2,493 research outputs found
Acarine Fauna of Bird Nests
In summer, 1961, 10 nests, representing seven species of passeriform birds, were collected and processed in Berlese funnels to obtain the mites present. Representatives of 20 different families or superfamilies were identified in addition to five groups of larvae and nymphs which could not be identified to family. The families Eremaeidae and Dermanyssidae were most widely represented, and dermanyssids were most numerous. Mite populations are believed to become established in nests by (1) mites being brought into the nest by way of nest materials, (2) mites being brought into the nest on the bird itself, and (3) mites in their wanderings accidentally encountering the nests
Significance of the pericardium in human subjects: Effects on left ventricular volume, pressure and ejection
To assess the effect of the pericardium, left ventricular systolic function and diastolic compliance were studied in 15 patients before and after pericardiotomy during coronary artery surgery. Using first pass radionuclide angiography, curves for left ventricular systolic function (stroke work versus end-diastolic volume) and a measure of diastolic compliance (pulmonary capillary wedge pressure versus end-diastolic volume) were generated by changing body position to alter venous return. Left ventricular end-diastolic volume ranged from 41 to 111 ml/m2and pulmonary capillary wedge pressure from 0 to 24 mm Hg.No significant changes were found in blood pressure (150/83 to 148/82 mm Hg), heart rate (66.7 to 67.1 beats/min), cardiac index (2.38 to 2.41 liters/min per m2), ejection fraction (0.56 to 0.54), end-systolic volume index (31.4 to 32.2 ml/m2), end-diastolic volume index (65.9 to 69.5 ml/m2) or pulmonary capillary wedge pressure (7.5 to 7.3 mm Hg). The pericardium did not affect the curves relating stroke work and end-diastolic volume or those relating pulmonary capillary wedge pressure and end-diastolic volume. Thus, when filling pressure and volume are normal or only moderately elevated, the pericardium does not appear to affect left ventricular systolic function or diastolic compliance in patients
Renewing the Exploration Approach for Mid-Enthalpy Systems: Examples from Northern England and Scotland
After a promising start in the 1970s and 80s, the UK rather fell behind other countries in the search for viable mid-enthalpy
geothermal resources. This situation began to turn around in 2004, when the first of three deep geothermal exploration boreholes
were drilled in northern England. What distinguished these from earlier drilling in Cornwall was the deliberate search for naturallyhigh
permeability associated with major faults, especially those that have undergone strike-slip reactivation during the Cenozoic.
Boreholes at Eastgate in the North Pennines targeted buried radiothermal granite, whereas the 1,821m-deep Science Central
Borehole in Newcastle upon Tyne targeted a postulated deep sedimentary aquifer (the Fell Sandstones), which were inferred to be
connected laterally to the granitic heat source by a major fault (the reactivation of the Iapetus geo-suture). The drilling was in both
cases rewarded with impressive heat flows, and in the case of Eastgate with what is believed to be the highest permeability yet
found in a deep granite batholith anywhere in the world. In parallel with these developments, a re-assessment was made of the preexisting
geothermal heat flow database for the UK, applying newly-standardised correction protocols for palaeoclimatic and
topographic distortions, which were found to be particularly marked in Scotland (where only shallow boreholes had been used to
establish geothermal gradients in the original 1980s analysis), Similar prospects in northern England (similar to that drilled at
Science Central) are now the focus of commercial exploration efforts. Appraisal of fault dispositions relative to the present-day
maximum compressive stress azimuth are being used to identify the most promising areas for intersecting fault-related permeability
at depth. New geophysical tools – most notably atomic dielectric resonance scanning – are also being appraised for their ability to
directly detect features (such as hot brines) which are indicative of localised convection in target fault zones and aquifers
Short-term studies underestimate 30-generation changes in a butterfly metapopulation
Most studies of rare and endangered species are based on work carried out within one generation, or over one to a few generations of the study organism. We report the results of a study that spans 30 generations (years) of the entire natural range of a butterfly race that is endemic to 35 km2 of north Wales, UK. Short-term studies (surveys in single years and dynamics over 4 years) of this system led to the prediction that the regional distribution would be quite stable, and that colonization and extinction dynamics would be relatively unimportant. However, a longer-term study revealed unexpectedly high levels of population turnover (local extinction and colonization), affecting 18 out of the 20 patches that were occupied at any time during the period. Modelling the system (using the 'incidence function model' (IFM) for metapopulations) also showed higher levels of colonization and extinction with increasing duration of the study. The longer-term dynamics observed in this system can be compared, at a metapopulation level, with the increased levels of variation observed with increasing time that have been observed in single populations. Long-term changes may arise from local changes in the environment that make individual patches more or less suitable for the butterfly, or from unusual colonization or extinction events that take metapopulations into alternative states. One implication is that metapopulation and population viability analyses based on studies that cover only a few animal or plant generations may underestimate extinction threats
Clinical significance of perioperative Q-wave myocardial infarction: The Emory Angioplasty versus Surgery Trial
AbstractObjective: The primary end point of the Emory Angioplasty versus Surgery Trial was a composite of three events: death, Q-wave infarction, and a new large defect on 3-year postoperative thallium scan. This study examines the clinical significance of Q-wave infarction in the surgical cohort (194 patients) of the Emory trial. Methods: Twenty patients (10.3%) with Q-wave infarctions were identified: 13 patients had inferior Q-wave infarctions and seven patients had anterior, lateral, septal, or posterior Q-wave infarctions (termed anterior Q-wave infarctions). Results: In the inferior Q-wave infarction group, postoperative cardiac catheterization (at 1 year or 3 years) in 11 patients revealed normal ejection fraction (ejection fraction >55%) in 10 (91%), no wall motion abnormalities in 10 (91%), and all grafts patent in 10 (91%). In the anterior Q-wave infarction group, postoperative catheterizatiOn in six patients revealed normal ejection fractions in five (83%), no wall motion abnormalities in three (50%), and all grafts patent in three (50%). Average peak postoperative creatine kinase MB levels were as follows: no Q-wave infarction (n = 174) 37 ± 43 IU/L, inferior Q-wave infarction 40 ± 27 IU/L, and anterior Q-wave infarction 58 ± 38 IU/L. Mortality in the 20 patients with Q-wave infarctions was 5% (1/20) at 3 years; in patients without a Q-wave infarction it was 6.3% (11/174) (p = 0.64). Of 17 patients with a Q-wave infarction who underwent postoperative catheterization, 11 (65%) had a normal ejection fraction, normal wall motion, and all grafts patent with an uneventful 3-year postoperative course. Conclusions: The core laboratory screening of postoperative electrocardiograms, particularly in the case of inferior Q-wave infarctions, appears to identify a number of patients as having a Q-wave infarction with minimal clinical significance. Q-wave infarction identified in the postoperative period seems to be a weak end point with little prognostic significance and therefore not valuable for future randomized trials. (J Thorac Cardiovasc Surg 1996;112:1447-54
Sharp-Tailed Grouse Nest Survival and Nest Predator Habitat Use in North Dakota’s Bakken Oil Field
Recent advancements in extraction technologies have resulted in rapid increases of gas and oil development across the United States and specifically in western North Dakota. This expansion of energy development has unknown influences on local wildlife populations and the ecological interactions within and among species. Our objectives for this study were to evaluate nest success and nest predator dynamics of sharp-tailed grouse (Tympanuchus phasianellus) in two study sites that represented areas of high and low energy development intensities in North Dakota. During the summers of 2012 and 2013, we monitored 163 grouse nests using radio telemetry. Of these, 90 nests also were monitored using miniature cameras to accurately determine nest fates and identify nest predators. We simultaneously conducted predator surveys using camera scent stations and occupancy modeling to estimate nest predator occurrence at each site. American badgers (Taxidea taxus) and striped skunks (Mephitis mephitis) were the primary nest predators, accounting for 56.7% of all video recorded nest depredations. Nests in our high intensity gas and oil area were 1.95 times more likely to succeed compared to our minimal intensity area. Camera monitored nests were 2.03 times more likely to succeed than non-camera monitored nests. Occupancy of mammalian nest predators was 6.9 times more likely in our study area of minimal gas and oil intensity compared to the high intensity area. Although only a correlative study, our results suggest energy development may alter the predator community, thereby increasing nest success for sharp-tailed grouse in areas of intense development, while adjacent areas may have increased predator occurrence and reduced nest success. Our study illustrates the potential influences of energy development on the nest predator—prey dynamics of sharp-tailed grouse in western North Dakota and the complexity of evaluating such impacts on wildlife
Observational Cosmology in Macroscopic Gravity
We discuss the construction of cosmological models within the framework of
Macroscopic Gravity (MG), which is a theory that models the effects of
averaging the geometry of space-time on large scales. We find new exact
spatially homogeneous and isotropic FLRW solutions to the MG field equations,
and investigate large-scale perturbations around them. We find that any
inhomogeneous perturbations to the averaged geometry are severely restricted,
but that possible anisotropies in the correlation tensor can have dramatic
consequences for the measurement of distances. These calculations are a first
step within the MG approach toward developing averaged cosmological models to a
point where they can be used to interpret real cosmological data, and hence to
provide a working alternative to the "concordance" LCDM model.Comment: 22 page
Back Reaction And Local Cosmological Expansion Rate
We calculate the back reaction of cosmological perturbations on a general
relativistic variable which measures the local expansion rate of the Universe.
Specifically, we consider a cosmological model in which matter is described by
a single field. We analyze back reaction both in a matter dominated Universe
and in a phase of scalar field-driven chaotic inflation. In both cases, we find
that the leading infrared terms contributing to the back reaction vanish when
the local expansion rate is measured at a fixed value of the matter field which
is used as a clock, whereas they do not appear to vanish if the expansion rate
is evaluated at a fixed value of the background time. We discuss possible
implications for more realistic models with a more complicated matter sector.Comment: 7 pages, No figure
Classification of phase transitions and ensemble inequivalence, in systems with long range interactions
Systems with long range interactions in general are not additive, which can
lead to an inequivalence of the microcanonical and canonical ensembles. The
microcanonical ensemble may show richer behavior than the canonical one,
including negative specific heats and other non-common behaviors. We propose a
classification of microcanonical phase transitions, of their link to canonical
ones, and of the possible situations of ensemble inequivalence. We discuss
previously observed phase transitions and inequivalence in self-gravitating,
two-dimensional fluid dynamics and non-neutral plasmas. We note a number of
generic situations that have not yet been observed in such systems.Comment: 42 pages, 11 figures. Accepted in Journal of Statistical Physics.
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