2,583 research outputs found
Contribution of the nucleon-hyperon reaction channels to K production in proton-nucleus collisions
The cross sections for producing K mesons in nucleon-hyperon elementary
processes are estimated assuming one-pion exchange and using the experimentally
known pion-hyperon cross sections. The results are implemented in a transport
model which is applied to calculation of proton-nucleus collisions. In
significant difference to earlier estimates for heavy-ion collisions the
inclusion of the nucleon-hyperon cross section roughly doubles the K
production in near-threshold proton-nucleus collisions
Co-regularised support vector regression
We consider a semi-supervised learning scenario for regression, where only few labelled examples, many unlabelled instances and different data representations (multiple views) are available. For this setting, we extend support vector regression with a co-regularisation term and obtain co-regularised support vector regression (CoSVR). In addition to labelled data, co-regularisation includes information from unlabelled examples by ensuring that models trained on different views make similar predictions. Ligand affinity prediction is an important real-world problem that fits into this scenario. The characterisation of the strength of protein-ligand bonds is a crucial step in the process of drug discovery and design. We introduce variants of the base CoSVR algorithm and discuss their theoretical and computational properties. For the CoSVR function class we provide a theoretical bound on the Rademacher complexity. Finally, we demonstrate the usefulness of CoSVR for the affinity prediction task and evaluate its performance empirically on different protein-ligand datasets. We show that CoSVR outperforms co-regularised least squares regression as well as existing state-of-the-art approaches for affinity prediction
Effects of next-nearest-neighbor hopping on the electronic structure of cuprates
Photoemission spectra of underdoped and lightly-doped
BiPbSrCa{\it R}CuO ( Pr, Er)
(BSCCO) have been measured and compared with those of LaSrCuO
(LSCO). The lower-Hubbard band of the insulating BSCCO, like
CaCuOCl, shows a stronger dispersion than LaCuO from () to (). The flat band at () is found generally deeper in BSCCO. These observations
together with the Fermi-surface shapes and the chemical potential shifts
indicate that the next-nearest-neighbor hopping of the
single-band model is larger in BSCCO than in LSCO and that
rather than the super-exchange influences the pseudogap energy scale.Comment: 5 pages,4 figures, 1 tabl
Avaliação da avifauna em sistemas agroflorestais com dendê (Elaeis guianeensis) no município de Tomé-Açu (PA).
È apresentada uma comparação entre a composição da avifauna de sistemas agroflorestais (SAF) com dendê, copoeiras e uma monocultura de dendê ao longo de dois anos no intuito de relatar a funcionalidade dos SAFs na manutenção de aves amazônicas. Foram registradas 196 espécies, destas 88 encontradas nos SAFs, 120 na capoeira e 63 na monocultura. Foi observada a ausência de espécies florestais das famílias, Thamnophilidae, Furnaridae e Tyrannidae no SAF e na monocultura de dendê, presentes na capoeira. O índice de similaridade de Morisita mostra que os SAFs se assemelham mais às monoculturas do que às capoeiras, possivelmente devido ao tempo recente de plantio, onde os SAFs ainda não apresentam uma estrutura florestal mais complexa com sub-bosque e dossel. Foi observado um aumento na riqueza de espécies frutívoras e nectarívoras e na diversidade dos SAFs, possivelmente refletindo o contínuo desenvolvimento e estruturação deste sistema. Os resultados apresentados mostram que apesar de os SAFs apresentarem uma comunidade de aves em geral distinta da comunidade encontrada nas capoeiras, estas apresentam índices de diversidade e riqueza de espécies semelhantes. A monocultura de dendê apresentou a menor riqueza e índices de diversidade, além de apresentar principalmente espécies insetívoras, onívoras e granívoras na composição de sua avifauna, configurando um ambiente pouco diverso na estrutura da vegetação. Sistemas agroflorestais de dendê podem vir a contribuir na manutenção da diversidade local de aves florestais amazônicas, contudo os resultados apontam a necessidade de mais tempo para um melhor desenvolvimento do sistema.Editores técnicos: Roberto Porro, Milton Kanashiro, Maria do Socorro Gonçalves Ferreira, Leila Sobral Sampaio e Gladys Ferreira de Sousa
Target mass number dependence of subthreshold antiproton production in proton-, deuteron- and alpha-particle-induced reactions
Data from KEK on subthreshold \bar{\mrm{p}} as well as on and
\mrm{K}^\pm production in proton-, deuteron- and -induced reactions
at energies between 2.0 and 12.0 A GeV for C, Cu and Pb targets are described
within a unified approach. We use a model which considers a nuclear reaction as
an incoherent sum over collisions of varying numbers of projectile and target
nucleons. It samples complete events and thus allows for the simultaneous
consideration of all final particles including the decay products of the
nuclear residues. The enormous enhancement of the \bar{\mrm{p}} cross
section, as well as the moderate increase of meson production in deuteron and
induced compared to proton-induced reactions, is well reproduced for
all target nuclei. In our approach, the observed enhancement near the
production threshold is mainly due to the contributions from the interactions
of few-nucleon clusters by simultaneously considering fragmentation processes
of the nuclear residues. The ability of the model to reproduce the target mass
dependence may be considered as a further proof of the validity of the cluster
concept.Comment: 9 pages, 4 figure
Influenza-Related Mortality Trends in Japanese and American Seniors: Evidence for the Indirect Mortality Benefits of Vaccinating Schoolchildren
Background: The historical Japanese influenza vaccination program targeted at schoolchildren provides a unique opportunity to evaluate the indirect benefits of vaccinating high-transmitter groups to mitigate disease burden among seniors. Here we characterize the indirect mortality benefits of vaccinating schoolchildren based on data from Japan and the US.
Methods: We compared age-specific influenza-related excess mortality rates in Japanese seniors aged $65 years during the schoolchildren vaccination program (1978–1994) and after the program was discontinued (1995–2006). Indirect vaccine benefits were adjusted for demographic changes, socioeconomics and dominant influenza subtype; US mortality data were used as a control. Results: We estimate that the schoolchildren vaccination program conferred a 36% adjusted mortality reduction among Japanese seniors (95%CI: 17–51%), corresponding to ,1,000 senior deaths averted by vaccination annually (95%CI: 400– 1,800). In contrast, influenza-related mortality did not change among US seniors, despite increasing vaccine coverage in this population.
Conclusions: The Japanese schoolchildren vaccination program was associated with substantial indirect mortality benefits in seniors
Measuring Temperature Gradients over Nanometer Length Scales
When a quantum dot is subjected to a thermal gradient, the temperature of
electrons entering the dot can be determined from the dot's thermocurrent if
the conductance spectrum and background temperature are known. We demonstrate
this technique by measuring the temperature difference across a 15 nm quantum
dot embedded in a nanowire. This technique can be used when the dot's energy
states are separated by many kT and will enable future quantitative
investigations of electron-phonon interaction, nonlinear thermoelectric
effects, and the effciency of thermoelectric energy conversion in quantum dots.Comment: 6 pages, 5 figure
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