bluuebunny/crossref_metadata_2025 huggingface dataset:
THz Observations of the Cool Neutral Medium
Authors: Dickey John M.
Published: January 2013

The astrophysical drivers for far-infrared spectroscopy of the Galactic interstellar medium using a 15m class telescope on Dome A are compelling. For the diffuse, atomic phase, the most important lines in the far-IR spectrum are OIat 63μm and CIIat 158μm. These are the dominant cooling lines of the cool, neutral medium, and they show rich spectral structure in Herschel observations at low latitudes. But theory predicts that they should both be highly sub-thermal in excitation, so that the level populations are not in equilibrium with the kinetic temperature of the gas. A large single dish telescope or an interferometer may be able to study the absorption and emission to determine the optical depth and column density of atoms and the physical conditions in the emission regions. Comparison of Herschel CIIspectra with 21-cm absorption spectra indicates that a significant fraction of the 158μm flux may be coming from the atomic rather than the molecular phase.
The Balloon-borne Large Aperture Submillimetre Telescope (BLAST) and BLASTPol
Authors: Pascale Enzo ,   for the BLAST and BLASTPol collaboration
Published: January 2013

Balloon observations from Antarctica have proven an effective and efficient way to address open Cosmological questions as well as problems in Galactic astronomy. The Balloon-borne Large Aperture Submillimetre Telescope (BLAST) is a sub-orbital mapping experiment which uses 270 bolometric detectors to image the sky in three wavebands centred at 250, 350 and 500 μm with a 1.8 m telescope. In the years before Herschel launched, BLAST provided data of unprecedented angular and spectral coverage in frequency bands close to the peak of dust emission in star forming regions in our Galaxy, and in galaxies at cosmological distances. More recently, BLASTPol was obtained by reconfiguring the BLAST focal plane as a submillimetric polarimeter to study the role that Galactic magnetic fields have in regulating the processes of star-formation. The first and successful BLASTPol flight from Antarctica in 2010 is followed by a second flight, currently scheduled for the end of 2012.
The US Long Duration Balloon Facility at McMurdo Station
Authors: Jones W. Vernon
Published: January 2013

A sea change in scientific ballooning occurred with the inauguration of 8–20-day flights around Antarctica in the early 1990's. The attainment of 28–31-day flights and 35–42-day flights, respectively, in two and three circumnavigations of the continent has greatly increased the expectations of scientific users. There is a scientific need for the capability to provide similar-duration flights for investigations that cannot be done in the Polar Regions. A new super-pressure balloon is currently under development for future flights of 60–100 days at any latitude. This first new balloon in more than half a century would meet this need and allow the focus to change from increasing the durations of flights over and around Antarctica to ultra-long-duration flights from Antarctica.
The French-Italian Concordia Station
Authors: Mekarnia Djamel , Frenot Yves
Published: January 2013

Concordia is a French-Italian permanent station located at Dome C, Antarctica. The station provides accommodation for up to 16 people over winter and more than 70 scientists and technicians during the austral summer. The scientific projects implemented at Concordia are strictly dependent on the characteristics of the site: a) the presence of a 3 300 m thick ice cap that allows access to the planet's climate archives and the reconstruction of glacial-interglacial cycles over more than 800 000 years; b) a particularly stable pure and dry atmosphere ideal for astronomy observations and for research on the chemical composition of the atmosphere; c) a distant location from coastal perturbations favourable to magnetic and seismological observatories to complement a poor world data network in the southern hemisphere; and d) a small totally isolated group of people confined to the station over a long winter, offering an opportunity for a range of medical and psychological studies useful to prepare long duration deep space missions.

We will address the main characteristics of this station and its interest for science.
Sub-mm VLBI from the Arctic—Imaging Black Holes
Authors: Inoue Makoto ,   the Greenland Telescope team
Published: January 2013

We are deploying a new station for sub-millimeter Very Long Baseline Interferometry (VLBI) to obtain shadow images of Supermassive Black Hole (SMBH). Sub-mm VLBI is thought to be the only way so far to get the direct image of SMBH by its shadow, thanks to the superb angular resolution and high transparency against dense plasma around SMBH. At the Summit Station on Greenland, we have started monitoring the opacity at sub-mm region. The Summit Station subtends long baselines with the Atacama Large Milimeter/submillimeter Array (ALMA) in Chile and Submillimeter Array (SMA) in Hawaii. In parallel, we started retrofitting the ALMA North America prototype telescope (renamed as Greenland Telescope: GLT) for the cold environment.
ASTEP South: a first photometric analysis
Authors: Crouzet N. , Guillot T. , Mékarnia D. , Szulágyi J. , Abe L. , Agabi A. , Fanteï-Caujolle Y. , Gonçalves I. , Barbieri M. , Schmider F.-X. , Rivet J.-P. , Bondoux E. , Challita Z. , Pouzenc C. , Fressin F. , Valbousquet F. , Blazit A. , Bonhomme S. , Daban J.-B. , Gouvret C. , Bayliss D. , Zhou G. ,   the ASTEP team
Published: January 2013

The ASTEP project aims at detecting and characterizing transiting planets from Dome C, Antarctica, and qualifying this site for photometry in the visible. The first phase of the project, ASTEP South, is a fixed 10 cm diameter instrument pointing continuously towards the celestial South Pole. Observations were made almost continuously during 4 winters, from 2008 to 2011. The point-to-point RMS of 1-day photometric lightcurves can be explained by a combination of expected statistical noises, dominated by the photon noise up to magnitude 14. This RMS is large, from 2.5 mmag at R = 8 to 6% at R = 14, because of the small size of ASTEP South and the short exposure time (30 s). Statistical noises should be considerably reduced using the large amount of collected data. A 9.9-day period eclipsing binary is detected, with a magnitude R = 9.85. The 2-season lightcurve folded in phase and binned into 1,000 points has a RMS of 1.09 mmag, for an expected photon noise of 0.29 mmag. The use of the 4 seasons of data with a better detrending algorithm should yield a sub-millimagnitude precision for this folded lightcurve. Radial velocity follow-up observations reveal a F-M binary system. The detection of this 9.9-day period system with a small instrument such as ASTEP South and the precision of the folded lightcurve show the quality of Dome C for continuous photometric observations, and its potential for the detection of planets with orbital periods longer than those usually detected from the ground.
A European vision for a “Polar Large Telescope” project
Authors: Abe Lyu , Epchtein Nicolas , Ansorge Wolfgang , Argentini Stefania , Bryson Ian , Carbillet Marcel , Dalton Gavin , David Christine , Esau Igor , Genthon Christophe , Langlois Maud , Le Bertre Thibault , Lemrani Rachid , Le Roux Brice , Marchiori Gianpietro , Mékarnia Djamel , Montnacher Joachim , Moretto Gil , Prugniel Philippe , Rivet Jean-Pierre , Ruch Eric , Tao Charling , Tilquin André , Vauglin Isabelle
Published: January 2013

The Polar Large Telescope (PLT) project is primarily aimed at undertaking large, wide band synoptic astronomical surveys in the infrared in order to provide critical data to the forthcoming generation of observational facilities such as ALMA, JWST, LSST and the E–ELT, and to complement the observations obtained with them. Sensitive thermal IR surveys beyond 2.3 μm cannot be carried out from any existing ground based observatory and the Antarctic Plateau is the only place on the ground where it can be envisaged, thanks to its unique atmospheric and environmental properties, such as the turbulence profile (image quality), the low opacity and the reduced thermal background emission of the sky. These unique conditions enable high angular resolution wide field surveys in the near thermal infrared (2.3–5 μm). This spectral range is particularly well suited to tackling key astrophysical questions such as: i) investigating the nature of the distant universe, the first generation of stars and the latest stages of stellar evolution, ii) understanding transient phenomena such as gamma ray-bursts and Type Ia supernovae, iii) increasing our knowledge of extra-solar planets. Further instruments may broaden the expected science outcomes of such a 2–4 m class telescope especially for the characterization of galaxies at very large distance to provide new clues in the mysteries of dark matter and energy. Efforts will be made to merge this project with other comparable projects within an international consortium.
Airglow and Aurorae from Dome A, Antarctica
Authors: Sims Geoff , Ashley Michael C. B. , Cui Xiangqun , Everett Jon R. , Feng LongLong , Gong Xuefei , Hengst Shane , Hu Zhongwen , Lawrence Jon S. , Luong-Van Daniel M. , Moore Anna M. , Riddle Reed , Shang Zhaohui , Storey John W. V. , Tothill Nick , Travouillon Tony , Wang Lifan , Yang Huigen , Yang Ji , Zhou Xu , Zhu Zhenxi
Published: January 2013

Despite the absence of artificial light pollution at Antarctic plateau sites such as Dome A, other factors such as airglow, aurorae and extended periods of twilight have the potential to adversely affect optical observations. We present a statistical analysis of the airglow and aurorae at Dome A using spectroscopic data from Nigel, an optical/near-IR spectrometer operating in the 300–850 nm range. The median auroral contribution to the B, V and R photometric bands is found to be 22.9, 23.4 and 23.0 mag arcsec−2 respectively. We are also able to quantify the amount of annual dark time available as a function of wavelength; on average twilight ends when the Sun reaches a zenith distance of 102.6°.
Shape measurement by using basis functions
Authors: Li Guoliang , Xin Bo , Cui Wei
Published: January 2013

Gravitational lensing is one of most promising tools to probe dark energy and dark matter in our Universe. Lensing by larger-scale structures distorts the shape of background galaxies. For ground-based observations the shape is further distorted by atmospheric turbulence and optical distortions. Many algorithms were proposed to measure the shear signal but the systematic biases are still too large to be acceptable for the larger-sky surveys in the future. I will present our new algorithms for PSF reconstruction and shape measurements based on several sets of basis functions.
Secular variation and fluctuation of GPS Total Electron Content over Antarctica
Authors: Jin Rui , Jin Shuanggen
Published: January 2013

The total electron content (TEC) is an important parameters in the Earth's ionosphere, related to various space weather and solar activities. However, understanding of the complex ionospheric environments is still a challenge due to the lack of direct observations, particularly in the polar areas, e.g., Antarctica. Now the Global Positioning System (GPS) can be used to retrieve total electron content (TEC) from dual-frequency observations. The continuous GPS observations in Antarctica provide a good opportunity to investigate ionospheric climatology. In this paper, the long-term variations and fluctuations of TEC over Antarctica are investigated from CODE global ionospheric maps (GIM) with a resolution of 2.5°×5° every two hours since 1998. The analysis shows significant seasonal and secular variations in the GPS TEC. Furthermore, the effects of TEC fluctuations are discussed.
Atmospheric calibration for submillimeter and terahertz observations
Authors: Guan Xin , Stutzki Jürgen , Okada Yoko
Published: January 2013

Submillimeter observations through the atmosphere can be affected by the complex spectroscopic features of the air. Calibration of astronomical observations in these frequencies requires proper modelling of the atmosphere. We analyzed sky observations from altitudes around 500 and 200 hPa respectively and found deficiencies in atmospheric models. Further research to improve the models are expected to help in future submillimeter observations.
Induction of Hyperhomocysteinemia Models Vascular Dementia by Induction of Cerebral Microhemorrhages and Neuroinflammation
Authors: Sudduth Tiffany L , Powell David K , Smith Charles D , Greenstein Abigail , Wilcock Donna M
Published: January 2013

Vascular dementia (VaD) is the second leading cause of dementia behind Alzheimer's disease (AD) and is a frequent comorbidity with AD, estimated to occur in as many as 40% of AD patients. The causes of VaD are varied and include chronic cerebral hypoperfusion, microhemorrhages, hemorrhagic infarcts, or ischemic infarcts. We have developed a model of VaD by inducing hyperhomocysteinemia (HHcy) in wild-type mice. By placing wild-type mice on a diet deficient in folate, B6, and B12 and supplemented with excess methionine, we induced a moderate HHcy (plasma level homocysteine 82.93 ± 3.561 μmol). After 11 weeks on the diet, the hyperhomocysteinemic mice showed a spatial memory deficit as assessed by the 2-day radial-arm water maze. Also, magnetic resonance imaging and subsequent histology revealed significant microhemorrhage occurrence. We found neuroinflammation induced in the hyperhomocysteinemic mice as determined by elevated interleukin (IL)-1β, tumor necrosis factor (TNF)α, and IL-6 in brain tissue. Finally, we found increased expression and increased activity of the matrix metalloproteinase 2 (MMP2) and MMP9 systems that are heavily implicated in the pathogenesis of cerebral hemorrhage. Overall, we have developed a dietary model of VaD that will be valuable for studying the pathophysiology of VaD and also for studying the comorbidity of VaD with other dementias and other neurodegenerative disorders.
Deviation of Zipf's and Heaps' Laws in Human Languages with Limited Dictionary Sizes
Authors: Lü Linyuan , Zhang Zi-Ke , Zhou Tao
Published: January 2013

Zipf's law on word frequency and Heaps' law on the growth of distinct words are observed in Indo-European language family, but it does not hold for languages like Chinese, Japanese and Korean. These languages consist of characters and are of very limited dictionary sizes. Extensive experiments show that: (i) The character frequency distribution follows a power law with exponent close to one, at which the corresponding Zipf's exponent diverges. Indeed, the character frequency decays exponentially in the Zipf's plot. (ii) The number of distinct characters grows with the text length in three stages: It grows linearly in the beginning, then turns to a logarithmical form and eventually saturates. A theoretical model for writing process is proposed, which embodies the rich-get-richer mechanism and the effects of limited dictionary size. Experiments, simulations and analytical solutions agree well with each other. This work refines the understanding about Zipf's and Heaps' laws in human language systems.
Zc3h12c inhibits vascular inflammation by repressing NF-κB activation and pro-inflammatory gene expression in endothelial cells
Authors: Liu Ling , Zhou Zhou , Huang Shengping , Guo Yanhong , Fan Yanbo , Zhang Ji , Zhang Jifeng , Fu Mingui , Chen Y. Eugene
Published: January 2013

Endothelial activation characterized by the expression of multiple chemokines and adhesive molecules is a critical initial step of vascular inflammation, which results in recruitment of leucocytes into the sub-endothelial layer of the vascular wall and triggers vascular inflammatory diseases such as atherosclerosis. Although inhibiting endothelial inflammation has already been well recognized as a therapeutic strategy in vascular inflammatory diseases, the therapeutic targets are still elusive. In the present study we found that Zc3h12c (zinc finger CCCH-type-containing 12C), a recently discovered CCCH zinc finger-containing protein, significantly inhibited the endothelial cell inflammatory response in vitro. Overexpression of Zc3h12c significantly attenuated TNFα (tumour necrosis factor α)-induced expression of chemokines and adhesive molecules, and thus reduced monocyte adherence to HUVECs (human umbilical vein endothelial cells). Conversely, siRNA (small interfering RNA)-mediated knockdown of Zc3h12c increased the TNFα-induced expression of chemokines and adhesive molecules in HUVECs. Furthermore, forced expression of Zc3h12c decreased TNFα-induced IKKα/β [IκB (inhibitor of nuclear factor κB) kinase α/β], IκBα phosphorylation and p65 nuclear translocation, suggesting that Zc3h12c exerted its anti-inflammatory function probably by suppressing the NF-κB (nuclear factor κB) pathway. Thus Zc3h12c is an endogenous inhibitor of TNFα-induced inflammatory signalling in HUVECs and might be a therapeutic target in vascular inflammatory diseases.
Instability of vortex pair leapfrogging
Authors: Tophøj Laust , Aref Hassan
Published: January 2013

Leapfrogging is a periodic solution of the four-vortex problem with two positive and two negative point vortices all of the same absolute circulation arranged as co-axial vortex pairs. The set of co-axial motions can be parameterized by the ratio 0 < α < 1 of vortex pair sizes at the time when one pair passes through the other. Leapfrogging occurs for α > σ2, where \documentclass[12pt]{minimal}\begin{document}$\sigma = \sqrt{2}-1$\end{document}σ=2−1 is the silver ratio. The motion is known in full analytical detail since the 1877 thesis of Gröbli and a well known 1894 paper by Love. Acheson [“Instability of vortex leapfrogging,” Eur. J. Phys. 21, 269–273 (2000)]10.1088/0143-0807/21/3/310 determined by numerical experiments that leapfrogging is linearly unstable for σ2 < α < 0.382, but apparently stable for larger α. Here we derive a linear system of equations governing small perturbations of the leapfrogging motion. We show that symmetry-breaking perturbations are essentially governed by a 2D linear system with time-periodic coefficients and perform a Floquet analysis. We find transition from linearly unstable to stable leapfrogging at α = ϕ2 ≈ 0.381966, where \documentclass[12pt]{minimal}\begin{document}$\phi = \frac{1}{2}(\sqrt{5}-1)$\end{document}ϕ=12(5−1) is the golden ratio. Acheson also suggested that there was a sharp transition between a “disintegration” instability mode, where two pairs fly off to infinity, and a “walkabout” mode, where the vortices depart from leapfrogging but still remain within a finite distance of one another. We show numerically that this transition is more gradual, a result that we relate to earlier investigations of chaotic scattering of vortex pairs [L. Tophøj and H. Aref, “Chaotic scattering of two identical point vortex pairs revisited,” Phys. Fluids 20, 093605 (2008)]10.1063/1.2974830. Both leapfrogging and “walkabout” motions can appear as intermediate states in chaotic scattering at the same values of linear impulse and energy.
On the asymptotic state of high Reynolds number, smooth-wall turbulent flows
Authors: Pullin D. I. , Inoue M. , Saito N.
Published: January 2013

It is argued that the extrapolation of the log-wake law for the mean turbulent velocity profile to arbitrarily large Reynolds numbers, and also the similarity scaling for the intensity of stream-wise turbulent velocity fluctuations indicated by recent experimental measurements, are consistent with the hypothesis that smooth-wall turbulence is asymptotically transitory in the sense that these fluctuations almost everywhere decay with respect to the outer velocity scale when 1/log (Reτ) ≪ 1, where Reτ is the Reynolds number based on the skin-friction velocity uτ. The existence of one or more near-wall maxima in these turbulent velocity fluctuations whose value may grow with Reτ, does not invalidate the main scaling arguments. At gigantic Reτ, this paradigm suggests that nonlinear motions and “turbulent” energy production are still present immediately adjacent to the wall, but that their amplitude becomes vanishingly small compared to the outer velocity scale.
Molecular dynamics based chemistry models of hypervelocity collisions of O(3P) + SO2(X, 1A1) in DSMC
Authors: Parsons Neal , Levin Deborah A. , van Duin Adri C. T.
Published: January 2013

A significant process in the formation of the unique atmosphere of Io, a Jovian moon, is collision-induced dissociation of sulfur dioxide. The direct simulation Monte Carlo method (DSMC) is used to model the rarefied gas dynamics of the Ionian atmosphere. However, there is a lack of reliable reaction and collision cross sections needed for hypervelocity conditions. In this work, collisions between SO2 and O were studied using molecular dynamics/quasi-classical trajectories methods with the potential of Murrell and a force field for reactive systems (ReaxFF). Dissociation to SO was found to be the significant reacting process, but at higher collision energies, complete atomization of SO2 was found to frequently occur. In contrast, dissociation to O2 was found to be mostly negligible and formation of SO3 occurred only at low impact velocities. The chemistry and collision models developed from the Murrell and ReaxFF methods were implemented in DSMC simulations and compared to the baseline DSMC collision and reaction models. It was found that the selection of both the dissociation reaction cross section and the non-reactive collision model has a significant effect on the counterflow, shock gas dynamic structure.
A velocity map imaging photoelectron spectrometer for the study of ultrafine aerosols with a table-top VUV laser and Na-doping for particle sizing applied to dimethyl ether condensation
Authors: Yoder Bruce L. , West Adam H. C. , Schläppi Bernhard , Chasovskikh Egor , Signorell Ruth
Published: January 2013

We present a new experimental configuration for the study of size-dependent, angle-resolved photoelectron and photoion spectra of weakly bound ultrafine aerosol particles targeted at particle sizes below ∼20 nm. It combines single photon ionization by a tunable, table-top vacuum ultraviolet laser at energies up to 18 eV with velocity map imaging detection and independent size determination of the aerosol particles using the Na-doping method. As an example, the size-dependence of the valence photoelectron spectrum of dimethyl ether clusters and ultrafine aerosols is investigated. Up to a mean particle diameter of ∼3–4 nm, the first ionization energy (value at band maximum) decreases systematically (up to ∼1 eV) and the corresponding band broadens systematically (up to a factor of ∼3) with increasing aggregate size. Plateau values for band positions and bandwidths are reached beyond a diameter of ∼3–4 nm. Experimental evidence for the dominance of the fast intermolecular proton transfer over monomer fragmentation reactions upon ionization is presented via photoion imaging.
Impedance spectroscopy on ceramic materials at high temperatures, considering stray fields and electromagnetic noise
Authors: Müller T. M. , Meinhardt J. , Raether F.
Published: January 2013

Impedance spectroscopy of many ceramics is a challenge due to their high electrical resistance. Small disturbances can significantly alter the measuring results. In the present paper, it is shown how impedance measurements can be performed in an electromagnetically noisy ac furnace, using consequent Faraday shielding of the sample and the electrical connections. As example, the conductivity data of alumina was measured between room temperature and 1000 °C and compared to literature data. In addition, a correction method for the calculation of permittivity was developed to consider the stray fields in the sample-electrode setup. The distribution of the electrical field was simulated by finite element (FE) methods for different sample geometries and electrode arrangements. The deviations from the behavior of an ideal plate capacitor follow a linear trend and are in the order of 5% to 20% for an experimentally reasonable range of sample thicknesses. To check the theoretical results experimentally, alumina samples of varying thickness were measured. The customary calculation of permittivity leads to a clear trend with sample thickness, whereas the correction from the FE-simulation produces almost constant values of the relative permittivity.
Enhanced upper critical field, critical current density, and thermal activation energy in new ytterbium doped CeFeAsO0.9F0.1 superconductor
Authors: Kanagaraj M. , Thakur Gohil S. , Prakash Jai , Kalai Selvan G. , Arumugam S. , Ganguli Ashok K.
Published: January 2013

In this report, we have investigated the essential physical properties of Ce0.7Yb0.3FeAsO0.9F0.1 superconductor such as field dependent critical current density (Jc), thermal activation energy (U0), and upper critical field (Hc2). From the isothermal magnetization curves and size of the superconducting grains, the critical current density Jc of 2.3 × 106 A/cm2 at 2 K, 0.5 T was estimated using the Bean's model for this Yb doped superconductor. A gradual decrease of Jc and absence of peak effect were found on increasing magnetic field up to 5 T. Thermal activation energy (U0/kB = ∼2500 K) calculated from Arrhenius plots at low magnetic field (0.5 T) indicates a strong flux pinning potential might be co-existing with applied magnetic field. Our results suggest that this new Yb doped superconductor is a possible practical high temperature superconductor under certain magnetic field and temperature.
Multifunctional bulk plasma source based on discharge with electron injection
Authors: Klimov A. S. , Medovnik A. V. , Tyunkov A. V. , Savkin K. P. , Shandrikov M. V. , Vizir A. V.
Published: January 2013

A bulk plasma source, based on a high-current dc glow discharge with electron injection, is described. Electron injection and some special design features of the plasma arc emitter provide a plasma source with very long periods between maintenance down-times and a long overall lifetime. The source uses a sectioned sputter-electrode array with six individual sputter targets, each of which can be independently biased. This discharge assembly configuration provides multifunctional operation, including plasma generation from different gases (argon, nitrogen, oxygen, acetylene) and deposition of composite metal nitride and oxide coatings.
Study of laser megajoule calorimeter's thermal behaviour for energy measurement uncertainty optimisation
Authors: Crespy Charles , Villate Denis , Lobios Olivier
Published: January 2013

For laser megajoule (LMJ) facility, an accurate procedure for laser pulse energy measurement is a crucial requirement. In this study, the influence of measurement procedure on LMJ calorimeter uncertainty is experimentally and numerically investigated. To this end, a 3D thermal model is developed and two experimental techniques are implemented. The metrological characteristics of both techniques are presented. As a first step, the model is validated by comparing numerical and experimental results. Then, the influence of a large number of parameters considered as likely uncertainty sources on calorimeter response is investigated: wavelength, pulse duration, ambient temperature, laser beam diameter…. The post processing technique procedure is also examined. The paper provides some of the parameters required to allow a robust and efficient calibration procedure to be produced.
Viscous forces are predominant in the zona pellucida mechanical resistance
Authors: Papi Massimiliano , Maiorana Alessandro , Douet Cécile , Maulucci Giuseppe , Parasassi Tiziana , Brunelli Roberto , Goudet Ghylène , De Spirito Marco
Published: January 2013

The zona pellucida (ZP) is a multilayer glycoprotein spherical shell surrounding mammalian eggs. The ZP's mechanical response plays a crucial role in mammalian fertilization and is a parameter commonly adopted in “in vitro fertilization” to characterize the oocytes quality. While it is assumed that ZP mechanical response is purely elastic, here we prove that dissipative forces cannot be neglected. Physiologically, this evidence implies that an increase in the spermatozoa motility can induce dramatic changes on the ZP reaction force turning ZP shell in an impenetrable barrier leading to fertility impairments.
Transition between breakdown regimes in a temperature-dependent mixture of argon and mercury using 100 kHz excitation
Authors: Sobota A. , van den Bos R. A. J. M. , Kroesen G. , Manders F.
Published: January 2013

The paper examines the breakdown process at 100 kHz in a changing temperature-dependent mixture of Ar and Hg and the associated transitions between breakdown regimes. Each measurement series started at 1400 K, 10 bar of Hg, and 0.05% admixture of Ar and finished by natural cooling at room temperature, 150 mbar of Ar, and 0.01% admixture of Hg. The E/N at breakdown as a function of temperature and gas composition was found to have a particular shape with a peak at 600 K, when Hg makes up for 66% of the gaseous mixture and Ar 34%. This peak was found to be an effect of the mixture itself, not the temperature effects or the possible presence of electronegative species. The analysis has shown that at this frequency both streamer and diffuse breakdown can take place, depending on the temperature and gas composition. Streamer discharges during breakdown are present at high temperatures and high Hg pressure, while at room temperature in 150 mbar of Ar the breakdown has a diffuse nature. In between those two cases, the radius of the discharges during breakdown was found to change in a monotonic manner, covering one order of magnitude from the size typical for streamer discharges to a diffuse discharge comparable to the size of the reactor.
Probing structural changes in Ca(1−x)Nd2x/3TiO3 ceramics by Raman spectroscopy
Authors: Lowndes Robert , Deluca Marco , Azough Feridoon , Freer Robert
Published: January 2013

Ceramics in the system Ca(1−x)Nd2x/3TiO3, intended for mobile communication applications, exhibit grossly non-linear variations in microwave dielectric properties with composition. There is evidence of a structural transition and the formation of vacancies on the A-site of the perovskite structure. High density, single phase perovskite Ca(1−x)Nd2x/3TiO3 ceramics have been prepared by the mixed oxide route. Raman spectroscopy was used to investigate the structural variations, which impact on dielectric properties. The Raman spectra show that with increasing Nd content, there is a transition from an ordered structure, to a disordered arrangement of cations and vacancies, and back to an ordered arrangement in Ca0.1Nd0.6TiO3. A structural phase transition from orthorhombic Pbnm to monoclinic C2/m coincides with the order-disorder transition at Ca0.1Nd0.6TiO3. Polarized Raman spectroscopy facilitated the assignment of the Raman modes and investigation of the role of importance of domain structures. Large variation in the plane angles was attributed to differences in domain structures. Differences in the angular dependence of the Raman modes with Nd content reflect changes in the preferred orientation of the domains from lamellar twins, to wedge shaped and back to lamellar twins.
Electron irradiation induced reduction of the permittivity in chalcogenide glass (As2S3) thin film
Authors: San-Román-Alerigi Damián P. , Anjum Dalaver H. , Zhang Yaping , Yang Xiaoming , Benslimane Ahmed , Ng Tien K. , Hedhili Mohamed N. , Alsunaidi Mohammad , Ooi Boon S.
Published: January 2013

In this paper, we investigate the effect of electron beam irradiation on the dielectric properties of As2S3 chalcogenide glass. By means of low-loss electron energy loss spectroscopy, we derive the permittivity function, its dispersive relation, and calculate the refractive index and absorption coefficients under the constant permeability approximation. The measured and calculated results show a heretofore unseen phenomenon: a reduction in the permittivity of ≥40%. Consequently a reduction of the refractive index of 20%, hence, suggests a conspicuous change in the optical properties of the material under irradiation with a 300 keV electron beam. The plausible physical phenomena leading to these observations are discussed in terms of the homopolar and heteropolar bond dynamics under high energy absorption. The reported phenomena, exhibited by As2S3-thin film, can be crucial for the development of photonics integrated circuits using electron beam irradiation method.
Effects of radio-frequency noise suppression on the microstrip line using FeCoNiB soft magnetic thin films
Authors: Qiu Jing
Published: January 2013

The FeCoNiB thin films with excellent soft magnetic properties were synthesized by radio frequency (RF) magnetron sputtering. Effects of RF noise suppression on the microstrip line using FeCoNiB films were investigated. It is found that FeCoNiB films with appropriate low Ni content exhibit excellent noise suppression properties including a maximum attenuation of 17.4 dB. Owing to the eddy current loss, the ferromagnetic resonance loss and L-C resonance, the intensity and frequency of RF signal attenuation can be adjusted by the geometric dimension of magnetic thin films and dielectric layers. These results reveal that the presented thin films possess high potential for RF noise suppressors.
Quantum magnetotransport properties of ultrathin topological insulator films
Authors: Tahir M. , Sabeeh K. , Schwingenschlögl U.
Published: January 2013

We study the quantum magnetotransport in ultrathin topological insulator films in an external magnetic field considering hybridization between the upper and lower surfaces of the film. We investigate the two possible mechanisms for splitting of Landau levels, Zeeman and hybridization effects, and show that their interplay leads to minima in the collisional and Hall conductivities with a metal-to-insulator phase transition at the charge neutrality point. Hall plateaus arise at unusual multiples of e2/h. Evidence of a quantum phase transition for the zeroth and splitting of the higher Landau levels is found from the temperature and magnetic field dependences of the transport.
Equivalent circuit models for the analysis of electric response and magnetic response of compact triangular electromagnetic resonator
Authors: Zhu Cheng , Li Ke , Chen Yang , Li Tong , Zhai Hui-Qing , Li Long , Liang Chang-Hong
Published: January 2013

The equivalent circuit model (ECM) and the design of compact triangular electromagnetic resonator (TER) are both introduced in this paper. ECM with analytic expressions is utilized to obtain the dispersion curves of effective permittivity and effective permeability of four kinds of TER with/without interdigital capacitor. Compared with effective parameters obtained by the parametric retrieval algorithm using simulated and measured s-parameters, the results of ECM correspond very well with the two results above, which demonstrates the effectiveness of ECM and provides us a new way to analyze the effective parameters of metamaterials.
Kinetics of light induced defect creation in organic solar cells
Authors: Street R. A. , Davies D. M.
Published: January 2013

The kinetics of light-induced recombination centers in bulk heterojunction organic solar cells are measured as a function of exposure time, intensity, and the illumination photon energy. The density of induced centers increases with exposure but stabilizes partially due to self-annealing. UV exposure is roughly 50 times more effective for defect creation than white light or yellow-filtered white light. Light-induced breaking of C-H bonds to create H-related localized states is proposed as the underlying mechanism.
Magnetic transition broadening and local lattice distortion in the negative thermal expansion antiperovskite Cu1−xSnxNMn3
Authors: Tong P. , Louca Despina , King Graham , Llobet Anna , Lin J. C. , Sun Y. P.
Published: January 2013

The local distortion indicated by the split of the Cu/Sn-Mn bonds for the negative thermal expansion (NTE) materials Cu1−xSnxNMn3 (x = 0.1 and 0.5) was observed using neutron pair distribution function. The distribution of Cu/Sn-Mn bonds upon Sn doping is suggested to be attributable to the fluctuation in the hybridization of Mn d with Sn p orbitals. Accordingly, the antiferromagnetic (AFM) coupling mediated by the p-d hybridization fluctuates in strength. Consequently, the AFM transition closely coupled with the volume change is broadened, leading to the NTE.
Reducing minimum flash ignition energy of Al microparticles by addition of WO3 nanoparticles
Authors: Ohkura Yuma , Rao Pratap M. , Sun Cho In , Zheng Xiaolin
Published: January 2013

Aluminum (Al) is an attractive solid fuel for rocket propulsion and energy conversion systems due to its large volumetric energy density, earth abundance, and low cost. Nonintrusive optical flash ignition is attractive for many applications due to its simplicity and flexibility in controlling the area exposed to the flash. However, flash ignition of Al microparticles (MPs) is challenging due to their higher minimum flash ignition energy, which originates from weaker light absorption and higher ignition temperature compared to Al nanoparticles (NPs). Herein, the minimum flash ignition energy of Al MPs is reduced by the addition of WO3 NPs.
Axial strain in GaAs/InAs core-shell nanowires
Authors: Biermanns Andreas , Rieger Torsten , Bussone Genziana , Pietsch Ullrich , Grützmacher Detlev , Ion Lepsa Mihail
Published: January 2013

We study the axial strain relaxation in GaAs/InAs core-shell nanowire heterostructures grown by molecular beam epitaxy. Besides a gradual strain relaxation of the shell material, we find a significant strain in the GaAs core, increasing with shell thickness. This strain is explained by a saturation of the dislocation density at the core-shell interface. Independent measurements of core and shell lattice parameters by x-ray diffraction reveal a relaxation of 93% in a 35 nm thick InAs shell surrounding cores of 80 nm diameter. The compressive strain of −0.5% compared to bulk InAs is accompanied by a tensile strain up to 0.9% in the GaAs core.
Remanent-polarization-induced enhancement of photoluminescence in Pr3+-doped lead-free ferroelectric (Bi0.5Na0.5)TiO3 ceramic
Authors: Tian Xiangling , Wu Zheng , Jia Yanmin , Chen Jianrong , Zheng R. K. , Zhang Yihe , Luo Haosu
Published: January 2013

We found that ferroelectric remanent polarization can remarkably enhance the photoluminescence intensity of Pr3+-doped lead-free (Bi0.5Na0.5)TiO3 ceramics. An enhancement in photoluminescence intensity of ∼35% was obtained in the 0.5 mol. % Pr3+-doped sample, attributed to the decrease of crystal symmetry that occurs in poled ferroelectric ceramics. Our results reveal the great potential to enhance the photoluminescence intensity in rare-earth doped ferroelectric ceramics through ferroelectric polarization and to monitor the ferroelectric remanent polarization strength through measuring the photoluminescence spectra. We also found that the threshold of Pr3+ concentration quenching increased in the poled Pr3+-doped lead-free (Bi0.5Na0.5)TiO3 ceramic sample.
Strain engineering enhancement of surface plasmon polariton propagation lengths for gold nanowires
Authors: Ben Xue , Park Harold S.
Published: January 2013

We present in this work the notion of using elastic strain engineering to reduce the intrinsic losses in a metal for subwavelength optical signal processing. By using a simple, analytical waveguide model, we demonstrate that application of uniaxial tensile strains below the yield strain of gold nanowires results in substantial increases of more than 70% in the surface plasmon polariton propagation lengths at optical frequencies. The enhancement is primarily due to a reduction in the core electron density, and is found to be size-independent for a wide range of nanowire diameters, while exhibiting a linear dependence on the applied tensile strain.
Broadly tunable (440–670 nm) solid-state organic laser with disposable capsules
Authors: Mhibik Oussama , Leang Tatiana , Siove Alain , Forget Sébastien , Chénais Sébastien
Published: January 2013

An innovative concept of thin-film organic solid-state laser is proposed, with diffraction-limited output and a broad tuning range covering the visible spectrum under UV optical pumping. The laser beam is tunable over 230 nm, from 440 to 670 nm, with a 3 nm full width at half maximum typical spectral width. The structure consists of a compact fixed bulk optical cavity, a polymeric intracavity etalon for wavelength tuning, as well as five different disposable glass slides coated with a dye-doped polymer film, forming a very simple and low-cost gain medium. The use of interchangeable/disposable “gain capsules” is an alternative solution to photodegradation issues, since gain chips can be replaced without realignment of the cavity. The laser lifetime of a single chip in ambient conditions and without encapsulation was extrapolated to be around 107 pulses at a microjoule energy-per-pulse level.
Photoelectron spectroscopic study of band alignment of polymer/ZnO photovoltaic device structure
Authors: Nagata T. , Oh S. , Yamashita Y. , Yoshikawa H. , Ikeno N. , Kobayashi K. , Chikyow T. , Wakayama Y.
Published: January 2013

Using x-ray photoelectron spectroscopy, we investigated the band alignment of a Ag/poly(3-hexylthiophene-2,5-diyl) (P3HT)/ZnO photovoltaic structure. At the P3HT/ZnO interface, a band bending of P3HT and a short surface depletion layer of ZnO were observed. The offset between the highest occupied molecular orbital of P3HT and the conduction band minimum of ZnO at the interface contributed to the open circuit voltage (Voc) was estimated to be approximately 1.5 ± 0.1 eV, which was bigger than that of the electrically measured effective Voc of P3HT/ZnO photovoltaic devices, meaning that the P3HT/ZnO photovoltaic structure has the potential to provide improved photovoltaic properties.
Replicating the discovery of Venus’s atmosphere
Authors: Shiltsev Vladimir , Nesterenko Igor , Rosenfeld Randall
Published: January 2013

The 2012 transit of Venus gave us a chance to reproduce Mikhail Lomonosov’s 1761 observation and demonstrate the excellent quality of 18th-century telescopes.
Crowdsourced Cartography: Mapping Experience and Knowledge
Authors: Dodge Martin , Kitchin Rob
Published: January 2013

This paper considers the emerging phenomenon of crowdsourced cartography in relation to ideas about the organisation of contemporary knowledge production in capitalist societies. Taking a philosophical perspective that views mapping as a processual, creative, productive act, constructed through citational, embodied, and contextual experiences, we examine how we might profitably analyse collaborative crowdsourced projects like OpenStreetMap to better understand geographic knowledge production in a shifting political economy and sociotechnical landscape. We begin by characterising crowdsourcing practices in the wider context of Web 2.0, which some commentators assert is rapidly becoming a new, dominant mode of knowledge production. We then contextualise Web 2.0 knowledge production, drawing upon the ideas of sociologist George Ritzer, and his notion of ‘prosumption’, geographer Michael Goodchild's idea of volunteerist ‘citizen scientists’, and economic commentator Nicholas Carr's critique of the ‘ignorance of crowds’. We then go on to discuss the changing nature of cartography in the Web 2.0 era with respect to authorship, ontology, representation, and temporality.
Augmented Realities and Uneven Geographies: Exploring the Geolinguistic Contours of the Web
Authors: Graham Mark , Zook Matthew
Published: January 2013

This paper analyzes the digital dimensions of places as represented by online, geocoded references to the economic, social, and political experiences of the city. These digital layers are invisible to the naked eye, but form a central component of the augmentations and mediations of place enabled by hundreds of millions of mobile computing devices and other digital technologies. The analysis highlights how these augmentations of place differ across space and language and highlights both the differences and some of the causal factors behind them. This is performed through a global study of all online content indexed within Google Maps, and more specific analyses of the linguistically and topically segregated layers of information over four selected places. The uneven linguistic geographies that this study reveals undoubtedly influence the many ways in which place is enacted and brought into being. The larger aim of this project is to use these initial mappings of the linguistic contours of the geoweb to push forward a broader debate about how augmented inclusions and exclusions, visibilities and invisibilities will shape the way that places become defined, imagined, and experienced.
Spaces of Neoliberal Experimentation: Soft Spaces, Postpolitics, and Neoliberal Governmentality
Authors: Haughton Graham , Allmendinger Phil , Oosterlynck Stijn
Published: January 2013

This paper examines the proliferation of soft spaces of governance, focusing on planning. We move beyond more functional explanations to explore the politics of soft spaces, more specifically how soft space forms of governance operate as integral to processes of neoliberalisation, highlighting how such state forms facilitate neoliberalisation through their flexibility and variability. Recent state restructuring of the planning sector and emerging trends for soft spaces in England under the Coalition government proposals are discussed.
Situating Performative Neogeography: Tracing, Mapping, and Performing “Everyone's East Lake”
Authors: Lin Wen
Published: January 2013

The emergence and proliferation of neogeographic practices since the mid-2000s have drawn significant attention from GIS scholars. I seek to contribute to the discussion on situating neogeography, particularly through examining the performative dimension of neogeography. To understand performative neogeographic practices I enroll de Certeau's notion of tactics to read these practices as tactical spatial narratives, which may provide different possibilities for spaces of civic engagement and political intervention in an increasingly networked and yet individualized society. I also draw upon theoretical insights from critical GIS and critical social theory to situate and trace the constructions of performative neogeographic practices within particular sociopolitical contexts. Through this synthesized framework, I discuss a case study involved in a participatory art performance project entitled “Everyone's East Lake” in China. Drawing upon interviews and document analysis, the author examines how participants utilize neogeographic mapping as a form of performance and tactical act in response to the dominant corporate and state power. While performative mapping has long been used by artists and cartographers, this case study illustrates how these performative neogeographic practices might highlight different intersections between self-identities, community participation, and sociopolitical conditions, through reconfigurations of mobile and networked mapping technologies. These dynamic, hybrid, and networked mapping practices necessitate a broader conceptualization of activism through mapping in critical GIS research.