2,067 research outputs found
Rigorous approach to the comparison between experiment and theory in Casimir force measurements
In most experiments on the Casimir force the comparison between measurement
data and theory was done using the concept of the root-mean-square deviation, a
procedure that has been criticized in literature. Here we propose a special
statistical analysis which should be performed separately for the experimental
data and for the results of the theoretical computations. In so doing, the
random, systematic, and total experimental errors are found as functions of
separation, taking into account the distribution laws for each error at 95%
confidence. Independently, all theoretical errors are combined to obtain the
total theoretical error at the same confidence. Finally, the confidence
interval for the differences between theoretical and experimental values is
obtained as a function of separation. This rigorous approach is applied to two
recent experiments on the Casimir effect.Comment: 10 pages, iopart.cls is used, to appear in J. Phys. A (special issue:
Proceedings of QFEXT05, Barcelona, Sept. 5-9, 2005
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The Stardust â a successful encounter with the remarkable comet Wild 2
On January 2, 2004 the Stardust spacecraft completed a close flyby of comet Wild2 (P81). Flying at a relative speed of 6.1 km/s within 237km of the 5 km nucleus, the spacecraft took 72 close-in images, measured the flux of impacting particles and did TOF mass spectrometry
The survivability of phyllosilicates and carbonates impacting Stardust Al foils: Facilitating the search for cometary water
Comet 81P/Wild 2 samples returned by NASA's Stardust mission provide an unequalled opportunity to study the contents of, and hence conditions and processes operating on, comets. They can potentially validate contentious interpretations of cometary infrared spectra and in situ mass spectrometry data: specifically the identification of phyllosilicates and carbonates. However, Wild 2 dust was collected via impact into capture media at ~6 km sâ1, leading to uncertainty as to whether these minerals were captured intact, and, if subjected to alteration, whether they remain recognizable. We simulated Stardust Al foil capture conditions using a twoâstage lightâgas gun, and directly compared transmission electron microscope analyses of preâ and postimpact samples to investigate survivability of lizardite and cronstedtite (phyllosilicates) and calcite (carbonate). We find the phyllosilicates do not survive impact as intact crystalline materials but as moderately to highly vesiculated amorphous residues lining resultant impact craters, whose bulk cation to Si ratios remain close to that of the impacting grain. Closer inspection reveals variation in these elements on a submicron scale, where impactâinduced melting accompanied by reducing conditions (due to the production of oxygen scavenging molten Al from the target foils) has resulted in the production of native silicon and Feâ and FeâSiârich phases. In contrast, large areas of crystalline calcite are preserved within the calcite residue, with smaller regions of vesiculated, Alâbearing calcic glass. Unambiguous identification of calcite impactors on Stardust Al foil is therefore possible, while phyllosilicate impactors may be inferred from vesiculated residues with appropriate bulk cation to Si ratios. Finally, we demonstrate that the characteristic textures and elemental distributions identifying phyllosilicates and carbonates by transmission electron microscopy can also be observed by stateâofâtheâart scanning electron microscopy providing rapid, nondestructive initial mineral identifications in Stardust residues
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Arabidopsis annexin1 mediates the radical-activated plasma membrane Ca2+ - and K+ -permeable conductance in root cells
Plant cell growth and stress signaling require Ca2+ influx through plasma membrane transport proteins that are regulated by
reactive oxygen species. In root cell growth, adaptation to salinity stress, and stomatal closure, such proteins operate
downstream of the plasma membrane NADPH oxidases that produce extracellular superoxide anion, a reactive oxygen
species that is readily converted to extracellular hydrogen peroxide and hydroxyl radicals, OH_. In root cells, extracellular OH_ activates a plasma membrane Ca2+-permeable conductance that permits Ca2+ influx. In Arabidopsis thaliana, distribution of
this conductance resembles that of annexin1 (ANN1). Annexins are membrane binding proteins that can form Ca2+-permeable
conductances in vitro. Here, the Arabidopsis loss-of-function mutant for annexin1 (Atann1) was found to lack the root hair and
epidermal OH_-activated Ca2+- and K+-permeable conductance. This manifests in both impaired root cell growth and ability to
elevate root cell cytosolic free Ca2+ in response to OH_. An OH_-activated Ca2+ conductance is reconstituted by recombinant
ANN1 in planar lipid bilayers. ANN1 therefore presents as a novel Ca2+-permeable transporter providing a molecular link
between reactive oxygen species and cytosolic Ca2+ in plants
Increased Glycemic Variability Is Independently Associated With Length of Stay and Mortality in Noncritically Ill Hospitalized Patients
OBJECTIVE To investigate the association between glycemic variability (GV) and both length of stay (LOS) and 90-day mortality in noncritically ill hospitalized patients.
RESEARCH DESIGN AND METHODS This study retrospectively analyzed 4,262 admissions to the general medicine or surgery services during a 2 year period. Patients with point-of-care glucose monitoring and a minimum of two glucose values per day on average were selected. GV was assessed by SD and coefficient of variation (CV). Data were analyzed with linear and logistic multivariate regression analysis in separate models for SD and CV. Analysis was performed with generalized estimating equations to adjust for correlation between multiple admissions in some individual cases.
RESULTS After exclusions, 935 admissions comprised the sample. Results of adjusted analysis indicate that for every 10 mg/dL increase in SD and 10ĂąâŹâpercentage point increase in CV, LOS increased by 4.4 and 9.7%, respectively. Relative risk of death in 90 days also increased by 8% for every 10-mg/dL increase in SD. These associations were independent of age, race, service of care (medicine or surgery), previous diagnosis of diabetes, HbA1c, BMI, the use of regular insulin as a sole regimen, mean glucose, and hypoglycemia occurrence during the hospitalization.
CONCLUSIONS Our results indicate that increased GV during hospitalization is independently associated with longer LOS and increased mortality in noncritically ill patients. Prospective studies with continuous glucose monitoring are necessary to investigate this association thoroughly and to generate therapeutic strategies targeted at decreasing GV.
Inpatient hyperglycemia is common, and it has been associated with increased morbidity and mortality in patients with and without diabetes (1ĂąâŹâ7). In the intensive care unit (ICU) setting, hypoglycemia has also been independently associated with a significant increase in mortality (8ĂąâŹâ10). Recently, a third metric of glucose control, known as glycemic variability (GV), has been proposed to be additionally implicated in the disease-associated process of dysglycemia (11).
GV refers to fluctuations of blood glucose values around the mean and has been posited as a novel marker for poor glycemic control (12,13). In vitro and human studies suggest that high GV leads to greater oxidative stress than does sustained hyperglycemia (14,15). Studies of ICU patients have consistently demonstrated that increased GV is independently associated with higher mortality (16ĂąâŹâ19). Notably, results from a large multicenter study concluded that GV was a stronger predictor of ICU mortality than was mean glucose concentrations (20).
Although there is no consensus as to the best method to determine GV in hospitalized patients, the use of SD of glucose values has been well validated by previous ICU studies (16,20). Coefficient of variation (CV) has also been suggested as a strong independent index for measuring GV because it corrects for mean glucose levels (21,22).
Despite substantial scientific evidence from the ICU, no previous studies have investigated the association between GV and clinical outcomes in patients admitted to the general medical and surgical wards. The purpose of this study was therefore to investigate the association between GV and length of stay (LOS) and 90-day mortality in noncritically ill hospitalized patients. We hypothesize that increased GV in this setting is associated with increased LOS and mortality
Antecedent anti-NMDA receptor encephalitis in two patients with multiple sclerosis
Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is an autoimmune disorder characterised by psychiatric symptoms, movement disorder and seizures often evolving into a severe encephalopathy. An overlap has recently been recognised between anti-NMDAR encephalitis and inflammatory demyelinating disorders, particularly neuromyelitis optical spectrum disorder (NMOSD). In this case report, we describe two patients with an initial presentation consistent with anti-NMDAR encephalitis who have subsequently developed relapsing-remitting multiple sclerosis (MS) and discuss the literature pertaining to potential overlap between NMDAR encephalitis and inflammatory demyelinating disorders
Casimir Effect as a Test for Thermal Corrections and Hypothetical Long-Range Interactions
We have performed a precise experimental determination of the Casimir
pressure between two gold-coated parallel plates by means of a micromachined
oscillator. In contrast to all previous experiments on the Casimir effect,
where a small relative error (varying from 1% to 15%) was achieved only at the
shortest separation, our smallest experimental error (%) is achieved
over a wide separation range from 170 nm to 300 nm at 95% confidence. We have
formulated a rigorous metrological procedure for the comparison of experiment
and theory without resorting to the previously used root-mean-square deviation,
which has been criticized in the literature. This enables us to discriminate
among different competing theories of the thermal Casimir force, and to resolve
a thermodynamic puzzle arising from the application of Lifshitz theory to real
metals. Our results lead to a more rigorous approach for obtaining constraints
on hypothetical long-range interactions predicted by extra-dimensional physics
and other extensions of the Standard Model. In particular, the constraints on
non-Newtonian gravity are strengthened by up to a factor of 20 in a wide
interaction range at 95% confidence.Comment: 17 pages, 7 figures, Sixth Alexander Friedmann International Seminar
on Gravitation and Cosmolog
Modelling polarization properties of comet 1P/Halley using a mixture of compact and aggregate particles
Recently, the result obtained from `Stardust' mission suggests that the
overall ratio of compact to aggregate particles is 65:35 (or 13:7) for Comet
81P/Wild 2 (Burchell et al. 2008). In the present work, we propose a model
which considers cometary dust as a mixture of compact and aggregate particles,
with composition of silicate and organic. We consider compact particles as
spheroidal particles and aggregates as BCCA and BAM2 aggregate with some size
distribution. For modeling Comet 1P/ Halley, the power-law size distribution
n(a)= a^{-2.6}, for both compact and aggregate particles is taken. We take a
mixture of BAM2 and BCCA aggregates with a lower and upper cutoff size around
0.20 and 1. We also take a mixture of prolate, spherical and
oblate compact particles with axial ratio (E) from 0.8 to 1.2 where a lower and
upper cutoff size around 0.1 and 10 are taken. Using T-matrix
code, the average simulated polarization curves are generated which can best
fit the observed polarization data at the four wavelengths =
0.365, 0.485, 0.670 and 0.684. The suitable mixing
percentage of aggregates emerging out from the present modeling corresponds to
50% BAM2 and 50% BCCA particles and silicate to organic mixing percentage
corresponds to 78% silicate and 22% organic in terms of volume. The present
model successfully reproduces the observed polarization data, especially the
negative branch, more effectively as compared to other work done in the past.
It is found that among the aggregates, the BAM2 aggregate plays a major role,
in deciding the cross-over angle and depth of negative polarization branch.Comment: 7 pages, 5 figures (accepted for publication in MNRAS on May 4, 2011
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Overview of the results of the organics PET Study of the cometary samples returned from comet Wild 2 by the Stardust mission
This presenation will provide an overview of the efforts and results produced by the Organics Preliminary Examination Team during their studies of the samples returned from comet Wild 2 by the Stardust spacecraft
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