2,926 research outputs found
Solar energy conversion
If solar energy is to become a practical alternative to fossil fuels, we must have efficient ways to convert photons into electricity, fuel, and heat. The need for better conversion technologies is a driving force behind many recent developments in biology, materials, and especially nanoscience
Non-renormalization conditions for four-gluon scattering in supersymmetric string and field theory
The constraints imposed by maximal supersymmetry on multi-loop contributions
to the scattering of four open superstrings in the U(N) theory are examined by
use of the pure spinor formalism. The double-trace term k^2 t_8(tr F^2)^2
(where k represents an external momentum and F the Yang--Mills field strength)
only receives contributions from L<=2 (where L is the loop number) while the
single-trace term k^2 t_8(tr F^4) receives contributions from all L. We
verified these statements up to L=5, but arguments based on supersymmetry
suggest they extend to all L. This explains why the single-trace contributions
to low energy maximally supersymmetric Yang--Mills field theory are more
divergent in the ultraviolet than the double-trace contributions. We also
comment further on the constraints on closed string amplitudes and their
implications for ultraviolet divergences in N=8 supergravity.Comment: 25 pages. 2 eps figures. Harvmac format. v2 qualifications regarding
comments on closed strings. References adde
Off-shell Supersymmetry versus Hermiticity in the Superstring
We point out that off-shell four-dimensional supersymmetry implies strange
hermiticity properties for the N=1 RNS superstring. However, these hermiticity
properties become natural when the N=1 superstring is embedded into an N=2
superstring.Comment: 4 pages harvma
The hidden burden of adult allergic rhinitis : UK healthcare resource utilisation survey
Funding Funding for this survey was provided by Meda Pharma.Peer reviewedPublisher PD
High-frequency performance of scaled carbon nanotube array field-effect transistors
We report the radio-frequency performance of carbon nanotube array
transistors that have been realized through the aligned assembly of highly
separated, semiconducting carbon nanotubes on a fully scalable device platform.
At a gate length of 100 nm, we observe output current saturation and obtain
as-measured, extrinsic current gain and power gain cut-off frequencies,
respectively, of 7 GHz and 15 GHz. While the extrinsic current gain is
comparable to the state-of-the-art the extrinsic power gain is improved. The
de-embedded, intrinsic current gain and power gain cut-off frequencies of 153
GHz and 30 GHz are the highest values experimentally achieved to date. We
analyze the consistency of DC and AC performance parameters and discuss the
requirements for future applications of carbon nanotube array transistors in
high-frequency electronics.Comment: 15 pages, 4 figures + Supplementary Informatio
Exactly Marginal Deformations and Global Symmetries
We study the problem of finding exactly marginal deformations of N=1
superconformal field theories in four dimensions. We find that the only way a
marginal chiral operator can become not exactly marginal is for it to combine
with a conserved current multiplet. Additionally, we find that the space of
exactly marginal deformations, also called the "conformal manifold," is the
quotient of the space of marginal couplings by the complexified continuous
global symmetry group. This fact explains why exactly marginal deformations are
ubiquitous in N=1 theories. Our method turns the problem of enumerating exactly
marginal operators into a problem in group theory, and substantially extends
and simplifies the previous analysis by Leigh and Strassler. We also briefly
discuss how to apply our analysis to N=2 theories in three dimensions.Comment: 23 pages, 2 figure
Allergic Rhinitis and its Associated Co-Morbidities at Bugando Medical Centre in Northwestern Tanzania; A Prospective Review of 190 Cases.
Allergic rhinitis is one of the commonest atopic diseases which contribute to significant morbidity world wide while its epidemiology in Tanzania remains sparse. There was paucity of information regarding allergic rhinitis in our setting; therefore it was important to conduct this study to describe our experience on allergic rhinitis, associated co-morbidities and treatment outcome in patients attending Bugando Medical Centre. This was descriptive cross-sectional study involving all patients with a clinical diagnosis of allergic rhinitis at Bugando Medical Centre over a three-month period between June 2011 and August 2011. Data was collected using a pre-tested coded questionnaire and analyzed using SPSS statistical computer software version 17.0. A total of 190 patients were studied giving the prevalence of allergic rhinitis 14.7%. The median age of the patients was 8.5 years. The male to female ratio was 1:1. Adenoid hypertrophy, tonsillitis, hypertrophy of inferior turbinate, nasal polyps, otitis media and sinusitis were the most common co-morbidities affecting 92.6% of cases and were the major reason for attending hospital services. Sleep disturbance was common in children with adenoids hypertrophy (χ2 = 28.691, P = 0.000). Allergic conjunctivitis was found in 51.9%. The most common identified triggers were dust, strong perfume odors and cold weather (P < 0.05). Strong perfume odors affect female than males (χ2 = 4.583, P = 0.032). In this study family history of allergic rhinitis was not a significant risk factor (P =0.423). The majority of patients (68.8%) were treated surgically for allergic rhinitis co morbidities. Post operative complication and mortality rates were 2.9% and 1.6% respectively. The overall median duration of hospital stay of in-patients was 3 days (2 - 28 days). Most patients (98.4%) had satisfactory results at discharge. The study shows that allergic rhinitis is common in our settings representing 14.7% of all otorhinolaryngology and commonly affecting children and adolescent. Sufferers seek medical services due to co-morbidities of which combination of surgical and medical treatment was needed. High index of suspicions in diagnosing allergic rhinitis and early treatment is recommended
Lipopolysaccharides of brucella abortus and brucella melitensis induce nitric oxide synthesis in rat peritoneal macrophages
Producción CientíficaSmooth lipopolysaccharide (S-LPS) and lipid A of Brucella abortus and Brucella melitensis induced the
production of nitric oxide (NO) by rat adherent peritoneal cells, but they induced lower levels of production
of NO than Escherichia coli LPS. The participation of the inducible isoform of NO synthase (iNOS) was
confirmed by the finding of an increased expression of both iNOS mRNA and iNOS protein. These observations
might help to explain (i) the acute outcome of Brucella infection in rodents, (ii) the low frequency of septic
shock in human brucellosis, and (iii) the prolonged intracellular survival of Brucella in humans.This work was supported by (grants FIS 96/1017, SAF96-0144, and SAF98-0176
Developing Advanced Practitioners in Mental Health Social Work : Pedagogical Considerations
Advanced social work practitioners in mental health services daily face the challenges of working alongside the more powerful professions of psychiatry and psychology. Advanced post-qualifying programmes in mental health social work equip practitioners with the knowledge, skills and expertise to confidently work alongside both psychiatrists and clinical psychologists in multi-disciplinary teams. This includes training in empirical research methods, which are used to develop the evidence base for psychiatry and psychology, although social work practitioners find this particularly challenging. This paper explores the importance of research methods teaching in the development of advanced practitioners in mental health social work. Using learning theory to explore possible reasons why practitioners find it so difficult, it offers some solutions which may enhance the learning and teaching of research methodology to experienced social worker
- …