bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chromosphere above sunspots as seen at millimeter wavelengths
Authors: Loukitcheva Maria A. , Solanki Sami K. , White Stephen M. 
Published: August 2011

AbstractMillimeter 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

AbstractEvolution 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

AbstractHow 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

AbstractNumerical 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

AbstractToday'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

AbstractWe 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

AbstractWe 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

AbstractFrom 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

AbstractIn 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

AbstractWe 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

AbstractWe 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

AbstractA 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

AbstractA 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.
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

AbstractAberrant 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

Abstract
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.
Pathology of oesophagitis
Authors: Maguire Aoife , Sheahan Kieran 
Published: August 2011

Maguire A & Sheahan K  (2012) Histopathology 60, 864–879 Pathology of oesophagitisEndoscopic oesophageal biopsies are common in daily pathology practice. Inflammation and damage of the oesophageal mucosa is known as oesophagitis and is common worldwide. A variety of physical, chemical and infectious agents cause oesophagitis. The oesophagus has a limited range of responses to a wide variety of injuries, and so histopathological features of different diseases often overlap. The pathologist is reliant on the endoscopist for the ‘macroscopic description’ of the oesophagus. Access to the endoscopic images enhances the pathologist’s overall interpretation of the case. Correlating clinical, endoscopic and microscopic findings may be crucial in arriving at the correct diagnosis. In this review, we present clinicopathological descriptions of the major types of oesophagitis.
Racial Harassment, Ethnic Concentration, and Economic Conditions*
Authors: Dustmann Christian , Fabbri Francesca , Preston Ian 
Published: August 2011

AbstractIn this paper, we analyse the association between the spatial concentration of ethnic minorities and racial harassment. Ethnic concentration relates to racial harassment through at least three channels: hostility in the attitudes of majority individuals that finds expression in harassment behaviour, the probability that minority individuals meet majority individuals, and the cost of expressing hostility aggressively. Thus, harassment cannot simply be modelled as a stronger form of hostility. Using unique data for Britain, we show that, in areas of higher local ethnic concentration, experience of harassment is lower, even though hostility on the side of the majority population is not.
Restrictions to G(𝔽p) and G(r) of rational G-modules
Authors: Friedlander Eric M. 
Published: August 2011

AbstractWe fix a prime p and consider a connected reductive algebraic group G over a perfect field k which is defined over 𝔽p. Let M be a finite-dimensional rational G-module M, a comodule for k[G]. We seek to somewhat unravel the relationship between the restriction of M to the finite Chevalley subgroup G(𝔽p)⊂G and the family of restrictions of M to Frobenius kernels G(r) ⊂G. In particular, we confront the conundrum that if M is the Frobenius twist of a rational G-module N,M=N(1), then the restrictions of M and N to G(𝔽p) are equal whereas the restriction of M to G(1) is trivial. Our analysis enables us to compare support varieties (and the finer non-maximal support varieties) for G(𝔽p) and G(r) of a rational G-module M where the choice of r depends explicitly on M.
Does increased information about reproductive potential result in better prediction of recruitment?
Authors: Morgan M. Joanne , Perez-Rodriguez Alfonso , Saborido-Rey Fran 
Published: August 2011

The relationship between stock size and recruitment is an essential element in the understanding of the productivity of a population. However, predicting the number of recruits produced by a population has proven to be a difficult challenge. This may in part be a result of poor estimation of reproductive potential (RP). We determined if including increased information on reproductive biology in indices of RP results in better predictions of recruitment. We investigated some of the conditions that lead to better (or worse) recruitment prediction when more biologically complex indices of RP are used. Data from four populations in the Northwest Atlantic were examined: southern Grand Bank (NAFO Division 3NO) cod ( Gadus morhua ), Flemish Cap (NAFO Division 3M) cod, Newfoundland (NAFO Division 3LNO) American plaice ( Hippoglossoides platessoides ), and Greenland halibut ( Reinhardtius hippoglossoides ) (NAFO Subarea 2 + Division 3KLMNO). Stock–recruit models paired with complex indices of RP gave a better estimate of recruitment in slightly more than half of the tests conducted. When there were larger trends in the reproductive biology (maturity at age, sex ratio and egg production), more complex indices of RP were more likely to provide a better estimate of recruitment.