745 research outputs found
Ultra-High Energy Neutrino-Nucleon Scattering and Parton Distributions at Small
The cross section for ultra-high energy neutrino-nucleon scattering is very
sensitive to the parton distributions at very small values of Bjorken x (. We numerically investigate the effects of modifying the
behavior of the gluon distribution function at very small in the DGLAP
evolution equation. We then use the Color Glass Condensate formalism to
calculate the neutrino-nucleon cross section at ultra-high energies and compare
the result with those based on modification of DGLAP evolution equation.Comment: 10 pages, 4 figures, INT-PUB-05-3
Double-illumination photoacoustic microscopy
Recent developments of optical-resolution photoacoustic microscopy (OR-PAM) have improved its spatial resolution and imaging speed. However, the penetration depth of OR-PAM is still limited to ∼1 mm in tissue, owing to the strong tissue scattering. Here, we have developed double-illumination PAM (DI-PAM), which illuminates the sample from both top and bottom sides simultaneously. Through phantom and in vivo experiments, we have demonstrated for thin targets that DI-PAM has a penetration depth of ∼2 mm in tissue at 532 nm and a focal zone of 260 μm, both significant improvements over traditional reflection or transmission-mode OR-PAM
Determination of water content in clay and organic soil using microwave oven
The article deals with the techniques of soil water content determination using microwave radiation. Its practical application would allow solving the problems of resource efficiency in geotechnical survey due to reduction of energy and resource intensity of laboratory analysis as well as its acceleration by means of decreasing labour intensity and, as a result, cost reduction. The article presents a detail analysis of approaches to soil water content determination and soil drying, considers its features and application. The study in soil of different composition, typical for Western Siberia including organic and organic-mineral ones, is a peculiarity of the given article, which makes it rather topical. The article compares and analyzes the results of the investigation into soil water content, which are obtained via conventional techniques and the original one developed by the authors, consisting in microwave drying. The authors also give recommendation on microwave technique application to dry soil
Double-illumination photoacoustic microscopy
Recent developments of optical-resolution photoacoustic microscopy (OR-PAM) have improved its spatial resolution and imaging speed. However, the penetration depth of OR-PAM is still limited to ∼1 mm in tissue, owing to the strong tissue scattering. Here, we have developed double-illumination PAM (DI-PAM), which illuminates the sample from both top and bottom sides simultaneously. Through phantom and in vivo experiments, we have demonstrated for thin targets that DI-PAM has a penetration depth of ∼2 mm in tissue at 532 nm and a focal zone of 260 μm, both significant improvements over traditional reflection or transmission-mode OR-PAM
Mathematical practice, crowdsourcing, and social machines
The highest level of mathematics has traditionally been seen as a solitary
endeavour, to produce a proof for review and acceptance by research peers.
Mathematics is now at a remarkable inflexion point, with new technology
radically extending the power and limits of individuals. Crowdsourcing pulls
together diverse experts to solve problems; symbolic computation tackles huge
routine calculations; and computers check proofs too long and complicated for
humans to comprehend.
Mathematical practice is an emerging interdisciplinary field which draws on
philosophy and social science to understand how mathematics is produced. Online
mathematical activity provides a novel and rich source of data for empirical
investigation of mathematical practice - for example the community question
answering system {\it mathoverflow} contains around 40,000 mathematical
conversations, and {\it polymath} collaborations provide transcripts of the
process of discovering proofs. Our preliminary investigations have demonstrated
the importance of "soft" aspects such as analogy and creativity, alongside
deduction and proof, in the production of mathematics, and have given us new
ways to think about the roles of people and machines in creating new
mathematical knowledge. We discuss further investigation of these resources and
what it might reveal.
Crowdsourced mathematical activity is an example of a "social machine", a new
paradigm, identified by Berners-Lee, for viewing a combination of people and
computers as a single problem-solving entity, and the subject of major
international research endeavours. We outline a future research agenda for
mathematics social machines, a combination of people, computers, and
mathematical archives to create and apply mathematics, with the potential to
change the way people do mathematics, and to transform the reach, pace, and
impact of mathematics research.Comment: To appear, Springer LNCS, Proceedings of Conferences on Intelligent
Computer Mathematics, CICM 2013, July 2013 Bath, U
Conceptual learning : the priority for higher education
The common sense notion of learning as the all-pervasive acquisition of new behaviour and knowledge, made vivid by experience, is an incomplete characterisation, because it assumes that the learning of behaviour and the learning of knowledge are indistinguishable, and that acquisition constitutes learning without reference to transfer. A psychological level of analysis is used to argue that conceptual learning should have priority in higher education
Genome-Wide Studies of Histone Demethylation Catalysed by the Fission Yeast Homologues of Mammalian LSD1
In order to gain a more global view of the activity of histone demethylases, we report here genome-wide studies of the fission yeast SWIRM and polyamine oxidase (PAO) domain homologues of mammalian LSD1. Consistent with previous work we find that the two S. pombe proteins, which we name Swm1 and Swm2 (after SWIRM1 and SWIRM2), associate together in a complex. However, we find that this complex specifically demethylates lysine 9 in histone H3 (H3K9) and both up- and down-regulates expression of different groups of genes. Using chromatin-immunoprecipitation, to isolate fragments of chromatin containing either H3K4me2 or H3K9me2, and DNA microarray analysis (ChIP-chip), we have studied genome-wide changes in patterns of histone methylation, and their correlation with gene expression, upon deletion of the swm1+ gene. Using hyper-geometric probability comparisons we uncover genetic links between lysine-specific demethylases, the histone deacetylase Clr6, and the chromatin remodeller Hrp1. The data presented here demonstrate that in fission yeast the SWIRM/PAO domain proteins Swm1 and Swm2 are associated in complexes that can remove methyl groups from lysine 9 methylated histone H3. In vitro, we show that bacterially expressed Swm1 also possesses lysine 9 demethylase activity. In vivo, loss of Swm1 increases the global levels of both H3K9me2 and H3K4me2. A significant accumulation of H3K4me2 is observed at genes that are up-regulated in a swm1 deletion strain. In addition, H3K9me2 accumulates at some genes known to be direct Swm1/2 targets that are down-regulated in the swm1¿ strain. The in vivo data indicate that Swm1 acts in concert with the HDAC Clr6 and the chromatin remodeller Hrp1 to repress gene expression. In addition, our in vitro analyses suggest that the H3K9 demethylase activity requires an unidentified post-translational modification to allow it to act. Thus, our results highlight complex interactions between histone demethylase, deacetylase and chromatin remodelling activities in the regulation of gene expression
Discriminating neutrino mass models using Type II seesaw formula
In this paper we propose a kind of natural selection which can discriminate
the three possible neutrino mass models, namely the degenerate, inverted
hierarchical and normal hierarchical models, using the framework of Type II
seesaw formula. We arrive at a conclusion that the inverted hierarchical model
appears to be most favourable whereas the normal hierarchical model follows
next to it. The degenerate model is found to be most unfavourable. We use the
hypothesis that those neutrino mass models in which Type I seesaw term
dominates over the Type II left-handed Higgs triplet term are favoured to
survive in nature.Comment: No change in the results, a few references added, some changes in
Type[IIB] calculation
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