Metal drilling with portable hand drills

Study of metal drilling solves problems of excessive burring, oversized holes, and out-of-round holes. Recommendations deal with using the proper chemical coolants, applying the coolants effectively, employing cutting oils, and dissipating the heat caused by drilling

Surface enhancement of oxygen exchange and diffusion in the ionic conductor La2Mo2O9

Isotopic surface oxygen exchange and its subsequent diffusion have been measured using secondary ion mass spectrometry in the fast ionic conductor La2Mo2O9. A silver coating was applied to the sample surface to enhance the surface exchange process for dry oxygen. Contrary to previous studies performed using a wet atmosphere, no grain boundary diffusion tail was observed under these optimized dry exchange conditions. The activation energy for oxygen diffusion was found to be 0.66(+/- 0.09) eV at high temperature (>570 degrees C), and 1.25(+/- 0.01)eV at low temperature (<570 degrees C). Time-of-Flight secondary ion mass spectrometry was employed to investigate the correlation between the silver coating and the O-18 concentration on the sample surface. A close correlation between the presence of silver and oxygen incorporation on the surface was observed. (C) 2010 Elsevier B.V. All rights reserved

The Validity of Individual Psychological Assessments for Entry-Level Police and Firefighter Positions

Although individual psychological assessment is widely used in employee selection, the empirical research on the validity of individual assessments is sparse. A multi-stage, multi-site study examined the validity of individual assessments for police officer and firefighter positions. Results showed that assessor judgments were largely unrelated to standardized test results, and that both assessor judgments and standardized tests were only weakly related to job performance ratings. Differences in validity across assessors were also found, with some assessors providing better predictions than others

Spacetime geometry of static fluid spheres

We exhibit a simple and explicit formula for the metric of an arbitrary static spherically symmetric perfect fluid spacetime. This class of metrics depends on one freely specifiable monotone non-increasing generating function. We also investigate various regularity conditions, and the constraints they impose. Because we never make any assumptions as to the nature (or even the existence) of an equation of state, this technique is useful in situations where the equation of state is for whatever reason uncertain or unknown. To illustrate the power of the method we exhibit a new form of the ``Goldman--I'' exact solution and calculate its total mass. This is a three-parameter closed-form exact solution given in terms of algebraic combinations of quadratics. It interpolates between (and thereby unifies) at least six other reasonably well-known exact solutions.Comment: Plain LaTeX 2e -- V2: now 22 pages; minor presentation changes in the first part of the paper -- no physics modifications; major additions to the examples section: the Gold-I solution is shown to be identical to the G-G solution. The interior Schwarzschild, Stewart, Buch5 XIII, de Sitter, anti-de Sitter, and Einstein solutions are all special cases. V3: Reference, footnotes, and acknowledgments added, typos fixed -- no physics modifications. V4: Technical problems with mass formula fixed -- affects discussion of our examples but not the core of the paper. Version to appear in Classical and Quantum Gravit

Negative Energy Density States for the Dirac Field in Flat Spacetime

Negative energy densities in the Dirac field produced by state vectors that are the superposition of two single particle electron states are examined. I show that for such states the energy density of the field is not bounded from below and that the quantum inequalities derived for scalar fields are satisfied. I also show that it is not possible to produce negative energy densities in a scalar field using state vectors that are arbitrary superpositions of single particle states.Comment: 11 pages, LaTe

Violator Spaces: Structure and Algorithms

Sharir and Welzl introduced an abstract framework for optimization problems, called LP-type problems or also generalized linear programming problems, which proved useful in algorithm design. We define a new, and as we believe, simpler and more natural framework: violator spaces, which constitute a proper generalization of LP-type problems. We show that Clarkson's randomized algorithms for low-dimensional linear programming work in the context of violator spaces. For example, in this way we obtain the fastest known algorithm for the P-matrix generalized linear complementarity problem with a constant number of blocks. We also give two new characterizations of LP-type problems: they are equivalent to acyclic violator spaces, as well as to concrete LP-type problems (informally, the constraints in a concrete LP-type problem are subsets of a linearly ordered ground set, and the value of a set of constraints is the minimum of its intersection).Comment: 28 pages, 5 figures, extended abstract was presented at ESA 2006; author spelling fixe

A multifaceted hospital-wide intervention increases hand hygiene compliance

Background. Hand hygiene is an important and basic practice that should be used by all healthcare staff to protect both themselves and their patients against infection. Unfortunately hand hygiene compliance remains poor.Objective. To show an improvement in hand hygiene compliance using a multifaceted approach.Methods. This was a quasiexperimental pre-post intervention study design with a number of standardised interventions to promote hand hygiene. The World Health Organization hand hygiene multimodal (five-step) intervention approach was used. The study ran from June 2015 to August 2015 in 11 selected wards of a 975-bed tertiary and quaternary care public hospital (Groote Schuur Hospital, Cape Town, South Africa). The outcome was to assess improvement in hand hygiene compliance monthly over the 3 months, compared with nonintervention wards and compared with the wards’ own performance measured in 2014. The study included both descriptive and analytical components.Results. Post intervention, hand hygiene compliance showed a statistically significant improvement for before patient contact from 34% in 2014 to 76% in 2015 (p&lt;0.05) and for after patient contact from 47% in 2014 to 82% in 2015 (p&lt;0.05).Conclusion. The intervention improved hand hygiene compliance and can easily be replicated in other wards, resulting in sustaining a culture of hand hygiene improvement and behavioural change throughout the hospital

Volume Integral Theorem for Exotic Matter

We answer an important question in general relativity about the volume integral theorem for exotic matter by suggesting an exact integral quantifier for matter violating Averaged Null Energy Condition (ANEC). It is checked against some well known static, spherically symmetric traversable wormhole solutions of general relativity with a sign reversed kinetic term minimally coupled scalar field. The improved quantifier is consistent with the principle that traversable wormholes can be supported by arbitrarily small quantities of exotic matter.Comment: 7 page