1,843 research outputs found
Gut morphology of the Otomyine rodents: an arid-mesic comparison
In this article we examine the gut morphology of the only three arid-occurring otomyine rodents; Brantsâ whistling rat, Parotomys brantsii, Littledaleâs whistling rat, Parotomys littledalei and the Karoo bush rat, Otomys unisulcatus and relate this to the semi-arid environment in which they are endemic. All three otomyine rodents display a gastro-intestinal system well suited to a wholly herbivorous diet, with a well-developed caecum and relatively long large intestine. Despite the broad similarity in the gross gastro-intestinal anatomy between the species examined in this study and their mesic-occurring otomyine counterparts, the results suggest an elongation of the large intestine, with a concurrent reduction in the size of the small intestine In the arid-occurring species. We argue that this trend may be related to water conservation and is supported by the distribution of the three species, with P. littledalei, which occurs in the most arid areas of the three, having the longest large intestine
The internal structure of situational judgement tests reflects candidate main effects: not dimensions or situations
Despite their popularity and capacity to predict performance, there is no clear consensus on the internal measurement characteristics of situational judgement tests (SJTs). Contemporary propositions in the literature focus on treating SJTs as methods, as measures of dimensions, or as measures of situational responses. However, empirical evidence relating to the internal structure of SJT scores is lacking. Using generalizability theory, we decomposed multiple sources of variance for three different SJTs used with different samples of job candidates (N1 = 2,320; N2 = 989; N3 = 7,934). Results consistently indicated that (a) the vast majority of reliable observed score variance reflected SJT-specific candidate main effects, analogous to a general judgment factor and that (b) the contribution of dimensions and situations to reliable SJT variance was, in relative terms, negligible. These findings do not align neatly with any of the proposals in the contemporary literature; however they do suggest an internal structure for SJTs
Understanding pattern scaling errors across a range of emissions pathways
The regional climate impacts of hypothetical future emissions scenarios can be estimated by combining Earth system model simulations with a linear pattern scaling model such as MESMER (Modular Earth System Model Emulator with spatially Resolved output), which uses estimated patterns of the local response per degree of global temperature change. Here we use the mean trend component of MESMER to emulate the regional pattern of the surface temperature response based on historical single-forcer and future Shared Socioeconomic Pathway (SSP) CMIP6 (Coupled Model Intercomparison Project Phase 6) simulations. Errors in the emulations for selected target scenarios (SSP1â1.9, SSP1â2.6, SSP2â4.5, SSP3â7.0, and SSP5â8.5) are decomposed into two components, namely (1) the differences in scaling patterns between scenarios as a consequence of varying combinations of external forcings and (2) the intrinsic time series differences between the local and global responses in the target scenario. The time series error is relatively small for high-emissions scenarios, contributing around 20â% of the total error, but is similar in magnitude to the pattern error for lower-emissions scenarios. This irreducible time series error limits the efficacy of linear pattern scaling for emulating strong mitigation pathways and reduces the dependence on the predictor pattern used. The results help guide the choice of predictor scenarios for simple climate models and where to target for the introduction of other dependent variables beyond global surface temperature into pattern scaling models
Cosmic D-Strings and Vortons in Supergravity
Recent developments in string inspired models of inflation suggest that
D-strings are formed at the end of inflation. Within the supergravity model of
D-strings there are 2(n-1) chiral fermion zero modes for a D-string of winding
n. Using the bounds on the relic vorton density, we show that D-strings with
winding number n>1 are more strongly constrained than cosmic strings arising in
cosmological phase transitions. The D-string tension of such vortons, if they
survive until the present, has to satisfy 8\pi G_N \mu \lesssim p 10^{-26}
where p is the intercommutation probability. Similarly, D-strings coupled with
spectator fermions carry currents and also need to respect the above bound.
D-strings with n=1 do not carry currents and evade the bound. We discuss the
coupling of D-strings to supersymmetry breaking. When a single U(1) gauge group
is present, we show that there is an incompatibility between spontaneous
supersymmetry breaking and cosmic D-strings. We propose an alternative
mechanism for supersymmetry breaking, which includes an additional U(1), and
might alleviate the problem. We conjecture what effect this would have on the
fermion zero modes.Comment: 11 page
Recommended from our members
A SENSITIVE PHOTOTHERMAL DEFLECTION TECHNIQUE FOR MEASURING ABSORPTION IN OPTICALLY THIN MEDIA
We present a highly sensitive and simple photothermal scheme for determining optical absorptions in condensed matter samples. {alpha}l values as low as 10{sup -7} and 10{sup -8} were measured for thin films and coatings and for liquids, respectively. A comparison with thermal lens effect is given, and the experimental factors limiting our sensitivity are discussed
Cold Plasma Dispersion Relations in the Vicinity of a Schwarzschild Black Hole Horizon
We apply the ADM 3+1 formalism to derive the general relativistic
magnetohydrodynamic equations for cold plasma in spatially flat Schwarzschild
metric. Respective perturbed equations are linearized for non-magnetized and
magnetized plasmas both in non-rotating and rotating backgrounds. These are
then Fourier analyzed and the corresponding dispersion relations are obtained.
These relations are discussed for the existence of waves with positive angular
frequency in the region near the horizon. Our results support the fact that no
information can be extracted from the Schwarzschild black hole. It is concluded
that negative phase velocity propagates in the rotating background whether the
black hole is rotating or non-rotating.Comment: 27 pages, 11 figures accepted for publication in Gen. Relat. & Gravi
Magnetic Flux of EUV Arcade and Dimming Regions as a Relevant Parameter for Early Diagnostics of Solar Eruptions - Sources of Non-Recurrent Geomagnetic Storms and Forbush Decreases
This study aims at the early diagnostics of geoeffectiveness of coronal mass
ejections (CMEs) from quantitative parameters of the accompanying EUV dimming
and arcade events. We study events of the 23th solar cycle, in which major
non-recurrent geomagnetic storms (GMS) with Dst <-100 nT are sufficiently
reliably identified with their solar sources in the central part of the disk.
Using the SOHO/EIT 195 A images and MDI magnetograms, we select significant
dimming and arcade areas and calculate summarized unsigned magnetic fluxes in
these regions at the photospheric level. The high relevance of this eruption
parameter is displayed by its pronounced correlation with the Forbush decrease
(FD) magnitude, which, unlike GMSs, does not depend on the sign of the Bz
component but is determined by global characteristics of ICMEs. Correlations
with the same magnetic flux in the solar source region are found for the GMS
intensity (at the first step, without taking into account factors determining
the Bz component near the Earth), as well as for the temporal intervals between
the solar eruptions and the GMS onset and peak times. The larger the magnetic
flux, the stronger the FD and GMS intensities are and the shorter the ICME
transit time is. The revealed correlations indicate that the main quantitative
characteristics of major non-recurrent space weather disturbances are largely
determined by measurable parameters of solar eruptions, in particular, by the
magnetic flux in dimming areas and arcades, and can be tentatively estimated in
advance with a lead time from 1 to 4 days. For GMS intensity, the revealed
dependencies allow one to estimate a possible value, which can be expected if
the Bz component is negative.Comment: 27 pages, 5 figures. Accepted for publication in Solar Physic
Active faulting within a megacity: the geometry and slip rate of the Pardisan thrust in central Tehran, Iran
Tehran, the capital city of Iran with a population of over 12 million, is one of the largest urban centres within the seismically active AlpineâHimalayan orogenic belt. Although several historic earthquakes have affected Tehran, their relation to individual faults is ambiguous for most. This ambiguity is partly due to a lack of knowledge about the locations, geometries and seismic potential of structures that have been obscured by dramatic urban growth over the past three decades, and which have covered most of the young geomorphic markers and natural exposures. Here we use aerial photographs from 1956, combined with an ~1 m DEM derived from stereo Pleiades satellite imagery to investigate the geomorphology of a growing anticline above a thrust faultâthe Pardisan thrustâwithin central Tehran. The topography across the ridge is consistent with a steep ramp extending from close to the surface to a depth of ~2 km, where it presumably connects with a shallow-dipping detachment. No primary fault is visible at the surface, and it is possible that the faulting dissipates in the near surface as distributed shearing. We use optically stimulated luminescence to date remnants of uplifted and warped alluvial deposits that are offset vertically across the Pardisan fault, providing minimum uplift and slip-rates of at least 1 mm yr. Our study shows that the faults within the Tehran urban region have relatively rapid rates of slip, are important in the regional tectonics, and have a great impact on earthquake hazard assessment of the city and surrounding region.Geological Survey of Iran, Christ Church College Oxford, Natural Environment Research Council, Economic and Social Research Counci
- âŠ