870 research outputs found
Differential effects on inhibition of cholesterol absorption by plant stanol and plant sterol esters in apoE−/− mice
Aims
'Functional foods'; supplemented with plant sterol esters (PSE) and plant stanol esters (PSA) are therapeutic options for the management of hypercholesterolaemia. However, their effects on blood monocytes, endothelial function, atherogenesis, and sterol tissue concentrations are poorly understood.
Methods and results
Male apoE−/− mice (n= 30) were randomized to three different diets for 6 weeks (n= 10 per group): high-cholesterol (1.25%) western-type diet (WTD), WTD + 2% PSE, and WTD + 2% PSA. Both supplements reduced serum cholesterol. WTD + PSE resulted in increased plant sterol serum concentrations and increased inflammatory Ly-6C(high) monocyte numbers. WTD + PSA increased plant stanol serum concentrations and Ly-6C-monocyte numbers, but decreased vascular superoxide release, lipid hydroperoxides, and inflammatory cytokines in aortic tissue, in plasma, and in circulating monocytes. Despite reduced serum cholesterol concentrations, both supplements impaired endothelial vasodilation compared with WTD. WTD + PSA reduced the development of atherosclerotic lesions compared with WTD alone (12.7 ± 3.7 vs. 28.3 ± 3.5%), and WTD + PSE was less effective (17.5 ± 3.7%). WTD + PSE and WTD + PSA reduced the cholesterol content in the liver, but not in the brain. However, WTD + PSE and WTD + PSA increased plant sterol and plant stanol concentrations in the liver as well as in the brain.
Conclusion
PSE and PSA supplementation reduced serum cholesterol, but increased plant sterol and plant stanol concentrations. Elevated levels of PSE and PSA were associated with endothelial dysfunction and increased central nervous system depositions. Atherosclerotic lesion retardation was more pronounced in WTD + PSA, coinciding with higher regenerative monocyte numbers, decreased oxidative stress, and decreased inflammatory cytokines compared with WTD + PSE
Analytic formulas for frequency and size dependence of absorption and scattering efficiencies of astronomical polycyclic aromatic hydrocarbons
In a series of two recent papers, the frequency and size distribution
dependence of extinction spectra for astronomical silicate and graphite grains
was analyzed by us in the context of MRN type interstellar dust models. These
grains were taken to be homogeneous spheres following the power law
size distribution which is very much in use. The analytic formulas
were obtained for the graphite and silicate grains in wavelength range 1000\AA
- 22,500\AA and their utility was demonstrated. In this paper of the series, we
present analytic formulas for the scattering and absorption spectrum of another
important constituent of interstellar dust models, namely, the polycyclic
aromatic hydrocarbons (PAHs). Relative contribution of the PAHs to extinction
{\it vis a vis} carbonaceous classical grains has been examined.Comment: 19 pages, 4 figures, to appear in JQSRT 201
Evaluating the capabilities and uncertainties of droplet measurements for the fog droplet spectrometer (FM-100)
Droplet size spectra measurements are crucial to obtain a quantitative microphysical description of clouds and fog. However, cloud droplet size measurements are subject to various uncertainties. This work focuses on the error analysis of two key measurement uncertainties arising during cloud droplet size measurements with a conventional droplet size spectrometer (FM-100): first, we addressed the precision with which droplets can be sized with the FM-100 on the basis of the Mie theory. We deduced error assumptions and proposed a new method on how to correct measured size distributions for these errors by redistributing the measured droplet size distribution using a stochastic approach. Second, based on a literature study, we summarized corrections for particle losses during sampling with the FM-100. We applied both corrections to cloud droplet size spectra measured at the high alpine site Jungfraujoch for a temperature range from 0 °C to 11 °C. We showed that Mie scattering led to spikes in the droplet size distributions using the default sizing procedure, while the new stochastic approach reproduced the ambient size distribution adequately. A detailed analysis of the FM-100 sampling efficiency revealed that particle losses were typically below 10% for droplet diameters up to 10 μm. For larger droplets, particle losses can increase up to 90% for the largest droplets of 50 μm at ambient wind speeds below 4.4 m s<sup>−1</sup> and even to >90% for larger angles between the instrument orientation and the wind vector (sampling angle) at higher wind speeds. Comparisons of the FM-100 to other reference instruments revealed that the total liquid water content (LWC) measured by the FM-100 was more sensitive to particle losses than to re-sizing based on Mie scattering, while the total number concentration was only marginally influenced by particle losses. Consequently, for further LWC measurements with the FM-100 we strongly recommend to consider (1) the error arising due to Mie scattering, and (2) the particle losses, especially for larger droplets depending on the set-up and wind conditions
Effect of humidity on nitric acid uptake to mineral dust aerosol particles
International audienceThis study presents the first laboratory observation of HNO3 uptake by airborne mineral dust particles. The model aerosols were generated by dry dispersion of Arizona Test Dust (ATD), SiO2, and by nebulizing a saturated solution of calcium carbonate. The uptake of 13N-labeled gaseous nitric acid was observed in a flow reactor on the 0.2?2 s reaction time scale at room temperature and atmospheric pressure. The amount of nitric acid appearing in the aerosol phase at the end of the flow tube was found to be a linear function of the aerosol surface area. SiO2 particles did not show any significant uptake, while the CaCO3 aerosol was found to be more reactive than ATD. Due to the smaller uncertainty associated with the reactive surface area in the case of suspended particles as compared to bulk powder samples, we believe that we provide an improved estimate of the rate of uptake of HNO3 to mineral dust. The fact that the rate of uptake was smaller at a concentration of 1012 than at 1011 was indicative of a complex uptake mechanism. The uptake coefficient averaged over the first 2 s of reaction time at a concentration of 1012 molecules cm-3 was found to increase with increasing relative humidity, from 0.022±0.007 at 12% RH to 0.113±0.017 at 73% RH , which was attributed to an increasing degree of solvation of the more basic minerals. The extended processing of the dust by higher concentrations of HNO3 at 85% RH led to a water soluble coating on the particles and enhanced their hygroscopicity
Molecular Gas in Intermediate Redshift ULIRGs
We report on the results of observations in the CO(1-0) transition of a
complete sample of Southern, intermediate redshift (z = 0.2 - 0.5)
Ultra-Luminous Infra-Red Galaxies using the Mopra 22m telescope. The eleven
ULIRGs with L_FIR > 10^12.5 L_Sun south of Dec = -12 deg were observed with
integration times that varied between 5 and 24 hours. Four marginal detections
were obtained for individual targets in the sample. The "stacked" spectrum of
the entire sample yields a high significance, 10{\sigma} detection of the
CO(1-0) transition at an average redshift of z = 0.38. The tightest correlation
of L_FIR and L_CO for published low redshift ULIRG samples (z < 0.2) is
obtained after normalisation of both these measures to a fixed dust
temperature. With this normalisation the relationship is linear. The
distribution of dust-to-molecular hydrogen gas mass displays a systematic
increase in dust-to-gas mass with galaxy luminosity for low redshift samples
but this ratio declines dramatically for intermediate redshift ULIRGs down to
values comparable to that of the Small Magellanic Cloud. The upper envelope to
the distribution of ULIRG molecular mass as function of look-back time
demonstrates a dramatic rise by almost an order of magnitude from the current
epoch out to 5 Gyr. This increase in maximum ULIRG gas mass with look-back time
is even more rapid than that of the star formation rate density.Comment: 7 pages, 5 figures, accepted for publication by MNRA
Far-Ultraviolet Dust Albedo Measurements in the Upper Scorpius Cloud Using the SPINR Sounding Rocket Experiment
The Spectrograph for Photometric Imaging with Numeric Reconstruction (SPINR)
sounding rocket experiment was launched on 2000 August 4 to record
far-ultraviolet (912-1450 A) spectral and spatial information for the giant
reflection nebula in the Upper Scorpius region. The data were divided into
three arbitrary bandpasses (912-1029 A, 1030-1200 A, and 1235-1450 A) for which
stellar and nebular flux levels were derived. These flux measurements were used
to constrain a radiative transfer model and to determine the dust albedo for
the Upper Scorpius region. The resulting albedos were 0.28+/-0.07 for the
912-1029 A bandpass, 0.33+/-0.07 for the 1030-1200 A bandpass, and 0.77+/-0.13
for the 1235-1450 A bandpass
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