3,753 research outputs found
Detecting hydrogen-containing contaminants on metal surfaces
Spark emission spectroscopy analyzes surface contamination of metals. This technique controls the quality of surface preparations and is useful in fundamental investigations of surface properties of metals
Phase correlation of laser waves with arbitrary frequency spacing
The theoretically predicted correlation of laser phase fluctuations in
Lambda-type interaction schemes is experimentally demonstrated. We show, that
the mechanism of correlation in a Lambda scheme is restricted to high frequency
noise components, whereas in a double- scheme, due to the laser phase
locking in closed-loop interaction, it extends to all noise frequencies. In
this case the correlation is weakly sensitive to coherence losses. Thus the
double-Lambda scheme can be used to correlate e.m. fields with carrier
frequency differences beyond the GHz regime.Comment: 4 pages, 4 figure
The ^(54)Mn Clock and Its Implications for Cosmic Ray Propagation and Fe Isotope Studies
Radioactive ^(54)Mn suggested as a 'clock' for measuring the lifetime of heavy cosmic rays, has a poorly known ÎČ-decay half-life estimated to be in the range from ~10^5 to 10 ^7 yr. Some years ago Koch et al. concluded from measurements of the Mn/Fe ratio that a significant fraction of low-energy (<1 GeV/nucleon) ^(54)Mn produced by Fe fragmentation had decayed. Using a propagation code that includes improved fragmentation cross-sections, and recent data from HEAO 3 and a number of other spacecraft, we have reexamined the evidence for ^(54)Mn decay in cosmic rays. We conclude that present cosmic-ray data cannot establish the degree of ^(54)Mn decay, but point out that this question has important implications for studies of the ^(54)Fe abundance in cosmic-ray source material, as well as for cosmic-ray propagation studies
Attacking the Yield Plateau: Assessing the Nutrient Status of Kentucky Alfalfa Stands
Soil and tissue analyses indicated that alfalfa yields may be limited in some cases by soil fertility. Soil pH was below the optimal range in more than 40% of the fields sampled. This may result in decreased nitrogen fixation and nutrient availability. Potassium was reported low in approximately oneâquarter of the sampled stands according to tissue analysis. This was not unexpected since hay production removes large quantities of potash. Sulfur and magnesium were reported low in 13 and 23 percent of stands, respectively. More work is needed to better understand if these two 2023 Kentucky Alfalfa and Stored Forage Conference Proceedings Page Number 76 nutrients are truly limiting alfalfa yield in Kentucky
Association of the tumour necrosis factor alpha -308 but not the interleukin 10 -627 promoter polymorphism with genetic susceptibility to primary sclerosing cholangitis
BACKGROUND AND AIMS Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease of unknown aetiology. Abnormalities in immune regulation and genetic associations suggest that PSC is an immune mediated disease. Several polymorphisms within the tumour necrosis factor α (TNF-α) and interleukin 10 (IL-10) promoter genes have been described which influence expression of these cytokines. This study examines the possible association between polymorphisms at the â308 and â627 positions in the TNF-α and IL-10 promoter genes, respectively, and susceptibility to PSC.
METHODS TNF-α â308 genotypes were studied by polymerase chain reaction (PCR) in 160 PSC patients from Norway and the UK compared with 145 ethnically matched controls. IL-10 â627 genotypes were studied by PCR in 90 PSC patients compared with 84 ethnically matched controls.
RESULTS A total of 16% of Norwegian PSC patients and 12% of British PSC patients were homozygous for the TNF2 allele compared with 3% and 6% of respective controls. The TNF2 allele was present in 60% of PSC patients versus 30% of controls (ORcombined data=3.2 (95% confidence intervals (CI) 1.8â4.5); pcorr=10â5). The association between the TNF2 allele and susceptibility to PSC was independent of the presence of concurrent inflammatory bowel disease (IBD) in the PSC patients; 61% of PSC patients without IBD had TNF2 compared with 30% of controls (ORcombined data=3.2 (95% CI 1.2â9.0); pcorr=0.006 ). There was no difference in the â627 IL-10 polymorphism distributions between patients and controls in either population. The increase in TNF2 allele in PSC patients only occurs in the presence of DRB1*0301 (DR3) and B8. In the combined population data, DRB1*0301 showed a stronger association with susceptibility to PSC than both the TNF2 and B8 alleles (ORcombined data=3.8, pcorr=10â6 v ORcombined data=3.2, pcorr=10â5 vORcombined data =3.41, pcorr=10â4, respectively).
CONCLUSIONS This study identified a significant association between possession of the TNF2 allele, a GâA substitution at position â308 in the TNF-α promoter, and susceptibility to PSC. This association was secondary to the association of PSC with the A1-B8-DRB1*0301-DQA1*0501-DQB1*0201 haplotype. No association was found between the IL-10 â627 promoter polymorphism and PSC
Multifrequency Observations of the Virgo Blazars 3C 273 and 3C 279 in CGRO Cycle 8
We report first observational results of multifrequency campaigns on the
prominent Virgo blazars 3C 273 and 3C 279 which were carried out in January and
February 1999. Both blazars are detected from radio to gamma-ray energies. We
present the measured X- to gamma-ray spectra of both sources, and for 3C 279 we
compare the 1999 broad-band (radio to gamma-ray) spectrum to measured previous
ones.Comment: 5 pages including 3 figures, latex2e, to appear in: 'Proc. of the 5th
Compton Symposium', AIP, in pres
High Resolution Cherenkov Detectors for Use in a Cosmic Ray Isotope Spectrometer
We describe the development of new high-resolution Cerenkov detectors for use in an
instrument designed to measure the isotopic composition of cosmic ray nuclei from Be to
Ni (Z = 4 to 28). The latest version of this balloon-borne instrument contains two new
large-area, (-0.5 m^2) Cerenkov detectors, one composed of Teflon and a second of Pilot-
425. Through the use of improved light-collection techniques, and a novel radiator design,
the photoelectron yield of these counters has been upgraded significantly over that of
earlier counters. In particular, the greatly improved Cerenkov light yield achieved with
Teflon makes it an attractive alternative to available liquid counters of similar index of
refraction. Laboratory tests of these and other Cerenkov radiators are described, along
with estimates of the mass resolution that can be achieved
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