951 research outputs found
Small-X Quarks at HERA Predict the Ultra High Energy Neutrino-Nucleon Cross Section
New structure function data at small Bjorken from HERA are used along
with next-to-leading order QCD evolution to predict a cross section for
charged-current interactions of ultrahigh energy neutrinos with nucleons. This
new result is over twice the size of previous estimates and has important
implications for cosmic ray experiments now underway as well as for KM3 arrays
(cubic kilometer-scale neutrino telescopes) now in the planning stages.Comment: KITCS94-9-1, 9 pages (REVTeX) plus 3 postscript figures all uuencode
The GZK Bound and Strong Neutrino-Nucleon Interactions above 10^19eV: a Progress Report
Cosmic ray events above 10^19 eV have posed a fundamental problem for more
than thirty years. Recent measurements indicate that these events do not show
the features predicted by the GZK bound. The events may, in addition, display
angular correlations with point sources. If these observations are confirmed
for point sources further than 50 - 100 Mpc, then strong interactions for the
neutrino are indicated. Recent work on extra spatial dimensions provides a
context for massive spin-2 exchanges capable of generating cross sections in
the 1 - 100 mb range, as indicated by data. Applications of extra-dimension
physics are controversial, and we comment on several contentious issues.Comment: 4 pages, 1 figure; talk by JPR at 7th Conference on the Intersections
of Particle and Nuclear Physics, Quebec City, May, 200
Extra dimensions and Strong Neutrino-Nucleon interactions above eV : Breaking the GZK Barrier
Cosmic ray events above eV are on the verge of confronting
fundamental particle physics. The neutrino is the only candidate primary among
established particles capable of crossing 100 Mpc intergalactic distances
unimpeded. The magnitude of cross sections indicated by events, plus
consistency with the Standard Model at low-energy, point to new physics of
massive spin-2 exchange. In models based on extra dimensions, we find that the
cross section rises to typical hadronic values of between 1 and 100 mb
at energies above eV. Our calculations take into account constraints
of unitarity. We conclude that air-showers observed with energies above
eV are consistent with neutrino primaries and extra-dimension models.
An {\it upper bound} of 1-10 TeV on the mass scale at which graviton exchange
becomes strong in current Kaluza-Klein models follows.Comment: 14 pages, 2 figures, minor change
Signatures of Pseudoscalar Photon Mixing in CMB Radiation
We model the effect of photon and ultra-light pseudoscalar mixing on the
propagation of electromagnetic radiation through the extragalactic medium. The
medium is modelled as a large number of magnetic domains, uncorrelated with one
another. We obtain an analytic expression for the different Stokes parameters
in the limit of small mixing angle. The different Stokes parameters are found
to increase linearly with the number of domains. We also verify this result by
direct numerical simulations. We use this formalism to estimate the effect of
pseudoscalar-photon mixing on the Cosmic Microwave Background (CMB)
polarization. We impose limits on the model parameters by the CMB observations.
We find that the currently allowed parameter range admits a CMB circular
polarization up to order .Comment: 17 pages, 5 figure
Measurement of HbA1c in multicentre diabetes trials - should blood samples be tested locally or sent to a central laboratory: an agreement analysis (vol 17, pg 517, 2016)
Background
Glycated haemoglobin (HbA1c) is an important outcome measure in diabetes clinical trials. For multicentre designs, HbA1c can be measured locally at participating centres or by sending blood samples to a central laboratory. This study analyses the agreement between local and central measurements, using 1-year follow-up data collected in a multicentre randomised controlled trial (RCT) of newly diagnosed children with type I diabetes.
Methods
HbA1c measurements were routinely analysed both locally and centrally at baseline and then at 3, 6, 9 and 12 months and the data reported in mmol/mol. Agreement was assessed by calculating the bias and 95 % limits of agreement, using the Bland-Altman analysis method. A predetermined benchmark for clinically acceptable margin of error between measurements was subjectively set as ±10 % for HbA1c. The percentage of pairs of measurements that were classified as clinically acceptable was calculated. Descriptive statistics were used to examine the agreement within centres. Treatment group was not considered.
Results
Five hundred and ninety pairs of measurement, representing 255 children and 15 trial centres across four follow-up time points, were compared. There was no significant bias: local measurements were an average of 0.16 mmol/mol (SD = 4.5, 95 % CI −0.2 to 0.5) higher than central. The 95 % limits of agreement were −8.6 to 9.0 mmol/mol (local minus central). Eighty percent of local measurements were within ±10 % of corresponding central measurements. Some trial centres were more varied in the differences observed between local and central measurements: IQRs ranging from 3 to 9 mmol/mol; none indicated systematic bias.
Conclusions
Variation in agreement between HbA1c measurements was greater than had been expected although no overall bias was detected and standard deviations were similar. Discrepancies were present across all participating centres. These findings have implications for the comparison of standards of clinical care between centres, the design of future multicentre RCTs and existing quality assurance processes for HbA1c measurements. We recommend that centralised HbA1c measurement is preferable in the multicentre clinical trial setting
Final Report for Intravenous Fluid Generation (IVGEN) Spaceflight Experiment
NASA designed and operated the Intravenous Fluid Generation (IVGEN) experiment onboard the International Space Station (ISS), Increment 23/24, during May 2010. This hardware was a demonstration experiment to generate intravenous (IV) fluid from ISS Water Processing Assembly (WPA) potable water using a water purification technique and pharmaceutical mixing system. The IVGEN experiment utilizes a deionizing resin bed to remove contaminants from feedstock water to a purity level that meets the standards of the United States Pharmacopeia (USP), the governing body for pharmaceuticals in the United States. The water was then introduced into an IV bag where the fluid was mixed with USP-grade crystalline salt to produce USP normal saline (NS). Inline conductivity sensors quantified the feedstock water quality, output water purity, and NS mixing uniformity. Six 1.5-L bags of purified water were produced. Two of these bags were mixed with sodium chloride to make 0.9 percent NS solution. These two bags were returned to Earth to test for compliance with USP requirements. On-orbit results indicated that all of the experimental success criteria were met with the exception of the salt concentration. Problems with a large air bubble in the first bag of purified water resulted in a slightly concentrated saline solution of 117 percent of the target value of 0.9 g/L. The second bag had an inadequate amount of salt premeasured into the mixing bag resulting in a slightly deficient salt concentration of 93.8 percent of the target value. The USP permits a range from 95 to 105 percent of the target value. The testing plans for improvements for an operational system are also presented
Correlation of Ultra High Energy Cosmic Rays with Compact Radio Loud Quasars
Angular correlations of ultra-high energy cosmic rays with cosmologically
distant sources may provide clues to these mysterious events. We compare cosmic
ray tracks with energies above to a compilation of radio-loud
compact QSO positions. The statistical method emphasizes invariant quantities
and a test of {\it statistical independence} of track and source distributions.
Statistical independence is ruled out by several independent statistics at
confidence levels of less that (.), indicating that track
directions and QSO source positions are correlated at a highly significant
level.Comment: 12 pages, 2 figure
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