111 research outputs found
Predicting occupational strain and job satisfaction: the role of stress, coping, personality, and affectivity variables
Four studies employed path analysis to examine how measures of occupational stressors, coping resources, and negative affectivity (NA) and positive affectivity (PA) interact to predict occupational strain. The Occupational Stress Inventory (Osipow & Spokane, 1987) was used to measure stress, strain, and coping. The Positive and Negative Affectivity Schedule (Watson, Clark, & Tellegen, 1988) was
used for the affectivity variables. The hypothesised model showed NA and PA as background dispositional variables that influenced relations among stress, strain, and coping while still allowing stress and coping to have a direct influence on strain. Goodness of fit indices were acceptable with the model predicting 15 per cent of the variance in stress, 24 per cent of coping, and 70 per cent of strain. Study 2 replicated these findings. Study 3 added a positive outcome variable, job satisfaction (JSI: Brayfield & Rothe, 1951) to the model. The expanded model again fit the data well. A fourth study added a global measure of personality (NEO-FFI: Costa & McCrae, 1991) to the model tested in Study 3. Results indicated that personality measures did not add
anything to the prediction of job satisfaction and strain in a model that already included measures of stressors, coping resources, NA and PA. The series of four studies yielded a reliable structural model that highlights the influence of organizational and dispositional variables on occupational strain and job satisfaction
Linear Sigma Models for Open Strings
We formulate and study a class of massive N=2 supersymmetric gauge field
theories coupled to boundary degrees of freedom on the strip. For some values
of the parameters, the infrared limits of these theories can be interpreted as
open string sigma models describing D-branes in large-radius Calabi-Yau
compactifications. For other values of the parameters, these theories flow to
CFTs describing branes in more exotic, non-geometric phases of the Calabi-Yau
moduli space such as the Landau-Ginzburg orbifold phase. Some simple properties
of the branes (like large radius monodromies and spectra of worldvolume
excitations) can be computed in our model. We also provide simple worldsheet
models of the transitions which occur at loci of marginal stability, and of
Higgs-Coulomb transitions.Comment: 51 pages, 2 figures; very minor corrections, refs adde
D-terms and D-strings in open string models
We study the Fayet-Iliopoulos (FI) D-terms on D-branes in type II Calabi-Yau
backgrounds. We provide a simple worldsheet proof of the fact that, at tree
level, these terms only couple to scalars in closed string hypermultiplets. At
the one-loop level, the D-terms get corrections only if the gauge group has an
anomalous spectrum, with the anomaly cancelled by a Green-Schwarz mechanism. We
study the local type IIA model of D6-branes at SU(3) angles and show that, as
in field theory, the one-loop correction suffers from a quadratic divergence in
the open string channel. By studying the closed string channel, we show that
this divergence is related to a closed string tadpole, and is cancelled when
the tadpole is cancelled. Next, we study the cosmic strings that arise in the
supersymmetric phases of these systems in light of recent work of Dvali et. al.
In the type IIA intersecting D6-brane examples, we identify the D-term strings
as D4-branes ending on the D6-branes. Finally, we use N=1 dualities to relate
these results to previous work on the FI D-term of heterotic strings.Comment: 29 pages, 5 figures; v2: improved referencin
The target space geometry of N=(2,1) string theory
We describe the constraints on the target space
geometry of the heterotic superstring due to the left-moving
supersymmetry and currents. In the fermionic description of the internal
sector supersymmetry is realized quantum mechanically, so that both tree-level
and one-loop effects contribute to the order
constraints. We also discuss the physical interpretation of the resulting
target space geometry in terms of configurations of a -dimensional object
propagating in a -dimensional spacetime with a null isometry, which has
recently been suggested as a unified description of string and M theory.Comment: 41 pages, 5 figures, standard LaTeX, uses epsf.tex. Some typos
corrected, discussion in footnote 1 correcte
Small Numbers from Tunneling Between Brane Throats
Generic classes of string compactifications include ``brane throats''
emanating from the compact dimensions and separated by effective potential
barriers raised by the background gravitational fields. The interaction of
observers inside different throats occurs via tunnelling and is consequently
weak. This provides a new mechanism for generating small numbers in Nature. We
apply it to the hierarchy problem, where supersymmetry breaking near the
unification scale causes TeV sparticle masses inside the standard model throat.
We also design naturally long-lived cold dark matter which decays within a
Hubble time to the approximate conformal matter of a long throat. This may
soften structure formation at galactic scales and raises the possibility that
much of the dark matter of the universe is conformal matter. Finally, the
tunnelling rate shows that the coupling between throats, mediated by bulk
modes, is stronger than a naive application of holography suggests.Comment: 11 pages, 2 figures. Small corrections to match the published versio
Signatures of Short Distance Physics in the Cosmic Microwave Background
We systematically investigate the effect of short distance physics on the
spectrum of temperature anistropies in the Cosmic Microwave Background produced
during inflation. We present a general argument-assuming only low energy
locality-that the size of such effects are of order H^2/M^2, where H is the
Hubble parameter during inflation, and M is the scale of the high energy
physics.
We evaluate the strength of such effects in a number of specific string and M
theory models. In weakly coupled field theory and string theory models, the
effects are far too small to be observed. In phenomenologically attractive
Horava-Witten compactifications, the effects are much larger but still
unobservable. In certain M theory models, for which the fundamental Planck
scale is several orders of magnitude below the conventional scale of grand
unification, the effects may be on the threshold of detectability.
However, observations of both the scalar and tensor fluctuation contributions
to the Cosmic Microwave Background power spectrum-with a precision near the
cosmic variance limit-are necessary in order to unambiguously demonstrate the
existence of these signatures of high energy physics. This is a formidable
experimental challenge.Comment: 49 pages, 2 figures. References added, minor typos correcte
The Kalanchoe genome provides insights into convergent evolution and building blocks of crassulacean acid metabolism
Crassulacean acid metabolism (CAM) is a water-use efficient adaptation of photosynthesis that has evolved independently many times in diverse lineages of flowering plants. We hypothesize that convergent evolution of protein sequence and temporal gene expression underpins the independent emergences of CAM from C3 photosynthesis. To test this hypothesis, we generate a de novo genome assembly and genome-wide transcript expression data for Kalanchoë fedtschenkoi, an obligate CAM species within the core eudicots with a relatively small genome (~260 Mb). Our comparative analyses identify signatures of convergence in protein sequence and re-scheduling of diel transcript expression of genes involved in nocturnal CO2 fixation, stomatal movement, heat tolerance, circadian clock, and carbohydrate metabolism in K. fedtschenkoi and other CAM species in comparison with non-CAM species. These findings provide new insights into molecular convergence and building blocks of CAM and will facilitate CAM-into-C3 photosynthesis engineering to enhance water-use efficiency in crops
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