1,027 research outputs found
ILR Impact Brief - CEOs and Layoffs: Sometimes the CEO Suffers Similar Fate
Mass layoffs have become an all too familiar occurrence in the United States; statistics indicate that an average of 5.7% of all employees lose their jobs in a typical year. And while many cutbacks were once meant to be temporary – that is, until demand picked up or the plant was retooled for a new model or new product – these days they more often have a permanence intended to reduce costs and boost efficiency. Companies may expect certain outcomes from workforce realignments, such as higher profits and greater productivity, but sometimes the future of the company’s chief executive is also at stake.
Previous academic studies have found links between CEO tenure and company performance. For example, researchers have shown that the probability of management turnover decreases as a company\u27s stock price increases. In a slight variation on this theme, researchers have also shown that CEO resignations/firings tend to rise as a company’s prospects deteriorate. This particular study goes a step further and explores the relationship between layoff announcements (another indicator of company performance) and chief executives\u27 term in office
Observation of thermo-mechanical equilibration in the presence of a solid 4He conduit
We observe a thermo-mechanical effect when a chemical potential difference is
created by a temperature difference imposed between two liquid reservoirs
connected to each other through Vycor rods in series with solid hcp 4He. By
creating a temperature difference, , between the two reservoirs, we
induce a rate-limited growth of a pressure difference between the two
reservoirs, . In equilibrium is in
quantitative agreement with the thermo-mechanical effect in superfluid helium.
These observations confirm that below 600 mK a flux-limited flow exists
through the solid helium.Comment: 4 pages, 4 figure
Growth of solid hcp \^4He off the melting curve
We report studies of the growth of solid hcp \4he at pressures higher than
the bulk freezing pressure using a cell design that allows us to inject atoms
into the solid. Near the melting curve during injection we observe random
events during which the pressure recorded in the cell drops abruptly. These
events are accompanied by transient increases in the temperature of the cell.
We discuss these transients and conclude that they represent the solidification
of meta-stable liquid regions and the associated relief of strain in the local
solid. We also observe that further from the melting curve the transients are
no longer recorded, but that we can continue to add atoms to the solid,
increasing its density at fixed volume. We document these changes in density
with respect to changes in the chemical potential as a function of temperature
and discuss these in the context of recent theoretical work.Comment: 7 pages, 8 figure
Recommended from our members
Mass flux and solid growth in solid 4He: 60 mK - 700 mK
We use the thermo-mechanical effect to create a chemical potential difference between two liquid reservoirs connected to each other through Vycor rods in series with solid hcp 4He to confirm that a DC flux of atoms takes place below 600 mK, but find that the flux falls abruptly in the vicinity of 80 mK. It is impossible to add density to a solid freshly made at 60 mK and samples freshly made at 60 mK do not allow mass flux, even when raised in temperature to 200 mK. Solids created above 300 mK and cooled to 60 mK accept added density and demonstrate finite mass flux
Mass flow through solid 4He induced by the fountain effect
Using an apparatus that allows superfluid liquid 4He to be in contact with
hcp solid \4he at pressures greater than the bulk melting pressure of the
solid, we have performed experiments that show evidence for 4He mass flux
through the solid and the likely presence of superfluid inside the solid. We
present results that show that a thermomechanical equilibrium in quantitative
agreement with the fountain effect exists between two liquid reservoirs
connected to each other through two superfluid-filled Vycor rods in series with
a chamber filled with solid 4He. We use the thermomechanical effect to induce
flow through the solid and measure the flow rate. On cooling, mass flux appears
near T = 600 mK and rises smoothly as the temperature is lowered. Near T = 75
mK a sharp drop in the flux is present. The flux increases as the temperature
is reduced below 75 mK. We comment on possible causes of this flux minimum.Comment: 20 pages, 22 figures, 7 table
Observation of Mass Transport through Solid 4He
By use of a novel experimental design, one that provides for superfluid
helium in contact with bulk hcp 4He off the melting curve, we have observed the
DC transport of mass through a cell filled with solid 4He in the hcp region of
the phase diagram. Flow, which shows characteristics of a superflow, is seen to
be independent of the method used to grow the solid, but depends on pressure
and temperature. The temperature dependence suggests the possibility of
hysteresis.Comment: 1 zipped file, produces 16 page paper, with 20 figures; resubmitted
with typos corrected, a figure corrected, some discussion improved, and
additional references - still 16 pages and 20 figure
Quantum Monte Carlo Algorithm Based on Two-Body Density Functional Theory for Fermionic Many-Body Systems: Application to 3He
We construct a quantum Monte Carlo algorithm for interacting fermions using
the two-body density as the fundamental quantity. The central idea is mapping
the interacting fermionic system onto an auxiliary system of interacting
bosons. The correction term is approximated using correlated wave functions for
the interacting system, resulting in an effective potential that represents the
nodal surface. We calculate the properties of 3He and find good agreement with
experiment and with other theoretical work. In particular, our results for the
total energy agree well with other calculations where the same approximations
were implemented but the standard quantum Monte Carlo algorithm was usedComment: 4 pages, 3 figures, 1 tabl
Observation of Unusual Mass Transport in Solid hcp 4He
Solid 4He has been created off the melting curve by growth at nearly constant
mass via the "blocked capillary" technique and growth from the 4He superfluid
at constant temperature. The experimental apparatus allows injection of 4He
atoms from superfluid directly into the solid. Evidence for the superfluid-like
transport of mass through a sample cell filled with hcp solid 4He off the
melting curve is found. This mass flux depends on temperature and pressure.Comment: 4 final pages (after pdf), including 4 image
Bleaching in foraminifera with algal symbionts: implications for reef monitoring and risk asessment
Reef-dwelling larger foraminifers share key characteristics with reefbuilding corals: they are prolific producers of calcium carbonate, they are physiologically dependent upon algal endosymbionts, and representatives of both groups have suffered bleaching episodes in recent decades. Since 1991, bleaching has been observed in populations of Amphistegina in all subtropical oceans, with peak bleaching in 1992 and secondary peaks in 1998 and 2005. Amphistegina populations exhibiting chronic, intermediate-intensity bleaching characteristically show anomalously high incidences of shell breakage, shell deformities, evidence of predation, and microbial infestation. Asexual reproduction is profoundly affected; broods from partly bleached parents typically have fewer individuals, many of which are anomalous in shape and size. Key differences between bleaching in corals and Amphistegina are that corals typically bleach by expelling their symbionts, while Amphistegina bleach when damaged symbionts are digested, and that mass coral bleaching requires high light but correlates most consistently with elevated temperatures, while bleaching in Amphistegina is induced by light. Amphistegina are particularly sensitive to the shorter (300-490 nm) wavelengths of solar radiation, which have increased in intensity relative to longer visible wavelengths (>;490-700 nm) in clear reef waters over the past 30 years as a consequence of stratospheric ozone depletion. Abundances and visual assessments of Amphistegina populations can be used as a low-cost risk-assessment tool. These protists are sensitive to environmental conditions over days to weeks, and provide a method to quickly distinguish between water quality (local) and photo-oxidative (global) stresses. Risk assessments based on the combined use of in situ measurements and low-cost indicators can provide resource managers with essential information to decide when more costly chemical or molecular procedures are needed to determine local sources of stress
Bound states of 3He at the edge of a 4He drop on a cesium surface
We show that small amounts of 3He atoms, added to a 4He drop deposited on a
flat cesium surface at zero temperature, populate bound states localized at the
contact line. These edge states show up for drops large enough to develop well
defined surface and bulk regions together with a contact line, and they are
structurally different from the well-known Andreev states that appear at the
free surface and at the liquid-solid interface of films. We illustrate the
one-body density of 3He in a drop with 1000 4He atoms, and show that for
sufficiently large number of impurities, the density profiles spread beyond the
edge, coating both the curved drop surface and its flat base and eventually
isolating it from the substrate.Comment: 10 pages and 7 figures. Submitted to PR
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