2,757 research outputs found
Pesticide effects on body temperature of torpid/hibernating rodents (Peromyscus leucopus and Spermophilus tridecemlineatus)
Environmental contaminants have been shown in the lab to alter thyroid hormone concentrations. Despite the role these hormones play in the physiological ecology of small mammals, no one has investigated the possible
effects of thyroid-disrupting chemicals on mammalian thermal ecology and thermoregulatory ability. Because the energetic impact of such a disruption is likely to be most dramatic during times already energetically stressful, we investigated the effects of two common pesticides (atrazine and lindane) on the use of daily torpor in white-footed mice, and the use of hibernation in 13-lined ground squirrels. Fortunately, we found that these strategies for over-wintering success were not impaired
Development of dispersion strengthened chromium alloys Summary report
Dispersion strengthened chromium alloys with minimal quantities of interstitial impuritie
Does a monetary incentive improve the response to a postal questionnaire in a randomised controlled trial? : the MINT incentive study
Background: Sending a monetary incentive with postal questionnaires has been found to improve
the proportion of responders, in research in non-healthcare settings. However, there is little
research on use of incentives to improve follow-up rates in clinical trials, and existing studies are
inconclusive. We conducted a randomised trial among participants in the Managing Injuries of the
Neck Trial (MINT) to investigate the effects on the proportion of questionnaires returned and
overall non-response of sending a £5 gift voucher with a follow-up questionnaire.
Methods: Participants in MINT were randomised to receive either: (a) a £5 gift voucher (incentive
group) or (b) no gift voucher (no incentive group), with their 4 month or 8 month follow-up
questionnaire. We recorded, for each group, the number of questionnaires returned, the number
returned without any chasing from the study office, the overall number of non-responders (after
all chasing efforts by the study office), and the costs of following up each group.
Results: 2144 participants were randomised, 1070 to the incentive group and 1074 to the no
incentive group. The proportion of questionnaires returned (RR 1.10 (95% CI 1.05, 1.16)) and the
proportion returned without chasing (RR 1.14 (95% CI 1.05, 1.24) were higher in the incentive
group, and the overall non-response rate was lower (RR 0.68 (95% CI 0.53, 0.87)). Adjustment for
injury severity and hospital of recruitment to MINT made no difference to these results, and there
were no differences in results between the 4-month and 8-month follow up questionnaires.
Analysis of costs suggested a cost of £67.29 per additional questionnaire returned.
Conclusion: Monetary incentives may be an effective way to increase the proportion of postal
questionnaires returned and minimise loss to follow-up in clinical trials
Evidence that hematopoietic stem cell function is preserved during aging in long-lived S6K1 mutant mice
The mechanistic target of rapamycin (mTOR) signalling pathway plays a highly conserved role in aging; mice lacking ribosomal protein S6 kinase 1 (S6K1-/-) have extended lifespan and healthspan relative to wild type (WT) controls. Exactly how reduced mTOR signalling induces such effects is unclear, although preservation of stem cell function may be important. We show, using gene expression analyses, that there was a reduction in expression of cell cycle genes in young (12 week) and aged (80 week) S6K1-/- BM-derived c-Kit+ cells when compared to age-matched WT mice, suggesting that these cells are more quiescent in S6K1-/- mice. In addition, we investigated hematopoietic stem cell (HSC) frequency and function in young and aged S6K1-/- and WT mice. Young, but not aged, S6K1-/- mice had more LSK (lineage-, c-Kit+, Sca-1+) cells (% of bone marrow (BM)), including the most primitive long-term repopulating HSC (LT-HSC) relative to WT controls. Donor-derived engraftment of LT-HSCs in recipient mice was unaffected by genotype in young mice, but was enhanced in transplants using LT-HSCs derived from aged S6K1-/- mice. Our results are the first to provide evidence that age-associated HSC functional decline is ameliorated in a long-lived mTOR mutant mouse
Multivariate Bernoulli and Euler polynomials via L\'evy processes
By a symbolic method, we introduce multivariate Bernoulli and Euler
polynomials as powers of polynomials whose coefficients involve multivariate
L\'evy processes. Many properties of these polynomials are stated
straightforwardly thanks to this representation, which could be easily
implemented in any symbolic manipulation system. A very simple relation between
these two families of multivariate polynomials is provided
A national survey of clinical practice for the management of whiplash-associated disorders in UK emergency departments
Objective: To undertake a national survey to determine current practice for the management of whiplash injuries in UK emergency departments (ED).
Methods: Postal questionnaire survey. 316 lead consultants from all UK ED with annual new attendances of over 50 000 people were asked to indicate the use of a range of treatments and the frequency with which these treatments were used. Samples of written advice were requested and content analysis was conducted and compared with survey responses.
Results: The response rate was 79% (251/316). The intervention most frequently used was verbal advice to exercise, reported by 84% of respondents for most or all cases, and advice against the use of a collar (83%). Other treatments reported as being used frequently were written advice and anti-inflammatory medication. 106 consultants (42%) provided a sample of written materials. Reference to expected recovery and encouragement for early return to activities were included in less than 6%. Nearly 50% of written materials contained information on how to use a soft collar and 61% contained information on solicitors and pursuing a personal injury claim. There were important differences between reported verbal behaviours and written advice.
Conclusion: Verbal advice is the primary method for managing whiplash injuries in ED and is usually supplemented by written advice. Within individual hospitals there is a lack of consistency between verbal and written advice. The promotion of personal injury claims is a common feature of written advice. Research is required to develop effective and consistent models of advice
Settling of cohesive sediment: particle-resolved simulations
We develop a physical and computational model for performing fully coupled,
particle-resolved Direct Numerical Simulations of cohesive sediment, based on
the Immersed Boundary Method. The model distributes the cohesive forces over a
thin shell surrounding each particle, thereby allowing for the spatial and
temporal resolution of the cohesive forces during particle-particle
interactions. The influence of the cohesive forces is captured by a single
dimensionless parameter in the form of a cohesion number, which represents the
ratio of cohesive and gravitational forces acting on a particle. We test and
validate the cohesive force model for binary particle interactions in the
Drafting-Kissing-Tumbling (DKT) configuration. The DKT simulations demonstrate
that cohesive particle pairs settle in a preferred orientation, with particles
of very different sizes preferentially aligning themselves in the vertical
direction, so that the smaller particle is drafted in the wake of the larger
one. To test this mechanism in a system of higher complexity, we perform large
simulations of 1,261 polydisperse settling particles starting from rest. These
simulations reproduce several earlier experimental observations by other
authors, such as the accelerated settling of sand and silt particles due to
particle bonding. The simulations demonstrate that cohesive forces accelerate
the overall settling process primarily because smaller grains attach to larger
ones and settle in their wakes. For the present cohesion number values, we
observe that settling can be accelerated by up to 29%. We propose physically
based parametrization of classical hindered settling functions proposed by
earlier authors, in order to account for cohesive forces. An investigation of
the energy budget shows that the work of the collision forces can substantially
modify the relevant energy conversion processes.Comment: 39 page
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