Oblique-incidence secondary emission from charged dielectrics

Secondary electron emission coefficients were measured on FEP-Teflon for normal and oblique incidence in the presence of a normal electric field. Such measurements require knowledge of the electrostatic environment surrounding the specimen, and they require calculation of particle trajectories such that particle impact parameters can be known. A simulation using a conformal mapping, a Green's integral, and a trajectory generator provides the necessary mathematical support for the measurements, which were made with normal fields of 1.5 and 2.7 kV/mm. When incidence is normal and energy exceeds the critical energy, the coefficient is given by (V sub 0/V) to the .58 power, and for oblique incidence this expression may be divided by the cosine of the angle. The parameter V sub 0 is a function of normal field

THE GROCERY STORES' WAGE DISTRIBUTION: A SEMI-PARAMETRIC ANALYSIS OF THE ROLE OF RETAILING AND LABOR MARKET INSTITUTIONS

How and why has the wage distribution in U.S. grocery stores changed between 1984 and 1994? Unlike other industries in the time period, the important change in the wage distribution is not rising inequality, but the real wages fell across the entire wage distribution. Changes in labor market institutions explain more than half of the change in the wage distribution in grocery stores. Specifically, the decline in the real value of the minimum wage explains little of the decline in the mean real wage but much of the change in the shape of the distribution between 1984 and 1994, and 95 percent of the decline at the lowest 10th percentile. The decline in union coverage in grocery stores and the narrowing of the union-nonunion wage gap explains much of the decline above the 25th percentile. A third institutional change, the use of part-time employees, is not associated with the changes in grocery industry wage outcomes. One might think that the major changes in operation and technologies that occurred during this time period are at least contributing factors, but we find quite the contrary. If average store size, weekly operating hours, and the use of scanning technology had remained at their 1984 levels, the real wage decline would have been even greater than that actually seen, and for the entire wage distribution. Changes in grocery retailing prevented and even greater decline in real wages. Again unlike many other industries, skill-biased technological change does not appear important for grocery industry wage outcomes. The basis of our analysis is a statistical technique which combines nonparametric kernel density estimation with a parametric re-weighting, applied to Current Population Survey data supplemented with secondary data sources on the Grocery industry.Agribusiness, Labor and Human Capital,

The role of the priesthood in the preservation and propagation of law

Not available

Fiber R and D for the CMS HCAL

This paper documents the fiber R and D for the CMS hadron barrel calorimeter (HCAL). The R and D includes measurements of fiber flexibility, splicing, mirror reflectivity, relative light yield, attenuation length, radiation effects, absolute light yield, and transverse tile uniformity. Schematics of the hardware for each measurement are shown. These studies are done for different diameters and kinds of multiclad fiber.Comment: 23 pages, 30 Figures 89 pages, 41 figures, corresponding author: H. Budd, [email protected]

Secondary electron emission from electrically charged fluorinated-ethylene-propylene Teflon for normal and non-normal electron incidence

The secondary electron emission coefficient was measured for a charged polymer (FEP-Teflon) with normally and obliquely incident primary electrons. Theories of secondary emission are reviewed and the experimental data is compared to these theories. Results were obtained for angles of incidence up to 60 deg in normal electric fields of 1500 V/mm. Additional measurements in the range from 50 to 70 deg were made in regions where the normal and tangential fields were approximately equal. The initial input angles and measured output point of the electron beam could be analyzed with computer simulations in order to determine the field within the chamber. When the field is known, the trajectories can be calculated for impacting electrons having various energies and angles of incidence. There was close agreement between the experimental results and the commonly assumed theoretical model in the presence of normal electric fields for angles of incidence up to 60 deg. High angle results obtained in the presence of tangential electric fields did not agree with the theoretical models

Evaluating the Evolutionary Origins of Unexpected Character Distributions within the Bacterial Planctomycetes-Verrucomicrobia-Chlamydiae Superphylum

Recently, several characters that are absent from most bacteria, but which are found in many eukaryotes or archaea, have been identified within the bacterial Planctomycetes-Verrucomicrobia-Chlamydiae (PVC) superphylum. Hypotheses of the evolutionary history of such characters are commonly based on the inference of phylogenies of gene or protein families associated with the traits, estimated from multiple sequence alignments (MSAs). So far, studies of this kind have focused on the distribution of (i) two genes involved in the synthesis of sterol, (ii) tubulin genes, and (iii) c1 transfer genes. In many cases, these analyses have concluded that horizontal gene transfer (HGT) is likely to have played a role in shaping the taxonomic distribution of these gene families. In this article, we describe several issues with the inference of HGT from such analyses, in particular concerning the considerable uncertainty associated with our estimation of both gene family phylogenies (especially those containing ancient lineage divergences) and the Tree of Life (ToL), and the need for wider use and further development of explicit probabilistic models to compare hypotheses of vertical and horizontal genetic transmission. We suggest that data which is often taken as evidence for the occurrence of ancient HGT events may not be as convincing as is commonly described, and consideration of alternative theories is recommended. While focusing on analyses including PVCs, this discussion is also relevant for inferences of HGT involving other groups of organisms

Interplay of Mre11 Nuclease with Dna2 plus Sgs1 in Rad51-Dependent Recombinational Repair

The Mre11/Rad50/Xrs2 complex initiates IR repair by binding to the end of a double-strand break, resulting in 5′ to 3′ exonuclease degradation creating a single-stranded 3′ overhang competent for strand invasion into the unbroken chromosome. The nuclease(s) involved are not well understood. Mre11 encodes a nuclease, but it has 3′ to 5′, rather than 5′ to 3′ activity. Furthermore, mutations that inactivate only the nuclease activity of Mre11 but not its other repair functions, mre11-D56N and mre11-H125N, are resistant to IR. This suggests that another nuclease can catalyze 5′ to 3′ degradation. One candidate nuclease that has not been tested to date because it is encoded by an essential gene is the Dna2 helicase/nuclease. We recently reported the ability to suppress the lethality of a dna2Δ with a pif1Δ. The dna2Δ pif1Δ mutant is IR-resistant. We have determined that dna2Δ pif1Δ mre11-D56N and dna2Δ pif1Δ mre11-H125N strains are equally as sensitive to IR as mre11Δ strains, suggesting that in the absence of Dna2, Mre11 nuclease carries out repair. The dna2Δ pif1Δ mre11-D56N triple mutant is complemented by plasmids expressing Mre11, Dna2 or dna2K1080E, a mutant with defective helicase and functional nuclease, demonstrating that the nuclease of Dna2 compensates for the absence of Mre11 nuclease in IR repair, presumably in 5′ to 3′ degradation at DSB ends. We further show that sgs1Δ mre11-H125N, but not sgs1Δ, is very sensitive to IR, implicating the Sgs1 helicase in the Dna2-mediated pathway

Dynamics of a piecewise smooth map with singularity

Experiments observing the liquid surface in a vertically oscillating container have indicated that modeling the dynamics of such systems require maps that admit states at infinity. In this paper we investigate the bifurcations in such a map. We show that though such maps in general fall in the category of piecewise smooth maps, the mechanisms of bifurcations are quite different from those in other piecewise smooth maps. We obtain the conditions of occurrence of infinite states, and show that periodic orbits containing such states are superstable. We observe period-adding cascade in this system, and obtain the scaling law of the successive periodic windows.Comment: 10 pages, 6 figures, composed in Latex2

Pilot survey of the health of Massachusetts dentists

AimDentistry is a career that is very rewarding because of the direct opportunity to deliver essential health services to patients in need. Dentistry is also very demanding; mentally, physically, and even emotionally. Little is known about the health of dentists and how it compares to the health of the general population. The aim of the present study was to report on the general health and health practices of dentists in Massachusetts.MethodsA medical health and health practices survey was developed from the Delaware Valley Community Health Center and customized. The surveys contained 36 questions relating to demographics, general health, and health practices.ResultsA total of 399 dentists completed the survey. Of those who responded to the survey, 78.2% were males, 32.6% were 56‐65 years of age, 23.1% were 66‐75 years of age, and 21.6% were 46‐55 years of age.ConclusionThis pilot study highlights several health issues where dentists seem to have a lower incidence than the general population: asthma, depression, diabetes, hearing loss, obesity, smoking, sleep apnea, and thyroid disease. However, there are some health issues where dentists have a higher incidence than the general population: taking at least one prescription medication, gastroesophageal reflux disease, some form of cancer, back pain, neck pain, headache, osteoarthritis, rheumatic arthritis, psoriatic arthritis, and alcohol abuse.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/139952/1/jicd12263_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/139952/2/jicd12263.pd

A heat transfer with a source: the complete set of invariant difference schemes

In this letter we present the set of invariant difference equations and meshes which preserve the Lie group symmetries of the equation u_{t}=(K(u)u_{x})_{x}+Q(u). All special cases of K(u) and Q(u) that extend the symmetry group admitted by the differential equation are considered. This paper completes the paper [J. Phys. A: Math. Gen. 30, no. 23 (1997) 8139-8155], where a few invariant models for heat transfer equations were presented.Comment: arxiv version is already officia