Modeling of magnetic island formation in magnetic reconnection experiment

Formation of a magnetic island found in the Magnetic Reconnection Experiment (MRX) [M. Yamada, H. Ji, S. Hsu, et al., Phys. Plasmas 4, 1936 (1997)] is investigated by a magnetohydrodynamic (MHD) relaxation theory and a numerical simulation. In the cohelicity injection with a mean toroidal field, the growing process of the island into a spheromak-type configuration is explained by quasistatic transition of the force-free and minimum energy state to a state with larger normalized helicity. It also turns out that no magnetic island would be generated in the counterhelicity case. The MHD simulation with inhomogeneous electric resistivity agrees with experimental results, which clearly shows formation and growth of the magnetic island in a diffusion region where the reconnection takes place

Multifocal versus monofocal intraocular lenses after cataract extraction.

BACKGROUND: Good unaided distance visual acuity is now a realistic expectation following cataract surgery and intraocular lens (IOL) implantation. Near vision, however, still requires additional refractive power, usually in the form of reading glasses. Multiple optic (multifocal) IOLs are available which claim to allow good vision at a range of distances. It is unclear whether this benefit outweighs the optical compromises inherent in multifocal IOLs. OBJECTIVES: The objective of this review was to assess the effects of multifocal IOLs, including effects on visual acuity, subjective visual satisfaction, spectacle dependence, glare and contrast sensitivity, compared to standard monofocal lenses in people undergoing cataract surgery. SEARCH METHODS: We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 2), MEDLINE (January 1946 to March 2012), EMBASE (January 1980 to March 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. The electronic databases were last searched on 6 March 2012. We searched the reference lists of relevant articles and contacted investigators of included studies and manufacturers of multifocal IOLs for information about additional published and unpublished studies. SELECTION CRITERIA: All randomised controlled trials comparing a multifocal IOL of any type with a monofocal IOL as control were included. Both unilateral and bilateral implantation trials were included. DATA COLLECTION AND ANALYSIS: Two authors collected data and assessed trial quality. Where possible, we pooled data from the individual studies using a random-effects model, otherwise we tabulated data. MAIN RESULTS: Sixteen completed trials (1608 participants) and two ongoing trials were identified. All included trials compared multifocal and monofocal lenses but there was considerable variety in the make and model of lenses implanted. Overall we considered the trials at risk of performance and detection bias because it was difficult to mask patients and outcome assessors. It was also difficult to assess the role of reporting bias. There was moderate quality evidence that similar distance acuity is achieved with both types of lenses (pooled risk ratio (RR) for unaided visual acuity worse than 6/6: 0.98, 95% confidence interval (CI) 0.91 to 1.05). There was also evidence that people with multifocal lenses had better near vision but methodological and statistical heterogeneity meant that we did not calculate a pooled estimate for effect on near vision. Total freedom from use of glasses was achieved more frequently with multifocal than monofocal IOLs. Adverse subjective visual phenomena, particularly haloes, or rings around lights, were more prevalent and more troublesome in participants with the multifocal IOL and there was evidence of reduced contrast sensitivity with the multifocal lenses. AUTHORS' CONCLUSIONS: Multifocal IOLs are effective at improving near vision relative to monofocal IOLs. Whether that improvement outweighs the adverse effects of multifocal IOLs will vary between patients. Motivation to achieve spectacle independence is likely to be the deciding factor

Off-diagonal quark distribution functions of the pion within an effective single instanton approximation

We develop a relativistic quark model for pion structure, which incorporates the non-trivial structure of the vacuum of Quantum Chromodynamics as modelled by instantons. Pions are boundstates of quarks and the strong quark-pion vertex is determined from an instanton induced effective lagrangian. The interaction of the constituents of the pion with the external electromagnetic field is introduced in gauge invariant form. The parameters of the model, i.e., effective instanton radius and constituent quark masses, are obtained from the vacuum expectation values of the lowest dimensional quark and gluon operators and the low-energy observables of the pion. We apply the formalism to the calculation of the pion form factor by means of the isovector nonforward parton distributions and find agreement with the experimental data.Comment: LaTeX; altered version; references and figures added. Published: paper has been accepted for publication in Nucl. Phys.

Dense Iron Ejecta and Core-collapse Supernova Explosion in the Young Supernova Remnant G11.2-0.3

We present the results of near-infrared spectroscopic observations of dense (\simgt 10$^3$ cm$^{-3}$) iron ejecta in the young core-collapse supernova remnant G11.2-0.3. Five ejecta knots projected to be close to its center show a large dispersion in their Doppler shifts: two knots in the east are blueshifted by more than 1,000 \kms, while three western knots have relatively small blueshifts of 20-60 \kms. This velocity discrepancy may indicate that the western knots have been significantly decelerated or that there exists a systematic velocity difference among the knots. One ejecta filament in the northwestern boundary, on the other hand, is redshifted by \simgt 200 \kms, while opposite filament in the southeastern boundary shows a negligible radial motion. Some of the knots and filaments have secondary velocity components, and one knot shows a bow shock-like feature in the velocity structure. The iron ejecta appear to be devoid of strong emission from other heavy elements, such as S, which may attest to the alpha-rich freezeout process in the explosive nucleosynthesis of the core-collapse supernova explosion close to its center. The prominent bipolar distribution of the Fe ejecta in the northwestern and southeastern direction, along with the elongation of the central pulsar wind nebula in the perpendicular direction, is consistent with the interpretation that the supernova exploded primarily along the northwestern and southeastern direction.Comment: To appear in ApJ Letter

Topological Dislocations and Mixed State of Charge Density Waves

We discuss the possibility of the ``mixed state'' in incommensurate charge density waves with three-dimensional order. It is shown that the mixed state can be created by applying an electric field perpendicular to the chains. This state consists of topological dislocations induced by the external field and is therefore similar to the mixed states of superfluids (type-II superconductor or liquid Helium II). However, the peculiar coupling of charge density waves with the electric field strongly modifies the nature of the mixed state compared to the conventional superfluids. The field and temperature dependence of the properties of the mixed state are studied, and some experimental aspects are discussed.Comment: 10 pages, Revtex format, no figures, to appear in Phys. Rev. Let

Robust acinar cell transgene expression of CreErT via BAC recombineering

Pancreatic acinar cells are critical in gastrointestinal physiology and pancreatitis and may be involved in pancreatic cancer. Previously, a short rat pancreatic elastase promoter has been widely utilized to control acinar cell transgene expression. However, this partial sequence does not confer robust and stable expression. In this study, we tested the hypothesis that a transgene employing bacterial-artificial-chromosome (BAC) technology to express a tamoxifen-regulated Cre recombinase from a full-length mouse elastase gene (BAC-Ela-CreErT) would be more robust and stable. When founders were crossed with Rosa26 reporter mice nearly 100% of acini expressed Β-galactosidase after tamoxifen treatment. The expression was specific for pancreatic acinar cells and these characteristics have remained stable for 2 years. However, because of high levels of expression in differentiated acinar cells, this construct is tamoxifen independent in ∼50% of adult acinar cells. This model of pancreatic acinar specific Cre expression is a powerful tool for future transgenic and knockout studies. genesis 46:390–395, 2008. © 2008 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/60895/1/20411_ftp.pd

Ultrarelativistic limits of boosted dilaton black holes

We investigate the ultrarelativistic limits of dilaton black holes, black $p$-branes (strings), multi-centered dilaton black hole solutions and black $p$-brane (string) solutions when the boost velocity approaches the speed of light. For dilaton black holes and black $p$-branes (boost is along the transverse directions), the resulting geometries are gravitational shock wave solutions generated by a single particle and membrane. For the multi-centered dilaton black hole solutions and black $p$-brane solutions (boost is along the transverse directions), the limiting geometries are shock wave solutions generated by multiple particles and membranes. When the boost is along the membrane directions, for the black $p$-brane and multi-centered black $p$-brane solution, the resulting geometries describe general plane-fronted waves propagating along the membranes. The effect of the dilaton on the limit is considered.Comment: Revtex, 17 pages, no figure

NTAP: for NimbleGen tiling array ChIP-chip data analysis

Summary:NTAP is designed to analyze ChIP-chip data generated by the NimbleGen tiling array platform and to accomplish various pattern recognition tasks that are useful especially for epigenetic studies. The modular design of NTAP makes the data processing highly customizable. Users can either use NTAP to perform the full process of NimbleGen tiling array data analysis, or choose post-processing modules in NTAP to analyze pre-processed epigenetic data generated by other platforms. The output of NTAP can be saved in standard GFF format files and visualized in GBrowse