bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetopause oscillations near the planetary period at Saturn: Occurrence, phase, and amplitude
Authors: Clarke K. E. , Andrews D. J. , Arridge C. S. , Coates A. J. , Cowley S. W. H.
Published: August 2010

Using magnetic field and plasma electron data from ∼40 Cassini orbits that crossed Saturn's magnetopause during 2004–2007, we make a first systematic study of the magnetopause oscillations that are related to the oscillations in the magnetic field and plasma inside the magnetosphere near the ∼11 h planetary rotation period, here termed the magnetospheric period. Because the motion of the spacecraft through the boundary region, combined with other boundary effects, produces a broad spread in timings between successive like crossings of the boundary, boundary oscillation events were selected for analysis using a broad timing window, 0.4–1.6 of the magnetospheric period. We find these events to be highly organized by the phase of the interior field oscillations, showing that they relate to boundary oscillations that have a closely common period. We find that ∼60% of passes through the boundary region show one or more such oscillations. Of those that do, ∼65% show one oscillation, ∼10% show two, and ∼25% show three or more. The oscillations are observed at all local times at which Cassini crossed the boundary and over a range of latitudes and are thus a global phenomenon. The phasing of the boundary oscillations is such that the rotating quasi‐uniform equatorial field within the quasi‐dipolar “core” magnetosphere (within ∼15 Saturn radii (RS) of the planet) points approximately away from the maximum outward boundary displacement. However, the boundary oscillation phase is found to depend somewhat on radial distance to the boundary, consistent with outward radial propagation in the magnetosphere at phase speeds of ∼250 km s−1. Taking account of the radial propagation, analysis shows that the phase of maximum outward boundary displacement is directly related to the phase of the density maximum in the Enceladus torus. The oscillation amplitude is estimated typically to be ∼1.2 RS but sometimes reaches ∼2–3 RS and is occasionally as great as ∼4–5 RS.
Observations of large‐amplitude, narrowband whistlers at stream interaction regions
Authors: Breneman A. , Cattell C. , Schreiner S. , Kersten K. , Wilson L. B. , Kellogg P. , Goetz K. , Jian L. K.
Published: August 2010

We present the first solar wind observations of large‐amplitude, narrowband waveforms in the frequency range 10–100 Hz, consistent with the whistler mode. These whistlers are only observable in high time resolution electric field waveform data provided by the Time Domain Sampler (TDS) instrument on STEREO. Amplitudes range from a few to >40 mV/m peak‐to‐peak, one to three orders of magnitude larger than any previous observations of whistler mode waves in the solar wind. The whistlers are obliquely propagating with a large electrostatic component and are right‐hand elliptically polarized in the spacecraft frame. The whistlers occur in groups that are strongly correlated with stream interaction regions (SIRs). The groups persist from a few seconds to minutes and are observed at 88% of SIRs and 17% of shocks from available data. A more detailed look shows that the whistler groups are observed near sudden disturbances of the solar wind magnetic field and plasma. We suggest that, owing to the oblique and narrowband nature of these waves, an electron or ion beam instability may be responsible for their creation. Test particle simulations show that the waves can interact strongly with halo (>60 eV) electrons. Test electrons were scattered by tens of degrees and energized/deenergized by up to 50% in a few tens of milliseconds. Thus these whistlers may play an important role in the dynamics of solar wind electrons within SIRs and near some shocks.
Odin/OSIRIS observations of stratospheric BrO: Retrieval methodology, climatology, and inferred Bry
Authors: McLinden C. A. , Haley C. S. , Lloyd N. D. , Hendrick F. , Rozanov A. , Sinnhuber B.‐M. , Goutail F. , Degenstein D. A. , Llewellyn E. J. , Sioris C. E. , Van Roozendael M. , Pommereau J. P. , Lotz W. , Burrows J. P.
Published: August 2010

A 7+ year (2001–2008) data set of stratospheric BrO profiles measured by the Optical Spectrograph and Infra‐Red Imager System (OSIRIS) instrument, a UV‐visible spectrometer measuring limb‐scattered sunlight from the Odin satellite, is presented. Zonal mean radiance spectra are computed for each day and inverted to yield effective daily zonal mean BrO profiles from 16 to 36 km. A detailed description of the retrieval methodology and error analysis is presented. Single‐profile precision and effective resolution are found to be about 30% and 3–5 km, respectively, throughout much of the retrieval range. Individual profile and monthly mean comparisons with ground‐based, balloon, and satellite instruments are found to agree to about 30%. A BrO climatology is presented, and its morphology and correlation with NO2 is consistent with our current understanding of bromine chemistry. Monthly mean Bry maps are derived. Two methods of calculating total Bry in the stratosphere are used and suggest (21.0 ± 5.0) pptv with a contribution from very short lived substances of (5.0 ± 5.0) pptv, consistent with other recent estimates.
Annual methane uptake by typical semiarid steppe in Inner Mongolia
Authors: Chen Weiwei , Wolf Benjamin , Yao Zhisheng , Brüggemann Nicolas , Butterbach‐Bahl Klaus , Liu Chunyan , Han Shenghui , Han Xingguo , Zheng Xunhua
Published: August 2010

Steppe ecosystems cover approximately 10% of the global land surface. Recent measurements have shown that steppe soils function as a significant sink for atmospheric methane (CH4). However, precise quantification of the annual CH4 uptake by steppe is challenged by infrequent measurements of exchange rates, which often only cover the growing season. In order to understand the annual dynamics and magnitude of CH4 exchange, especially contribution of nongrowing season to the cumulative annual CH4 exchange, we conducted year‐round CH4 flux measurements at high temporal resolution at two adjacent steppe sites. One was ungrazed and fenced since 1999 (UG99) and the other was grazed during the winter (WG01). The measurements were supplemented with observations of CH4 concentrations in the soil profile. Sites were located in typical Leymus chinensis steppe in Inner Mongolia, China. The results show that the typical semiarid steppe functioned exclusively as a sink for atmospheric CH4 throughout the entire year. Even during the spring soil thawing, a period with high water content in the top soil, CH4 uptake was dominant. The seasonality of CH4 uptake displayed a strong dependency on the seasonal variation in soil temperature. Soil moisture increased in importance when temperature was not the limiting factor. For example, CH4 rates decreased sharply following summer rainfall events. The annual CH4 uptake by the ungrazed UG99 and the winter‐grazed WG01 sites was 3.7 and 2.1 kg C ha−1, respectively. The contribution of the nongrowing season (October–April) to the cumulative annual CH4 uptake was approximately 30% (25%–36%). Additionally, our data suggest that winter grazing significantly alters the capacity of steppe soils for CH4 uptake. However, more measurements at paired ungrazed/grazed sites are needed to assess how grazing might affect the CH4 uptake capacity of steppe soils at a larger regional or global scale.
Spatial variations of crustal characteristics beneath the Hoggar swell, Algeria, revealed by systematic analyses of receiver functions from a single seismic station
Authors: Liu Kelly H. , Gao Stephen S.
Published: August 2010

The Hoggar swell in Algeria is one of the significant massifs of northwest Africa. The paucity of high‐resolution geophysical studies of the crust and mantle beneath the massifs is mostly responsible for the heated debates about the depth of the source region of the Cenozoic volcanism and the closely related uncertainty about the mechanism that formed and maintains the high elevation of the swells. Here we report results from a systematic study of 1386 high‐quality receiver functions (RFs) recorded by station TAM, the only permanent broadband seismic station on the Hoggar swell. The resulting crustal thickness is about 34 km and the Vp/Vs is 1.77 when all the RFs from the station are stacked. Our study reveals a sharp contrast in the amplitude of the P‐to‐S converted phases between the volcanic, highly‐fractured Tefedest terrane and the non‐volcanic, less fractured Laouni terrane. The former has a stacking amplitude that is comparable to typical cratonic areas, and the latter has an amplitude that is only about 25% as large. Spatially consistent crustal thickness and an intermediate‐mafic crust are inferred on the Tefedest terrane, while spatially variable crustal thickness and a felsic crust is inferred beneath the Laouni terrane. The observations can be best explained by a mantle‐derived underplated magmatic layer beneath the mechanically‐stronger Laouni terrane, and magmatic diking and resultant volcanism associated with the mechanically weaker Tefedest crust. The study demonstrated the significance of a long‐running station in the investigation of spatial variations of crustal characteristics.
Glucose promotion of GABA metabolism contributes to the stimulation of insulin secretion in β-cells
Authors: Pizarro-Delgado Javier , Braun Matthias , Hernández-Fisac Inés , Martín-Del-Río Rafael , Tamarit-Rodriguez Jorge
Published: August 2010

We have demonstrated recently that branched-chain α-keto acid stimulation of insulin secretion is dependent on islet GABA (γ-aminobutyric acid) metabolism: GABA transamination to succinic semialdehyde is increased by 2-oxoglutarate, generated in α-keto acid transamination to its corresponding α-amino acid. The present work was aimed at investigating whether glucose also promotes islet GABA metabolism and whether the latter contributes to the stimulation of insulin secretion. Glucose (20 mM) decreased both the content and release of islet GABA. Gabaculine (1 mM), a GABA transaminase inhibitor, partially suppressed the secretory response of rat perifused islets to 20 mM glucose at different L-glutamine concentrations (0, 1 and 10 mM), as well as the glucose-induced decrease in islet GABA. The drug also reduced islet ATP content and the ATP/ADP ratio at 20 mM glucose. Exogenous succinic semialdehyde induced a dose-dependent increase in islet GABA content by reversal of GABA transamination and a biphasic insulin secretion in the absence of glucose. It depolarized isolated β-cells and triggered action potential firing, accompanied by a reduction of membrane currents through ATP-sensitive K+ channels. The gene expression and enzyme activity of GABA transaminase were severalfold higher than that of 2-oxoglutarate dehydrogenase in islet homogenates. We conclude that, at high glucose concentrations, there is an increased diversion of glucose metabolism from the citric acid cycle into the ‘GABA shunt’. Semialdehyde succinic acid is a cell-permeant ‘GABA-shunt’ metabolite that increases ATP and the ATP/ADP ratio, depolarizes β-cells and stimulates insulin secretion. In summary, an increased islet GABA metabolism may trigger insulin secretion.
A New Economic Framework for Tourism Decision Making
Authors: Bailey Eric , Richardson Robert
Published: August 2010

In this article it is argued that the conventional approach of conducting either a micro- or macro-economic analysis in tourism is incongruent with emerging concerns of the modern tourism system which require economic analysis that explicitly considers community as a unit of analysis. This article thus proposes an ecological economics framework for analyzing economic decision making in tourism. This approach assumes that tourism brings costs and benefits to a society with differential effects. Communities are proximate to the benefits or costs of tourism, including externalities or negative impacts which are often associated with tourism growth. Extensions of micro economic models are proposed as an alternative framework for addressing dynamic decision making and tradeoffs in resource use. This is consistent with evolving trends in tourism demand for sustainable products or destinations, and provides important insights into the inherent tradeoffs that tourism stakeholders may need to make in the post modern ‘triple bottom line accounting’ tourism industry.
N
=
2
supersymmetric a=4-Korteweg–de Vries hierarchy derived via Gardner’s deformation of Kaup–Boussinesq equation
Authors: Hussin V. , Kiselev A. V. , Krutov A. O. , Wolf T.
Published: August 2010

We consider the problem of constructing Gardner’s deformations for the N=2 supersymmetric a=4-Korteweg–de Vries (SKdV) equation; such deformations yield recurrence relations between the super-Hamiltonians of the hierarchy. We prove the nonexistence of supersymmetry-invariant deformations that retract to Gardner’s formulas for the Korteweg-de Vries (KdV) with equation under the component reduction. At the same time, we propose a two-step scheme for the recursive production of the integrals of motion for the N=2, a=4-SKdV. First, we find a new Gardner’s deformation of the Kaup–Boussinesq equation, which is contained in the bosonic limit of the superhierarchy. This yields the recurrence relation between the Hamiltonians of the limit, whence we determine the bosonic super-Hamiltonians of the full N=2, a=4-SKdV hierarchy. Our method is applicable toward the solution of Gardner’s deformation problems for other supersymmetric KdV-type systems.
Fluid and drift-kinetic description of a magnetized plasma with low collisionality and slow dynamics orderings. I. Electron theory
Authors: Ramos J. J.
Published: August 2010

A closed theoretical model to describe slow, macroscopic plasma processes in a fusion-relevant collisionality regime is set forward. This formulation is a hybrid one, with fluid conservation equations for particle number, momentum and energy, and drift-kinetic closures. Intended for realistic application to the core of a high-temperature tokamak plasma, the proposed approach is unconventional in that the ion collisionality is ordered lower than in the ion banana regime of neoclassical theory. The present first part of a two-article series concerns the electron system, which is still equivalent to one based on neoclassical electron banana orderings. This system is derived such that it ensures the precise compatibility among the complementary fluid and drift-kinetic equations, and the rigorous treatment of the electric field and the Fokker–Planck–Landau collision operators. As an illustrative application, the special limit of an axisymmetric equilibrium is worked out in detail.
Nonlinear optical properties and ultrafast dynamics of three novel boradiazaindacene derivatives
Authors: Wang Yaochuan , Zhang Dakui , Zhou Hui , Ding Jinliang , Chen Qiang , Xiao Yi , Qian Shixiong
Published: August 2010

Three two-photon active boradiazaindacene derivatives named 2,6-di-(phenylacetylenyl)-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene (3a), 2,6-di-(9-ethyl-9H-carbazole-3-ethynyl)-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene (3b), and 2,6-di-(4-N,N-di-phenyl-phenylacetylenyl)-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene (3c) in tetrahydrofuran solutions were systematically investigated by using the femtosecond laser spectroscopic techniques. The two-photon absorption cross sections of 3a, 3b and 3c were determined to be 29 GM, 46 GM, and 60 GM, respectively, increasing with the increase in strength of the electron-donor groups. The relaxation dynamics of the excited states measured by femtosecond pump-probe experiments reveal a broad region of stimulated radiation of the excited states and the different relaxation process happened in these compounds. The preliminary two-photon fluorescence imaging experiment show their good cell permeability, nontoxicity, and excellent two-photon fluorescence properties.
A numerical study of geometry dependent errors in velocity, temperature, and density measurements from single grid planar retarding potential analyzers
Authors: Davidson R. L. , Earle G. D. , Klenzing J. H. , Heelis R. A.
Published: August 2010

Planar retarding potential analyzers (RPAs) have been utilized numerous times on high profile missions such as the Communications/Navigation Outage Forecast System and the Defense Meteorological Satellite Program to measure plasma composition, temperature, density, and the velocity component perpendicular to the plane of the instrument aperture. These instruments use biased grids to approximate ideal biased planes. These grids introduce perturbations in the electric potential distribution inside the instrument and when unaccounted for cause errors in the measured plasma parameters. Traditionally, the grids utilized in RPAs have been made of fine wires woven into a mesh. Previous studies on the errors caused by grids in RPAs have approximated woven grids with a truly flat grid. Using a commercial ion optics software package, errors in inferred parameters caused by both woven and flat grids are examined. A flat grid geometry shows the smallest temperature and density errors, while the double thick flat grid displays minimal errors for velocities over the temperature and velocity range used. Wire thickness along the dominant flow direction is found to be a critical design parameter in regard to errors in all three inferred plasma parameters. The results shown for each case provide valuable design guidelines for future RPA development.
Free energy calculations using dual-level Born–Oppenheimer molecular dynamics
Authors: Retegan Marius , Martins-Costa Marilia , Ruiz-López Manuel F.
Published: August 2010

We describe an efficient and accurate method to compute free energy changes in complex chemical systems that cannot be described through classical molecular dynamics simulations, examples of which are chemical and photochemical reactions in solution, enzymes, interfaces, etc. It is based on the use of dual-level Born–Oppenheimer molecular dynamics simulations. A low-level quantum mechanical method is employed to calculate the potential of mean force through the umbrella sampling technique. Then, a high-level quantum mechanical method is used to estimate a free energy correction on selected points of the reaction coordinate using perturbation theory. The precision of the results is comparable to that of ab initio molecular dynamics methods such as the Car–Parrinello approach but the computational cost is much lower, roughly by two to three orders of magnitude. The method is illustrated by discussing the association free energy of simple organometallic compounds, although the field of application is very broad.
Electrostatic height modulation of bound particle labels by buffer exchange in an evanescent wave biosensor
Authors: van Ommering Kim , Paesen Rik , van Zon Hans B. A. , Koets Marjo , van IJzendoorn Leo J. , Prins Menno W. J.
Published: August 2010

We introduce a technique to electrostatically modulate the height of bound particle labels on a biosensor surface by exchanging the buffer. In an evanescent wave biosensor, height modulation leads to a modulation of the scattered and reflected light intensity. We measured a lower scattering and, therefore, a higher reflection for a decreasing ionic strength, which can be explained by an increasing electrostatic force repelling bound particles from the surface. By comparing bonds with troponin, 105 base pair (bp) DNA and 290 bp DNA, we found that the signal change for an ensemble of bound particles was related to the length of the analyte. Additionally, we observed for individual particles that the thermal fluctuations of scattered light intensity became smaller for decreasing ionic strength and that the average intensity shifted toward lower values, corresponding to larger particle heights. A quantitative model comprising electrostatic repulsion and van der Waals interaction could fit the measured height displacements for four different DNA lengths (105 bp to 590 bp) as analytes. Height manipulation of bound particle labels thus reflects analyte-specific properties and may lead to biosensors with enhanced specificity.
Kohn’s localization in the insulating state: One-dimensional lattices, crystalline versus disordered
Authors: Bendazzoli Gian Luigi , Evangelisti Stefano , Monari Antonio , Resta Raffaele
Published: August 2010

The qualitative difference between insulators and metals stems from the nature of the low-lying excitations, but also—according to Kohn’s theory [W. Kohn, Phys. Rev. 133, A171 (1964)]—from a different organization of the electrons in their ground state: electrons are localized in insulators and delocalized in metals. We adopt a quantitative measure of such localization, by means of a “localization length” λ, finite in insulators and divergent in metals. We perform simulations over a one-dimensional binary alloy model, in a tight-binding scheme. In the ordered case the model is either a band insulator or a band metal, whereas in the disordered case it is an Anderson insulator. The results show indeed a localized/delocalized ground state in the insulating/metallic cases, as expected. More interestingly, we find a significant difference between the two insulating cases: band versus Anderson. The insulating behavior is due to two very different scattering mechanisms; we show that the corresponding values of λ differ by a large factor for the same alloy composition. We also investigate the organization of the electrons in the many body ground state from the viewpoint of the density matrices and of Boys’ theory of localization.
Quantum Monte Carlo ground state energies for the singly charged ions from Li through Ar
Authors: Maldonado P. , Sarsa A. , Buendía E. , Gálvez F. J.
Published: August 2010

Nonrelativistic frozen nucleus all-electron Quantum Monte Carlo ground state energies of positive and negative ions Li+ to Ar+ and Li− to Cl−, respectively, are reported. Explicitly correlated wave functions with a single configuration model function times a Jastrow factor are employed for all of the systems studied. The accuracy obtained for the ions in the third period is similar to that reached for the ions in the second one. For those ions with a stronger multiconfiguration nature a restricted multiconfiguration expansion has been employed. The ground state energy here obtained for the charged species shows a similar quality to that reached for neutral atoms. Starting from those results, ionization potentials and electron affinities are calculated.
Comprehensive understanding of the effect of electric dipole at high-k/SiO2 interface on the flatband voltage shift in metal-oxide-semiconductor device
Authors: Wang Xiaolei , Han Kai , Wang Wenwu , Ma Xueli , Chen Dapeng , Zhang Jing , Du Jun , Xiong Yuhua , Huang Anping
Published: August 2010

Electrical characteristics of HfO2/SiO2 interface are comprehensively studied to clarify the intrinsic origin of flatband voltage (VFB) shift in metal-oxide-semiconductor (MOS) device with high-k/metal gate structure. A methodology for quantitative extraction of the interface dipole and chargers at high-k/SiO2 interface is proposed. The dipole and charges at HfO2/SiO2 interface are extracted to be about −0.38 V and −1.15×1013 cm−2, respectively. This result shows that the high density of negative charges at HfO2/SiO2 interface rather than the interface dipole are the dominant cause of the positive VFB shift in the MOS device with HfO2/SiO2 stack.
Homogeneous linewidth of the intraband transition at 1.55 μm in GaN/AlN quantum dots
Authors: Nguyen D. T. , Wüster W. , Roussignol Ph. , Voisin C. , Cassabois G. , Tchernycheva M. , Julien F. H. , Guillot F. , Monroy E.
Published: August 2010

We present homogeneous line width measurements of the intraband transition at 1.55 μm in GaN/AlN quantum dots by means of nonlinear spectral hole-burning experiments. The square-root dependence of the differential transmission signal with the incident pump power reveals the importance of electron-electron scattering in the population relaxation dynamics. We find on the contrary that this scattering process plays a minor role in the coherence relaxation dynamics since the homogeneous linewidth of 15 meV at 5 K does not depend on the incident pump power. This suggests the predominance of other dephasing mechanisms such as spectral diffusion, and temperature-dependent measurements support this hypothesis.
Kinetics of photoinduced surface patterning in chalcogenide thin films
Authors: Kaganovskii Yu. , Beke D. L. , Kökényesi S.
Published: August 2010

The kinetics of photoinduced variations in surface profile in chalcogenide glass films under illumination is described. It is demonstrated that the competition between the stress-induced atomic flux (toward irradiated regions of the film) and the diffusion flux induced by an increase in the bulk energy due to broken bonds (and directed from irradiated to dark regions) can result in either a positive or negative net mass transfer in the irradiated region. Depending on the light intensity, one can obtain either formation of bumps or depressions in the illuminated regions.
Nonspin related giant magnetoresistance ≤600% in hybrid field-effect transistors with ferromagnetic gates
Authors: Lin T.-Y. , Lim K.-M. , Andrews A. M. , Strasser G. , Bird J. P.
Published: August 2010

We demonstrate a nonspin related giant magnetoresistance (600% at 1.6 K) in a hybrid field-effect transistor (FET) with a ferromagnetic gate. The robust response of this “Mag-FET” is obtained by using a gate that induces strong fringing magnetic fields (FMFs) in the FET channel. The large magnetoresistance results from the ability of the FMFs to modulate the electrostatic barrier to transport, induced in the channel by the gate potential. These results suggest a viable strategy to achieve Mag-FET operation at room temperature, and as such could open up approaches to magnetoelectronics.
Model Linear Low Density Polyethylenes from the ROMP of 5-Hexylcyclooct-1-ene
Authors: Kobayashi Shingo , Macosko Christopher W. , Hillmyer Marc A.
Published: August 2010

Model hexyl-branched linear low density polyethylene (C8-LLDPE) samples were synthesized by the ring-opening metathesis copolymerization (ROMP) of the 5-hexylcyclooct-1-ene (1) and cyclooctadiene (COD), followed by catalytic hydrogenation. The ROMP of 1 and copolymerization of 1 and COD using the Grubbs second generation catalyst (G2) afford polymers with the number of hexyl branches based on the feed composition. The resulting hexyl-branched polymers, poly(1) and poly(1-stat-COD), were completely converted into model C8-LLDPE samples by catalytic hydrogenation. The C8-LLDPE samples exhibit the expected reduction in density on branching content. The melting temperature (Tm), crystallization temperature (Tc), and heat of fusion/crystallization (ΔHm/ΔHc) of these materials were studied by differential scanning calorimetry.
Synthesis of Photoreactive Block Copolymers Based on 1-Iminopyridinium Ylides
Authors: Theato Patrick , Klinger Daniel
Published: August 2010

Two photoreactive pyridinium ylide containing monomers, {[2-(metacryloyloxy)ethoxy]carbonyl}(pyridinium-1-yl)azanide (M1) and pyridinium-1-yl-(4-vinylbenzoyl)azanide (M2), were synthesized. Both monomers were polymerized under controlled radical polymerization conditions, i.e. reversible addition–fragmentation chain transfer polymerization (M1 and M2) and nitroxide-mediated polymerization (M2). Further block copolymers PMMA-b-PM1 and PS-b-PM2 were successfully synthesized and their molecular weight, Mn, and block ratio could be determined by 1H NMR analysis, thereby opening the synthetic possibilities of photoreactive ylides in block copolymer syntheses.
Solubility and Thermoresponsiveness of PMMA in Alcohol-Water Solvent Mixtures
Authors: Hoogenboom Richard , Becer C. Remzi , Guerrero-Sanchez Carlos , Hoeppener Stephanie , Schubert Ulrich S.
Published: August 2010

To reduce the environmental burden of polymer processing, the use of non-toxic solvents is desirable. In this regard, the improved solubility of poly(methyl methacrylate) (PMMA) in ethanol/water solvent mixtures is very appealing. In this contribution, detailed investigations on the solubility of PMMA in alcohol/water solvent mixtures are reported based on turbidimetry measurements. PMMA revealed upper critical solution temperature transitions in pure ethanol and ethanol/water mixtures. However, around 80 wt-% ethanol content a solubility maximum was observed for PMMA as indicated by a decrease in the transition temperature. Moreover, the transition temperatures increased with increasing PMMA molar mass as well as increasing polymer concentration. Careful analysis of both heating and cooling turbidity curves revealed a peculiar hysteresis behaviour with a higher precipitation temperature compared with dissolution with less than 60 wt-% or more than 90 wt-% ethanol in water and a reverse hysteresis behaviour at intermediate ethanol fractions. Finally, the transfer of poly(styrene)-block-poly(methyl methacrylate) block copolymer micelles from the optimal solvent, i.e. aqueous 80 wt-% ethanol, to almost pure water and ethanol is demonstrated.
A RAFT Analogue Olefin Polymerization Technique Using Coordination Chemistry
Authors: D'Agosto Franck , Boisson Christophe
Published: August 2010

The present paper highlights analogies between one of the most efficient control radical polymerization techniques namely the reversible addition–fragmentation chain transfer process, and the catalyzed polyethylene chain growth, the only technique that can controlled olefins polymerization through coordination chemistry under catalytic conditions.
Synthesis of Self-assembling Cyclic Peptide-polymer Conjugates using Click Chemistry
Authors: Chapman Robert , Jolliffe Katrina A. , Perrier Sébastien
Published: August 2010

Self-assembling cyclic peptide-polymer conjugates were prepared by ‘clicking’ polymers (prepared by RAFT polymerization) to an azide functionalized d-alt-l cyclic octapeptide via the Huisgen 1,3-dipolar cycloaddition reaction. Due to the high graft density, the efficiency of the click chemistry conjugation reaction was found to be highly dependent on the size of the polymer. At relatively low molecular weights, as many as four polymer chains could be grafted to each 8 residue cyclic peptide ring. Evidence for the self assembly of the conjugates into peptide-polymer nanotubes was observed by TEM and IR.
Thiol-Based 'Click' Chemistries in Polymer: Synthesis and Modification
Authors: Lowe Andrew B. , Harvison M. Alyse
Published: August 2010

A series of thiol-based ‘click’ reactions is discussed with an emphasis on highlighting the individual chemistries and noting recent literature examples. This is not an exhaustive review but rather serves to demonstrate the versatility and clear potential of thiol-based chemistry in polymer/materials design, synthesis, and modification.
Everything Under the Sun: The 11th Pacific Polymer Conference
Authors: Whittaker Andrew K.
Published: August 2010

The 11th Pacific Polymer Conference brought together experts in all fields of polymer science. In this issue some of the recent advances presented at the meeting are highlighted.
Effects of gamete source and culture conditions on the competence of in vitro-produced embryos for post-transfer survival in cattle
Authors: Hansen Peter J. , Block Jeremy , Loureiro Barbara , Bonilla Luciano , Hendricks Katherine E. M.
Published: August 2010

One limitation to the use of in vitro-produced embryos in cattle production systems is the fact that pregnancy rates after transfer to recipients are typically lower than when embryos produced in vivo are transferred. Conceptually, the oocyte and spermatozoon from which the embryo is derived could affect competence for post-transfer survival. There are sire differences in embryonic survival after transfer, but there is little evidence that an embryo’s ability to establish pregnancy is determined by sex sorting of spermatozoa by flow cytometry. The role of the source of the oocyte as a determinant of embryonic survival after transfer has not been examined carefully. Conditions for embryo culture after fertilisation can have an impact on the ability of the embryo to establish pregnancy following transfer. Among the specific molecules produced in the reproductive tract of the cow that have been shown to improve competence of in vitro-produced embryos for post-transfer survival are colony-stimulating factor 2, insulin-like growth factor-1 (for recipients exposed to heat stress) and hyaluronan (for less-advanced embryos). There is also a report that embryo competence for post-transfer survival can be improved by inclusion of a carbon-activated air filtration system in the incubator used to culture embryos. Progress in developing culture systems to improve embryonic competence for survival after transfer would be hastened by the development of in vitro assays that accurately predict the potential of an embryo to establish pregnancy after transfer. A group of 52 genes has been identified that are differentially expressed in embryos that developed to term v. embryos that did not establish pregnancy. Perhaps a gene microarray consisting of these genes, alone or in combination with other genes, could be used to screen embryos for competence to establish pregnancy.
Brief introduction to whole-genome selection in cattle using single nucleotide polymorphisms
Authors: Seidel G. E.
Published: August 2010

Genomic selection using single nucleotide polymorphisms (SNPs) is a powerful new tool for genetic selection. In cattle, SNP profiles for individual animals are generated using a small plastic chip that is diagnostic for up to 50 000 SNPs spaced throughout the genome. Phenotypes, usually averaged over offspring of bulls, are matched with SNP profiles of bulls mathematically so that animals can be ranked for siring desirable phenotypes via their SNP profiles. For many traits in dairy cattle, the rate of genetic improvement can be nearly doubled when SNP information is used in addition to current methods of genetic evaluation. Separate SNP analyses need to be developed for different populations (e.g. the system for Holsteins is not useful for Jerseys). In addition, the value of these systems is very dependent on the number of accurate phenotypes matched with SNP profiles; for example, increasing the number of North American Holstein bulls evaluated from 1151 to 3576 quadrupled the additional genetic gain in net merit from this approach. Thus, the available information will be insufficient to exploit this technology fully for most populations. However, once a valid SNP evaluation system is developed, any animal in that population, including embryos, can be evaluated with similar accuracy. Biopsying embryos and screening them via SNP analysis will greatly enhance the value of this technology by minimising generation intervals.
Use of equine chorionic gonadotrophin in synchronised AI of seasonal-breeding, pasture-based, anoestrous dairy cattle
Authors: Bryan M. A. , Bó G. A. , Heuer C. , Emslie F. R.
Published: August 2010

In seasonally calving dairy areas, a critical index of efficiency and profitability is the ability to maintain a short annual calving spread. In essence, this means that all cows need to conceive within 90 days of calving. Anovulatory anoestrus (AA) is a major barrier to reproductive performance under these conditions and the successful treatment of AA is an important aspect of reproductive intervention. The present paper reviews regimens used to treat AA in New Zealand and reports on a large-scale field trial investigating the effects of equine chorionic gonadotrophin (eCG) within a proven efficacious treatment protocol. The administration of eCG at the time of removal of a progesterone-releasing device in an 8-day, oestradiol benzoate (EB)-based treatment protocol increased the percentage of cows in calf after 7 and 28 days of breeding. The interaction between cow age and treatment with eCG was significant, with cows over 5 years of age having higher conception rates (P = 0.002) and 7 day in-calf rates (P = 0.002) than cows on a standard 8-day treatment protocol without eCG. The addition of eCG to a standard 8-day EB/progesterone protocol can improve reproductive success in seasonally calving AA dairy cows.
12 QUANTIFICATION OF REACTIVE OXYGEN SPECIES IN BOVINE SEMEN WITH DIFFERENT SEMINAL QUALITY AND WITH EXTENDER CONTAINING ANTIOXIDANT EVALUATED BY ARTIFICIAL INSEMINATION
Authors: Borges J. C. , Silva M. R. , Tedesco A. C. , Costa D. S. , Esper C. R. , Franceschini P. H.
Published: August 2010

The aim this study was to evaluate the effects on artificial insemination (AI) of minimizing oxidative stress by adding an antioxidant into the sperm microenvironment. For that purpose, semen of bulls with different seminal quality was evaluated in nature and after addition of extender with and without antioxidant, followed by freezing and thawing, with respect to thiobarbituric acid reactive substances (TBARS) concentration, total antioxidant capacity (TAC), and AI success. TBARS is an indicator of lipid peroxidation and TAC measures free radicals. Twelve ejaculates from 5 bulls were treated with Tris egg yolk extender (CE) and in half of each ejaculate the extender was supplemented with 200 μL of Trolox (AE). Three of these 5 bulls had high-quality semen (mean 11.9 ± 5.9 total defect, 7.7 ± 3.1 major defect, and 4.2 ± 3.9 minor defect) and 2 animals had poor-quality sperm (mean 31.9 ± 9.7 total defect, 26.3 ± 8.5 major defect, and 5.6 ± 5.0 minor defect) (P < 0.05). For AI, 300 Nelore heifers were divided in 10 groups and the females in each group were inseminated with semen of the same bull and extender treatment. To evaluate oxidative damage, TBARS concentration was measured to indirectly determine malondialdehyde (lipid-peroxidation metabolite) concentration, whereas TAC was measured using myoglobin, as a source of radicals, which interact with a chromogen 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS), whose cation radical is spectroscopically detectable. The latency phase (lag) in the accumulation of ABTS cation is proportional to the antioxidant concentration. The pregnancy rates 60 days after AI were analyzed by chi-square test, and data of free radical production were evaluated by ANOVA, followed by the Tukey test with significance level of 5%. Reactive oxygen species (ROS) production in nature semen (0.351 nmol of TBARS in 50 × 108 spermatozoa) was lower (P < 0.05) when compared to diluted semen (0.367 nmol of TBARS in 50 × 108 spermatozoa). No difference (P > 0.05) between extenders was observed after thawing. The bulls with poor-quality semen presented total ROS production (0.967) superior (P < 0.05) to that of bulls with good-quality semen (0.753). Although the use of antioxidant in the extender did not decrease ROS and TAC production (P > 0.05), pregnancy rates after AI in bulls with poor quality semen with AE (60.0%) was superior (P < 0.06) to that in bulls with high-quality sperm with AE (56.6%). In conclusion, bulls with poor-quality semen present higher ROS and TAC production, and the use of antioxidant in the extender for cryopreservation with poor-quality bovine semen, in spite of not decreasing ROS and TAC production, improves pregnancy rates.

Financial support: FAPESP.
123 BOVINE OOCYTE VITRIFICATION USING THE CRYOTOP METHOD: EFFECT OF CUMULUS CELLS AND VITRIFICATION PROTOCOL ON SURVIVAL AND SUBSEQUENT DEVELOPMENT
Authors: Zhou X. L. , Al Naib A. , Sun D. W. , Lonergan P.
Published: August 2010

The ability to successfully cryopreserve mammalian oocytes has numerous practical and economic ethical benefits that may positively affect animal breeding programs and assisted conception in humans. However, oocyte survival and development following cryopreservation remain poor. The aim of the present study was (1) to evaluate the effect of the presence of cumulus cells on the outcome of vitrification of immature (GV) or mature (MII) oocytes, (2) to compare empirical and theoretical vitrification protocol, and (3) to assess the effect of adding ice blockers to vitrification media on survival and development competence of bovine oocytes following vitrification using the Cryotop method. Bovine oocytes were collected from the ovaries of slaughtered cross-bred beef heifers. In Experiment 1, cumulus-enclosed and partially denuded GV and MII oocytes were vitrified in 15% EG + 15% DMSO + 0.5 M sucrose in 2 steps. In Experiment 2, GV oocytes were vitrified as above or using theoretical modelling based on permeability and osmotic tolerance characteristics (Wang et al. Reprod. Fertil. Dev. 21 141) in 30% EG +11.4% trehalose in 3 steps or 40% EG + 11.4% trehalose in 4 steps. In Experiment 3, GV oocytes were vitrified in media supplemented or not with 1 of 2 ice blockers (21st Century Medicine, Fontana, CA, USA) 1% X-1000, 1% Z-1000, or both in 3 steps. The survival, cleavage, and blastocyst rate of cumulus-enclosed oocytes was significantly higher (ANOVA) than those of partially denuded oocytes when vitrified at GV (93.8% v. 81.3%, 65.8% v. 47.3%, 11.3% v. 4.0%, respectively, P < 0.05). However, no significant effect of cumulus cover was detected between the two groups when vitrified at MII (93.0% v. 91.8%, 35.2% v. 36.8%, 5.0% v. 4.4%, respectively). Furthermore, cumulus-enclosed oocytes vitrified at the GV stage exhibited a significantly higher development competence than those vitrified at MII (P < 0.05). In Experiment 2, there were no significant differences in the survival, cleavage, and blastocyst rates among 3 protocols (86.0% v. 92.8% v. 91.2%, 44.8% v. 54.4% v. 45.6%, 5.0% v. 5.4% v. 4.0%, respectively). However, cleavage and blastocyst rate were significantly lower (P < 0.05) than nonvitrified control oocytes. In Experiment 3, the presence of ice-blockers did not improve rate or blastocyst development (P < 0.05). In conclusion, cumulus-enclosed GV bovine oocytes survived vitrification and subsequently developed at higher rates than MII oocytes. Theoretical analysis of permeability characteristics and tolerance limits alone may not be sufficient to improve vitrification protocols.
127 REGULATION OF H3K27me3 AND H3K4me3 DURING INITIAL PORCINE EMBRYONIC DEVELOPMENT
Authors: Gao Y. , Hall V. , Hyttel P.
Published: August 2010

During mammalian development, gene expression is partly regulated by posttranslational modifications of histones. In particular, H3K27me3 and H3K4me3 are involved in transcriptional repression and activation, respectively. In this study, we examined the global levels of H3K27me3 and H3K4me3, as well as the expression levels of their specific methylases and demethylases during porcine pre-implantation embryonic development. Global histone methylation was analyzed by immunocytochemical quantification within in vivo porcine embryos at 1-cell (Day 1), 4-cell (Day 3), morula (Day 5), and late blastocyst (containing the epiblast; Day 9). The numbers of embryos analyzed for H3K27me3 at the 1-cell, 4-cell, morula, and late blastocyst stage were 7, 8, 6, and 5, respectively, and for H3K4me3 at these four stages were 7, 6, 6, and 5, respectively. At the same developmental stages, mRNA expression of methylases (EZH2, EED, and SUZ12, three core components of PRC2) and demethylases (JMJD3 and UTX) of H3K27me3 was performed on pooled embryos (n = 10), as well as expression of methylases (MLL1 and ASH1L) and demethylase (RBP2) of H3K4me3, by comparative RT-PCR. Expression was compared with pooled embryos from the limb bud stage (Day 21). GAPDH was used as the reference gene, and expression was normalized to Day 21 embryos. Our results show that the levels of global histone methylation of H3K27me3 and H3K4me3 decrease gradually from 1-cell to morula, but both were increased in late blastocysts. The levels of H3K27me3 methylase (EZH2, EED, and SUZ12) transcripts increased from 1-cell to late blastocyst stage. Low expression of the H3K27me3 demethylase JMJD3 was found at 1-cell stage and high expression at the 4-cell stage from when it decreased gradually to the late blastocyst. UTX expression was low but peaked at the 4-cell stage. Expression of H3K4me3 methylase MLL1, was low, whereas ASH1L expression was high at the 4-cell stage. RBP2, a demethylase of H3K4me3, was highly expressed at the late blastocyst stage. In conclusion, at the major genome activation (the 4-cell stage), H3K27me3 and H3K4me3 have decreased to moderate levels, which apparently balance each other with respect to gene repression and activation allowing for genome activation. At the 4-cell stage the activation of H3K4me3 is favored as a consequence of low levels of H3K27 methylases and high levels of H3K27 demethylases combined with high levels of H3K4 methylases and low levels of H3K4 demethylases. Interestingly, at the late blastocyst stage of development, high expression of H3K27me3 methylases and the H3K4me3 demethylase, RBP2, are observed, indicating repression of gene expression, which is counterintuitive to accelerating development. We speculate other factors, such as microRNA or other kinds of epigenetic mechanisms, might play a critical role at this developmental stage. Thus, further research is required to explain these phenomena occurred during early porcine development.
154 THE EFFECT OF OXYGEN TENSION ON IN VITRO DEVELOPMENT OF BOVINE EMBRYOS IN POLYDIMETHYLSILOXANE-BASED WELL OF THE WELL DISHES PREPARED UNDER ATMOSPHERIC OR REDUCED AIR PRESSURE
Authors: Somfai T. , Inaba Y. , Aikawa Y. , Ohtake M. , Kobayashi S. , Akai T. , Hattori H. , Sugimura S. , Konishi K. , Nagai T. , Imai K.
Published: August 2010

Polydimethylsiloxane (PDMS) is a non-toxic silicon compound. Its excellent optical characteristics and easy preparation make it a good candidate material for the molding of custom-shaped dishes for embryo culture. We investigated the feasibility of PDMS-based well of the well (WOW) dishes for in vitro culture of bovine embryos under different oxygen tensions. The WOW dishes with 25 micro-wells (each of 175 μm depth and 250 μm width in diameter arranged in 5 columns and 5 rows) were molded from PDMS prepared either under atmospheric (Experiment 1) or reduced (0.1 MPa) (Experiment 2) air pressure to remove air bubbles. Presumptive zygotes obtained by the in vitro maturation and fertilization of follicular oocytes were placed and cultured for 7 days in traditional micro-drops of culture medium (Control) or in the micro-wells of PDMS-based WOW dishes (PDMS-WOW), both covered by paraffin oil. The culture medium was CR1aa supplemented with 5% calf serum. The culture drop size was 125 μL (5 μL/oocyte) in both groups. Embryo development and blastocyst cell numbers between Control and PDMS-WOW groups were compared either under 20% or 5% O2 tensions. There was no statistical difference in cleavage and blastocyst rates (ranging between 82.3-86.4% and 34.0-45.8%, respectively) between Control and PDMS-WOW embryos irrespective of oxygen tension and dish production method. In Experiment 1, the mean total cell numbers in blastocysts were lower in the PDMS-WOW group than that in Control under 20% O2 (105.0 ± 5.5 and 130.4 ± 9.9, respectively) (P < 0.05, ANOVA); however, the application of 5% O2 significantly improved the cell numbers and eliminated the difference between the PDMS-WOW and Control groups (135.4 ± 6.2 and 148.0 ± 9.0, respectively). In Experiment 2, there was no significant difference in mean total cell numbers in blastocysts between the PDMS-WOW and Control either under 20% O2 (97.2 ± 5.7 and 103.9 ± 8.9, respectively) or 5% O2 (147.5 ± 12.1 and 157.3 ± 3.9, respectively). The numbers and rates of inner cell mass and trophectoderm cells did not differ between the Control and PDMS-WOW groups, irrespective of O2 tension and production method. Our results demonstrate that bovine embryos can develop to the blastocyst stage in PDMS-based WOW dishes; however, it may express detrimental effects on embryonic cell numbers, which can be neutralized by the application of low O2 tension during culture or reduced air pressure during the PDMS preparation.

This work was supported by the Research and Development Program for New Bio-Industry Initiatives.