4,589 research outputs found
AdS4 backgrounds with N>16 supersymmetries in 10 and 11 dimensions
We explore all warped backgrounds with the most
general allowed fluxes that preserve more than 16 supersymmetries in -
and -dimensional supergravities. After imposing the assumption that either
the internal space is compact without boundary or the isometry
algebra of the background decomposes into that of AdS and that of
, we find that there are no such backgrounds in IIB supergravity.
Similarly in IIA supergravity, there is a unique such background with 24
supersymmetries locally isometric to , and in
supergravity all such backgrounds are locally isometric to the maximally
supersymmetric solution.Comment: 53 pages. v2: minor changes and references added. v3: typos corrected
and minor footnote added, published versio
Selection of medical students - a follow-up study
The attributes of 1026 medical students admitted to university on academic criteria and by interview between 1980 and 1983, and the characteristics of 822 of them who graduated between 1985 and 1988, were analysed. There were 133 students (13%) who failed and were excluded, 99 (10%) repeated 1 or more years of study, 67 (7%) voluntarily withdrew, 42 (4%) completed a Bsc. degree during their medical training, and 675 graduated in the minimum' time. The admitted and graduated students were mainly white (85%), male (67%) and had no academic experience other than matriculation (69%). During the review period the proportion of 'non-whites', women and applicants with university experience increased. Students who voluntarily withdrew had significantly low interview scores; applicants with university experience and applicants who subsequently failed. had significanUy high interview scores. It is concluded that the interview is useful, that the demographic characteristics of the classes are changing, and that traditional academic standards have been maintained
A non-existence theorem for N>16 supersymmetric AdS3 backgrounds
We show that there are no smooth warped AdS solutions in 10- and
11-dimensional supergravities which preserve strictly more than 16
supersymmetries and have internal space a compact without boundary manifold.Comment: 50 page
Anomalous suppression of the shot noise in a nanoelectromechanical system
In this paper we report a relaxation-induced suppression of the noise for a
single level quantum dot coupled to an oscillator with incoherent dynamics in
the sequential tunneling regime. It is shown that relaxation induces
qualitative changes in the transport properties of the dot, depending on the
strength of the electron-phonon coupling and on the applied voltage. In
particular, critical thresholds in voltage and relaxation are found such that a
suppression below 1/2 of the Fano factor is possible. Additionally, the current
is either enhanced or suppressed by increasing relaxation, depending on bias
being greater or smaller than the above threshold. These results exist for any
strength of the electron-phonon coupling and are confirmed by a four states toy
model.Comment: 7 pages, 7 eps figures, submitted to PRB; minor changes in the
introductio
Topotecan-vincristine-doxorubicin in stage 4 high risk neuroblastoma patients failing to achieve a complete metastatic response to rapid COJEC : a SIOPEN study
Purpose : Metastatic response to induction therapy for high-risk neuroblastoma is a prognostic factor. In the International Society of Paediatric Oncology Europe Neuroblastoma (SIOPEN) HR-NBL-1 protocol, only patients with metastatic complete response (CR) or partial response (PR) with <= three abnormal skeletal areas on iodine 123-metaiodobenzylguanidine ([I-123] mIBG) scintigraphy and no bone marrow disease proceed to high dose therapy (HDT). In this study, topotecan-vincristine-doxorubicin (TVD) was evaluated in patients failing to achieve these criteria, with the aim of improving the metastatic response rate.
Materials and Methods : Patients with metastatic high-risk neuroblastoma who had not achieved the SIOPEN criteria for HDT after induction received two courses of topotecan 1.5 mg/m(2)/day for 5 days, followed by a 48-hour infusion of vincristine, 2 mg/m(2), and doxorubicin, 45 mg/m(2).
Results : Sixty-three patients were eligible and evaluable. Following two courses of TVD, four (6.4%) patients had an overall CR, while 28 (44.4%) had a PR with a combined response rate of 50.8% (95% confidence interval [CI], 37.9 to 63.6). Of these, 23 patients achieved a metastatic CR or a PR with <= 3 mIBG skeletal areas and no bone marrow disease (36.5%; 95% CI, 24.7 to 49.6) and were eligible to receive HDT. Toxicity was mostly haematological, affecting 106 of the 126 courses (84.1%; 95% CI, 76.5 to 90.0), and dose reduction was necessary in six patients. Stomatitis was the second most common nonhematological toxicity, occurring in 20 patients (31.7%).
Conclusion : TVD was effective in improving the response rate of high-risk neuroblastoma patients after induction with COJEC enabling them to proceed to HDT. However, the long-term benefits of TVD needs to be determined in randomized clinical trials
A rapid-screening approach to detect and quantify microplastics based on fluorescent tagging with Nile Red
A new approach is presented for analysis of microplastics in environmental samples, based on selective fluorescent staining using Nile Red (NR), followed by density-based extraction and filtration. The dye adsorbs onto plastic surfaces and renders them fluorescent when irradiated with blue light. Fluorescence emission is detected using simple photography through an orange filter. Image-analysis allows fluorescent particles to be identified and counted. Magnified images can be recorded and tiled to cover the whole filter area, allowing particles down to a few micrometres to be detected. The solvatochromic nature of Nile Red also offers the possibility of plastic categorisation based on surface polarity characteristics of identified particles. This article details the development of this staining method and its initial cross-validation by comparison with infrared (IR) microscopy. Microplastics of different sizes could be detected and counted in marine sediment samples. The fluorescence staining identified the same particles as those found by scanning a filter area with IR-microscopy
A systematic review of the scientifically demonstrated effects of densification
One of the current dominant strategies proposed for sustainable urban development is densification. UN Habitat prescribes a density of over 150 inhabitants per hectare to realize the UN Sustainable Development Goals. While some authors advocate the very reasonable benefits of density, others emphasize the potential drawbacks. The main goal of this paper is to provide a systematic review of international research on urban density and its potential benefits and drawbacks for sustainable urban development. 1208 articles were selected from Web of Science and after the screening of abstracts, 330 papers were found eligible to be included in the quantitative synthesis. Results show that the effects of densification that dominate literature are transport related studies (41%), followed by studies focusing on economics (14%), social effects (12%) and human health (11%). Least studied effects are resource efficiency (1%), service (3%) and urban environment (4%). Positive correlations with higher density are reported for transport and economics, while ecology, social impact and health show mainly negative correlations with higher density. The findings reported are generic as similar trends are found in North America, Asia and Europe and only minor differences in outcome are found in studies using different measures of density, unit or scale of analysis
Mechanism-controlled thermomechanical treatment of high manganese steels
Austenitic high manganese steels exhibit outstanding mechanical properties, such as high energy absorption, owing to various deformation-mechanisms such as dislocation slip, twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP). Here, we show a novel thermomechanical treatment to manufacture a high manganese steel Fe–18Mn-0.3C (wt.-%) with excellent mechanical performance by combining these three deformation-mechanisms. This process of mechanism-controlled rolling resulted in ultra-high tensile strength of the high manganese steel up to 1.6 GPa, simultaneously with uniform elongations up to 15%.A thermomechanical process was developed to establish this combination of properties. Warm rolling was conducted at 200 °C, to suppress TRIP and activate TWIP as deformation mechanism. Thus, a high density of deformation twins and dislocations was introduced to the microstructure, avoiding martensite formation. During a subsequent recovery annealing at 520 °C or 550 °C, the dislocation density was reduced, yet the high density of deformation twins was preserved. The combination of warm rolling and recovery annealing resulted in an ultrafine microstructure with a high density of twins and moderate density of dislocations. The TRIP effect is predominant during plastic deformation at ambient conditions in the highly twinned microstructure. The resulting steel exhibits an ultra-high yield strength and sufficient ductility, favorable properties for lightweight construction in automotive or aerospace industry
A systematic review of motives for densification in Swedish planning practice
One of the current dominant strategies proposed for sustainable urban development is densification. While some advocate the very reasonable benefits of density, others emphasize the potential drawbacks. The main goal of this paper is to provide a systematic overview of the claimed benefits of densification in Swedish practice and relate this to the scientific evidence. For the systematic overview, comprehensive plans from 59 Swedish municipalities, covering plans from both highly urbanized areas as well as more rural regions, are included. The results show that in three out of four cases where density or densification is mentioned, no motive is given. For the other quarter, the most often used motivation is related to transport (19%), services (17%) and urban environmental qualities (14%). The least frequent motives used are related to health (8%) and ecology (2%). The motives in comprehensive plans are for the most part pointing to a positive impact of density on sustainable urban development (77%), which is not always supported by the empirical evidence that more often describe a negative correlation. Furthermore, many of the most frequently used motives in comprehensive plans have little scientific support, which puts new questions on the research agenda
A conceptual framework and exploratory model for health and social intervention acceptability among African adolescents and youth
Intervention acceptability has become an increasingly key consideration in the development, evaluation and implementation of health and social interventions. However, to date this area of investigation has been constrained by the absence of a consistent definition of acceptability, comprehensive conceptual frameworks disaggregating its components, and few reliable assessment measures. This paper aims to contribute to this gap, by proposing a conceptual framework and exploratory model for acceptability with a specific priority population for health and developmental interventions: adolescents and youth in Africa. We document our multi-staged approach to model development, comprising both inductive and deductive components, and both systematic and interpretative review methods. This included thematic analyses of respective acceptability definitions and findings, from 55 studies assessing acceptability of 60 interventions conducted with young people aged 10–24 in (mainly Southern and Eastern) Africa over a decade; a consideration of these findings in relation to Sekhon et al.‘s Theoretical Framework of Acceptability (TFA); a cross-disciplinary review of acceptability definitions and models; a review of key health behavioural change models; and expert consultation with interdisciplinary researchers. Our proposed framework incorporates nine component constructs: affective attitude, intervention understanding, perceived positive effects, relevance, perceived social acceptability, burden, ethicality, perceived negative effects and self-efficacy. We discuss the rationale for the inclusion and definition of each component, highlighting key behavioural models that adopt similar constructs. We then extend this framework to develop an exploratory model for acceptability with young people, that links the framework components to each other and to intervention engagement. Acceptability is represented as an emergent property of a complex, adaptive system of interacting components, which can influence user engagement directly and indirectly, and in turn be influenced by user engagement. We discuss opportunities for applying and further refining or developing these models, and their value as a point of reference for the development of acceptability assessment tools
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