97 research outputs found
Integrated Image and X-Ray Microanalysis of Hepatic Lysosomes in a Patient with Idiopathic Hemosiderosis Before and After Treatment by Phlebotomy
Morphometrical and X-ray elemental information was extracted from Scanning Transmission Electron Microscopy (STEM) images of hepatic lysosomes of a patient with idiopathic hemosiderosis before and after treatment by phlebotomy. The elements of interest were (i) iron, stored in pathological quantities in hepatic lysosomal structures and (ii) cerium, used as a capture ion after a cytochemical reaction to detect acid phosphatase activity in the lysosomal structures.
Morphologically the lysosomal structures are heteromorph and the elements iron and cerium are heterogeneously distributed. With reduced raster (= reduced scanning area) analysis at 16 x 16 pixel points (integrating image and X-ray microanalysis), a marked difference in the area of the cross sectioned lysosomal structures before and after treatment could be demonstrated. Simultaneously the difference in the relative orientation of the elements iron and cerium before and after phlebotomy could be visualized.
Chelex ion exchange beads, loaded with 11.5% w/w iron, and coembedded with the tissue blocks, were used as an internal standard. A mean iron peak to background ratio was obtained and a factor, converting ratio to absolute iron concentration, was calculated. The same calculation procedure, now per pixel point, was followed for the hepatic lysosomal structures. A marked difference in iron concentration in the individual lysosomal structures was observed before and after treatment by phlebotomy
Image Analysis and X-Ray Microanalysis in Cytochemistry
When cytochemical reaction products are homogeneously distributed within an organelle, point analyses suffice for the quantitative approach. However, quantitative analysis becomes tedious, when the elements in the reaction product are inhomogeneously distributed. Problems arise when elements from two reaction products have to be related to each other, or to endogenous cytological products (ferritin, haemosiderin, calcium, electron dense markers), either topographically or in concentration. When analyzing inhomogeneous/heteromorphical reaction product-containing organelles special attention has to be paid to measure and relate both volume and concentration. In this paper a relative simple structure (eosinophil granules) is chosen to demonstrate that the acquisition of the requested morphometrical plus chemical information and their integration is possible. The following points will be covered to acquire the morphometrical and chemical information:
a). How to estimate the total cell cross-sectioned area. b). How to estimate the total cross-sectioned area of all reaction product-containing particles inside that cell. The ratio of these two areas will provide the requested information about the particle volume fraction. By using the X-ray detector in addition: c). How to acquire the chemical information at the requested resolution, within a reasonable total acquisition time d). How to integrate the morphometrical and chemical data per organelle, by matrix analysis in a reduced scan area. e). How to acquire quantitative chemical information, by the use of cross-sectioned standards. f). How to make this acquisition method independent from changes in the instrumental conditions during the acquisition
Gas Mass Fractions and the Evolution of LSB Dwarf Galaxies
The optical and HI properties for a sample of low surface brightness (LSB)
dwarf galaxies, cataloged from the Second Palomar Sky Survey, is presented. Gas
mass fractions for LSB dwarfs reach the highest levels of any know galaxy type
(f_g=95%) confirming that their low stellar densities are due to inefficient
conversion of gas mass into stellar mass. Comparison with star formation models
indicates that the blue optical colors of LSB dwarfs is not due to low
metallicity or recent star formation and can only be explained by a dominant
stellar population that is less than 5 Gyrs in mean age. If star formation
occurs in OB complexes, similar to normal galaxies, then LSB dwarfs must
undergo weak bursts traveling over the extent of the galaxy to maintain their
LSB nature, which contributes to their irregular morphological appearance.Comment: 23 pages AAS LaTeX, 7 figures, accepted for publication in A
Dissecting the luminosity function of the Coma cluster of galaxies using CFHT wide field images
[Abridged] We determined the luminosity function (LF) of the Coma cluster
galaxies selected by luminosity, and the LF bi-variate in central brightness.
The Coma cluster and control fields were imaged using the CFH12K (42x28 arcmin)
and UH8K (28x28 arcmin) wide-field cameras at the CFHT. Selected HST images
were used for testing. Quantities were derived from measurements in at least
two colors, which have the following features: (1) Galaxies as faint as three
times the luminosity of the brightest globular clusters are in the completeness
region of our data. (2) We have a complete census (in the explored region) of
low surface brightness galaxies with central surface brightness galaxies almost
as low as the faintest so far cataloged ones. (3) The explored area is among
the largest ever sampled with CCDs at comparable depth for any cluster of
galaxies. (4) The error budget includes all sources of errors known to date.
Using HST images we also discovered that blends of globular clusters, not
resolved in individual components due to seeing, look like dwarf galaxies when
observed from the ground and are numerous and bright. The derived Coma LF is
relatively steep (alpha=-1.4) over the 11 magnitudes sampled, but the slope and
shape depend on color. A large population of faint low surface brightness
galaxies was discovered, representing the largest contributor (in number) to
the LF at faint magnitudes. We found a clear progression for a faintening of
the LF from high surface brightness galaxies (mu~20 mag/arcsec2) to galaxies of
very faint central brightnesses (mu~24.5 mag/arcsec2), and some evidence for a
steepening. Compact galaxies, usually classified as stars and therefore not
included in the LF, are found to be a minor population in Coma.Comment: ApJ, in pres
Normal Globular Cluster Systems in Massive Low Surface Brightness Galaxies
We present the results of a study of the globular cluster systems of 6
massive spiral galaxies, originally cataloged as low surface brightness
galaxies but here shown to span a wide range of central surface brightness
values, including two intermediate to low surface brightness galaxies. We used
the Advanced Camera for Surveys on board HST to obtain photometry in the F475W
and F775W bands and select sources with photometric and morphological
properties consistent with those of globular clusters. A total of 206
candidates were identified in our target galaxies. From a direct comparison
with the Galactic globular cluster system we derive specific frequency values
for each galaxy that are in the expected range for late-type galaxies. We show
that the globular cluster candidates in all galaxies have properties consistent
with globular cluster systems of previously studied galaxies in terms of
luminosity, sizes and color. We establish the presence of globular clusters in
the two intermediate to low surface brightness galaxies in our sample and show
that their properties do not have any significant deviation from the behavior
observed in the other sample galaxies. Our results are broadly consistent with
a scenario in which low surface brightness galaxies follow roughly the same
evolutionary history as normal (i.e. high surface) brightness galaxies except
at a much lower rate, but require the presence of an initial period of star
formation intense enough to allow the formation of massive star clusters.Comment: 14 pages, 6 figures. AJ accepte
Flavor decomposition of the sea quark helicity distributions in the nucleon from semi-inclusive deep-inelastic scattering
Double-spin asymmetries of semi-inclusive cross sections for the production
of identified pions and kaons have been measured in deep-inelastic scattering
of polarized positrons on a polarized deuterium target. Five helicity
distributions including those for three sea quark flavors were extracted from
these data together with re-analyzed previous data for identified pions from a
hydrogen target. These distributions are consistent with zero for all three sea
flavors. A recently predicted flavor asymmetry in the polarization of the light
quark sea appears to be disfavored by the data.Comment: 5 pages, 3 figure
Transverse-target-spin asymmetry in exclusive -meson electroproduction
Hard exclusive electroproduction of mesons is studied with the
HERMES spectrometer at the DESY laboratory by scattering 27.6 GeV positron and
electron beams off a transversely polarized hydrogen target. The amplitudes of
five azimuthal modulations of the single-spin asymmetry of the cross section
with respect to the transverse proton polarization are measured. They are
determined in the entire kinematic region as well as for two bins in photon
virtuality and momentum transfer to the nucleon. Also, a separation of
asymmetry amplitudes into longitudinal and transverse components is done. These
results are compared to a phenomenological model that includes the pion pole
contribution. Within this model, the data favor a positive
transition form factor.Comment: DESY Report 15-14
Nuclear Polarization of Molecular Hydrogen Recombined on a Non-metallic Surface
The nuclear polarization of molecules formed by recombination
of nuclear polarized H atoms on the surface of a storage cell initially coated
with a silicon-based polymer has been measured by using the longitudinal
double-spin asymmetry in deep-inelastic positron-proton scattering. The
molecules are found to have a substantial nuclear polarization, which is
evidence that initially polarized atoms retain their nuclear polarization when
absorbed on this type of surfac
First Measurement of the Tensor Structure Function of the Deuteron
The \Hermes experiment has investigated the tensor spin structure of the
deuteron using the 27.6 GeV/c positron beam of \Hera. The use of a tensor
polarized deuteron gas target with only a negligible residual vector
polarization enabled the first measurement of the tensor asymmetry \At and
the tensor structure function \bd for average values of the Bj{\o}rken
variable and of the squared four-momentum transfer . The quantities \At and \bd are found to be
non-zero. The rise of \bd for decreasing values of can be interpreted to
originate from the same mechanism that leads to nuclear shadowing in
unpolarized scattering
Single-spin asymmetries in semi-inclusive deep-inelastic scattering on a transversely polarized hydrogen target
Single-spin asymmetries for semi-inclusive electroproduction of charged pions
in deep-inelastic scattering of positrons are measured for the first time with
transverse target polarization. The asymmetry depends on the azimuthal angles
of both the pion () and the target spin axis () about the virtual
photon direction and relative to the lepton scattering plane. The extracted
Fourier component \cmpi is a signal of the previously unmeasured quark
transversity distribution, in conjunction with the so-called Collins
fragmentation function, also unknown. The Fourier component \smpi of the
asymmetry arises from a correlation between the transverse polarization of the
target nucleon and the intrinsic transverse momentum of quarks, as represented
by the previously unmeasured Sivers distribution function. Evidence for both
signals is observed, but the Sivers asymmetry may be affected by exclusive
vector meson productio
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