bluuebunny/crossref_metadata_2025 huggingface dataset:
Shallow shelf approximation as a “sliding law” in a thermomechanically coupled ice sheet model
Authors: Bueler Ed , Brown Jed
Published: July 2009

The shallow shelf approximation, a balance of membrane stresses for ice flow, is an effective “sliding law” for ice sheet modeling. Our use of it as a sliding law becomes a standard model for ice stream flow when the sliding velocity is large (100 m a−1 and faster). Following Schoof (2006a), we describe the basal resistance as plastic till for which the yield stress is given by a Mohr‐Coulomb formula. Pore water pressure is related to basal melt rate. The velocity field used in the mass continuity and conservation of energy equations is an average of velocities from the shallow shelf approximation and the nonsliding shallow ice approximation. Using this scheme, our model has realistic, time‐dependent ice streams which exhibit the range of surface velocities seen in actual ice streams. We demonstrate the model at high spatial resolution (5 km grid) over multiple millenia using its implementation in the Parallel Ice Sheet Model. Numerical experiments show that the entire scheme is stable with respect to many parameter changes. Some experiments reveal significant ice stream variability in a hypothetical steady climate, with characteristic cycles on the order of 1000 years. We believe this is the first practical whole ice sheet model with a unified treatment of vertical shear stresses and membrane stresses. It is capable of high‐resolution, thermomechanically coupled, multimillenia simulations of ice sheets containing ice streams.
Improvements to regional explosion identification using attenuation models of the lithosphere
Authors: Pasyanos Michael E. , Walter William R.
Published: July 2009

Regional P/S amplitudes have been recognized as an effective discriminant between earthquakes and explosions. While closely spaced events generally discriminate easily, the application of this technique to broad regions has been hampered by large variations in the amplitude of phases due to the attenuation of the crust and upper mantle. Making use of a recent P‐wave and S‐wave attenuation model of the lithosphere, we have found that correcting the events using our amplitude methodology significantly reduces the scattering in the earthquake population. We demonstrate an application of this technique to station NIL using broad‐area earthquakes and the 1998 Indian nuclear explosion using the Pn/Lg discriminant in the 1–2 Hz passband. We find that the explosion, which is lost in the scatter of the earthquakes in the uncorrected discriminant, clearly separates by correcting for attenuation structure. We see a similar reduction in scatter and separation for the Pn/Sn and Pg/Lg discriminants.
The Io UV footprint: Location, inter‐spot distances and tail vertical extent
Authors: Bonfond B. , Grodent D. , Gérard J.‐C. , Radioti A. , Dols V. , Delamere P. A. , Clarke J. T.
Published: July 2009

The Io footprint (IFP) consists of one or several spots observed in both jovian hemispheres and is related to the electromagnetic interaction between Io and the magnetosphere. These spots are followed by an auroral curtain, called the tail, extending more than 90° longitude in the direction of planetary rotation. We use recent Hubble Space Telescope images of Jupiter to analyze the location of the footprint spots and tail as a function of Io's location in the jovian magnetic field. We present here a new IFP reference contour—the locus of all possible IFP positions—with an unprecedented accuracy, especially in previously poorly covered sectors. We also demonstrate that the lead angle ‐ the longitudinal shift between Io and the actual IFP position ‐ is not a reliable quantity for validation of the interaction models. Instead, the evolution of the inter‐spot distances appears to be a better diagnosis of the Io‐Jupiter interaction. Moreover, we present observations of the tail vertical profiles as seen above the limb. The emission peak altitude is ∼900 km and remains relatively constant with the distance from the main spot. The altitudinal extent of the vertical emission profiles is not compatible with precipitation of a mono‐energetic electron population. The best fit is obtained for a kappa distribution with a characteristic energy of ∼70 eV and a spectral index of 2.3. The broadness of the inferred electron energy spectrum gives insight into the physics of the electron acceleration mechanism at play above the IFP tail.
Observations of drifter dispersion in the surfzone: The effect of sheared alongshore currents
Authors: Spydell Matthew S. , Feddersen Falk , Guza R. T.
Published: July 2009

Surfzone dispersion is characterized with single‐particle Lagrangian statistics of GPS‐tracked drifters deployed on 5 days at Huntington Beach, California. Incident wave heights varied weakly between days, and stationary rip currents did not occur. Generally, the time‐dependent bulk surfzone cross‐shore diffusivity xx was similar on all days, reaching a local maxima of approximately 1.5 m2 s−1 between 160 and 310 s, before decreasing to about 1 m2 s−1 at 1000 s. The alongshore diffusivity increased monotonically to 1000 s and was variable between the 5 days. For times greater than 30 s, the alongshore diffusivity is greater than the cross‐shore diffusivity, consistent with previous observations. The observed diffusivities are fit to analytic functional forms, from which asymptotic diffusivities and Lagrangian timescales are determined. The asymptotic alongshore diffusivity varies between 4 and 19 m2 s−1, and this variation is related to the variation in the maximum of the mean alongshore current m, broadly consistent with a shear dispersion scaling ∼ . Cross‐shore variation in dispersion processes, lumped together in the bulk κ, is apparent in the non‐Gaussian probability distribution function of drifter displacements at intermediate times (30 s). Both biased and unbiased diffusivity sampling errors depend on the number and length of drifter trajectories and limit aspects of the analysis.
Chemical characterization of water‐soluble organic carbon aerosols at a rural site in the Pearl River Delta, China, in the summer of 2006
Authors: Miyazaki Y. , Kondo Y. , Shiraiwa M. , Takegawa N. , Miyakawa T. , Han S. , Kita K. , Hu M. , Deng Z. Q. , Zhao Y. , Sugimoto N. , Blake D. R. , Weber R. J.
Published: July 2009

Online measurements of water‐soluble organic carbon (WSOC) aerosols were made using a particle‐into‐liquid sampler (PILS) combined with a total organic carbon (TOC) analyzer at a rural site in the Pearl River Delta region, China, in July 2006. A macroporous nonionic (DAX‐8) resin was used to quantify hydrophilic and hydrophobic WSOC, which are defined as the fractions of WSOC that penetrated through and retained on the DAX‐8 column, respectively. Laboratory calibrations showed that hydrophilic WSOC (WSOCHPI) included low‐molecular aliphatic dicarboxylic acids and carbonyls, saccharides, and amines, while hydrophobic WSOC (WSOCHPO) included longer‐chain aliphatic dicarboxylic acids and carbonyls, aromatic acids, phenols, organic nitrates, cyclic acids, and fulvic acids. On average, total WSOC (TWSOC) accounted for 60% of OC, and WSOCHPO accounted for 60% of TWSOC. Both WSOCHPI and WSOCHPO increased with photochemical aging determined from the NOx/NOy ratio. In particular, the average WSOCHPO mass was found to increase by a factor of five within a timescale of ∼10 hours, which was substantially larger than that of WSOCHPI (by a factor of 2–3). The total increase in OC mass with photochemical aging was associated with the large increase in WSOCHPO mass. These results, combined with the laboratory calibrations, suggest that significant amounts of hydrophobic organic compounds (likely containing large carbon numbers) were produced by photochemical processing. By contrast, water‐insoluble OC (WIOC) mass did not exhibit significant changes with photochemical aging, suggesting that chemical transformation of WIOC to WSOC was not a dominant process for the production of WSOC during the study period.
21 Tesla MRI Microscopy of Mice Kidney, Heart and Skin: Quantitation of MRI Visible Features
Authors: Sharma S , Sharma Rakesh
Published: July 2009

Excised mice kidney, heart and skin MRI visible features were quantitated using ex vivo 21 Tesla MRI microimager. The fast MRI acquisition protocols of FLASH, gradient echo flow compensated (GEFC) techniques were used to visualize microvasculature of mice kidney, mice heart including cardiac arteries, veins, cordate tendons and mice skin epidermis with hair follicle features.
Regulation and function of selenoproteins in human disease
Authors: Bellinger Frederick P. , Raman Arjun V. , Reeves Mariclair A. , Berry Marla J.
Published: July 2009

Selenoproteins are proteins containing selenium in the form of the 21st amino acid, selenocysteine. Members of this protein family have many diverse functions, but their synthesis is dependent on a common set of cofactors and on dietary selenium. Although the functions of many selenoproteins are unknown, several disorders involving changes in selenoprotein structure, activity or expression have been reported. Selenium deficiency and mutations or polymorphisms in selenoprotein genes and synthesis cofactors are implicated in a variety of diseases, including muscle and cardiovascular disorders, immune dysfunction, cancer, neurological disorders and endocrine function. Members of this unusual family of proteins have roles in a variety of cell processes and diseases.
Josephson squelch filter for quantum nanocircuits
Authors: Forn-Díaz P. , Schouten R. N. , den Braver W. A. , Mooij J. E. , Harmans C. J. P. M.
Published: July 2009

We fabricated and tested a squelch circuit consisting of a copper powder filter with an embedded Josephson junction connected to ground. For small signals (squelch ON), the small junction inductance attenuates strongly from dc to at least 1 GHz, while for higher frequencies dissipation in the copper powder increases the attenuation exponentially with frequency. For large signals (squelch OFF), the circuit behaves as a regular metal powder filter. The measured ON/OFF ratio is larger than 50 dB up to 50 MHz. This squelch can be applied in low temperature measurement and control circuitry for quantum nanostructures, such as superconducting qubits and quantum dots.
Multiphoton autofluorescence spectral analysis for fungus imaging and identification
Authors: Lin Sung-Jan , Tan Hsin-Yuan , Kuo Chien-Jui , Wu Ruei-Jr , Wang Shiou-Han , Chen Wei-Liang , Jee Shiou-Hwa , Dong Chen-Yuan
Published: July 2009

We performed multiphoton imaging on fungi of medical significance. Fungal hyphae and spores of Aspergillus flavus, Micosporum gypseum, Micosoprum canis, Trichophyton rubrum, and Trichophyton tonsurans were found to be strongly autofluorescent but generate less prominent second harmonic signal. The cell wall and septum of fungal hyphae can be easily identified by autofluorescence imaging. We found that fungi of various species have distinct autofluorescence characteristics. Our result shows that the combination of multiphoton imaging and spectral analysis can be used to visualize and identify fungal species. This approach may be developed into an effective diagnostic tool for fungal identification.
Observation of a fifth-order optical nonlinearity in Bi0.9La0.1Fe0.98Mg0.02O3 ferroelectric thin films
Authors: Gu Bing , Wang Yang , Ji Wei , Wang John
Published: July 2009

Ferroelectric Bi0.9La0.1Fe0.98Mg0.02O3 thin films with high optical quantity were deposited on quartz substrates by radio frequency magnetron sputtering at 650 °C. The interplay between third- and fifth-order optical nonlinearities is observed by performing Z-scans under femtosecond laser excitation with 1.60 eV photon energy. The measured third-order nonlinearities mainly originate from electronic Kerr effect and two-photon absorption (2PA), while the population redistribution assisted by 2PA leading to an equivalent stepwise χ(3):χ(1) process is the main mechanism of the fifth-order effect.
Influence of Coulomb collisions on the structure of reconnection layers
Authors: Daughton W. , Roytershteyn V. , Albright B. J. , Karimabadi H. , Yin L. , Bowers Kevin J.
Published: July 2009

The influence of Coulomb collisions on the structure of reconnection layers is examined in neutral sheet geometry using fully kinetic simulations with a Monte Carlo treatment of the Fokker–Planck operator. The algorithm is first carefully benchmarked against key predictions from transport theory, including the parallel and perpendicular resistivities as well as the thermal force. The results demonstrate that the collisionality is accurately specified, thus allowing the initial Lundquist number to be chosen as desired. For modest Lundquist numbers S≲1000, the classic Sweet–Parker solution is recovered. Furthermore, a distinct transition to a faster kinetic regime is observed when the thickness of the resistive layer δSP falls below the ion inertial length di. For higher Lundquist numbers S≳1000, plasmoids (secondary islands) are observed within the elongated resistive layers. These plasmoids give rise to a measurable increase in the reconnection rate and for certain cases induce a transition to kinetic regimes sooner than expected from the δSP≈di condition. During this transition, the reconnection electric field exceeds the runaway limit, leading to electron scale current layers in which the nonideal electric field is supported predominantly by off-diagonal components in the electron pressure tensor, along with a residual contribution from electron-ion momentum exchange. These weakly collisional electron layers are also unstable to the formation of new plasmoids.
A new lattice density functional theory for polymer adsorption at solid-liquid interface
Authors: Chen Xueqian , Sun Lei , Liu Honglai , Hu Ying , Jiang Jianwen
Published: July 2009

We report a new lattice density functional theory for polymer solutions at the solid-liquid interface. The theory accounts for the nearest-neighbor interactions and the long-range correlations due to chain connectivity. A Helmholtz free-energy functional is developed with an exact free-energy functional expression for the ideal chains and a thermodynamic model of lattice polymer solutions for the excess contributions. The local and weighted density approximations are used to calculate the contributions due to the athermal entropy of mixing and the internal energy of mixing, respectively. Mayer function and propagator formalism are adopted to obtain the segment-density distributions for various conformations including adsorbed trains, tails, loops, and free polymers. The predicted density distributions of polymer adsorption are in good agreement with simulation results. The results imply that as a counterbalance between energy and conformational entropy, the weighted density approximation used in the functional can rationally capture the segment-segment correlations.
Solution-processable polymer solar cells from a poly(3-hexylthiophene)/[6,6]-phenyl C61-butyric acidmethyl ester concentration graded bilayers
Authors: Wang Dong Hwan , Lee Hang Ken , Choi Dae-Geun , Park Jong Hyeok , Park O Ok
Published: July 2009

Polymer photovoltaic (PV) device prepared with a vertical phase separation has intensified the research on the effectiveness of the concentration graded active layer. In this paper, a polymer PV device with a poly(3-hexylthiophene)/[6,6]-phenyl C61-butyric acidmethyl ester (P3HT/PCBM) bilayers active film with a concentration gradient has been fabricated via solution process. The concentration variation has been confirmed by the Auger spectroscopy. The devices showed an enhanced photocurrent density and power conversion efficiency compared to those of the bulk heterojunction PV prepared under the same fabrication condition.
Photoluminescence properties of erbium doped InGaN epilayers
Authors: Sedhain A. , Ugolini C. , Lin J. Y. , Jiang H. X. , Zavada J. M.
Published: July 2009

We report on the photoluminescence properties of erbium (Er) doped InxGa1−xNa epilayers synthesized by metal organic chemical vapor deposition. The crystalline quality and surface morphology of Er doped In0.05Ga0.95N were nearly identical to those of Er doped GaN. The photoluminescence intensity of the 1.54 μm emission in Er doped In0.05Ga0.95N was an order of magnitude lower than in Er doped GaN and decreased with the increase of the In content. The reduction in 1.54 μm emission intensity was accompanied by enhanced emission intensities of deep level impurity transition lines.
Self-organization in dissipative optical lattices
Authors: Bağci G. Baris , Tirnakli Ugur
Published: July 2009

We show that the transition from Gaussian to the q-Gaussian distributions occurring in atomic transport in dissipative optical lattices can be interpreted as self-organization by recourse to a modified version of Klimontovich’s S-theorem. As a result, we find that self-organization is possible in the transition regime, only where the second moment ⟨p2⟩ is finite. Therefore, the nonadditivity parameter q is confined within the range 1<q<53, although the whole spectrum of q values, i.e., 1<q<3, is considered theoretically possible. The range of q values obtained from the modified S-theorem is also confirmed by the experiments carried out by Douglas et al. [Phys. Rev. Lett. 96, 110601 (2006)].
Structural analysis of substrate binding by the TatBC component of the twin-arginine protein transport system
Authors: Tarry Michael J. , Schäfer Eva , Chen Shuyun , Buchanan Grant , Greene Nicholas P. , Lea Susan M. , Palmer Tracy , Saibil Helen R. , Berks Ben C.
Published: July 2009

The Tat system transports folded proteins across the bacterial cytoplasmic membrane and the thylakoid membrane of plant chloroplasts. In
Escherichia coli
substrate proteins initially bind to the integral membrane TatBC complex which then recruits the protein TatA to effect translocation. Overproduction of TatBC and the substrate protein SufI in the absence of TatA led to the accumulation of TatBC-SufI complexes that could be purified using an affinity tag on the substrate. Three-dimensional structures of the TatBC-SufI complexes and unliganded TatBC were obtained by single-particle electron microscopy and random conical tilt reconstruction. Comparison of the structures shows that substrate molecules bind on the periphery of the TatBC complex and that substrate binding causes a significant reduction in diameter of the TatBC part of the complex. Although the TatBC complex contains multiple copies of the signal peptide-binding TatC protomer, purified TatBC-SufI complexes contain only 1 or 2 SufI molecules. Where 2 substrates are present in the TatBC-SufI complex, they are bound at adjacent sites. These observations imply that only certain TatC protomers within the complex interact with substrate or that there is a negative cooperativity of substrate binding. Similar TatBC-substrate complexes can be generated by an alternative in vitro reconstitution method and using a different substrate protein.
Quasiclassical trajectory study of H+SiH
4
reactions in full-dimensionality reveals atomic-level mechanisms
Authors: Cao Jianwei , Zhang Zhijun , Zhang Chunfang , Liu Kun , Wang Manhui , Bian Wensheng
Published: July 2009

This work elucidates new atomic-level mechanisms that may be common in a range of chemical reactions, and our findings are important for the understanding of the nature of polyatomic abstraction and exchange reactions. A global 12-dimensional ab initio potential energy surface (PES), which describes both H+SiH
4
abstraction and exchange reactions is constructed, based on the modified Shepard interpolation method and UCCSD(T)/cc-pVQZ energy calculations at 4,015 geometries. This PES has a classical barrier height of 5.35 kcal/mol for abstraction (our best estimate is 5.35 ± 0.15 kcal/mol from extensive ab initio calculations), and an exothermicity of −13.12 kcal/mol, in excellent agreement with experiment. Quasiclassical trajectory calculations on this new PES reveal interesting features of detailed dynamical quantities and underlying new mechanisms. Our calculated product angular distributions for exchange are in the forward hemisphere with a tail sideways, and are attributed to the combination of three mechanisms: inversion, torsion-tilt, and side-inversion. With increase of collision energy our calculated angular distributions for abstraction first peak at backward scattering and then shift toward smaller scattering angles, which is explained by a competition between rebound and stripping mechanisms; here stripping is seen at much lower energies, but is conceptually similar to what was observed in the reaction of H+CD
4
by Zare and coworkers [Camden JP, et al. (2005)
J Am Chem Soc
127:11898–11899]. Each of these atomic-level mechanisms is confirmed by direct examination of trajectories, and two of them (torsion-tilt and side-inversion) are proposed and designated in this work.
Survival of an evasive prey
Authors: Oshanin G. , Vasilyev O. , Krapivsky P. L. , Klafter J.
Published: July 2009

We study the survival of a prey that is hunted byNpredators. The predators perform independent random walks on a square lattice withVsites and start a direct chase whenever the prey appears within their sighting range. The prey is caught when a predator jumps to the site occupied by the prey. We analyze the efficacy of a lazy, minimal-effort evasion strategy according to which the prey tries to avoid encounters with the predators by making a hop only when any of the predators appears within its sighting range; otherwise the prey stays still. We show that if the sighting range of such a lazy prey is equal to 1 lattice spacing, at least 3 predators are needed in order to catch the prey on a square lattice. In this situation, we establish a simple asymptotic relation lnPev(t) ∼ (N/V)2lnPimm(t) between the survival probabilities of an evasive and an immobile prey. Hence, when the density ρ =N/Vof the predators is low, ρ ≪ 1, the lazy evasion strategy leads to the spectacular increase of the survival probability. We also argue that a short-sighting prey (its sighting range is smaller than the sighting range of the predators) undergoes an effective superdiffusive motion, as a result of its encounters with the predators, whereas a far-sighting prey performs a diffusive-type motion.
Acute stress enhances glutamatergic transmission in prefrontal cortex and facilitates working memory
Authors: Yuen Eunice Y. , Liu Wenhua , Karatsoreos Ilia N. , Feng Jian , McEwen Bruce S. , Yan Zhen
Published: July 2009

The prefrontal cortex (PFC), a key brain region controlling cognition and emotion, is strongly influenced by stress. While chronic stress often produces detrimental effects on these measures, acute stress has been shown to enhance learning and memory, predominantly through the action of corticosteroid stress hormones. We used a combination of electrophysiological, biochemical, and behavioral approaches in an effort to identify the cellular targets of acute stress. We found that behavioral stressors in vivo cause a long-lasting potentiation of NMDAR- and AMPAR-mediated synaptic currents via glucocorticoid receptors (GRs) selectively in PFC pyramidal neurons. This effect is accompanied by increased surface expression of NMDAR and AMPAR subunits in acutely stressed animals. Furthermore, behavioral tests indicate that working memory, a key function relying on recurrent excitation within networks of PFC neurons, is enhanced by acute stress via a GR-dependent mechanism. These results have identified a form of long-term potentiation of synaptic transmission induced by natural stimuli in vivo, providing a potential molecular and cellular mechanism for the beneficial effects of acute stress on cognitive processes subserved by PFC.
Hepatitis C Virus Transmission in Hemodialysis Units Importance of Infection Control Practices and Aseptic Technique
Authors: Thompson Nicola D. , Novak Ryan T. , Datta Deblina , Cotter Susanne , Arduino Matthew J. , Patel Priti R. , Williams Ian T. , Bialek Stephanie R.
Published: July 2009

We investigated 4 hepatitis C virus (HCV) infection outbreaks at hemodialysis units to identify practices associated with transmission. Apparent failures to follow recommended infection control precautions resulted in patient-to-patient HCV transmission, through cross-contamination of the environment or intravenous medication vials. Fastidious attention to aseptic technique and infection control precautions are essential to prevent HCV transmission.
Regulation of Cell Death by Recycling Endosomes and Golgi Membrane Dynamics via a Pathway Involving Src-family kinases, Cdc42 and Rab11a
Authors: Landry Marie-Claude , Sicotte Andréane , Champagne Claudia , Lavoie Josée N.
Published: July 2009

Actin dynamics and membrane trafficking influence cell commitment to programmed cell death through largely undefined mechanisms. To investigate how actin and recycling endosome (RE) trafficking can engage death signaling, we studied the death program induced by the adenovirus early region 4 open reading frame 4 (E4orf4) protein as a model. We found that in the early stages of E4orf4 expression, Src-family kinases (SFKs), Cdc42, and actin perturbed the organization of the endocytic recycling compartment and promoted the transport of REs to the Golgi apparatus, while inhibiting recycling of protein cargos to the plasma membrane. The resulting changes in Golgi membrane dynamics that relied on actin-regulated Rab11a membrane trafficking triggered scattering of Golgi membranes and contributed to the progression of cell death. A similar mobilization of RE traffic mediated by SFKs, Cdc42 and Rab11a also contributed to Golgi fragmentation and to cell death progression in response to staurosporine, in a caspase-independent manner. Collectively, these novel findings suggest that diversion of RE trafficking to the Golgi complex through a pathway involving SFKs, Cdc42, and Rab11a plays a general role in death signaling by mediating regulated changes in Golgi dynamics.
c-Cbl and Cbl-b Act Redundantly to Protect Osteoclasts from Apoptosis and to Displace HDAC6 from β-Tubulin, Stabilizing Microtubules and Podosomes
Authors: Purev Enkhtsetseg , Neff Lynn , Horne William C. , Baron Roland
Published: July 2009

c-Cbl and Cbl-b are highly conserved adaptor proteins that participate in integrin signaling, regulating cytoskeletal organization, motility, and bone resorption. Deletion of both c-Cbl and Cbl-b in mice leads to embryonic lethality, indicating that the two proteins perform essential redundant functions. To examine the redundant actions of c-Cbl and Cbl-b in osteoclasts, we depleted c-Cbl in Cbl-b−/−osteoclasts by using a short hairpin RNA. Depleting both Cbl proteins disrupted both the podosome belt and the microtubule network and decreased bone-resorbing activity. Stabilizing the microtubules with paclitaxel or inhibiting histone deacetylase 6 (HDAC6), which destabilizes microtubules by deacetylating β-tubulin, protected both the microtubule network and the podosome belt. Examination of the mechanism involved demonstrated that the conserved four-helix bundle of c-Cbl's tyrosine kinase binding domain bound to β-tubulin, and both c-Cbl and Cbl-b displaced HDAC6. In addition to the effects on microtubules and the podosome belt, depleting both Cbls significantly increased the levels of the proapoptotic protein Bim and apoptosis relative to the levels induced by eliminating either protein alone. Thus, both c-Cbl and Cbl-b promote bone resorption via the stabilization of microtubules, allowing the formation of the podosome belt in osteoclasts, and by promoting osteoclast survival.
Utilization of Western Medicine and Traditional Chinese Medicine Services by Physicians and Their Relatives: The Role of Training Background
Authors: Huang Nicole , Chou Yiing-Jenq , Chen Long-Shen , Lee Cheng-Hua , Wang Pen-Jen , Tsay Jen-Huoy
Published: July 2009

Despite extensive efforts to improve the attitude and practice of physicians with respect to complementary and alternative medicine (CAM), the role of training background on physician′s own utilization of mainstream Western medicine (WM) and CAM remains unclear. We aimed to compare personal utilizations of WM and traditional Chinese medicine (TCM) among doctors trained in WM only, TCM only or both. A retrospective population‐based study was conducted using the 2004 Taiwan′s National Health Insurance data. A total of 103 879 doctors and their relatives and 2 623 658 other adults with equivalent socioeconomic status were analyzed. Ambulatory care utilization of WM and TCM services was compared using the following three measures: probability of any use, number of visits and total annual expenditure. Doctors who were trained in Western medicine only (WMDs) had the highest WM use, followed by doctors who were trained in both (WMD‐CMDs), while Chinese medicine‐trained doctors (CMDs) had the lowest use. For TCM use, a reverse pattern was observed. Similar patterns were found among doctors′ relatives. Compared with other adults with equivalent socioeconomic status, both the CMDs and WMD‐CMDs had a greater use of TCM services. For WM, although the WMDs′ probability and frequency of usage were similar to other adults, they incurred considerably higher expenditure. The use of WM and TCM by doctors and their relatives was significantly associated with the training background of the doctors. This highlights the importance of how increasing knowledge and understanding of other medical discipline may influence a practitioner′s care‐providing behaviors.
Nutrient balance affects foraging behaviour of a trap-building predator
Authors: Mayntz David , Toft Søren , Vollrath Fritz
Published: July 2009

Predator foraging may be affected by previous prey capture, but it is unknown how nutrient balance affects foraging behaviour. Here, we use a trap-building predator to test whether nutrients from previous prey captures affect foraging behaviour. We fed orb-weaving spiders (
Zygiella x-notata
) prey flies of different nutrient composition and in different amounts during their first instar and measured the subsequent frequency of web building and aspects of web architecture. We found that both the likelihood of web building and the number of radii in the web were affected by prey nutrient composition while prey availability affected capture area and mesh height. Our results show that both the balance of nutrients in captured prey and the previous capture rate may affect future foraging behaviour of predators.
The management of fluid and wave resistances by whirligig beetles
Authors: Voise Jonathan , Casas Jérôme
Published: July 2009

Whirligig beetles (Coleoptera: Gyrinidae) are semi-aquatic insects with a morphology and propulsion system highly adapted to their life at the air–water interface. When swimming on the water surface, beetles are subject to both fluid resistance and wave resistance.

The purpose of this study was to analyse swimming speed, leg kinematics and the capillarity waves produced by whirligig beetles on the water surface in a simple environment. Whirligig beetles of the speciesGyrinus substriatuswere filmed in a large container, with a high-speed camera. Resistance forces were also estimated.

These beetles used three types of leg kinematics, differing in the sequence of leg strokes: two for swimming at low speed and one for swimming at high speed. Four main speed patterns were produced by different combinations of these types of leg kinematics, and the minimum speed for the production of surface waves (23 cm s−1) corresponded to an upper limit when beetles used low-speed leg kinematics. Each type of leg kinematics produced characteristic capillarity waves, even if the beetles moved at a speed below 23 cm s−1. Our results indicate that whirligig beetles use low- and high-speed leg kinematics to avoid maximum drag and swim at speed corresponding to low resistances.
The Invariant Set Postulate: a new geometric framework for the foundations of quantum theory and the role played by gravity
Authors: Palmer T. N.
Published: July 2009

A new law of physics is proposed, defined on the cosmological scale but with significant implications for the microscale. Motivated by nonlinear dynamical systems theory and black-hole thermodynamics, the Invariant Set Postulate proposes that cosmological states of physical reality belong to a non-computable fractal state-space geometry
I
, invariant under the action of some subordinate deterministic causal dynamics
D

I

. An exploratory analysis is made of a possible causal realistic framework for quantum physics based on key properties of
I
. For example, sparseness is used to relate generic counterfactual states to points
p
∉
I
of unreality, thus providing a geometric basis for the essential contextuality of quantum physics and the role of the abstract Hilbert Space in quantum theory. Also, self-similarity, described in a symbolic setting, provides a possible realistic perspective on the essential role of complex numbers and quaternions in quantum theory. A new interpretation is given to the standard ‘mysteries’ of quantum theory: superposition, measurement, non-locality, emergence of classicality and so on. It is proposed that heterogeneities in the fractal geometry of
I
are manifestations of the phenomenon of gravity. Since quantum theory is inherently blind to the existence of such state-space geometries, the analysis here suggests that attempts to formulate unified theories of physics within a conventional quantum-theoretic framework are misguided, and that a successful quantum theory of gravity should unify the causal non-Euclidean geometry of space–time with the atemporal fractal geometry of state space.

The task is not to make sense of the quantum axioms by heaping more structure, more definitions, more science fiction imagery on top of them, but to throw them away wholesale and start afresh. We should be relentless in asking ourselves: From what deep physical principles might we derive this exquisite structure? These principles should be crisp, they should be compelling. They should stir the soul.

Chris Fuchs (
Gilder 2008
, p. 335)
Critical strength of an electric field whereby a bubble can adopt a steady shape
Authors: Shaw S. J. , Spelt P. D. M.
Published: July 2009

The electrically induced steady-state solutions of a gas bubble in a dielectric liquid under the action of a steady electric field are considered using the leaky dielectric model. Representing the shape deformation by a sum of spherical harmonics, it is shown that for a given parameter set there exists a critical value of the ratio of the electric to surfaces stresses beyond which no steady states exist, thus implying bubble instability and possible fragmentation. Previous studies imply that bubble instability can only be achieved if either the dielectric constant or the conductivity of the gaseous contents of the bubble is large. We show that on accounting for compressibility of the bubble, no such restriction applies for bubble instability. Below these critical values, multiple steady states are found. It is shown that a more approximate model, which assumes that the bubble is a prolate ellipsoid, can be used to represent the results for weak electric fields, but cannot be used for the prediction of the critical value of the strength of the electric field beyond which no steady-state exists.
Investigation of the critical states of dielectric cracks in functionally graded piezoelectric materials
Authors: Yan Zhi , Jiang Liying
Published: July 2009

A critical state for electromechanical loads that determines when the traditional impermeable (or permeable) crack model serves as the upper or the lower bound of the dielectric crack model, first proposed for homogeneous piezoelectric materials, is studied further for functionally graded piezoelectric materials (FGPMs) in the current work. The analytical formulations of a single crack and two interacting cracks in the FGPMs are derived by using Fourier transforms, and the resulting integral equations are solved with Chebyshev polynomials. Numerical simulations are conducted to show the effect of crack length, positions of two interacting cracks and material gradient of FGPMs at this critical state. Interesting results show that the combination of the material gradient and the crack length
α
a
plays an important role in determining this critical state. Our solutions also reveal there may exist several critical states for two interacting cracks in the FGPMs.
The Late Permian herbivore
Suminia
and the early evolution of arboreality in terrestrial vertebrate ecosystems
Authors: Fröbisch Jörg , Reisz Robert R.
Published: July 2009

Vertebrates have repeatedly filled and partitioned the terrestrial ecosystem, and have been able to occupy new, previously unexplored habitats throughout their history on land. The arboreal ecospace is particularly important in vertebrate evolution because it provides new food resources and protection from large ground-dwelling predators. We investigated the skeletal anatomy of the Late Permian (approx. 260 Ma) herbivorous synapsid
Suminia getmanovi
and performed a morphometric analysis of the phalangeal proportions of a great variety of extant and extinct terrestrial and arboreal tetrapods to discern locomotor function and habitat preference in fossil taxa, with special reference to
Suminia
. The postcranial anatomy of
Suminia
provides the earliest skeletal evidence for prehensile abilities and arboreality in vertebrates, as indicated by its elongate limbs, intrinsic phalangeal proportions, a divergent first digit and potentially prehensile tail. The morphometric analysis further suggests a differentiation between grasping and clinging morphotypes among arboreal vertebrates, the former displaying elongated proximal phalanges and the latter showing an elongation of the penultimate phalanges. The fossil assemblage that includes
Suminia
demonstrates that arboreality and resource partitioning occurred shortly after the initial establishment of the modern type of terrestrial vertebrate ecosystems, with a large number of primary consumers and few top predators.
Evolution of muscle phenotype for extreme high altitude flight in the bar-headed goose
Authors: Scott Graham R. , Egginton Stuart , Richards Jeffrey G. , Milsom William K.
Published: July 2009

Bar-headed geese migrate over the Himalayas at up to 9000 m elevation, but it is unclear how they sustain the high metabolic rates needed for flight in the severe hypoxia at these altitudes. To better understand the basis for this physiological feat, we compared the flight muscle phenotype of bar-headed geese with that of low altitude birds (barnacle geese, pink-footed geese, greylag geese and mallard ducks). Bar-headed goose muscle had a higher proportion of oxidative fibres. This increased muscle aerobic capacity, because the mitochondrial volume densities of each fibre type were similar between species. However, bar-headed geese had more capillaries per muscle fibre than expected from this increase in aerobic capacity, as well as higher capillary densities and more homogeneous capillary spacing. Their mitochondria were also redistributed towards the subsarcolemma (cell membrane) and adjacent to capillaries. These alterations should improve O2diffusion capacity from the blood and reduce intracellular O2diffusion distances, respectively. The unique differences in bar-headed geese were much greater than the minor variation between low altitude species and existed without prior exercise or hypoxia exposure, and the correlation of these traits to flight altitude was independent of phylogeny. In contrast, isolated mitochondria had similar respiratory capacities, O2kinetics and phosphorylation efficiencies across species. Bar-headed geese have therefore evolved for exercise in hypoxia by enhancing the O2supply to flight muscle.
Host acceptance and sex allocation of
Nasonia
wasps in response to conspecifics and heterospecifics
Authors: Ivens A. B. F. , Shuker D. M. , Beukeboom L. W. , Pen I.
Published: July 2009

Species recognition is an important aspect of an organism's biology. Here, we consider how parasitoid wasps vary their reproductive decisions when their offspring face intra- and interspecific competition for resources and mates. We use host acceptance and sex ratio behaviour to test whether female
Nasonia vitripennis
and
Nasonia longicornis
discriminate between conspecifics and heterospecifics when ovipositing. We tested pairs of conspecific or heterospecific females ovipositing either simultaneously or sequentially on a single host, using strains varying in their recent history of sympatry. Both
N. vitripennis
and
N. longicornis
rejected parasitized hosts more often than unparasitized hosts, although females were more likely to superparasitize their own species in the sequential treatment. However, sex ratio behaviour did not vary, suggesting similar responses towards conspecifics and heterospecifics. This contrasts with theory predicting that heterospecifics should not influence sex ratios as their offspring do not influence local mate competition, where conspecifics would. These non-adaptive sex ratios reinforce the lack of adaptive kin discrimination in
N. vitripennis
and suggest a behavioural constraint. Discrimination between closely related species is therefore context dependent in
Nasonia
. We suggest that isolating mechanisms associated with the speciation process have influenced behaviour to a greater extent than selection on sex ratios.
Male mating costs in a polygynous mosquito with ornaments expressed in both sexes
Authors: South Sandra H. , Steiner Dianna , Arnqvist Göran
Published: July 2009

Male mate choice in species with conventional sex roles is difficult to explain and has, therefore, been the focus of many recent theoretical models. These models have focused on variance in female quality and, to a lesser extent, male investments/costs associated with mating. In this study, we investigate the costs of courtship and copulation in the polygynous mosquitoSabethes cyaneus. In this species, both males and females possess elaborate ornaments. Previous studies suggest that the most likely explanation for the presence of these ornaments is mutual mate choice. Thus, this system provides an excellent model for exploring the evolution of mutual mate choice in polygynous species. We disentangle the costs of courtship and copulation by monitoring male survival in three groups of males: housed alone (group 1); able only to court females (group 2); or able to court and copulate with females (group 3). We show that males incur a cost of courtship and copulation and that courtship intensity is negatively related to male longevity. Our results suggest that courtship and copulation carry additive costs to males. We discuss the implications of these results in the context of current mutual mate choice theory and suggest that courtship costs may be an unappreciated key factor in the evolution of male mate choice.
New Insights into the Mechanisms of Water-Stress-Induced Cavitation in Conifers
Authors: Cochard Hervé , Hölttä Teemu , Herbette Stéphane , Delzon Sylvain , Mencuccini Maurizio
Published: July 2009

Cavitation resistance is a key parameter to understand tree drought tolerance but little is known about the mechanisms of air entry into xylem conduits. For conifers three mechanisms have been proposed: (1) a rupture of pit margo microfibrils, (2) a displacement of the pit torus from its normal sealing position over the pit aperture, and (3) a rupture of an air-water menisci in a pore of the pit margo. In this article, we report experimental results on three coniferous species suggesting additional mechanisms. First, when xylem segments were injected with a fluid at a pressure sufficient to aspirate pit tori and well above the pressure for cavitation induction we failed to detect the increase in sample conductance that should have been caused by torus displacement from blocking the pit aperture or by membrane rupture. Second, by injecting xylem samples with different surfactant solutions, we found a linear relation between sample vulnerability to cavitation and fluid surface tension. This suggests that cavitation in conifers could also be provoked by the capillary failure of an air-water meniscus in coherence with the prediction of Young-Laplace's equation. Within the bordered pit membrane, the exact position of this capillary seeding is unknown. The possible Achilles' heel could be the seal between tori and pit walls or holes in the torus. The mechanism of water-stress-induced cavitation in conifers could then be relatively similar to the one currently proposed for angiosperms.
TILLING in Lotus japonicus Identified Large Allelic Series for Symbiosis Genes and Revealed a Bias in Functionally Defective Ethyl Methanesulfonate Alleles toward Glycine Replacements
Authors: Perry Jillian , Brachmann Andreas , Welham Tracey , Binder Andreas , Charpentier Myriam , Groth Martin , Haage Kristina , Markmann Katharina , Wang Trevor L. , Parniske Martin
Published: July 2009

We have established tools for forward and reverse genetic analysis of the legume Lotus (Lotus japonicus). A structured population of M2 progeny of 4,904 ethyl methanesulfonate-mutagenized M1 embryos is available for single nucleotide polymorphism mutation detection, using a TILLING (for Targeting Induced Local Lesions IN Genomes) protocol. Scanning subsets of this population, we identified a mutation load of one per 502 kb of amplified fragment. Moreover, we observed a 1:10 ratio between homozygous and heterozygous mutations in the M2 progeny. This reveals a clear difference in germline genetics between Lotus and Arabidopsis (Arabidopsis thaliana). In addition, we assembled M2 siblings with obvious phenotypes in overall development, starch accumulation, or nitrogen-fixing root nodule symbiosis in three thematic subpopulations. By screening the nodulation-defective population of M2 individuals for mutations in a set of 12 genes known to be essential for nodule development, we identified large allelic series for each gene, generating a unique data set that combines genotypic and phenotypic information facilitating structure-function studies. This analysis revealed a significant bias for replacements of glycine (Gly) residues in functionally defective alleles, which may be explained by the exceptional structural features of Gly. Gly allows the peptide chain to adopt conformations that are no longer possible after amino acid replacement. This previously unrecognized vulnerability of proteins at Gly residues could be used for the improvement of algorithms that are designed to predict the deleterious nature of single nucleotide polymorphism mutations. Our results demonstrate the power, as well as the limitations, of ethyl methanesulfonate mutagenesis for forward and reverse genetic studies. (Original mutant phenotypes can be accessed at http://data.jic.bbsrc.ac.uk/cgi-bin/lotusjaponicus Access to the Lotus TILLING facility can be obtained through http://www.lotusjaponicus.org or http://revgenuk.jic.ac.uk)