Radiative polarization of electrons in a strong laser wave

We reanalyze the problem of radiative polarization of electrons brought into collision with a circularly polarized strong plane wave. We present an independent analytical verification of formulae for the cross section given by D.\,Yu. Ivanov et al [Eur.\ Phys.\ J. C \textbf{36}, 127 (2004)]. By choosing the exact electron's helicity as the spin quantum number we show that the self-polarization effect exists only for the moderately relativistic electrons with energy $\gamma = E/mc^2 \lesssim 10$ and only for a non-head-on collision geometry. In these conditions polarization degree may achieve the values up to 65%, but the effective polarization time is found to be larger than 1\,s even for a high power optical or infrared laser with intensity parameter $\xi = |{\bf E}| m c^2/E_c \hbar \omega \sim 0.1$ ($E_c = m^2 c^3/e \hbar$). This makes such a polarization practically unrealizable. We also compare these results with the ones of some papers where the high degree of polarization was predicted for ultrarelativistic case. We argue that this apparent contradiction arises due to the different choice of the spin quantum numbers. In particular, the quantum numbers which provide the high polarization degree represent neither helicity nor transverse polarization, that makes the use of them inconvenient in practice.Comment: minor changes compared to v3; to appear in PR

Entangled granular media

We study the geometrically induced cohesion of ensembles of granular "u-particles" which mechanically entangle through particle interpenetration. We vary the length-to-width ratio $l/w$ of the u-particles and form them into free-standing vertical columns. In laboratory experiment we monitor the response of the columns to sinusoidal vibration (frequency $f$, peak acceleration $\Gamma$). Column collapse occurs in a characteristic time, $\tau$, which follows the relation $\tau = f^{-1} \exp(\Delta / \Gamma)$. $\Delta$ resembles an activation energy and is maximal at intermediate $l/w$. Simulation reveals that optimal strength results from competition between packing and entanglement.Comment: 4 pages, 5 figure

Bottom-loading dilution refrigerator with ultra-high vacuum deposition capability

A Kelvinox 400 dilution refrigerator with the ability to load samples onto the mixing chamber from the bottom of the cryostat has been combined with an ultrahigh-vacuum (UHV) deposition chamber equipped with molecular beam sources. The liquid helium cooled sample transfer mechanism is used in a manner that allows films to be grown on substrates which are kept at temperatures of order 8K with chamber pressures in the 10^-9 to 10^-10 Torr range. This system facilitates the growth of quench-condensed ultrathin films which must always be kept below ~ 12K in a UHV environment during and after growth. Measurements can be made on the films down to millikelvin temperatures and in magnetic fields up to 15 T.Comment: 10 pages text, 1figur

Forcing function control of Faraday wave instabilities in viscous shallow fluids

We investigate the relationship between the linear surface wave instabilities of a shallow viscous fluid layer and the shape of the periodic, parametric-forcing function (describing the vertical acceleration of the fluid container) that excites them. We find numerically that the envelope of the resonance tongues can only develop multiple minima when the forcing function has more than two local extrema per cycle. With this insight, we construct a multi-frequency forcing function that generates at onset a non-trivial harmonic instability which is distinct from a subharmonic response to any of its frequency components. We measure the corresponding surface patterns experimentally and verify that small changes in the forcing waveform cause a transition, through a bicritical point, from the predicted harmonic short-wavelength pattern to a much larger standard subharmonic pattern. Using a formulation valid in the lubrication regime (thin viscous fluid layer) and a WKB method to find its analytic solutions, we explore the origin of the observed relation between the forcing function shape and the resonance tongue structure. In particular, we show that for square and triangular forcing functions the envelope of these tongues has only one minimum, as in the usual sinusoidal case.Comment: 12 pages, 10 figure

What does the future hold for utility electricity efficiency programs?

This study develops projections of future spending and savings from electricity efficiency programs funded by electric utility customers in the United States through 2030 based on three scenarios. Our analysis relies on detailed bottom-up modeling of current state energy efficiency policies, demand-side management and integrated resource plans, and regulatory decisions. The three scenarios represent a range of potential outcomes given the policy environment at the time of the study and uncertainties in the broader economic and state policy environment in each state. We project spending to increase to $8.6 billion in 2030 in the medium scenario, about a 45 percent increase relative to 2016 spending. In the high case, annual spending increases to$11.1 billion in 2030 and remains relatively flat in the low case ($6.8 billion in 2030). Our analysis suggests that electricity efficiency programs funded by utility customers will continue to impact load growth significantly at least through 2030, as savings as a percent of retail sales are forecast at 0.7 percent in the medium scenario and 0.98 percent in the high scenario

Stationary state volume fluctuations in a granular medium

A statistical description of static granular material requires ergodic sampling of the phase space spanned by the different configurations of the particles. We periodically fluidize a column of glass beads and find that the sequence of volume fractions phi of post-fluidized states is history independent and Gaussian distributed about a stationary state. The standard deviation of phi exhibits, as a function of phi, a minimum corresponding to a maximum in the number of statistically independent regions. Measurements of the fluctuations enable us to determine the compactivity X, a temperature-like state variable introduced in the statistical theory of Edwards and Oakeshott [Physica A {\bf 157}, 1080 (1989)].Comment: published with minor change

Energetics of Quantum Antidot States in Quantum Hall Regime

We report experiments on the energy structure of antidot-bound states. By measuring resonant tunneling line widths as function of temperature, we determine the coupling to the remote global gate voltage and find that the effects of interelectron interaction dominate. Within a simple model, we also determine the energy spacing of the antidot bound states, self consistent edge electric field, and edge excitation drift velocity.Comment: 4 pages, RevTex, 5 Postscript figure

Goodbye to Projects? Briefing Paper 1: An Overview: Projects and Principles.

YesThis briefing paper reports on research exploring ten detailed case studies of livelihoods-oriented interventions operating in Tanzania, Lesotho, South Africa and Uganda. Analysing these interventions through an audit of sustainable livelihood `principles¿ (as a proxy for best practice) revealed general lessons both about the practical opportunities and challenges for employing sustainable livelihoods approaches to the design, implementation, monitoring and evaluation of development interventions and also about the changing format of development interventions.Department for International Developmen

Goodbye to Projects? - Briefing Paper 3: The changing format of development interventions.

yesThis briefing paper reports on research exploring ten detailed case studies of livelihoods-oriented interventions operating in Tanzania, South Africa, Uganda and Lesotho. As a proxy for best practice, these interventions were analysed through an audit of sustainable livelihood `principles¿. This revealed general lessons about both the practical opportunities and challenges for employing sustainable livelihoods approaches to the design, implementation, monitoring and evaluation of development interventions and also about the changing format of development interventions.Department for International Development