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To examine the use of vitamin D supplements during infancy among the participants in an international infant feeding trial.
Information about vitamin D supplementation was collected through a validated FFQ at the age of 2 weeks and monthly between the ages of 1 month and 6 months.
Infants (n 2159) with a biological family member affected by type 1 diabetes and with increased human leucocyte antigen-conferred susceptibility to type 1 diabetes from twelve European countries, the USA, Canada and Australia.
Daily use of vitamin D supplements was common during the first 6 months of life in Northern and Central Europe (>80 % of the infants), with somewhat lower rates observed in Southern Europe (>60 %). In Canada, vitamin D supplementation was more common among exclusively breast-fed than other infants (e.g. 71 % v. 44 % at 6 months of age). Less than 2 % of infants in the USA and Australia received any vitamin D supplementation. Higher gestational age, older maternal age and longer maternal education were study-wide associated with greater use of vitamin D supplements.
Most of the infants received vitamin D supplements during the first 6 months of life in the European countries, whereas in Canada only half and in the USA and Australia very few were given supplementation.
A reliable nondestructive method for measuring trace amounts of hydrogen in semiconductors and related materials has long been needed. Cold neutron capture prompt γ-ray activation analysis (CNPGAA) is a nondestructive, multielement technique which has found application in the measurement of trace amounts of hydrogen. The sample is irradiated by a beam of “cold” neutrons; the presence of hydrogen is confirmed by the detection of a 2223 keV gamma-ray. The technique gives bulk analyses (the neutron and gamma radiation penetrate the sample), the hydrogen peak is free of interferences, and the results are independent of the chemical form of hydrogen present. The instrument is capable of detecting less than 10 mg/kg of hydrogen in many matrices. We have used the technique to measure hydrogen levels in a dielectric film on a silicon wafer, semiconductor grade germanium, and quartz.
A combination of cold neutron prompt gamma-ray activation analysis (PGAA) and neutron incoherent scattering (NIS) has been used for nondestructive characterization of hydrogen as a function of position in slabs of wet concrete of different compositions. Hydrogen was determined by PGAA by scanning each sample across a 5 mm diameter neutron beam in 10 mm increments, and measuring the 2223 keV prompt gamma ray. NIS measurements were performed by scanning the sample across a 5 mm diameter neutron beam at 5 mm increments and detecting scattered neutrons. The measurements demonstrate the feasibility of the techniques for 2D compositional mapping of hydrogen and other elements in materials, and indicate the potential of these methods for monitoring the uniformity of drying concrete.
Mass fractions of hydrogen in titanium matrices have been measured using neutron incoherent scattering (NIS) and compared with results from prompt gamma activation analysis (PGAA). Qualitatively, NIS is a more efficient technique than PGAA which involves neutron absorption, and the former may be suitable for on-line analysis. However, for NIS the scattering contribution comes from both the hydrogen and the matrix, whereas prompt gamma emission has minimal matrix effect. To isolate the signal due to hydrogen scattering, a set of polypropylene films is used to simulate the increasing amount of hydrogen, and the scattered intensity is monitored. From this response, an unknown amount of the hydrogen can be deduced empirically. We have further attempted a first principle calculation of the intensity of the scattered signal from the experimental systems, and have obtained good agreement between calculation and the measurements. The study can be used as a reference for future applications of the scattering method to other hydrogen-in-metal systems.
Acetylcholine (ACh) in the vertebrate retina affects
the response properties of many ganglion cells, including
those that display directional selectivity. Three β
and eight α subunits of neuronal nicotinic acetylcholine
receptors (nAChRs) have been purified and antibodies have
been raised against many of them. Here we describe biochemical
and immunocytochemical studies of nAChRs in the rabbit retina.
Radioimmunoassay and Western blot analysis demonstrated that
many of the nAChRs recognized by a monoclonal antibody (mAb210)
contain β2 subunits, some of which are in combination with
α3 and possibly other subunits. MAb210-immunoreactive
cells in the inner nuclear layer (INL) were 7–14
μm in diameter and were restricted to the innermost
one or two tiers of cells, although occasional cells were
found in the middle of the INL. At least 60% of the cells
in the ganglion cell layer (GCL) in the visual streak displayed
mAb210 immunoreactivity; these neurons ranged from 7–18
μm in diameter. The dendrites of cells in both the
INL and GCL could sometimes be followed until they entered
one of two dense, poorly defined, bands of processes in
the inner plexiform layer (IPL) that overlap the arbors
of the cholinergic starburst cells. Parvalbumin and serotonin-positive
neurons did not exhibit nAChR immunoreactivity. Although
the level of receptor expression appeared to be low, mAb210
immunoreactivity was observed in some of the ChAT-positive
(starburst) amacrine cells.
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