bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron-ion dissociative recombination rate constants relevant to the Titan atmosphere and the Interstellar Medium
Authors: Osborne David , Lawson Patrick , Adams Nigel
Published: January 2014

Following the arrival of Cassini at Titan in 2004, the Titan atmosphere has been shown to contain large complex polycyclic-aromatic hydrocarbons. Since Cassini has provided a great deal of data, there exists a need for kinetic rate data to help with modeling this atmosphere. One type of kinetic data needed is electron-ion dissociative recombination (e-IDR) rate constants. These data are not readily available for larger compounds, such as naphthalene, or oxygen containing compounds, such as 1,4 dioxane or furan. Here, the rate constants for naphthalene, 1,4 dioxane, and furan have been measured and their temperature dependencies are determined when possible, using the University of Georgia's Variable Temperature Flowing Afterglow. The rate constants are compared with those previously published for other compounds; these show trends which illustrate the effects which multi-rings and oxygen heteroatoms substitutions have upon e-IDR rate constants.
Unified view on linear response of interacting identical and distinguishable particles from multiconfigurational time-dependent Hartree methods
Authors: Alon Ofir E. , Streltsov Alexej I. , Cederbaum Lorenz S.
Published: January 2014

A unified view on linear response of interacting systems utilizing multiconfigurational time-dependent Hartree methods is presented. The cases of one-particle and two-particle response operators for identical particles and up to all-system response operators for distinguishable degrees-of-freedom are considered. The working equations for systems of identical bosons and identical fermions, as well for systems of distinguishable particles are explicitly derived. These linear-response theories – applicable for discrete excitation spectra – provide numerically exact excitation energies and system's properties, when numerical convergence is achieved in the calculations.
The isotropic-nematic and nematic-nematic phase transition of binary mixtures of tangent hard-sphere chain fluids: An analytical equation of state
Authors: van Westen Thijs , Vlugt Thijs J. H. , Gross Joachim
Published: January 2014

An analytical equation of state (EoS) is derived to describe the isotropic (I) and nematic (N) phase of linear- and partially flexible tangent hard-sphere chain fluids and their mixtures. The EoS is based on an extension of Onsager's second virial theory that was developed in our previous work [T. van Westen, B. Oyarzún, T. J. H. Vlugt, and J. Gross, J. Chem. Phys. 139, 034505 (2013)]. Higher virial coefficients are calculated using a Vega-Lago rescaling procedure, which is hereby generalized to mixtures. The EoS is used to study (1) the effect of length bidispersity on the I-N and N-N phase behavior of binary linear tangent hard-sphere chain fluid mixtures, (2) the effect of partial molecular flexibility on the binary phase diagram, and (3) the solubility of hard-sphere solutes in I- and N tangent hard-sphere chain fluids. By changing the length bidispersity, two types of phase diagrams were found. The first type is characterized by an I-N region at low pressure and a N-N demixed region at higher pressure that starts from an I-N-N triphase equilibrium. The second type does not show the I-N-N equilibrium. Instead, the N-N region starts from a lower critical point at a pressure above the I-N region. The results for the I-N region are in excellent agreement with the results from molecular simulations. It is shown that the N-N demixing is driven both by orientational and configurational/excluded volume entropy. By making the chains partially flexible, it is shown that the driving force resulting from the configurational entropy is reduced (due to a less anisotropic pair-excluded volume), resulting in a shift of the N-N demixed region to higher pressure. Compared to linear chains, no topological differences in the phase diagram were found. We show that the solubility of hard-sphere solutes decreases across the I-N phase transition. Furthermore, it is shown that by using a liquid crystal mixture as the solvent, the solubility difference can by maximized by tuning the composition. Theoretical results for the Henry's law constant of the hard-sphere solute are in good agreement with the results from molecular simulation.
Size exclusion deep bed filtration: Experimental and modelling uncertainties
Authors: Badalyan Alexander , You Zhenjiang , Aji Kaiser , Bedrikovetsky Pavel , Carageorgos Themis , Zeinijahromi Abbas
Published: January 2014

A detailed uncertainty analysis associated with carboxyl-modified latex particle capture in glass bead-formed porous media enabled verification of the two theoretical stochastic models for prediction of particle retention due to size exclusion. At the beginning of this analysis it is established that size exclusion is a dominant particle capture mechanism in the present study: calculated significant repulsive Derjaguin-Landau-Verwey-Overbeek potential between latex particles and glass beads is an indication of their mutual repulsion, thus, fulfilling the necessary condition for size exclusion. Applying linear uncertainty propagation method in the form of truncated Taylor's series expansion, combined standard uncertainties (CSUs) in normalised suspended particle concentrations are calculated using CSUs in experimentally determined parameters such as: an inlet volumetric flowrate of suspension, particle number in suspensions, particle concentrations in inlet and outlet streams, particle and pore throat size distributions. Weathering of glass beads in high alkaline solutions does not appreciably change particle size distribution, and, therefore, is not considered as an additional contributor to the weighted mean particle radius and corresponded weighted mean standard deviation. Weighted mean particle radius and LogNormal mean pore throat radius are characterised by the highest CSUs among all experimental parameters translating to high CSU in the jamming ratio factor (dimensionless particle size). Normalised suspended particle concentrations calculated via two theoretical models are characterised by higher CSUs than those for experimental data. The model accounting the fraction of inaccessible flow as a function of latex particle radius excellently predicts normalised suspended particle concentrations for the whole range of jamming ratios. The presented uncertainty analysis can be also used for comparison of intra- and inter-laboratory particle size exclusion data.
An in situ platform for the investigation of Raman shift in micro-scale silicon structures as a function of mechanical stress and temperature increase
Authors: Gan Ming , Tomar Vikas
Published: January 2014

Raman spectroscopy provides an accurate approach to measure temperature and stress in semiconductors at micro-scale and nano-scale. In the present work an in situ experimentation-based approach to separate a measured room to high temperature Raman shift signal into mechanical and thermal components when a uniaxial compressive load is applied in situ is presented. In situ uniaxial compressive loads were applied on examined silicon cantilever specimens from room temperature to 150 °C. The Raman shift measurements were performed as a function of strain at constant temperature and as a function of temperature at constant strain levels. The results show that the Raman shift measured at a given temperature under a given level of applied stress can be expressed as a summation of stress-induced Raman shift signal and temperature-induced Raman shift signal measured separately. For silicon, the stress-induced Raman shift is caused by inelastic interaction between the incident laser and the vibration of crystal lattice, while the temperature-induced Raman shift is caused by the anharmonic terms in the vibrational potential energy. Analyses indicate that such separation of Raman shift signal can be used to measure localized change in thermal conductivity and mechanical stress of semiconductor structures under applied stress.
The nucleation process and the roles of structure and density fluctuations in supercooled liquid Fe
Authors: Li Rong , Wu Yongquan , Xiao Junjiang
Published: January 2014

We observed homogeneous nucleation process of supercooled liquid Fe by molecular dynamics simulations. Using bond-orientational order parameters together with Voronoi polyhedron method, we characterized local structure, calculated the volume of Voronoi polyhedra of atoms and identified the structure and density fluctuations. We monitored the formation of nucleus and analyzed its inner structure. The birth and growth of the pre-nucleus and nucleus are accompanied with aggregating and disaggregating processes in the time scale of femtosecond. Only the initial solid-like clusters (ISLC), ranging from 1 to 7 atoms, pop up directly from liquid. The relation between the logarithm of number of clusters and the cluster size was found to be linear for ISLCs and was observed to be parabolic for all solid-like clusters (SLC) due to aggregating and disaggregating effects. The nucleus and pre-nuclei mainly consist of body centered cubic (BCC) and hexagonal close packed atoms, while the BCC atoms tend to be located at the surface. Medium-range structure fluctuations induce the birth of ISLCs, benefit the aggregation of embryos and remarkably promote the nucleation. But density fluctuations contribute little to nucleation. The lifetime of most icosahedral-like atoms (ICO) is shorter than 0.7 ps. No obvious relationship was found between structure/density fluctuations and the appearance of ICO atoms.
Modeling of soft interfacial volume fraction in composite materials with complex convex particles
Authors: Xu Wenxiang , Chen Wen , Chen Huisu
Published: January 2014

The influence of the soft interfacial volume fraction on physical properties of composite materials has been found to be significant. However, the soft interfacial volume fraction is difficultly determined by traditional experimental methods and simple models proposed so far. This article addresses the problem by means of theoretical and numerical approaches that start at a microscopic scale of composite materials, which are regarded as a three-phase composite structure with polydisperse convex particles, soft interfaces, and a matrix. A theoretical scheme for the soft interfacial volume fraction is proposed by a theory of the nearest-surface distribution functions and geometrical configurations of polydisperse convex particles. The theoretical scheme represents a generalized model for the soft interfacial volume fraction in that it cannot only determine the interfacial volume fraction around convex polyhedral particles but also to derive that around ellipsoidal and spherical particles. In order to test the theoretical scheme, a numerical model that adopts the three-phase composite structure and a numerical Monte Carlo integration scheme is presented. Also, theoretical and numerical results of the soft interfacial volume fraction around ellipsoidal and spherical particles in the literature are further compared. By way of application, it is shown that the developed model provides a quantitative means to evaluate the dependence of the soft interfacial volume fraction on various factors, such as geometrical configurations of particles and the interfacial thickness.
Vibronic structure of VO2 probed by slow photoelectron velocity-map imaging spectroscopy
Authors: Kim Jongjin B. , Weichman Marissa L. , Neumark Daniel M.
Published: January 2014

We report high-resolution anion photoelectron spectra of vanadium dioxide (VO2−) obtained by slow electron velocity-map imaging of trapped and cryogenically cooled anions. Vibrationally resolved spectra are obtained for photodetachment to the first three neutral electronic states, giving an electron affinity of 1.8357(5) eV for the $\tilde X\,{}^2A_1 $X̃A12 ground state and term energies of 0.1845(8) eV and 0.8130(5) eV for the $\tilde A\,{}^2B_1 $ÃB12 and $\tilde B\,{}^2A_1 $B̃A12 excited states, respectively. The vibrational fundamentals ν1 and ν2 are obtained for all three states. Experimental assignments are confirmed by energies from electronic structure calculations and Franck-Condon spectral simulations. These simulations support assigning the anion ground state as the $\tilde X\,{}^3B_1 $X̃B13 state. With this assignment, photodetachment to the $\tilde B\,{}^2A_1 $B̃A12 state involves a nominally forbidden two-electron transition, suggesting extensive configuration interaction in neutral VO2.
Pore-scale dynamics of salt transport and distribution in drying porous media
Authors: Shokri Nima
Published: January 2014

Understanding the physics of water evaporation from saline porous media is important in many natural and engineering applications such as durability of building materials and preservation of monuments, water quality, and mineral-fluid interactions. We applied synchrotron x-ray micro-tomography to investigate the pore-scale dynamics of dissolved salt distribution in a three dimensional drying saline porous media using a cylindrical plastic column (15 mm in height and 8 mm in diameter) packed with sand particles saturated with CaI2 solution (5% concentration by mass) with a spatial and temporal resolution of 12 μm and 30 min, respectively. Every time the drying sand column was set to be imaged, two different images were recorded using distinct synchrotron x-rays energies immediately above and below the K-edge value of Iodine. Taking the difference between pixel gray values enabled us to delineate the spatial and temporal distribution of CaI2 concentration at pore scale. Results indicate that during early stages of evaporation, air preferentially invades large pores at the surface while finer pores remain saturated and connected to the wet zone at bottom via capillary-induced liquid flow acting as evaporating spots. Consequently, the salt concentration increases preferentially in finer pores where evaporation occurs. Higher salt concentration was observed close to the evaporating surface indicating a convection-driven process. The obtained salt profiles were used to evaluate the numerical solution of the convection-diffusion equation (CDE). Results show that the macro-scale CDE could capture the overall trend of the measured salt profiles but fail to produce the exact slope of the profiles. Our results shed new insight on the physics of salt transport and its complex dynamics in drying porous media and establish synchrotron x-ray tomography as an effective tool to investigate the dynamics of salt transport in porous media at high spatial and temporal resolution.
UV resonance Raman analysis of trishomocubane and diamondoid dimers
Authors: Meinke Reinhard , Richter Robert , Merli Andrea , Fokin Andrey A. , Koso Tetyana V. , Rodionov Vladimir N. , Schreiner Peter R. , Thomsen Christian , Maultzsch Janina
Published: January 2014

We present resonance Raman measurements of crystalline trishomocubane and diamantane dimers containing a C=C double bond. Raman spectra were recorded with excitation energies between 2.33 eV and 5.42 eV. The strongest enhancement is observed for the C=C stretch vibration and a bending mode involving the two carbon atoms of the C=C bond, corresponding to the B2g wagging mode of ethylene. This is associated with the localization of the π-HOMO and LUMO and the elongation of the C=C bond length and a pyramidalization of the two sp2-hybridized carbon atoms at the optical excitation. The observed Raman resonance energies of the trishomocubane and diamantane dimers are significantly lower than the HOMO-LUMO gaps of the corresponding unmodified diamondoids.
State-to-state dynamics of the H*(n) + HD → D*(n′) + H2 reactive scattering
Authors: Yu Shengrui , Su Shu , Dai Dongxu , Yuan Kaijun , Yang Xueming
Published: January 2014

The state-to-state dynamics of the H*(n) + HD → D*(n′) + H2 reactive scattering at the collision energy of 0.5 eV have been carried out for the first time by using H-atom Rydberg tagging time-of-flight technique. Experimental results show that the angular distribution of the total H2 products presents clearly forward-backward asymmetric, which considerably differs from that of the corresponding H+ + HD → D+ + H2 reaction predicted by previously theoretical calculations. Such disagreement between these two processes suggests that the Fermi independent-collider model is also not valid in describing the dynamics of isotopic variants of the H* + H2 reaction. The rotational state distribution of the H2 products demonstrates a saw-toothed distribution with odd-j′ > even-j′. This interesting observation is strongly influenced by nuclear spin statistics.
Low-density InP-based quantum dots emitting around the 1.5 μm telecom wavelength range
Authors: Yacob M. , Reithmaier J. P. , Benyoucef M.
Published: January 2014

The authors report on low-density InAs quantum dots (QDs) grown on AlGaInAs surfaces lattice matched to InP using post-growth annealing by solid-source molecular beam epitaxy. Clearly spatially separated QDs with a dot density of about 5 × 108 cm−2 are obtained by using a special capping technique after the dot formation process. High-resolution micro-photoluminescence performed on optimized QD structures grown on distributed Bragg reflector exhibits single QD emissions around 1.5 μm with narrow excitonic linewidth below 50 μeV, which can be used as single photon source in the telecom wavelength range.
Chaotic vibrations of the duffing system with fractional damping
Authors: Syta Arkadiusz , Litak Grzegorz , Lenci Stefano , Scheffler Michael
Published: January 2014

We examined the Duffing system with a fractional damping term. Calculating the basins of attraction, we demonstrate a broad spectrum of non-linear behaviour connected with sensitivity to the initial conditions and chaos. To quantify dynamical response of the system, we propose the statistical 0-1 test as well as the maximal Lyapunov exponent; the application of the latter encounter a few difficulties because of the memory effect due to the fractional derivative. The results are confirmed by bifurcation diagrams, phase portraits, and Poincaré sections.
Precise parameter extraction technique for organic thin-film transistors operating in the linear regime
Authors: Marinov Ognian , Jamal Deen M. , Feng Cong , Wu Yiliang
Published: January 2014

We demonstrate a precise parameter extraction for organic thin-film transistors (OTFTs) operating in the linear regime. The precision is achieved by utilizing the mathematical functions YVG and HVG that are derived from measured current-voltage (I–V) characteristics, in a proper sequence. The YVG function compensates for the impact of the contact resistance Rc on the I–V characteristics of the OTFT. The HVG function applied on the YVG function is used to determine the mobility enhancement factor γ > 0, which allows for defining the γYVG function for OTFT that is linearly proportional to the gate-overdrive voltage (VG–VT). The linearity of the γYVG function allows for extraction of the threshold voltage VT and the mobility μ in the OTFT. Using the extracted parameters, the reduction of the experimental data for drain-source resistance with the resistance model for the intrinsic channel allows for accurate determination of RC. The precision of the extraction technique is verified by re-simulation that uses the extracted values of the parameters, and the re-simulation accurately replicates the measurement of the current and the transconductance of the OTFT.
Temperature dependence of the transverse piezoelectric coefficient of thin films and aging effects
Authors: Rossel C. , Sousa M. , Abel S. , Caimi D. , Suhm A. , Abergel J. , Le Rhun G. , Defay E.
Published: January 2014

We present a technique to measure the temperature dependence of the transverse piezoelectric coefficient e31,f of thin films of lead zirconate titanate (PZT), aluminum nitride, and BaTiO3 deposited on Si wafers. It is based on the collection of electric charges induced by the deflection of a Si cantilever coated with the piezoelectric film. The aim of this work is to assess the role of temperature in the decay of the remnant polarization of these materials, in particular, in optimized gradient-free PZT with composition PbZr0.52Ti0.48O3. It is found that in contrast to theoretical predictions, e31,f decreases with temperature because of the dominance of relaxation effects. The observation of steps in the logarithmic aging decay law is reminiscent of memory effects seen in frustrated spin glasses.
Switching at small magnetic fields in Josephson junctions fabricated with ferromagnetic barrier layers
Authors: Abd El Qader Makram , Singh R. K. , Galvin Sarah N. , Yu L. , Rowell J. M. , Newman N.
Published: January 2014

Nb-based Josephson junctions have been fabricated, which can select one of two states depending on the relative magnetization of their ferromagnetic barrier layers. To minimize the free-layer switching energy, while maintaining adequate thermal stability at 4.2 K, a dilute Cu-permalloy alloy [Cu0.7(Ni80Fe20)0.3] with a low magnetic saturation (Ms ∼ 80 emu/cm3) is used. The optimal thickness of the permalloy (Ni80Fe20) fixed-layer is shown to be 2.4 nm. Such devices exhibit switching at magnetic fields as low as 5 Oe, demonstrating their potential use in low power non-volatile memory for superconductor digital circuits.
Ultrafast carrier dynamics in CuInS2 quantum dots
Authors: Sun Jianhui , Zhu Dehua , Zhao Jialong , Ikezawa Michio , Wang Xiuying , Masumoto Yasuaki
Published: January 2014

The ultrafast carrier dynamics in CuInS2 (CIS) quantum dots (QDs) was studied by means of femtosecond transient absorption (TA) spectroscopy. The size-dependent 1S transition energy determined from bleaching spectra is in agreement with that calculated on the finite-depth-well model in the effective mass approximation. The TA bleaching comes from filling of electron quantized levels, allowing us to know the dynamics of the 1S electron in CIS QDs. The sub-100-ps electron trapping at surface defects in bare QDs accelerates with decreasing QD size, while is effectively suppressed in well-passivated CIS/ZnS core/shell QDs.
Enhanced coherent extreme ultraviolet emission through high order harmonic generation from plasma plumes containing nanoparticles
Authors: Singhal H. , Naik P. A. , Kumar M. , Chakera J. A. , Gupta P. D.
Published: January 2014

A new method to calculate the high order harmonic generation from the interaction of ultra-short laser pulses with plasma plumes containing solid nanoparticles has been presented. It is shown that enhancement for a particular harmonic order is almost independent of the nanoparticle size, in agreement with the observed experimental results which are not explainable by the existing theories applicable to high order harmonic generation from gases or gas clusters.
Dispersion retrieval from multi-level ultra-deep reactive-ion-etched microstructures for terahertz slow-wave circuits
Authors: Baik Chan-Wook , Young Ahn Ho , Kim Yongsung , Lee Jooho , Hong Seogwoo , Hee Choi Jun , Kim Sunil , Hun Lee Sang , Yeon Jun So , Yu SeGi , Lawrence Ives R. , Min Kim Jong , Hwang Sungwoo
Published: January 2014

A multi-level microstructure is proposed for terahertz slow-wave circuits, with dispersion relation retrieved by scattering parameter measurements. The measured return loss shows strong resonances above the cutoff with negligible phase shifts compared with finite element analysis. Splitting the circuit into multi levels enables a low aspect ratio configuration that alleviates the loading effect of deep-reactive-ion etching on silicon wafers. This makes it easier to achieve flat-etched bottom and smooth sidewall profiles. The dispersion retrieved from the measurement, therefore, corresponds well to the theoretical estimation. The result provides a straightforward way to the precise determination of dispersions in terahertz vacuum electronics.
Controlled switching of ultrafast circular polarization oscillations in spin-polarized vertical-cavity surface-emitting lasers
Authors: Höpfner Henning , Lindemann Markus , Gerhardt Nils C. , Hofmann Martin R.
Published: January 2014

We demonstrate a scheme for controlled switching of polarization oscillations in spin-polarized vertical-cavity surface-emitting lasers (spin-VCSEL). Under hybrid electrical and optical pumping conditions, our VCSEL devices show polarization oscillations with frequencies far above the VCSEL's electrical modulation bandwidth. Using multiple optical pulses, we are able to excite and amplify these polarization oscillations. When specific phase and amplitude conditions for the optical excitation pulses are met, destructive interference leads to switch-off of the polarization oscillation, enabling the generation of controlled short polarization bursts.
Giant magnetocaloric and magnetoresistance effects in ferrimagnetic Mn1.9Co0.1Sb alloy
Authors: Ma S. C. , Hou D. , Gong Y. Y. , Wang L. Y. , Huang Y. L. , Zhong Z. C. , Wang D. H. , Du Y. W.
Published: January 2014

Magnetic and transitional behaviors are investigated in Mn1.9Co0.1Sb intermetallic compound. Mn2Sb is a simple ferrimagnet with Neel temperature around 550 K. The Co-introduction results in the appearance of antiferromagnetic state, and therefore, the first-order magnetic transition occurs between antiferromagnetic and ferrimagnetic state, which can be induced by temperature/magnetic field, in Mn1.9Co0.1Sb alloy. Accordingly, a magnetic entropy change as high as 5 J kg−1 K−1 and a large magnetoresistance of 46% under the field change of 10 and 50 kOe are achieved, respectively.
Voltage calibration of luminescence images of silicon solar cells
Authors: Höffler Hannes , Al-Mohtaseb Hasan , Haunschild Jonas , Michl Bernhard , Kasemann Martin
Published: January 2014

A variety of methods extracting spatially resolved information of solar cell parameters using luminescence imaging on silicon solar cells have been introduced in the past years. Nearly, all methods base on calibrating the local luminescence intensity to local junction voltage. The different methods, however, use different approaches to calibrate the luminescence images to local junction voltage. The assumptions made by the voltage calibration approaches are fundamental for a correct voltage calibration and hence for a correct extraction of other relevant local solar cell parameters. In this work, we review the different voltage calibration approaches and analyse the validity and the effect of the underlying assumptions carefully using circuit simulation results. We present experimental results of voltage calibrated luminescence images of a multicrystalline silicon solar cell using different voltage calibration approaches. We show the relevance of accurate voltage calibration by performing a sensitivity analysis investigating the sensitivity of local cell parameter results obtained by a method known from literature with respect to changes in the calibration constant. We conclude proposing an approach for voltage calibration which is the most reasonable trade-off between accuracy and sufficiently low data acquisition times.
Curling probe measurement of electron density in pulse-modulated plasma
Authors: Pandey Anil , Sakakibara Wataru , Matsuoka Hiroyuki , Nakamura Keiji , Sugai Hideo
Published: January 2014

The electron density ne of stationary plasma can be easily obtained on the basis of the resonance frequency f of a curling probe (CP) measured by a network analyzer (NWA). However, in pulsed plasma with discharge period T, the ne and f values periodically change with time. This study extends the conventional CP technique to a time-resolved measurement of the pulse-modulated electron density. The condition necessary for the measurement is revealed to be synchronization of NWA with the pulse modulation, which is expressed as (n − 1)T/TSWP = integer (1, 2, …) for a number n of data point and sweep time TSWP.
Effects of amendment of different biochars on soil carbon mineralisation and sequestration
Authors: Ouyang Lei , Yu Liuqian , Zhang Renduo
Published: January 2014

The aim of this study was to determine the impact of addition of different biochars on soil carbon mineralisation and sequestration. Different biochars were produced from two types of feedstock, fresh dairy manure and pine tree woodchip, each of which was pyrolysed at 300, 500, and 700°C. Each biochar was mixed at 5% (w/w) with a forest loamy soil and the mixture was incubated at 25°C for 180 days, during which soil physicochemical properties and soil carbon mineralisation were measured. Results showed that the biochar addition increased soil carbon mineralisation at the early stage (within the first 15 days) because biochar brought available organic carbon to the soil and changed associated soil properties, such increasing soil pH and microbial activity. The largest increase in soil carbon mineralisation at the beginning of incubation was induced by the dairy manure biochar pyrolysed at 300°C. Soil carbon mineralisation was enhanced more significantly by the dairy manure biochars than by the woodchip biochars, and the enhancement effect decreased with increasing pyrolysis temperature. Although the biochar addition induced increased soil carbon mineralisation at the beginning of the incubation, soil carbon mineralisation rates decreased sharply within a short time (within 15 days) and then remained very low afterwards. Carbon mineralisation kinetic modelling indicated that the stable organic matter in biochars could be sequestrated in soil for a long time and resulted in high levels of carbon sequestration, especially for the woodchip biochars pyrolysed from higher temperatures.
An RNAi screen for Aire cofactors reveals a role for Hnrnpl in polymerase release and Aire-activated ectopic transcription
Authors: Giraud Matthieu , Jmari Nada , Du Lina , Carallis Floriane , Nieland Thomas J. F. , Perez-Campo Flor M. , Bensaude Olivier , Root David E. , Hacohen Nir , Mathis Diane , Benoist Christophe
Published: January 2014

Significance

The transcription factor Aire controls an unusual mode of transcriptional regulation, important to establish immune tolerance to self, which allows the ectopic expression in the thymic epithelium of RNA transcripts normally restricted to defined tissues. Through a genome-scale RNAi, we identify 51 functional partners of Aire, reaffirming a role for Aire in unleashing stalled transcription, interestingly through involvement of RNA processing factors.
ULASJ1234+0907: the reddest type 1 quasar at
z = 2.5
revealed in the X-ray and far-infrared
Authors: Banerji Manda , Fabian A. C. , McMahon R. G.
Published: January 2014

We present Herschel and XMM–Newton observations of ULASJ1234+0907 (z = 2.503), the reddest broad-line type 1 quasar currently known with (i − K)AB > 7.1. Herschel observations indicate that the quasar host is a hyperluminous infrared galaxy with a total infrared luminosity of log10(LIR/L⊙) = 13.90 ± 0.02. A greybody fit gives a dust temperature of Td = 60 ± 3 K assuming an emissivity index of β = 1.5, considerably higher than in submillimeter bright galaxies observed at similar redshifts. The star formation rate is estimated to be >2000 M⊙ yr−1 even accounting for a significant contribution from an active galactic nucleus (AGN) component to the total infrared luminosity or requiring that only the far-infrared luminosity is powered by a starburst. XMM–Newton observations constrain the hard X-ray luminosity to be L2-10 keV = 1.3 × 1045 erg s−1, putting ULASJ1234+0907 among the brightest X-ray quasars known. Through very deep optical and near-infrared imaging of the field at subarcsecond seeing, we demonstrate that despite its extreme luminosity, it is highly unlikely that ULASJ1234+0907 is being lensed. We measure a neutral hydrogen column density of NH = 9.0 × 1021 cm−2 corresponding to AV ∼ 6. The observed properties of ULASJ1234+0907 – high luminosity and Eddington ratio, broad lines, moderate column densities and significant infrared emission from reprocessed dust – are similar to those predicted by galaxy formation simulations for the AGN blowout phase. The high Eddington ratio, combined with the presence of significant amounts of dust, is expected to drive strong outflows due to the effects of radiation pressure on dust.
Determinants of expression variability
Authors: Alemu Elfalem Y. , Carl Joseph W. , Corrada Bravo Héctor , Hannenhalli Sridhar
Published: January 2014

The amount of tissue-specific expression variability (EV) across individuals is an essential characteristic of a gene and believed to have evolved, in part, under functional constraints. However, the determinants and functional implications of EV are only beginning to be investigated. Our analyses based on multiple expression profiles in 41 primary human tissues show that a gene’s EV is significantly correlated with a number of features pertaining to the genomic, epigenomic, regulatory, polymorphic, functional, structural and network characteristics of the gene. We found that (i) EV of a gene is encoded, in part, by its genomic context and is further influenced by the epigenome; (ii) strong promoters induce less variable expression; (iii) less variable gene loci evolve under purifying selection against copy number polymorphisms; (iv) genes that encode inherently disordered or highly interacting proteins exhibit lower variability; and (v) genes with less variable expression are enriched for house-keeping functions, while genes with highly variable expression tend to function in development and extra-cellular response and are associated with human diseases. Thus, our analysis reveals a number of potential mediators as well as functional and evolutionary correlates of EV, and provides new insights into the inherent variability in eukaryotic gene expression.
A tRNA splicing operon: Archease endows RtcB with dual GTP/ATP cofactor specificity and accelerates RNA ligation
Authors: Desai Kevin K. , Cheng Chin L. , Bingman Craig A. , Phillips George N. , Raines Ronald T.
Published: January 2014

Archease is a 16-kDa protein that is conserved in all three domains of life. In diverse bacteria and archaea, the genes encoding Archease and the tRNA ligase RtcB are localized into an operon. Here we provide a rationale for this operon organization by showing that Archease and RtcB from Pyrococcus horikoshii function in tandem, with Archease altering the catalytic properties of the RNA ligase. RtcB catalyzes the GTP and Mn(II)-dependent joining of either 2′,3′-cyclic phosphate or 3′-phosphate termini to 5′-hydroxyl termini. We find that catalytic concentrations of Archease are sufficient to activate RtcB, and that Archease accelerates both the RNA 3′-P guanylylation and ligation steps. In addition, we show that Archease can alter the NTP specificity of RtcB such that ATP, dGTP or ITP is used efficiently. Moreover, RtcB variants that have inactivating substitutions in the guanine-binding pocket can be rescued by the addition of Archease. We also present a 1.4 Å-resolution crystal structure of P. horikoshii Archease that reveals a metal-binding site consisting of conserved carboxylates located at the protein tip. Substitution of the Archease metal-binding residues drastically reduced Archease-dependent activation of RtcB. Thus, evolution has sought to co-express archease and rtcB by creating a tRNA splicing operon.
A novel role for the rat retrosplenial cortex in cognitive control
Authors: Nelson Andrew J.D. , Hindley Emma L. , Haddon Josephine E. , Vann Seralynne D. , Aggleton John P.
Published: January 2014

By virtue of its frontal and hippocampal connections, the retrosplenial cortex is uniquely placed to support cognition. Here, we tested whether the retrosplenial cortex is required for frontal tasks analogous to the Stroop Test, i.e., for the ability to select between conflicting responses and inhibit responding to task-irrelevant cues. Rats first acquired two instrumental conditional discriminations, one auditory and one visual, set in two distinct contexts. As a result, rats were rewarded for pressing either the right or left lever when a particular auditory or visual signal was present. In extinction, rats received compound stimuli that either comprised the auditory and visual elements that signaled the same lever response (congruent) or signaled different lever responses (incongruent) during training. On conflict (incongruent) trials, lever selection by sham-operated animals followed the stimulus element that had previously been trained in that same test context, whereas animals with retrosplenial cortex lesions failed to disambiguate the conflicting response cues. Subsequent experiments demonstrated that this abnormality on conflict trials was not due to a failure in distinguishing the contexts. Rather, these data reveal the selective involvement of the rat retrosplenial cortex in response conflict, and so extend the frontal system underlying cognitive control.
(S,Z)-3-Phenyl-2-[(1,1,1-trichloro-7-methoxy-2,7-dioxohept-3-en-4-yl)amino]propanoic acid monohydrate
Authors: Flores Alex Fabiani Claro , Vicenti Juliano Rosa de Menezes , Pizzuti Lucas , Campos Patrick Teixeira
Published: January 2014

In the title compound, C17H18Cl3NO5·H2O, intramolecular N—H...O and C—H...Cl hydrogen bonds formS(6) andS(5) ring motifs, respectively. The chiral organic molecule is connected to the solvent water molecule by a short O—H...O hydrogen bond. In the crystal, a weak C—H...Cl interaction connects the organic molecules along [100] while the water molecules act as bridges between the organic molecules in both the [100] and [010] directions, generating layers parallel to theabplane.
6,7-Dimethoxy-2,4-diphenylquinoline
Authors: Prabhuswamy M. , Madan Kumar S. , Swaroop T. R. , Rangappa K. S. , Lokanath N. K.
Published: January 2014

In the title structure of the title compound, C23H19NO2, two conformationally similar molecules (AandB) comprise the asymmetric unit. The dihedral angle between phenyl rings bridged by the quinoline moiety are 76.25 (8)° in moleculeAand 70.39 (9)° in moleculeB. In the crystal, the independent molecules are connected by C—H...O hydrogen bonds and the resulting dimeric aggregates are linked by π–π [inter-centroid distance = 3.7370 (8) Å] and C—H...π interactions, forming a three-dimensional architecture.
Tetrachloridodi-μ3-oxido-tetrakis(μ2-propan-2-olato-κ2O:O)ditin(II)ditin(IV)
Authors: Yarushnikov Oleg , Naumova Dina , Klishin Nikolai , Rusanov Eduard , Brusylovets Oleksii
Published: January 2014

The centrosymmetric tetranuclear title molecule, [Sn4(C3H7O)4Cl4O2], contains two types of Sn atoms, SnIIand SnIV. The SnIIatom has a trigonal–pyramidal coordination environment and is bonded to two O atoms from two isopropanolate groups and one μ3-oxide atom. The SnIVatom has an octahedral coordination environment, formed by two chloride atoms, two μ3-oxide atoms and two O atoms from isopropanolate groups.
(1-Methyl-1H-imidazole-κN3)(1-methyl-2-nitrosobenzene-κN)(5,10,15,20-tetraphenylporphyrinato-κ4N)iron(II) dichloromethane monosolvate
Authors: Abucayon Erwin G. , Awasabisah Dennis , Powell Douglas R. , Richter-Addo George B.
Published: January 2014

The solvated title compound, [Fe(C44H28N4)(C4H6N2)(C7H7NO)]·CH2Cl2, is a porphyrin complex containing an octahedrally coordinated FeIIatom with 1-methylimidazole [Fe—N = 2.0651 (17) Å] ando-nitrosotoluene ligands at the axial positions. Theo-nitrosotoluene ligand is N-bound to iron(II) [Fe—N = 1.8406 (18)Å and Fe—N—O = 122.54 (14)°]. The axial N—Fe—N linkage is almost linear, with a bond angle of 177.15 (7)°. One phenyl group of the porphyrin ligand is disordered over two orientations in a 0.710 (3):0.290 (3) ratio. The dichloromethane solvent molecule was severely disordered and its contribution to the scattering was removed with the SQUEEZE routine [van der Sluis & Spek (1990).Acta Cryst.A46, 194–201].
5-Imino-3,4-diphenyl-1H-pyrrol-2-one
Authors: Bulatov Evgeny , Chulkova Tatiana , Haukka Matti
Published: January 2014

The title compound, C16H12N2O, exists in the crystalline state as the 5-imino-3,4-diphenyl-1H-pyrrol-2-one tautomer. The dihedral angles between the pyrrole and phenyl rings are 35.3 (2) and 55.3 (2)°. In the crystal, inversion dimers linked by pairs of N—H...N hydrogen bonds generate a graph-set motif ofR22(8)viaN—H...N hydrogen bonds.
Diffraction stress analysis of highly planar-faulted, macroscopically elastically anisotropic thin films and application to tensilely loaded nanocrystalline Ni and Ni(W)
Authors: Kurz Silke Julia Birgit , Welzel Udo , Bischoff Ewald , Mittemeijer Eric Jan
Published: January 2014

The presence of planar faults complicates the diffraction stress analysis enormously owing to fault-induced displacement, broadening and asymmetry of the Bragg reflections. A dedicated stress-analysis method has been developed for highly planar-faulted, fibre-textured thin films of cubic crystal symmetry, using only specific reflections for diffraction stress analysis. The effect of unjustified use of other reflections has been demonstrated in the course of application of the method to Ni and Ni(W) thin films exhibiting excessive faulting and subjected to (1) a planar, rotationally symmetric stress state and (2) a planar biaxial stress state. In case 1 the crystallite-group method has been used, whereas in case 2 the stress-analysis method based on X-ray stress factors had to be applied. The successful separation of stress- and fault-induced reflection displacements has enabled the investigation of the mechanical behaviour of Ni and Ni(W) thin films byin situstress measurements during tensile loading, thereby exposing pronounced stiffness and increased strength by alloying with W.
Effect of cationic order–disorder on the transport properties of LaBaCo2O6–δand La0.5Ba0.5CoO3–δperovskites
Authors: Garcés Diana , Setevich Cristian F. , Caneiro Alberto , Cuello Gabriel Julio , Mogni Liliana
Published: January 2014

A-site cationic ordered LaBaCo2O6−δand disordered La0.5Ba0.5CoO3−δperovskite phases were obtained by solid state reaction. Their structural properties were studied at room temperature and 673 K, by combining powder diffraction techniques, X-ray diffraction and neutron powder diffraction with an independent determination of the oxygen content of the samples by thermogravimetry. La0.5Ba0.5CoO3−δexhibits cubic symmetry with cations randomly distributed, whereas LaBaCo2O6−δshows tetragonal symmetry with the La3+and Ba2+ions distributed in alternating layers. The diffraction data were analyzed using the Rietveld method and different structural and microstructural models. Bond valence and Fourier methods were used to determine bond distances and neutron/electron density maps. LaBaCo2O6−δexhibits a higher concentration of oxygen vacancies than La0.5Ba0.5CoO3−δ, because the O atom is weakly bonded to the LaO layers. The anisotropic atomic displacement and the neutron density distribution suggest a two-dimensional O-migration path for LaBaCo2O6−δand a three-dimensional path for La0.5Ba0.5CoO3−δ.The mechanism of electrical conductivity isviaelectron holes with high mobilities (μLa0.5Ba0.5CoO3−δ= 2.49 cm2 V−1 s−1and μLaBaCo2O6−δ= 1.48 cm2 V−1 s−1at room temperature) and low activation energy (EaLaBaCo2O6−δ = 0.019 eV andEaLa0.5Ba0.5CoO3−δ= 0.030 eV). It has also been found that the higher electronic and ionic conductivities in La0.5Ba0.5CoO3−δcompared to those in LaBaCo2O6−δare due to the higher dimensionality of transport and to greater overlapping between the Co 3dand O 2porbitals.
Structural analysis of calcium reactive hydride composite for solid state hydrogen storage
Authors: Karimi Fahim , Pranzas P. Klaus , Hoell Armin , Vainio Ulla , Welter Edmund , Raghuwanshi Vikram S. , Pistidda Claudio , Dornheim Martin , Klassen Thomas , Schreyer Andreas
Published: January 2014

Owing to a theoretical hydrogen storage capacity of 10.5 wt% H2, Ca(BH4)2+MgH2, the so-called calcium reactive hydride composite (Ca-RHC), has a great potential as a hydrogen storage material. However, its dehydrogenation temperature (∼623 K) is too high for any mobile applications. By addition of 10 mol% of NbF5into Ca(BH4)2+MgH2, a decrease of the dehydrogenation onset temperature by ∼120 K is observed. In order to understand the reasons behind this desorption temperature decrement two sets of samples [Ca(BH4)2+MgH2and Ca(BH4)2+MgH2+0.1NbF5] in different hydrogenation states, were prepared. The structural investigation of the above mentioned sets of samples by means of volumetric measurements, anomalous small-angle X-ray scattering (ASAXS) and X-ray absorption spectroscopy (XAS) is reported here. The XAS results show that after the milling procedure NbB2is formed and remains stable upon further de/rehydrogenation cycling. The results of Nb ASAXS point to nanometric spherical NbB2particles distributed in the hydride matrix, with a mean diameter of ∼10 nm. Results from Ca ASAXS indicate Ca-containing nanostructures in the Ca-RHC+0.1NbF5samples to be ∼50% finer compared to those without additive. Thus, a higher reaction surface area and shorter diffusion paths for the constituents are concluded to be important contributions to the catalytic effect of an NbF5additive on the hydrogen sorption kinetics of the Ca(BH4)2+MgH2composite system.
Microstructure and texture analysis of δ-hydride precipitation in Zircaloy-4 materials by electron microscopy and neutron diffraction
Authors: Wang Zhiyang , Garbe Ulf , Li Huijun , Wang Yanbo , Studer Andrew J. , Sun Guangai , Harrison Robert P. , Liao Xiaozhou , Vicente Alvarez M. A. , Santisteban J. R. , Kong Charlie
Published: January 2014

This work presents a detailed microstructure and texture study of various hydrided Zircaloy-4 materials by neutron diffraction and microscopy. The results show that the precipitated δ-ZrH1.66generally follows the δ(111)//α(0001) and δ[1{\overline 1}0]//α[11{\overline 2}0] orientation relationship with the α-Zr matrix. The δ-hydride displays a weak texture that is determined by the texture of the α-Zr matrix, and this dependence essentially originates from the observed orientation correlation between α-Zr and δ-hydride. Neutron diffraction line profile analysis and high-resolution transmission electron microscopy observations reveal a significant number of dislocations present in the δ-hydride, with an estimated average density one order of magnitude higher than that in the α-Zr matrix, which contributes to the accommodation of the substantial misfit strains associated with hydride precipitation in the α-Zr matrix. The present observations provide an insight into the behaviour of δ-hydride precipitation in zirconium alloys and may help with understanding the induced embrittling effect of hydrides.
Effect of aging and alkali activator on the porous structure of a geopolymer
Authors: Steins Prune , Poulesquen Arnaud , Frizon Fabien , Diat Olivier , Jestin Jacques , Causse Jérémy , Lambertin David , Rossignol Sylvie
Published: January 2014

Nitrogen sorption and small- and wide-angle X-ray and neutron scattering techniques were used to study the porous structure of geopolymers, inorganic polymers synthesized by reaction of a strongly alkaline solution and an aluminosilicate source (metakaolin). The effects of aging and the use of alkali activators (Na+, K+) of different sizes were investigated at room temperature. The influence of aging time on the microstructure of both geopolymer matrixes was verified in terms of pore volume and specific surface area. The results suggested a refinement of the porosity and therefore a reduction in the pore volume over time. Regardless of the age considered, some characteristics of the porous network such as pore size, shape and distribution depend on the alkali activator used. Whatever the technique considered, the potassium geopolymer has a greater specific surface area than the sodium geopolymer. According to the scattering results, the refinement of the porosity can be associated with, first, a densification of the solid network and, secondly, a partial closure of the porosity at the nanometre scale. The kinetics are much slower for the sodium geopolymer than for the potassium geopolymer in the six months of observation.