3,773 research outputs found
Predictability of catastrophic events: material rupture, earthquakes, turbulence, financial crashes and human birth
We propose that catastrophic events are "outliers" with statistically
different properties than the rest of the population and result from mechanisms
involving amplifying critical cascades. Applications and the potential for
prediction are discussed in relation to the rupture of composite materials,
great earthquakes, turbulence and abrupt changes of weather regimes, financial
crashes and human parturition (birth).Comment: Latex document of 22 pages including 6 ps figures, in press in PNA
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Experimental Measurements of Phase Space
Direct measurements of integrated phase-space densities, e.g., f(x,vy,t), have been made in an experiment. Using spectroscopically active ions, measurements in a plasma show the ion response, fi(x,v,t), to linear and nonlinear waves and phase-space particle bunching. Time-resolved measurements show coherent and incoherent phase-space density changes in the presence of waves, indicating that transitions to turbulence and chaos may be studied. The time, space, and velocity-space resolution may allow experimental tests of predictions from the Boltzmann equation
Ultrasonic locating devices for central venous cannulation: meta-analysis
OBJECTIVES: To assess the evidence for the clinical
effectiveness of ultrasound guided central venous
cannulation.
DATA SOURCES: 15 electronic bibliographic databases,
covering biomedical, science, social science, health
economics, and grey literature.
DESIGN: Systematic review and meta-analysis of
randomised controlled trials.
POPULATIONS: Patients scheduled for central venous
access.
INTERVENTION REVIEWED: Guidance using real time two
dimensional ultrasonography or Doppler needles and
probes compared with the anatomical landmark
method of cannulation.
DATA EXTRACTION: Risk of failed catheter placement
(primary outcome), risk of complications from
placement, risk of failure on first attempt at
placement, number of attempts to successful
catheterisation, and time (seconds) to successful
catheterisation.
DATA SYNTHESIS: 18 trials (1646 participants) were
identified. Compared with the landmark method, real
time two dimensional ultrasound guidance for
cannulating the internal jugular vein in adults was
associated with a significantly lower failure rate both
overall (relative risk 0.14, 95% confidence interval
0.06 to 0.33) and on the first attempt (0.59, 0.39 to
0.88). Limited evidence favoured two dimensional
ultrasound guidance for subclavian vein and femoral
vein procedures in adults (0.14, 0.04 to 0.57 and 0.29,
0.07 to 1.21, respectively). Three studies in infants
confirmed a higher success rate with two dimensional
ultrasonography for internal jugular procedures (0.15,
0.03 to 0.64). Doppler guided cannulation of the
internal jugular vein in adults was more successful
than the landmark method (0.39, 0.17 to 0.92), but the
landmark method was more successful for subclavian
vein procedures (1.48, 1.03 to 2.14). No significant
difference was found between these techniques for
cannulation of the internal jugular vein in infants. An
indirect comparison of relative risks suggested that
two dimensional ultrasonography would be more
successful than Doppler guidance for subclavian vein
procedures in adults (0.09, 0.02 to 0.38).
CONCLUSIONS: Evidence supports the use of two
dimensional ultrasonography for central venous
cannulation
Using Life History and Ecology as Tools to Manage a Threatened Salamander Species
Selected aspects of the life history and ecology of the small-mouthed salamander (Ambystoma texanum Matthes) relevant to the management of this threatened species in Iowa are presented. The population studied utilizes flooded woodland habitat during courtship, breeding and egg laying, and during the entire larval period. Larval foraging strategies in this habitat included ontogenetic but no diel shifts in prey selection. Synchronous, nocturnal breeding migration allowed effective use of drift fences fur capture of adults used in captive breeding, courtship behavior studies, and the estimation of breeding population size. Large numbers of spennatophores, apparently indiscriminate mate choice, and the relatively large number of eggs produced by females makes captive breeding programs potentially very successful. Because larvae are particularly vulnerable to predation by fish and larval tiger salamanders, ephemeral ponds are required for breeding and larval habitat. The primary management objective should be to preserve ephemeral woodland ponds and adjacent terrestrial habitat favorable for larval and adult survival
Mild acetabular dysplasia and risk of osteoarthritis of the hip : a case-control study
Objective To determine whether mild variation in acetabular depth (AD) and shape is a risk factor for osteoarthritis (OA) of the hip.
Methods The unaffected contralateral hip of patients with unilateral hip OA was compared with hips of asymptomatic controls without hip OA, derived from the Nottingham Genetics Osteoarthritis and Lifestyle case–control study. Standardised anteroposterior x-rays of the pelvis were used to measure centre edge (CE) angle and AD. Cut-off points for narrow CE angle and shallow AD were calculated from the control group (mean −1.96×SD). The relative risk of hip OA associated with each feature was estimated using OR and 95% CI and adjusted risks were calculated by logistic regression.
Results In controls, both the CE angle and the AD were lower in the left hip than in the right hip. The CE angle related to age in both hips, and AD of the right hip was lower in men than in women. The contralateral unaffected hip in patients with unilateral hip OA had a decreased CE angle and AD compared with controls, irrespective of side. The lowest tertile of the CE angle in contralateral hips was associated with an eightfold risk of OA (aOR 8.06, 95% CI 4.87 to 13.35) and the lowest tertile of AD was associated with a 2.5-fold risk of OA (aOR 2.53, 95% CI 1.28 to 5.00). Significant increases in the risk of OA were also found as the CE angle and AD decreased
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