Impedance matrix of a folded dipole pair under eleven configuration

A new decade wideband antenna, the Eleven antenna, has been developed during the last years. The basic configuration of Eleven antenna is two parallel dipoles separated by half wavelength above the ground plane, which is referred to as the eleven configuration. In order to cascade the dipoles in log-periodic array for obtaining wideband performance, folded dipoles are often used. The input impedance of shorted folded dipole in free space has been analysed by using two-mode method: a transmission line mode and an antenna mode. In the present study, the impedance matrix of a pair of folded dipoles as a two-port network under the eleven configuration will be analysed by including the mutual coupling among elements of folded dipoles into the two-mode method. As veri. cation, an Eleven antenna with one pair of folded dipoles has been analysed by the present method, modelled in a commercial software - CST MS and manufactured. The results by using the present method agree well with the measured and simulated one

Relations between topography, wetlands, vegetation cover and stream water chemistry in boreal headwater catchments in Sweden

International audienceA large part of the spatial variation of stream water chemistry is found in headwater streams and small catchments. To understand the dominant processes, taking place in small and heterogeneous catchments, spatial and temporal data with high resolution is needed. In most cases available map data has too low quality and resolution to successfully be used in environmental assessments and modelling. In this study 18 forested catchments (1?4 km2) were selected within a 120×50 km area in the county of Värmland in western Sweden. The aim was to test if topographic and vegetation variables derived from official datasets were correlated to stream water chemistry, represented by DOC, Al, Fe and Si content. A GIS was used to analyse the elevation characteristics, generate topographic indices and calculate the percentage of wetlands and a number of vegetation classes. The results clearly show that the topography has a major influence on the occurrence of wetlands, which has a major influence on stream water chemistry. There were very strong correlations between mean slope and percentage wetland, percentage wetland and DOC, mean slope and DOC and mean topographic wetness index and DOC. The conclusion was that official topographic data, despite uncertain or low quality and resolution, could be useful in the prediction of headwater chemistry in boreal forested catchments

Extension of nano-confined DNA: quantitative comparison between experiment and theory

The extension of DNA confined to nanochannels has been studied intensively and in detail. Yet quantitative comparisons between experiments and model calculations are difficult because most theoretical predictions involve undetermined prefactors, and because the model parameters (contour length, Kuhn length, effective width) are difficult to compute reliably, leading to substantial uncertainties. Here we use a recent asymptotically exact theory for the DNA extension in the "extended de Gennes regime" that allows us to compare experimental results with theory. For this purpose we performed new experiments, measuring the mean DNA extension and its standard deviation while varying the channel geometry, dye intercalation ratio, and ionic buffer strength. The experimental results agree very well with theory at high ionic strengths, indicating that the model parameters are reliable. At low ionic strengths the agreement is less good. We discuss possible reasons. Our approach allows, in principle, to measure the Kuhn length and effective width of a single DNA molecule and more generally of semiflexible polymers in solution.Comment: Revised version, 6 pages, 2 figures, 1 table, supplementary materia

Identifying Collective Modes via Impurities in the Cuprate Superconductors

We show that the pinning of collective charge and spin modes by impurities in the cuprate superconductors leads to qualitatively different fingerprints in the local density of states (LDOS). In particular, in a pinned (static) spin droplet, the creation of a resonant impurity state is suppressed, the spin-resolved LDOS exhibits a characteristic spatial pattern, and the LDOS undergoes significant changes with increasing magnetic field. Since all of these fingerprints are absent in a charge droplet, impurities are a new probe for identifying the nature and relative strength of collective modes.Comment: 4 pages, 4 figure

Materializing Power to Recover Corporate Social Responsibility

Through the development of CSR ratings, metrics and management tools, Corporate Social Responsibility (CSR) is currently materialized at an unprecedented scale within and across organizations. However, the material dimension of CSR and the inherent political potential in this materialization have been neglected. Drawing on insights from Actor-Network Theory (ANT) and the critical discussion of current approaches to power in CSR studies, we offer an alternative sociomaterial conceptualization of power in order to clarify how power works through materialized forms of CSR. We develop a framework that explains both how power is constituted within materialized forms of CSR through processes of ‘assembling / disassembling’, and how power is mobilized through materialized forms of CSR through processes of ‘overflowing / framing’. From this framework, we derive four tactics that clarify how CSR materializations can be seized by marginalized actors to ‘recover’ CSR. Our analysis aims to renew CSR studies by showing the potential of CSR for progressive politics

A Survey of Safety Recommendations for All-Terrain Vehicle Dealers and Track Owners in Kansas

Introduction. All-terrain vehicles (ATVs) are associated with injury,mortality, and healthcare costs. ATV related injuries are less severewhen consistent safety practices are followed, however, ATV safetyregulations are varied among states. This study sought to surveyKansas ATV dealers and track owners to determine safety promotionpractices. Methods. A cross-sectional telephone survey was conducted ofKansas ATV dealers and tracks. Survey questions included promotionand sale of safety equipment, provision of ATV safety information,and respondent characteristics. Results. Of those contacted, 32% of dealers and 31% of tracksresponded to the survey. Most ATV dealers sell safety gear (70% -100%) and all recommend safety gear to buyers and riders. All ATVtracks reported requiring helmets (100%) but were varied regardingother forms of safety gear. The majority of ATV dealers (77%) recommendedsafety courses, but only 31% of dealers and 40% of tracksoffered courses. Eighty percent of ATV tracks and 52% of dealers feltthey had a professional responsibility to educate riders/owners onsafety. Conclusions. Safety promotion by ATV dealers in Kansas consistentlywas recommended, but often limited to the sales of safety gear(helmets and gloves) or the provision of manufacturer provided safetymaterials. Further, ATV dealers reported rarely offering skills tests orsafety courses to buyers. In Kansas, safety promotion at the point ofsale or track level could be improved to increase public awareness ofATV safety practices. KS J Med 2017;10(4):76-78

Complete Experimental Structure Determination of the p(3x2)pg Phase of Glycine on Cu{110}

We present a quantitative low energy electron diffraction (LEED) surface-crystallograpic study of the complete adsorption geometry of glycine adsorbed on Cu{110} in the ordered p(3×2) phase. The glycine molecules form bonds to the surface through the N atoms of the amino group and the two O atoms of the de-protonated carboxylate group, each with separate Cu atoms such that every Cu atom in the first layer is involved in a bond. Laterally, N atoms are nearest to the atop site (displacement 0.41 Å). The O atoms are asymmetrically displaced from the atop site by 0.54 Å and 1.18 Å with two very different O-Cu bond lengths of 1.93 Å and 2.18 Å. The atom positions of the upper-most Cu layers show small relaxations within 0.07 Å of the bulk-truncated surface geometry. The unit cell of the adsorbate layer consists of two glycine molecules, which are related by a glide-line symmetry operation. This study clearly shows that a significant coverage of adsorbate structures without this glide-line symmetry must be rejected, both on the grounds of the energy dependence of the spot intensities (LEED-IV curves) and of systematic absences in the LEED pattern

Digital pulse-shape discrimination of fast neutrons and gamma rays

Discrimination of the detection of fast neutrons and gamma rays in a liquid scintillator detector has been investigated using digital pulse-processing techniques. An experimental setup with a 252Cf source, a BC-501 liquid scintillator detector, and a BaF2 detector was used to collect waveforms with a 100 Ms/s, 14 bit sampling ADC. Three identical ADC's were combined to increase the sampling frequency to 300 Ms/s. Four different digital pulse-shape analysis algorithms were developed and compared to each other and to data obtained with an analogue neutron-gamma discrimination unit. Two of the digital algorithms were based on the charge comparison method, while the analogue unit and the other two digital algorithms were based on the zero-crossover method. Two different figure-of-merit parameters, which quantify the neutron-gamma discrimination properties, were evaluated for all four digital algorithms and for the analogue data set. All of the digital algorithms gave similar or better figure-of-merit values than what was obtained with the analogue setup. A detailed study of the discrimination properties as a function of sampling frequency and bit resolution of the ADC was performed. It was shown that a sampling ADC with a bit resolution of 12 bits and a sampling frequency of 100 Ms/s is adequate for achieving an optimal neutron-gamma discrimination for pulses having a dynamic range for deposited neutron energies of 0.3-12 MeV. An investigation of the influence of the sampling frequency on the time resolution was made. A FWHM of 1.7 ns was obtained at 100 Ms/s.Comment: 26 pages, 14 figures, submitted to Nuclear Instruments and Methods in Physics Research