bluuebunny/crossref_metadata_2025 huggingface dataset:
Left atrial deformation parameters in patients with non-alcoholic fatty liver disease: a 2D speckle tracking imaging study
Authors: Kocabay Gonenc , Karabay Can Yucel , Colak Yasar , Oduncu Vecih , Kalayci Arzu , Akgun Taylan , Guler Ahmet , Kirma Cevat
Published: August 2013

The presence of the metabolic syndrome is a strong predictor for the presence of NASH (non-alcoholic steatohepatitis) in patients with NAFLD (non-alcoholic fatty liver disease). In the present study, we assessed LA (left atrial) deformation parameters in patients with NAFLD using 2D-STE (speckle tracking echocardiography) and to investigate if any changes exist between subgroups of the NAFLD. A total of 55 NAFLD patients and 21 healthy controls were included in the study. The diagnosis of NAFLD was based on liver biopsy. After patients were categorized into groups according to histopathological analysis (simple steatosis, borderline NASH, definitive NASH), all patients underwent echocardiography with Doppler examination. In the 2D-STE analysis of the left atrium, LA-Res (peak LA strain during ventricular systole), LA-Pump (peak LA strain during atrial systole), LA-SRS (peak LA strain rate during ventricular systole), LA-SRE (peak LA strain rate during early diastole) and LA-SRA (peak LA strain rate during atrial systole) were obtained. LA-Res, LA-Pump and LA-SRA were lower in the NAFLD group than in the control group. LA-Res was found to be significantly lower in NAFLD subgroups compared with healthy subjects (43.9±14.2 in healthy controls compared with 31.4±8.3 with simple steatosis, 32.8±12.8 with borderline NASH and 33.8±9.0 with definitive NASH). LA-Pump was significantly lower in the NAFLD group (18.2±3.1 in healthy controls compared with 13.3±4.7 with borderline NASH and 14.4±4.7 with definitive NASH). There were significant differences in LA-SRA between healthy controls compared with simple steatosis and borderline NASH (−1.56±0.36 compared with 1.14±0.38 and 1.24±0.32 respectively). Correlation analysis showed significant correlation of LA-Res values with E (early diastolic peak velocity)/Em (early diastolic mitral annular velocity) ratio (r=−0.50, P≤0.001), with LAVI (LA volume index; r=−0.45, P≤0.001) and with Vp (propagation velocity; r=0.39, P≤0.001). 2D-STE-based LA deformation parameters are impaired in patients with NAFLD with normal systolic function. Although LA-Res and pump function parameters might be useful in estimating LV (left ventricular) filling pressure in the NAFLD patient group, it could not be used for differentiating the subgroups.
Performance and throughput analysis of turbo decoder for the physical layer of digital‐video‐broadcasting‐satellite‐services‐to‐handhelds standard
Authors: Shrestha Rahul , Paily Roy
Published: August 2013

In this study, coding performance of turbo decoder compliant to the physical layer of digital‐video‐broadcasting‐satellite‐services‐to‐handhelds (DVB‐SH) standard for additive‐white‐Gaussian‐noise (AWGN) and frequency selective fading channels are presented. The modulation of transmitted bits is carried out with orthogonal‐frequency‐division‐multiplexing (OFDM) technique, incorporating 1 K‐fast‐Fourier‐transform (1K‐FFI) where each subcarrier is modulated using quadrature‐phase‐shift‐keying (QPSG) or quadrature‐amplitude‐modulation (QAM) schemes. Performance analysis of turbo decoder for the decoding iterations of 3, 8, 14 and 18 as well as the sliding window sizes of 10, 20, 30 and 40 are investigated for both the channels. Discussion on the values of these design metrics to achieve optimum coding performance is also presented. The optimisation of system throughput for turbo decoder based on the decoding iteration and sliding window size for various processor speed ranging from 200 MHz to 1 GHz is carried out. Such an analysis is presented for non‐parallel radix‐2 as well as parallel radix‐4 configuration of turbo decoder to meet the system throughput specification of third‐generation wireless communication standard ranging from 100 to 300 Mbps. The coding performance of turbo decoder based on max‐log‐MAP, log‐MAP and Maclaurin series‐based algorithms are studied for both the channel conditions. Simultaneously, the running time for each of these algorithm in a 64 bit processor is also presented for comparison. Finally, the coding performance of turbo decoder for various code rates of 1/5, 2/9, 1/4, 2/7, 1/3, 2/5 and 1/2 are carried out.
Graph‐based low complexity detection algorithms in multiple‐input–multiple‐out systems: an edge selection approach
Authors: Lv Tiejun , Long Feichi
Published: August 2013

In this study, the problem of low complexity multiple‐input–multiple‐out signal detection based on belief propagation (BP) is addressed. The authors propose an edge selection approach that works on factor graph model to cut down the number of circles and high complexity of standard BP algorithm. The message passing from factor nodes to variable nodes is updated by only partial edges, and the mean feedback method is designed to compensate the information loss brought by the edge selection. Both binary and high‐order modulations are considered, and the scheme of mapping between bit soft output and modulation symbols when computing the feedback information is discussed. In addition, a minimum mean‐square error filter initialised algorithm is proposed, in which the initial message of BP detection is exploited. Both binary and high‐order modulations are discussed as well when the authors design this initial message. Simulation results along with convergence and complexity analyses verify that the proposed edge selection approach can achieve good performance with low complexity, and significantly outperform the existing methods with comparative complexity. Moreover, our approach has asymptotic optimality and is a self‐adapting scheme, which can achieve the trade‐off between performance and complexity by varying the number of selected edges.
Intrusion damage assessment for multi‐stage attacks for clouds
Authors: Arshad Junaid , Ajmal Azad Muhammad , Ali Jokhio Imran , Townend Paul
Published: August 2013

Clouds represent a major paradigm shift from contemporary systems, inspiring the contemporary approach to computing. They present fascinating opportunities to address dynamic user requirements with the provision of flexible computing infrastructures that are available on demand. Clouds, however, introducing novel challenges particularly with respect to security that require dedicated efforts to address them. This study is focused at one such challenge, that is, determining the extent of damage caused by an intrusion for a victim virtual machine. It has significant implications especially with respect to effective response to the intrusion. This study presents the efforts to address this challenge for Clouds in the form of a novel scheme for intrusion damage assessment for Clouds. In addition to its context‐aware operation, the scheme facilitates protection against multi‐stage attacks. The study also includes the formal specification and evaluation of the scheme, which successfully demonstrate its effectiveness to achieve rigorous damage assessment for Clouds.
Capacity of multiple beamformed spatial stream transmission in millimetre‐wave communication channels
Authors: Joon Lee Seung , Yong Lee Woo
Published: August 2013

This study deals with the study on the performance of the hybrid transmission scheme combining both beamforming and spatial multiplexing for multiple spatial streams. The capacity of the hybrid scheme is evaluated and compared with that of the beamforming scheme for a single spatial stream in both line‐of‐sight and multi‐path channels. Two kinds of hybrid schemes are considered: the shared antenna architecture, where each antenna processes all spatial streams and the split antenna architecture, where each antenna processes only one spatial stream. The effects of the channel parameters, such as the antenna spacing, the existence of reflected paths etc. On the capacity and the optimal beams and powers are examined. The frequency‐selective property of the capacity and optimal beams and powers are also investigated. In this study, a scenario is assumed, where the same analogue radio frequency (RF) beamforming vector (or matrix) is applied to all subcarriers whereas the digital baseband power allocation is executed individually at each subcarrier.
Hierarchical modulated quadrature amplitude modulation with signal space diversity and maximal ratio combining reception in Nakagami‐m fading channels
Authors: Saeed Ayesha , Quazi Tahmid , Xu Hongjun
Published: August 2013

This study combines hierarchical modulation with signal space diversity (SSD) to present an unequal error protection scheme with improved bit‐error rate (BER) performance for single as well as multiple antenna reception by employing maximal ratio combing in Nakagami‐m fading channels. The optimal rotation angles for different constellation priority parameter α are derived. A theoretical BER expression in Nakagami‐m fading channels using the nearest neighbour approximation approach is also derived. This is confirmed as a valid performance approximation for single and multiple antenna reception through simulations. The resultant scheme produces improved BER performance for both important and less important data without consuming any additional power than a non‐SSD system at the cost of increased complexity at detection. Specifically, performance gains of up to 18 and 17 dB at a BER of 1 × 10−5 for base and refinement bits, respectively, are observed for single receive antenna with Nakagami m = 1. A further improvement of roughly 3 dB at a BER of 1 × 10−6 for base bits at N = 3 receiver antennas is found as hierarchy is increased. Although the gain is observed to decrease as m increases, a gain of 14 dB at 1 × 10−6 for α = 4 is achieved even as m increases from m = 1 to m = 3.
Combined power control and link selection in device‐to‐device enabled cellular systems
Authors: Cheng Yongsheng , Gu Yuantao , Lin Xiaokang
Published: August 2013

Device‐to‐device (D2D) communication underlaying cellular systems is proposed to support short‐range data‐intensive services. In a D2D‐enabled system, a closely located user pair is allowed to communicate over a direct data link, instead of being relayed through the network. In this study, based on the power control framework in traditional cellular networks, a combined power control and link selection algorithm with temporary removal for D2D‐enabled systems is proposed. It is proved that the proposed algorithm converges to the optimal power and link selection vector in all feasible systems. In an infeasible system, convergence of the temporary removal algorithm cannot be guaranteed. Therefore two adaptive gradual removal algorithms are proposed, which are suitable for lightly and heavily loaded systems, respectively. Numerical results show that both of the proposed algorithms outperform the existing ones in terms of outage probability and convergence rate.
Exact outage analysis of underlay cooperative cognitive networks over Nakagami‐m fading channels
Authors: Ho‐Van Khuong
Published: August 2013

This paper studies the outage performance behaviour of underlay cooperative cognitive networks over Nakagami‐m fading channels. For time savings in collecting simulation results, the authors propose a new outage probability expression. Notably, this expression is quite general, taking into account practical operation conditions such as interference power constraint, maximum transmit power constraint, correlation among received signal‐to‐noise ratios, non‐identically and independently distributed Nakagami‐m fading channels and the maximum ratio combining receiver. Moreover, it is useful in obtaining numerical results for performance comparison between dual‐hop communications and cooperative communications in underlay cognitive networks. Interestingly, analytical results illustrate that like dual‐hop cognitive networks, cooperative cognitive ones experience an error floor but the latter significantly outperform the former at almost no cost of power and bandwidth.
Circular polariser for use in a gyro‐travelling wave amplifier
Authors: Robertson Craig W. , Young Alan R. , Ronald Kevin , Cross Adrian W. , Whyte Colin G.
Published: August 2013

A corrugated rectangular waveguide, commonly used in radio frequency antennas applications, was considered for use in a gyro‐TWA experiment. This waveguide transducer produced broadband circularly polarised radiation in the Ka‐band frequency range (26–40 GHz). Computer simulations, using computer simulation technology Microwave Studio®, were carried out and predicted return losses exceeding 30 dB and a 6° phase variation for 20% bandwidth centred at 31 GHz. Comparison between experimental measurements and simulations showed good agreement. The performance of this polariser was also compared to that of a conventional elliptical converter. Owing to its broadband performance the authors consider some of the technical aspects of applying this component to a Ka‐band gyro‐TWA experiment.
Microwave imaging for brain stroke detection using Born iterative method
Authors: Ireland David , Bialkowski Konstanty , Abbosh Amin
Published: August 2013

Microwave imaging reconstruction is applied to an anatomically realistic, numerical head phantom using the Born iterative method for detection of a haemorrhagic stroke within the brain tissues. A forward model is used to estimate back‐scattered signals which are subsequently used in the image reconstruction process. Image reconstruction using excitation signals at 850 MHz is shown to produce the emulated stroke with a high contrast particular to the estimated conductivity profile.
Chaos and noise
Authors: He Temple , Habib Salman
Published: August 2013

Simple dynamical systems—with a small number of degrees of freedom—can behave in a complex manner due to the presence of chaos. Such systems are most often (idealized) limiting cases of more realistic situations. Isolating a small number of dynamical degrees of freedom in a realistically coupled system generically yields reduced equations with terms that can have a stochastic interpretation. In situations where both noise and chaos can potentially exist, it is not immediately obvious how Lyapunov exponents, key to characterizing chaos, should be properly defined. In this paper, we show how to do this in a class of well-defined noise-driven dynamical systems, derived from an underlying Hamiltonian model.
Acid pretreatment of bagasse pith at low temperature with steam-assisted heating
Authors: Bianfang Lu , Suping Zhang , Gang Wang , Yuancheng Chen , Zhengwei Ren , Qingli Xu , Yongjie Yan
Published: August 2013

In this paper, dilute acid pretreatment of bagasse pith was investigated at low temperature. Process parameters varied including mass ratio of liquid to solid (r = 6:1–12:1 l/kg), reaction temperature (T = 100 °C–130 °C), and acid concentration (c = 0.75 wt. %–1.5 wt. %) in order to effectively transform hemicellulose to fermentable sugar to improve the utilization of bagasse pith. The effects of dilute acid pretreatment were evaluated by fermentable sugar yield and decomposition products concentration. The optimum pretreatment conditions for depolymerization of hemicellulose bagasse pith was obtained at r = 10:1 l/kg, T = 120 °C, c = 1.0 wt. %, t = 16 min. From this paper, it could be concluded that dilute acid pretreatment can be successfully applied to bagasse pith to achieve high yield of xylose (84.41%) with acceptable levels of fermentation inhibitors formation.
Reducing the propensity for unphysical wavefunction symmetry breaking in multireference calculations of the excited states of semiconductor clusters
Authors: Shu Yinan , Levine Benjamin G.
Published: August 2013

Unphysical spatial symmetry breaking in multiconfigurational self-consistent field calculations can lead to undesirable artifacts in the potential energy surfaces and electronic properties of molecules. Herein, we report several examples of such symmetry breaking in calculations of the excited states of small semiconductor clusters and related molecules at the state-averaged complete active space self-consistent field (SA-CASSCF) level of theory. A multireference approach is proposed to reduce its incidence: the singly excited active space complete active space configuration interaction (SEAS-CASCI) method. In SEAS-CASCI, the orbitals are determined by variationally minimizing an energy expression that does not depend on the off-diagonal Hamiltonian matrix elements which drive symmetry breaking at the SA-CASSCF level of theory. By application to several highly symmetric molecules, SEAS-CASCI is demonstrated to reduce the propensity for unphysical spatial symmetry breaking and eliminate resulting errors in the potential energy surfaces and molecular properties relative to the SA-CASSCF description. The SEAS method is also found to eliminate unphysical wavefunction distortion in asymmetric molecules. Finally, SEAS-CASCI is demonstrated to accurately describe the biradicaloid region of the potential energy surface of ethylene.
Magnetocaloric effect of field-induced ferromagnet BaFeO3
Authors: Mizumaki Masaichiro , Yoshii Kenji , Hayashi Naoaki , Saito Takashi , Shimakawa Yuichi , Takano Mikio
Published: August 2013

We have investigated the magnetocaloric effect (MCE) of a perovskite oxide, BaFeO3, that shows ferromagnetism by the aid of a small external field of ∼3 kOe (3.5 μB/Fe, TC = 111 K). The magnetization is found to change almost reversibly in both field and temperature cycles. Hence, magnetic and thermal hysteretic losses are negligibly low during refrigeration, a property that is suitable for application. The reversible MCE is likely to arise from the absence of an orbital magnetic moment of Fe ions which are essentially in the Fe3+L state (L: ligand hole). The magnetic entropy change and refrigerant capacity near the TC are ∼5.8 J kg−1 K−1 and ∼172 J kg−1, respectively, both of which are comparable to those of ferromagnetic perovskite manganites. As BaFeO3 contains no rare metals and is stable against corrosion, the material can be regarded as a candidate refrigerant material.
Acoustoelectric effects in very high-mobility p-SiGe/Ge/SiGe heterostructure at low temperatures in high magnetic fields
Authors: Drichko I. L. , Malysh V. A. , Smirnov I. Yu. , Suslov A. V. , Mironov O. A. , Kummer M. , von Känel H.
Published: August 2013

The contactless Surface Acoustic Wave (SAW) technique was implemented to probe the high-frequency (ac) conductivity in a high-mobility p-SiGe/Ge/SiGe structure in the integer quantum Hall (IQHE) regime. The structure was grown by low-energy plasma-enhanced chemical vapor deposition and comprised a two-dimensional channel formed in a compressively strained Ge layer. It was investigated at temperatures of 0.3–5.8 K and magnetic fields up to 18 T at various SAW intensities. In the IQHE regime, in minima of the conductivity oscillations with small filling factors, holes are localized. The ac conductivity is of the hopping nature and can be described within the “two-site” model. Furthermore, the dependence of the ac conductivity on the electric field of the SAW was determined. The manifestation of non-linear effects is interpreted in terms of nonlinear percolation-based conductivity.
Defects and electronic transport in hydrogenated amorphous SiC films of interest for low dielectric constant back end of the line dielectric systems
Authors: Pomorski T. A. , Bittel B. C. , Cochrane C. J. , Lenahan P. M. , Bielefeld J. , King S. W.
Published: August 2013

Back end of line dielectrics with low dielectric constants are needed for current and future integrated circuit technology. However, an understanding of the defects that cause leakage currents and limit reliability in these films is not yet developed. We utilize conventional electron paramagnetic resonance (EPR), electrically detected magnetic resonance (EDMR), and leakage current measurements, complimented by Fourier transform infrared spectroscopy and Rutherford back scattering results, to investigate a-SiC:H dielectrics which have great potential use for back end of line dielectrics. We observe a strong correlation between conventional EPR defect density measurements and leakage currents. There is also a very strong correlation between hydrogen content and both leakage current and EPR defect density. The close correspondence between the EPR results and the leakage currents strongly indicates that the defects observed by EPR are largely responsible for the leakage currents and likely limit the dielectric reliability. Important reliability phenomena in these films are time-dependent dielectric breakdown and stress induced leakage current. Additionally, we have utilized EDMR via spin dependent trap assisted tunneling to investigate the direct link between defects observed in EPR and electrical transport.
Direct evaluation of the position dependent diffusion coefficient and persistence time from the equilibrium density profile in anisotropic fluids
Authors: Olivares-Rivas Wilmer , Colmenares Pedro J. , López Floralba
Published: August 2013

We derive expressions for the transverse diffusion coefficient D(z) and the average persistence time τ(z; L) within a layer of width L, for particles of a non-homogeneous fluid enclosed in a planar nanopore. The method allows the direct evaluation of these position-dependent dynamical quantities from the equilibrium local particle density profile. We use results for the density and persistence time profiles from the virtual layer molecular dynamics method to numerically assess the significance of the Smoluchowski approximation.
Generation of strong electric fields in an ice film capacitor
Authors: Shin Sunghwan , Kim Youngsoon , Moon Eui-seong , Lee Du Hyeong , Kang Hani , Kang Heon
Published: August 2013

We present a capacitor-type device that can generate strong electrostatic field in condensed phase. The device comprises an ice film grown on a cold metal substrate in vacuum, and the film is charged by trapping Cs+ ions on the ice surface with thermodynamic surface energy. Electric field within the charged film was monitored through measuring the film voltage using a Kelvin work function probe and the vibrational Stark effect of acetonitrile using IR spectroscopy. These measurements show that the electric field can be increased to ∼4 × 108 V m−1, higher than that achievable by conventional metal plate capacitors. In addition, the present device may provide several advantages in studying the effects of electric field on molecules in condensed phase, such as the ability to control the sample composition and structure at molecular scale and the spectroscopic monitoring of the sample under electric field.
Channel-length scaling for effects of single defects in carbon nanotube transistors
Authors: Wang Neng-Ping , Xu Xiao-Jun
Published: August 2013

We investigate channel-length scaling characteristics for effects of a single charged defect in a carbon nanotube field-effect transistor (CNFET), using the nonequilibrium Greens function method. We find that the threshold voltage shift due to a single charge in midchannel increases with the decreasing channel length. In a p-type CNFET, the relative current reduction in the on-state due to a positive charge and the relative current change in the turn-on region due to a negative charge increase apparently with the decreasing channel length. The threshold voltage shift and relative current change caused by a single charge for short channel CNFETs increases with the gate-oxide thickness much faster than that for long channel CNFETs. For a short channel p-type CNFET, the current reduction in the on-state due to a positive charge may be larger than 60% and the threshold voltage shift due to a negative charge may amount to 0.6 V.
Etched graphene quantum dots on hexagonal boron nitride
Authors: Engels S. , Epping A. , Volk C. , Korte S. , Voigtländer B. , Watanabe K. , Taniguchi T. , Trellenkamp S. , Stampfer C.
Published: August 2013

We report on the fabrication and characterization of etched graphene quantum dots (QDs) on hexagonal boron nitride (hBN) and SiO2 with different island diameters. We perform a statistical analysis of Coulomb peak spacings over a wide energy range. For graphene QDs on hBN, the standard deviation of the normalized peak spacing distribution decreases with increasing QD diameter, whereas for QDs on SiO2 no diameter dependency is observed. In addition, QDs on hBN are more stable under the influence of perpendicular magnetic fields up to 9 T. Both results indicate a substantially reduced substrate induced disorder potential in graphene QDs on hBN.
Near-forward Raman scattering by bulk and surface phonon-polaritons in the model percolation-type ZnBeSe alloy
Authors: Hajj Hussein R. , Pagès O. , Firszt F. , Paszkowicz W. , Maillard A.
Published: August 2013

We study the bulk and surface phonon-polaritons of the Zn0.67Be0.33Se zincblende alloy by near-forward Raman scattering. The short (Be-Se) bond exhibits a distinct percolation doublet in the conventional backscattering Raman spectra, corresponding to a three-mode behavior in total [1×(Zn-Se), 2×(Be-Se)] for Zn0.67Be0.33Se. This offers an opportunity to achieve a refined understanding of the phonon-polariton modes of a zincblende alloy beyond the current two-mode approximation, corresponding to a [1×(Zn-Se), 1×(Be-Se)] description in the present case. The discussion is supported by contour modeling of the Raman signals of the multi-mode bulk and surface phonon-polaritons within the formalism of the linear dielectric response.
Analysis of lateral transport through the inversion layer in amorphous silicon/crystalline silicon heterojunction solar cells
Authors: Filipič Miha , Holman Zachary C. , Smole Franc , De Wolf Stefaan , Ballif Christophe , Topič Marko
Published: August 2013

In amorphous/crystalline silicon heterojunction solar cells, an inversion layer is present at the front interface. By combining numerical simulations and experiments, we examine the contribution of the inversion layer to lateral transport and assess whether this layer can be exploited to replace the front transparent conductive oxide (TCO) in devices. For this, heterojunction solar cells of different areas (2 × 2, 4 × 4, and 6 × 6 mm2) with and without TCO layers on the front side were prepared. Laser-beam-induced current measurements are compared with simulation results from the ASPIN2 semiconductor simulator. Current collection is constant across millimeter distances for cells with TCO; however, carriers traveling more than a few hundred microns in cells without TCO recombine before they can be collected. Simulations show that increasing the valence band offset increases the concentration of holes under the surface of n-type crystalline silicon, which increases the conductivity of the inversion layer. Unfortunately, this also impedes transport across the barrier to the emitter. We conclude that the lateral conductivity of the inversion layer may not suffice to fully replace the front TCO in heterojunction devices.
Multilayer HfO2/TiO2 gate dielectric engineering of graphene field effect transistors
Authors: Deen David A. , Champlain James G. , Koester Steven J.
Published: August 2013

Graphene field effect transistors and capacitors that employ ultra-thin atomic layer deposited high-κ TiO2 dielectrics are demonstrated. Of the three TiO2 gate insulation schemes employed, the sequentially deposited HfO2:TiO2 gate insulator stack enabled the reduction of equivalent oxide thickness while simultaneously providing an ultra-thin gate insulation layer that minimized gate leakage current. The multilayer gate insulation scheme demonstrates a means for advanced device scaling in graphene-based devices.
On the beneficial role of noise in resistive switching
Authors: Patterson G. A. , Fierens P. I. , Grosz D. F.
Published: August 2013

We study the effect of external noise on resistive switching. Experimental results on a manganite sample are presented showing that there is an optimal noise amplitude that maximizes the contrast between high and low resistive states. By means of numerical simulations, we study the causes underlying the observed behavior. We find that experimental results can be related to general characteristics of the equations governing the system dynamics.
Solution-state NMR investigation of the sorptive fractionation of dissolved organic matter by alkaline mineral soils
Authors: Mitchell Perry J. , Simpson André J. , Soong Ronald , Oren Adi , Chefetz Benny , Simpson Myrna J.
Published: August 2013

Environmental context Dissolved organic matter plays a key role in global carbon cycling and environmental contaminant transport. We use one- and two-dimensional solution-state nuclear magnetic resonance spectroscopy to characterise dissolved organic matter before and after binding to alkaline subsoils with low organic carbon content. The results show that the dissolved organic matter is selectively fractionated through preferential binding of specific organic carbon functional groups. Abstract Sorption to clay minerals is a prominent fate of dissolved organic matter (DOM) in terrestrial environments. Previous studies have observed that DOM is selectively fractionated by interactions with both pure clay minerals and acidic mineral soils. However, the specific DOM functional groups that preferentially sorb to mineral surfaces in alkaline soils require further examination because higher basicity could change the nature of these sorptive interactions. Biosolids-derived DOM was characterised using one- and two-dimensional solution-state NMR spectroscopy before and after sorption to three alkaline subsurface mineral soils with varying mineralogy. Carboxylic DOM components sorbed preferentially to all soils, likely due to cation bridging and ligand exchange mechanisms. Aliphatic constituents were selectively retained only by a soil with high clay mineral content, possibly by van der Waals interactions with montmorillonite surfaces. Polar carbohydrate and peptide components of the DOM did not exhibit preferential sorption and may remain mobile in the soil solution and potentially stimulate microbial activity. A relatively low signal from aromatic DOM components prevented a full assessment of their sorption behaviour. The results suggest that DOM is selectively fractionated by similar interactions in both acidic and alkaline soils that may play a key role in the chemical and biochemical processes of subsurface environments.
Asymptotic inequalities for positive crank and rank moments
Authors: Bringmann Kathrin , Mahlburg Karl
Published: August 2013

Andrews, Chan, and Kim recently introduced a modified definition of crank and rank moments for integer partitions that allows the study of both even and odd moments. In this paper, we prove the asymptotic behavior of these moments in all cases. Our main result states that the two families of moment functions are asymptotically equal, but the crank moments are also asymptotically larger than the rank moments.

Andrews, Chan, and Kim also gave a combinatorial description for the differences of the first crank and rank moments that they named the ospt-function. Our main results therefore also give the asymptotic behavior of the ospt-function (and its analogs for higher moments), and we further determine the behavior of the ospt-function modulo

2
2

by relating its parity to Andrews’ spt-function.
1-O-alkyl-2-acetyl-sn-glycerol: a platelet-activating factor metabolite with biological activity in vascular smooth muscle cells.
Authors: Stoll L L , Figard P H , Yerram N R , Yorek M A , Spector A A
Published: August 2013

Platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine; PAF) is a potent vasoactive ether lipid produced by activated blood cells and endothelial cells. Vascular smooth muscle cells partially convert exogenous PAF to 1-O-alkyl-2-acetyl-sn-glycerol (AAG), a biologically active diacylglycerol analogue. AAG is formed rapidly (less than 15 s) after exposure of the smooth muscle cells and does not appear to be a substrate for diacylglycerol kinase in these cells. Although most of the compound is metabolized to 1-O-alkyl-sn-glycerol, a small quantity remains as AAG for greater than or equal to 6 h. AAG inhibits phorbol ester binding, and it is as effective an activator of protein kinase C as diolein in an in vitro assay. Furthermore, AAG and PAF produce the same pattern of effects on smooth muscle cell proliferation. These observations suggest that at least some of the actions of PAF in vascular smooth muscle may be mediated through the formation of AAG, a stable, bioactive metabolite that appears to function as a diacylglycerol analogue.
Stable, resealable pores formed in sea urchin eggs by electric discharge (electroporation) permit substrate loading for assay of enzymes in vivo.
Authors: Swezey R R , Epel D
Published: August 2013

We describe a simple electroporation procedure for loading suspensions of unfertilized sea urchin eggs with impermeant small molecules under conditions that allow close to 90% successful fertilization and development. Poration is carried out in a low-Ca2+ medium that mimicks the intracellular milieu. The induced pores remain open for several minutes in this medium, allowing loading of the cells; resealing is achieved by adding back millimolar calcium ions to the medium. While the pores are open, an influx of exogenous molecules and efflux of endogenous metabolites takes place, and the eggs can lose up to 40% of their ATP content and still survive. Introduced metabolites are utilized by the cells, e.g., introduced 3H-thymidine is incorporated into DNA. This procedure will be useful for loading impermeant substrates into eggs, permitting in vivo assessment of metabolism, and also for introducing other interesting impermeant molecules, such as inhibitors, fluorescent indicators, etc. Though the details may differ, the principle of electroporation in an intracellular-like medium may prove to be useful for loading other cell types with minimal loss of viability.
Mitogen-induced oscillations of cytosolic Ca2+ and transmembrane Ca2+ current in human leukemic T cells.
Authors: Lewis R S , Cahalan M D
Published: August 2013

A rapid rise in the level of cytosolic free calcium ([Ca2+]i) is believed to be one of several early triggering signals in the activation of T lymphocytes by antigen. Although Ca2+ release from intracellular stores and its contribution to Ca2+ signaling in many cell types is well documented, relatively little is known regarding the role and mechanism of Ca2+ entry across the plasma membrane. We have investigated mitogen-triggered Ca2+ signaling in individual cells of the human T-leukemia-derived line, Jurkat, using fura-2 imaging and patch-clamp recording techniques. Phytohemagglutinin (PHA), a mitogenic lectin, induces repetitive [Ca2+]i oscillations in these cells peaking at micromolar levels with a period of 90-120 s. The oscillations depend critically upon Ca2+ influx across the plasma membrane, as they are rapidly terminated by removal of extracellular Ca2+, addition of Ca(2+)-channel blockers such as Ni2+ or Cd2+, or membrane depolarization. Whole-cell and perforated-patch recording methods were combined with fura-2 measurements to identify the mitogen-activated Ca2+ conductance involved in this response. A small, highly selective Ca2+ conductance becomes activated spontaneously in whole-cell recordings and in response to PHA in perforated-patch experiments. This conductance has properties consistent with a role in T-cell activation, including activation by PHA, lack of voltage-dependent gating, inhibition by Ni2+ or Cd2+, and regulation by intracellular Ca2+. Moreover, a tight temporal correlation between oscillations of Ca2+ conductance and [Ca2+]i suggests a role for the membrane Ca2+ conductance in generating [Ca2+]i oscillations in activated T cells.
TGF-beta: problems and prospects.
Authors: Sporn M B , Roberts A B
Published: August 2013

TGF-beta research is proceeding at an exponential pace. Studies in this area have become increasingly relevant to many areas of cell regulation, continually providing new surprises and findings. One may confidently predict that TGF-beta will be one of the key molecules in future attempts to establish an integrated view of the processes whereby cells coordinate their own and mutual functions. We have seen only the beginning, and this minireview is only a glimpse.
Affinity modulation of the alpha IIb beta 3 integrin (platelet GPIIb-IIIa) is an intrinsic property of the receptor.
Authors: O'Toole T E , Loftus J C , Du X P , Glass A A , Ruggeri Z M , Shattil S J , Plow E F , Ginsberg M H
Published: August 2013

To analyze the basis of affinity modulation of integrin function, we studied cloned stable Chinese hamster ovary cell lines expressing recombinant integrins of the beta 3 family (alpha IIb beta 3 and alpha v beta 3). Antigenic and peptide recognition specificities of the recombinant receptors resembled those of the native receptors found in platelets or endothelial cells. The alpha IIb beta 3-expressing cell line (A5) bound RGD peptides and immobilized fibrinogen (Fg) but not soluble fibrinogen or the activation-specific monoclonal anti-alpha IIb beta 3 (PAC1), indicating that it was in the affinity state found on resting platelets. Several platelet agonists failed to alter the affinity state of ("activate") recombinant alpha IIb beta 3. The binding of soluble Fg and PAC1, however, was stimulated in both platelets and A5 cells by addition of IgG papain-digestion products (Fab) fragments of certain beta 3-specific monoclonal antibodies. These antibodies stimulated PAC1 binding to platelets fixed under conditions rendering them unresponsive to other agonists. Addition of these antibodies to detergent-solubilized alpha IIb beta 3 also stimulated specific Fg binding. These data demonstrate that certain anti-beta 3 antibodies activate alpha IIb beta 3 by acting directly on the receptor, possibly by altering its conformation. Furthermore, they indicate that the activation state of alpha IIb beta 3 is a property of the receptor itself rather than of the surrounding cell membrane microenvironment.
Microtubule perturbation inhibits intracellular transport of an apical membrane glycoprotein in a substrate-dependent manner in polarized Madin-Darby canine kidney epithelial cells.
Authors: van Zeijl M J , Matlin K S
Published: August 2013

The effects of microtubule perturbation on the transport of two different viral glycoproteins were examined in infected Madin-Darby canine kidney (MDCK) cells grown on both permeable and solid substrata. Quantitative biochemical analysis showed that the microtubule-depolymerizing drug nocodazole inhibited arrival of influenza hemagglutinin on the apical plasma membrane in MDCK cells grown on both substrata. In contrast, the microtubule-stabilizing drug taxol inhibited apical appearance of hemagglutinin only when MDCK cells were grown on permeable substrata. On the basis of hemagglutinin mobility on sodium dodecyl sulfate gels and its sensitivity to endo H, it was evident that nocodazole and taxol arrested hemagglutinin at different intracellular sites. Neither drug caused a significant increase in the amount of hemagglutinin detected on the basolateral plasma membrane domain. In addition, neither drug had any noticeable effect on the transport of the vesicular stomatitis virus (VSV)-G protein to the basolateral surface. These results shed light on previous conflicting reports using this model system and support the hypothesis that microtubules play a role in the delivery of membrane glycoproteins to the apical, but not the basolateral, domain of epithelial cells.
Nuclear receptors for retinoic acid and thyroid hormone regulate transcription of keratin genes.
Authors: Tomic M , Jiang C K , Epstein H S , Freedberg I M , Samuels H H , Blumenberg M
Published: August 2013

In the epidermis, retinoids regulate the expression of keratins, the intermediate filament proteins of epithelial cells. We have cloned the 5' regulatory regions of four human epidermal keratin genes, K#5, K#6, K#10, and K#14, and engineered constructs in which these regions drive the expression of the CAT reporter gene. By co-transfecting the constructs into epithelial cells along with the vectors expressing nuclear receptors for retinoic acid (RA) and thyroid hormone, we have demonstrated that the receptors can suppress the promoters of keratin genes. The suppression is ligand dependent; it is evident both in established cell lines and in primary cultures of epithelial cells. The three RA receptors have similar effects on keratin gene transcription. Our data indicate that the nuclear receptors for RA and thyroid hormone regulate keratin synthesis by binding to negative recognition elements in the upstream DNA sequences of the keratin genes. RA thus has a twofold effect on epidermal keratin expression: qualitatively, it regulates the regulators that effect the switch from basal cell-specific keratins to differentiation-specific ones; and quantitatively, it determines the level of keratin synthesis within the cell by direct interaction of its receptors with the keratin gene promoters.
Alternative patterns of mitogenesis and cell scattering induced by acidic FGF as a function of cell density in a rat bladder carcinoma cell line.
Authors: Vallés A M , Tucker G C , Thiery J P , Boyer B
Published: August 2013

The dual function exerted by acidic fibroblast growth factor (aFGF) in a rat bladder carcinoma cell line has been explored under two different conditions of culture density. At low cell density, aFGF promotes the epithelium-to-mesenchyme transition of NBT-II cells characterized by cell dissociation, morphological changes toward a fibroblastic-like phenotype, and acquisition of cell motility. Under these conditions, NBT-II cells are unresponsive to the growth-promoting effect of aFGF. At high cell density, aFGF is a potent mitogenic factor, but its scattering activity is essentially abrogated. Slight modifications in the binding of aFGF to its specific receptors were observed at high cell density; these changes correlated with a downregulation of receptors with no apparent change in their molecular form. NBT-II cells located at the edge of artificial wounds mimicked the behavior of subconfluent cells, because they did not proliferate upon aFGF treatment. Furthermore, in large-sized NBT-II colonies, peripheral cells were the first to dissociate in response to aFGF. Altogether, our results suggest that the cellular response to multifunctional growth factors might depend on the localization within the responding cell population.
Tyrosine phosphorylation of the gap junction protein connexin43 is required for the pp60v-src-induced inhibition of communication.
Authors: Swenson K I , Piwnica-Worms H , McNamee H , Paul D L
Published: August 2013

Gap junction communication in some cells has been shown to be inhibited by pp60v-src, a protein tyrosine kinase encoded by the viral oncogene v-src. The gap junction protein connexin43 (Cx43) has been shown to be phosphorylated on serine in the absence of pp60v-src and on both serine and tyrosine in cells expressing pp60v-src. However, it is not known if the effect of v-src expression on communication results directly from tyrosine phosphorylation of the Cx43 or indirectly, for example, by activation of other second-messenger systems. In addition, the effect of v-src expression on communication based on other connexins has not been examined. We have used a functional expression system consisting of paired Xenopus oocytes to examine the effect of v-src expression on the regulation of communication by gap junctions comprised of different connexins. Expression of pp60v-src completely blocked the communication induced by Cx43 but had only a modest effect on communication induced by connexin32 (Cx32). Phosphoamino acid analysis showed that pp60v-src induced tyrosine phosphorylation of Cx43, but not Cx32. A mutation replacing tyrosine 265 of Cx43 with phenylalanine abolished both the inhibition of communication and the tyrosine phosphorylation induced by pp60v-src without affecting the ability of this protein to form gap junctions. These data show that the effect of pp60v-src on gap junctional communication is connexin specific and that the inhibition of Cx43-mediated junctional communication by pp60v-src requires tyrosine phosphorylation of Cx43.
Domain deletion in the extracellular portion of the EGF-receptor reduces ligand binding and impairs cell surface expression.
Authors: Lax I , Bellot F , Honegger A M , Schmidt A , Ullrich A , Givol D , Schlessinger J
Published: August 2013

Cultured NIH-3T3 cells were transfected with cDNA constructs encoding human epidermal growth factor-receptor (EGF-R)* and two deletion mutants in the extracellular portion of the receptor molecule. One mutant is devoid of 124 amino-terminal amino acids, and the other lacks 76 residues. Mutant receptors were not delivered to the cell surface unless the transfected cells contained also endogenous EGF-Rs, suggesting that receptor interaction complements the mutation and allows surface display of mutant receptors. Immunoprecipitation experiments revealed an association between mutant and endogenous EGF-Rs when both proteins were expressed in the same cell. Hence, receptor-oligomers may exist in the plane of the membrane even in the absence of ligand binding, and oligomerization may play a role in normal trafficking of EGF-Rs to the cell surface. Mutant receptors retained partial ligand binding activity as 125I-labeled EGF was covalently cross-linked to both mutant receptors, and EGF stimulated, albeit weakly, their protein tyrosine kinase activity. Both mutant EGF-Rs bind EGF with a 10-fold lower affinity than that of the solubilized wild type EGF-R. These results provide further evidence that the region flanked by the two cysteine-rich domains plays a crucial role in defining ligand-binding specificity of EGF-R.
The in vitro biological effect of nerve growth factor is inhibited by synthetic peptides.
Authors: Longo F M , Vu T K , Mobley W C
Published: August 2013

Nerve growth factor (NGF)1 is a neurotrophic polypeptide that acts via specific receptors to promote the survival and growth of neurons. To delineate the NGF domain(s) responsible for eliciting biological activity, we synthesized small peptides corresponding to three regions in NGF that are hydrophilic and highly conserved. Several peptides from mouse NGF region 26-40 inhibited the neurite-promoting effect of NGF on sensory neurons in vitro. Inhibition was sequence-specific and could be overcome by increasing the concentration of NGF. Moreover, peptide actions were specific for NGF-mediated events in that they failed to block the neurotrophic activity of ciliary neuronotrophic factor (CNTF) or phorbol 12-myristate 13-acetate (PMA). In spite of the inhibition of NGF activity, peptides did not affect the binding of radiolabeled NGF. These studies define one region of NGF that may be required for neurotrophic activity.