4,157 research outputs found
Magnetic Domains in Magnetar Matter as an Engine for Soft Gamma-ray Repeaters and Anomalous X-ray Pulsars
Magnetars have been suggested as the most promising site for the origin of
observed soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs). In
this work we investigate the possibility that SGRs and AXPs might be
observational evidence for a magnetic phase separation in magnetars. We study
magnetic domain formation as a new mechanism for SGRs and AXPs in which
magnetar-matter separates into two phases containing different flux densities.
We identify the parameter space in matter density and magnetic field strength
at which there is an instability for magnetic domain formation. We conclude
that such instabilities will likely occur in the deep outer crust for the
magnetic Baym, Pethick, and Sutherland (BPS) model and in the inner crust and
core for magnetars described in relativistic Hartree theory. Moreover, we
estimate that the energy released by the onset of this instability is
comparable with the energy emitted by SGRs.Comment: 4 figures, ApJ in pres
Complete reducibility and subgroups of exceptional algebraic groups
This survey article has two components. The first part gives a gentle
introduction to Serre's notion of -complete reducibility, where is a
connected reductive algebraic group defined over an algebraically closed field.
The second part concerns consequences of this theory when is simple of
exceptional type, specifically its role in elucidating the subgroup structure
of . The latter subject has a history going back about sixty years. We give
an overview of what is known, up to the present day. We also take the
opportunity to offer several corrections to the literature.Comment: 42 page
Col-OSSOS: Colors of the Interstellar Planetesimal 1I/`Oumuamua
The recent discovery by Pan-STARRS1 of 1I/2017 U1 (`Oumuamua), on an unbound
and hyperbolic orbit, offers a rare opportunity to explore the planetary
formation processes of other stars, and the effect of the interstellar
environment on a planetesimal surface. 1I/`Oumuamua's close encounter with the
inner Solar System in 2017 October was a unique chance to make observations
matching those used to characterize the small-body populations of our own Solar
System. We present near-simultaneous g, r, and J photometry
and colors of 1I/`Oumuamua from the 8.1-m Frederick C. Gillett Gemini North
Telescope, and photometry from the 4.2 m William Herschel Telescope. Our
grJ observations are directly comparable to those from the
high-precision Colours of the Outer Solar System Origins Survey (Col-OSSOS),
which offer unique diagnostic information for distinguishing between outer
Solar System surfaces. The J-band data also provide the highest signal-to-noise
measurements made of 1I/`Oumuamua in the near-infrared. Substantial, correlated
near-infrared and optical variability is present, with the same trend in both
near-infrared and optical. Our observations are consistent with 1I/`Oumuamua
rotating with a double-peaked period of hours and being a
highly elongated body with an axial ratio of at least 5.3:1, implying that it
has significant internal cohesion. The color of the first interstellar
planetesimal is at the neutral end of the range of Solar System and
solar-reflectance colors: it is like that of some dynamically excited objects
in the Kuiper belt and the less-red Jupiter Trojans.Comment: Accepted to ApJ
Using Design Interventions to Develop Communication Solutions for Integrated Pest Management
Iowa State University’s (ISU) Integrated Pest Management (IPM) program partnered with the ISU College of Design (COD) to use Design Thinking and other practical design methodologies and theories to identify and develop approaches to address IPM extension and communication issues. ISU IPM met with agriculture industry, program colleagues, and ISU COD faculty to discuss IPM-related needs in agriculture and to determine the program’s primary challenges. ISU COD faculty developed a two-semester course for undergraduate students, allocating various resources to solve these challenges. Undergraduates in the course, as the primary agents and problem solvers, developed various strategies the IPM program and its colleagues could implement. A model of interdisciplinary collaboration was developed, where design and science may function as equal partners in a design education setting. In our collaboration, the partners bought into a design-led process-based methodology that began with identifying IPM communication needs. This project resulted in unique design interventions to communicate IPM to stakeholders and the public, as well as created a model for interdisciplinary cooperation that can be exported to fields outside of agriculture and IPM
Taking Free Flap Surgery Abroad: A Collaborative Approach to a Complex Surgical Problem.
Accessibility to health care, especially complex surgical care, represents one of the major health care disparities in developing countries. While surgical teams may be willing to travel to these areas to help address these needs, there are many logistical and ethical dilemmas inherent in this pursuit. We reviewed our approach to the establishment of the team-based surgical outreach program, wherein we perform head and neck free tissue transfer surgery in Haiti. We describe the challenges encountered in the delivery of surgical care as well as ethical dilemmas relevant to surgical outreach trips, highlighting an approach reliant on strong local cooperation. Despite the obstacles in place, our experience shows that free flap surgery can be successfully and ethically performed in these areas of great need
Design and Fabrication of a Fully-Integrated, Miniaturised Fluidic System for the Analysis of Enzyme Kinetics
The average laboratory samples a population of 7,300 Amazon Mechanical Turk workers
Using capture-recapture analysis we estimate the effective size of the active Amazon Mechanical Turk (MTurk) population that a typical laboratory can access to be about 7,300 workers. We also estimate that the time taken for half of the workers to leave the MTurk pool and be replaced is about 7 months. Each laboratory has its own population pool which overlaps, often extensively, with the hundreds of other laboratories using MTurk. Our estimate is based on a sample of 114,460 completed sessions from 33,408 unique participants and 689 sessions across seven laboratories in the US, Europe, and Australia from January 2012 to March 2015
Seroprevalence of Zika virus in wild African green monkeys and baboons
ABSTRACT Zika virus (ZIKV) has recently spread through the Americas and has been associated with a range of health effects, including birth defects in children born to women infected during pregnancy. Although the natural reservoir of ZIKV remains poorly defined, the virus was first identified in a captive “sentinel” macaque monkey in Africa in 1947. However, the virus has not been reported in humans or nonhuman primates (NHPs) in Africa outside Gabon in over a decade. Here, we examine ZIKV infection in 239 wild baboons and African green monkeys from South Africa, the Gambia, Tanzania, and Zambia using combinations of unbiased deep sequencing, quantitative reverse transcription-PCR (qRT-PCR), and an antibody capture assay that we optimized using serum collected from captive macaque monkeys exposed to ZIKV, dengue virus, and yellow fever virus. While we did not find evidence of active ZIKV infection in wild NHPs in Africa, we found variable ZIKV seropositivity of up to 16% in some of the NHP populations sampled. We anticipate that these results and the methodology described within will help in continued efforts to determine the prevalence, natural reservoir, and transmission dynamics of ZIKV in Africa and elsewhere. IMPORTANCE Zika virus (ZIKV) is a mosquito-borne virus originally discovered in a captive monkey living in the Zika Forest of Uganda, Africa, in 1947. Recently, an outbreak in South America has shown that ZIKV infection can cause myriad health effects, including birth defects in the children of women infected during pregnancy. Here, we sought to investigate ZIKV infection in wild African primates to better understand its emergence and spread, looking for evidence of active or prior infection. Our results suggest that up to 16% of some populations of nonhuman primate were, at some point, exposed to ZIKV. We anticipate that this study will be useful for future studies that examine the spread of infections from wild animals to humans in general and those studying ZIKV in primates in particular. Podcast: A podcast concerning this article is available
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