5,406 research outputs found
Electrodynamics of quasi-two-dimensional BEDT-TTF charge transfer salts
We consider the millimeter-wave electrodynamics specific to
quasi-two-dimensional conductors and superconductors based on the organic donor
molecule BEDT-TTF. Using realistic physical parameters, we examine the current
polarizations that result for different oscillating (GHz) electric and magnetic
field polarizations. We show that, in general, it is possible to discriminate
between effects (dissipation and dispersion) due to in-plane and interlayer ac
currents. However, we also show that it is not possible to selectively probe
any single component of the in-plane conductivity tensor, and that excitation
of interlayer currents is strongly influenced by the sample geometry and the
electromagnetic field polarization.Comment: 5 pages including 3 figures Minor correction to figure
Fluorescent carbon dots from mono- and polysaccharides:synthesis, properties and applications
Fluorescent carbon dots (FCDs) are an emerging class of nanomaterials made from carbon sources that have been hailed as potential non-toxic replacements to traditional semiconductor quantum dots (QDs). Particularly in the areas of live imaging and drug delivery, due to their water solubility, low toxicity and photo- and chemical stability. Carbohydrates are readily available chiral biomolecules in nature which offer an attractive and cheap starting material from which to synthesise FCDs with distinct features and interesting applications. This mini-review article will cover the progress in the development of FCDs prepared from carbohydrate sources with an emphasis on their synthesis, functionalization and technical applications, including discussions on current challenges
Beyond good intentions: lessons on equipment donation from an African hospital.
OBJECTIVE: In 2000, a referral hospital in the Gambia accepted a donation of oxygen concentrators to help maintain oxygen supplies. The concentrators broke down and were put into storage. A case study was done to find the reasons for the problem and to draw lessons to help improve both oxygen supplies and the success of future equipment donations. METHODS: A technical assessment of the concentrators was carried out by a biomedical engineer with relevant expertise. Semi-structured interviews were undertaken with key informants, and content analysis and inductive approaches were applied to construct the history of the episode and the reasons for the failure. FINDINGS: Interviews confirmed the importance of technical problems with the equipment. They also revealed that the donation process was flawed, and that the hospital did not have the expertise to assess or maintain the equipment. Technical assessment showed that all units had the wrong voltage and frequency, leading to overheating and breakdown. Subsequently a hospital donations committee was established to oversee the donations process. On-site biomedical engineering expertise was arranged with a nongovernmental organization (NGO) partner. CONCLUSION: Appropriate donations of medical equipment, including oxygen concentrators, can be of benefit to hospitals in resource-poor settings, but recipients and donors need to actively manage donations to ensure that the donations are beneficial. Success requires planning, technical expertise and local participation. Partners with relevant skills and resources may also be needed. In 2002, WHO produced guidelines for medical equipment donations, which address problems that might be encountered. These guidelines should be publicized and used
Ground-Based Astronomical Instrumentation Development in the United States: A White Paper on the Challenges Faced by the US Community
This invited white paper, submitted to the National Science Foundation in
January of 2020, discusses the current challenges faced by the United States
astronomical instrumentation community in the era of extremely large
telescopes. Some details may have changed since submission, but the basic
tenets are still very much valid. The paper summarizes the technical, funding,
and personnel challenges the US community faces, provides an informal census of
current instrumentation groups in the US, and compares the state-of-affairs in
the US with that of the European community, which builds astronomical
instruments from consortia of large hard-money funded instrument centers in a
coordinated fashion. With the recent release of the Decadal Survey on Astronomy
and Astrophysics 2020 (Astro2020), it is clear that strong community support
exists for this next generation of large telescopes in the US. Is the US ready?
Is there sufficient talent, facilities, and resources in the community today to
meet the challenge of developing the complex suite of instruments envisioned
for two US ELTs? These questions are addressed, along with thoughts on how the
National Science Foundation can help build a more viable and stable
instrumentation program in the US. These thoughts are intended to serve as a
starting point for a broader discussion, with the end goal being a plan that
puts the US astronomical instrumentation community on solid footing and poised
to take on the challenges presented by the ambitious goals we have set in the
era of ELTs.Comment: 22 pages, 1 table, 0 figures. This is an invited white paper
submitted to the National Science Foundation in January of 202
How IDEA Fails Families Without Means: Causes and Corrections From the Frontlines of Special Education
How IDEA Fails Families Without Means: Causes and Corrections From the Frontlines of Special Education
ΦCrAss001 represents the most abundant bacteriophage family in the human gut and infects Bacteroides intestinalis
peer-reviewedCrAssphages are an extensive and ubiquitous family of tailed bacteriophages, predicted to infect bacteria of the order Bacteroidales. Despite being found in ~50% of individuals and representing up to 90% of human gut viromes, members of this viral family have never been isolated in culture and remain understudied. Here, we report the isolation of a CrAssphage (ΦCrAss001) from human faecal material. This bacteriophage infects the human gut symbiont Bacteroides intestinalis, confirming previous in silico predictions of the likely host. DNA sequencing demonstrates that the bacteriophage genome is circular, 102 kb in size, and has unusual structural traits. In addition, electron microscopy confirms that ΦcrAss001 has a podovirus-like morphology. Despite the absence of obvious lysogeny genes, ΦcrAss001 replicates in a way that does not disrupt proliferation of the host bacterium, and is able to maintain itself in continuous host culture during several weeks
IMPACT: The Journal of the Center for Interdisciplinary Teaching and Learning. Volume 9, Issue 1, Winter 2020
Explicitly established to foreground interdisciplinary teaching and learning, Impact also welcomes evidence and
discussion of experiential learning. Often the two – interdisciplinary teaching and experiential learning – co-exist. Yet
even when they do not, both practices model how to think in myriad ways and to notice how knowledge is constructed.
As our winter 2019 issue makes clear, interdisciplinary teaching and learning and experiential learning often begin with
questions. Why does it matter that students grapple directly with archival material? What happens when undergraduates
practice psychology by training dogs? Do students understand financial literacy? This issue also asks questions about
students’ reading habits and faculty expectations of them as readers
A rotating cavity for high-field angle-dependent microwave spectroscopy of low-dimensional conductors and magnets
The cavity perturbation technique is an extremely powerful method for
measuring the electrodynamic response of a material in the millimeter- and
sub-millimeter spectral range (10 GHz to 1 THz), particularly in the case of
high-field/frequency magnetic resonance spectroscopy. However, the application
of such techniques within the limited space of a high-field magnet presents
significant technical challenges. We describe a 7.62 mm x 7.62 mm (diameter x
length) rotating cylindrical cavity which overcomes these problems.Comment: 11 pages including 8 figure
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