The use of ion beam cleaning to obtain high quality cold welds with minimal deformation

A variation of cold welding is described which utilizes an ion beam to clean mating surfaces prior to joining in a vacuum environment. High quality solid state welds were produced with minimal deformation

Infall near clusters of galaxies: comparing gas and dark matter velocity profiles

We consider the dynamics in and near galaxy clusters. Gas, dark matter and galaxies are presently falling into the clusters between approximately 1 and 5 virial radii. At very large distances, beyond 10 virial radii, all matter is following the Hubble flow, and inside the virial radius the matter particles have on average zero radial velocity. The cosmological parameters are imprinted on the infall profile of the gas, however, no method exists, which allows a measurement of it. We consider the results of two cosmological simulations (using the numerical codes RAMSES and Gadget) and find that the gas and dark matter radial velocities are very similar. We derive the relevant dynamical equations, in particular the generalized hydrostatic equilibrium equation, including both the expansion of the Universe and the cosmological background. This generalized gas equation is the main new contribution of this paper. We combine these generalized equations with the results of the numerical simulations to estimate the contribution to the measured cluster masses from the radial velocity: inside the virial radius it is negligible, and inside two virial radii the effect is below 40%, in agreement the earlier analyses for DM. We point out how the infall velocity in principle may be observable, by measuring the gas properties to distance of about two virial radii, however, this is practically not possible today.Comment: 7 pages, 3 figures, to appear in MNRA

An Invariant Theory of Spacelike Surfaces in the Four-dimensional Minkowski Space

We consider spacelike surfaces in the four-dimensional Minkowski space and introduce geometrically an invariant linear map of Weingarten-type in the tangent plane at any point of the surface under consideration. This allows us to introduce principal lines and an invariant moving frame field. Writing derivative formulas of Frenet-type for this frame field, we obtain eight invariant functions. We prove a fundamental theorem of Bonnet-type, stating that these eight invariants under some natural conditions determine the surface up to a motion. We show that the basic geometric classes of spacelike surfaces in the four-dimensional Minkowski space, determined by conditions on their invariants, can be interpreted in terms of the properties of the two geometric figures: the tangent indicatrix, and the normal curvature ellipse. We apply our theory to a class of spacelike general rotational surfaces.Comment: 23 pages; to appear in Mediterr. J. Math., Vol. 9 (2012

Scaling treatment of the random field Ising model

Analytic phenomenological scaling is carried out for the random field Ising model in general dimensions using a bar geometry. Domain wall configurations and their decorated profiles and associated wandering and other exponents $(\zeta,\gamma,\delta,\mu)$ are obtained by free energy minimization. Scaling between different bar widths provides the renormalization group (RG) transformation. Its consequences are (1) criticality at $h=T=0$ in $d \leq 2$ with correlation length $\xi(h,T)$ diverging like $\xi(h,0) \propto h^{-2/(2-d)}$ for $d<2$ and $\xi(h,0) \propto \exp[1/(c_1\gamma h^{\gamma})]$ for $d=2$, where $c_1$ is a decoration constant; (2) criticality in $d = 2+\epsilon$ dimensions at $T=0$, $h^{\ast}= (\epsilon/2c_1)^{1/\gamma}$, where $\xi \propto [(s-s^{\ast})/s]^{-2\epsilon/\gamma}$, $s \equiv h^{\gamma}$. Finite temperature generalizations are outlined. Numerical transfer matrix calculations and results from a ground state algorithm adapted for strips in $d=2$ confirm the ingredients which provide the RG description.Comment: RevTex v3.0, 5 pages, plus 4 figures uuencode

Changes in U.S. family finances from 2004 to 2007: evidence from the Survey of Consumer Finances

The Federal Reserve Board's Survey of Consumer Finances for 2007 provides insights into changes in family income and net worth since the 2004 survey. The survey shows that, over the 2004-07 period, the median value of real (inflation-adjusted) family income before taxes was little changed, while mean income climbed 8.5 percent. Unlike family income over this period, both median and mean net worth increased; the median rose 17.7 percent, and the mean rose 13.0 percent. This article reviews these and other changes in the financial condition of U.S. families, including developments in assets, liabilities, and debt payments.Consumer surveys ; Households - Economic aspects

Explicit connection between conformal field theory and 2+1 Chern-Simons theory

We give explicit field theoretical representations for the observables of 2+1 dimensional Chern-Simons theory in terms of gauge invariant composites of 2D WZW fields. To test our identification we compute some basic Wilson loop correlators reobtaining known results.Comment: 13 pages, Latex file. To appear in Mod.Phys.Lett.

Changes from 1986 to 2006 in reasons for liking leisure-time physical activity among adolescents

Reasons for participating in physical activity (PA) may have changed in accordance with the general modernization of society. The aim is to examine changes in self-reported reasons for liking leisure-time physical activity (LTPA) and their association with self-reported LTPA over a 20-year period. Data were collected among nationally representative samples of 13-year-olds in Finland, Norway, and Wales in 1986 and 2006 (N = 9252) as part of the WHO cross-national Health Behaviour in School-aged Children (HBSC) study. Univariate ANOVAs to establish differences according to gender, year, and country were conducted. In all countries, 13-year-olds in 2006 tended to report higher importance in terms of achievement and social reasons than their counterparts in 1986, while changes in health reasons were minor. These reasons were associated with LTPA in a similar way at both time points. Health reasons for liking LTPA were considered most important, and were the strongest predictor of LTPA. The findings seem robust as they were consistent across countries and genders. Health education constitutes the most viable strategy for promoting adolescents' motivation for PA, and interventions and educational efforts could be improved by an increased focus on LTPA and sport as a social activity

Structure of d(TGCGCA)(2) and a comparison with other DNA Hexamers

The X-ray crystal structure of d(TGCGCA)(2) has been determined at 120 K to a resolution of 1.3 Angstrom. Hexamer duplexes, in the Z-DNA conformation, pack in an arrangement similar to the 'pure spermine form' [Egli et al. (1991). Biochemistry, 30, 11388-11402] but with significantly different cell dimensions. The phosphate backbone exists in two equally populated discrete conformations at one nucleotide step, around phosphate 11. The structure contains two ordered cobalt hexammine molecules which have roles in stabilization of both the Z-DNA conformation of the duplex and in crystal packing. A comparison of d(TGCGCA)(2) with other Z-DNA hexamer structures available in the Nucleic Acid Database illustrates the elusive nature of crystal packing. A review of the interactions with the metal cations Na+, Mg2+ and Co3+ reveals a relatively small proportion of phosphate binding and that close contacts between metal ions are common. A prediction of the water structure is compared with the observed pattern in the reported structure

Soil Moisture Workshop

The Soil Moisture Workshop was held at the United States Department of Agriculture National Agricultural Library in Beltsville, Maryland on January 17-19, 1978. The objectives of the Workshop were to evaluate the state of the art of remote sensing of soil moisture; examine the needs of potential users; and make recommendations concerning the future of soil moisture research and development. To accomplish these objectives, small working groups were organized in advance of the Workshop to prepare position papers. These papers served as the basis for this report