3,355 research outputs found
Hyperhomocysteinemia decreases bone blood flow
Elevated plasma levels of homocysteine (Hcy), known as hyperhomocysteinemia (HHcy), are associated with osteoporosis. A decrease in bone blood flow is a potential cause of compromised bone mechanical properties. Therefore, we hypothesized that HHcy decreases bone blood flow and biomechanical properties. To test this hypothesis, male Sprague–Dawley rats were treated with Hcy (0.67 g/L) in drinking water for 8 weeks. Age-matched rats served as controls. At the end of the treatment period, the rats were anesthetized. Blood samples were collected from experimental or control rats. Biochemical turnover markers (body weight, Hcy, vitamin B12, and folate) were measured. Systolic blood pressure was measured from the right carotid artery. Tibia blood flow was measured by laser Doppler flow probe. The results indicated that Hcy levels were significantly higher in the Hcy-treated group than in control rats, whereas vitamin B12 levels were lower in the Hcy-treated group compared with control rats. There was no significant difference in folate concentration and blood pressure in Hcy-treated versus control rats. The tibial blood flow index of the control group was significantly higher (0.78 ± 0.09 flow unit) compared with the Hcy-treated group (0.51 ± 0.09). The tibial mass was 1.1 ± 0.1 g in the control group and 0.9 ± 0.1 in the Hcy-treated group. The tibia bone density was unchanged in Hcy-treated rats. These results suggest that Hcy causes a reduction in bone blood flow, which contributes to compromised bone biomechanical properties
A novel method for the absolute fluorescence yield measurement by AIRFLY
One of the goals of the AIRFLY (AIR FLuorescence Yield) experiment is to
measure the absolute fluorescence yield induced by electrons in air to better
than 10% precision. We introduce a new technique for measurement of the
absolute fluorescence yield of the 337 nm line that has the advantage of
reducing the systematic uncertainty due to the detector calibration. The
principle is to compare the measured fluorescence yield to a well known process
- the Cerenkov emission. Preliminary measurements taken in the BFT (Beam Test
Facility) in Frascati, Italy with 350 MeV electrons are presented. Beam tests
in the Argonne Wakefield Accelerator at the Argonne National Laboratory, USA
with 14 MeV electrons have also shown that this technique can be applied at
lower energies.Comment: presented at the 5th Fluorescence Workshop, El Escorial - Madrid,
Spain, 16 - 20 September 200
Temperature and Humidity Dependence of Air Fluorescence Yield measured by AIRFLY
The fluorescence detection of ultra high energy cosmic rays requires a
detailed knowledge of the fluorescence light emission from nitrogen molecules
over a wide range of atmospheric parameters, corresponding to altitudes typical
of the cosmic ray shower development in the atmosphere. We have studied the
temperature and humidity dependence of the fluorescence light spectrum excited
by MeV electrons in air. Results for the 313.6 nm, 337.1 nm, 353.7 nm and 391.4
nm bands are reported in this paper. We found that the temperature and humidity
dependence of the quenching process changes the fluorescence yield by a
sizeable amount (up to 20%) and its effect must be included for a precise
estimation of the energy of ultra high energy cosmic rays.Comment: presented at the 5th Fluorescence Workshop, El Escorial - Madrid,
Spain, 16 - 20 September 2007, to appear in Nuclear Instruments and Methods
LHC Optics Measurement with Proton Tracks Detected by the Roman Pots of the TOTEM Experiment
Precise knowledge of the beam optics at the LHC is crucial to fulfil the
physics goals of the TOTEM experiment, where the kinematics of the scattered
protons is reconstructed with the near-beam telescopes -- so-called Roman Pots
(RP). Before being detected, the protons' trajectories are influenced by the
magnetic fields of the accelerator lattice. Thus precise understanding of the
proton transport is of key importance for the experiment. A novel method of
optics evaluation is proposed which exploits kinematical distributions of
elastically scattered protons observed in the RPs. Theoretical predictions, as
well as Monte Carlo studies, show that the residual uncertainty of this optics
estimation method is smaller than 0.25 percent.Comment: 20 pages, 11 figures, 5 figures, to be submitted to New J. Phy
Double diffractive cross-section measurement in the forward region at LHC
The first double diffractive cross-section measurement in the very forward
region has been carried out by the TOTEM experiment at the LHC with
center-of-mass energy of sqrt(s)=7 TeV. By utilizing the very forward TOTEM
tracking detectors T1 and T2, which extend up to |eta|=6.5, a clean sample of
double diffractive pp events was extracted. From these events, we measured the
cross-section sigma_DD =(116 +- 25) mub for events where both diffractive
systems have 4.7 <|eta|_min < 6.5 .Comment: 5 pages, 1 figure, submitted for publicatio
Diamond Detectors for the TOTEM Timing Upgrade
This paper describes the design and the performance of the timing detector
developed by the TOTEM Collaboration for the Roman Pots (RPs) to measure the
Time-Of-Flight (TOF) of the protons produced in central diffractive
interactions at the LHC. The measurement of the TOF of the protons allows the
determination of the longitudinal position of the proton interaction vertex and
its association with one of the vertices reconstructed by the CMS detectors.
The TOF detector is based on single crystal Chemical Vapor Deposition (scCVD)
diamond plates and is designed to measure the protons TOF with about 50 ps time
precision. This upgrade to the TOTEM apparatus will be used in the LHC run 2
and will tag the central diffractive events up to an interaction pileup of
about 1. A dedicated fast and low noise electronics for the signal
amplification has been developed. The digitization of the diamond signal is
performed by sampling the waveform. After introducing the physics studies that
will most profit from the addition of these new detectors, we discuss in detail
the optimization and the performance of the first TOF detector installed in the
LHC in November 2015.Comment: 26 pages, 18 figures, 2 tables, submitted for publication to JINS
Evidence for non-exponential elastic proton-proton differential cross-section at low |t| and sqrt(s) = 8 TeV by TOTEM
The TOTEM experiment has made a precise measurement of the elastic
proton-proton differential cross-section at the centre-of-mass energy sqrt(s) =
8 TeV based on a high-statistics data sample obtained with the beta* = 90
optics. Both the statistical and systematic uncertainties remain below 1%,
except for the t-independent contribution from the overall normalisation. This
unprecedented precision allows to exclude a purely exponential differential
cross-section in the range of four-momentum transfer squared 0.027 < |t| < 0.2
GeV^2 with a significance greater than 7 sigma. Two extended parametrisations,
with quadratic and cubic polynomials in the exponent, are shown to be well
compatible with the data. Using them for the differential cross-section
extrapolation to t = 0, and further applying the optical theorem, yields total
cross-section estimates of (101.5 +- 2.1) mb and (101.9 +- 2.1) mb,
respectively, in agreement with previous TOTEM measurements.Comment: Final version published in Nuclear Physics
First Results from the TOTEM Experiment
The first physics results from the TOTEM experiment are here reported,
concerning the measurements of the total, differential elastic, elastic and
inelastic pp cross-section at the LHC energy of = 7 TeV, obtained
using the luminosity measurement from CMS. A preliminary measurement of the
forward charged particle distribution is also shown.Comment: Conference Proceeding. MPI@LHC 2010: 2nd International Workshop on
Multiple Partonic Interactions at the LHC. Glasgow (UK), 29th of November to
the 3rd of December 201
Performance of the TOTEM Detectors at the LHC
The TOTEM Experiment is designed to measure the total proton-proton
cross-section with the luminosity-independent method and to study elastic and
diffractive pp scattering at the LHC. To achieve optimum forward coverage for
charged particles emitted by the pp collisions in the interaction point IP5,
two tracking telescopes, T1 and T2, are installed on each side of the IP in the
pseudorapidity region 3.1 < = |eta | < = 6.5, and special movable beam-pipe
insertions - called Roman Pots (RP) - are placed at distances of +- 147 m and
+- 220 m from IP5. This article describes in detail the working of the TOTEM
detector to produce physics results in the first three years of operation and
data taking at the LHC.Comment: 40 pages, 31 figures, submitted to Int. J. Mod. Phys.
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