant J. D. , Nelson E. C. , Madden P. A. F. , Heath A. C. , Bucholz K. K.
Published: July 2012

Background

Initiation of cannabis use typically follows alcohol use, but the reverse order does occur and is more common for African-Americans (AAs) than European-Americans (EAs). The aim of this study was to test for differences in the order of initiation of cannabis and alcohol use between AA and EA women and to determine whether order and ethnicity contribute independently to risk for rapid progression to cannabis-related problems.

Method

Data were drawn from structured psychiatric interviews of 4102 women (mean age = 21.6 years), 3787 from an all-female twin study and 315 from a high-risk family study; 18.1% self-identified as AA, 81.9% as EA. Ethnicity and order of initiation of cannabis and alcohol use were modeled as predictors of transition time from first use to onset of cannabis use disorder symptom(s) using Cox proportional hazards regression analyses.

Results

AA women were nearly three times as likely as EA women to initiate cannabis use before alcohol use. Using cannabis before alcohol [hazard ratio (HR) 1.44, 95% confidence interval (CI) 1.08–1.93] and AA ethnicity (HR 1.59, 95% CI 1.13–2.24) were both associated with rapid progression from first use to cannabis symptom onset even after accounting for age at initiation and psychiatric risk factors.

Conclusions

The findings indicate that AA women are at greater risk for rapid development of cannabis-related problems than EA women and that this risk is even higher when cannabis use is initiated before alcohol use. Prevention programs should be tailored to the various patterns of cannabis use and relative contributions of risk factors to the development of cannabis-related problems in different ethnic groups.
Spiders’ webs and locally connected Julia sets of transcendental entire functions
Authors: OSBORNE J. W.
Published: July 2012

We show that if the Julia set of a transcendental entire function is locally connected, then it takes the form of a spider’s web in the sense defined by Rippon and Stallard. In the opposite direction, we prove that a spider’s web Julia set is always locally connected at a dense subset of buried points. We also show that the set of buried points (the residual Julia set) can be a spider’s web.
Learning to swim: a dynamical systems approach to mimicking fish swimming with CPG
Authors: Wang Tianmiao , Hu Yonghui , Liang Jianhong
Published: July 2012

Central Pattern Generators (CPGs) can generate robust, smooth and coordinated oscillatory signals for locomotion control of robots with multiple degrees of freedom, but the tuning of CPG parameters for a desired locomotor pattern constitutes a tremendously difficult task. This paper addresses this problem for the generation of fish-like swimming gaits with an adaptive CPG network on a multi-joint robotic fish. Our approach converts the related CPG parameters into dynamical systems that evolve as part of the CPG network dynamics. To reproduce the bodily motion of swimming fish, we use the joint angles calculated with the trajectory approximation method as teaching signals for the CPG network, which are modeled as a chain of coupled Hopf oscillators. A novel coupling scheme is proposed to eliminate the influence of afferent signals on the amplitude of the oscillator. The learning rules of intrinsic frequency, coupling weight and amplitude are formulated with phase space representation of the oscillators. The frequency, amplitudes and phase relations of the teaching signals can be encoded by the CPG network with adaptation mechanisms. Since the Hopf oscillator exhibits limit cycle behavior, the learned locomotor pattern is stable against perturbations. Moreover, due to nonlinear characteristics of the CPG model, modification of the target travelling body wave can be carried out in a smooth way. Numerical experiments are conducted to validate the effectiveness of the proposed learning rules.
Seboxplays an important role during the early mouse oogenesisin vitro
Authors: Moreno Dafne Linda , Salazar Zayil , Betancourt Miguel , Casas Eduardo , Ducolomb Yvonne , González Cristina , Bonilla Edmundo
Published: July 2012

Oogenesis is a highly complex process that requires the exquisite temporal and spatial regulation of gene expression at multiple levels. Skin–embryo–brain–oocyte homeobox (Sebox) gene encodes a transcription factor that is highly expressed in germinal vesicle stage oocytes and that plays an essential role in early embryogenesis at the 2-cell stage in the mouse. AsSeboxis also expressed in mouse fetal ovaries, the aim of the present study was to study its role during the early oogenesisin vitro. Expression ofSeboxwas low in 15.5 to 17.5 days post coitum (dpc) ovaries, showed a peak at 18.5 dpc and then its expression decreased dramatically in newborn ovaries.Seboxexpression was efficiently knocked down (>80%) in fetal mouse ovary explants in culture using RNAi technology. When fetal ovary explants were transfected withSebox-specific RNAi, the number of oocytes at germinal vesicle stage and showing a diameter of 40–70 μm was decreased significantly to 75% after 7 days of culture relative to the negative control, and to 22.4% after 10 days of culture, thus indicating thatSeboxplays an important role in the early oogenesis in mice.
Armies, Wars and their Food
Authors: Rao D. Vijaya
Published: July 2012

In the history of mankind, armies fought at the behest of a ruler to conquer and expand territories. In due course, war crafts were devised and war logistics were developed. However, armies food remained much the same as ever for a very long time. Eventually science and technology played a crucial role in bringing army foods and nourishment to the expected level of modernity, commensurate with advancements in other features of the war craft. Armies, Wars and their Food traces the evolution of military rations and provides insights into the concept of nutrition for military from the point of a food scientist. The principal theme of the book is the historical development of armies and the supply and delivery systems prevalent at different periods of time. Providing a ready source of historical perspectives on the armies, it discusses the role of science and technology in instigating improvements in military ration. The book will appeal to students of food science and nutrition, army, navy and air force establishments, food industry laboratories and research and development organizations. General readers interested in the history of science and military history will also find this book useful.
Large electronic bandwidth in solution-processable pyrene crystals: The role of close-packed crystal structure
Authors: Provencher Françoise , Bérubé Nicolas , Laprade Jean-Frédéric , Simard Gabrielle , Tant Julien , de Halleux Véronique , Geerts Yves , Silva Carlos , Côté Michel
Published: July 2012

We examine the interdependence of structural and electronic properties of two substituted pyrene crystals by means of combined spectroscopic probes and density-functional theory calculations. Substituted pyrenes are useful model systems to unravel the interplay of crystal structure and electronic properties in organic semiconductors. To study the effect of steric encumbrance on the crystalline arrangement of two 1,3,6,8-tetraalkynylpyrene derivatives, one features linear n-hexyl side groups while the other contains branched trimethylsilyl groups. Both derivatives form triclinic crystal structures when grown from solution, but the electronic dispersion behavior is significantly different due to differences in π–π overlap along the π-stacking axis. Both systems display dispersion of around 0.45 eV in the valence band, suggesting a high intrinsic hole mobility. However, the direction of the dispersion is different: it is primarily along the π-stacking axis in the trimethylsilyl-substituted derivative, but less aligned with this crystal axis in the hexyl-substituted molecule. This is a direct consequence of the differences in co-facial π electron overlap revealed by the crystallographic studies. We find that photophysical defects, ascribed to excimer-like states, point to the importance of localized trap states.
A high-field adiabatic fast passage ultracold neutron spin flipper for the UCNA experiment
Authors: Holley A. T. , Broussard L. J. , Davis J. L. , Hickerson K. , Ito T. M. , Liu C.-Y. , Lyles J. T. M. , Makela M. , Mammei R. R. , Mendenhall M. P. , Morris C. L. , Mortensen R. , Pattie R. W. , Rios R. , Saunders A. , Young A. R.
Published: July 2012

The UCNA collaboration is making a precision measurement of the β asymmetry (A) in free neutron decay using polarized ultracold neutrons (UCN). A critical component of this experiment is an adiabatic fast passage neutron spin flipper capable of efficient operation in ambient magnetic fields on the order of 1 T. The requirement that it operate in a high field necessitated the construction of a free neutron spin flipper based, for the first time, on a birdcage resonator. The design, construction, and initial testing of this spin flipper prior to its use in the first measurement of A with UCN during the 2007 run cycle of the Los Alamos Neutron Science Center's 800 MeV proton accelerator is detailed. These studies determined the flipping efficiency of the device, averaged over the UCN spectrum present at the location of the spin flipper, to be \documentclass[12pt]{minimal}\begin{document}$\overline{\epsilon }=0.9985(4)$\end{document}ε¯=0.9985(4).
On solving the master equation in spatially periodic systems
Authors: Kolokathis Panagiotis D. , Theodorou Doros N.
Published: July 2012

We present a new method for solving the master equation for a system evolving on a spatially periodic network of states. The network contains 2ν images of a “unit cell” of n states, arranged along one direction with periodic boundary conditions at the ends. We analyze the structure of the symmetrized (2νn) × (2νn) rate constant matrix for this system and derive a recursive scheme for determining its eigenvalues and eigenvectors, and therefore analytically expressing the time-dependent probabilities of all states in the network, based on diagonalizations of n × n matrices formed by consideration of a single unit cell. We apply our new method to the problem of low-temperature, low-occupancy diffusion of xenon in the zeolite silicalite-1 using the states, interstate transitions, and transition state theory-based rate constants previously derived by June et al. [J. Phys. Chem. 95, 8866 (1991)]. The new method yields a diffusion tensor for this system which differs by less than 3% from the values derived previously via kinetic Monte Carlo (KMC) simulations and confirmed by new KMC simulations conducted in the present work. The computational requirements of the new method are compared against those of KMC, numerical solution of the master equation by the Euler method, and direct molecular dynamics. In the problem of diffusion of xenon in silicalite-1, the new method is shown to be faster than these alternative methods by factors of about 3.177 × 104, 4.237 × 103, and 1.75 × 107, respectively. The computational savings and ease of setting up calculations afforded by the new method of master equation solution by recursive reduction of dimensionality in diagonalizing the rate constant matrix make it attractive as a means of predicting long-time dynamical phenomena in spatially periodic systems from atomic-level information.
Spinodal decomposition and droplets entrapment in monotectic solidification
Authors: Wang F. , Choudhury A. , Strassacker C. , Nestler B.
Published: July 2012

In this article, we present two models to simulate solidification morphologies in monotectic alloys. With the first model, we investigate the morphological evolution under the influence of spinodal decomposition. The model requires that a gradient energy contribution for the concentration field should be incorporated, in order to stabilize phase separation when the liquid concentration is inside the region of miscibility gap. The free energy of the system in this model is derived from direct interpolation of the bulk energy densities. This, however, results in simulation regions in nanometer scale due to contributions from the chemical free energy of the system to the total surface excess. With the second model, our purpose is to develop a phase-field model to simulate scales that are larger than nanometer, where the departures from equilibrium are very small resulting in phase concentrations outside the spinodal region. In view of this, we exclude the concentration gradient contribution to the grand chemical potential functional, and develop a model based on [M. Plapp, Phys. Rev. E 84, 031601 (2011)10.1103/PhysRevE.84.031601; A. Choudhury and B. Nestler, Phys. Rev. E 85, 021602 (2012)]10.1103/PhysRevE.85.021602. The advantage is that the free energy excess across the interface at equilibrium disappears, and hence it is easier to derive the required surface energies with higher interface widths. Due to this benefit, we employ the method to simulate the dynamic entrapment process in the monotectic reaction and study the influence of liquid1 − liquid2 surface energy and undercooling on the entrapment process.
On nonlocal Gross-Pitaevskii equations with periodic potentials
Authors: Curtis Christopher W.
Published: July 2012

The Gross-Pitaevskii equation is a widely used model in physics, in particular in the context of Bose-Einstein condensates. However, it only takes into account local interactions between particles. This paper demonstrates the validity of using a nonlocal formulation as a generalization of the local model. In particular, the paper demonstrates that the solution of the nonlocal model approaches in norm the solution of the local model as the nonlocal model approaches the local model. The nonlocality and potential used for the Gross-Pitaevskii equation are quite general, thus this paper shows that one can easily add nonlocal effects to interesting classes of Bose-Einstein condensate models. Based on a particular choice of potential for the nonlocal Gross-Pitaevskii equation, we establish the orbital stability of a class of parameter-dependent solutions to the nonlocal problem for certain parameter regimes. Numerical results corroborate the analytical stability results and lead to predictions about the stability of the class of solutions for parameter values outside of the purview of the theory established in this paper.
A higher-k tetragonal HfO2 formed by chlorine plasma treatment at interfacial layer for metal-oxide-semiconductor devices
Authors: Fu Chung-Hao , Chang-Liao Kuei-Shu , Li Chen-Chien , Ye Zong-Hao , Hsu Fang-Ming , Wang Tien-Ko , Lee Yao-Jen , Tsai Ming-Jinn
Published: July 2012

A tetragonal HfO2 (t-HfO2) with higher-k value and large band gap is investigated in this work. X-ray diffraction analysis shows a t-HfO2 can be formed by using Cl2 plasma treatment at the HfO2/Si interface after a post deposition annealing at 650 °C. The mechanisms of t-HfO2 formation can be attributed to the Si diffusion and oxygen vacancy generation which are formed by Cl2 plasma treatment. From the cross-sectional transmission electron microscope and capacitance-voltage measurement, the k value of this t-HfO2 is estimated to be about 35. The optical band gap value for t-HfO2 is similar to that of the monoclinic.
Ge2Sb2Te5 phase-change films on polyimide substrates by pulsed laser deposition
Authors: Lu Hongbing , Thelander Erik , Gerlach Jürgen W. , Hirsch Dietmar , Decker Ulrich , Rauschenbach Bernd
Published: July 2012

Growth of Ge2Sb2Te5 phase-change films on flexible polyimide substrates by pulsed laser deposition (PLD) is demonstrated. The effect of annealing temperature on the crystalline nature of the films was studied. A decrease of (200) lattice plane distance with the increase of annealing temperature was revealed for the films grown on both polyimide and Si substrates, which was related to tensile stress in the crystallized films. Optical reflectivity measurements showed a high reflectivity contrast between full crystalline and amorphous films. The results indicate an excellent potential for applications of these PLD-deposited Ge2Sb2Te5 films on flexible polyimide substrates in optical data storage.
Photocurrent spectroscopy of site-controlled pyramidal quantum dots
Authors: Mohan A. , Nevou L. , Gallo P. , Dwir B. , Rudra A. , Kapon E. , Faist J.
Published: July 2012

Intraband photocurrent spectroscopy of site-controlled pyramidal quantum dots by inserting them into the intrinsic region of n-i-n like quantum dot infrared photodetector structure is reported. The photovoltaic response is observed in the mid-infrared region. A peak responsivity of 0.4 mA/W at 120 meV (λ = 10 μm) is observed at 10 K at −2 V bias. The ability to engineer states in the conduction band of the QDs has been exploited to tune their photocurrent response from 10 μm to 18 μm with a narrow spectral width of Δλ/λ = 0.17.
On the energy conversion and efficiency of a dielectric electroactive polymer generator
Authors: Wang Huaming , Wang Chengshu , Yuan Tongyan
Published: July 2012

Dielectric electroactive polymers are studied for their energy generating ability based on a variable capacitance mechanism. Energy conversion for one cycle is analyzed by considering the energy loss in the charging process, where generated energy is defined as the difference between output and total input electrical energy. Experiments are conducted under two charging modes and different stretch rates to investigate their effect on the energy conversion. Energy conversion efficiency of up to 18.3% is achieved with charging-while-stretching mode and a low stretch rate, with an energy density of 18.9 mJ/g and power of 3.775 mW/g per cycle obtained.
Metallic glass mold insert for hot embossing of polymers
Authors: Ma J. , Zhang X. , Wang W. H.
Published: July 2012

Molding of micro components from thermoplastic polymers (TPs) has become a routinely used industrial production process. To find hard, ductile and durable material for mold insert and to fabricate the mold insert are two big challenges for the thermoplastic polymers fabrication techniques. We report that a Pd-based metallic glass (MG) mold insert was readily fabricated in its supercooled liquid region, and the atomic force microscope measurement and time-temperature-transformation analysis show that the metallic glass mold insert has very fine surface quality and long service life. We show that the metallic glasses, which have remarkable mechanical properties and excellent thermoplastic forming ability, are new ideal materials for hot embossing mold insert of thermoplastic polymers.
Effect of magnetic field on the wave dispersion relation in three-dimensional dusty plasma crystals
Authors: Yang Xue-Feng , Wang Zheng-Xiong
Published: July 2012

Three-dimensional plasma crystals under microgravity condition are investigated by taking into account an external magnetic field. The wave dispersion relations of dust lattice modes in the body centered cubic (bcc) and the face centered cubic (fcc) plasma crystals are obtained explicitly when the magnetic field is perpendicular to the wave motion. The wave dispersion relations of dust lattice modes in the bcc and fcc plasma crystals are calculated numerically when the magnetic field is in an arbitrary direction. The numerical results show that one longitudinal mode and two transverse modes are coupled due to the Lorentz force in the magnetic field. Moreover, three wave modes, i.e., the high frequency phonon mode, the low frequency phonon mode, and the optical mode, are obtained. The optical mode and at least one phonon mode are hybrid modes. When the magnetic field is neither parallel nor perpendicular to the primitive wave motion, all the three wave modes are hybrid modes and do not have any intersection points. It is also found that with increasing the magnetic field strength, the frequency of the optical mode increases and has a cutoff at the cyclotron frequency of the dust particles in the limit of long wavelength, and the mode mixings for both the optical mode and the high frequency phonon mode increase. The acoustic velocity of the low frequency phonon mode is zero. In addition, the acoustic velocity of the high frequency phonon mode depends on the angle of the magnetic field and the wave motion but does not depend on the magnetic field strength.
High aspect ratio and high breakdown strength metal-oxide capacitors
Authors: Usui T. , Mollinger S. A. , Iancu A. T. , Reis R. M. , Prinz F. B.
Published: July 2012

Thin film capacitors of HfO2 with high energy storage were fabricated using plasma-enhanced atomic layer deposition on a relatively large platform with a lateral area of 0.8-7.1 mm2. An untreated film of 10-nm HfO2 showed a breakdown strength of 0.47 V/nm. Annealing of HfO2 formed a large crystalline phase, which creates electron paths and increases defect-induced currents. Laminate structures of Al2O3 and HfO2 were also fabricated to relate crystallinity, current leakage path, and breakdown behavior. A 7-layer laminate structure exhibited a breakdown strength of 0.58 V/nm with an aspect ratio of 1:300 000 due to suppressed crystallinity.
Inkjet printed carbon nanotube networks: the influence of drop spacing and drying on electrical properties
Authors: Wang Tianming , Roberts Michael A , Kinloch Ian A. , Derby Brian
Published: July 2012

We have measured the electrical resistance of inkjet printed multiwall carbon nanotube networks and found that it depends strongly on the temperature of the substrate during the printing process, with both the resistance and its anisotropy decreasing as temperature increases. A parallel investigation of the surface morphology of the printed networks found long raised ridges running parallel to the printing direction, with the height of the ridges decreasing with increasing substrate temperature. Both these observations are shown to be associated with segregation of the nanotubes during drying (coffee staining) and that this segregation is suppressed at higher substrate temperatures, with the lowest resistance values and anisotropy found with a substrate temperature of 70 °C. Network conductance was found to increase with increasing layer thickness and similar results are obtained through a reduction in drop spacing or by printing multiple layers.
A model of carbon nanotube synthesis in arc discharge plasmas
Authors: Kundrapu M , Li J , Shashurin A , Keidar M
Published: July 2012

Nanoparticle growth in arc discharges is analysed numerically. An analysis is carried out for the root growth method of nanotubes in plasmas. The existing models for estimating the growth of nanoparticles in stationary plasmas are extended to plasmas with variable properties. The distributions of velocity, species density and temperature from numerical simulations are used as input to the growth models. The nickel particle diameter obtained from the numerical model is 9.2 nm and the frequency of finding this size in the experiment is 26 on the larger side. The length of the single-walled carbon nanotube obtained from the model is 2.1 µm, which falls in the upper 10% of the size distribution from experiment. Parametric studies are carried out varying the arc current, inter-electrode gap and background pressure. Results showed 40–95% increment in the nanotube length by increasing the background pressure and the inter-electrode gap. A hot-chamber arc discharge method is proposed to maximize the growth of nanoparticles subjected to the conditions identical to those existing in convectional arc discharges.
The effect of remodelling and contractility of the actin cytoskeleton on the shear resistance of single cells: a computational and experimental investigation
Authors: Dowling Enda P. , Ronan William , Ofek Gidon , Deshpande Vikram S. , McMeeking Robert M. , Athanasiou Kyriacos A. , McGarry J. Patrick
Published: July 2012

The biomechanisms that govern the response of chondrocytes to mechanical stimuli are poorly understood. In this study, a series of
in vitro
tests are performed, in which single chondrocytes are subjected to shear deformation by a horizontally moving probe. Dramatically different probe force–indentation curves are obtained for untreated cells and for cells in which the actin cytoskeleton has been disrupted. Untreated cells exhibit a rapid increase in force upon probe contact followed by yielding behaviour. Cells in which the contractile actin cytoskeleton was removed exhibit a linear force–indentation response. In order to investigate the mechanisms underlying this behaviour, a three-dimensional active modelling framework incorporating stress fibre (SF) remodelling and contractility is used to simulate the
in vitro
tests. Simulations reveal that the characteristic force–indentation curve observed for untreated chondrocytes occurs as a result of two factors: (i) yielding of SFs due to stretching of the cytoplasm near the probe and (ii) dissociation of SFs due to reduced cytoplasm tension at the front of the cell. In contrast, a passive hyperelastic model predicts a linear force–indentation curve similar to that observed for cells in which the actin cytoskeleton has been disrupted. This combined modelling–experimental study offers a novel insight into the role of the active contractility and remodelling of the actin cytoskeleton in the response of chondrocytes to mechanical loading.
Overtopping of solitary waves and solitary bores on a plane beach
Authors: Baldock T. E. , Peiris D. , Hogg A. J.
Published: July 2012

The overtopping of solitary waves and bores present major hazards during the initial phase of tsunami inundation and storm surges. This paper presents new laboratory data on overtopping events by both solitary waves and solitary bores. Existing empirical overtopping scaling laws are found to be deficient for these wave forms. Two distinct scaling regimes are instead identified. For solitary waves, the overtopping rates scale linearly with the deficit in run-up freeboard. The volume flux in the incident solitary wave is also an important parameter, and a weak dependence on the nonlinearity of the waves (
H
/
d
) is observed. For solitary bores, the overtopping cannot be scaled uniquely, because the fluid momentum behind the incident bore front is independent of the bore height, but it is in close agreement with recent solutions of the nonlinear shallow water equations. The maximum overtopping rate for the solitary waves is shown to be the lower bound of the overtopping rate for the solitary bores with the same deficit in freeboard. Thus, for a given run-up, the solitary bores induce greater overtopping rates than the solitary waves when the relative freeboard is small.
Lethal effects of habitat degradation on fishes through changing competitive advantage
Authors: McCormick Mark I.
Published: July 2012

Coral bleaching has caused catastrophic changes to coral reef ecosystems around the world with profound ecological, social and economic repercussions. While its occurrence is predicted to increase in the future, we have little understanding of mechanisms that underlie changes in the fish community associated with coral degradation. The present study uses a field-based experiment to examine how the intensity of interference competition between juveniles of two species of damselfish changes as healthy corals degrade through thermal bleaching. The mortality of a damselfish that is a live coral specialist (
Pomacentrus moluccensis
) increased on bleached and dead coral in the presence of the habitat generalist (
Pomacentrus amboinensis
). Increased mortality of the specialist was indirectly owing to enhanced aggression by the generalist forcing the specialist higher up and further away from shelter on bleached and dead coral. Evidence from this study stresses the importance of changing interspecific interactions to community dynamics as habitats change.
Explaining differences in the lifespan and replicative capacity of cells: a general model and comparative analysis of vertebrates
Authors: Gillooly James F. , Hayward April , Hou Chen , Burleigh J. Gordon
Published: July 2012

A better understanding of the factors that govern individual cell lifespan and the replicative capacity of cells (i.e. Hayflick's limit) is important for addressing disease progression and ageing. Estimates of cell lifespan
in vivo
and the replicative capacity of cell lines in culture vary substantially both within and across species, but the underlying reasons for this variability remain unclear. Here, we address this issue by presenting a quantitative model of cell lifespan and cell replicative capacity. The model is based on the relationship between cell mortality and metabolic rate, which is supported with data for different cell types from ectotherms and endotherms. These data indicate that much of the observed variation in cell lifespan and cell replicative capacity is explained by differences in cellular metabolic rate, and thus by the three primary factors that control metabolic rate: organism size, organism temperature and cell size. Individual cell lifespan increases as a power law with both body mass and cell mass, and decreases exponentially with increasing temperature. The replicative capacity of cells also increases with body mass, but is independent of temperature. These results provide a point of departure for future comparative studies of cell lifespan and replicative capacity in the laboratory and in the field.
Pseudosymmetry in a cyclopalladated compound
Authors: Raven William , Kalf Irmgard , Englert Ulli
Published: July 2012

The enantiomerically pure title complex, [SP-4-4]-(R)-[2-(1-aminoethyl)phenyl-κ2C1,N]chlorido(quinoline-κN)palladium(II) acetone hemisolvate, [Pd(C8H10N)Cl(C9H7N)]·0.5C3H6O, crystallizes with four molecules of the organopalladium complex and two molecules of acetone in the asymmetric unit. This corresponds to a discrete hydrogen-bonded aggregate and to the content of the unit cell in the space groupP1. Pronounced pseudo-inversion symmetry relates pairs of these objects in the asymmetric unit.
(1S)-1-Phenylethanaminium 4-{[(1S,2S)-1-hydroxy-2,3-dihydro-1H,1′H-[2,2′-biinden]-2-yl]methyl}benzoate
Authors: Frampton Christopher S. , Zhang Tao , Scalabrino Gaia A. , Frankish Neil , Sheridan Helen
Published: July 2012

The title molecular salt, C8H12N+·C26H21O3−, contains a dimeric indane pharmacophore that demonstrates potent anti-inflammatory activity. The indane group of the anion exhibits some disorder about the α-C atom, which appears common to many structures containing this group. A model to account for the slight disorder was attempted, but this was deemed unsuccessful because applying bond-length constraints to all the bonds about the α-C atom led to instability in the refinement. The absolute configuration was determined crystallographically asS,S,Sby anomalous dispersion methods with reference to both the Flack parameter and Bayesian statistics on Bijvoet differences. The configuration was also determined by ana prioriknowledge of the absolute configuration of the (1S)-1-phenylethanaminium counter-ion. The molecules pack in the crystal structure to form an infinite two-dimensional hydrogen-bond network in the (100) plane of the unit cell.
{1′-Phenyl-1′,2′,5′,6′,7′,7a'-hexahydrospiro[indeno[1,2-b]quinoxaline-11,3′-pyrrolizin]-2′-yl}(p-tolyl)methanone
Authors: Srinivasan T. , Suhitha S. , Purushothaman S. , Raghunathan R. , Velmurugan D.
Published: July 2012

In the title compound, C35H29N3O, the quinoxaline and indene systems are essentially planar, with maximum deviations of 0.047 (2) and 0.032 (2) Å for C atoms, respectively. The quinoxaline system forms a dihedral angle of 4.75 (3)° with the indene system. The pyrrolizine system is folded. The substituted five-membered ring adopts an envelope conformation. In the other five-membered ring, one C atom is disordered with a site-occupancy ratio of 0.676 (12):0.324 (12). In the crystal, molecules are linkedviaC—H...O hydrogen bonds involving the bifurcated carbonyl O atom.
2-[(2-Hydroxybenzyl)amino]pyrazinium perchlorate–2-[(pyrazin-2-ylamino)methyl]phenol (1/1)
Authors: Gao Shan , Ng Seik Weng
Published: July 2012

In the crystal structure of the title co-crystal, C11H12N3O+·ClO4−·C11H11N3O, the perchlorate ion is disordered about a twofold rotation axis with the Cl atom located on the twofold rotation axis; the 2-[(2-hydroxybenzyl)amino]pyrazinium cation and the neutral 2-[(pyrazin-2-ylamino)methyl]phenol molecule are disordered about the rotation axis in a 1:1 ratio. These two are connected by a pyrazine–pyrazine N1—H...N4hydrogen bond. The cation, whose two aromatic rings are twisted along the –CH2—NH– bond by 76.8 (1)°, is a hydrogen-bond donor to the perchlorate ion through the N atom of this link.
1-(5-Chloro-6-fluoro-1,3-benzothiazol-2-yl)hydrazine
Authors: Fun Hoong-Kun , Quah Ching Kheng , Sarojini B. K. , Mohan B. J. , Narayana B.
Published: July 2012

In the title compound, C7H5ClFN3S, the 1,3-benzothiazole ring system is nearly planar (r.m.s. deviation = 0.023 Å). In the crystal, molecules are linkedviaintermolecular N—H...N hydrogen bonds into a two-dimensional network parallel to (100).
2,4-Bis[(prop-2-ynyl)oxy]benzaldehyde
Authors: Esakkiammal M. , Selvarani V. , Neelakantan M. A. , Silambarasan V. , Velmurugan D.
Published: July 2012

In the title compound, C13H10O3, two prop-2-ynyloxy groups are attached to the benzaldehyde ring at positions 2 and 6. The crystal packing features C—H...O interactions.
Dicarbonyl(η5-cyclopentadienyl)(hexamethylenetetramine-κN1)iron(II) tetrafluoridoborate
Authors: M'thiruaine Cyprian M. , Friedrich Holger B. , Omondi Bernard
Published: July 2012

In the structure of the title compound, [Fe(C5H5)(C6H12N4)(CO)2]BF4, the arrangement around the FeIIatom corresponds to that of a three-legged piano stool. The cyclopentadienyl ligand occupies three coordination sites of the apical position in a η5fashion, while two CO ligands and one N atom of the hexamethylenetetramine ligand occupy the remaining coordination sites to complete a distorted octahedral geometry. The asymmetric unit consists of two sets of crystallographically independent cations and anions with the r.m.s. deviations of the overlay of non-H atoms of each pair being 0.081 and 0.120 Å, respectively. The Fe—N bond lengths are 2.0459 (15) and 2.0490 (14) Å, while the Fe—Cp(centroid) distances are 1.7257 (3) and 1.7246 (3) Å. One of the anions displays disorder, with the F atoms having occupancies of 0.58 (4) and 0.42 (4).
6-Oxo-1,6-dihydropyridazine-3-carbaldehyde monohydrate
Authors: Wang Lei
Published: July 2012

In the title hydrate, C5H4N2O2·H2O, the pyridazine ring is essentially planar, with an r.m.s. deviation of 0.0025 Å. In the crystal, O—H...O and N—H...O hydrogen bonds link the molecules into a one-dimensional chain.
Tetrakis(1,10-phenanthroline)bis(μ-pyridine-2,6-dicarboxylato)(pyridine-2,6-dicarboxylato)dicopper(II)terbium(III) nitrate tetrahydrate
Authors: Zhang Wei
Published: July 2012

The asymmetric unit of the title compound, [Cu2Tb(C7H3NO4)3(C12H8N2)4]NO3·4H2O, consists of one-half of theC2-symmetric trinuclear coordination cation, one-half of theC2-symmetric nitrate anion and two water molecules. In the coordination cation, the CuIIatom is coordinated by four N atoms from two 1,10-phenanthroline ligands and two O atoms from a bridging–chelating carboxylate group of the pyridine-2,6-dicarboxylate anion, completing a distorted N4O2octahedral coordination environment. The TbIIIatom, located on a twofold rotation axis, is nine-coordinated by three tridentate pyridine-2,6-dicarboxylate anions forming an N3O6donor set. The intramolecular Cu...Tb distance of 5.0592 (11) Å indicates weak interactions between the CuIIand TbIIIatoms. The coordination cations, nitrate anions and water molecules are connectedviaO—H...O hydrogen bonds into layers parallel to the (001) plane. Moreover, there are extensive π–π stacking interactions [centroid–centroid distances = 4.332 (7) and 3.878 (5) Å] between the phenanthroline ligands and between phenanthroline and pyridine-2,6-dicarboxylate ligands.
(S)-4-tert-Butyl-2-(1,2,3,4-tetrahydroisoquinolin-3-yl)-1,3-thiazole
Authors: Pawar Sunayna , Govender Thavendran , Kruger Hendrik G. , Maguire Glenn E. M.
Published: July 2012

In the title compound, C16H20N2S, a potential tetrahydroisoquinoline (TIQ) thiazole ligand, the N-containing six-membered ring of the TIQ unit adopts a half-chair conformation. There are four molecules in the asymmetric unit. No classical hydrogen bonds or π–π interactions were found in the crystal structure.
Bis(acetato-κO)bis(2-pyridinealdoxime-κ2N,N′)cadmium
Authors: Shirvan Sadif A. , Haydari Dezfuli Sara
Published: July 2012

In the title molecule, [Cd(CH3COO)2(C6H6N2O)2], the CdIIcation isN,N′-chelated by two 2-pyridinealdoxime ligands and coordinated by two acetate anions in a distorted octahedral geometry. The hydroxy groups of the 2-pyridinealdoxime ligands link to the acetate anionsviaintramolecular O—H...O hydrogen bonds. Weak intermolecular C—H...O hydrogen bonds occur in the crystal.
N-[4-(4-Nitrophenoxy)phenyl]acetamide
Authors: Nigar Asifa , Akhter Zareen , Tahir M. Nawaz
Published: July 2012

The asymmetric unit of the title compound, C14H12N2O4, contains two molecules that differ principally in the orientation of the acetamide substituent to the adjacent benzene ring with dihedral angles of 44.77 (7) and 19.06 (7)°. The dihedral angles between the benzene rings are 64.46 (4) and 80.84 (4)°. In the crystal, classical N—H...O hydrogen bonds formC(4) chains along [100]. These chains are interlinked by C—H...O contacts formingR22(10) rings. In the crystal, π–π interactions are observed with a distance of 3.5976 (18) Å between the centroids of the nitro-substituted benzene rings of one type of molecule.
Methyl 4-[N-(5-bromopyrimidin-2-yl)carbamoyl]benzoate
Authors: Hu Hui-Ling , Wu Chia-Jun , Yeh Chun-Wei , Chen Jhy-Der
Published: July 2012

In the title compound, C13H10BrN3O3, the pyrimidine and benzene rings are twisted with an interplanar angle of 58.4 (1)°. The secondary amide group adopts acisconformation with an H—N—C—O torsion angle of 14.8 (1)°. In the crystal, molecules are connected into inversion dimersviapairs of N—H...N hydrogen bonds, generating anR22(8) motif. The dimers are further connected through a C—Br...O interaction [3.136 (1) Å and 169.31 (1)°] into a chain along [110]. Weak C—H...N hydrogen bonds between the methyl benzoate groups and pyrimidine rings are also observed in the crystal structure.
5-Bromo-3-(3-fluorophenylsulfinyl)-2-methyl-1-benzofuran
Authors: Choi Hong Dae , Seo Pil Ja , Lee Uk
Published: July 2012

In the title compound, C15H10BrFO2S, the 3-fluorophenyl ring makes a dihedral angle of 85.0 (1)° with the mean plane [r.m.s. deviation = 0.008 (2) Å] of the benzofuran fragment. In the crystal, molecules are linked by weak C—H...O hydrogen bonds and a Br...O contact [3.200 (3) Å]. The crystal structure also exhibits slipped π–π interactions between the benzene and furan rings of neighbouring molecules [centroid–centroid distance = 3.619 (4) Å and slippage of 1.389 (4) Å]. In the 3-fluorophenyl ring, the F atom is disordered over two positions with site-occupancy factors of 0.583 (5) and 0.417 (5).
Hydrogen measurements using new temperature-programmed desorption mass spectrometry system with double cryopanel-attached quadrupole mass spectrometers
Authors: Higashi Yasuhiro , Fujimoto Norihiro , Saito Hiroyuki , Sawada Takashi
Published: July 2012

The authors developed a temperature-programmed desorption mass spectrometry system equipped with two quadrupole mass spectrometers (QMSs) positioned in the line and out of the line of sight for a sample, respectively. This enables us to directly compare and discuss detection efficiencies and limits of detection of a gas species due to the QMS positions in the same desorption at the same time. Cryopanels are attached to cover the QMS heads, which function as cold traps to decrease interference from unexpected gas species, especially for eliminating the effect of water on hydrogen measurement. The authors evaluated and compared detection efficiencies during hydrogen measurements at room temperature and 50 K using standard hydrogen ion-implanted samples. The cold measurements enhanced detection efficiencies of hydrogen at both QMS positions since ionization efficiencies increased as a result of lowered velocity of the hydrogen molecules after collision with the cryopanels. The authors measured hydrogen content in a steel sample after immersion in an ammonium thiocyanate aqueous solution. The elimination of water effectively resulted in high signal-to-background ratios, which led to low limits of detection and quantitation of hydrogen, rather than enhancement in detection efficiencies.
Resonant modes of a constricted annular resonator
Authors: Lin Hsaio-Tseng , Choe Yun , Muehleisen Ralph T. , Atchley Anthony A.
Published: July 2012

One topic of current interest in thermoacoustic research is an annular prime mover [Lin et al., J. Acoust. Soc. Am. 100, 2846(A) (1996)]. The starting point for this research is an investigation of a constricted annular resonator. A literature search of the field resulted in surprisingly few references. The results of analytic, numerical, and experimental investigations are presented. It was found that introducing a constriction to an annular resonator split each longitudinal duct mode into two modes, one of a higher frequency with a pressure antinode at the constriction, and one at a lower frequency with a velocity antinode near the constriction. While changing the size of the constriction appreciably modified the lower resonance frequency and the position of the velocity antinode, the upper resonance frequency was only moderately modified and the position of the pressure antinode was virtually fixed. [Work supported by the Office of Naval Research and the American Society for Engineering Education.]
Environmentally sensitive adaptive fluctuation-based processing
Authors: Wagstaff Ronald A. , Mobbs Jackson A.
Published: July 2012

Signals that propagate from submerged sources to submerged receivers in the ocean generally interact less with the fluctuation generation mechanisms near the sea surface, e.g., internal and sea-surface waves, than signals originating near the surface, e.g., surface ship clutter and sea-surface noise. Therefore, submerged source signals generally have smaller fluc- tuations than clutter signals and noise. The differences in amplitudes of fluctuations have been used to devise a class of signal processing algorithms that provides preferential gains for signals having fluctuation amplitudes less than those of clutter and noise. Gains include increases in signal-to-noise ratio, clutter suppression, and unalerted automatic detection. The AWSUM filter is an example of such a processor [R. A. Wagstaff, IEEE J. Oceanic Eng. 22(1) (1997)]. Similar gains can be achieved by exploiting the order dependence of fluctuation amplitudes. By combining amplitude dependence and order dependence, an algorithm has been devised that is both sensitive to fluctuations and adapts to the input data. The resulting algorithm is designated the AWSUM Environmentally Sensitive Adaptation (ESA). The AWSUM ESA algorithm is described and results from processing real data are presented. [Work supported by ONR and NRL.]
Fluctuation-based beamformer for the enhancement of low-fluctuation amplitude signals
Authors: Wagstaff Ronald A.
Published: July 2012

A formulation of the cross-spectral density matrix (CSDM, also known as the data covariance matrix) is presented, which is sensitive to the fluctuations that occur naturally in undersea acoustic data. This new formulation, called the AWSUMk cross-spectral density matrix or AkCSDM, is patterned after the WISPR and AWSUM filters, both of which are sensitive to amplitude fluctuations. The AkCSDM utilizes a similar approach to achieving sensitivity to fluctuations, but AkCSDM goes a step further by including sensitivity to phase fluctuations as well as amplitude fluctuations. The formulation is described and results are presented for beamforming the elements of a towed horizontal line array. The results indicate that in the case of a low-fluctuation amplitude tonal, the signal-to-noise-ratio of the AkCSDM beamformer is much greater than the conventional CSDM beamformer, and that in some cases the noise and clutter signals were nearly eliminated. Such results suggest that ‘‘noise elimination’’ is a better description of the AkCSDM beamformer than is ‘‘noise suppression.’’ [Work supported by ONR and NRL.]
Space-time dynamic focusing from axisymmetric planar radiators with transient excitations: Localized waves
Authors: Sun Jie , Stepanishen Peter R.
Published: July 2012

A geometric space-time approach to evaluate the on-axis response is developed for axisymmetric planar radiators with pulsed transient excitations. The approach is based on combining the Rayleigh time-dependent surface integral with a simple geometric focusing method. The acoustic field at the pulse center is simply related to the source signal or aperture distribution along a focusing line in the space-time domain. This space-time dynamic focusing approach is used to explain the behavior of localized wave solutions to the free-space scalar wave equation. As examples, two different types of localized wave fields are investigated. The characteristics of the space-time source distributions are connected to the on-axis acoustic field and energy distribution pattern, using the space-time dynamic focusing approach. Numerical results are presented to show both the source signals and the resulting acoustic fields for the localized waves. [Work supported by URI/Ocean Technology Center.]
Transient axisymmetric response of a finite cylindrical shell with internal fluid loading. Part 1. Theory and numerical results
Authors: Hassan Scott E. , Stepanishen Peter R.
Published: July 2012

A general approach to evaluate the transient response of finite length shells with internal fluid loading is addressed. As a special case the axisymmetric response of a cylindrical shell with a base plate at one end and internal fluid loading is investigated. The velocity field of the shell is expressed as an in-vacuo eigenvector expansion and the pressure field in the fluid is expressed using a Green’s function for the mixed boundary value problem. The unknown time-dependent modal velocity amplitudes are formulated as a set of coupled convolution integral equations where the time-dependent fluid loading on the shell and base plate is included using an impulse response approach. In-vacuo and fluid-loaded results will be presented for the special case of a transient point force excitation applied to the base plate. The influence of fluid loading on the shell and base plate will be discussed in detail.
Ultra-wideband filter for noise control
Authors: Kushwaha M. S. , Halevi P.
Published: July 2012

It is proposed that arrays of periodically positioned metallic bars could serve as a low-tech, low-cost, and effective device for filtering out environmental or industrial noise. The proposed scheme is composed of five sets of periodic arrays in tandem, each characterized by a certain value of the period (of square lattice) a and cylinders of radius r; the filling fraction is f=(r2/a2). The purpose of the tandem structure is to achieve an ultra-wideband filter of noise. The tandem structure is designed such that, for certain values of the period, the stop bands of the respective sets of structure superimpose over one another. It is found that, for f=0.55, the tandem structure should shield from noise in the entire range between 2.0 and 11.0 kHz. This is attributed to the formation of a ‘‘super stop band’’ due to overlapping of the five individual stop bands. An ultra-wideband filter for environmental or industrial noise could thus be fabricated according to the specific requirements. This idea is based on the band structure calculations reported in the preceding abstract.