bluuebunny/crossref_metadata_2025 huggingface dataset:
Metacognition may be more impaired than mindreading in autism
Authors: Williams David M. , Lind Sophie E. , Happé Francesca
Published: April 2009

This commentary focuses on evidence from autism concerning the relation between metacognition and mindreading. We support Carruthers' rejection of models 1 (independent systems) and 3 (metacognition before mindreading), and provide evidence to strengthen his critique. However, we also present evidence from autism that we believe supports model 2 (one mechanism, two modes of access) over model 4 (mindreading is prior).
Learning without thinking
Authors: Boakes R. A.
Published: April 2009

The main conclusion to draw from Mitchell et al's article is that it is difficult to disentangle cognitive and learning processes in contingency and causal experiments. More compelling evidence for human associate learning comes from research where, because of the type of events involved, participants are unable or unlikely to think about the relationships between the events.
The new enlightenment hypothesis: All learners are rational
Authors: Nolan Rita
Published: April 2009

The proposal to recruit available formal structures to build an algorithmic model of all learning falters on close examination of its essential assumption: that the input and output of the model are propositional in structure. After giving three framework considerations, I describe three possibly fatal problems with this assumption, concluding each with a question that needs answering to avoid fatality.
There is more to thinking than propositions
Authors: Penn Derek C. , Cheng Patricia W. , Holyoak Keith J. , Hummel John E. , Povinelli Daniel J.
Published: April 2009

We are big fans of propositions. But we are not big fans of the “propositional approach” proposed by Mitchell et al. The authors ignore the critical role played by implicit, non-inferential processes in biological cognition, overestimate the work that propositions alone can do, and gloss over substantial differences in how different kinds of animals and different kinds of cognitive processes approximate propositional representations.
Measuring interstellar magnetic fields by radio synchrotron emission
Authors: Beck Rainer
Published: April 2009

Radio synchrotron emission, its polarization and its Faraday rotation are powerful tools to study the strength and structure of interstellar magnetic fields. The total intensity traces the strength and distribution of total magnetic fields. Total fields in gas-rich spiral arms and bars of nearby galaxies have strengths of 20–30 μGauss, due to the amplification of turbulent fields, and are dynamically important. In the Milky Way, the total field strength is about 6 μG near the Sun and several 100 μG in filaments near the Galactic Center. – The polarized intensity measures ordered fields with a preferred orientation, which can be regular or anisotropic fields. Ordered fields with spiral structure exist in grand-design, barred, flocculent and even in irregular galaxies. The strongest ordered fields are found in interarm regions, sometimes forming “magnetic spiral arms” between the optical arms. Halo fields are X-shaped, probably due to outflows. – The Faraday rotation of the polarization vectors traces coherent regular fields which have a preferred direction. In some galaxies Faraday rotation reveals large-scale patterns which are signatures of dynamo fields. However, in most galaxies the field has a complicated structure and interacts with local gas flows. In the Milky Way, diffuse polarized radio emission and Faraday rotation of the polarized emission from pulsars and background sources show many small-scale and large-scale magnetic features, but the overall field structure in our Galaxy is still under debate.
The magnetic field structure in the multi-source magnetized core NGC 2024 FIR 5
Authors: Alves Felipe de O. , Girart J. M. , Lai S.-P. , Rao R. , Zhang Q.
Published: April 2009

This work reports high resolution SMA polarimetric observations toward NGC 2024 FIR 5, a magnetized core previously found to harbour protostars. Our 345 GHz data indicates the presence of an extended dust emission associated with the dense core where the protostars are embedded. The 3σ polarized intensity shows depolarization toward the peak of Stokes I emission. This diminishing polarized flux implies that the alignment efficiency of the core dust grains is low within higher column densities where grain properties are likely different. The derived magnetic field geometry exhibits pinched field lines which are typical in evolved supercritical clouds where the magnetic field no longer support the core from collapsing. As a consequence for protostars, the gravitational pulling along the disk's long axis makes an equatorial bend to the field lines that, in turn, results in a hourglass shape. The SMA field structure agrees perfectly with the BIMA map. However, models are still necessary to provide a complete description of the evolutionary scenario of FIR 5.
Probing interstellar magnetic fields with Supernova remnants
Authors: Kothes Roland , Brown Jo-Anne
Published: April 2009

As Supernova remnants expand, their shock waves are freezing in and compressing the magnetic field lines they encounter; consequently we can use Supernova remnants as magnifying glasses for their ambient magnetic fields. We will describe a simple model to determine emission, polarization, and rotation measure characteristics of adiabatically expanding Supernova remnants and how we can exploit this model to gain information about the large scale magnetic field in our Galaxy. We will give two examples: The SNR DA530, which is located high above the Galactic plane, reveals information about the magnetic field in the halo of our Galaxy. The SNR G182.4+4.3 is located close to the anti-centre of our Galaxy and reveals the most probable direction where the large-scale magnetic field is perpendicular to the line of sight. This may help to decide on the large-scale magnetic field configuration of our Galaxy. But more observations of SNRs are needed.
Observations of magnetic fields toward the star forming region S88B
Authors: Sarma Anuj P. , Brogan C. L. , Bourke T. , Eftimova M.
Published: April 2009

We present observations of the high mass star forming region S88B taken with the VLA with the aim of measuring magnetic fields via the Zeeman effect. By observing thermal absorption lines of OH at 1665 and 1667 MHz, we obtain magnetic fields between 90 and 210 μG. We find these magnetic fields to be dynamically significant in this region.
On global stability of thin ionized disks immersed in an external magnetic field
Authors: Liverts Edward , Mond Michael
Published: April 2009

The problem of the global stability of rotating magnetized thin disks is considered. The appropriate boundary value problem (BVP) of the linearized MHD equations is solved by employing the WKB approximation to describe the dynamical development of an initial perturbation. The eigenfrequencies as well as eigenfunctions are explicitly obtained and are verified numerically. The importance of considering the initial value problem (IVP) as well as the question of global stability for finite systems is emphasized and discussed in detail. It is further shown that thin enough disks are stable (global stability) but as their thickness grows increasing number of unstable modes participate in the solution of the IVP. However it is demonstrated that due to the localization of the initial perturbation the growth time of the instability may be significantly longer than the calculated inverse growth rate of the individual unstable eigenfunctions.
Axisymmetric magneto-rotational instability in viscous accretion disks
Authors: Masada Youhei , Sano Takayoshi
Published: April 2009

Axisymmetric MRI in viscous accretion disks is investigated. The linear growth of the viscous MRI is characterized by the Reynolds number RMRI ≡ v2A/νΩ, where vA is the Alfvén velocity, ν is the kinematic viscosity, and Ω is the angular velocity of the disk. Although the linear growth of the MRI is suppressed as the Reynolds number decreases, its nonlinear behavior is found to be almost independent of RMRI. At the nonlinear stage, the channel flow grows and the Maxwell stress increases even though RMRI is much smaller than unity. Nonlinear behavior of the MRI in the viscous regime can be explained by the characteristics of the linear dispersion relation. Applying our results to the case with both viscosity and resistivity, it is anticipated that the critical value of the Lundquist number SMRI ≡ v2A/ηΩ for active turbulence would depend on the magnetic Prandtl number Pm ≡ ν/η, where η is the magnetic diffusivity.
The magnetic field in the X-ray binary Cyg X-1
Authors: Karitskaya Eugenia A. , Bochkarev N. G. , Hubrig S. , Gnedin Yu. N. , Pogodin M. A. , Yudin R. V. , Agafonov M. I. , Sharova O. I.
Published: April 2009

VLT FORS 1 observations indicate the presence of a variable significant magnetic field in the X-ray binary Cyg X-1. The importance of this investigation comes from the fact that it rules one of the most significant BH manifestations: the X-ray millisecond flickering, usually related to reconnection of magnetic lines in the innermost part of the accretion disc.
Spectropolarimetry of supernova remnant G296.5 + 10.0
Authors: Harvey-Smith Lisa , Gaensler Bryan M. , Ng C.-Y. , Green Anne J.
Published: April 2009

Radio continuum emission from the supernova remnant G296.5 + 10.0 was observed using the Australia Telescope Compact Array. Using a 104 MHz bandwidth split into 13 × 8 MHz spectral channels, it was possible to produce a pixel-by-pixel image of Rotation Measure (RM) across the entire remnant. A lack of correlation between RM and X-ray surface brightness reveals that the RMs originate from outside the remnant. Using this information, we will characterise the smooth component of the magnetic field within the supernova remnant and attempt to probe the magneto-ionic structure and turbulent scale sizes in the ISM and galactic halo along the line-of-sight.
Paradigm shifts in solar dynamo modeling
Authors: Brandenburg Axel
Published: April 2009

Selected topics in solar dynamo theory are being highlighted. The possible relevance of the near-surface shear layer is discussed. The role of turbulent downward pumping is mentioned in connection with earlier concerns that a dynamo-generated magnetic field would be rapidly lost from the convection zone by magnetic buoyancy. It is argued that shear-mediated small-scale magnetic helicity fluxes are responsible for the success of some of the recent large-scale dynamo simulations. These fluxes help in disposing of excess small-scale magnetic helicity. This small-scale magnetic helicity, in turn, is generated in response to the production of an overall tilt in each Parker loop. Some preliminary calculations of this helicity flux are presented for a system with uniform shear. In the Sun the effects of magnetic helicity fluxes may be seen in coronal mass ejections shedding large amounts of magnetic helicity.
X-ray jets and magnetic flux emergence in the Sun
Authors: Moreno-Insertis Fernando
Published: April 2009

Magnetized plasma is emerging continually from the solar interior into the atmosphere. Magnetic flux emergence events and their consequences in the solar atmosphere are being observed with high space, time and spectral resolution by a large number of space missions in operation at present (e.g. SOHO, Hinode, Stereo, Rhessi). The collision of an emerging and a preexisting magnetic flux system in the solar atmosphere leads to the formation of current sheets and to field line reconnection. Reconnection under solar coronal conditions is an energetic event; for the field strengths, densities and speeds involved in the collision of emerging flux systems, the reconnection outflows lead to launching of high-speed (hundreds of km/s), high-temperature (107 K) plasma jets. Such jets are being observed with the X-Ray and EUV detectors of ongoing satellite missions. On the other hand, the spectacular increase in computational power in recent years permits to carry out three-dimensional numerical experiments of the time evolution of flux emerging systems and the launching of jets with a remarkable degree of detail.

In this review, observation and modeling of the solar X-Ray jets are discussed. A two-decade long computational effort to model the magnetic flux emergence events by different teams has led to numerical experiments which explain, even quantitatively, many of the observed features of the X-ray jets. The review points out that, although alternative mechanisms must be considered, flux emergence is a prime candidate to explain the launching of the solar jets.
North-south asynchrony and long-term variations of sunspot latitudes
Authors: Zolotova Nadezhda V. , Ponyavin D. I.
Published: April 2009

The long-term records of sunspot area available separately for Northern and Southern Hemispheres have been investigated by means of cross-recurrence technique. Phase component of the north-south asymmetry was extracted. This measure demonstrates long-period systematic variations with the sign change of hemispheric leading in 1930s and 1960s. Moreover phase north-south asynchrony anticorrelates with the so called magnetic equator, which was defined as difference of the mean sunspot latitudes between two hemispheres. Relationships of the phase north-south asynchrony, magnetic equator and butterfly diagrams are presented and discussed.
The role of intrinsic magnetic fields in planetary evolution and habitability: the planetary protection aspect
Authors: Khodachenko Maxim L. , Lammer H. , Lichtenegger H. I. M. , Grießmeier J.-M. , Holmström M. , Ekenbäck A.
Published: April 2009

The widely used definition of a habitable zone (HZ) for planets as a circumstellar area, where the star's luminosity is sufficiently intense to maintain liquid water at the surface of a planet, is shown to be too simplified. The role of a host star's activity and the intrinsic magnetic field of a planet with respect to their influence on mass loss processes of close-in gas giants and a definition of a HZ for the terrestrial-type exoplanets are discussed. The stellar X-ray/EUV radiation and the stellar wind result in ionization, heating, chemical modification, and slow erosion of the planetary upper atmospheres throughout their lifetime. The closer the planet is to the star, the more efficient are these processes, and therefore, the more important becomes the magnetic protection of a planet as a potential habitat. Different ways for planetary magnetic dipole moment estimation, based on existing magnetic dynamo scaling laws as well as on the recent measurements of hot atomic hydrogen clouds around close-in ‘Hot Jupiters’ are considered, and the predictions of these estimations are compared to each other.
Is the wind of the Oe star HD 155806 magnetically confined?
Authors: Petit Véronique , Fullerton A. W. , Bagnulo S. , Wade G. A. ,   the MiMeS Collaboration
Published: April 2009

Oe stars are a subset of the O-type stars that exhibit emission lines from a circumstellar disk. The recent detection of magnetic fields in some O-type stars suggests a possible explanation for the stability of disk-like structures around Oe stars. According to this hypothesis, the wind of the star is channeled by a dipolar magnetic field producing a disc in the magnetic equatorial plane. As a test of this model, we have obtained spectropolarimetric observations of the hottest Galactic Oe star HD 155806. Here we discuss its results and implications.
Searching for a link between the presence of chemical spots on the surface of HgMn stars and their weak magnetic fields
Authors: Savanov Igor S. , Hubrig S. , González J. F. , Schöller M.
Published: April 2009

We present the results of mapping the HgMn star AR Aur using the Doppler Imaging technique for several elements and discuss the obtained distributions in the framework of a magnetic field topology.
Stellar nonlinear dynamos: observations and modelling
Authors: Tuominen Ilkka , Korpi Maarit J. , Käpylä Petri J. , Lindborg Marjaana , Ilyin Ilya
Published: April 2009

Recent numerical modelling of mean-field stellar dynamos with induction and Reynolds' equations show that, with increasing rotation, field symmetry changes from an axisymmetric solar type to a nonaxymmetric one, where the so-called active longitudes in the same stellar hemisphere are predicted to be of opposite polarities. It was originally named Active star Hale rule in Tuominen et al. (2002), being an analogue to the famous bipolar sunspot polarity rule but different in scale and being a global phenomenon. In addition to long timeseries of temperature mapping and photometry, during the last few years we have been able to measure accurately polarization spectra of an active late-type star II Peg with the upgraded spectropolarimetric option of the high-resolution spectrograph SOFIN at the Nordic Optical Telescope, La Palma. The magnetic inversions (Carroll et al., Kochukhov et al.) can be compared to the dynamo models and the preliminary results show some resemblance to the dynamo solutions.
Low-dimensional models of stellar and galactic dynamos
Authors: Sokoloff Dimitry , Nefyodov S.
Published: April 2009

A regular method how to simplify dynamo model for a particular celestial body up to a dynamical system is suggested. Dynamical system obtained occurs specific for a thin galactic disc, a fully convective star and a thin convective shell.
Radial differential rotation vs. surface differential rotation: investigation based on dynamo models
Authors: Korhonen Heidi , Elstner Detlef
Published: April 2009

Differential rotation plays a crucial role in the alpha-omega dynamo, and thus also in creation of magnetic fields in stars with convective outer envelopes. Still, measuring the radial differential rotation on stars is impossible with the current techniques, and even the measurement of surface differential rotation is difficult. In this work we investigate the surface differential rotation obtained from dynamo models using similar techniques as are used on observations, and compare the results with the known radial differential rotation used when creating the dynamo model.
Time series Doppler imaging using STELLA
Authors: Weber Michael , Strassmeier Klaus G. , Granzer Thomas
Published: April 2009

One of the core programs of the STELLA robotic observatory is to monitor the stellar activity on a sample of stars using Doppler imaging. We present first preliminary results of the rapidly rotating, single giant star HD 31993 from the first two years of operation. We confirm the presence and orientation of differential rotation on the stellar surface.
Magnetic geometries of Sun-like stars: exploring the mass-rotation plane
Authors: Petit Pascal , Dintrans B. , Aurière M. , Catala C. , Donati J.-F. , Fares R. , Gastine T. , Lignières F. , Morgenthaler A. , Morin J. , Paletou F. , Ramirez J. , Solanki S. K. , Théado S.
Published: April 2009

Sun-like stars are able to continuously generate a large-scale magnetic field through the action of a dynamo. Various physical parameters of the star are able to affect the dynamo output, in particular the rotation and mass. Using the NARVAL spectropolarimeter (Observatoire du Pic du Midi, France), it is now possible to measure the large-scale magnetic field of solar analogues (i.e. stars very close to the Sun in the mass-rotation plane, including strict solar twins). From spectropolarimetric time-series, tomographic inversion enables one to reconstruct the field geometry and its progressive distortion under the effect of surface differential rotation. We show the first results obtained on a sample of main-sequence dwarfs, probing masses between 0.7 and 1.4 solar mass and rotation rates between 1 and 3 solar rotation rate.
Magnetic fields, winds and X-rays of massive stars in the Orion Nebula Cluster
Authors: Petit Véronique , Wade G. A. , Drissen L. , Montmerle T. , Alecian E.
Published: April 2009

In massive stars, magnetic fields are thought to confine the outflowing radiatively-driven wind, resulting in X-ray emission that is harder, more variable and more efficient than that produced by instability-generated shocks in non-magnetic winds. Although magnetic confinement of stellar winds has been shown to strongly modify the mass-loss and X-ray characteristics of massive OB stars, we lack a detailed understanding of the complex processes responsible. The aim of this study is to examine the relationship between magnetism, stellar winds and X-ray emission of OB stars. In conjunction with a Chandra survey of the Orion Nebula Cluster, we carried out spectropolarimatric ESPaDOnS observations to determine the magnetic properties of massive OB stars of this cluster.
Cosmic-ray driven dynamo in galactic disks
Authors: Hanasz Michał , Otmianowska-Mazur K. , Lesch H. , Kowal G. , Soida M. , Wóltański D. , Kowalik K. , Pawłaszek R. K. , Kulesza-Żydzik B.
Published: April 2009

We present new developments on the Cosmic–Ray driven, galactic dynamo, modeled by means of direct, resistive CR–MHD simulations, performed with ZEUS and PIERNIK codes. The dynamo action, leading to the amplification of large–scale galactic magnetic fields on galactic rotation timescales, appears as a result of galactic differential rotation, buoyancy of the cosmic ray component and resistive dissipation of small–scale turbulent magnetic fields. Our new results include demonstration of the global–galactic dynamo action driven by Cosmic Rays supplied in supernova remnants. An essential outcome of the new series of global galactic dynamo models is the equipartition of the gas turbulent energy with magnetic field energy and cosmic ray energy, in saturated states of the dynamo on large galactic scales.
Pulsars & Magnetars
Authors: Kramer Michael
Published: April 2009

The largest magnetic field encountered in the observable Universe can be found in neutron stars, in particular in radio pulsars and magnetars. While recent discoveries have slowly started to blur the distinction between these two classes of highly magnetized neutron stars, it is possible that both types of sources are linked via an evolutionary sequence. Indications for this to be the case are obtained from observations of the spin-evolution of pulsars. It is found that most young pulsars are heading across the top of the main distribution of radio pulsars in the P–Ṗ-diagram, suggesting that at least a sub-class of young pulsars may evolve into objects with magnetar-like magnetic field strengths. Part of this evolutionary sequence could be represented by RRATs which appear to share at least in parts properties with both pulsars and magnetars.
Why we need to measure turbulent magnetic fields in HII regions
Authors: Beckman John E. , Relaño Mónica
Published: April 2009

We have measured the emission line profiles in Hα from populations of HII regions in nearby spiral galaxies, and extracted their non-thermal line widths. These are supersonic for the more luminous regions. We infer from plots of line width, σ, against Hα luminosity, a set of regions in virial equilibrium, and derive their masses summing all known components. The virial masses are considerably larger. If this discrepancy, and the supersonic line widths, are due to the presence of magnetic fields, we can estimate their strengths at a few microgauss. Observational confirmation is clearly required.
The integrated polarization of spiral galaxies
Authors: Stil Jeroen M. , Krause Marita , Mitchell Lydia , Beck Rainer , Taylor A. Russell
Published: April 2009

We present deep observations of polarized radio emission of distant spiral galaxies with the Effelsberg 100-m telescope† at 4.8 GHz. These cross scans with sensitivity of 50 μJy or better open the possibility of a statistical study of magnetic field properties and internal Faraday rotation as a function of inclination for a large sample of unresolved galaxies. The Square Kilometre Array (SKA) will be able to detect polarization of spiral galaxies to high redshift, probing the evolution of magnetic fields in disk galaxies over cosmic time.
DRAO deep polarization study at 1.4 GHz
Authors: Grant Julie K. , Taylor A. R. , Stil J. M. , Ricci R. , O'Sullivan S. P. , Landecker T. L. , Kothes R. , Ransom R. R.
Published: April 2009

The Dominion Radio Astrophysical Observatory synthesis telescope (DRAO-ST) was used to produce a deep polarization mosaic at 1.4 GHz to a noise level of 45 microJy beam−1 for both Stokes Q and U at 1′ resolution. The DRAO deep field covers 8.6 sq. degrees in polarization centered on the ELAIS N1 field. We identified over 1700 total intensity (Stokes I) radio sources of which 197 are linearly polarized down to a flux density level of 203 microJy. The fractional polarization of faint polarized sources are flat down to a polarized flux density of about 4 mJy, at which point the numbers increase, until the counts drop for polarized flux densities below 1 mJy. These faint polarized radio sources are mostly AGNs with luminosities below the traditional FRI/FRII boundary. Follow-up observations with the VLA show that the origin of the polarization of the radio sources down to a polarized flux of 1 mJy comes from both the lobes and central region of these objects.
Deriving AGN properties from circular and linear radio polarimetry
Authors: Cenacchi Elena , Kraus A. , Mack K.-H.
Published: April 2009

We report multi-frequency circular polarization measurements for the radio source 0056-00 taken at the Effelsberg 100-m radio telescope. The data reduction is based on a new calibration procedure that allows the contemporary measurement of the four Stokes parameters with single-dish radio telescopes.
Cosmic magnetism with the Square Kilometre Array and its pathfinders
Authors: Gaensler Bryan M.
Published: April 2009

One of the five key science projects for the Square Kilometre Array (SKA) is “The Origin and Evolution of Cosmic Magnetism”, in which radio polarimetry will be used to reveal what cosmic magnets look like and what role they have played in the evolving Universe. Many of the SKA prototypes now being built are also targeting magnetic fields and polarimetry as key science areas. Here I review the prospects for innovative new polarimetry and Faraday rotation experiments with forthcoming facilities such as ASKAP, LOFAR, the ATA, the EVLA, and ultimately the SKA. Sensitive wide-field polarisation surveys with these telescopes will provide a dramatic new view of magnetic fields in the Milky Way, in nearby galaxies and clusters, and in the high-redshift Universe.
Testing the cosmological evolution of magnetic fields in galaxies with the SKA
Authors: Arshakian Tigran G. , Beck Rainer , Krause Marita , Sokoloff Dimitry
Published: April 2009

We investigate the cosmological evolution of large- and small-scale magnetic fields in galaxies at high redshifts. Results from simulations of hierarchical structure formation cosmology provide a tool to develop an evolutionary model of regular magnetic fields coupled to galaxy formation and evolution. Turbulence in protogalactic halos generated by thermal virialization can drive an efficient turbulent dynamo. The mean-field dynamo theory is used to derive the timescales of amplification and ordering of regular magnetic fields in disk and dwarf galaxies. For future observations with the SKA, we predict an anticorrelation at fixed redshift between galaxy size and the ratio between ordering scale and galaxy size. Undisturbed dwarf galaxies should host fully coherent fields at z < 1, spiral galaxies at z < 0.5.
Transport properties and dynamic processes in a fault zone from samples recovered from TCDP Hole B of the Taiwan Chelungpu Fault Drilling Project
Authors: Tanikawa Wataru , Sakaguchi Masumi , Hirono Tetsuro , Lin Weiren , Soh Wonn , Song Sheng‐Rong
Published: April 2009

We measured transport properties at a confining pressure of 60 MPa in core samples from the fault zone in Hole B of the Taiwan Chelungpu Fault Drilling Project (TCDP). Permeability and specific storage of the fault gouge range from 3 × 10−15 to 1 × 10−17 m2 and from 2 × 10−10 to 7 × 10−10 Pa−1, respectively, and the measured hydraulic diffusivity was 6 × 10−5 m2/s, which is consistent with the data measured in situ. Numerical analysis of the thermal pressurization mechanism during the 1999 Chi‐Chi earthquake using laboratory measured transport and frictional properties showed that pore pressure at the fault zone increased dramatically during slip, whereas temperature increased only moderately to 400°C at the end of slip. The results indicate that dehydration of interlayer water in smectite is plausibly caused by frictional heating, although such dehydration does not influence fault weakening. The decomposition reactions of other minerals are difficult to explain for only one slip event. A magnetic susceptibility anomaly observed in the fault zone is consistent with the modeling results, although low contents of inorganic carbon and clay minerals are not. We concluded that these inconsistencies can possibly be explained by the combined effects of enhancement of chemical reactions by mechanochemical influences and periodic movement on the Chelungpu fault. High‐temperature water‐rock interactions are also a possible explanation for inconsistencies.
Gravity wave temperature variance calculated using the ray‐based spectral parameterization of convective gravity waves and its comparison with Microwave Limb Sounder observations
Authors: Choi Hyun‐Joo , Chun Hye‐Yeong , Song In‐Sun
Published: April 2009

The ray‐based spectral parameterization of convective gravity wave drag, which explicitly calculates the gravity wave propagation properties, is validated against the Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite (UARS). Offline calculations of the ray‐based parameterization are performed using global reanalysis data and gravity wave temperature variances calculated from the parameterization are compared with those measured from the MLS. The parameterized temperature variances are calculated from gravity wave packets that are visible from the MLS to allow for comparison. The MLS visibility is analytically obtained using the three‐dimensional MLS filter function. Comparisons between the parameterization calculations and MLS measurements show that both the magnitude and spatial distribution of the MLS‐filtered temperature variances in the ray‐based parameterization are in good agreement with observations. However, the MLS‐filtered temperature variances are found to be sensitive to the source‐level wave propagation direction, which, until now, has been regarded as a free parameter in the ray‐based parameterization. This result indicates that the wave propagation direction can be crucial for more realistic parameterization of gravity wave (GW) effects and thus needs to be reasonably determined. Comparisons between the ray‐based parameterization and columnar parameterization, which considers the gravity wave propagation only in the vertical direction, are also made in terms of temperature variance, and both results, after filtered, are similar to MLS observations. However, the magnitude of the unfiltered temperature variance in the equatorial regions with weak MLS visibility is smaller in the ray‐based parameterization than in the columnar parameterization.
Reduction of nitrate in Shewanella oneidensis depends on atypical NAP and NRF systems with NapB as a preferred electron transport protein from CymA to NapA
Authors: Gao Haichun , Yang Zamin K , Barua Soumitra , Reed Samantha B , Romine Margaret F , Nealson Kenneth H , Fredrickson James K , Tiedje James M , Zhou Jizhong
Published: April 2009

In the genome of Shewanella oneidensis, a napDAGHB gene cluster encoding periplasmic nitrate reductase (NapA) and accessory proteins and an nrfA gene encoding periplasmic nitrite reductase (NrfA) have been identified. These two systems seem to be atypical because the genome lacks genes encoding cytoplasmic membrane electron transport proteins, NapC for NAP and NrfBCD/NrfH for NRF, respectively. Here, we present evidence that reduction of nitrate to ammonium in S. oneidensis is carried out by these atypical systems in a two-step manner. Transcriptional and mutational analyses suggest that CymA, a cytoplasmic membrane electron transport protein, is likely to be the functional replacement of both NapC and NrfH in S. oneidensis. Surprisingly, a strain devoid of napB encoding the small subunit of nitrate reductase exhibited the maximum cell density sooner than the wild type. Further characterization of this strain showed that nitrite was not detected as a free intermediate in its culture and NapB provides a fitness gain for S. oneidensis to compete for nitrate in the environments. On the basis results from mutational analyses of napA, napB, nrfA and napBnrfA in-frame deletion mutants, we propose that NapB is able to favor nitrate reduction by routing electrons to NapA exclusively.
IMGT/Automat: the strategy for the annotation of human and mouse cDNA nucleotide sequences of IG and TR
Authors: Folch Géraldine , Jabado-Michaloud Joumana , Bellahcene Fatena , Regnier Laetitia , Giudicelli Véronique , Lefranc Marie-Paule
Published: April 2009

The cDNA sequences of immunoglobulins (IG) and T cell receptors (TR) represent more than one half of the sequences in the IMGT^®^ nucleotide database IMGT/LIGM-DB^1^ and 75% of them are from human and mouse. A few cDNA are germline but the great majority results from a V-D-J or V-J gene rearrangement, spliced to a C gene. The IG and TR genes have been studied extensively in IMGT^®^ ("http://www.imgt.org":http://www.imgt.org) ^2^, which allowed to set up their nomenclature and the corresponding germline reference sequences. These standardized reference directory sets (one for each group of each locus) and the IMGT-ONTOLOGY axioms and derived concepts^3^ are the key elements indispensable to perform the annotation of IG and TR cDNA sequences. A Java program, IMGT/Automat^4^, was developed by IMGT^®^, to automatically annotate the IG and TR cDNA sequences and to produce a totally automatic and complete annotation. More than 9,000 human and mouse cDNA have already been successfully automatically annotated. The quality of the cDNA automatic annotation is equivalent to the quality of the annotation achieved by a human expert. The IMGT^®^ strategy is currently the only way, in the field of immunogenetics, to guarantee the annotation quality and the management of an always increasing number of IG and TR cDNA nucleotide sequences.
Low or Moderate Dietary Energy Restriction for Long‐term Weight Loss: What Works Best?
Authors: Das Sai Krupa , Saltzman Edward , Gilhooly Cheryl H. , DeLany James P. , Golden Julie K. , Pittas Anastassios G. , Dallal Gerard E. , Bhapkar Manjushri V. , Fuss Paul J. , Dutta Chhanda , McCrory Megan A. , Roberts Susan B.
Published: April 2009

Theoretical calculations suggest that small daily reductions in energy intake can cumulatively lead to substantial weight loss, but experimental data to support these calculations are lacking. We conducted a 1‐year randomized controlled pilot study of low (10%) or moderate (30%) energy restriction (ER) with diets differing in glycemic load in 38 overweight adults (mean ± s.d., age 35 ± 6 years; BMI 27.6 ± 1.4 kg/m2). Food was provided for 6 months and self‐selected for 6 additional months. Measurements included body weight, resting metabolic rate (RMR), adherence to the ER prescription assessed using 2H218O, satiety, and eating behavior variables. The 10%ER group consumed significantly less energy (by 2H218O) than prescribed over 12 months (18.1 ± 9.8%ER, P = 0.04), while the 30%ER group consumed significantly more (23.1 ± 8.7%ER, P < 0.001). Changes in body weight, satiety, and other variables were not significantly different between groups. However, during self‐selected eating (6–12 months) variability in % weight change was significantly greater in the 10%ER group (P < 0.001) and poorer weight outcome on 10%ER was predicted by higher baseline BMI and greater disinhibition (P < 0.0001; adj R2 = 0.71). Weight loss at 12 months was not significantly different between groups prescribed 10 or 30%ER, supporting the efficacy of low ER recommendations. However, long‐term weight change was more variable on 10%ER and weight change in this group was predicted by body size and eating behavior. These preliminary results indicate beneficial effects of low‐level ER for some but not all individuals in a weight control program, and suggest testable approaches for optimizing dieting success based on individualizing prescribed level of ER.
Periodic density functional theory studies of Li-doped polythiophene: Dependence of electronic and structural properties on dopant concentration
Authors: Ramírez-Solís A. , Kirtman B. , Bernal-Jáquez R. , Zicovich-Wilson C. M.
Published: April 2009

We report periodic B3LYP∕6-31G** density functional theory calculations on Li-doped polythiophene at various dopant concentrations using (SC4H2)mLi2 unit cells for m=2, 6, and 10. Uniform doping by Li atoms and by pairs of Li atoms on adjacent thiophene rings are considered with the primary aim of comparing polaron versus bipolaron properties. Properties examined include geometries, charge distributions, polaron/bipolaron formation energies, dopant binding energies, band structures, and densities of states.
Ion implantation and SiC transistor performance
Authors: Gurfinkel M. , Potbhare S. , Xiong H. D. , Suehle J. S. , Shapira Yoram , Lelis A. J. , Habersat D. , Goldsman N.
Published: April 2009

SiC metal oxide semiconductor field effect transistors grown on low-doped epilayer channels and on ion-implanted channels with either “as grown” or NO annealed thermal oxides have been electrically characterized. The threshold voltage, effective electron mobility, as well as fixed charge, oxide trap, and interface trap concentrations have been separately obtained using conventional dc sweep, capacitance-voltage (C-V), fast current-voltage (I-V), and low frequency noise measurements. The results show that devices with as grown SiO2 have a much higher density of “slow” bulk oxide traps than devices after postoxidation annealing in NO. The oxide fixed charge density is unaffected by the annealing process. Devices fabricated on ion-implanted channels exhibit only a small increase in the slow bulk oxide trap density and the fixed charge. However, the density of the “fast” interface traps increases dramatically. This suggests that the damage due to the ion-implantation process is mainly interfacial. In contrast to Si devices, this ion-implantation damage is not completely repaired even after annealing.
Improved atomistic damage generation model for binary collision simulations
Authors: Santos Iván , Marqués Luis A. , Pelaz Lourdes , López Pedro
Published: April 2009

We have carried out a classical molecular dynamics study to quantify the conditions under which damage is generated by ion implantation in silicon at energies below the displacement threshold. The obtained results have been used to construct a general framework for damage generation which captures the transition from ballistic (high above the displacement threshold) to thermal (around and below the displacement threshold) regime. The model, implemented in a binary collision code, has been successfully used to simulate monatomic and especially molecular implantations, where nonlinear effects occur. It reproduces the amount and morphology of generated damage at atomic level in good agreement with classical molecular dynamics simulations but with a computational gain factor of ∼103 to ∼104. The incorporation of this damage model to process simulators will improve the prediction of amorphization conditions and provide a convenient tool for simulating molecular implants not available to date. Although this work has been focused on silicon, the model can be applied with appropriate calibration to other materials where the thermal regime of damage generation plays an important role.
Analysis and optimisation of microcrystalline silicon solar cells with periodic sinusoidal textured interfaces by two-dimensional optical simulations
Authors: Čampa Andrej , Krč Janez , Topič Marko
Published: April 2009

Two-dimensional optical model for simulation of thin-film solar cells with periodical textured interfaces is presented. The model is based on finite element method and uses triangular discrete elements for the structure description. The advantages of the model in comparison to other existing models are highlighted. After validation and verification of the developed simulator, simulations of a microcrystalline silicon solar cell with a sinusoidal grating texture applied to the interfaces are carried out. The analysis and optimization of the two grating parameters—period and height of the grooves—are performed with respect to the maximal short-circuit current density of the cell. Up to 45% increase in the current density is identified for the optimized structure, compared to that of the cell with flat interfaces. Optical losses in the periodically textured silver back reflector are determined.
Probing chiral solute-water hydrogen bonding networks by chirality transfer effects: A vibrational circular dichroism study of glycidol in water
Authors: Yang Guochun , Xu Yunjie
Published: April 2009

Vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra of (S)-(−)-glycidol were measured in water with a concentration of 6.0M in the 1000–1750 cm−1 region. Prominent and complex VCD spectral features were detected at the water bending vibrational region. Our experimental results show that water molecules can become optically active through hydrogen bonding interactions with glycidol molecules. To model the glycidol-water hydrogen bonding network in the solution, molecular dynamics simulations using the AMBER9 suite of programs were carried out. Altogether, 34 conformers of the small glycidol-(water)N clusters with N=1, 2, 3, and 4 were considered. Geometry optimizations, harmonic frequency calculations, and the VA and VCD intensity predictions of these small glycidol-water clusters were performed at the B3LYP/6-311++G(d,p) level of theory using the GAUSSIAN 03 program package. Strong cooperative hydrogen bonding effects were detected in the larger glycidol-(water)N clusters. The population weighted VA and VCD spectra of each N group of glycidol (water)N=1,2,3,4 were used to produce the simulated VA and VCD spectra, which are in good agreement with the experimental VA and VCD spectra. The study shows that all these clusters make important contributions to the observed spectra and are the most important species in the aqueous solution with complicated equilibriums among them.
Open-shell molecular electronic states from the parametric two-electron reduced-density-matrix method
Authors: DePrince A. Eugene , Mazziotti David A.
Published: April 2009

The parametric variational two-electron reduced-density-matrix (2-RDM) method, developed from an analysis of positivity (N-representability) constraints on the 2-RDM, is extended to treat both closed- and open-shell molecules in singlet, doublet, and triplet spin states. The parametric 2-RDM method can be viewed as using N-representability conditions to modify the 2-RDM from a configuration interaction singles-doubles wave function to make the energy size extensive while keeping the 2-RDM approximately N-representable [J. Kollmar, Chem. Phys. 125, 084108 (2006); A. E. DePrince and D. A. Mazziotti, Phys. Rev. A 76, 049903 (2007)]. Vertical excitation energies between triplet and singlet states are computed in a polarized valence triple-zeta basis set. In comparison to traditional single-reference wave function methods, the parametric 2-RDM method recovers a larger percentage of the multireference correlation in the singlet excited states, which improves the accuracy of the vertical excitation energies. Furthermore, we show that molecular geometry optimization within the parametric 2-RDM method can be efficiently performed through a Hellmann–Feynman-like relation for the energy gradient with respect to nuclear coordinates. Both the open-shell extension and the energy-gradient relation are applied to computing relative energies and barrier heights for the isomerization reaction HCN+↔HNC+. The computed 2-RDMs very nearly satisfy well known, necessary N-representability conditions.
Formation of lamellar structures from spherical particles
Authors: Li Zhidong , Wu Jianzhong
Published: April 2009

We report disorder to lamellar transition in a system of spherically symmetric particles where the interparticle potential consists of a short-ranged attraction and a longer-ranged repulsion. The system provides a simplified model for aqueous dispersions of colloidal particles and globular proteins that may exhibit stable/metastable clusters or microscopic phases. By using a non-mean-field density functional theory, we predict that under appropriate conditions, a lamellar phase with alternating condensed and dilute layers of particles is thermodynamically more stable than a uniform disordered phase at the same temperature and molecular number density. Formation of the lamellar structure may prohibit the macroscopic fluid-fluid phase transition. At a given condition, the width of the condensed lamellar layers increases with the overall particle density but the trend is opposite for the dilute lamellar layers. A minimal lamellar periodicity is obtained when the condensed and dilute layers have approximately the same thickness.
Model of a source-driven plasma interacting with a wall in an oblique magnetic field
Authors: Ahedo E. , Carralero D.
Published: April 2009

A fluid model of a magnetized source-driven plasma is discussed for regimes with (Debye length)⪡(ion Larmor radius)⪡(plasma size and collisional mean-free path). Plasma collection by the wall is determined in terms of angle of incidence, magnetic strength, and plasma collisionality. For nonparallel incidence, a three-scale asymptotic analysis reveals a three-region matched structure consisting of a magnetically aligned bulk region, the Chodura layer, and the Debye sheath. Sonic Chodura and Bohm conditions define the singular region transitions. For near-parallel incidence, a separate analysis demonstrates the presence of a diffusive-collisional bulk region followed by a thin collisionless layer, which differs partially from the Chodura layer. A parametric analysis unveils the presence of four regimes depending on plasma collisionality: (1) a collisionless regime, with the magnetically channeled bulk region governed by plasma production; (2) a resistive semicollisional regime, where collisions retard the plasma transport in the bulk region; (3) a diffusive semicollisional regime, where the E×B drift dominates the ion flux in the bulk region; and (4) a collisional regime, where collisions cancel out magnetic effects. At grazing incidence, plasma collection is found to vary nonmonotonically with plasma collisionality. Nonzero Debye-length effects are discussed briefly.