Minimum Bias and Underlying Event Measurements with ATLAS

A summary of some of the recent minimum bias and underlying event measurements by the ATLAS collaboration is given. The results of several analyses using low-luminosity proton-proton collision data from the LHC taken at center-of-mass energies of sqrt(s) = 0.9, 2.36 and 7 TeV are presented. Data are compared to predictions by several different Monte Carlo event generators. The measurements expose limitations of the phenomenological models in properly describing the measured observables in all regions of phase space.Comment: 9 pages, 5 figures, 1 table; Proceedings for the 3rd Workshop on Multiple-Partonic Interactions at the LHC, Hamburg, Germany, November 201

Antiresonant quantum transport in ac driven molecular nanojunctions

(Dated: July 17, 2017) We calculate the electric charge current flowing through a vibrating molecular nanojunction, which is driven by an ac voltage, in its regime of nonlinear oscillations. Without loss of generality, we model the junction by a vibrating molecule which is doubly clamped to two metallic leads which are biased by time-periodic ac voltages. Dressed-electron tunneling between the leads and the molecule drives the mechanical degree of freedom out of equilibrium. In the deep quantum regime, where only a few vibrational quanta are excited, the formation of coherent vibrational resonances affects the dressed-electron tunneling. In turn, back action modifies the electronic ac current passing through the junction. The concert of nonlinear vibrations and ac driving induces quantum transport currents which are antiresonant to the applied ac voltage. Quantum back action on the flowing nonequilibriun current allows us to obtain rather sharp spectroscopic information on the population of the mechanical vibrational states.Comment: 12 pages, 3 figures; replaced with accepted versio

Exploring the hidden interior of the Earth with directional neutrino measurements

Roughly 40% of the Earth's total heat flow is powered by radioactive decays in the crust and mantle. Geo-neutrinos produced by these decays provide important clues about the origin, formation and thermal evolution of our planet, as well as the composition of its interior. Previous measurements of geo-neutrinos have all relied on the detection of inverse beta decay reactions, which are insensitive to the contribution from potassium and do not provide model-independent information about the spatial distribution of geo-neutrino sources within the Earth. Here we present a method for measuring previously unresolved components of Earth's radiogenic heating using neutrino-electron elastic scattering and low-background, direction-sensitive tracking detectors. We calculate the exposures needed to probe various contributions to the total geo-neutrino flux, specifically those associated to potassium, the mantle and the core. The measurements proposed here chart a course for pioneering exploration of the veiled inner workings of the Earth.Comment: 18 pages, 11 figures, 8 table

Photon-assisted confinement-induced resonances for ultracold atoms

We solve the two-particle s-wave scattering for an ultracold atom gas confined in a quasi-one-dimensional trapping potential which is periodically modulated. The interaction between the atoms is included in terms of Fermi's pseudopotential. For a modulated isotropic transverse harmonic confinement, the atomic center of mass and relative degrees of freedom decouple and an exact solution is possible. We use the Floquet approach to show that additional photon-assisted resonant scattering channels open up due to the harmonic modulation. Applying the Bethe-Peierls boundary condition, we obtain the general scattering solution of the time-dependent Schr\"odinger equation which is universal at low energies. The binding energies and the effective one-dimensional scattering length can be controlled by the external driving

Geometry as Transfer

It is generally accepted that intelligent action involves considerable use of transfer. For example, Carbonell [1] has argued that learning proceeds by analogical reasoning; Rosch [12] has argued that categorization proceeds by seeing objects in terms of prototypes; and Leyton [9] has argued that the human perceptual system is organized as a hierarchy of transfer. The role of geometry is also seen as fundamental to the representations produced by the cognitive system. For example, Gallistel [2] has elaborated the powerful role of geometry in animal learning and navigation; Lakoff [3] has emphasized the role of geometry in semantics; and Leyton [9] has proposed an extensive role for geometry in causal explanation. We bring together the two above factors, transfer and geometry, in the book, Leyton [10], by developing a generative theory of shape in which transfer is a fundamental organizing principle. In this approach, transfer is basic to the very meaning of geometry. The purpose of the present paper is to give an introduction to this transfer-based theory of geometry

Implementación de aisladores sísmicos en un edificio de viviendas en Lima, Perú

En la actualidad, los sistemas de protección sísmica representan una opción viable para la prevención de desastres naturales como lo es un evento telúrico. Nuestro país se encuentra en la zona del cinturón de fuego del pacífico, por lo tanto no se debe hacer caso omiso al peligro que un sismo supone. En atención a ello, se presenta el siguiente estudio que intentará explicar, a grandes rasgos, una tecnología de protección sísmica: la implementación de aisladores en un edificio de viviendas. Es recurrente que el público en general, e inclusive ingenieros civiles, tengan interrogantes sobre el comportamiento, tipos, eficiencia y conveniencia de los distintos tipos de aisladores sísmicos. Por tal motivo, este estudio fue estructurado para describir la tecnología desde los principios básicos y la filosofía del diseño, hasta los mecanismos de protección y propiedades dinámicas de cada uno de los dispositivos. La información técnica mostrada corresponde a estándares internacionales, normativa local y prácticas comunes de la ingeniería estructural y construcción. Complementario a la información teórica, se plantea una comparación entre la propuesta ya construida y su similar con aisladores en una edificación de viviendas de varios niveles. Se ha seleccionado para el ejercicio un edificio multifamiliar típico del distrito de San Isidro, en la ciudad de Lima: dos sótanos y siete niveles de viviendas, incluyendo la azotea. La directriz general que se siguió, para realizar la propuesta con aisladores, fue la de restructurar la edificación con la idea de ahorrar en materiales de construcción y compensar, así, el sobrecosto por el concepto de aisladores. Al mismo tiempo, se mantuvo la arquitectura original y la funcionalidad de las viviendas. Finalmente, se resumen los resultados de los análisis de estructuras, de acuerdo a norma, y se presentan los costos de construcción asociados, junto con los beneficios del aislamiento sísmico, para comparar la conveniencia de su implementación en el ejercicio mostrado.Tesi

Longitudinal change in everyday function and behavioral symptoms in frontotemporal dementia

Background: The relationship between behavioral changes and functional decline in frontotemporal dementia (FTD) is not well understood. Methods: Thirty-nine patients (21 behavioral variant FTD [bvFTD], 18 semantic variant primary progressive aphasia [svPPA]) were followed up longitudinally (2–4 years follow-up). Functional (Disability Assessment for Dementia) and behavioral (Cambridge Behavioural Inventory Revised) assessments were included for between-group (pairwise comparisons, mixed model analysis) and within-group analyses (bivariate correlations). Results: Functionally, patients with bvFTD were more impaired than patients with svPPA at baseline and continued to be at follow-up, despite similar disease duration. By contrast, behavioral impairments differed between patient groups at baseline and at follow-up. At baseline, patients with bvFTD exhibited higher levels of apathy and changes in eating than patients with svPPA; disinhibited and stereotypical behaviors were similar. Over the years, patients with bvFTD showed reduction in disinhibition and stereotypical behavior while apathy and eating changes increased. By contrast, all measured behaviors increased in patients with svPPA over time. Finally, only apathy made longitudinal contributions to functional disability in patients with svPPA, whereas apathy and stereotypical behavior were associated with increased disability in patients with bvFTD. Conclusions: Despite shared overlapping baseline behavioral symptoms, patients with bvFTD are more functionally impaired than patients with svPPA. Apathy has a strong role in disability for both bvFTD and svPPA, but stereotypical behaviors only contributed to functional deficits in patients with bvFTD. Our findings suggest that rigid/compulsive behaviors may in fact support activity engagement in patients with svPPA. Taken together, our results indicate that interventions to reduce disability in the FTD spectrum require an alternative rationale in comparison to Alzheimer disease dementia, and should carefully weigh the interaction of behavioral symptoms and functional status

Size and conformation limits to secretion of disulfide-bonded loops in autotransporter proteins

Autotransporters are a superfamily of virulence factors typified by a channel-forming C terminus that facilitates translocation of the functional N-terminal passenger domain across the outer membrane of Gram-negative bacteria. This final step in the secretion of autotransporters requires a translocation-competent conformation for the passenger domain that differs markedly from the structure of the fully folded secreted protein. The nature of the translocation-competent conformation remains controversial, in particular whether the passenger domain can adopt secondary structural motifs, such as disulfide- bonded segments, while maintaining a secretion-competent state. Here, we used the endogenous and closely spaced cysteine residues of the plasmid-encoded toxin (Pet) from enteroaggregative Escherichia coli to investigate the effect of disulfide bond-induced folding on translocation of an auto-transporter passenger domain. We reveal that rigid structural elements within disulfide-bonded segments are resistant to autotransporter-mediated secretion. We define the size limit of disulfide-bonded segments tolerated by the autotransporter system demonstrating that, when present, cysteine pairs are intrinsically closely spaced to prevent congestion of the translocator pore by large disulfide-bonded regions. These latter data strongly support the hairpin mode of autotransporter biogenesis

Measurement of the directional sensitivity of Dark Matter Time Projection Chamber detectors

The Dark Matter Time Projection Chamber (DMTPC) is a direction-sensitive detector designed to measure the direction of recoiling $^{19}$F and $^{12}$C nuclei in low-pressure CF$_4$ gas using optical and charge readout systems. In this paper, we employ measurements from two DMTPC detectors, with operating pressures of 30-60 torr, to develop and validate a model of the directional response and performance of such detectors as a function of recoil energy. Using our model as a benchmark, we formulate the necessary specifications for a scalable directional detector with sensitivity comparable to that of current-generation counting (non-directional) experiments, which measure only recoil energy. Assuming the performance of existing DMTPC detectors, as well as current limits on the spin-dependent WIMP-nucleus cross section, we find that a 10-20 kg scale direction-sensitive detector is capable of correlating the measured direction of nuclear recoils with the predicted direction of incident dark matter particles and providing decisive (3$\sigma$) confirmation that a candidate signal from a non-directional experiment was indeed induced by elastic scattering of dark matter particles off of target nuclei.Comment: 13 pages, 10 figures. Accepted for publication in Phys. Rev. D. Added color figures, switched to more compact layout, and fixed some reference