236 research outputs found
Possible Observation of Photon Speed Energy Dependence
Current constraints on photon velocity variability are summarized and
displayed in terms of an energy dependent vacuum refraction index. It is shown
that the energy-momentum balance of high energy Compton scattering is very
sensitive to the outgoing photon speed. A missing energy observation in HERA
Compton polarimeter data indicates that photons with 12.7 GeV energy are moving
faster than light by 5.1(1.4)mm/s. An asymmetry spectrum measured by the SLC
longitudinal polarimeter implies however an effect which is 42 times smaller,
although the interpretation of the data is less clear here.Comment: 13 pages, 3 figure
Comparison of QG-Induced Dispersion with Standard Physics Effects
One of the predictions of quantum gravity phenomenology is that, in
situations where Planck-scale physics and the notion of a quantum spacetime are
relevant, field propagation will be described by a modified set of laws.
Descriptions of the underlying mechanism differ from model to model, but a
general feature is that electromagnetic waves will have non-trivial dispersion
relations. A physical phenomenon that offers the possibility of experimentally
testing these ideas in the foreseeable future is the propagation of high-energy
gamma rays from GRB's at cosmological distances. With the observation of
non-standard dispersion relations within experimental reach, it is thus
important to find out whether there are competing effects that could either
mask or be mistaken for this one. In this letter, we consider possible effects
from standard physics, due to electromagnetic interactions, classical as well
as quantum, and coupling to classical geometry. Our results indicate that, for
currently observed gamma-ray energies and estimates of cosmological parameter
values, those effects are much smaller than the quantum gravity one if the
latter is first-order in the energy; some corrections are comparable in
magnitude with the second-order quantum gravity ones, but they have a very
different energy dependence.Comment: 8 pages; Version to be published in CQG as a letter; Includes some
new comments and references, but no changes in the result
Cytotoxicity of albebetin oligomers depends on cross-β-sheet formation
AbstractPrefibrillar cytotoxicity was suggested as a common amyloid characteristic. We showed two types of albebetin prefibrillar oligomers are formed during incubation at pH 7.3. Initial round-shaped oligomers consist of 10–15 molecules determined by atomic force microscopy, do not bind thioflavin-T and do not affect viability of granular neurons and SH-SY5Y cells. They are converted into ca. 30–40-mers possessing cross-β-sheet and reducing viability of neuronal cells. Neither monomers nor fibrils possess cytotoxicity. We suggest that oligomeric size is important for stabilising cross-β-sheet core critical for cytotoxicity. As albebetin was used as a carrier-protein for drug delivery, examination of amyloidogenicity is required prior polypeptide biomedical applications
An analysis of blood pressure screening of 21 112 participants in Armenia: May Measurement Month 2018.
Elevated blood pressure (BP) is a growing burden worldwide and is the leading cause of mortality and disability-adjusted life years all over the world. May Measurement Month (MMM) is a global initiative aimed to raise awareness of high BP and to act as a temporary solution to the lack of screening programmes worldwide. An opportunistic cross-sectional survey of volunteers aged ≥18 was carried out in May to July 2018. Blood pressure measurement, the definition of hypertension (HTN) and statistical analysis followed the standard MMM protocol. The study was conducted in public areas (17 sites in Yerevan and 22 in regions), both indoor and outdoor, as well as in 78 primary care centres. A total of 21 112 individuals were screened during MMM18, of which 20 732 had three BP measurements available. The mean age of screened individuals was 46.2 ± 17.3 years, 57.8% were female. At the time of screening, 26.1% were on antihypertensive medication. After imputation, the percentage of participants with HTN was 38.7%, and 76.7% of them were aware of their high BP. Of participants receiving treatment, 47.1% had a controlled BP. MMM18 was the largest BP screening campaign undertaken in Armenia. We found that the proportion of HTN is substantial in Armenia, which may be a vital contributor to the growing burden of non-communicable diseases. Our results also suggest that untreated HTN is common and when treated still not adequately controlled in Armenia. The current situation, with an insufficient control rate of HTN, must be changed as soon as possible
Beam-helicity asymmetries for single-hadron production in semi-inclusive deep-inelastic scattering from unpolarized hydrogen and deuterium targets
A measurement of beam-helicity asymmetries for single-hadron production in
deep-inelastic scattering is presented. Data from the scattering of 27.6 GeV
electrons and positrons off gaseous hydrogen and deuterium targets were
collected by the HERMES experiment. The asymmetries are presented separately as
a function of the Bjorken scaling variable, the hadron transverse momentum, and
the fractional energy for charged pions and kaons as well as for protons and
anti-protons. These asymmetries are also presented as a function of the three
aforementioned kinematic variables simultaneously
Transverse-target-spin asymmetry in exclusive -meson electroproduction
Hard exclusive electroproduction of mesons is studied with the
HERMES spectrometer at the DESY laboratory by scattering 27.6 GeV positron and
electron beams off a transversely polarized hydrogen target. The amplitudes of
five azimuthal modulations of the single-spin asymmetry of the cross section
with respect to the transverse proton polarization are measured. They are
determined in the entire kinematic region as well as for two bins in photon
virtuality and momentum transfer to the nucleon. Also, a separation of
asymmetry amplitudes into longitudinal and transverse components is done. These
results are compared to a phenomenological model that includes the pion pole
contribution. Within this model, the data favor a positive
transition form factor.Comment: DESY Report 15-14
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