1,826 research outputs found
Solving for Micro- and Macro- Scale Electrostatic Configurations Using the Robin Hood Algorithm
We present a novel technique by which highly-segmented electrostatic
configurations can be solved. The Robin Hood method is a matrix-inversion
algorithm optimized for solving high density boundary element method (BEM)
problems. We illustrate the capabilities of this solver by studying two
distinct geometry scales: (a) the electrostatic potential of a large volume
beta-detector and (b) the field enhancement present at surface of electrode
nano-structures. Geometries with elements numbering in the O(10^5) are easily
modeled and solved without loss of accuracy. The technique has recently been
expanded so as to include dielectrics and magnetic materials.Comment: 40 pages, 20 figure
Resonant inelastic x-ray scattering probes the electron-phonon coupling in the spin-liquid kappa-(BEDT-TTF)2Cu2(CN)3
Resonant inelastic x-ray scattering at the N K edge reveals clearly resolved
harmonics of the anion plane vibrations in the kappa-(BEDT-TTF)2Cu2(CN)3
spin-liquid insulator. Tuning the incoming light energy at the K edge of two
distinct N sites permits to excite different sets of phonon modes. Cyanide CN
stretching mode is selected at the edge of the ordered N sites which are more
strongly connected to the BEDT-TTF molecules, while positionally disordered N
sites show multi-mode excitation. Combining measurements with calculations on
an anion plane cluster permits to estimate the sitedependent electron-phonon
coupling of the modes related to nitrogen excitation
The mechanism of caesium intercalation of graphene
Properties of many layered materials, including copper- and iron-based
superconductors, topological insulators, graphite and epitaxial graphene can be
manipulated by inclusion of different atomic and molecular species between the
layers via a process known as intercalation. For example, intercalation in
graphite can lead to superconductivity and is crucial in the working cycle of
modern batteries and supercapacitors. Intercalation involves complex diffusion
processes along and across the layers, but the microscopic mechanisms and
dynamics of these processes are not well understood. Here we report on a novel
mechanism for intercalation and entrapment of alkali-atoms under epitaxial
graphene. We find that the intercalation is adjusted by the van der Waals
interaction, with the dynamics governed by defects anchored to graphene
wrinkles. Our findings are relevant for the future design and application of
graphene-based nano-structures. Similar mechanisms can also play a role for
intercalation of layered materials.Comment: 8 pages, 7 figures in published form, supplementary information
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The MATHUSLA Test Stand
The rate of muons from LHC collisions reaching the surface above the
ATLAS interaction point is measured and compared with expected rates from
decays of and bosons and - and -quark jets. In addition, data
collected during periods without beams circulating in the LHC provide a
measurement of the background from cosmic ray inelastic backscattering that is
compared to simulation predictions. Data were recorded during 2018 in a 2.5
2.5 6.5~ active volume MATHUSLA test stand detector
unit consisting of two scintillator planes, one at the top and one at the
bottom, which defined the trigger, and six layers of RPCs between them, grouped
into three -measuring layers separated by 1.74 m from each other.
Triggers selecting both upward-going tracks and downward-going tracks were
used.Comment: 18 pages, 11 figures, 1 tabl
What exactly is ‘N’ in cell culture and animal experiments?
Biologists determine experimental effects by perturbing biological entities or units. When done appropriately, independent replication of the entity-intervention pair contributes to the sample size (N) and forms the basis of statistical inference. If the wrong entity-intervention pair is chosen, an experiment cannot address the question of interest. We surveyed a random sample of published animal experiments from 2011 to 2016 where interventions were applied to parents and effects examined in the offspring, as regulatory authorities provide clear guidelines on replication with such designs. We found that only 22% of studies (95% CI = 17%-29%) replicated the correct entity-intervention pair and thus made valid statistical inferences. Nearly half of the studies (46%, 95% CI = 38%-53%) had pseudoreplication while 32% (95% CI = 26%-39%) provided insufficient information to make a judgement. Pseudoreplication artificially inflates the sample size, and thus the evidence for a scientific claim, resulting in false positives. We argue that distinguishing between biological units, experimental units, and observational units clarifies where replication should occur, describe the criteria for genuine replication, and provide concrete examples of in vitro, ex vivo, and in vivo experimental designs
Immune genotypes, immune responses, and survival in a wild bird population
ACKNOWLEDGEMENTS We thank the Tsawout and Tseycum bands for allowing us to conduct research on Mandarte Island, and to the many contributors to long-term monitoring, especially L. Keller, P. Nietlisbach, and J. Krippel. We also thank C. Ritland, A. Miscampbell, and G. Huber for their assistance in the laboratory. All work was conducted under permit of the Canadian Wildlife Service and UBC Animal Care Committee. Funding Information: This study was generously supported by the Natural Sciences and Engineering Research Council of Canada via a Post‐doctoral Fellowship award to MJNF (PDF‐2014–454522) and a Discovery Grant to EAMS.Peer reviewedPublisher PD
On the electromagnetic energy resolution of Cherenkov-fiber calorimeters
Electromagnetic calorimeters which sample the Cherenkov radiation of shower particles in optical fibers operate in a markedly different manner from calorimeters which rely on the dE/dx of shower particles. The well-understood physics of electromagnetic shower development is applied to the case of Cherenkov-fiber calorimetry (also known as quartz fiber calorimetry) and the results of systematically performed studies are considered in detail to derive an understanding of the critical parameters involved in energy measurement using such calorimeters. A quantitative parameterization of Cherenkov-fiber calorimetry electromagnetic energy resolution is proposed and compared with existing experimental results
The latent stem cell population is retained in the hippocampus of transgenic Huntington's disease mice but not wild-type mice
The demonstration of the brain's ability to initiate repair in response to disease or injury has sparked considerable interest in therapeutic strategies to stimulate adult neurogenesis. In this study we examined the effect of a progressive neurodegenerative condition on neural precursor activity in the subventricular zone (SVZ) and hippocampus of the R6/1 transgenic mouse model of Huntington's disease (HD). Our results revealed an age-related decline in SVZ precursor numbers in both wild-type (WT) and HD mice. Interestingly, hippocampal precursor numbers declined with age in WT mice, although we observed maintenance in hippocampal precursor number in the HD animals in response to advancement of the disease. This maintenance was consistent with activation of a recently identified latent hippocampal precursor population. We found that the small latent stem cell population was also maintained in the HD hippocampus at 33 weeks, whereas it was not present in the WT. Our findings demonstrate that, despite a loss of neurogenesis in the HD hippocampus in vivo, there is a unique maintenance of the precursor and stem cells, which may potentially be activated to ameliorate disease symptoms
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