4,554 research outputs found
Validation and determination of a reference interval for Canine HbA1c using an immunoturbidimetric assay
Background:
Hemoglobin A1c (HbA1c) provides a reliable measure of glycemic control over 2â3Â months in human diabetes mellitus. In dogs, presence of HbA1c has been demonstrated, but there are no validated commercial assays.
Objective:
The purpose of the study was to validate a commercially available automated immunoturbidimetric assay for canine HbA1c and determine an RI in a hospital population.
Methods:
The specificity of the assay was assessed by inducing glycosylation in vitro using isolated canine hemoglobin, repeatability by measuring canine samples 5 times in succession, long term inter-assay imprecision by measuring supplied control materials, stability using samples stored at 4°C over 5 days and â20°C over 8 weeks, linearity by mixing samples of known HbA1c in differing proportions, and the effect of anticoagulants with paired samples. An RI was determined using EDTA-anticoagulated blood samples from 60 nondiabetic hospitalized animals of various ages and breeds. Hemoglobin A1c was also measured in 10 diabetic dogs.
Results:
The concentration of HbA1c increased proportionally with glucose concentration in vitro. For repeat measurements, the CV was 4.08% (range 1.16â6.10%). Samples were stable for 5 days at 4°C. The assay was linear within the assessed range. Heparin- and EDTA-anticoagulated blood provided comparable results. The RI for HbA1c was 9â18.5 mmol/mol. There was no apparent effect of age or breed on HbA1c. In diabetic dogs, HbA1c ranged from 14 to 48 mmol/mol.
Conclusions:
The assay provides a reliable method for canine HbA1c measurement with good analytic performance
AMPTE/CCEâSCATHA simultaneous observations of substormâassociated magnetic fluctuations
This study examines substorm-associated magnetic field fluctuations observed by the AMPTE/CCE and SCATHA satellites in the near-Earth tail. Three tail reconfiguration events are selected, one event on August 28, 1986, and two consecutive events on August 30, 1986. The fractal analysis was applied to magnetic field measurements of each satellite. The result indicates that (1) the amplitude of the fluctuation of the north-south magnetic component is larger, though not overwhelmingly, than the amplitudes of the other two components and (2) the magnetic fluctuations do have a characteristic timescale, which is several times the proton gyroperiod. In the examined events the satellite separation was less than 10 times the proton gyroradius. Nevertheless, the comparison between the AMPTE/CCE and SCATHA observations indicates that (3) there was a noticeable time delay between the onsets of the magnetic fluctuations at the two satellite positions, which is too long to ascribe to the propagation of a fast magnetosonic wave, and (4) the coherence of the magnetic fluctuations was low in the August 28, 1986, event and the fluctuations had different characteristic timescales in the first event of August 30, 1986, whereas some similarities can be found for the second event of August 30, 1986. Result 1 indicates that perturbation electric currents associated with the magnetic fluctuations tend to flow parallel to the tail current sheet and are presumably related to the reduction of the tail current intensity. Results 2 and 3 suggest that the excitation of the magnetic fluctuations and therefore the trigger of the tail current disruption is a kinetic process in which ions play an important role. It is inferred from results 3 and 4 that the characteristic spatial scale of the associated instability is of the order of the proton gyroradius or even shorter, and therefore the tail current disruption is described as a system of chaotic filamentary electric currents. However, result 4 suggests that the nature of the tail current disruption can vary from event to event
Design of an electron microscope phase plate using a focused continuous-wave laser
We propose a Zernike phase contrast electron microscope that uses an intense
laser focus to convert a phase image into a visible image. We present the
relativistic quantum theory of the phase shift caused by the
laser-electron-interaction, study resonant cavities for enhancing the laser
intensity, and discuss applications in biology, soft materials science, and
atomic and molecular physics.Comment: 5 pages, 3 figure
Posteruptive phenomena in coronal mass ejections and substorms: Indicators of a universal process?
[1] We examine phenomena associated with eruptions in the two different regimes of the solar corona and the terrestrial magnetosphere. We find striking similarities between the speeds of shrinking magnetic field lines in the corona and dipolarization fronts traversing the magnetosphere. We also examine the similarities between supra-arcade downflows observed during solar flares and bursty bulk flows seen in the magnetotail and find that these phenomena have remarkably similar speeds, velocity profiles, and size scales. Thus we show manifest similarities in the magnetic reconfiguration in response to the ejection of coronal mass ejections in the corona and the ejection of plasmoids in the magnetotail. The subsequent return of loops to a quasi-potential state in the corona and field dipolarization in the magnetotail are physical analogs and trigger similar phenomena such as downflows, which provides key insights into the underlying drivers of the plasma dynamics
Simulations of inner magnetosphere dynamics with an expanded RAM-SCB model and comparisons with Van Allen Probes observations
Abstract Simulations from our newly expanded ring current-atmosphere interactions model with self-consistent magnetic field (RAM-SCB), now valid out to 9 R E, are compared for the first time with Van Allen Probes observations. The expanded model reproduces the storm time ring current buildup due to the increased convection and inflow of plasma from the magnetotail. It matches Magnetic Electron Ion Spectrometer (MagEIS) observations of the trapped high-energy (\u3e50 keV) ion flux; however, it underestimates the low-energy (\u3c10 keV) Helium, Oxygen, Proton, and Electron (HOPE) observations. The dispersed injections of ring current ions observed with the Energetic particle, Composition, and Thermal plasma (ECT) suite at high (\u3e20 keV) energy are better reproduced using a high-resolution convection model. In agreement with Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) observations, RAM-SCB indicates that the large-scale magnetic field is depressed as close as âŒ4.5 RE during even a moderate storm. Regions of electromagnetic ion cyclotron instability are predicted on the duskside from âŒ6 to âŒ9 RE, indicating that previous studies confined to geosynchronous orbit may have underestimated their scattering effect on the energetic particles. Key Points Expanded RAM-SCB model reproduces well high-energy (\u3e50 keV) MagEIS observations The magnetic field is depressed as close as âŒ4.5 RE during even a moderate storm EMIC wave growth extends on duskside from âŒ6 to âŒ9 RE during storm main phase
White matter changes and confrontation naming in retired aging national football league athletes
Using diffusion tensor imaging (DTI), we assessed the relationship of white matter integrity and performance on the Boston Naming Test (BNT) in a group of retired professional football players and a control group. We examined correlations between fractional anisotropy (FA) and mean diffusivity (MD) with BNT T-scores in an unbiased voxelwise analysis processed with tract-based spatial statistics (TBSS). We also analyzed the DTI data by grouping voxels together as white matter tracts and testing each tract's association with BNT T-scores. Significant voxelwise correlations between FA and BNT performance were only seen in the retired football players (pâ<â0.02). Two tracts had mean FA values that significantly correlated with BNT performance: forceps minor and forceps major. White matter integrity is important for distributed cognitive processes, and disruption correlates with diminished performance in athletes exposed to concussive and subconcussive brain injuries, but not in controls without such exposure
An electron Talbot interferometer
The Talbot effect, in which a wave imprinted with transverse periodicity
reconstructs itself at regular intervals, is a diffraction phenomenon that
occurs in many physical systems. Here we present the first observation of the
Talbot effect for electron de Broglie waves behind a nanofabricated
transmission grating. This was thought to be difficult because of Coulomb
interactions between electrons and nanostructure gratings, yet we were able to
map out the entire near-field interference pattern, the "Talbot carpet", behind
a grating. We did this using a Talbot interferometer, in which Talbot
interference fringes from one grating are moire'-filtered by a 2nd grating.
This arrangement has served for optical, X-ray, and atom interferometry, but
never before for electrons. Talbot interferometers are particularly sensitive
to distortions of the incident wavefronts, and to illustrate this we used our
Talbot interferometer to measure the wavefront curvature of a weakly focused
electron beam. Here we report how this wavefront curvature demagnified the
Talbot revivals, and we discuss applications for electron Talbot
interferometers.Comment: 5 pages, 5 figures, updated version with abstrac
Recursion Relations for One-Loop Gravity Amplitudes
We study the application of recursion relations to the calculation of finite
one-loop gravity amplitudes. It is shown explicitly that the known four, five,
and six graviton one-loop amplitudes for which the external legs have identical
outgoing helicities, and the four graviton amplitude with helicities (-,+,+,+)
can be derived from simple recursion relations. The latter amplitude is derived
by introducing a one-loop three-point vertex of gravitons of positive helicity,
which is the counterpart in gravity of the one-loop three-plus vertex in
Yang-Mills. We show that new issues arise for the five point amplitude with
helicities (-,+,+,+,+), where the application of known methods does not appear
to work, and we discuss possible resolutions.Comment: 28 pages, LaTeX, 12 figures. v2:typos and references correcte
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