Color Screening, Casimir Scaling, and Domain Structure in G(2) and SU(N) Gauge Theories

We argue that screening of higher-representation color charges by gluons implies a domain structure in the vacuum state of non-abelian gauge theories, with the color magnetic flux in each domain quantized in units corresponding to the gauge group center. Casimir scaling of string tensions at intermediate distances results from random spatial variations in the color magnetic flux within each domain. The exceptional G(2) gauge group is an example rather than an exception to this picture, although for G(2) there is only one type of vacuum domain, corresponding to the single element of the gauge group center. We present some numerical results for G(2) intermediate string tensions and Polyakov lines, as well as results for certain gauge-dependent projected quantities. In this context, we discuss critically the idea of projecting link variables to a subgroup of the gauge group. It is argued that such projections are useful only when the representation-dependence of the string tension, at some distance scale, is given by the representation of the subgroup.Comment: 24 pages, 14 figures; v2: references added; v3: published version containing some additional introductory discussio

Uniqueness of infrared asymptotics in Landau gauge Yang-Mills theory

We uniquely determine the infrared asymptotics of Green functions in Landau gauge Yang-Mills theory. They have to satisfy both, Dyson-Schwinger equations and functional renormalisation group equations. Then, consistency fixes the relation between the infrared power laws of these Green functions. We discuss consequences for the interpretation of recent results from lattice QCD.Comment: 24 pages, 8 figure

Multiple Metamorphic Stages within an Eclogite-facies Terrane (Sesia Zone, Western Alps) Revealed by Th-U-Pb Petrochronology

Convergent plate margins typically experience a transition from subduction to collision dynamics as massive continental blocks enter the subduction channel. Studies of high-pressure rocks indicate that tectonic fragments are rapidly exhumed from eclogite facies to mid-crustal levels, but the details of such dynamics are controversial. To understand the dynamics of a subduction channel we report the results of a petrochronological study from the central Sesia Zone, a key element of the internal Western Alps. This comprises two polymetamorphic basement complexes (Eclogitic Micaschist Complex and Gneiss Minuti Complex) and a thin, dismembered cover sequence (Scalaro Unit) associated with pre-Alpine metagabbros and metasediments (Bonze Unit). Structurally controlled samples from three of these units (Eclogitic Micaschist Complex and Scalaro-Bonze Units) yield unequivocal petrological and geochronological evidence of two distinct high-pressure stages. Ages (U-Th-Pb) of growth zones in accessory allanite and zircon, combined with inclusion and textural relationships, can be tied to the multi-stage evolution of single samples. Two independent tectono-metamorphic ‘slices' showing a coherent metamorphic evolution during a given time interval have been recognized: the Fondo slice (which includes Scalaro and Bonze rocks) and the Druer slice (belonging to the Eclogitic Micaschist Complex). The new data indicate separate stages of deformation at eclogite-facies conditions for each recognized independent kilometer-sized tectono-metamorphic slice, between ∼85 and 60 Ma, with evidence of intermittent decompression (ΔP ∼ 0·5 GPa) within only the Fondo slice. The evolution path of the Druer slice indicates a different P-T-time evolution with prolonged eclogite-facies metamorphism between ∼85 and 75 Ma. Our approach, combining structural, petrological and geochronological techniques, yields field-based constraints on the duration and rates of dynamics within a subduction channe

APTASENSORS FOR BIOSECURITY APPLICATIONS

Nucleic acid aptamers have found steadily increased utility and application steadily over the last decade. In particular, aptamers have been touted as a valuable complement to and in some cases replacement for antibodies due to their structural and functional robustness as well as their ease in generation and synthesis. They are thus attractive for biosecurity applications, e.g. pathogen detection, and are especially well suited since their in vitro generation process does not require infection of any host systems. Herein we provide a brief overview of the aptamers generated against biopathogens over the last few years. In addition, a few recently described detection platforms using aptamers (aptasensors) and potentially suitable for biosecurity applications will be discussed

Unconventional MBE Strategies from Computer Simulations for Optimized Growth Conditions

We investigate the influence of step edge diffusion (SED) and desorption on Molecular Beam Epitaxy (MBE) using kinetic Monte-Carlo simulations of the solid-on-solid (SOS) model. Based on these investigations we propose two strategies to optimize MBE growth. The strategies are applicable in different growth regimes: During layer-by-layer growth one can exploit the presence of desorption in order to achieve smooth surfaces. By additional short high flux pulses of particles one can increase the growth rate and assist layer-by-layer growth. If, however, mounds are formed (non-layer-by-layer growth) the SED can be used to control size and shape of the three-dimensional structures. By controlled reduction of the flux with time we achieve a fast coarsening together with smooth step edges.Comment: 19 pages, 7 figures, submitted to Phys. Rev.

Historical Improvement in Speed Skating Economy

Half the improvement in 1500-m speed-skating world records can be explained by technological innovations and the other half by athletic improvement. It is hypothesized that improved skating economy is accountable for much of the athletic improvement. Purpose - To determine skating economy in contemporary athletes and to evaluate the change in economy over the years. Methods - Contemporary skaters of the Dutch national junior team (n=8) skated 3 bouts of 6 laps at submaximal velocity, from which skating economy was calculated (in mL O2·kg-1·km-1). A literature search provided historic data of skating velocity and submaximal VO2 (in mL·kg-1·min-1), from which skating economy was determined. The association between year and skating economy was determined using linear regression analysis. Correcting the change in economy for technological innovations resulted in an estimate of the association between year and economy due to athletic improvement. Results An average (±SD) skating economy of 73.4±6.4 mL O2·kg-1·km-1 was found in contemporary athletes. Skating economy improved significantly over the historical timeframe (-0.57 mL O2·kg-1·km-1 per year, 95% confidence interval [-0.84, -0.31]). In the final regression model for the klapskate era, with altitude as confounder, skating economy improved with a non-significant -0.58 mL O2·kg-1·km-1 each year ([-1.19, 0.035]). Conclusions Skating economy was 73.4±6.4 mL O2·kg-1·km-1 in contemporary athletes and improved over the past ~50 years. The association between year and skating economy due to athletic improvement, for the klapskate era, approached significance, suggesting a possible improvement in economy over these years

An assessment of the statistical distribution of Random Telegraph Noise Time Constants

As transistor sizes are downscaled, a single trapped charge has a larger impact on smaller devices and the Random Telegraph Noise (RTN) becomes increasingly important. To optimize circuit design, one needs assessing the impact of RTN on the circuit and this can only be accomplished if there is an accurate statistical model of RTN. The dynamic Monte Carlo modelling requires the statistical distribution functions of both the amplitude and the capture/emission time (CET) of traps. Early works were focused on the amplitude distribution and the experimental data of CETs were typically too limited to establish their statistical distribution reliably. In particular, the time window used has been often small, e.g. 10 sec or less, so that there are few data on slow traps. It is not known whether the CET distribution extracted from such a limited time window can be used to predict the RTN beyond the test time window. The objectives of this work are three fold: to provide the long term RTN data and use them to test the CET distributions proposed by early works; to propose a methodology for characterizing the CET distribution for a fabrication process efficiently; and, for the first time, to verify the long term prediction capability of a CET distribution beyond the time window used for its extraction