129 research outputs found
Growing old, yet staying young: The role of telomeres in bats' exceptional longevity
Understanding aging is a grand challenge in biology. Exceptionally long-lived animals have mechanisms that underpin extreme longevity. Telomeres are protective nucleotide repeats on chromosome tips that shorten with cell division, potentially limiting life span. Bats are the longest-lived mammals for their size, but it is unknown whether their telomeres shorten. Using >60 years of cumulative mark-recapture field data, we show that telomeres shorten with age inRhinolophus ferrumequinumandMiniopterus schreibersii, but not in the bat genus with greatest longevity,Myotis. As in humans, telomerase is not expressed inMyotis myotisblood or fibroblasts. Selection tests on telomere maintenance genes show thatATMandSETX, which repair and prevent DNA damage, potentially mediate telomere dynamics inMyotisbats. Twenty-one telomere maintenance genes are differentially expressed inMyotis, of which 14 are enriched for DNA repair, and 5 for alternative telomere-lengthening mechanisms. We demonstrate how telomeres, telomerase, and DNA repair genes have contributed to the evolution of exceptional longevity inMyotisbats, advancing our understanding of healthy aging
Measurement of GEp/GMp in ep -> ep to Q2 = 5.6 GeV2
The ratio of the electric and magnetic form factors of the proton, GEp/GMp,
was measured at the Thomas Jefferson National Accelerator Facility (JLab) using
the recoil polarization technique. The ratio of the form factors is directly
proportional to the ratio of the transverse to longitudinal components of the
polarization of the recoil proton in the elastic
reaction. The new data presented in this article span the range 3.5 < Q2 < 5.6
GeV2 and are well described by a linear Q2 fit. Also, the ratio QF2p/F1p
reaches a constant value above Q2=2 GeV2.Comment: 6 pages, 4 figures Added two names to the main author lis
New Measurement of Parity Violation in Elastic Electron-Proton Scattering and Implications for Strange Form Factors
We have measured the parity-violating electroweak asymmetry in the elastic
scattering of polarized electrons from the proton. The result is A = -15.05 +-
0.98(stat) +- 0.56(syst) ppm at the kinematic point theta_lab = 12.3 degrees
and Q^2 = 0.477 (GeV/c)^2. The measurement implies that the value for the
strange form factor (G_E^s + 0.392 G_M^s) = 0.025 +- 0.020 +- 0.014, where the
first error is experimental and the second arises from the uncertainties in
electromagnetic form factors. This measurement is the first fixed-target parity
violation experiment that used either a `strained' GaAs photocathode to produce
highly polarized electrons or a Compton polarimeter to continuously monitor the
electron beam polarization.Comment: 8 pages, 4 figures, Tex, elsart.cls; revised version as accepted for
Phys. Lett.
Display of probability densities for data from a continuous distribution
Based on cumulative distribution functions, Fourier series expansion and
Kolmogorov tests, we present a simple method to display probability densities
for data drawn from a continuous distribution. It is often more efficient than
using histograms.Comment: 5 pages, 4 figures, presented at Computer Simulation Studies XXIV,
Athens, GA, 201
Communally breeding bats use physiological and behavioural adjustments to optimise daily energy expenditure
Small endotherms must change roosting and thermoregulatory behaviour in response to changes in ambient conditions if they are to achieve positive energy balance. In social species, for example many bats, energy expenditure is influenced by environmental conditions, such as ambient temperature, and also by social thermoregulation. Direct measurements of daily fluctuations in metabolic rates in response to ambient and behavioural variables in the field have not been technologically feasible until recently. During different reproductive periods, we investigated the relationships between ambient temperature, group size and energy expenditure in wild maternity colonies of Bechstein’s bats (Myotis bechsteinii). Bats used behavioural and physiological adjustments to regulate energy expenditure. Whether bats maintained normothermia or used torpor, the number of bats in the roosts as well changed with reproductive status and ambient temperature. During pregnancy and lactation, bats remained mostly normothermic and daily group sizes were relatively large, presumably to participate in the energetic benefits of social thermoregulation. In contrast, smaller groups were formed on days when bats used torpor, which occurred mostly during the post-lactation period. Thus, we were able to demonstrate on wild animals under natural conditions the significance of behavioural and physiological flexibility for optimal thermoregulatory behaviour in small endotherms
Tuning the GENIE Pion Production Model with MINERvA Data
Faced with unresolved tensions between neutrino interaction measurements at
few-GeV neutrino energies, current experiments are forced to accept large
systematic uncertainties to cover discrepancies between their data and model
predictions. In this paper, the widely used pion production model in GENIE is
compared to four MINERvA charged current pion production measurements using
NUISANCE. Tunings, ie, adjustments of model parameters, to help match GENIE to
MINERvA and older bubble chamber data are presented here. We find that
scattering off nuclear targets as measured in MINERvA is not in good agreement
with scattering off nucleon (hydrogen or deuterium) targets in the bubble
chamber data. An additional ad hoc correction for the low- region, where
collective effects are expected to be large, is also presented. While these
tunings and corrections improve the agreement of GENIE with the data, the
modeling is imperfect. The development of these tunings within the NUISANCE
frameworkallows for straightforward extensions to other neutrino event
generators and models, and allows omitting and including new data sets as they
become available
Polarization Transfer in the ^4He(\vec e,e'\vec p)^3H Reaction up to Q^2 = 2.6 (GeV/c)^2
We have measured the proton recoil polarization in the ^4He(\vec e,e'\vec
p)^3H reaction at Q^2 = 0.5, 1.0, 1.6, and 2.6 (GeV/c)^2. The measured ratio of
polarization transfer coefficients differs from a fully relativistic
calculation, favoring the inclusion of a predicted medium modification of the
proton form factors based on a quark-meson coupling model. In contrast, the
measured induced polarizations agree reasonably well with the fully
relativistic calculation indicating that the treatment of final-state
interactions is under control.Comment: 5 pages, 3 figures, uses revtex.sty, submitted to Physical Review
Letter
Beam-Target Double Spin Asymmetry A_LT in Charged Pion Production from Deep Inelastic Scattering on a Transversely Polarized He-3 Target at 1.4<Q^2<2.7 GeV^2
We report the first measurement of the double-spin asymmetry for
charged pion electroproduction in semi\nobreakdash-inclusive
deep\nobreakdash-inelastic electron scattering on a transversely polarized
He target. The kinematics focused on the valence quark region,
with . The corresponding neutron
asymmetries were extracted from the measured He asymmetries and
proton over He cross section ratios using the effective polarization
approximation. These new data probe the transverse momentum dependent parton
distribution function and therefore provide access to quark
spin-orbit correlations. Our results indicate a positive azimuthal asymmetry
for production on He and the neutron, while our
asymmetries are consistent with zero.Comment: 6 pages, 2 figures, 1 tables, published in PR
Single Spin Asymmetries in Charged Pion Production from Semi-Inclusive Deep Inelastic Scattering on a Transversely Polarized He Target
We report the first measurement of target single spin asymmetries in the
semi-inclusive reaction on a transversely polarized
target. The experiment, conducted at Jefferson Lab using a 5.9 GeV electron
beam, covers a range of 0.14 0.34 with 1.3 2.7 GeV. The
Collins and Sivers moments were extracted from the azimuthal angular dependence
of the measured asymmetries. The extracted Collins moments for He
are consistent with zero, except for the moment at , which
deviates from zero by 2.3. While the Sivers moments are
consistent with zero, the Sivers moments favor negative values. The
neutron results were extracted using the nucleon effective polarization and the
measured cross section ratio of proton to He, and are largely consistent
with the predictions of phenomenological fits and quark model calculations.Comment: 6 pages, 2 figures, 2 tables, published in PR
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