Simultaneous dual-frequency radio observations of S5 0716+714: A search for intraday variability with the Korean VLBI Network

This study aims to search for the existence of intraday variability (IDV) of BL Lac object S5 0716+714 at high radio frequencies for which the interstellar scintillation effect is not significant. Using the 21-meter radio telescope of the Korean VLBI Network (KVN), we present results of multi-epoch simultaneous dual-frequency radio observations. Single-dish observations of S5 0716+714 were simultaneously conducted at 21.7 GHz (K-band) and 42.4 GHz (Q-band), with a high cadence of 30-60 minute intervals.We observed four epochs between December 2009 and June 2010. Over the whole set of observation epochs, S5 0716+714 showed significant inter-month variations in flux density at both the K- and Q-bands, with modulation indices of approximately 19% for the K-band and approximately 36% for the Q-band. In all epochs, no clear intraday variability was detected at either frequency. The source shows monotonic flux density increase in epochs 1 and 3 and monotonic flux density decrease in epochs 2 and 4. In the flux density increasing phases, the flux densities at the Q-band increase more rapidly. In the decreasing phase, no significant flux density difference is seen at the two frequencies. The situation could be different close to flux density peaks that we did not witness in our observations. We find an inverted spectrum with mean spectral indices of -0.57+-0.13 in epoch 1 and -0.15+-0.11 in epoch 3. On the other hand, we find relatively steep indices of +0.24+-0.14 and +0.17+-0.18 in epochs 2 and 4, respectively. We conclude that the frequency dependence of the variability and the change of the spectral index are caused by source-intrinsic effects rather than by any extrinsic scintillation effect.Comment: 6 pages and 4 figures and 4 table

Electronic, optical and thermal properties of the hexagonal and fcc Ge2Sb2Te5 chalcogenide from first-principle calculations

We present a comprehensive computational study on the properties of face-centered cubic and hexagonal chalcogenide Ge2Sb2Te5. We calculate the electronic structure using density functional theory (DFT); the obtained density of states (DOS) compares favorably with experiments, also looking suitable for transport analysis. Optical constants including refraction index and absorption coefficient capture major experimental features, aside from an energy shift owed to an underestimate of the band gap that is typical of DFT calculations. We also compute the phonon DOS for the hexagonal phase, obtaining a speed of sound and thermal conductivity in good agreement with the experimental lattice contribution. The calculated heat capacity reaches ~ 1.4 x 106 J/(m3 K) at high temperature, in agreement with experimental data, and provides insight into the low-temperature range (< 150 K), where data are unavailable.Comment: 19 pages, 8 figure

Magnetic domain wall motion in a nanowire: depinning and creep

The domain wall motion in a magnetic nanowire is examined theoretically in the regime where the domain wall driving force is weak and its competition against disorders is assisted by thermal agitations. Two types of driving forces are considered; magnetic field and current. While the field induces the domain wall motion through the Zeeman energy, the current induces the domain wall motion by generating the spin transfer torque, of which effects in this regime remain controversial. The spin transfer torque has two mutually orthogonal vector components, the adiabatic spin transfer torque and the nonadiabatic spin transfer torque. We investigate separate effects of the two components on the domain wall depinning rate in one-dimensional systems and on the domain wall creep velocity in two-dimensional systems, both below the Walker breakdown threshold. In addition to the leading order contribution coming from the field and/or the nonadiabatic spin transfer torque, we find that the adiabatic spin transfer torque generates corrections, which can be of relevance for an unambiguous analysis of experimental results. For instance, it is demonstrated that the neglect of the corrections in experimental analysis may lead to incorrect evaluation of the nonadiabaticity parameter. Effects of the Rashba spin-orbit coupling on the domain wall motion are also analyzed.Comment: 14 pages, 3 figure

Poly(A) RNA and Paip2 act as allosteric regulators of poly(A)-binding protein

When bound to the 30 poly(A) tail of mRNA, poly(A)binding protein (PABP) modulates mRNA translation and stability through its association with various proteins. By visualizing individual PABP molecules in real time, we found that PABP, containing four RNA recognition motifs (RRMs), adopts a conformation on poly(A) binding in which RRM1 is in proximity to RRM4. This conformational change is due to the bending of the region between RRM2 and RRM3. PABP-interacting protein 2 actively disrupts the bent structure of PABP to the extended structure, resulting in the inhibition of PABP-poly(A) binding. These results suggest that the changes in the configuration of PABP induced by interactions with various effector molecules, such as poly(A) and PABP-interacting protein 2, play pivotal roles in its function.X1143sciescopu

Lazaroid U-74500A for warm ischemia and reperfusion injury of the canine small intestine

BACKGROUND: Although lazaroids have been shown to protect various organs from ischemia/reperfusion injury, results obtained in the small intestine have been conflicting. STUDY DESIGN: The canine small intestine was made totally ischemic for 2 hours by occluding the superior mesenteric artery and the superior mesenteric vein with interruption of the mesenteric collateral vessels. A lazaroid compound, U74500A, or a citrate vehicle was given intravenously to each of the six animals for 30 minutes before intestinal ischemia. Intestinal tissue blood flow, lipid peroxidation, neutrophil infiltration, adenine nucleotides and their catabolites, and histologic changes after reperfusion were determined. RESULTS: Lazaroid treatment attenuated decline of the mucosal and serosal blood flow after reperfusion. Accumulation of lipid peroxidation products and neutrophils in mucosal tissues was markedly inhibited by the treatment. Postischemic energy resynthesis was also augmented by lazaroid. Morphologically, mucosal architectures were better preserved with lazaroid treatment after reperfusion, and recovered to normal by postoperative day 3 in the treated group and by post-operative day 7 in control animals. CONCLUSIONS: Lazaroids protect the canine small intestine from ischemia/reperfusion injury by inhibiting lipid peroxidation and neutrophil infiltration. Dogs are tolerant of 2-hour normothermic complete intestinal ischemia

Inter- and Intra-observer Reliability of MRI for Lumbar Lateral Disc Herniation

Background: The authors analyzed inter- and intra-observer agreement with respect to interpretation of simple magnetic resonance T1- and T2-weighted axial and sagittal images for the diagnosis of lumbar lateral disc herniation, including foraminal and extraforaminal disc herniations.Methods: Forty-two patients in whom lumbar lateral disc herniation was suspected or confirmed by simple magnetic resonance imaging at one institute between May 2003 and December 2004 were included. The magnetic resonance images consisting of T1- and T2-weighted axial and sagittal images, and these were reviewed blindly and independently by three orthopaedic spine surgeons in a random manner. The images were interpreted as positive or negative for lateral disc herniation on 2 different occasions 3 months apart. Results were analyzed using Cohens kappa statistic, and strengths of agreements were determined using the Landis and Koch criteria.Results: The kappa values for inter-observer agreement averaged 0.234 (0.282, 0.111, and 0.308 respectively) on the first occasion, and 0.166 (0.249, 0.111, and 0.137 respectively) on the second occasion, with an overall mean value of 0.200. Thus, the strength of agreement was only slight-to-fair according to the Landis and Koch criteria. Kappa values for intra-observer agreement averaged 0.479 (0.488, 0.491, and 0.459 respectively), indicating moderate agreement.Conclusions: The present study indicates that simple magnetic resonance imaging is not a reliable imaging modality for diagnosing lumbar lateral disc herniation. Another imaging study with improved diagnostic values should be developed to diagnose this pathologic finding.Keywords: Lumbar lateral disc herniation, Inter-observer reliability, Intra-observer reliability, Magnetic resonance imagingOAIID:oai:osos.snu.ac.kr:snu2009-01/102/0000004226/1SEQ:1PERF_CD:SNU2009-01EVAL_ITEM_CD:102USER_ID:0000004226EMP_ID:A076317DEPT_CD:801FILENAME:E019T_CiOS-2009_Kim_Inter-and Intra-observer Reliability of MRI for Lumbar.pdfDEPT_NM:의학과EMAIL:[email protected]_YN:NCONFIRM:YCONFIRM:

Genotyping of Sarawak rice cultivars using microsatellite markers

Genetic diversity of 53 Sarawak rice cultivars, originating from Southern Sarawak, was assessed using 54 microsatellite markers. Initial polymorphism detection was conducted using 54 primer pairs distributed on 12 rice chromosomes. Polymorphic markers were chosen from the initial screening results in order to obtain microsatellite marker panels that can differentiate the rice cultivars undertaken in the study. The chosen microsatellite marker panel consisted of RM1, RM240, RM489, RM252, RM413, RM204, RM11, RM404, RM316, RM271, RM206, and RM19, with one representative from each chromosome. A total of 43 alleles were detected with an average of 3.58 alleles per locus. The polymorphism information content (PIC) values obtained from the microsatellite marker panels ranged from 0.306 to 0.730, with an average of 0.622. The Unweighted Pair Group Method with Arithmetic Mean (UPGMA) dendrogram (r = 0.789) revealed 2 major groups with 6 sub-clusters and the wide range of similarity values (0.24-1.0) obtained showed a high degree of diversity among the cultivars. The results suggest microsatellite markers as a useful tool for the estimation of genetic diversity and cultivar differentiation and present invaluable genetic information for future breeding and association mapping efforts