bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of conductive impurities on electrical conductivity in polycrystalline olivine
Authors: Watson Heather C. , Roberts Jeffery J. , Tyburczy James A.
Published: January 2010

Bulk electrical conductivity and impedance spectroscopy of single crystal and polycrystalline San Carlos olivine with carbon or iron sulfide impurities on grain boundaries were measured at 1GPa and 350°C–1200°C in a piston cylinder apparatus. The addition of 0.1 wt% (∼0.16 vol%) C causes series‐type grain boundary impedance in the samples that slightly decreases the bulk conductivity of the system. In contrast, the addition of 1.0 vol% sulfide results in conductivity much higher than plain olivine, but still lower than that of a fully interconnected sulfide phase. The sulfide is partially connected on the grain boundaries and edges and has reached the electrical percolation threshold. The effect adding sulfide is similar to the effect of adding 0.01%–0.1% H to olivine. It may not always be necessary to have hydrogen or connected melt or fluid to account for anomalously high conductivity in some parts of the mantle or crust.
Carbon sequestration and greenhouse gas emissions in urban turf
Authors: Townsend‐Small Amy , Czimczik Claudia I.
Published: January 2010

Undisturbed grasslands can sequester significant quantities of organic carbon (OC) in soils. Irrigation and fertilization enhance CO2 sequestration in managed turfgrass ecosystems but can also increase emissions of CO2 and other greenhouse gases (GHGs). To better understand the GHG balance of urban turf, we measured OC sequestration rates and emission of N2O (a GHG ∼ 300 times more effective than CO2) in Southern California, USA. We also estimated CO2 emissions generated by fuel combustion, fertilizer production, and irrigation. We show that turf emits significant quantities of N2O (0.1–0.3 g N m−2 yr−1) associated with frequent fertilization. In ornamental lawns this is offset by OC sequestration (140 g C m−2 yr−1), while in athletic fields, there is no OC sequestration because of frequent surface restoration. Large indirect emissions of CO2 associated with turfgrass management make it clear that OC sequestration by turfgrass cannot mitigate GHG emissions in cities.
A statistical analysis of vertical shear effect on tropical cyclone intensity change in the North Atlantic
Authors: Zeng Zhihua , Wang Yuqing , Chen Lianshou
Published: January 2010

Based on the best track data of tropical cyclones (TCs) in the North Atlantic and the NCEP/NCAR reanalysis during 1981–2008,the effect of vertical wind shear (VWS) between different vertical levels and with different directions of shear on TC intensity change for TCs of different intensities, translational speeds, and latitudes were statistically analyzed. The results show that TC intensity change and VWS are generally negatively correlated, indicating the overall negative effect of VWS on TC intensity. The strong, slow moving, and low latitude TCs are strongly affected by VWS in a deep layer, while the weak, fast moving, and high latitude TCs are subject to strong effect by VWS in the mid‐lower troposphere. Furthermore, overall easterly shear, especially in the mid‐lower troposphere, has considerably weaker effects on TC intensity change than westerly shear because part of the easterly shear could be offset by the beta‐induced northwesterly shear.
Modeling of thundercloud screening charges: Implications for blue and gigantic jets
Authors: Riousset Jeremy A. , Pasko Victor P. , Krehbiel Paul R. , Rison William , Stanley Mark A.
Published: January 2010

A two‐dimensional axisymmetric model of charge relaxation in the conducting atmosphere is used in conjunction with a probabilistic lightning model to demonstrate how realistic cloud electrodynamics lead to the development of blue and gigantic jets. The model accounts for time‐dependent conduction currents and screening charges formed under the influence of the thundercloud charge sources. Particular attention is given to numerical modeling of the screening charges near the cloud boundaries. The modeling results demonstrate the important role of the screening charges in local enhancement of the electric field and/or reduction of net charge in the upper levels of the thundercloud. The charge relaxation model presented in this work confirms the previous results obtained with a simpler model by Krehbiel et al. (2008), specifically that the accumulation of screening charges near the thundercloud top produces a charge configuration leading to the initiation of blue jets, while the effective mixing of these charges with the upper thundercloud charge may lead to the formation of gigantic jets.
Multispacecraft observation of electron pitch angle distributions in magnetotail reconnection
Authors: Wang Rongsheng , Lu Quanming , Huang Can , Wang Shui
Published: January 2010

In this paper, we present Cluster observations of a magnetotail reconnection event without the presence of an obvious guide magnetic field and analyze electron pitch angle distributions in the vicinity of the X line and the outflow region, respectively. In the vicinity of the X line, at lower energies the distributions are highly anisotropic (field‐aligned bidirectional anisotropic), while at higher energies, the electrons are observed to flow away from the X line along the magnetic field lines. The electron distributions change largely in the outflow region. At the edge of the outflow region, at lower energies, the electrons flow toward the X line, while the electrons at higher energies are directed away from the X line. When the satellites approach the center of the current sheet, at lower energies, the electrons have field‐aligned bidirectional distributions, while at higher energies, the electron distributions are isotropic. The generation mechanisms of such distributions are explained by following typical electron trajectories in the electric and magnetic fields of magnetic reconnection, which are obtained in two‐dimensional particle‐in‐cell simulations. It is shown that the observed high‐energy electrons directed away from the X line both in the vicinity of the X line and in the outflow region are due to the acceleration by the reconnection electric field near the X line, and the field‐aligned bidirectional distributions at lower energies are caused by the effects of the magnetic mirror in the reconnection site. The isotropic distributions at higher energies in the outflow region are the results of the electron stochastic motions when their gyroradii are comparable to the curvature radii of the magnetic field lines.
Ship‐based measurement of air‐sea CO2 exchange by eddy covariance
Authors: Miller Scott D. , Marandino Christa , Saltzman Eric S.
Published: January 2010

A system for the shipboard measurement of air‐sea CO2 fluxes by eddy covariance was developed and tested. The system was designed to reduce two major sources of experimental uncertainty previously reported. First, the correction for in situ water vapor fluctuations (the “Webb” correction) was reduced by 97% by drying the air sample stream. Second, motion sensitivity of the gas analyzer was reduced by using an open‐path type sensor that was converted to a closed‐path configuration to facilitate drying of the air stream. High‐quality CO2 fluxes were obtained during 429 14 min flux intervals during two cruises in the North Atlantic. The results suggest that the gas analyzer resolved atmospheric CO2 fluctuations well below its RMS noise level. This noise was uncorrelated with the vertical wind and therefore filtered out by the flux calculation. Using climatological data, we estimate that the techniques reported here could enable high‐quality measurements of air‐sea CO2 flux over much of the world oceans.
Atmospheric origins of perchlorate on Mars and in the Atacama
Authors: Catling D. C. , Claire M. W. , Zahnle K. J. , Quinn R. C. , Clark B. C. , Hecht M. H. , Kounaves S.
Published: January 2010

Isotopic studies indicate that natural perchlorate is produced on Earth in arid environments by the oxidation of chlorine species through pathways involving ozone or its photochemical products. With this analogy, we propose that the arid environment on Mars may have given rise to perchlorate through the action of atmospheric oxidants. A variety of hypothetical pathways can be proposed including photochemical reactions, electrostatic discharge, and gas‐solid reactions. Because perchlorate‐rich deposits in the Atacama desert are closest in abundance to perchlorate measured at NASA's Phoenix Lander site, we made a preliminary study of the means to produce Atacama perchlorate to help shed light on the origin of Martian perchlorate. We investigated gas phase pathways using a 1‐D photochemical model. We found that perchlorate can be produced in sufficient quantities to explain the abundance of perchlorate in the Atacama from a proposed gas phase oxidation of chlorine volatiles to perchloric acid. The feasibility of gas phase production for the Atacama provides justification for future investigations of gas phase photochemistry as a possible source for Martian perchlorate.
Enhanced Weight Loss Following Coadministration of Pramlintide With Sibutramine or Phentermine in a Multicenter Trial
Authors: Aronne Louis J. , Halseth Amy E. , Burns Colleen M. , Miller Stephan , Shen Larry Z.
Published: January 2010

Preclinical evidence suggests that pharmacotherapy for obesity using combinations of agents targeted at distinct regulatory pathways may produce robust additive or synergistic effects on weight loss. This randomized placebo‐controlled trial examined the safety and efficacy of the amylin analogue pramlintide alone or in combination with either phentermine or sibutramine. All patients also received lifestyle intervention. Following a 1‐week placebo lead‐in, 244 obese or overweight, nondiabetic subjects (88% female; 41 ± 11 years; BMI 37.7 ± 5.4 kg/m2; weight 103 ± 19 kg; mean ± s.d.) received placebo subcutaneously (sc) t.i.d., pramlintide sc (120 µg t.i.d.), pramlintide sc (120 µg t.i.d.) + oral sibutramine (10 mg q.a.m.), or pramlintide sc (120 µg t.i.d.) + oral phentermine (37.5 mg q.a.m.) for 24 weeks. Treatment was single‐blind for subjects receiving subcutaneous medication only and open‐label for subjects in the combination arms. Weight loss achieved at week 24 with either combination treatment was greater than with pramlintide alone or placebo (P < 0.001; 11.1 ± 1.1% with pramlintide + sibutramine, 11.3 ± 0.9% with pramlintide + phentermine, −3.7 ± 0.7% with pramlintide; −2.2 ± 0.7% with placebo; mean ± s.e.). Elevations from baseline in heart rate and diastolic blood pressure were demonstrated with both pramlintide + sibutramine (3.1 ± 1.2 beats/min, P < 0.05; 2.7 ± 0.9 mm Hg, P < 0.01) and pramlintide + phentermine (4.5 ± 1.3 beats/min, P < 0.01; 3.5 ± 1.2 mm Hg, P < 0.001) using 24‐h ambulatory monitoring. However, the majority of subjects receiving these treatments remained within normal blood pressure ranges. These results support the potential of pramlintide‐containing combination treatments for obesity.
Obese Adolescents Show Impaired Meal Responses of the Appetite‐Regulating Hormones Ghrelin and PYY
Authors: Mittelman Steven D. , Klier Katie , Braun Sharon , Azen Colleen , Geffner Mitchell E. , Buchanan Thomas A.
Published: January 2010

Ghrelin and peptide YY (PYY) stimulate hunger and satiety, respectively. The physiology of these hormones during normal meal intake remains unclear. This study was designed to compare the responses of these two hormones to meal intake between lean and obese Hispanic adolescents. A total of 10 obese and 7 lean Hispanic youth, aged 11–14 years, consumed two mixed meals, one small and one large, during which plasma measurements of active and total ghrelin and total PYY were obtained. Obese subjects tended to consume more calories during the small meal than lean subjects, although this did not reach statistical significance. Intake of the small meal significantly suppressed active ghrelin and stimulated PYY levels in the lean subjects, and these changes were further accentuated by the large meals. In obese subjects, the suppression of active ghrelin and stimulation of PYY by caloric intake were blunted. Interestingly, a paradoxical stimulation of active ghrelin levels was noted during the small meals in both lean and obese subjects. This stimulation was not seen during the larger meals in lean subjects, but remained present in the obese subjects. Thus, meal‐related changes in active ghrelin and PYY are blunted in obese as compared to lean Hispanic subjects. This blunting could contribute to the development or worsening of obesity.
JNK Deficiency Enhances Fatty Acid Utilization and Diverts Glucose From Oxidation to Glycogen Storage in Cultured Myotubes
Authors: Vijayvargia Ravi , Mann Kara , Weiss Harvey R. , Pownall Henry J. , Ruan Hong
Published: January 2010

Although germ‐line deletion of c‐Jun NH2‐terminal kinase (JNK) improves overall insulin sensitivity in mice, those studies could not reveal the underlying molecular mechanism and the tissue site(s) in which reduced JNK activity elicits the observed phenotype. Given its importance in nonesterified fatty acids (NEFA) and glucose utilization, we hypothesized that the insulin‐sensitive phenotype associated with Jnk deletion originates from loss of JNK function in skeletal muscle. Short hairpin RNA (shRNA)–mediated gene silencing was used to identify the functions of JNK subtypes in regulating energy metabolism and metabolic responses to elevated concentrations of NEFA in C2C12 myotubes, a cellular model of skeletal muscle. We show for the first time that cellular JNK2‐ and JNK1/JNK2‐deficiency divert glucose from oxidation to glycogenesis due to increased glycogen synthase (GS) activity and induction of Pdk4. We further show that JNK2‐ and JNK1/JNK2‐deficiency profoundly increase cellular NEFA oxidation, and their conversion to phospholipids and triglyceride. The increased NEFA utilization was coupled to increased expressions of selective NEFA handling genes including Cd36, Acsl4, and Chka, and enhanced palmitic acid (PA)‐dependent suppression of acetyl‐CoA carboxylase (Acc). In JNK‐intact cells, PA inhibited insulin signaling and glycogenesis. Although silencing Jnk1 and/or Jnk2 prevented PA‐induced inhibition of insulin signaling, it did not completely block decreased insulin‐mediated glycogenesis, thus indicating JNK‐independent pathways in the suppression of glycogenesis by PA. Muscle‐specific inhibition of JNK2 (or total JNK) improves the capacity of NEFA utilization and glycogenesis, and is a potential therapeutic target for improving systemic insulin sensitivity in type 2 diabetes (T2D).
Fumagillin Reduces Adipose Tissue Formation in Murine Models of Nutritionally Induced Obesity
Authors: Lijnen Henri R. , Frederix Liesbeth , van Hoef Berthe
Published: January 2010

The effect of fumagillin (a methionine aminopeptidase‐type 2 (Met‐AP2) inhibitor, with antiangiogenic properties) was investigated in murine models of diet‐induced obesity. Eleven‐week‐old male C57Bl/6 mice (group 1) were given fumagillin by oral gavage at a dose of 1 mg/kg/day during 4 weeks while fed a high‐fat diet (HFD) (20.1 kJ/g), and control mice (group 2) received solvent and were pair‐fed. At the end of the experiment, body weights in group 1 were significantly lower as compared to group 2 (P < 0.0005). The subcutaneous (SC) and gonadal (GON) fat mass was also significantly lower in group 1 (P < 0.005 and P < 0.05, respectively). Adipocytes were smaller in adipose tissues of mice in group 1, associated with higher adipocyte density. Blood vessel density normalized to adipocyte density was lower in group 1 adipose tissues. However, in mice with established obesity monitored to maintain the same body weight and fat mass as controls, short‐term fumagillin administration was also associated with adipocyte hypotrophy (P = 0.01) without affecting blood vessel size or density. Thus, treatment with fumagillin impaired diet‐induced obesity in mice, associated with adipocyte hypotrophy but without marked effect on adipose tissue angiogenesis.
Integrated structural control of cage-type mesoporous platinum possessing both tunable large mesopores and variable surface structures by block copolymer-assisted Pt deposition in a hard-template
Authors: Kuroda Yoshiyuki , Yamauchi Yusuke , Kuroda Kazuyuki
Published: January 2010

Cage-type mesoporous Pt with tunable large mesopores possessing smooth and rough pore surfaces were prepared selectively by the deposition of Pt with and without a block copolymer in a hard-template, respectively.
Towards chiral polystyrene based materials: controlled polymerization of p-(2,2′-diphenylethyl)styrene
Authors: Hohberger Christiane , Beckerle Klaus , Okuda Jun
Published: January 2010

p-(2,2′-Diphenylethyl)styrene (DPES) was polymerized with the homochiral postmetallocene catalyst dichloro{trans-1,2-dithiocyclohexanediyl-2,2′-bis(4,6-di-tert-butylphenolato)}titanium/MAO. Optically active isotactic polymers were obtained by a controlled reduction of the molecular weight, employing diethylzinc as CTA. Polymers with molecular weights below Mn of 50,000 g mol−1 showed specific rotation values ([α]23D) between ±0.2 and 2.2.
Electrical oscillations induced by the metal-insulator transition in VO2
Authors: Kim Hyun-Tak , Kim Bong-Jun , Choi Sungyoul , Chae Byung-Gyu , Lee Yong Wook , Driscoll T. , Qazilbash M. M. , Basov D. N.
Published: January 2010

We systematically investigate the characteristics of an electrical oscillation observed in two-terminal vanadium dioxide (VO2) devices. These oscillations are observed at room temperature in a simple electrical circuit without inductive components. The circuit is composed only of a dc voltage source, the VO2 device, and a standard resistor connected in series with the device. We explain why the observed oscillations are a result of the percolative metal-to-insulator transition (MIT) of VO2 and the coexistence of the metal and insulating phases. Specifically, oscillations are attributed to the construction and destruction of capacitive regions composed of regions of the semiconducting phase, (as dielectric material) and metallic phase electron carriers, induced by the MIT (as capacitor electrodes). Since the coexistence of these phases—and thus the capacitive regions—is destroyed by elevated temperature, the MIT oscillation is not explained in terms of significant heat input but rather in terms of a voltage-triggered effect. It is also discussed whether the current jump at the onset of the oscillations is driven by Mott physics or by Peierls physics relying on a structural phase transition. Furthermore, the electrical parameter space surrounding these oscillations is explored, and a generation window is identified. Within this generation window, the oscillation frequency can be continuously tuned by adjusting applied voltage or by an external circuit component, such as resistor or added capacitor. The frequency of oscillations can be increased up to >1 MHz.
Crystal and rotator phases of n-alkanes: A molecular dynamics study
Authors: Wentzel Nathaniel , Milner Scott T.
Published: January 2010

Normal alkanes have a simple molecular structure, but display a surprising variety of ordered phases, including an orthorhombic crystal, followed on heating by two partially ordered rotator phases RI and RII. These phases are interesting both because of the weakly first-order transitions that separate them, and because rotator phases are implicated in the nucleation of crystals in polyethylene. To understand this interesting and technologically important phenomenon, a clear picture of the rotator phase is essential. We conducted all-atom simulations of pure C23 and mixed C21–C23 normal alkanes. Among potentials we tried, only Flexible Williams gave good agreement with the experimental sequence of phases and transition temperatures. Physical properties of the simulated phases, including lattice dimensions and transition entropy between orthorhombic and rotator RII phase are in good agreement with experiment. We define order parameters for investigating pretransitional fluctuations in RI and RII phases; we observed only very short-range correlations in these phases, but slower temperature scans may be necessary to properly investigate these weakly first-order transitions.
A slow atom source using a collimated effusive oven and a single-layer variable pitch coil Zeeman slower
Authors: Bell S. C. , Junker M. , Jasperse M. , Turner L. D. , Lin Y.-J. , Spielman I. B. , Scholten R. E.
Published: January 2010

We describe a simple slow atom source for loading a rubidium magneto-optical trap. The source includes an effusive oven with a long heated collimation tube. Almost all components are standard vacuum parts. The heating elements and thermocouples are external to the vacuum, protecting them from the hostile hot alkali environment and allowing repair without breaking vacuum. The thermal source is followed by a Zeeman slower with a single-layer coil of variable winding pitch. The single-layer design is simple to construct and has low inductance which allows for rapid switching of the magnetic field. The coil pitch was determined by fitting the analytic form of the magnetic field for a variable winding pitch to the desired magnetic field profile required to slow atoms. The measured magnetic field for the constructed coil is in excellent agreement with the desired field. The source produces atoms at 35 m/s with a flux up to 2×1010 cm−2 s−1 at 200 °C.
Temperature control design for a high-resolution gamma-ray tomography detector
Authors: Bieberle André , Schleicher Eckhard , Hampel Uwe
Published: January 2010

In this paper, a thermal control design for a high-resolution gamma-ray computed tomography detector is presented. It accounts for the generation of heat produced by active electronic components as well as heat transfer from external heat sources. The development and implementation of this feature were motivated by stringent requirements for measurement accuracy at thermal hydraulic test facilities, where ambient thermal conditions are constantly changing. As a first step, the thermal behavior of the existing tomography detector was analyzed, critical components were identified, and different approaches for heat removal were tested. Eventually, an improved thermal detector design was elaborated and a controlled active cooling system was implemented. Performance tests proved its effectiveness and accuracy improvement.
Infrared luminescence of Tm3+/Yb3+ codoped lanthanum aluminum germanate glasses
Authors: Zhang Qiang , Chen Guorong , Zhang Guang , Qiu Jianrong , Chen Danping
Published: January 2010

Tm 3 + doped and Tm3+/Yb3+ codoped lanthanum aluminum germanate (LAG) glasses are prepared by melt-quenching method and characterized optically. Based on the measurement of absorption spectrum, Judd–Ofelt intensity parameters (Ω2,Ω4,Ω6) are calculated. The radiation emission rates, branching ratios, and lifetimes of Tm3+ are calculated to evaluate the spectroscopic properties of Tm3+ in LAG glass. The infrared emission properties of the samples are investigated and the results show that the 1.8 μm emission can be greatly enhanced by adding proper amount of Yb3+ under the excitation of 980 nm. The energy transfer processes of Yb3+–Yb3+ and Yb3+–Tm3+ are analyzed, and the results show that Yb3+ ions can transfer their energy to Tm3+ ions with high efficiency and large energy transfer coefficient.
Direct observation of high velocity current induced domain wall motion
Authors: Heyne L. , Rhensius J. , Bisig A. , Krzyk S. , Punke P. , Kläui M. , Heyderman L. J. , Le Guyader L. , Nolting F.
Published: January 2010

We study fast vortex wall propagation in Permalloy wires induced by 3 ns short current pulses with sub 100 ps rise time using high resolution magnetic imaging at zero field. We find a constant domain wall displacement after each current pulse as well as current induced domain wall structure changes, even at these very short timescales. The domain wall velocities are found to be above 100 m/s and independent of the domain wall spin structure. Comparison to experiments with longer pulses points to the pulse shape as the origin of the high velocities.
Dielectric spectroscopy of Pb0.92La0.08Zr0.52Ti0.48O3 films on hastelloy substrates with and without LaNiO3 buffer layers
Authors: Narayanan Manoj , Ma Beihai , Balachandran U. (Balu) , Li Wei
Published: January 2010

Pb 0.92 La 0.08 Zr 0.52 Ti 0.48 O 3 (PLZT) films were deposited by sol-gel synthesis on Hastelloy substrates with and without a LaNiO3 buffer. The dielectric properties were measured as a function of temperature and frequency to study the cause of dielectric degradation in PLZT films directly on hastelloy substrates. These measurements indicated an increased charge carrier activity in films without a buffer layer. We propose that a region of the film closer to the substrate surface is more oxygen deficient than the bulk and is responsible for the degradation in properties rather than the presence of a low parasitic secondary-phase interfacial layer such as NiOx.
Asymmetry in photocurrent enhancement by plasmonic nanoparticle arrays located on the front or on the rear of solar cells
Authors: Beck F. J. , Mokkapati S. , Polman A. , Catchpole K. R.
Published: January 2010

We show experimentally that there is asymmetry in photocurrent enhancement by Ag nanoparticle arrays located on the front or on the rear of solar cells. The scattering cross-section calculated for front- and rear-located nanoparticles can differ by up to a factor of 3.7, but the coupling efficiency remains the same. We attribute this to differences in the electric field strength and show that the normalized scattering cross-section of a front-located nanoparticle varies from two to eight depending on the intensity of the driving field. In addition, the scattering cross-section of rear-located particles can be increased fourfold using ultrathin spacer layers.
Effects of particle size and ligand density on the kinetics of receptor-mediated endocytosis of nanoparticles
Authors: Yuan Hongyan , Zhang Sulin
Published: January 2010

We elucidate, from thermodynamic arguments, the governing factors of receptor-mediated endocytosis of nanoparticles (NPs). We show that the endocytic energetics specifies a minimal particle size and a minimal ligand density below which endocytosis is not possible. Due to the entropic penalty involved in ligand-receptor binding, endocytosis may occur with a large fraction of ligands unbound with receptors. Our analyses suggest that the endocytic time depends interrelatedly on the particle size and ligand density. There exists an optimal condition at which the endocytic time minimizes. These findings may provide valuable guidance to the rational designs of NP-based biomarkers and anticancer bioagents.
Magnetization reversal process in Fe/FePt films
Authors: Tsai Jai-Lin , Tzeng Hsin-Te , Lin Guo-Bin
Published: January 2010

A soft/hard Fe/FePt bilayer with perpendicular magnetization was prepared on a glass substrate. Controlling the Fe layer thickness allowed modification of the hysteresis loops from rigid magnet with perpendicular magnetization to exchange-spring like magnet with parallel magnetization due to the nanoscale soft/hard interface coupling. For rigid magnetic films, the magnetization was reversed at a single switching field and interpreted by the two-spin model. In an exchange-spring like film, the in-plane magnetization reversal process was in two-steps and resulted from domain wall nucleation and propagation from the Fe layer into the FePt layer.
Electronic structure of self-assembled InGaAs/GaAs quantum rings studied by capacitance-voltage spectroscopy
Authors: Lei W. , Notthoff C. , Lorke A. , Reuter D. , Wieck A. D.
Published: January 2010

Self-assembled InGaAs quantum rings, embedded in a GaAs matrix, were investigated using magneto-capacitance-voltage spectroscopy. The magnetic-field dispersion of the charging energies exhibits characteristic features for both the first and second electron, which can be attributed to a ground state transition from l=0 into l=−1, and a ground state transition from l=−1 into l=−2, respectively. Furthermore, using a combination of capacitance-voltage spectroscopy and one-dimensional numerical simulations, the conduction band structure of these InGaAs quantum rings was determined.
Communications: Spatial separation of enantiomers by coherent optical means
Authors: Li Xuan , Shapiro Moshe
Published: January 2010

We show that it is possible to spatially separate a (“racemic”) mixture of left-handed and right-handed chiral molecules using optically induced forces. The separation is affected by the irradiation of the racemic mixture with three spatially inhomogeneous and partially overlapping cw laser fields, giving rise to enantiomeric and vibrational dependent light-induced forces. Two experimental arrangements, one consisting of placing the racemate in 1 mK optical trap, the second composed of a tightly skimmed molecular beam of the racemic mixture, forming one arm of a four-sided cavity, are numerically tested by performing quantum wave packet propagation and classical trajectories. Both the classical and the quantum simulations show an essentially perfect spatial separation between enantiomers of several vibrational states.
Synergistic antitumor effects of combined cathepsin B and cathepsin Z deficiencies on breast cancer progression and metastasis in mice
Authors: Sevenich Lisa , Schurigt Uta , Sachse Kathrin , Gajda Mieczyslaw , Werner Fee , Müller Sebastian , Vasiljeva Olga , Schwinde Anne , Klemm Nicole , Deussing Jan , Peters Christoph , Reinheckel Thomas
Published: January 2010

The lysosomal cysteine proteases cathepsin B (Ctsb) and cathepsin Z (Ctsz, also called cathepsin X/P) have been implicated in cancer pathogenesis. Compensation of Ctsb by Ctsz inCtsb−/−mice has been suggested. To further define the functional interplay of these proteases in the context of cancer, we generated Ctsz null mice, crossed them with Ctsb-deficient mice harboring a transgene for the mammary duct–specific expression of polyoma middle T oncogene (PymT), and analyzed the effects of single and combined Ctsb and Ctsz deficiencies on breast cancer progression. Single Ctsb deficiency resulted in delayed detection of first tumors and reduced tumor burden, whereas Ctsz-deficient mice had only a prolonged tumor-free period. However, only a trend toward reduced metastatic burden without statistical significance was detected in both single mutants. Strikingly, combined loss of Ctsb and Ctsz led to additive effects, resulting in significant and prominent delay of early and advanced tumor development, improved histopathologic tumor grading, as well as a 70% reduction in the number of lung metastases and an 80% reduction in the size of these metastases. We conclude that the double deficiency of Ctsb and Ctsz exerts significant synergistic anticancer effects, whereas the single deficiencies demonstrate at least partial reciprocal compensation.
Coherent concepts are computed in the anterior temporal lobes
Authors: Lambon Ralph Matthew A. , Sage Karen , Jones Roy W. , Mayberry Emily J.
Published: January 2010

In his
Philosophical Investigations
, Wittgenstein famously noted that the formation of semantic representations requires more than a simple combination of verbal and nonverbal features to generate conceptually based similarities and differences. Classical and contemporary neuroscience has tended to focus upon how different neocortical regions contribute to conceptualization through the summation of modality-specific information. The additional yet critical step of computing coherent concepts has received little attention. Some computational models of semantic memory are able to generate such concepts by the addition of modality-invariant information coded in a multidimensional semantic space. By studying patients with semantic dementia, we demonstrate that this aspect of semantic memory becomes compromised following atrophy of the anterior temporal lobes and, as a result, the patients become increasingly influenced by superficial rather than conceptual similarities.
Formation and dissociation of M1muscarinic receptor dimers seen by total internal reflection fluorescence imaging of single molecules
Authors: Hern Jonathan A. , Baig Asma H. , Mashanov Gregory I. , Birdsall Berry , Corrie John E. T. , Lazareno Sebastian , Molloy Justin E. , Birdsall Nigel J. M.
Published: January 2010

G-protein–coupled receptors (GPCRs) are the largest family of transmembrane signaling proteins in the human genome. Events in the GPCR signaling cascade have been well characterized, but the receptor composition and its membrane distribution are still generally unknown. Although there is evidence that some members of the GPCR superfamily exist as constitutive dimers or higher oligomers, interpretation of the results has been disputed, and recent studies indicate that monomeric GPCRs may also be functional. Because there is controversy within the field, to address the issue we have used total internal reflection fluorescence microscopy (TIRFM) in living cells to visualize thousands of individual molecules of a model GPCR, the M1muscarinic acetylcholine receptor. By tracking the position of individual receptors over time, their mobility, clustering, and dimerization kinetics could be directly determined with a resolution of ~30 ms and ~20 nm. In isolated CHO cells, receptors are randomly distributed over the plasma membrane. At any given time, ~30% of the receptor molecules exist as dimers, and we found no evidence for higher oligomers. Two-color TIRFM established the dynamic nature of dimer formation with M1receptors undergoing interconversion between monomers and dimers on the timescale of seconds.
Structure of the
Plasmodium falciparum
M17 aminopeptidase and significance for the design of drugs targeting the neutral exopeptidases
Authors: McGowan Sheena , Oellig Christine A. , Birru Woldeamanuel A. , Caradoc-Davies Tom T. , Stack Colin M. , Lowther Jonathan , Skinner-Adams Tina , Mucha Artur , Kafarski Pawel , Grembecka Jolanta , Trenholme Katharine R. , Buckle Ashley M. , Gardiner Donald L. , Dalton John P. , Whisstock James C.
Published: January 2010

Current therapeutics and prophylactics for malaria are under severe challenge as a result of the rapid emergence of drug-resistant parasites. The human malaria parasite
Plasmodium falciparum
expresses two neutral aminopeptidases,
Pf
A-M1 and
Pf
A-M17, which function in regulating the intracellular pool of amino acids required for growth and development inside the red blood cell. These enzymes are essential for parasite viability and are validated therapeutic targets. We previously reported the x-ray crystal structure of the monomeric
Pf
A-M1 and proposed a mechanism for substrate entry and free amino acid release from the active site. Here, we present the x-ray crystal structure of the hexameric leucine aminopeptidase,
Pf
A-M17, alone and in complex with two inhibitors with antimalarial activity. The six active sites of the
Pf
A-M17 hexamer are arranged in a disc-like fashion so that they are orientated inwards to form a central catalytic cavity; flexible loops that sit at each of the six entrances to the catalytic cavern function to regulate substrate access. In stark contrast to
Pf
A-M1,
Pf
A-M17 has a narrow and hydrophobic primary specificity pocket which accounts for its highly restricted substrate specificity. We also explicate the essential roles for the metal-binding centers in these enzymes (two in
Pf
A-M17 and one in
Pf
A-M1) in both substrate and drug binding. Our detailed understanding of the
Pf
A-M1 and
Pf
A-M17 active sites now permits a rational approach in the development of a unique class of two-target and/or combination antimalarial therapy.
Perceived health from biological motion predicts voting behaviour
Authors: Kramer Robin S. S. , Arend Isabel , Ward Robert
Published: January 2010

Body motion signals socially relevant traits like the sex, age, and even the genetic quality of actors and may therefore facilitate various social judgements. By examining ratings and voting decisions based solely on body motion of political candidates, we considered how the candidates’ motion affected people's judgements and voting behaviour. In two experiments, participants viewed stick figure motion displays made from videos of politicians in public debate. Participants rated the motion displays for a variety of social traits and then indicated their vote preference. In both experiments, perceived physical health was the single best predictor of vote choice, and no two-factor model produced significant improvement. Notably, although attractiveness and leadership correlated with voting behaviour, neither provided additional explanatory power to a single-factor model of health alone. Our results demonstrate for the first time that motion can produce systematic vote preferences.
Saudi youth: the illusion of transnational freedom
Authors: Yamani Mai
Published: January 2010

The paper deals with the matter of Saudi youth as this correlates to increasing social problems of unemployment and sometimes antithetical cultural currents in conjunction with the spread of alternative media and a burgeoning public ‘space’ provided by the Internet. A third of the Kingdom’s population is now under the age of 14, and how the youth are alternatively absorbed into the system or marginalized depends upon not only simple economic factors, but also tribal and sectarian affiliation which is downplayed or masked by the regime. The underrepresented among average Ḥijāzi youth who do not sense affiliation with the Wahhābi trends of the Najd as well as minority sects including Shāꜥah in the Eastern Province and Ismāꜥīlis is in the ꜥAsīr are increasingly coming to identify with transnational groups outside the Kingdom, and whether the ruling family – which itself is facing a potential crisis of succession – can successfully maintain national unity which would entail genuine reform and a reduction in the role of Wahhābi elements as well as economic reform remains to be seen. The traditional strategies that have relied on garnering the loyalty of the population through subsidies of electricity and such like have worn thin, as has the supposition that the Āl Saꜥūd as ostensibly the ūlī al-amr and custodians of the two Holy Shrines of Mecca and Medina ought to receive unquestioning loyalty.
The failure of sanctions and the evolution of international policy towards Iraq, 1990–2003
Authors: Dodge Toby
Published: January 2010

The day after Iraq’s August 1990 invasion of Kuwait, the United Nations Security Council passed Resolution 660 condemning Iraq’s aggression and demanding that it withdraw. A week later it passed Resolution 661 demanding that UN Member States prevent all trade and financial transactions with Iraq. In all of its previous history, the Security Council had only imposed sanctions to discipline errant states twice before. The precedent used for the drafting of Resolution 661 was the sanctions imposed on Rhodesia in December 1966 after it had declared independence from Britain. This signified something of an empirical vacuum where those drafting resolutions in New York deployed a set of assumptions that gave both the theory and practise of sanctions their coherence. It was assumed that a state, when faced with an on-going economic embargo, would be forced to react in predictable ways. If the application of sanctions caused enough suffering within society, then popular discontent would eventually force the ruling elite to change policy and work to lift sanctions as theoretically the state cannot escape public opinion or ignore a population whose economic well-being has been seriously damaged by the application of sanctions. In 1990–1991 the economic and political assumptions underpinning the practice of sanctions appeared to make Iraq an ideal candidate for their application given that 95% of Iraq’s foreign exchange earnings came directly from oil exports. In addition, the economy was dependent upon food imports costing US$3 billion annually. However, these assumptions along with the normative vision that gave sanctions their ideological coherence were proven wrong as the Iraqi regime manoeuvred to entrench itself further within society and actually strengthen its position.
Enhanced red emission in ZnMoO4 : Eu3+ by charge compensation
Authors: Xie An , Yuan Ximing , Wang Fengxiang , Shi Yu , Mu Zhongfei
Published: January 2010

Eu3+ doped ZnMoO4 with charge compensation were synthesized by solid-state reactions. The phosphors with different charge compensation approaches,
and
,
were studied in detail. All of the phosphors can be effectively excited by 396 and 467 nm light, and exhibit superior red emission around 614 nm to ZnMoO4 : Eu3+ without charge compensation, which implies that efficient charge compensation can promote the luminescence of Eu3+ in ZnMoO4. The influence of sintering temperature on the luminescent properties of phosphors with different charge compensation approaches is also discussed. The result indicates that appropriate charge compensation can not only enhance the relative intensity but can also improve the colour purity of the red phosphor.
Plasmon flow control at gap waveguide junctions using square ring resonators
Authors: Liu Jianlong , Fang Guangyu , Zhao Haifa , Zhang Yan , Liu Shutian
Published: January 2010

A compact add-drop coupler with square ring resonator (SRR) in gap plasmon waveguide is studied. It is shown that there exist both travelling-wave and standing-wave resonant modes in the resonator due to the influence of the four corners in the square ring. Based on SRR, a new type of two-dimensional plasmonic L-shaped bend is proposed. The compact geometry and high add-drop efficiency of the proposed structure enable the realization of flexible flow control at waveguide junctions, e.g. T-splitter and waveguide cross intersections, in nano scale. The optical field propagation patterns in the gap waveguide junctions equipped with SRRs are investigated by the finite-difference time-domain method.
Calibration of a miniaturized retarding field analyzer for low-temperature plasmas: geometrical transparency and collisional effects
Authors: Baloniak Tim , Reuter Rüdiger , Flötgen Christoph , von Keudell Achim
Published: January 2010

Retarding field analyzers (RFAs) are important diagnostics to measure fluxes and energies of ions impinging onto the wall of a plasma reactor. Any quantitative use of the data requires a proper calibration, which is here performed for a miniaturized RFA. The calibration accounts for the transparencies of the RFA grids as well as for collisions inside the RFA. An analytical model is derived which covers both geometrical and collisional effects. The model is calibrated and experimentally verified using a Langmuir probe. We find that the transparency of an RFA is a random variable which depends on the individual alignment of the RFA grids. Collisions inside the RFA limit the ion current transfer through the RFA at higher pressures. A simple method is presented which allows one to remove these artefacts from the RFA data and to obtain quantitative ion velocity distributions.
Surface energy controlled preferential orientation of thin films
Authors: Körber C , Suffner J , Klein A
Published: January 2010

The preferred crystalline orientation of magnetron sputtered transparent conducting SnO2 : Sb thin films is controlled by the oxygen content in the sputter gas. Reducing conditions, given by a low oxygen content in the sputter gas, result in a (1 0 1) orientation, while oxidizing conditions result in a (1 1 0) orientation. The change in orientation is accompanied by a transition from reduced to oxidized surface termination and explained by the dependence of surface energy on orientation and oxygen partial pressure given in Batzill and Diebold (2005 Prog. Surf. Sci.
79 47–154).
Ar plasma treatment on few layer graphene sheets for enhancing their field emission properties
Authors: Qi J L , Wang X , Zheng W T , Tian H W , Hu C Q , Peng Y S
Published: January 2010

Plasma treatment in Ar gas on few layer graphene sheets (FLGSs), synthesized by plasma enhanced chemical vapour deposition, has been performed for enhancing their field emission properties. The plasma etching treatment for 3 min on the FLGSs, forming an extremely sharp edge, decreases the turn-on electric field from 3.91 to 2.23 V µm−1, and increases the maximum emission current density, drawn at a field of 4.4 V µm−1, from 33 to 1330 µA cm−2. It is expected that plasma treatment provides an efficient way to improve the field emission properties of FLGSs.
Depth-resolved analysis of spontaneous phase separation in the growth of lattice-matched AlInN
Authors: Redondo-Cubero A , Lorenz K , Gago R , Franco N , di Forte Poisson M-A , Alves E , Muñoz E
Published: January 2010

We report the detection of phase separation of an Al1−x
In
x
N/GaN heterojunction grown close to lattice-matched conditions (x ∼ 0.18) by means of Rutherford backscattering spectrometry in channelling geometry and high-resolution x-ray diffraction. An initial pseudomorphic growth of the film was found, with good single crystalline quality, the nominal composition and very low strain state. After ∼50 nm, a critical thickness is reached at which the InN molar fraction of the films drops to ∼15% and at the same time the single crystalline quality of the films degrade drastically. This spontaneous effect cannot be ascribed to strain relaxation mechanisms since both techniques show a good single crystalline growth of the ternary under lattice matched conditions.
Globular Adiponectin as a Complete Mesoangioblast Regulator: Role in Proliferation, Survival, Motility, and Skeletal Muscle Differentiation
Authors: Fiaschi Tania , Tedesco Francesco Saverio , Giannoni Elisa , Diaz-Manera Jordi , Parri Matteo , Cossu Giulio , Chiarugi Paola
Published: January 2010

Mesoangioblasts are progenitor endowed with multipotent mesoderm differentiation ability. Despite the promising results obtained with mesoangioblast transplantation in muscle dystrophy, an improvement of their efficient engrafting and survival within damaged muscles, as well as their ex vivo activation/expansion and commitment toward myogenic lineage, is highly needed and should greatly increase their therapeutic potential. We show that globular adiponectin, an adipokine endowed with metabolic and differentiating functions for muscles, regulates vital cues of mesoangioblast cell biology. The adipokine drives mesoangioblasts to entry cell cycle and strongly counteracts the apoptotic process triggered by growth factor withdrawal, thereby serving as an activating and prosurvival stem cell factor. In addition, adiponectin provides a specific protection against anoikis, the apoptotic death due to lack of anchorage to extracellular matrix, suggesting a key protective role for these nonresident stem cells after systemic injection. Finally, adiponectin behaves as a chemoattractive factor toward mature myotubes and stimulates their differentiation toward the skeletal muscle lineage, serving as a positive regulator in mesoangioblast homing to injured or diseased muscles. We conclude that adiponectin exerts several advantageous effects on mesoangioblasts, potentially valuable to improve their efficacy in cell based therapies of diseased muscles.