188 resultados para 379.8
Resumo:
Absolute and differential chemical abundances are presented for the largest group of massive stars in M31 studied to date. These results were derived from intermediate resolution spectra of seven B-type supergiants, lying within four OB associations covering a galactocentric distance of 5-12 kpc. The results are mainly based on an LTE analysis, and we additionally present a full non-LTE, unified model atmosphere analysis of one star (OB 78-277) to demonstrate the reliability of the differential LTE technique. A comparison of the stellar oxygen abundance with that of previous nebular results shows that there is an off set of between similar to0.15-0.4 dex between the two methods which is critically dependent on the empirical calibration adopted for the R 23 parameter with [O/H]. However within the typical errors of the stellar and nebular analyses (and given the strength of dependence of the nebular results on the calibration used) the oxygen abundances determined in each method are fairly consistent. We determine the radial oxygen abundance gradient from these stars, and do not detect any systematic gradient across this galactocentric range. We find that the inner regions of M31 are not, as previously thought, very "metal rich". Our abundances of C, N, O, Mg, Si, Al, S and Fe in the M31 supergiants are very similar to those of massive stars in the solar neighbourhood.
Resumo:
Modern intense ultrafast pulsed lasers generate an electric field of sufficient strength to permit tunnel ionization of the valence electrons in atoms(1). This process is usually treated as a rapid succession of isolated events, in which the states of the remaining electrons are neglected(2). Such electronic interactions are predicted to be weak, the exception being recollision excitation and ionization caused by linearly polarized radiation(3). In contrast, it has recently been suggested that intense field ionization may be accompanied by a two-stage 'shake-up' reaction(4). Here we report a unique combination of experimental techniques(5-8) that allows us to accurately measure the tunnel ionization probability for argon exposed to 50-fs laser pulses. Most significantly for the current study, this measurement is independent of the optical focal geometry(7,8), equivalent to a homogenous electric field. Furthermore, circularly polarized radiation negates recollision. The present measurements indicate that tunnel ionization results in simultaneous excitation of one or more remaining electrons through shake-up(9). From an atomic physics standpoint, it may be possible to induce ionization from specific states, and will influence the development of coherent attosecond extreme-ultraviolet-radiation sources(10). Such pulses have vital scientific and economic potential in areas such as high-resolution imaging of in vivo cells and nanoscale extreme-ultraviolet lithography.
Resumo:
BACKGROUND:
The protein components of GCF can be separated by reverse-phase microbore HPLC on a C18 column with detection on the basis of 214 nm absorbance. A single major symmetrical protein peak eluting with a retention time of 26 min (50% acetonitrile) was evident in gingival crevicular fluid (GCF) from periodontitis patients but not in healthy GCF. This protein was identified as human MRP-8 by N-terminal amino acid sequencing and liquid chromatography quadropole mass spectrometry.
AIMS:
To quantify the amount of MRP-8 detectable in GCF from individual healthy, gingivitis and periodontitis affected sites and to study the relationship, if any, between the levels of this responsive protein and periodontal health and disease.
METHODS:
GCF was sampled (30 s) from healthy, gingivitis, and periodontitis sites in peridontitis subjects (n=15) and from controls (n=5) with clinically healthy gingiva and no periodontitis. Purified MRP-8 was sequenced by Edmann degradation and the phenylthiohydantoin (PTH) amino acid yield determined (by comparison of peak area with external PTH amino acid standards). This value was subsequently used to calculate the relative amount of protein in the peak eluting with a retention time of 26.0 min (MRP-8) in individual GCF chromatograms.
RESULTS:
Higher levels of MRP-8 were detected in inflammatory sites: periodontitis 457.0 (281.0) ng; gingivitis 413.5 (394.5) ng compared with periodontally healthy sites in diseased subjects 14.6 (14.3) ng and in controls 18.6 (18.5) ng, p=0.003. There was at least 20-fold more MRP-8 in the inflammatory compared with the healthy sites studied.
CONCLUSIONS:
The preliminary data indicate that MRP-8 is present in GCF, with significantly greater amounts present at diseased than healthy sites. A systematic study of the relationship of this protein to periodontal disease could prove useful in further clarifying whether MRP-8 could be a reliable GCF biomarker of gingivitis and periodontitis.
Resumo:
Background
Little is known about the quality of life (QoL) of disabled children. We describe self-reported QoL of children with cerebral palsy, factors that influence it, and how it compares with QoL of the general population.
Methods
1174 children aged 8–12 years were randomly selected from eight population-based registers of children with cerebral palsy in six European countries and 743 (63%) agreed to participate; one further region recruited 75 children from multiple sources. Researchers visited these 818 children. 318 (39%) with severe intellectual impairment could not self-report; 500 (61%) reported their QoL using KIDSCREEN, an instrument with scores in ten domains, each with SD=10. Multivariable regression was used to relate QoL to impairments, pain, and sociodemographic characteristics. Comparisons were made with QoL data from the general population.
Findings
Impairments were not significantly associated with six KIDSCREEN domains. Comparison of least and most able groups showed that severely limited self-mobility was significantly associated with reduced mean score for physical wellbeing (7·6, 95% CI 2·7–12·4); intellectual impairment with reduced mean for moods and emotions (3·7, 1·5–5·9) and autonomy (3·3, 0·9–5·7); and speech difficulties with reduced mean for relationships with parents (4·5, 1·9–7·1). Pain was common and associated with lower QoL on all domains. Impairments and pain explained up to 3% and 7%, respectively, of variation in QoL. Children with cerebral palsy had similar QoL to children in the general population in all domains except schooling, in which evidence was equivocal, and physical wellbeing, in which comparison was not possible.
Interpretation
Parents can be reassured that most children aged 8–12 years with cerebral palsy will have similar QoL to other children. This finding should guide social and educational policy to ensure that disabled children participate fully in society. Because of its association with QoL, children's pain should be carefully assessed.
Resumo:
A new generation of water soluble tetrazolium salts have recently become available and in this study we compared a colorimetric assay developed using one of these salts, 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2, 4-disulfophenyl)-2H-tetrazolium, monosodium salt (WST-8), with a previously developed 2,3-bis[2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide(XTT) colorimetric assay to determine which agent is most suitable for use as a colorimetric indicator in susceptibility testing. The MICs of 6 antibiotics were determined for 33 staphylococci using both colorimetric assays and compared with those obtained using the British Society for Antimicrobial Chemotherapy reference broth microdilution method. Absolute categorical agreement between the reference and test methods ranged from 79% (cefuroxime) to 100% (vancomycin) for both assays. No minor or major errors occurred using either assay with very major errors ranging from zero (vancomycin) to seven (cefuroxime). Analysis of the distribution of differences in the 1092 dilution MIC results revealed overall agreement, within the accuracy limits of the standard test ( 1 1092 dilution), using the XTT and WST-8 assays of 98% and 88%, respectively. Further studies on 31 ESBL-producing isolates were performed using the XTT method with absolute categorical agreement ranging from 87% (nitrofurantoin) to 100% (ofloxacin and meropenem). No errors were noted for either ofloxacin or meropenem with overall agreement of 91%. The data suggests that XTT is more reliable and accurate than WST-8 for use in a rapid antimicrobial susceptibility test. (c) 2007 Elsevier B.V. All rights reserved.
