31,347 research outputs found
Particle Dynamics in Damped Nonlinear Quadrupole Ion Traps
We examine the motions of particles in quadrupole ion traps as a function of
damping and trapping forces, including cases where nonlinear damping or
nonlinearities in the electric field geometry play significant roles. In the
absence of nonlinearities, particles are either damped to the trap center or
ejected, while their addition brings about a rich spectrum of stable closed
particle trajectories. In three-dimensional (3D) quadrupole traps, the extended
orbits are typically confined to the trap axis, and for this case we present a
1D analysis of the relevant equation of motion. We follow this with an analysis
of 2D quadrupole traps that frequently show diamond-shaped closed orbits. For
both the 1D and 2D cases we present experimental observations of the calculated
trajectories in microparticle ion traps. We also report the discovery of a new
collective behavior in damped 2D microparticle ion traps, where particles
spontaneously assemble into a remarkable knot of overlapping, corotating
diamond orbits, self-stabilized by air currents arising from the particle
motion
Are We Understating the Impact of Economic Conditions on Welfare Rolls?
In this brief we argue that welfare participation is more sensitive to economic conditions than previously believed. Why? Prior research focused on short-term economic fluctuations and ignored differences between high- and low-skilled workers. As welfare is long-term (i.e., permanent) it makes more sense to make comparisons with long-term economic trends. Also, since low-skilled workers are more likely to end up on welfare, it is proper to focus on their economic opportunities. Thus, we focus on the long-term impact of economic conditions on welfare participation, and we concentrate our analysis on low-skilled workers. Specifically, we analyze long-term changes in the supply of high-paying jobs for coal and steel workers as they affect certain heavy coal- and steel-producing regions of the United States during the 1970s and 1980s. Our findings indicate that welfare participation in these regions closely mirrors the long-term local availability of high-paying jobs for low-skilled workers. This has serious policy implications for the long-term success of welfare reform.
Structure, bonding and morphology of hydrothermally synthesised xonotlite
The authors have systematically investigated the role of synthesis conditions upon the structure and morphology of xonotlite. Starting with a mechanochemically prepared, semicrystalline phase with Ca/Si=1, the authors have prepared a series of xonotlite samples hydrothermally, at temperatures between 200 and 250 degrees C. Analysis in each case was by X-ray photoelectron spectroscopy, environmental scanning electron microscopy and X-ray diffraction. The authorsâ use of a much lower water/solid ratio has indirectly confirmed the âthrough solutionâ mechanism of xonotlite formation, where silicate dissolution is a key precursor of xonotlite formation. Concerning the role of temperature, too low a temperature (~200 degrees C) fails to yield xonotlite or leads to increased number of structural defects in the silicate chains of xonotlite and too high a temperature (>250 degrees C) leads to degradation of the xonotlite structure, through leaching of interchain calcium. Synthesis duration meanwhile leads to increased silicate polymerisation due to diminishing of the defects in the silicate chains and more perfect crystal morphologies
The Agricultural Emergency in Iowa, I. The Situation Today
The major problems that the present depression has forced upon agriculture can be grouped under three heads : 1. Low prices for agricultural products. 2. High fixed charges on mortgage and other indebtedness in relation to income. 3. High truces in relation to income. The gravity of these problems is perhaps not comprehended by those outside of agriculture itself. The average man hears of 10 cent corn and $3.00 hogs, but he does not grasp the significance of these prices; he does not realize the meaning of the events· of the past year for agriculture, nor does he realize what is going to happen to agriculture during the next 12 months if some program of action is not put into effect
Apparatus for measuring thermal conductivity Patent
Development of apparatus for measuring thermal conductivit
Are Children "Normal"?
We examine Becker's (1960) contention that children are "normal." For the cross section of non-Hispanic white married couples in the U.S., we show that when we restrict comparisons to similarly-educated women living in similarly-expensive locations, completed fertility is positively correlated with the husband's income. The empirical evidence is consistent with children being "normal." In an effort to show causal effects, we analyze the localized impact on fertility of the mid-1970s increase in world energy prices â an exogenous shock that substantially increased men's incomes in the Appalachian coal-mining region. Empirical evidence for that population indicates that fertility increases in men's income.economics of fertility, location choice, Appalachian fertility
Blade loss transient dynamics analysis. Volume 3: User's manual for TETRA program
The users manual for TETRA contains program logic, flow charts, error messages, input sheets, modeling instructions, option descriptions, input variable descriptions, and demonstration problems. The process of obtaining a NASTRAN 17.5 generated modal input file for TETRA is also described with a worked sample
Effects of low level military training flights on wading bird colonies in Florida
During 1983 and 1984 the effect of low level military training
flights on the establishment. size and reproductive success of wading
bird colonies was studied in Florida. Based on the indirect evidence
of colony distributions and turnover rates in relation to military
areas (training routes designated to 500 feet or less above ground
level and military operations areas). there was no demonstrated effect
of military activity on wading bird colony establishment or size on a
statewide basis. Colony distributions were random with respect to
military areas and turnover rates were within 2% when military and
non-military areas were compared. Colony distributions and turnover
rates, however. were related to the amount and type.Les tuer-tne or
freshwater) of wetland. respectively.
During two breeding seasons the behavioral responses and
reproductive success of selected species were monitored in a
non-habituated treatment colony (military overflights) and a control
colony (no overflights). Breeding wading birds responded to F-16
overflights at 420 knots indicated airspeed. 82-84% maximum rpm. 500
feet above ground level and sound levels ranging from 55-100 dBA by
exhibiting no response. looking up or changing position (usually to an
alert posture): no productivity limiting responses were observed.
High-nesting Great Egrets responded more than other species, nestling
Great Egrets and Cattle Egrets responded significantly (r <.05) more
intensely than adults of their respective species, and adults
responded less during incubation and late chick-rearing than at other
times. In addition, no differences in adult attendance, aggressive
interactions or chick feeding rates were observed to result from F-16 overflights. No evidence of habituation to overflights was noted.
Humans entering the colony or airboats approaching the colony vicinity
elicited the most severe responses (flushing and panic flights)
observed at both sites.
Since relatively little coastal military activity occurs at low
levels ( ~500 ft) and only one Brown Pelican colony (5-6% of the
breeding population) was located in such an area, the reproductive
success of five, more lIexposedll study species (Great Egrets, Snowy
Egrets, Tricolored Herons, Little Blue Herons, Cattle Egrets) nesting
in interior freshwater colonies was studied. Reproductive activity
including such factors as nest success, nestling survival, nestling
mortality, and nesting chronology was independent of F-16 overflights
but related to ecological factors including colony location, colony
characteristics and climatology. The responses to and effects of F-16
overflights, as reported here, should not be considered representative
of military aircraft at lower altitudes or greater noise levels. (194 pages
- âŠ