bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic responses of sunspots to their ambient magnetic configuration
Authors: Bagare S. P.
Published: August 2011

In our earlier study of a revisit of the classic Wilson Effect, it was found that a large proportion of sunspots do not display the geometric effect which is ascribed to a depression of the umbra. It was shown that the presence or absence of the effect, observed close to the limb, depends upon the ambient magnetic configuration of the sunspot. In this follow up study, we look for the impact of changes in ambient magnetic configuration on the measurable properties of sunspots during their disk passage, using observations obtained at the Kodaikanal observatory during 1978-80. Digitized photoheliogram data were used to examine and measure areas of spots and their umbrae for 101 cases. Magnetic field measures published by the Academy of sciences, Leningrad were used to evaluate the ambient magnetic configuration. The results indicate that the extent of magnetic bipolarity is associated with changes in the proportion of the area of the penumbra to that of the umbra. In regular spots, the relative area of penumbra reduces with reduction in the strength of ambient opposite polarity spots and pores. However, in the presence of pore sized blob(s) in penumbra, and with associated emerging fluxes, the penumbra is significantly enlarged. But in the presence of a light bridge or a split umbra, the relative area of penumbra is considerably reduced.
Sunspot temperatures from red and blue photometry
Authors: Chapman G. A. , Cookson A. M. , Preminger D. G.
Published: August 2011

Photometric images are used to measure the temperature of sunspots at different wavelengths. Images at 672.3 nm and 472.3 nm are obtained at the San Fernando Observatory using the CFDT2 (2.5” x 2.5” pixels). Images at 607.1 nm and 409.4 nm are obtained by the PSPT at Mauna Loa Observatory. Monochromatic intensities are converted to temperatures as in Steinegger et al (1990). The pixel by pixel temperature for a sunspot is converted into a bolometric contrast for that sunspot according to Chapman et al (1994). Sunspot temperatures, i.e., their bolometric contrasts, are calculated from both red (672.3 nm) and blue wavelengths (472.3 nm) and compared.
A filament supported by different magnetic field configurations
Authors: Guo Y. , Schmieder B. , Démoulin P. , Wiegelmann T. , Aulanier G. , Török T. , Bommier V.
Published: August 2011

A nonlinear force-free magnetic field extrapolation of vector magnetogram data obtained by THEMIS/MTR on 2005 May 27 suggests the simultaneous existence of different magnetic configurations within one active region filament: one part of the filament is supported by field line dips within a flux rope, while the other part is located in dips within an arcade structure. Although the axial field chirality (dextral) and the magnetic helicity (negative) are the same along the whole filament, the chiralities of the filament barbs at different sections are opposite, i.e., right-bearing in the flux rope part and left-bearing in the arcade part. This argues against past suggestions that different barb chiralities imply different signs of helicity of the underlying magnetic field. This new finding about the chirality of filaments will be useful to associate eruptive filaments and magnetic cloud using the helicity parameter in the Space Weather Science.
The solar active region magnetic field and energetics
Authors: Hu Qiang , Deng Na , Choudhary Debi P. , Dasgupta B. , Su Jiangtao
Published: August 2011

Motivated by increasingly more advanced solar observations, we recently develop a method of coronal magnetic field extrapolation, especially for an active region (sunspot region). Based on a more complex variational principle, the principle of minimum (energy) dissipation rate (MDR), we adopt and solve a more complex equation governing the coronal magnetic field that is non-force-free in general. We employ the vector magnetograms from multiple instruments, including Hinode, NSO, and HSOS, and particularly observations at both photospheric and chromospheric levels for one active region. We discuss our results in the context of quantitative characterization of active region magnetic energy and magnetic topology. These quantitative analyses aid in better understanding and developing prediction capability of the solar activity that is largely driven by the solar magnetic field.
How reliable are observations of solar magnetic fields? Comparison of full-disk measurements in different spectral lines and calibration issues of space missions SOHO, Hinode, and SDO
Authors: Demidov Mikhail
Published: August 2011

An urgent problem in modern solar physics, which is not completely solved up to now, is to obtain realistic magnetic field strength values from parameters measured magnetographs or Stokes-meter instruments. One of the important tools on this way is a comparison of observations made in different spectral lines with the same or with the different telescopes. This issue is an actual task in the analysis of the new data sets provided by the space missions SOHO and Hinode, which measurements are available for several years already, and SDO, which data appeared recently. The main aim of this study is a cross-comparison of magnetic field observations made in different spectral lines used on the above mentioned space observatories: Ni i λ676.77 nm (SOHO/MDI), Fe i λ630.152 nm and Fe i λ630.25 nm (Hinode/SP), and Fe i λ617.33 nm (SDO/HMI). Full-disk high-precision Stokes-meter measurements with the STOP telescope at the Sayan observatory in these lines are used basically, as well as some observations in other spectral lines having a great diagnostic impact, such as Fe i λ525.02 nm, Fe i λ523.29 nm and Fe i λ532.42 nm. The difference between one-instrument (STOP) simultaneous or quasi-simultaneous observations in different spectral lines do not exceed the factor of 2-3 depending on the combination of spectral lines and the position on the solar disk. This is significantly less than in some other studies devoted to cross-comparison of different data sets. Importance and consequences of the obtained results are discussed.
Helioseismic probing of the subsurface structure of sunspots
Authors: Crouch A.D. , Birch A.C. , Braun D.C. , Clack C.T.M.
Published: August 2011

We discuss recent progress in the helioseismic probing of the subsurface structure of solar magnetic regions. To simulate the interaction of helioseismic waves with magnetic fields and thermal perturbations we use a simple model that is translation invariant in the horizontal directions, has a realistic stratification in the vertical direction, and has physically consistent boundary conditions for the waves at the upper and lower boundaries of the computational domain. Using this model we generate synthetic helioseismic data and subsequently measure time-distance travel times. We evaluate a model for the wave-speed perturbation below sunspots that replaces the sound speed in a non-magnetic model by the fast-mode speed from a magnetic model; our results indicate that this approach is unlikely to be useful in modeling wave-speed perturbations in sunspots. We develop and test an inversion algorithm for inferring the sound-speed perturbation in magnetic regions. We show that this algorithm retrieves the correct sound-speed perturbation only when the sensitivity kernels employed account for the effects of the magnetic field on the waves and the subsurface structure.
Temporal changes in the frequencies of the solar p-mode oscillations during solar cycle 23
Authors: Rhodes E J , Reiter J , Schou J , Larson T , Scherrer P , Brooks J , McFaddin P , Miller B , Rodriguez J , Yoo J
Published: August 2011

We present a study of the temporal changes in the sensitivities of the frequencies of the solar p-mode oscillations to corresponding changes in the levels of solar activity during Solar Cycle 23. From MDI and GONG++ full-disk Dopplergram three-day time series obtained between 1996 and 2008 we have computed a total of 221 sets of m-averaged power spectra for spherical harmonic degrees ranging up to 1000. We have then fit these 284 sets of m-averaged power spectra using our WMLTP fitting code and both symmetric Lorentzian profiles for the peaks as well as the asymmetric profile of Nigam and Kosovichev to obtain 568 tables of p-mode parameters. We then inter-compared these 568 tables, and we performed linear regression analyses of the differences in p-mode frequencies, widths, amplitudes, and asymmetries as functions of the differences in as many as ten different solar activity indices. From the linear regression analyses that we performed on the frequency difference data sets, we have discovered a new signature of the frequency shifts of the p-modes. Specifically, we have discovered that the temporal shifts of the solar oscillation frequencies are positively correlated with the changes in solar activity below a limiting frequency. They then become anti-correlated with the changes in activity for a range of frequencies before once again becoming positively-correlated with the activity changes at very high frequencies. We have also discovered that the two frequencies where the sensitivities of the temporal frequency shifts change sign also change in phase with the average level of solar activity.
Signature of collision of magnetic flux tubes in the quiet solar photosphere
Authors: Andic Aleksandra
Published: August 2011

Collision of the magnetic flux tubes in the Quiet Sun was proposed as one of the possible sources for the heating of the solar atmosphere (Furusawa and Sakai, 2000). The solar photosphere was observed using the New Solar Telescope ad Big Bear Solar Observatory. In TiO spectral line at 705.68 nm we approached resolution of 0.1″. The horizontal plasma wave was observed spreading from the larger bright point. Shorty after this wave an increase in the oscillatory power appeared at the same location as the observed bright point. This behavior matches some of the results from the simulation of the collision of the two flux tubes with a weak current.
Chromosphere above sunspots as seen at millimeter wavelengths
Authors: Loukitcheva Maria A. , Solanki Sami K. , White Stephen M.
Published: August 2011

Millimeter emission is known to be a sensitive diagnostic of temperature and density in the solar chromosphere. In this work we use millimeter wave data to distinguish between various atmospheric models of sunspots, whose temperature structure in the upper photosphere and chromosphere has been the source of some controversy. From mm brightness simulations we expect a radio umbra to change its appearance from dark to bright (compared to the Quiet Sun) at a given wavelength in the millimeter spectrum (depending on the exact temperature in the model used). Thereby the millimeter brightness observed above an umbra at several wavelengths imposes strong constraints on temperature and density stratification of the sunspot atmosphere, in particular on the location and depth of the temperature minimum and the location of the transition region. Current mm/submm observational data suggest that brightness observed at short wavelengths is unexpectedly low compared to the most widely used sunspot models such as of Maltby et al. (1986). A successful model that is in agreement with millimeter umbral brightness should have an extended and deep temperature minimum (below 3000 K), such as in the models of Severino et al. (1994). However, we are not able to resolve the umbra cleanly with the presently available observations and better resolution as well as better wavelength coverage are needed for accurate diagnostics of umbral brightness at millimeter wavelengths. This adds one more scientific objective for the Atacama Large Millimeter/Submillimeter Array (ALMA).
Study of sunspot motion and flow fields associated with solar flares
Authors: Wang Shuo , Liu Chang , Wang Haimin
Published: August 2011

Evolution of sunspot structure and photospheric magnetic fields are important to understand how the flare energy is built up and released. With high-resolution optical data, it is possible to examine in details the optical flows of the photosphere and their relationship to the flaring process. Using G-band and Stokes-V data obtained with Hinode Solar Optical Telescope (SOT), we study the sunspot motion and flow fields associated with the 2006 December 13 X3.4 flare in NOAA AR 10930. We calculate the centroids of the delta spot umbrae lying in opposite magnetic polarities, and use two different methods to derive the photospheric flow fields of the AR. We find that the shearing motion before the flare changes to unshearing motion associated with the eruption. A decrease of average velocity of shear flow is found to be associated with the flare, with a magnitude of 0.2 km s−1.

As a related study, we also test implementing the recently developed differential affine velocity estimator for vector magnetograms (DAVE4VM; Schuck, P. W 2008) technique for the magnetic field observations obtained by the Big Bear Solar Observatory (BBSO) and Helioseismic Magnetic Imager (HMI) on board the Solar Dynamic Observatory (SDO). Using this method to analyze changes of active region magnetic fields associated with flares may shed new light on the cause and effect of flaring process.
Study of the change of surface magnetic field associated with flares
Authors: Li Yixuan , Jing Ju , Fan Yuhong , Wang Haimin
Published: August 2011

How magnetic field structure changes with eruptive events (e.g., flares and CMEs) has been a long-standing problem in solar physics. Here we present the analysis of eruption-associated changes in the magnetic inclination angle, the transverse component of magnetic field and the Lorentz force. The analysis is based on an observation of the X3.4 flare on Dec.13 2006 and a numerical simulation of a solar eruption made by Yuhong Fan. Both observation and simulation show that (1) the magnetic inclination angle in the decayed peripheral penumbra increases, while that in the central area close to flaring polarity inversion line (PIL) deceases after the flare; (2) the transverse component of magnetic field increases at the lower altitude near flaring PIL after the flare. The result suggests that the field lines at flaring neutral line turn to more horizontal near the surface, that is in agreement with the prediction of Hudson, Fisher & Welsch (2008).
Comparison of numerical simulations and observations of helioseismic MHD waves in sunspots
Authors: Parchevsky K. V. , Zhao J. , Kosovichev A. G. , Rempel M.
Published: August 2011

Numerical 3D simulations of MHD waves in magnetized regions with background flows are very important for the understanding of propagation and transformation of waves in sunspots. Such simulations provide artificial data for testing and calibration of helioseismic techniques used for analysis of data from space missions SOHO/MDI, SDO/HMI, and HINODE. We compare with helioseismic observations results of numerical simulations of MHD waves in different models of sunspots. The simulations of waves excited by a localized source provide a detailed picture of the interaction of the MHD waves with the magnetic field and background flows (deformation of the waveform, wave transformation, amplitude variations and anisotropy). The observed cross-covariance function represents an effective Green's function of helioseismic waves. As an initial step, we compare it with simulations of waves generated by a localized source. More thorough analysis implies using multiple sources and comparison of the observed and simulated cross-covariance functions. We plan to do such calculations in the nearest future. Both, the simulations and observations show that the wavefront inside the sunspot travels ahead of a reference “quiet Sun” wavefront, when the wave enters the sunspot. However, when the wave passes the sunspot, the time lag between the wavefronts becomes unnoticeable.
Are the umbral dots, penumbral grains, and G band bright points formed by the same type of magnetic flux tubes?
Authors: Sattarov Isroil
Published: August 2011

Today's Solar Physics comes across of different type of fine structures in solar atmosphere including umbral dots and penumbral grains in sunspots, and G-band bright points in quiet Sun. In this report, we present evidence that umbral dots, penumbral grains, and, possibly, G band bright points are related to a common type of features in solar atmosphere magnetic flux tubes.
Possible explanations of the Maunder minimum from a flux transport dynamo model
Authors: Karak Bidya Binay , Choudhuri Arnab Rai
Published: August 2011

We propose that at the beginning of the Maunder minimum the poloidal field or amplitude of meridional circulation or both fell abruptly to low values. With this proposition, a flux transport dynamo model is able to reproduce various important aspects of the historical records of the Maunder minimum remarkably well.
Evidence for the return meridional flow in the convection zone from latitude motions of sunspots
Authors: Sivaraman K.R. , Sivaraman H. , Gupta S.S. , Howard R.F.
Published: August 2011

We have derived the latitude motions of sunspots classified into three area categories using the measures of positions and areas of their umbrae from the white – light images of the Sun for the period 1906 – 1987 from the Kodaikanal Observatory archives. The latitude motions are directed equator – ward in all the three area classes. We interpret that these equator – ward latitude motions reflect the meridional flows at the three depths in the convection zone where the magnetic flux loops of the spots of the three area classes are anchored. We obtain estimates of the anchor depths through a comparison of the rotation rates of the spots in each area class with the rotation rate profiles from helioseismic inversions. The equator – ward flows measured by us thus provide evidence of the return meridional flows in the convection zone as required in the flux transport solar dynamo models. We have done an identical analysis using a similar data set derived from the photoheliogram collections of the Mt.Wilson Observatory for the period 1917 – 1985. There is good agreement between the results from the data sets of the two observatories.
Excitation of magneto-acoustic waves in network magnetic elements
Authors: Kato Yoshiaki , Steiner Oskar , Steffen Matthias , Suematsu Yoshinori
Published: August 2011

From radiation magnetohydrodynamic (RMHD) simulations we track the temporal evolution of a vertical magnetic flux sheet embedded in a two-dimensional non-stationary atmosphere that reaches all the way from the upper convection zone to the low chromosphere. Examining its temporal behavior near the interface between the convection zone and the photosphere, we describe the excitation of propagating longitudinal waves within the magnetic element as a result of convective motion in its surroundings.
Solar flare forecasting using sunspot-groups classification and photospheric magnetic parameters
Authors: Yuan Yuan , Shih Frank Y. , Jing Ju , Wang Haimin
Published: August 2011

In this paper, we investigate whether incorporating sunspot-groups classification information would further improve the performance of our previous logistic regression based solar flare forecasting method, which uses only line-of-sight photospheric magnetic parameters. A dataset containing 4913 samples from the year 2000 to 2005 is constructed, in which 2721 samples from the year 2000, 2002 and 2004 are used as a training set, and the remaining 2192 samples from the year 2001, 2003 and 2005 are used as a testing set. Experimental results show that sunspot-groups classification combined with total gradient on the strong gradient polarity neutral line achieve the highest forecasting accuracy and thus it testifies sunspot-groups classification does help in solar flare forecasting.
Optical polarimetry and photometry of young sun-like star LO Peg
Authors: Pandey J. C. , Medhi B. J. , Sagar R.
Published: August 2011

We have carried out the B,V and R-band polarimetric and V-band photometric study of the star LO Peg. Our analysis reveal that LO Peg is highly polarized among the sun-like stars. The degree of polarization and polarization position angle are found to be rotationally modulated. The levels of polarization observed in LO Peg could be the result of scattering of an anisotropic stellar radiation field by an optically thin circumstellar envelope or scattering of the stellar radiation by prominence-like structures. The long term photometric observations of LO Peg indicate three independent groups of spots are present on the surface of LO Peg.
Surface evolution in stable magnetic fields: the case of the fully convective dwarf V374 Peg
Authors: Vida K. , Oláh K. , Kővári Zs.
Published: August 2011

We present BV(RI)C photometric measurements of the dM4-type V374 Peg covering ~430 days. The star has a mass of ~0.28MSun, so it is supposed to be fully convective. Previous observations detected almost-rigid-body rotation and stable, axisymmetric poloidal magnetic field. Our photometric data agree well with this picture, one persistent active nest is found on the stellar surface. Nevertheless, the surface is not static: night-to-night variations and frequent flaring are observed. The flares seem to be concentrated on the brighter part of the surface. The short-time changes of the light curve could indicate emerging flux ropes in the same region, resembling to the active nests on the Sun. We have observed flaring and quiet states of V374 Peg changing on monthly timescale.
A nonlinear model for rotating cool stars
Authors: Barnes Sydney A.
Published: August 2011

A simple nonlinear model is introduced here to describe the rotational evolution of main sequence cool (FGKM) stars. It is formulated only in terms of the ratio of a star's rotation period, P, to its convective turnover timescale, τ, and two dimensionless constants which are specified using solar- and open cluster data. The model explains the origin of the two sequences, C/fast and I/slow, of rotating stars observed in open cluster color-period diagrams, and describes their evolution from C-type to I-type through the rotational gap, g, separating them. It explains why intermediate-mass open cluster stars have the longest periods, while higher- and lower-mass cool stars have shorter periods. It provides an exact expression for the age of a rotating cool star in terms of P and τ, thereby generalizing gyrochronology. The possible range of initial periods is shown to contribute upto 128 Myr to the gyro age errors of solar mass field stars. A transformation to color-period space shows how this model explains some detailed features in the color-period diagrams of open clusters, including the shapes and widths of the sequences, and the observed number density of stars across these diagrams.
Laboratory simulation of solar magnetic flux rope eruptions
Authors: Tripathi S. K. P. , Gekelman W.
Published: August 2011

A laboratory plasma experiment has been constructed to simulate the eruption of arched magnetic flux ropes (AMFRs e.g., coronal loops, solar prominences) in an ambient magnetized plasma. The laboratory AMFR is produced using an annular hot LaB6 cathode and an annular anode in a vacuum chamber which has additional electrodes to produce the ambient magnetized plasma. Two laser beams strike movable carbon targets placed behind the annular electrodes to generate controlled plasma flows from the AMFR footpoints that drives the AMFR eruption. The experiment operates with a 0.5 Hz repetition rate and is highly reproducible. Thus, time evolution of the AMFR is recorded in three-dimensions with high spatio-temporal resolutions using movable diagnostic probes. Experimental results demonstrate outward expansion of the AMFR, release of its plasma to the background, and excitation of fast magnetosonic waves during the eruption.
Burnout and psychiatrists: what do we know and where to from here?
Authors: Kumar S.
Published: August 2011

Medicine in most parts of the world is becoming a stressful profession. Psychiatrists represent a high-risk group among doctors for experiencing burnout, alcohol and drug use, posing suicide risk and other forms of work-related stress. There are reports that entrants in the profession of psychiatrists are decreasing globally. Conceptual issues related to burnout are explored and factors contributing to burnout in psychiatrists are reviewed. Methodologically sound studies are needed to help us understand positive aspects of psychiatry as a profession and the environment psychiatrists work in. Effective treatment programmes for burnout are also needed not only to reduce suffering but also to retain psychiatrists in the profession.
Climate, soil, and vegetation controls on the temporal variability of vadose zone transport
Authors: Harman C. J. , Rao P. S. C. , Basu N. B. , McGrath G. S. , Kumar P. , Sivapalan M.
Published: August 2011

Temporal patterns of solute transport and transformation through the vadose zone are driven by the stochastic variability of water fluxes. This is determined by the hydrologic filtering of precipitation variability into infiltration, storage, drainage, and evapotranspiration. In this work we develop a framework for examining the role of the hydrologic filtering and, in particular, the effect of evapotranspiration in determining the travel time and delivery of sorbing, reacting solutes transported through the vadose zone by stochastic rainfall events. We describe a 1‐D vertical model in which solute pulses are tracked as point loads transported to depth by a series of discrete infiltration events. Numerical solutions of this model compare well to the Richards equation–based HYDRUS model for some typical cases. We then utilize existing theory of the stochastic dynamics of soil water to derive analytical and semianalytical expressions for the probability density functions (pdf's) of solute travel time and delivery. The moments of these pdf's directly relate the mean and variance of expected travel times to the water balance and show how evapotranspiration tends to reduce (and make more uncertain) the mass of a degrading solute delivered to the base of the vadose zone. The framework suggests a classification of different modes hydrologic filtering depending on hydroclimatic and landscape controls. Results suggest that variability in travel times decreases with soil depth in wet climates but increases with soil depth in dry climates. In dry climates, rare large storms can be an important mechanism for leaching to groundwater.
Automatic recognition of complex magnetic regions on the Sun in GONG magnetogram images and prediction of flares: Techniques for the flare warning program Flarecast
Authors: Steward Graham A. , Lobzin Vasili V. , Wilkinson Phil J. , Cairns Iver H. , Robinson Peter A.
Published: August 2011

In the present paper, Global Oscillation Network Group (GONG) solar magnetograms are used to automatically identify active regions by thresholding the line‐of‐sight component of the solar magnetic field. The flare potential of the regions is predicted by locating strong‐gradient polarity inversion lines (SPILs) and estimating their parameters. The parameters of interest are the length of the SPIL, a proxy for its curvature; the maximum west‐east and south‐north gradients of the magnetic field in its vicinity; and a sum of the magnetic field gradients, the summation being performed along the SPIL. Analysis for thresholding of one, two, and three parameters and the corresponding probabilities for correct prediction of flares are presented and compared. The probability for correct prediction of X‐ray flares of class C or greater in a 24 h window exceeds 88%, while the probability of false alarms is less than 10% if the decision rule involves thresholding of three specific parameters. These parameters are the steepest south‐north gradient of the magnetic field, the maximum curvature of the SPILs, and the length of the longest SPIL, all being calculated for the entire region rather than for a particular SPIL. The steepest south‐north gradient of the magnetic field is also used to estimate the probabilities for a flare to belong to classes C, M, or X. These techniques are now implemented in the flare warning program Flarecast. The first automatically predicted M‐ and X‐class flares are presented, and Flarecast is found to predict well the observed X‐ray flares.
Modeling colloid transport and retention in saturated porous media under unfavorable attachment conditions
Authors: Bradford Scott A. , Torkzaban Saeed , Simunek Jiri
Published: August 2011

A mathematical model is presented for colloid transport and retention in saturated porous media under unfavorable attachment conditions. The model accounts for colloid transport in the bulk aqueous phase and adjacent to the solid surface, and rates of colloid collision, interaction, release, and immobilization on the solid phase. Model parameters were estimated using (1) filtration theory; (2) calculated interaction energies in conjunction with the Maxwellian kinetic energy model of diffusion; (3) information about the velocity magnitude and distribution adjacent to the solid phase that was obtained from pore scale water flow simulations; (4) colloid and collector sizes; (5) the balance of applied hydrodynamic and resisting adhesive torques; and (6) time dependent filling of retention locations using a Langmuirian approach. The presented theory constrains the model parameters and output to physically realistic values in many instances, and minimizes the need for parameter optimization. Example simulations demonstrate that our modeling formulation is qualitatively consistent with observed trends for retention with colloid size and concentration, grain size, and velocity for many systems. The model provides a clear conceptual explanation for the causes of hyperexponential, exponential, uniform, and nonmonotonic retention profiles without invoking hypotheses with regard to colloid heterogeneity, aggregation, or multiple deposition rates. Furthermore, the model formulation and research presented herein helps to identify areas where additional research and theory development are still needed.
Independent localization of MAP2, CaMKIIα and β‐actin RNAs in low copy numbers
Authors: Mikl Martin , Vendra Georgia , Kiebler Michael A
Published: August 2011

Messenger RNA localization involves the assembly of ribonucleoprotein particles (RNPs) and their subsequent transport along the cytoskeleton to their final destination. Here, we provide new evidence that microtubule‐associated protein 2 (MAP2), calcium/calmodulin‐dependent protein kinase II (CaMKIIα) and β‐actin RNAs localize to dendrites in distinct RNPs, which contain—unexpectedly—very few RNA molecules. The number of MAP2 molecules per particle is affected by synaptic activity and Staufen 2, indicating that RNP composition is tightly controlled. Our data suggest that the independent localization of individual RNAs in low copy numbers could contribute to tighter temporal and spatial control of expression in neurons and synapse‐specific plasticity.
Yan, an ETS‐domain transcription factor, negatively modulates the Wingless pathway in the Drosophila eye
Authors: Olson Emily R , Pancratov Raluca , Chatterjee Sujash S , Changkakoty Binita , Pervaiz Zeeshan , DasGupta Ramanuj
Published: August 2011

We report the identification of yan, an ETS‐domain transcription factor belonging to the Drosophila epidermal growth factor receptor (DER) pathway, as an antagonist of the Wingless signalling pathway. We demonstrate that cells lacking yan function in the Drosophila eye show increased Wingless pathway activity, and inhibition of Wingless signalling in yan−/− cells rescues the yan mutant phenotype. Biochemical analysis shows that Yan physically associates with Armadillo, a crucial effector of the Wingless pathway, thereby suggesting a direct regulatory mechanism. We conclude that yan represents a new and unsuspected molecular link between the Wingless and DER pathways.
A common single nucleotide polymorphism A118G of the μ opioid receptor alters its N-glycosylation and protein stability
Authors: Huang Peng , Chen Chongguang , Mague Stephen D. , Blendy Julie A. , Liu-Chen Lee-Yuan
Published: August 2011

The A118G SNP (single nucleotide polymorphism) of the hMOPR [human MOPR (μ opioid receptor)] gene OPRM1 results in an amino acid substitution (N40D). Subjects homozygous for the 118G allele have been reported to require higher morphine doses to achieve adequate analgesia, and the 118G allele is more prevalent among drug abusers. However, changes in the MOPR protein associated with this SNP are unknown. Using a knockin mouse model (G/G mice; mice homozygous for the 112G allele of MOPR) that possesses the equivalent nucleotide/amino acid substitution (A112G; N38D) of the A118G SNP in the hMOPR gene, we investigated the N-linked glycosylation status of thalamic and striatal MOPR in G/G mice compared with A/A mice (wild-type mice homozygous for the 112A allele of MOPR). The molecular mass of MOPR determined by immunoblotting was lower in G/G mice than in A/A mice. Following treatment with peptide N-glycosidase F, which removes all N-linked glycans, both MOPR variants had an identical molecular mass, indicating that this discrepancy was due to a lower level of N-glycosylation of the MOPR in G/G mice. In Chinese-hamster ovary cells stably expressing hMOPRs, 118G/Asp40-hMOPR had a lower molecular mass than 118A/Asn40-hMOPR, which was similarly due to differential N-glycosylation. Pulse–chase studies revealed that the half-life of the mature form of 118G/Asp40-hMOPR (~12 h) was shorter than that of 118A/Asn40-hMOPR (~28 h). Thus the A118G SNP reduces MOPR N-glycosylation and protein stability.
Promoter hypermethylation of DNA damage response genes in hepatocellular carcinoma
Authors: Li Zhiqin , Zhang Hongyan , Yang Jianping , Hao Tielai , Li Shenglei
Published: August 2011

Aberrant methylation of promoter CpG islands is a major inactivation mechanism of tumour‐related genes that play a crucial role in the progression of silencing in human cancers, including HCC (hepatocellular carcinoma). We have examined the promoter methylation status of five important DNA damage response genes in fresh‐frozen HCC tissues and cell lines, as well as the possible correlation between methylation patterns and clinical features of the carcinoma. Promoter methylation status of RASSF1A (Ras association domain family 1), CHFR (checkpoint with forkhead and ring finger domains), GSTP1 (glutathione‐S‐transferase‐pi gene), MGMT [O(6)‐methylguanine‐DNA methyltransferase] and hMLH1 (human mutL homologue 1) were examined by the MSP (methylation‐specific PCR) in 70 HCC tissues and five HCC cell lines. The mRNA expression levels of these genes were measured by RT—PCR (reverse transcription—PCR). Methylation frequencies of these genes tested in HCC were 54 (78%) for RASSF1A, 30 (43%) for CHFR, 26 (38%) for GSTP1 and 22 (32%) for MGMT. No hypermethylation was detected for hMLH1 in any case of HCC or HCC cell lines. Moreover, promoter hypermethylation of RASSF1A, CHFR and GSTP1 in both HepG2 and SNU398 cells, and hypermethylation of MGMT in Huh7 cells, were detected. Treatment of three cell lines with 5Aza‐dC (5‐aza‐20‐deoxycytidine) restored or increased the expression of these genes, implicating aberrant DNA methylation in transcriptional silencing. Hypermethylation of RASSF1A and patient age were significantly associated. CHFR methylation status showed a statistically significant correlation with HCC progression. Methylation of the RASSF1A, CHFR, GSTP1 and MGMT genes seem therefore to play an important role in the pathogenesis of HCC. These epigenetic changes may have prognostic importance for patients with HCC.
Measurement of the Optic Nerve Sheath Diameter in Children: Comparison Between Transbulbar Sonography and Magnetic Resonance Imaging
Authors: Steinborn M. , Fiegler J. , Ruedisser K. , Hapfelmeier A. , Denne C. , Macdonald E. , Hahn H.
Published: August 2011

Purpose: To evaluate the accuracy of measurements of the optic nerve sheath diameter (ONSD) in children by comparing transbulbar sonography with magnetic resonance imaging (MRI).

Materials and Methods: 65 children (age: 3 mo– 17y; mean age: 11.3y) underwent MR imaging of the brain including a heavily T 2-w sequence of the orbit and transbulbar sonography using a 17 MHz linear array transducer. Measurements of the ONSD were performed retrospectively by two experienced readers and all images were evaluated regarding the image quality. Bland-Altman Plots were produced to assess the accuracy of measurements. The correlation between readers and between MR imaging and transbulbar sonography was calculated by the concordance correlation coefficient (CCC).

Results: Overall the mean values of the ONSD for MRI (5.86 ± 0.66 mm) and transbulbar sonography (5.86 ± 0.71 mm) were identical. There was a high correlation between readers for measurements of the ONSD both for transbulbar sonography (CCC = 0.93) as well as for MRI (CCC = 0.9). Comparing the measurement values between transbulbar sonography and MRI, the correlation of ONSD values was good to moderate with a high dependency on image quality (CCC [0.31, 0.68]).

Conclusion: We were able to demonstrate that the ONSD values of transbulbar sonography in children correlate well with MRI if the relevant anatomic structures are depicted and the measuring points are set correctly. Based on the findings of our study, it seems necessary to define normal and cut-off values for the ONSD in children again to finally assess the clinical relevance of the ONSD as a noninvasive parameter for the evaluation of intracranial pressure.
Polarity reversal in bipolar resistive switching in Pr0.7Ca0.3MnO3 noble metal sandwich structures
Authors: Scherff M. , Meyer B.-U. , Hoffmann J. , Jooss Ch.
Published: August 2011

The electrically induced persistent resistance change in perovskite Pr0.7Ca0.3MnO3 films sandwiched by metallic electrodes is analyzed with respect to noble electrode materials (Pt, Au, and Ag) and geometric arrangement by electrical transport measurements. Comparing switching behavior in symmetric and asymmetric electrode interfaces gives evidence for identifying the active, single interface in the switching process. The interaction of two opposing interfaces can lead to an observed switching polarity inversion in different current density regimes in the otherwise well defined bipolar behavior. The different noble metals exhibit a quite similar switching behavior, but a lower interfacial resistance seems to favor switching.
Printed array of thin-dielectric metal-oxide-metal (MOM) tunneling diodes
Authors: Bareiß Mario , Hochmeister Andreas , Jegert Gunther , Zschieschang Ute , Klauk Hagen , Huber Rupert , Grundler Dirk , Porod Wolfgang , Fabel Bernhard , Scarpa Giuseppe , Lugli Paolo
Published: August 2011

A large area array of metal-oxide-metal (MOM) tunneling diodes with an ultrathin dielectric (∼3.6 nm aluminum oxide) have been fabricated via a transfer-printing process. The MOM diodes exhibit an excellent tunneling behavior that is suitable for rectifying high-frequency ac current into direct current (dc). Direct tunneling and Fowler-Nordheim tunneling have been observed over eight orders of magnitude in current density. The ratio between forward and reverse current is as large as two orders of magnitude. Simulations have been carried out to extract the static device parameters and have confirmed the existence of a dipole layer at the aluminum/aluminum oxide interface of the printed tunneling diodes. Capacitance measurements have shown that the permittivity of the ultrathin aluminum oxide film is smaller than that of bulk aluminum oxide. The mechanical yield of the transfer-printing process is better than 80%, confirming that transfer printing is a promising candidate for the efficient fabrication of quantum devices over large areas.
Optimum condition for magnetic properties of two-phase soft magnetic alloys
Authors: He Kai-Yuan
Published: August 2011

It is well-known that the optimum condition to obtain the highest permeability and lowest coercive force for a soft magnetic material is that both K and λs are very small. In this paper, it is suggested that this optimum condition is sufficient only for the single phase soft magnetic material. For the material containing two phases, in order to obtain the best magnetic properties, a new condition must be added; the difference in the magnitude of the saturation magnetization of the two phases, ΔMS, should be very small. Only when the K, λs, and ΔMS are all very small can the best soft magnetic properties be obtained. A model describing the hindrance of the domain well motion by the ΔMS effect is suggested. Some examples in the nanocrystalline soft magnetic alloys are used to demonstrate the existence of the ΔMS effect.
Effect of toroidal magnetic field on n = 1 mode stability in rotamak plasmas
Authors: Yang X. , Goss J. , Kalaria D. , Huang T. S.
Published: August 2011

To study the effect of toroidal magnetic field on n = 1 mode stability, a series of experiments with linearly ramping the axial current Iz, which makes field-reversed configuration (FRC) to spherical tokamak (ST) transition, have been conducted in rotamak. Results clearly demonstrate that the tilt mode can be completely suppressed by small Iz around 0.4 kA (in comparison with 2.0 kA plasma current). An unknown new mode with larger magnetic perturbations is triggered when Iz reaches 0.5 kA. This instability mode keeps saturation while plasma current is boosted when Iz is in the range of 0.6–1.4 kA. When Iz exceeds 1.6 kA, the new mode suddenly disappears and discharge is free from instability modes.
Ab initio investigation on ion-associated species and association process in aqueous Na2SO4 and Na2SO4/MgSO4 solutions
Authors: Zhang Hao , Wang Song , Sun Chia-Chung
Published: August 2011

In the present paper, the possible ion associated species in pure Na2SO4 and mixed Na2SO4/MgSO4 aqueous solutions are investigated via the ab initio method at the HF/6-31+G* level. The vibrational v1-SO42− band is analyzed. For the unhydrated species, when the number of metal ions around the SO42− ion is less than 3, the dominating effect to the v1-SO42− band is the polarization of the cations, while the M–O bonding will be dominating as the number is equal to or more than 3. For the hydrated species, the coordinated structures of the Na+ ion in all ion pairs are not stable due to the strong effect of the SO42− ion but relatively stable in the triple ion (TI) clusters since there are fewer vacant hydration sites around the SO42−. The v1-SO42− frequencies are close to that of the hydrated SO42− ion in the ion pairs and larger in both Na2SO4 and Na2SO4/MgSO4 TI clusters. On the basis of our calculated results, the evolvement of Raman spectra in the Na2SO4/MgSO4 droplet with the molar ratio of 1:1 is explained.
Weak intermolecular interactions in gas-phase nuclear magnetic resonance
Authors: Garbacz Piotr , Piszczatowski Konrad , Jackowski Karol , Moszynski Robert , Jaszuński Michał
Published: August 2011

Gas-phase nuclear magnetic resonance (NMR) spectra demonstrating the effect of weak intermolecular forces on the NMR shielding constants of the interacting species are reported. We analyse the interaction of the molecular hydrogen isotopomers with He, Ne, and Ar, and the interaction in the He–CO2 dimer. The same effects are studied for all these systems in the ab initio calculations. The comparison of the experimental and computed shielding constants is shown to depend strongly on the treatment of the bulk susceptibility effects, which determine in practice the pressure dependence of the experimental values. Best agreement of the results is obtained when the bulk susceptibility correction in rare gas solvents is evaluated from the analysis of the He-rare gas interactions, and when the shielding of deuterium in D2–rare gas systems is considered.
Atomic and electronic structures of a transition layer at the CrN/Cr interface
Authors: Zhang Zaoli , Daniel Rostislav , Mitterer Christain
Published: August 2011

By spherical aberration (CS)-corrected high-resolution transmission electron microscopy (HRTEM) and electron energy-loss spectroscopy (EELS), the atomic and electronic structures at the CrN/Cr interface are studied. A transition layer is formed at the CrN/Cr interface, which is identified as hexagonal Cr2N. The atomic structures at the interfaces are revealed. The elemental concentration distribution across the interface was quantified by EELS. The fine structures of Cr-L2,3 in Cr, CrN, and Cr2N exhibit a subtle difference. The Cr-L2,3 edge in CrN shows a noticeable chemical shift as compared to Cr and Cr2N, accompanied by a slight variation at the corresponding N-K edge.
Heat transfer and pressure drop through rectangular helical ducts
Authors: Sleiti Ahmad K.
Published: August 2011

Optimization of heat transfer and flow in a helical duct of rectangular cross-section used to cool the stators of electric machines is studied using computational fluid dynamics (CFD) techniques. Realizable turbulent model is used with water and oil as working fluids for two different designs (helical continuous (HC) and helical reverse annulus (HRA) designs) and total of five configurations of the helical duct at small pitch size of 0.00254 m. The HRA is a new design proposed by the author. Due to the curvature of the ducts, as fluid flows through curved tubes, a centrifugal force is generated. A secondary flow induced by the centrifugal force has significant ability to enhance the heat transfer rate. Results showed that the HC design provides better heat transfer in terms of lower surface temperatures at the expense of higher pressure drop for the same flow rate of fluid.
The k-j-j′ vector correlation in inelastic and reactive scattering
Authors: Brouard M. , Chadwick H. , Eyles C. J. , Aoiz F. J. , Kłos J.
Published: August 2011

Quasi-classical trajectory (QCT) methods are presented which allow characterization of the angular momentum depolarization of the products of inelastic and reactive scattering. The particular emphasis of the theory is on three-vector correlations, and on the connection with the two-vector correlation between the initial and final angular momenta, \documentclass[12pt]{minimal}\begin{document}$\bm j$\end{document}j and \documentclass[12pt]{minimal}\begin{document}$\bm j^{\prime }$\end{document}j′, which is amenable to experimental measurement. The formal classical theory is presented, and computational results for NO(A) + He are used to illustrate the type of mechanistic information provided by analysis of the two- and three-vector correlations. The classical \documentclass[12pt]{minimal}\begin{document}$\bm j$\end{document}j-\documentclass[12pt]{minimal}\begin{document}$\bm j^{\prime }$\end{document}j′ two-vector correlation results are compared with quantum mechanical calculations, and are shown to be in good agreement. The data for NO(A) + He support previous conclusions [M. Brouard, H. Chadwick, Y.-P. Chang, R. Cireasa, C. J. Eyles, A. O. L. Via, N. Screen, F. J. Aoiz, and J. Kłos, J. Chem. Phys. 131, 104307 (2009)]10.1063/1.3212608 that this system is only weakly depolarizing. Furthermore, it is shown that the projection of \documentclass[12pt]{minimal}\begin{document}$\bm j$\end{document}j along the kinematic apse is nearly conserved for this system under thermal collision energy conditions.