Experimental validation of phase space conduits of transition between potential wells

A phase space boundary between transition and non-transition, similar to those observed in chemical reaction dynamics, is shown experimentally in a macroscopic system. We present a validation of the phase space flux across rank one saddles connecting adjacent potential wells and confirm the underlying phase space conduits that mediate the transition. Experimental regions of transition are found to agree with the theory to within 1\%, suggesting the robustness of phase space conduits of transition in a broad array of two or more degree of freedom experimental systems, despite the presence of small dissipation.Comment: 7 pages, 6 figure

Sanctuary or double-edged sword? Challenges confronting adolescents living at Nkosi’s Haven in Johannesburg, South Africa

Living in an institution associated with HIV and AIDS is likely to exacerbate difficulties experienced by teenagers who have to cope with the normal stresses of adolescence. The aim of the study was to explore the challenges that adolescents living at Nkosi’s Haven encounter and whether they experience any problems when interacting with their peers and other members of the community. The study was located within a qualitative research paradigm and utilised a purposive, non-probability sample of 15 participants recruited from two Nkosi’s Havens. A semi-structured interview schedule was employed as the research tool, with in-depth one-on-oneinterviews adopted as the method of data collection. Thematic content analysis was used to analyse the data collected during the interviews. The main finding that emanated from the study was that Nkosi’s Haven is indeed a place of care and nurturing as adolescents are afforded the opportunity to continue with their educational needs while basic and psychosocial needs are also addressed. However, it also emerged that rejection, discrimination, social exclusion and stigmatisation associated with the setting make it difficult for resident adolescents to integrate freely with their peers at school and in the community. The conclusion drawn is that Nkosi’s Haven can be regarded as a double-edged sword as it presents both positive and negative factors that impact on its resident adolescents. Results are discussed in terms of their implications for community awareness programmes, policies and practice changes regarding employment and training of staff, and visiting of parents as well as future research

Comparison of methods for estimating continuous distributions of relaxation times

The nonparametric estimation of the distribution of relaxation times approach is not as frequently used in the analysis of dispersed response of dielectric or conductive materials as are other immittance data analysis methods based on parametric curve fitting techniques. Nevertheless, such distributions can yield important information about the physical processes present in measured material. In this letter, we apply two quite different numerical inversion methods to estimate the distribution of relaxation times for glassy \lila\ dielectric frequency-response data at 225 \kelvin. Both methods yield unique distributions that agree very closely with the actual exact one accurately calculated from the corrected bulk-dispersion Kohlrausch model established independently by means of parametric data fit using the corrected modulus formalism method. The obtained distributions are also greatly superior to those estimated using approximate functions equations given in the literature.Comment: 4 pages and 4 figure

Interactions of technology and society: Impacts of improved airtransport. A study of airports at the grass roots

The feasibility of applying a particular conception of technology and social change to specific examples of technological development was investigated. The social and economic effects of improved airport capabilities on rural communities were examined. Factors which led to the successful implementation of a plan to construct sixty small airports in Ohio are explored and implications derived for forming public policies, evaluating air transportation development, and assessing technology

Minimizing the stochasticity of halos in large-scale structure surveys

In recent work (Seljak, Hamaus and Desjacques 2009) it was found that weighting central halo galaxies by halo mass can significantly suppress their stochasticity relative to the dark matter, well below the Poisson model expectation. In this paper we extend this study with the goal of finding the optimal mass-dependent halo weighting and use $N$-body simulations to perform a general analysis of halo stochasticity and its dependence on halo mass. We investigate the stochasticity matrix, defined as $C_{ij}\equiv<(\delta_i -b_i\delta_m)(\delta_j-b_j\delta_m)>$, where $\delta_m$ is the dark matter overdensity in Fourier space, $\delta_i$ the halo overdensity of the $i$-th halo mass bin and $b_i$ the halo bias. In contrast to the Poisson model predictions we detect nonvanishing correlations between different mass bins. We also find the diagonal terms to be sub-Poissonian for the highest-mass halos. The diagonalization of this matrix results in one large and one low eigenvalue, with the remaining eigenvalues close to the Poisson prediction $1/\bar{n}$, where $\bar{n}$ is the mean halo number density. The eigenmode with the lowest eigenvalue contains most of the information and the corresponding eigenvector provides an optimal weighting function to minimize the stochasticity between halos and dark matter. We find this optimal weighting function to match linear mass weighting at high masses, while at the low-mass end the weights approach a constant whose value depends on the low-mass cut in the halo mass function. Finally, we employ the halo model to derive the stochasticity matrix and the scale-dependent bias from an analytical perspective. It is remarkably successful in reproducing our numerical results and predicts that the stochasticity between halos and the dark matter can be reduced further when going to halo masses lower than we can resolve in current simulations.Comment: 17 pages, 14 figures, matched the published version in Phys. Rev. D including one new figur

Multi-Temperature Blackbody Spectra of Thin Accretion Disks With and Without a Zero-Torque Inner Boundary Condition

The standard spectral model for analyzing the soft component of thermal emission from a thin accretion disk around a black hole is the multi-temperature blackbody (MTB) model. The widely used implementation of this model, which is known as ``diskbb,'' assumes nonzero torque at the inner edge of the accretion disk. This assumption is contrary to the classic and current literature on thin-disk accretion, which advocates the use of a zero-torque boundary condition. Consequently, we have written code for a zero-torque model, ``ezdiskbb,'' which we compare to the nonzero-torque model diskbb by fitting RXTE spectra of three well-known black hole binaries: 4U 1543-47, XTE J1550-564, and GRO J1655-40. The chief difference we find is that the zero-torque model gives a value for the inner disk radius that is about 2.2 times smaller than the value given by diskbb. This result has important implications, especially for the determination of black-hole angular momentum and mass accretion rate.Comment: 27 pages, 9 figures, submitted to Ap

Improvements in simultaneous sodium and calcium imaging

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Cellular Neuroscience 12 (2019): 514. doi: 10.3389/fncel.2018.00514.High speed imaging of ion concentration changes in neurons is an important and growing tool for neuroscientists. We previously developed a system for simultaneously measuring sodium and calcium changes in small compartments in neurons (Miyazaki and Ross, 2015). We used this technique to analyze the dynamics of these ions in individual pyramidal neuron dendritic spines (Miyazaki and Ross, 2017). This system is based on high speed multiplexing of light emitting diodes (LEDs) and classic organic indicators. To improve this system we made additional changes, primarily incorporating lasers in addition to the LEDs, more sophisticated imaging protocols, and the use of newer sodium and calcium indicators. This new system generates signals with higher signal to noise ratio (S/N), less background fluorescence, and less photodynamic damage. In addition, by using longer wavelength indicators instead of indicators sensitive in the UV range, it allows for the incorporation of focal uncaging along with simultaneous imaging, which should extend the range of experiments.This work was supported in part by National Institutes of Health Grants R21NS085729 (WR), R01NS099122 (WR), and R01NS103168 (JL)

A flexible low-cost, high-precision, single interface electrical impedance tomography system for breast cancer detection using FPGA

Typically, in multi-frequency Electrical Impedance Tomography (EIT) systems, a current is applied and the voltages developed across the subject are detected. However, due to the complexity of designing stable current sources, there has been mention in the literature of applying a voltage to the subject whilst measuring the consequent current flow. This paper presents a comparative study between the two techniques in a novel design suitable for the detection of breast cancers. The suggested instrument borrows the best features of both the injection of current and the application of voltage, circumventing their limitations. Furthermore, the system has a common patient-electrode interface for both methodologies, whilst the control of the system and the necessary signal processing is carried out in a field programmable gate array (FPGA). Through this novel system, wide-bandwidth, low-noise, as well as high-speed (frame rate) can be achieved

Tomando en Cuenta lo Importante: Investigación Vecinal para la Salud y Justicia Económica y Ambiental en Richmond, North Richmond, y San Pablo

108 p. Libro electrónicoEl Proyecto de Indicadores del Oeste del Condado fue lanzado en 2006 para descubrir las respuestas de la comunidad a esta pregunta y trabajar con residentes y organizaciones locales para fortalecer el poder para alcanzar esta visión. Su punto principal: una comunidad saludable requiere justicia ambiental y económica. Con justicia ambiental, los residentes de Richmond, North Richmond, y San Pablo viven en una comunidad saludable y segura sin importar su raza, nacionalidad o situación económica. Justicia económica asegura que cada habitante tiene acceso a un medio de subsistencia significativo y que cada vecindario cuenta con los recursos necesarios para que ellos mismos puedan desarrollarse. Subyacente a todo el proyecto está la idea de que la investigación controlada y dirigida por los habitantes del vecindario puede ayudar a construir movimientos poderosos para un cambio social. El poder unificador de la investigación participativa sobre preocupaciones del vecindario construye conexiones y tiene éxito en temas como buenos trabajos, calidad del aire, oportunidades para jóvenes, condiciones del parque, alumbrado público, y calidad de las viviendas, y tiene poder para ayudar a unificar diversas comunidades