bluuebunny/crossref_metadata_2025 huggingface dataset:
Roles of glutamine in neurotransmission
Authors: Albrecht Jan , Sidoryk-Węgrzynowicz Marta , Zielińska Magdalena , Aschner Michael
Published: October 2011

Glutamine (Gln) is found abundantly in the central nervous system (CNS) where it participates in a variety of metabolic pathways. Its major role in the brain is that of a precursor of the neurotransmitter amino acids: the excitatory amino acids, glutamate (Glu) and aspartate (Asp), and the inhibitory amino acid, γ-amino butyric acid (GABA). The precursor–product relationship between Gln and Glu/GABA in the brain relates to the intercellular compartmentalization of the Gln/Glu(GABA) cycle (GGC). Gln is synthesized from Glu and ammonia in astrocytes, in a reaction catalyzed by Gln synthetase (GS), which, in the CNS, is almost exclusively located in astrocytes (Martinez-Hernandez et al., 1977). Newly synthesized Gln is transferred to neurons and hydrolyzed by phosphate-activated glutaminase (PAG) to give rise to Glu, a portion of which may be decarboxylated to GABA or transaminated to Asp. There is a rich body of evidence which indicates that a significant proportion of the Glu, Asp and GABA derived from Gln feed the synaptic, neurotransmitter pools of the amino acids. Depolarization-induced-, calcium- and PAG activity-dependent releases of Gln-derived Glu, GABA and Asp have been observed in CNS preparations in vitro and in the brain in situ. Immunocytochemical studies in brain slices have documented Gln transfer from astrocytes to neurons as well as the location of Gln-derived Glu, GABA and Asp in the synaptic terminals. Patch-clamp studies in brain slices and astrocyte/neuron co-cultures have provided functional evidence that uninterrupted Gln synthesis in astrocytes and its transport to neurons, as mediated by specific carriers, promotes glutamatergic and GABA-ergic transmission. Gln entry into the neuronal compartment is facilitated by its abundance in the extracellular spaces relative to other amino acids. Gln also appears to affect neurotransmission directly by interacting with the NMDA class of Glu receptors. Transmission may also be modulated by alterations in cell membrane polarity related to the electrogenic nature of Gln transport or to uncoupled ion conductances in the neuronal or glial cell membranes elicited by Gln transporters. In addition, Gln appears to modulate the synthesis of the gaseous messenger, nitric oxide (NO), by controlling the supply to the cells of its precursor, arginine. Disturbances of Gln metabolism and/or transport contribute to changes in Glu-ergic or GABA-ergic transmission associated with different pathological conditions of the brain, which are best recognized in epilepsy, hepatic encephalopathy and manganese encephalopathy.
Measuring urban rainfall using microwave links from commercial cellular communication networks
Authors: Overeem A. , Leijnse H. , Uijlenhoet R.
Published: October 2011

The estimation of rainfall using commercial microwave links is a new and promising measurement technique. Commercial link networks cover large parts of the land surface of the earth and have a high density, particularly in urban areas. Rainfall attenuates the electromagnetic signals transmitted between antennas within this network. This attenuation can be calculated from the difference between the received powers with and without rain and is a measure of the path‐averaged rainfall intensity. This study uses a 17‐day data set of, on average, 57 single‐frequency links from 2009 to estimate rainfall in the Rotterdam region, a densely populated delta city in Netherlands (≈1250 km2, >1 million inhabitants). A methodology is proposed where nearby links are used to remove signal fluctuations that are not related to rainfall in order to be able to reliably identify wet and dry weather spells. Subsequently, received signal powers are converted to path‐averaged rainfall intensities, taking into account the temporal sampling protocol and attenuation due to wet antennas. Link‐based rainfall depths are compared with those based on gauge‐adjusted radar data. In addition, the rainfall retrieval algorithm is applied to an independent data set of 21 rainy days in 2010 with on average 16 single‐frequency links in the same region. Rainfall retrievals are compared against gauge‐adjusted radar rainfall estimates over the link path. Moreover, the retrieval algorithm is also tested using high‐resolution research link data to investigate the algorithm's sensitivity to temporal rainfall variations. All presented comparisons confirm the quality of commercial microwave link data for quantitative precipitation estimation over urban areas.
Geomorphic and structural variations along the Doruneh Fault System (central Iran)
Authors: Farbod Yassaman , Bellier Olivier , Shabanian Esmaeil , Abbassi Mohammad Reza
Published: October 2011

This paper focuses on the analysis of geomorphic, structural, and behavioral characteristics along the Doruneh Fault System (DFS), east of longitude 56°45′E. Detailed geomorphic and structural analyses of different scale satellite images and digital topographic data, accompanied with field surveys allowed us to establish a fault segmentation model in which three discrete fault zones have been recognized: (1) the western fault zone (WFZ) characterized by reverse left‐lateral mechanism with left‐handed step‐over geometry, (2) the central fault zone (CFZ) which is pure left‐lateral strike‐slip and comprises nearly parallel faults, and (3) the eastern fault zone (EFZ) that is a trailing imbricate fan fault‐termination characterized by reverse faulting and fault‐related folding. Each fault zone shows discrete geometry and kinematics implying that deformation is not uniformly accommodated along the DFS. We propose a new kinematic model to explain how the DFS accommodate the Arabia‐Eurasia convergence normal to the overall fault orientation. According to this model, the DFS takes up the northward motion between central Iran–Lut block relative to Eurasia by a complex kinematics varying from pure reverse to pure left‐lateral strike‐slip faulting. The kinematics of the WFZ and EFZ corresponds to the direction of the NE‐trending regional compression. While, the partitioning of slip into strike‐slip and reverse component of faulting on parallel faults (strain partitioning) allows the CFZ to remain pure left‐lateral strike‐slip. Such a model propose a way to explain how large strike‐slip faults such as the DFS accommodate tectonic block motions perpendicular to strike of the faults.
Growth and fragmentation of the Andean foreland basin during eastward advance of fold‐thrust deformation, Puna plateau and Eastern Cordillera, northern Argentina
Authors: Siks Benjamin C. , Horton Brian K.
Published: October 2011

The fault‐bounded Cianzo basin represents a Cenozoic depocenter between the Puna plateau and Eastern Cordillera of northern Argentina. Analysis of fold‐thrust relationships, nonmarine sedimentation, and detrital provenance at 23–24°S helps constrain the origin, interconnectedness, and subsequent uplift and exhumation of the Cianzo basin, a potential analog for intermontane hinterland basins in the Andes. Structural mapping reveals a plunging syncline within the >6000‐m‐thick, upward coarsening Cenozoic clastic succession in the shared footwall of the N‐striking, E‐directed Cianzo thrust fault and transverse, NE‐striking Hornocal fault. Growth strata within upper Miocene levels indicate syncontractional accumulation adjacent to the Hornocal fault. Measured stratigraphic sections show upsection changes from (1) paleosol‐rich, distal‐fluvial sandstones (∼400 m Paleocene‐Eocene Santa Bárbara Subgroup) to (2) braided fluvial sandstones and mudstones (∼1400 m upper Eocene‐Oligocene Casa Grande Formation) to (3) distributary fluvial megafan sandstones and conglomerates (∼3300 m upper Oligocene‐Miocene Río Grande Formation) to (4) alluvial fan conglomerates (∼1600 m upper Miocene Pisungo Formation). The 40Ar/39Ar geochronological results for interbedded tuffs indicate continuous Río Grande deposition from at least 16.34 ± 0.71 to 9.69 ± 0.05 Ma. Sandstone petrographic results define distinct upsection trends in lithic and feldspar content, potentially distinguishing the Western Cordillera magmatic arc from Puna‐Eastern Cordillera thrust‐belt sources. In addition to growth stratal relationships and 40Ar/39Ar ages, conglomerate clast compositions reflect distinct lithologic differences, constraining activation of the Cianzo thrust and coeval reverse slip on the reactivated (inverted) Hornocal fault. Finally, detrital zircon U‐Pb ages, paleocurrents, and facies patterns distinguish local from distal sources, revealing a systematic forelandward (eastward) advance of Eocene through upper Miocene fold‐thrust deformation.
Tectonic history of the Kyrgyz South Tien Shan (Atbashi‐Inylchek) suture zone: The role of inherited structures during deformation‐propagation
Authors: Glorie S. , De Grave J. , Buslov M. M. , Zhimulev F. I. , Stockli D. F. , Batalev V. Y. , Izmer A. , Van den haute P. , Vanhaecke F. , Elburg M. A.
Published: October 2011

Multimethod chronology was applied on intrusives bordering the Kyrgyz South Tien Shan suture (STSs) to decipher the timing of (1) formation and amalgamation of the suturing units and (2) intracontinental deformation that built the bordering mountain ranges. Zircon U/Pb data indicate similarities between the Tien Shan and Tarim Precambrian crust. Caledonian (∼440–410 Ma) and Hercynian (∼310–280 Ma) zircon U/Pb ages were found at the edge of the STSs, related to subduction and closure of the Turkestan Ocean and the formation of the suture itself. Permian‐Triassic (∼280–210 Ma) titanite fission track and zircon (U‐Th)/He data record the first signs of exhumation when the STSs evolved into a shear zone and the adjacent Tarim basin started to subside. Low‐temperature thermochronological (apatite fission track, zircon and apatite (U‐Th)/He) analyses reveal three distinct cooling phases, becoming younger toward the STSs center: (1) Jurassic‐Cretaceous cooling ages provide evidence that a Mesozoic South Tien Shan orogen formed as a response to the Cimmerian orogeny; (2) Early Paleogene (∼60–45 Ma) data indicate a renewed pulse of STSs reactivation during the Early Cenozoic; (3) Neogene ages constrain the onset of the modern Tien Shan mountain building to the Late Oligocene (∼30–25 Ma), which intensified during the Miocene (∼10–8 Ma) and Pliocene (∼3–2 Ma). The Cenozoic signals may reflect renewed responses to collisions at the southern Eurasian border (i.e., the Kohistan‐Dras and India‐Eurasia collisions). This progressive rejuvenation of the STSs demonstrates that deformation has not migrated steadily into the forelands, but was focused on pre‐existing basement structures.
Gravity Recovery and Climate Experiment (GRACE) detection of water storage changes in the Three Gorges Reservoir of China and comparison with in situ measurements
Authors: Wang Xianwei , de Linage Caroline , Famiglietti James , Zender Charles S.
Published: October 2011

Water impoundment in the Three Gorges Reservoir (TGR) of China caused a large mass redistribution from the oceans to a concentrated land area in a short time period. We show that this mass shift is captured by the Gravity Recovery and Climate Experiment (GRACE) unconstrained global solutions at a 400 km spatial resolution after removing correlated errors. The WaterGAP Global Hydrology Model (WGHM) is selected to isolate the TGR contribution from regional water storage changes. For the first time, this study compares the GRACE (minus WGHM) estimated TGR volume changes with in situ measurements from April 2002 to May 2010 at a monthly time scale. During the 8 year study period, GRACE‐WGHM estimated TGR volume changes show an increasing trend consistent with the TGR in situ measurements and lead to similar estimates of impounded water volume. GRACE‐WGHM estimated total volume increase agrees to within 14% (3.2 km3) of the in situ measurements. This indicates that GRACE can retrieve the true amplitudes of large surface water storage changes in a concentrated area that is much smaller than the spatial resolution of its global harmonic solutions. The GRACE‐WGHM estimated TGR monthly volume changes explain 76% (r2 = 0.76) of in situ measurement monthly variability and have an uncertainty of 4.62 km3. Our results also indicate reservoir leakage and groundwater recharge due to TGR filling and contamination from neighboring lakes are nonnegligible in the GRACE total water storage changes. Moreover, GRACE observations could provide a relatively accurate estimate of global water volume withheld by newly constructed large reservoirs and their impacts on global sea level rise since 2002.
Thrombin-induced shedding of tumour endothelial marker 5 and exposure of its RGD motif are regulated by cell-surface protein disulfide-isomerase
Authors: Vallon Mario , Aubele Philipp , Janssen Klaus-Peter , Essler Markus
Published: October 2011

TEM5 (tumour endothelial marker 5; also known as GPR124) is an adhesion G-protein-coupled receptor containing a cryptic RGD motif in its extracellular domain. TEM5 is expressed in endothelial cells and pericytes during angiogenesis. In the present paper, we report that thrombin mediates shedding of an N-terminal TEM5 fragment of 60 kDa (termed N60) containing the RGD motif in an open conformation. Thrombin directly cleaved rsTEM5 (recombinant soluble TEM5) 5 and 34 residues downstream of the RGD motif, resulting in formation of N60 and its C-terminal counterpart (termed C50). Interestingly, N60 derived from thrombin cleavage of rsTEM5 was covalently linked to C50 by disulfide bonds, whereas N60 shed from thrombin-treated cells was not associated with its membrane-bound C-terminal counterpart. Inhibition of the reducing function of cell-surface PDI (protein disulfide-isomerase) abrogated thrombin-induced N60 shedding. Conversely, addition of reduced PDI enhanced N60 shedding. Furthermore, thrombin cleavage of rsTEM5 was increased by reduced PDI and resulted in dissociation of the N60–C50 heterodimer. We conclude that PDI regulates thrombin-induced shedding of N60 and exposure of the TEM5 RGD motif by catalysing the reduction of crucial disulfide bonds of TEM5 on the cell surface. Binding of N60 to RGD-dependent integrins may modulate cellular functions such as adhesion and migration during angiogenesis.
The effect of air leakage and heat exchange on the decay of entrapped air pocket slamming oscillations
Authors: Abrahamsen Bjørn C. , Faltinsen Odd M.
Published: October 2011

The phenomenon studied in this work is that of an air pocket entrapped by a free surface water wave inside a rectangular tank at a high filling level. The wave, which is a gravity wave, is caused by forced horizontal motion which is constructed in a particular way, in order to entrap an air pocket as it approaches the upper left corner of the tank. As the wave touches the roof, the air is compressed and starts to oscillate. The oscillations resemble, to some extent, the free oscillations of an underdamped mass-spring system, where the mass is related to the generalized added mass effect of the water pressure associated with the air pocket oscillations. The stiffness is due to the compressibility of the air. The reason for the damping or, more generally, the decay of the air pocket oscillations is less understood. Air leakage has been proposed as one possible reason for this decay. In this work, the role of air leakage is found not to be the reason for the decay of the air pocket oscillations, because it is not present during major parts of the impact. However, by drilling holes in the roof of the tank, the effect of leakage during the oscillations is proven to cause decay. To explain the physical source of the decay of the oscillations, damping due to heat transfer to and from the air pocket is investigated through an analytical one-dimensional steady-state model. The damping due to heat transfer is observed to play an important role. The obtained understanding of the mechanisms causing the decay of the air-pocket impact at the upper corner is believed to be relevant to other types of impacts, particularly the entrapment of air pockets on walls by breaking waves.
Plasma dynamics in laboratory-produced current sheets
Authors: Frank Anna G. , Kyrie Natalya P. , Satunin Sergey N.
Published: October 2011

Evolution of currents and Ampere forces in current sheets are analyzed on the basis of magnetic measurements. Two new effects are observed in the current distributions at the later stage of the sheet evolution: first, a broadening of the current area at the side edges of the current sheet; second, a generation of reverse currents followed by their propagation from the edges to the center of the sheet. Super-thermal plasma flows moving across the width of the current sheet are observed by spectroscopic methods. The energies of plasma jets are consistent with the spatial structure and time dependences of the Ampere forces in the current sheets. The assumption is advanced that plasma acceleration may be more effective at the regions with lower plasma density, which are located at some distances from the sheet mid-plane. Generation of reverse currents provides an additional confirmation of transfer of energetic plasma jets toward the sheet edges.
Impurity-free seeded crystallization of amorphous silicon by nanoindentation
Authors: Ruffell S. , Knights A. P. , Bradby J. E. , Williams J. S.
Published: October 2011

We demonstrate that nanoindents formed in amorphous Si films, with dimensions as small as ∼20 nm, provide a means to seed solid phase crystallization. During post-indentation annealing at ∼600 °C, solid phase crystallization initiates from the indented sites, effectively removing the incubation time for random nucleation in the absence of seeds. The seeded crystallization is studied by optical microscopy, cross-sectional transmission electron microscopy, and electrical characterization via Hall measurements. Full crystallization can be achieved, with improved electrical characteristics attributed to the improved microstructure, using a lower thermal budget. The process is metal contaminant free and allows for selective area crystallization.
Magnetic properties of sputtered Permalloy/molybdenum multilayers
Authors: Romera M. , Ranchal R. , Ciudad D. , Maicas M. , Aroca C.
Published: October 2011

In this work, we report the magnetic properties of sputtered Permalloy (Py: Ni80Fe20)/molybdenum (Mo) multilayer thin films. We show that it is possible to maintain a low coercivity and a high permeability in thick sputtered Py films when reducing the out-of-plane component of the anisotropy by inserting thin film spacers of a non-magnetic material like Mo. For these kind of multilayers, we have found coercivities which are close to those for single layer films with no out-of-plane anisotropy. The coercivity is also dependent on the number of layers exhibiting a minimum value when each single Py layer has a thickness close to the transition thickness between Neel and Bloch domain walls.
Quantitative calibration of radiofrequency NMR Stark effects
Authors: Tarasek Matthew R. , Kempf James G.
Published: October 2011

Nuclear magnetic resonance (NMR) Stark responses can occur in quadrupolar nuclei for an electric field oscillating at twice the usual NMR frequency (2ω0). Calibration of responses to an applied E field is needed to establish nuclear spins as probes of native E fields within material and molecular systems. We present an improved approach and apparatus for accurate measurement of quadrupolar Stark effects. Updated values of C14 (the response parameter in cubic crystals) were obtained for both 69Ga and 75As in GaAs. Keys to improvement include a modified implementation of voltage dividers to assess the 2ω0 amplitude, |E|, and the stabilization of divider response by reduction of stray couplings in 2ω0 circuitry. Finally, accuracy was enhanced by filtering sets of |E| through a linear response function that we established for the radiofrequency amplifier. Our approach is verified by two types of spectral results. Steady-state 2ω0 excitation to presaturate NMR spectra yielded C14 = (2.59 ± 0.06) × 1012 m−1 for 69Ga at room-temperature and 14.1 T. For 75As, we obtained (3.1 ± 0.1) × 1012 m−1. Both values reconcile with earlier results from 77 K and below 1 T, whereas current experiments are at room temperature and 14.1 T. Finally, we present results where few-microsecond pulses of the 2ω0 field induced small (tens of Hz) changes in high-resolution NMR line shapes. There too, spectra collected vs |E| agree with the model for response, further establishing the validity of our protocols to specify |E|.
Rapid, accurate calculation of the s-wave scattering length
Authors: Meshkov Vladimir V. , Stolyarov Andrey V. , Le Roy Robert J.
Published: October 2011

Transformation of the conventional radial Schrödinger equation defined on the interval  r ∈ [0, ∞) into an equivalent form defined on the finite domain  y(r) ∈ [a, b]  allows the s-wave scattering length as to be exactly expressed in terms of a logarithmic derivative of the transformed wave function ϕ(y) at the outer boundary point y = b, which corresponds to r = ∞. In particular, for an arbitrary interaction potential that dies off as fast as 1/rn for n ⩾ 4, the modified wave function ϕ(y) obtained by using the two-parameter mapping function $r(y;\bar{r},\beta ) = \bar{r}[1+\frac{1}{\beta }\tan (\pi y/2)]$r(y;r¯,β)=r¯[1+1βtan(πy/2)] has no singularities, and $a_s=\bar{r}[1+\frac{2}{\pi \beta }\frac{1}{\phi (1)}\frac{d\phi (1)}{dy}] .$as=r¯[1+2πβ1φ(1)dφ(1)dy]. For a well bound potential with equilibrium distance re, the optimal mapping parameters are $\,\bar{r}\approx r_e\,$r¯≈re and $\,\beta \approx \frac{n}{2}-1$β≈n2−1. An outward integration procedure based on Johnson's log-derivative algorithm [J. Comp. Phys. 13, 445 (1973)] combined with a Richardson extrapolation procedure is shown to readily yield high precision as-values both for model Lennard-Jones (2n, n) potentials and for realistic published potentials for the Xe–e−, ${\rm Cs}_2(a\sideset{^3}{_u^+}{\Sigma}$ Cs 2(aΣu+3), and 3, 4${\rm He}_2(X\sideset{^1}{_g^+}{\Sigma})$ He 2(XΣg+1) systems. Use of this same transformed Schrödinger equation was previously shown [V. V. Meshkov et al., Phys. Rev. A 78, 052510 (2008)] to ensure the efficient calculation of all bound levels supported by a potential, including those lying extremely close to dissociation.
Numerical modeling of quasitransient backward Raman amplification of laser pulses in moderately undercritical plasmas with multicharged ions
Authors: Balakin A. A. , Fisch N. J. , Fraiman G. M. , Malkin V. M. , Toroker Z.
Published: October 2011

It was proposed recently that powerful optical laser pulses could be efficiently compressed through backward Raman amplification in ionized low density solids, in spite of strong damping of the resonant Langmuir wave. It was argued that, even for nonsaturated Landau damping of the Langmuir wave, the energy transfer from the pump laser pulse to the amplified seed laser pulse can nevertheless be highly efficient. This work numerically examines such regimes of strong damping, called quasitransient regimes, within the simplest model that takes into account the major effects. The simulations indicate that compression of powerful optical laser pulses in ionized low density solids indeed can be highly efficient.
Index of refraction of shock-released materials
Authors: Fratanduono D. E. , Eggert J. H. , Boehly T. R. , Barrios M. A. , Meyerhofer D. D. , Jensen B. J. , Collins G. W.
Published: October 2011

A new technique to measure the refractive index of shocked materials is reported. The arrival of a transparent shock at the free surface of an optical window generates a discontinuity in the observed interferometry record. In this work, we show that the magnitude of that discontinuity is simply defined by the shock velocity, the shocked refractive, and the free-surface velocity. This new technique, to measure the high-pressure refractive index of a transparent material, is demonstrated.
A 4D wave packet study of the CH3I photodissociation in the A-band. Comparison with femtosecond velocity map imaging experiments
Authors: García-Vela A. , de Nalda R. , Durá J. , González-Vázquez J. , Bañares L.
Published: October 2011

The time-resolved photodissociation dynamics of CH3I in the A-band has been studied theoretically using a wave packet model including four degrees of freedom, namely the C–I dissociation coordinate, the I–CH3 bending mode, the CH3 umbrella mode, and the C−H symmetric stretch mode. Clocking times and final product state distributions of the different dissociation (nonadiabatic) channels yielding spin-orbit ground and excited states of the I fragment and vibrationless and vibrationally excited (symmetric stretch ν1 and umbrella ν2 modes) CH3 fragments have been obtained and compared with the results of femtosecond velocity map imaging experiments. The wave packet calculations are able to reproduce with very good agreement the experimental reaction times for the CH3(ν1, ν2)+I*(2P1/2) dissociation channels with ν1 = 0 and ν2 = 0,1,2, and also for the channel CH3(ν1 = 0, ν2 = 0)+I(2P3/2). However, the model fails to predict the experimental clocking times for the CH3(ν1, ν2)+I(2P3/2) channels with (ν1, ν2) = (0, 1), (0, 2), and (1, 0), that is, when the CH3 fragment produced along with spin-orbit ground state I atoms is vibrationally excited. These results are similar to those previously obtained with a three-dimensional wave packet model, whose validity is discussed in the light of the results of the four-dimensional treatment. Possible explanations for the disagreements found between theory and experiment are also discussed.
Correlated motion dynamics of electron channels and domain walls in a ferroelectric-gate thin-film transistor consisting of a ZnO/Pb(Zr,Ti)O3 stacked structure
Authors: Kaneko Yukihiro , Nishitani Yu , Tanaka Hiroyuki , Ueda Michihito , Kato Yoshihisa , Tokumitsu Eisuke , Fujii Eiji
Published: October 2011

We studied the switching dynamics of a ferroelectric-gate thin-film transistor (FeTFT) consisting entirely of oxide-based thin films: SrRuO3 (SRO: bottom-gate electrode), Pb(Zr,Ti)O3 (PZT: ferroelectric), and ZnO (semiconductor). We switched the FeTFT channel conductance by applying short pulses to the gate electrode. We found that the switching of a FeTFT was caused by the domain wall motion in a ferroelectric film. The polarization reversal starts from the region located under the source and drain electrodes and travels along the channel length direction. In addition, the domain wall velocity increases as the domain wall gets closer to the source and drain electrodes in a ferroelectric film. Therefore, a FeTFT has the scaling merit of fast operation speed.
Second-order dipolar order in magic-angle spinning nuclear magnetic resonance
Authors: van Beek Jacco D. , Hemmi Adrian , Ernst Matthias , Meier Beat H.
Published: October 2011

Generating dipolar order under magic-angle spinning (MAS) conditions is explored for different pulse sequences and dipolar-coupling networks. It is shown that under MAS second-order dipolar order can be generated reliably with 10% to 30% efficiency using the Jeener-Broekaert sequence in systems where the second-order average Hamiltonian is a (near) constant of the motion. When using adiabatic demagnetization and remagnetization, second-order dipolar order can be generated and reverted back to Zeeman order with up to 60% efficiency. This requires a maximum field strength with a nutation frequency that is less than one-quarter of the rotor frequency, and that the spin system can be properly spinlocked under such conditions. A simple coherent description accounts for the principal features of the spin dynamics, even using the smallest possible system of three coupled spins. For the systems investigated, the lifetime of second-order dipolar order under MAS was found to be on the order of T1.
Nonlinear waves and coherent structures in the quantum single-wave model
Authors: Tzenov Stephan I. , Marinov Kiril B.
Published: October 2011

Starting from the von Neumann-Maxwell equations for the Wigner quasi-probability distribution and for the self-consistent electric field, the quantum analog of the classical single-wave model has been derived. The linear stability of the quantum single-wave model has been studied, and periodic in time patterns have been found both analytically and numerically. In addition, some features of quantum chaos have been detected in the unstable region in parameter space. Further, a class of standing-wave solutions of the quantum single-wave model has also been found, which have been observed to behave as stable solitary-wave structures. The analytical results have been finally compared to the exact system dynamics obtained by solving the corresponding equations in Schrodinger representation numerically.
Reaction coordinates for the crystal nucleation of colloidal suspensions extracted from the reweighted path ensemble
Authors: Lechner Wolfgang , Dellago Christoph , Bolhuis Peter G.
Published: October 2011

We study the mechanisms of the homogeneous crystal nucleation from the supercooled liquid to the crystal phase in the Gaussian core model for colloidal suspensions with the aim to find optimal reaction coordinates. We introduce a set of novel collective variables based on the local structure of particles. By applying likelihood maximization of the committor function for the reweighted path ensemble constructed by replica exchange transition interface sampling, we select the optimal reaction coordinates from the set of collective variables. We find that the size of the cloud of prestructured particles surrounding the crystalline nucleus enhances the description of the transition. Further, we show that the rearrangement of the inner core of the nucleus according to Ostwald's step rule is a separate process, independent of the growth of the nucleus.
Ab initioquantum dynamical study of the multi-state nonadiabatic photodissociation of pyrrole
Authors: Faraji S. , Vazdar M. , Reddy V. Sivaranjana , Eckert-Maksic M. , Lischka H. , Köppel H.
Published: October 2011

There has been a substantial amount of theoretical investigations on the photodynamics of pyrrole, often relying on surface hopping techniques or, if fully quantal, confining the study to the lowest two or three singlet states. In this study we extend ab initio based quantum dynamical investigations to cover simultaneously the lowest five singlet states, two π − σ* and two π − π* excited states. The underlying potential energy surfaces are obtained from large-scale MRCI ab initio computations. These are used to extract linear and quadratic vibronic coupling constants employing the corresponding coupling models. For the \documentclass[12pt]{minimal}\begin{document}$\text{N-H}$\end{document}N-H stretching mode Q24 an anharmonic treatment is necessary and also adopted. The results reveal a sub-picosecond internal conversion from the S4 (π − π*) state, corresponding to the strongly dipole-allowed transition, to the S1 and S2 (π − σ*) states and, hence, to the ground state of pyrrole. The significance of the various vibrational modes and coupling terms is assessed. Results are also presented for the dissociation probabilities on the three lowest electronic states.
Electronic excitation dynamics in multichromophoric systems described via a polaron-representation master equation
Authors: Kolli Avinash , Nazir Ahsan , Olaya-Castro Alexandra
Published: October 2011

We derive a many-site version of the non-Markovian time-convolutionless polaron master equation [Jang et al., J. Chem Phys. 129, 101104 (2008)]10.1063/1.2977974 to describe electronic excitation dynamics in multichromophoric systems. By treating electronic and vibrational degrees of freedom in a combined frame (polaron frame), this theory is capable of interpolating between weak and strong exciton-phonon coupling and is able to account for initial non-equilibrium bath states and spatially correlated environments. Besides outlining a general expression for the expected value of any electronic system observable in the original frame, we also discuss implications of the Markovian and Secular approximations highlighting that they need not hold in the untransformed frame despite being strictly satisfied in the polaron frame. The key features of the theory are illustrated using as an example a four-site subsystem of the Fenna-Mathews-Olson light-harvesting complex. For a spectral density including a localised mode, we show that oscillations of site populations may only be observed when non-equilibrium bath effects are taken into account. Furthermore, we illustrate how this formalism allows us to identify the electronic and vibrational components of the oscillatory dynamics.
The size of RNA as an ideal branched polymer
Authors: Fang Li Tai , Gelbart William M. , Ben-Shaul Avinoam
Published: October 2011

Because of the branching arising from partial self-complementarity, long single-stranded (ss) RNA molecules are significantly more compact than linear arrangements (e.g., denatured states) of the same sequence of monomers. To elucidate the dependence of compactness on the nature and extent of branching, we represent ssRNA secondary structures as tree graphs which we treat as ideal branched polymers, and use a theorem of Kramers for evaluating their root-mean-square radius of gyration, $\hat R_g = \sqrt {\langle {R_g^2 } \rangle } $R̂g=⟨Rg2⟩. We consider two sets of sequences—random and viral—with nucleotide sequence lengths (N) ranging from 100 to 10 000. The RNAs of icosahedral viruses are shown to be more compact (i.e., to have smaller $\hat R_g $R̂g) than the random RNAs. For the random sequences we find that $\hat R_g $R̂g varies as N1/3. These results are contrasted with the scaling of $\hat R_g $R̂g for ideal randomly branched polymers (N1/4), and with that from recent modeling of (relatively short, N ⩽ 161) RNA tertiary structures (N2/5).
Transportation of single cell and microbubbles by phase-shift introduced to standing leaky surface acoustic waves
Authors: Meng Long , Cai Feiyan , Zhang Zidong , Niu Lili , Jin Qiaofeng , Yan Fei , Wu Junru , Wang Zhanhui , Zheng Hairong
Published: October 2011

A microfluidic device was developed to precisely transport a single cell or multiple microbubbles by introducing phase-shifts to a standing leaky surface acoustic wave (SLSAW). The device consists of a polydimethyl-siloxane (PDMS) microchannel and two phase-tunable interdigital transducers (IDTs) for the generation of the relative phase for the pair of surface acoustic waves (SAW) propagating along the opposite directions forming a standing wave. When the SAW contacts the fluid medium inside the microchannel, some of SAW energy is coupled to the fluid and the SAW becomes the leaky surface wave. By modulating the relative phase between two IDTs, the positions of pressure nodes of the SLSAW in the microchannel change linearly resulting in the transportation of a single cell or microbubbles. The results also reveal that there is a good linear relationship between the relative phase and the displacement of a single cell or microbubbles. Furthermore, the single cell and the microbubbles can be transported over a predetermined distance continuously until they reach the targeted locations. This technique has its distinct advantages, such as precise position-manipulation, simple to implement, miniature size, and noninvasive character, which may provide an effective method for the position-manipulation of a single cell and microbubbles in many biological and biomedical applications.
Analysis of the particle stability in a new designed ultrasonic levitation device
Authors: Baer Sebastian , Andrade Marco A. B. , Esen Cemal , Adamowski Julio Cezar , Schweiger Gustav , Ostendorf Andreas
Published: October 2011

The use of acoustic levitation in the fields of analytical chemistry and in the containerless processing of materials requires a good stability of the levitated particle. However, spontaneous oscillations and rotation of the levitated particle have been reported in literature, which can reduce the applicability of the acoustic levitation technique. Aiming to reduce the particle oscillations, this paper presents the analysis of the particle stability in a new acoustic levitator device. The new acoustic levitator consists of a piezoelectric transducer with a concave radiating surface and a concave reflector. The analysis is conducted by determining numerically the axial and lateral forces that act on the levitated object and by measuring the oscillations of a sphere particle by a laser Doppler vibrometer. It is shown that the new levitator design allows to increase the lateral forces and reduce significantly the lateral oscillations of the levitated object.
Explicit correlation and basis set superposition error: The structure and energy of carbon dioxide dimer
Authors: McMahon Jordan D. , Lane Joseph R.
Published: October 2011

We have investigated the slipped parallel and t-shaped structures of carbon dioxide dimer [(CO2)2] using both conventional and explicitly correlated coupled cluster methods, inclusive and exclusive of counterpoise (CP) correction. We have determined the geometry of both structures with conventional coupled cluster singles doubles and perturbative triples theory [CCSD(T)] and explicitly correlated cluster singles doubles and perturbative triples theory [CCSD(T)-F12b] at the complete basis set (CBS) limits using custom optimization routines. Consistent with previous investigations, we find that the slipped parallel structure corresponds to the global minimum and is 1.09 kJ mol−1 lower in energy. For a given cardinal number, the optimized geometries and interaction energies of (CO2)2 obtained with the explicitly correlated CCSD(T)-F12b method are closer to the CBS limit than the corresponding conventional CCSD(T) results. Furthermore, the magnitude of basis set superposition error (BSSE) in the CCSD(T)-F12b optimized geometries and interaction energies is appreciably smaller than the magnitude of BSSE in the conventional CCSD(T) results. We decompose the CCSD(T) and CCSD(T)-F12b interaction energies into the constituent HF or HF CABS, CCSD or CCSD-F12b, and (T) contributions. We find that the complementary auxiliary basis set (CABS) singles correction and the F12b approximation significantly reduce the magnitude of BSSE at the HF and CCSD levels of theory, respectively. For a given cardinal number, we find that non-CP corrected, unscaled triples CCSD(T)-F12b/VXZ-F12 interaction energies are in overall best agreement with the CBS limit.
Tuning open-circuit voltage in organic solar cells by magnesium modified Alq3
Authors: Chou Chi-Ta , Lin Chien-Hung , Wu Meng-Hsiu , Cheng Tzu-Wei , Lee Jiun-Haw , Liu Chin-Hsin J. , Tai Yian , Chattopadhyay Surojit , Wang Juen-Kai , Chen Kuei-Hsien , Chen Li-Chyong
Published: October 2011

The low molecular weight tris-(8-hydroxyquinoline) aluminum (Alq3) has been incorporated with magnesium (Mg) that altered the nature of its opto-electronic characteristics. The lowering of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) in Mg:Alq3, compared to pure Alq3, creates a stronger field (exceeding the exciton binding energy) at the donor-acceptor junction to dissociate the photo-generated exciton and also provides a low barrier for electron transport across the device. In an electron-only device (described in the text), a current enhancement in excess of 103, with respect to pure Alq3, could be observed at 10 V applied bias. Optimized Mg:Alq3 layer, when introduced in the photovoltaic device, improves the power conversion efficiencies significantly to 0.15% compared to the pure Alq3 device. The improvement in the photovoltaic performance has been attributed to the superior exciton dissociation and carrier transport.
Transmission of subhertz electromagnetic waves from an inhomogeneous earth’s crust to the atmosphere
Authors: Shiozawa Toshiyuki
Published: October 2011

For the study of electromagnetic fields generated by precursory effects of earthquakes, the problem of transmission to the atmosphere is investigated for a subhertz plane electromagnetic wave obliquely incident from a homogeneous earth’s crust of semi-infinite extent through an inhomogeneous earth’s crust of finite thickness. To analyze the problem, the inhomogeneous earth’s crust is subdivided into a number of thin homogeneous layers. Then, an easier problem of propagation through a composite multilayered medium replacing the homogeneous and inhomogeneous earth’s crusts and the atmosphere is treated. To confirm the validity of the above formulation, an exponential inhomogeneity for the conductivity of the earth’s crust is considered for a specific example. First, for the case of the inhomogeneous earth’s crust, the overall power transmission coefficient on the earth-atmosphere interface at normal incidence is found to show a broader frequency characteristic and to take a maximum value at a definite subhertz frequency, shifting to a lower frequency. For the general case of oblique incidence as well, these features of the overall power transmission coefficient are retained except in the vicinity of the critical angle of incidence for the H-wave. At the critical angle of incidence, the power flow density carried by a surface wave along the earth-atmosphere interface becomes anomalously large for the H-wave.
A classification of the embeddings of the Diamond Lie algebra into $\mathfrak {sl}(3,\mathbb {C})$sl(3,C) and $\mathfrak {sp}(4,\mathbb {C})$sp(4,C), and restrictions of irreducible modules
Authors: Douglas Andrew , Joseph Wainright , Repka Joe
Published: October 2011

The Diamond Lie algebra $\mathfrak {D}$D is a four-dimensional, solvable Lie algebra. It is a central extension of the Poincaré Lie algebra in two dimensions. We classify the embeddings of $\mathfrak {D}$D into each of the classical Lie algebras of rank 2, namely, $\mathfrak {sl}(3,\mathbb {C})$sl(3,C) and $\mathfrak {sp}(4,\mathbb {C})$sp(4,C), up to conjugation by elements of $SL(3,\mathbb {C})$SL(3,C) or $Sp(4,\mathbb {C})$Sp(4,C), respectively. We then show that the irreducible representations of $\mathfrak {sl}(3,\mathbb {C})$sl(3,C) or $\mathfrak {sp}(4,\mathbb {C})$sp(4,C) remain indecomposable upon restriction to $\mathfrak {D}$D under any embedding.
Gel formation and aging in weakly attractive nanocolloid suspensions at intermediate concentrations
Authors: Guo Hongyu , Ramakrishnan S. , Harden James L. , Leheny Robert L.
Published: October 2011

We report x-ray photon correlation spectroscopy (XPCS) and rheometry experiments to study the temporal evolution of gel formation and aging in suspensions of silica nanocolloids possessing a tunable short-range attraction. The colloid volume fractions, ϕ = 0.20 and 0.43, are below the glass regime at high concentration and above the fractal regime at low concentration. Following a sudden initiation of the interparticle attraction, the suspensions display a protracted latency period in which they remain fluid before acquiring a measurable elastic shear modulus. The duration of the latency period and the subsequent rate of increase of the modulus vary strongly with the strength of the attraction. The XPCS results indicate dynamic heterogeneity among the colloids during this gel formation in which a growing fraction of the particles become localized. The temporal evolution of this localization correlates with that of the rheology. In particular, the time scale over which the fraction of localized particles increases tracks the duration of the latency period. Also, at ϕ = 0.20 the localization length characterizing the motion of the localized fraction scales onto the shear modulus with no free parameters as predicted by a self-consistent theory based on mode coupling [K. S. Schweizer and G. Yatsenko, J. Chem. Phys. 127, 164505 (2007)10.1063/1.2780861], while deviations from the predicted scaling at ϕ = 0.43 are observed near the gel point. The XPCS results also reveal slow, hyperdiffusive motion of the colloids in the newly formed gels that is attributed to strain from the relaxation of internal stress. While some features of this motion correlate with the evolving rheology, others appear decoupled from the macroscopic mechanical behavior.
On the stability of the massive scalar field in Kerr space-time
Authors: Beyer Horst Reinhard
Published: October 2011

The current early stage in the investigation of the stability of the Kerr metric is characterized by the study of appropriate model problems. Particularly interesting is the problem of the stability of the solutions of the Klein-Gordon equation, describing the propagation of a scalar field in the background of a rotating (Kerr-) black hole. Results suggest that the stability of the field depends crucially on its mass μ. Among others, the paper provides an improved bound for μ above which the solutions of the reduced, by separation in the azimuth angle in Boyer-Lindquist coordinates, Klein-Gordon equation are stable. Finally, it gives new formulations of the reduced equation, in particular, in form of a time-dependent wave equation that is governed by a family of unitarily equivalent positive self-adjoint operators. The latter formulation might turn out useful for further investigation. On the other hand, it is proved that from the abstract properties of this family alone it cannot be concluded that the corresponding solutions are stable.
High performance polymer light-emitting diodes with N-type metal oxide/conjugated polyelectrolyte hybrid charge transport layers
Authors: Sun Park Ji , Ram Lee Bo , Jeong Eunjae , Lee Hyun-Jung , Min Lee Ju , Kim Ji-Seon , Young Kim Jin , Young Woo Han , Ouk Kim Sang , Hoon Song Myoung
Published: October 2011

We present an interfacial engineering strategy employing n-type-metal-oxide/conjugated-polyelectrolyte (CPE) hybrid charge-transport layers for highly efficient polymer light-emitting diodes (PLEDs). The hybrid metal-oxide/CPE layer facilitates electron-injection, while blocking hole-transport, and thereby maximizes electron-hole recombination within the emitting layer. A series of metal-oxide/CPE combinations were tested in inverted PLEDs (FTO/metal-oxide/CPE/F8BT/MoO3/Au). Specifically, HfO2/CPE double layer achieved an electroluminescence (EL) efficiency of up to 25.8 cd/A (@ 6.4 V, one of the highest values reported for fluorescent PLEDs).
Time-averaging approximation in the interaction picture: Absorption line shapes for coupled chromophores with application to liquid water
Authors: Yang Mino , Skinner J. L.
Published: October 2011

The time-averaging approximation (TAA), originally developed to calculate vibrational line shapes for coupled chromophores using mixed quantum/classical methods, is reformulated. In the original version of the theory, time averaging was performed for the full one-exciton Hamiltonian, while herein the time averaging is performed on the coupling (off-diagonal) Hamiltonian in the interaction picture. As a result, the influence of the dynamic fluctuations of the transition energies is more accurately described. We compare numerical results of the two versions of the TAA with numerically exact results for the vibrational absorption line shape of the OH stretching modes in neat water. It is shown that the TAA in the interaction picture yields theoretical line shapes that are in better agreement with exact results.
Composition dependence of dispersion and bandgap properties in PZN-xPT single crystals
Authors: He Chongjun , Xu Feng , Wang Jiming , Du Chaoling , Zhu Kongjun , Liu Youwen
Published: October 2011

Refractive indices and optical transmittance spectra of (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-xPT) single crystals poled along [001] direction have been investigated. Cauchy dispersion equations of the refractive indices were obtained by least square fitting, which can be used to calculate the refractive indices in the low absorption wavelength range. After poled along [001] direction, the transmittance of PZN–12%PT single crystal is more than 65% from 0.5 to 5.8 μm, which is much higher than that of PZN–5%PT and PZN–8%PT single crystals. Optical energy bandgap was obtained from absorption coefficient spectra. Our results show that as the PT content increases, the refractive indices of PZN-xPT single crystals increase, while the optical bandgap decreases.