378 research outputs found
City slickers: poor performance does not deter \u3cem\u3eAnolis\u3c/em\u3e lizards from using artificial substrates in human‐modified habitats
1. As animals move through their environments, they encounter a variety of substrates, which have important effects on their locomotor performance. Habitat modification can alter the types of substrates available for locomotion. In particular, many types of artificial substrates have been added to urban areas, but effects of these novel surfaces on animal locomotion are little known. In this study, we assessed locomotor performance of two Anolis lizard species (A. cristatellus and A. stratulus) on substrates that varied in inclination and surface roughness. Rough substrates represented the tree trunks and branches typically used in natural forest habitats, whereas smooth, vertical substrates captured the qualities of artificial surfaces, such as posts and walls, available in human‐modified habitats. We then observed habitat use to test the habitat constraint hypothesis – that lizards should more frequently occupy portions of the habitat in which they perform better. Increased inclination and decreased surface roughness caused lizards to run slower. Both A. cristatellus and A. stratulus ran slowest on the smooth, vertical surface, and A. cristatellus often slipped and fell on this surface. In contrast to predictions, both species frequently used smooth, vertical substrates in the wild. Anolis cristatellus occupied artificial substrates 73% of the time in human‐modified habitats despite performing worse than A. stratulus on the smooth, vertical track. We therefore rejected the habitat constraint hypothesis for anoles in these human‐modified habitats. Despite overall poor performance on the smooth, vertical track, A. cristatellus had a significant morphology–performance relationship that supports the prediction that selection should favour smaller lizards with relatively longer limbs in human‐modified habitats. The smaller bodied A. stratulus performed better than A. cristatellus on smooth, vertical substrates and therefore may not be exposed to the same selective pressures. We contend that habitat modification by humans may alter morphology‐performance–habitat use relationships found in natural habitats. This may lead to changes in selective pressures for some species, which may influence their ability to occupy human‐modified habitats such as cities
Synthesis of chitosan oligomers/propolis/silver-nanoparticles composite systems and study of their activity against Diplodia seriata
The synthesis and characterization of composites of oligomeric chitosan with propolis extract which allow the incorporation of a third component (silver nanoparticles) are reported, together with their application in aqueous or hydroalcoholic solutions with a view to the formation of adhesive substances or nanofilms for the protection of vineyards against harmful xylophagous fungi. The antimicrobial properties of the association of the two biological products or those resulting from the incorporation of silver nanoparticles (NPs) are studied and discussed. The efficacy of the chitosan oligomers/propolis/silver NPs ternary system is assessed in vitro for Diplodia fungi. A preliminary study on the convenience of replacing propolis with gentisic acid is also presented
White-etching matter in bearing steel. Part II: Distinguishing cause and effect in bearing steel failure
The premature failure of large bearings of the type used in wind turbines, possibly through a mechanism called “white-structure flaking”, has triggered many studies of microstructural damage associated with “white-etching areas” created during rolling contact fatigue, although whether they are symptoms or causes of failure is less clear. Therefore, some special experiments have been conducted to prove that white-etching areas are the consequence, and not the cause, of damage. By artificially introducing a fine dispersion of microcracks in the steel through heat treatment and then subjecting the sample to rolling contact fatigue, manifestations of hard white-etching matter have been created to a much greater extent than samples similarly tested without initial cracks. A wide variety of characterization tools has been used to corroborate that the white areas thus created have the same properties as reported observations on real bearings. Evidence suggests that the formation mechanism of the white-etching regions involves the rubbing and beating of the free surfaces of cracks, debonded inclusions, and voids under repeated rolling contact. It follows that the focus in avoiding early failure should be in enhancing the toughness of the bearing steel in order to avoid the initial microscopic feature event.Funding by CONACyT, the
Cambridge Overseas Trust, and the Roberto Rocca Education Programme
is highly appreciated and acknowledged.This is the accepted manuscript version. The final published version is available from Springer at http://link.springer.com/article/10.1007%2Fs11661-014-2431-x
Second-generation colon capsule endoscopy compared with colonoscopy
Colon capsule endoscopy (CCE) represents a noninvasive technology
that allows visualization of the colon without requiring sedation and air
insufflation. A second-generation colon capsule endoscopy system (PillCam Colon
2) (CCE-2) was developed to increase sensitivity for colorectal polyp detection
compared with the first-generation system. OBJECTIVE: To assess the feasibility,
accuracy, and safety of CCE-2 in a head-to-head comparison with colonoscopy.
DESIGN AND SETTING: Prospective, multicenter trial including 8 European sites.
PATIENTS: This study involved 117 patients (mean age 60 years). Data from 109
patients were analyzed. INTERVENTION: CCE-2 was prospectively compared with
conventional colonoscopy as the criterion standard for the detection of
colorectal polyps that are >/=6 mm or masses in a cohort of patients at average
or increased risk of colorectal neoplasia. Colonoscopy was independently
performed within 10 hours after capsule ingestion or on the next day. MAIN
OUTCOME MEASUREMENTS: CCE-2 sensitivity and specificity for detecting patients
with polyps >/=6 mm and >/=10 mm were assessed. Capsule-positive but
colonoscopy-negative cases were counted as false positive. Capsule excretion
rate, level of bowel preparation, and rate of adverse events also were assessed.
RESULTS: Per-patient CCE-2 sensitivity for polyps >/=6 mm and >/=10 mm was 84%
and 88%, with specificities of 64% and 95%, respectively. All 3 invasive
carcinomas were detected by CCE-2. The capsule excretion rate was 88% within 10
hours. Overall colon cleanliness for CCE-2 was adequate in 81% of patients.
LIMITATIONS: Not unblinding the CCE-2 results at colonoscopy; heterogenous
patient population; nonconsecutive patients. CONCLUSION: In this European,
multicenter study, CCE-2 appeared to have a high sensitivity for the detection of
clinically relevant polypoid lesions, and it might be considered an adequate tool
for colorectal imaging
Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
Data collected by the Pierre Auger Observatory through 31 August 2007 showed
evidence for anisotropy in the arrival directions of cosmic rays above the
Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{eV}. The
anisotropy was measured by the fraction of arrival directions that are less
than from the position of an active galactic nucleus within 75 Mpc
(using the V\'eron-Cetty and V\'eron catalog). An updated
measurement of this fraction is reported here using the arrival directions of
cosmic rays recorded above the same energy threshold through 31 December 2009.
The number of arrival directions has increased from 27 to 69, allowing a more
precise measurement. The correlating fraction is , compared
with expected for isotropic cosmic rays. This is down from the early
estimate of . The enlarged set of arrival directions is
examined also in relation to other populations of nearby extragalactic objects:
galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in
hard X-rays by the Swift Burst Alert Telescope. A celestial region around the
position of the radiogalaxy Cen A has the largest excess of arrival directions
relative to isotropic expectations. The 2-point autocorrelation function is
shown for the enlarged set of arrival directions and compared to the isotropic
expectation.Comment: Accepted for publication in Astroparticle Physics on 31 August 201
Atmospheric effects on extensive air showers observed with the Surface Detector of the Pierre Auger Observatory
Atmospheric parameters, such as pressure (P), temperature (T) and density,
affect the development of extensive air showers initiated by energetic cosmic
rays. We have studied the impact of atmospheric variations on extensive air
showers by means of the surface detector of the Pierre Auger Observatory. The
rate of events shows a ~10% seasonal modulation and ~2% diurnal one. We find
that the observed behaviour is explained by a model including the effects
associated with the variations of pressure and density. The former affects the
longitudinal development of air showers while the latter influences the Moliere
radius and hence the lateral distribution of the shower particles. The model is
validated with full simulations of extensive air showers using atmospheric
profiles measured at the site of the Pierre Auger Observatory.Comment: 24 pages, 9 figures, accepted for publication in Astroparticle
Physic
The Fluorescence Detector of the Pierre Auger Observatory
The Pierre Auger Observatory is a hybrid detector for ultra-high energy
cosmic rays. It combines a surface array to measure secondary particles at
ground level together with a fluorescence detector to measure the development
of air showers in the atmosphere above the array. The fluorescence detector
comprises 24 large telescopes specialized for measuring the nitrogen
fluorescence caused by charged particles of cosmic ray air showers. In this
paper we describe the components of the fluorescence detector including its
optical system, the design of the camera, the electronics, and the systems for
relative and absolute calibration. We also discuss the operation and the
monitoring of the detector. Finally, we evaluate the detector performance and
precision of shower reconstructions.Comment: 53 pages. Submitted to Nuclear Instruments and Methods in Physics
Research Section
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