Magnetic Reconnection in Extreme Astrophysical Environments

Magnetic reconnection is a basic plasma process of dramatic rearrangement of magnetic topology, often leading to a violent release of magnetic energy. It is important in magnetic fusion and in space and solar physics --- areas that have so far provided the context for most of reconnection research. Importantly, these environments consist just of electrons and ions and the dissipated energy always stays with the plasma. In contrast, in this paper I introduce a new direction of research, motivated by several important problems in high-energy astrophysics --- reconnection in high energy density (HED) radiative plasmas, where radiation pressure and radiative cooling become dominant factors in the pressure and energy balance. I identify the key processes distinguishing HED reconnection: special-relativistic effects; radiative effects (radiative cooling, radiation pressure, and Compton resistivity); and, at the most extreme end, QED effects, including pair creation. I then discuss the main astrophysical applications --- situations with magnetar-strength fields (exceeding the quantum critical field of about 4 x 10^13 G): giant SGR flares and magnetically-powered central engines and jets of GRBs. Here, magnetic energy density is so high that its dissipation heats the plasma to MeV temperatures. Electron-positron pairs are then copiously produced, making the reconnection layer highly collisional and dressing it in a thick pair coat that traps radiation. The pressure is dominated by radiation and pairs. Yet, radiation diffusion across the layer may be faster than the global Alfv\'en transit time; then, radiative cooling governs the thermodynamics and reconnection becomes a radiative transfer problem, greatly affected by the ultra-strong magnetic field. This overall picture is very different from our traditional picture of reconnection and thus represents a new frontier in reconnection research.Comment: Accepted to Space Science Reviews (special issue on magnetic reconnection). Article is based on an invited review talk at the Yosemite-2010 Workshop on Magnetic Reconnection (Yosemite NP, CA, USA; February 8-12, 2010). 30 pages, no figure

Effects of measurement statistics on the detection of damage in the Alamosa Canyon Bridge

This paper presents a comparison of the statistics on the measured model parameters of a bridge structure to the expected changes in those parameters caused by damage. It is then determined if the changes resulting from damage are statistically significant. This paper considers the most commonly used modal parameters for indication of damage: modal frequency, mode shape, and mode shape curvature. The approach is divided into two steps. First, the relative uncertainties (arising from random error sources) of the measured modal frequencies, mode shapes, and mode shape curvatures are determined by Monte Carlo analysis of the measured data. Based on these uncertainties, 95% statistical confidence bounds are computed for these parameters. The second step is the determination of the measured change in these parameters resulting from structural damage. Changes which are outside the 95% bounds are considered to be statistically significant. It is proposed that this statistical significance can be used to selectively filter which modes are used for damage identification. The primary conclusion of the paper is that the selection of the appropriate parameters to use in the damage identification algorithm must take into account not only the sensitivity of the damage indicator to the structural deterioration, but also the uncertainty inherent in the measurement of the parameters used to compute the indicator

The Role of Color Neutrality in Nuclear Physics--Modifications of Nucleonic Wave Functions

The influence of the nuclear medium upon the internal structure of a composite nucleon is examined. The interaction with the medium is assumed to depend on the relative distances between the quarks in the nucleon consistent with the notion of color neutrality, and to be proportional to the nucleon density. In the resulting description the nucleon in matter is a superposition of the ground state (free nucleon) and radial excitations. The effects of the nuclear medium on the electromagnetic and weak nucleon form factors, and the nucleon structure function are computed using a light-front constituent quark model. Further experimental consequences are examined by considering the electromagnetic nuclear response functions. The effects of color neutrality supply small but significant corrections to predictions of observables.Comment: 37 pages, postscript figures available on request to [email protected]

STC1 interference on calcitonin family of receptors signaling during osteoblastogenesis via adenylate cyclase inhibition

Stanniocalcin 1 (STC1) and calcitonin gene-related peptide (CGRP) are involved in bone formation/remodeling. Here we investigate the effects of STC1 on functional heterodimer complex CALCRL/RAMP1, expression and activity during osteoblastogenesis. STC1 did not modify CALCRL and ramp 1 gene expression during osteoblastogenesis when compared to controls. However, plasma membrane spatial distribution of CALCRL/RAMP1 was modified in 7-day pre-osteoblasts exposed to either CGRP or STC1, and both peptides induced CALCRL and RAMP1 assembly. CGRP, but not STC1 stimulated cAMP accumulation in 7-day osteoblasts and in CALCRL/RAMP1 transfected HEK293 cells. Furthermore, STC1 inhibited forskolin stimulated cAMP accumulation of HEK293 cells, but not in CALCRL/RAMP1 transfected HEK293 cells. However, STC1 inhibited cAMP accumulation in calcitonin receptor (CTR) HEK293 transfected cells stimulated by calcitonin. In conclusion, STC1 signals through inhibitory G-protein modulates CGRP receptor spatial localization during osteoblastogenesis and may function as a regulatory factor interacting with calcitonin peptide members during bone formation. (C) 2015 Elsevier Ireland Ltd. All rights reserved.CAPES/CNPq (VS PNPD fellowship program); FAPERGS/CNPq [008/2009 (FCRG)]; Portuguese Foundation for Science and Technology (FCT) [PTDC/MAR/121279/2010, PEst-C/MAR/LA0015/2013, SFRH/BPD/89811/2012]; CNPq (SRT PhD fellowship program); CNPq (LAMM PhD fellowship program); CNPq (FCRG research productivity fellowship program); INCT Exitotoxicity and Neuroprotection (DOGS

Design and Microwave-assisted Synthesis of 1,3,4-Oxadiazole Derivatives for Analgesic and Anti-inflammatory Activity

1,3,4-Oxadizoles form a biologically important group of compounds having activities like analgesic, anti-inflammatory, bactericidal, antifungal, anticonvulsant, psychotropic, plant growth regulating and mono amino oxidase inhibition. This research has focused on the incorporation of the oxadiazole moiety into isoniazid because of their versatile biological action, to get 2-aryl-5-(4-pyridyl)-1,3,4-oxadiazole to explore the possibilities of some altered biological action. 1,3,4-Oxadiazole derivatives were synthesized by microwave-assisted synthesis and screened for their analgesic, anti-inflammatory activities. The synthesized compounds were characterized by Melting point, Thin layer chromatographyInfra red, Nuclear magnetic resonance spectroscopy, etc. Almost all the synthesized compounds possessed good activity as compared to the standard

Undergraduate research. Genomics Education Partnership

The Genomics Education Partnership offers an inclusive model for undergraduate research experiences incorporated into the academic year science curriculum, with students pooling their work to contribute to international data bases

A central support system can facilitate implementation and sustainability of a Classroom-based Undergraduate Research Experience (CURE) in Genomics

In their 2012 report, the President\u27s Council of Advisors on Science and Technology advocated replacing standard science laboratory courses with discovery-based research courses -a challenging proposition that presents practical and pedagogical difficulties. In this paper, we describe our collective experiences working with the Genomics Education Partnership, a nationwide faculty consortium that aims to provide undergraduates with a research experience in genomics through a scheduled course (a classroom-based undergraduate research experience, or CURE). We examine the common barriers encountered in implementing a CURE, program elements of most value to faculty, ways in which a shared core support system can help, and the incentives for and rewards of establishing a CURE on our diverse campuses. While some of the barriers and rewards are specific to a research project utilizing a genomics approach, other lessons learned should be broadly applicable. We find that a central system that supports a shared investigation can mitigate some shortfalls in campus infrastructure (such as time for new curriculum development, availability of IT services) and provides collegial support for change. Our findings should be useful for designing similar supportive programs to facilitate change in the way we teach science for undergraduates

A course-based research experience: how benefits change with increased investment in instructional time

There is widespread agreement that science, technology, engineering, and mathematics programs should provide undergraduates with research experience. Practical issues and limited resources, however, make this a challenge. We have developed a bioinformatics project that provides a course-based research experience for students at a diverse group of schools and offers the opportunity to tailor this experience to local curriculum and institution-specific student needs. We assessed both attitude and knowledge gains, looking for insights into how students respond given this wide range of curricular and institutional variables. While different approaches all appear to result in learning gains, we find that a significant investment of course time is required to enable students to show gains commensurate to a summer research experience. An alumni survey revealed that time spent on a research project is also a significant factor in the value former students assign to the experience one or more years later. We conclude: 1) implementation of a bioinformatics project within the biology curriculum provides a mechanism for successfully engaging large numbers of students in undergraduate research; 2) benefits to students are achievable at a wide variety of academic institutions; and 3) successful implementation of course-based research experiences requires significant investment of instructional time for students to gain full benefit