669 research outputs found
Using the MitoB method to assess levels of reactive oxygen species in ecological studies of oxidative stress
In recent years evolutionary ecologists have become increasingly interested in the effects of reactive
oxygen species (ROS) on the life-histories of animals. ROS levels have mostly been inferred indirectly
due to the limitations of estimating ROS from in vitro methods. However, measuring ROS (hydrogen
peroxide, H2O2) content in vivo is now possible using the MitoB probe. Here, we extend and refine
the MitoB method to make it suitable for ecological studies of oxidative stress using the brown trout
Salmo trutta as model. The MitoB method allows an evaluation of H2O2 levels in living organisms over
a timescale from hours to days. The method is flexible with regard to the duration of exposure and
initial concentration of the MitoB probe, and there is no transfer of the MitoB probe between fish. H2O2
levels were consistent across subsamples of the same liver but differed between muscle subsamples
and between tissues of the same animal. The MitoB method provides a convenient method for
measuring ROS levels in living animals over a significant period of time. Given its wide range of possible
applications, it opens the opportunity to study the role of ROS in mediating life history trade-offs in
ecological settings
Effects of anisotropic interactions on the structure of animal groups
This paper proposes an agent-based model which reproduces different
structures of animal groups. The shape and structure of the group is the effect
of simple interaction rules among individuals: each animal deploys itself
depending on the position of a limited number of close group mates. The
proposed model is shown to produce clustered formations, as well as lines and
V-like formations. The key factors which trigger the onset of different
patterns are argued to be the relative strength of attraction and repulsion
forces and, most important, the anisotropy in their application.Comment: 22 pages, 9 figures. Submitted. v1-v4: revised presentation; extended
simulations; included technical results. v5: added a few clarification
Recreational drug use and use of drugs associated with chemsex among HIV-negative and HIV-positive heterosexual men and women attending sexual health and HIV clinics in England
Background: There is little information on the prevalence of recreational drug use among UK heterosexual men
and women, in particular on use of drugs associated with ‘chemsex’ within gay communities. The aim of this study
was to examine among HIV-negative and HIV-positive heterosexual men and women in England: (i) the prevalence
of recreational drug use (including use of drugs associated with chemsex), (ii) socio-economic/lifestyle correlates
of drug use, and (iii) the association of drug use with sexual behavior measures and mental health symptoms.
Methods: Data are from the AURAH study of HIV-negative individuals attending sexual health clinics across England (2013–2014) and the ASTRA study of HIV-positive individuals attending HIV outpatient clinics in England
(2011–2012). Prevalence of recreational drug use (past three months) and associations are presented separately
among the four sample groups: HIV-negative (N = 470) and HIV-positive (N = 373) heterosexual men and HIVnegative (N = 676) and HIV-positive (N = 637) women.
Results: The age standardized prevalence of any drug use was 22.9%, 17.1%, 15.3%, and 7.1% in the four
sample groups respectively. In all groups, cannabis was the drug most commonly used (range from 4.7% to 17.9%)
followed by cocaine (1.6% to 8.5%). The prevalence of use of drugs associated with chemsex was very low among
HIV-negative participants (1.0% heterosexual men, 0.2% women) and zero among HIV-positive men and women.
In age-adjusted analysis, factors linked to drug use overall and/or to cannabis and cocaine use specifically in the
four sample groups included Black/mixed Caribbean and white (vs. Black/mixed African) ethnicity, lower level
of education , cigarette smoking, and higher risk alcohol consumption. Associations of recreational drug use with
measures of condomless sex, depression, and anxiety were observed in the four groups, but were particularly
strong/apparent among women.
Conclusion: Providers need to be aware of cannabis and cocaine use and its potential link with sexual risk
behavior and symptoms of depression and anxiety among heterosexual men and women attending sexual health
and HIV clinics
Aerobic capacity, activity levels and daily energy expenditure in male and female adolescents of the kenyan nandi sub-group
The relative importance of genetic and socio-cultural influences contributing to the success of east Africans in endurance athletics remains unknown in part because the pre-training phenotype of this population remains incompletely assessed. Here cardiopulmonary fitness, physical activity levels, distance travelled to school and daily energy expenditure in 15 habitually active male (13.9±1.6 years) and 15 habitually active female (13.9±1.2) adolescents from a rural Nandi primary school are assessed. Aerobic capacity ([Formula: see text]) was evaluated during two maximal discontinuous incremental exercise tests; physical activity using accelerometry combined with a global positioning system; and energy expenditure using the doubly labelled water method. The [Formula: see text] of the male and female adolescents were 73.9±5.7 ml(.) kg(-1.) min(-1) and 61.5±6.3 ml(.) kg(-1.) min(-1), respectively. Total time spent in sedentary, light, moderate and vigorous physical activities per day was 406±63 min (50% of total monitored time), 244±56 min (30%), 75±18 min (9%) and 82±30 min (10%). Average total daily distance travelled to and from school was 7.5±3.0 km (0.8-13.4 km). Mean daily energy expenditure, activity-induced energy expenditure and physical activity level was 12.2±3.4 MJ(.) day(-1), 5.4±3.0 MJ(.) day(-1) and 2.2±0.6. 70.6% of the variation in [Formula: see text] was explained by sex (partial R(2) = 54.7%) and body mass index (partial R(2) = 15.9%). Energy expenditure and physical activity variables did not predict variation in [Formula: see text] once sex had been accounted for. The highly active and energy-demanding lifestyle of rural Kenyan adolescents may account for their exceptional aerobic fitness and collectively prime them for later training and athletic success
Measurement of the Atmospheric Muon Charge Ratio at TeV Energies with MINOS
The 5.4 kton MINOS far detector has been taking charge-separated cosmic ray
muon data since the beginning of August, 2003 at a depth of 2070
meters-water-equivalent in the Soudan Underground Laboratory, Minnesota, USA.
The data with both forward and reversed magnetic field running configurations
were combined to minimize systematic errors in the determination of the
underground muon charge ratio. When averaged, two independent analyses find the
charge ratio underground to be 1.374 +/- 0.004 (stat.) +0.012 -0.010(sys.).
Using the map of the Soudan rock overburden, the muon momenta as measured
underground were projected to the corresponding values at the surface in the
energy range 1-7 TeV. Within this range of energies at the surface, the MINOS
data are consistent with the charge ratio being energy independent at the two
standard deviation level. When the MINOS results are compared with measurements
at lower energies, a clear rise in the charge ratio in the energy range 0.3 --
1.0 TeV is apparent. A qualitative model shows that the rise is consistent with
an increasing contribution of kaon decays to the muon charge ratio.Comment: 16 pages, 17 figure
Measurement of neutrino velocity with the MINOS detectors and NuMI neutrino beam
The velocity of a ~3 GeV neutrino beam is measured by comparing detection times at the near and far detectors of the MINOS experiment, separated by 734 km. A total of 473 far detector neutrino events was used to measure (v-c)/c=5.12.910-5 (at 68% C.L.). By correlating the measured energies of 258 charged-current neutrino events to their arrival times at the far detector, a limit is imposed on the neutrino mass of mnu<50 MeV/c2 (99% C.L.)
A Study of Muon Neutrino Disappearance Using the Fermilab Main Injector Neutrino Beam
We report the results of a search for muon-neutrino disappearance by the Main
Injector Neutrino Oscillation Search. The experiment uses two detectors
separated by 734 km to observe a beam of neutrinos created by the Neutrinos at
the Main Injector facility at Fermi National Accelerator Laboratory. The data
were collected in the first 282 days of beam operations and correspond to an
exposure of 1.27e20 protons on target. Based on measurements in the Near
Detector, in the absence of neutrino oscillations we expected 336 +/- 14
muon-neutrino charged-current interactions at the Far Detector but observed
215. This deficit of events corresponds to a significance of 5.2 standard
deviations. The deficit is energy dependent and is consistent with two-flavor
neutrino oscillations according to delta m-squared = 2.74e-3 +0.44/-0.26e-3
eV^2 and sin^2(2 theta) > 0.87 at 68% confidence level.Comment: In submission to Phys. Rev.
Testing Lorentz Invariance and CPT Conservation with NuMI Neutrinos in the MINOS Near Detector
A search for a sidereal modulation in the MINOS near detector neutrino data
was performed. If present, this signature could be a consequence of Lorentz and
CPT violation as predicted by a class of extensions to the Standard Model. No
evidence for a sidereal signal in the data set was found, implying that there
is no significant change in neutrino propagation that depends on the direction
of the neutrino beam in a sun-centered inertial frame. Upper limits on the
magnitudes of the Lorentz and CPT violating terms in these extensions to the
Standard Model lie between 0.01-1% of the maximum expected, assuming a
suppression of these signatures by factor of .
No Evidence for a Trade-Off between Reproductive Investment and Immunity in a Rodent
Life history theory assumes there are trade-offs between competing functions such as reproduction and immunity. Although well studied in birds, studies of the trade-offs between reproduction and immunity in small mammals are scarce. Here we examined whether reduced immunity is a consequence of reproductive effort in lactating Brandt's voles (Lasiopodomys brandtii). Specifically, we tested the effects of lactation on immune function (Experiment I). The results showed that food intake and resting metabolic rate (RMR) were higher in lactating voles (6≤ litter size ≤8) than that in non-reproductive voles. Contrary to our expectation, lactating voles also had higher levels of serum total Immunoglobulin G (IgG) and anti-keyhole limpet hemocyanin (KLH) IgG and no change in phytohemagglutinin (PHA) response and anti-KLH Immunoglobulin M (IgM) compared with non-reproductive voles, suggesting improved rather than reduced immune function. To further test the effect of differences in reproductive investment on immunity, we compared the responses between natural large (n≥8) and small litter size (n≤6) (Experiment II) and manipulated large (11–13) and small litter size (2–3) (Experiment III). During peak lactation, acquired immunity (PHA response, anti-KLH IgG and anti-KLH IgM) was not significantly different between voles raising large or small litters in both experiments, despite the measured difference in reproductive investment (greater litter size, litter mass, RMR and food intake in the voles raising larger litters). Total IgG was higher in voles with natural large litter size than those with natural small litter size, but decreased in the enlarged litter size group compared with control and reduced group. Our results showed that immune function is not suppressed to compensate the high energy demands during lactation in Brandt's voles and contrasting the situation in birds, is unlikely to be an important aspect mediating the trade-off between reproduction and survival
B Physics at the Tevatron: Run II and Beyond
This report provides a comprehensive overview of the prospects for B physics
at the Tevatron. The work was carried out during a series of workshops starting
in September 1999. There were four working groups: 1) CP Violation, 2) Rare and
Semileptonic Decays, 3) Mixing and Lifetimes, 4) Production, Fragmentation and
Spectroscopy. The report also includes introductory chapters on theoretical and
experimental tools emphasizing aspects of B physics specific to hadron
colliders, as well as overviews of the CDF, D0, and BTeV detectors, and a
Summary.Comment: 583 pages. Further information on the workshops, including
transparencies, can be found at the workshop's homepage:
http://www-theory.lbl.gov/Brun2/. The report is also available in 2-up
http://www-theory.lbl.gov/Brun2/report/report2.ps.gz or chapter-by-chapter
http://www-theory.lbl.gov/Brun2/report
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