Striking Photospheric Abundance Anomalies in Blue Horizontal-Branch Stars in Globular Cluster M13

High-resolution optical spectra of thirteen blue horizontal-branch (BHB) stars in the globular cluster M13 show enormous deviations in element abundances from the expected cluster metallicity. In the hotter stars (T_eff > 12000 K), helium is depleted by factors of 10 to 100 below solar, while iron is enhanced to three times the solar abundance, two orders of magnitude above the canonical metallicity [Fe/H] ~= -1.5 dex for this globular cluster. Nitrogen, phosphorus, and chromium exhibit even more pronounced enhancements, and other metals are also mildly overabundant, with the exception of magnesium, which stays very near the expected cluster metallicity. These photospheric anomalies are most likely due to diffusion --- gravitational settling of helium, and radiative levitation of the other elements --- in the stable radiative atmospheres of these hot stars. The effects of these mechanisms may have some impact on the photometric morphology of the cluster's horizontal branch and on estimates of its age and distance.Comment: 11 pages, 1 Postscript figure, uses aaspp4.sty, accepted for publication in ApJ Letter

Rotations and Abundances of Blue Horizontal-Branch Stars in Globular Cluster M15

High-resolution optical spectra of eighteen blue horizontal-branch (BHB) stars in the globular cluster M15 indicate that their stellar rotation rates and photospheric compositions vary strongly as a function of effective temperature. Among the cooler stars in the sample, at Teff ~ 8500 K, metal abundances are in rough agreement with the canonical cluster metallicity, and the v sin i rotations appear to have a bimodal distribution, with eight stars at v sin i < 15 km/s and two stars at v sin i ~ 35 km/s. Most of the stars at Teff > 10000 K, however, are slowly rotating, v sin i < 7 km/s, and their iron and titanium are enhanced by a factor of 300 to solar abundance levels. Magnesium maintains a nearly constant abundance over the entire range of Teff, and helium is depleted by factors of 10 to 30 in three of the hotter stars. Diffusion effects in the stellar atmospheres are the most likely explanation for these large differences in composition. Our results are qualitatively very similar to those previously reported for M13 and NGC 6752, but with even larger enhancement amplitudes, presumably due to the increased efficiency of radiative levitation at lower intrinsic [Fe/H]. We also see evidence for faster stellar rotation explicitly preventing the onset of the diffusion mechanisms among a subset of the hotter stars.Comment: 11 pages, 1 figure, 1 table, accepted to ApJ

Counts and Colors of Faint Galaxies in the U and R Bands

Ground-based counts and colors of faint galaxies in the U and R bands in one field at high Galactic latitude are presented. Integrated over flux, a total of 1.2x10^5 sources per square degree are found to U=25.5 mag and 6.3x10^5 sources per square degree to R=27 mag, with d log N/dm ~ 0.5 in the U band and d log N/dm ~ 0.3 in the R band. Consistent with these number-magnitude curves, sources become bluer with increasing magnitude to median U-R=0.6 mag at 24<U<25 mag and U-R=1.2 mag at 25 < R < 26 mag. Because the Lyman break redshifts into the U band at z~3, at least 1.2x10^5 sources per square degree must be at redshifts z<3. Measurable U-band fluxes of 73 percent of the 6.3x10^5 sources per square degree suggest that the majority of these also lie at z < 3. These results require an enormous space density of objects in any cosmological model.Comment: 17 pages, MNRAS in pres

Protein kinase activity is associated with CD63 in melanoma cells

BACKGROUND: The tetraspan protein CD63, originally described as a stage-specific melanoma antigen but also present in a number of normal cells, regulates melanoma cell growth in nude mice, motility in serum containing media, and adhesion to several extracellular matrix proteins. CD63 has been reported to associate with β1 and β2 integrins, but the mechanism of signal transduction by CD63 is not clear. This study examined whether CD63 is associated with protein kinase and can transmit signals in melanoma cells. METHODS: Immunoprecipitation and radiolabeling were used to test for association of protein kinase activity with CD63. Adhesion of cells to monoclonal antibodies immobilized to microtiter plates was used to examine the ability of CD63 to transmit signals. RESULTS: CD63 was capable of transmitting a signal in melanoma cells that required extracellular calcium. In the absence of extracellular calcium at the time of binding to the CD63 mAb, the cell was no longer responsive to stimulation by CD63. Immunoprecipitation studies demonstrated protein kinase activity associated with CD63, and phosphoamino acid analysis revealed that most of this protein kinase activity was due to serine kinase activity. CONCLUSION: The current study suggests that serine protein kinase activity associated with CD63 may play a role in signaling by CD63 in melanoma cells

Creating an Online Community of Practice: The Deaf and Hard of Hearing Virtual Academic Community

This presentation describes the activities of the Deaf STEM Community Alliance project using the social media platform Google+ private community. The private community provides socialization opportunities and shares accessible STEM media with community participants. A pilot study was conducted on a segment of the community’s activity. Posting frequency was analyzed for the highest impact day, posting times, and types of posts that received the most activity. Tuesdays were the most active, and the best times to post were during the afternoon hours. Posts having content related to community members received the most responses. These findings were compared to research on posting frequency in open social media platforms. Future research should investigate in greater detail the uses of social media for education and for other groups with disabilities

Human Keratinocytes Adhere to Two Distinct Heparin-Binding Synthetic Peptides Derived from Fibronectin

Fibronectin is present at the dermal-epidermal junction in normal skin and is increased in skin tissues in inflammatory diseases, skin cancers and wound repair. The present studies focused on further characterizing the interaction between fibronectin and keratinocytes, specifically addressing whether human keratinocytes utilize multiple adhesion promoting sequences within fibronectin. Initially, direct cell-binding assays were utilized in which keratinocyte adhesion to plastic substrata coated with fibronectin or proteolytic fragments of fibronectin was quantified. Intact fibronectin, a 75-kD proteolytic fragment containing the RGD sequence, and 33/66-kD cell adhesion/heparin binding fragments lacking the RGD sequence derived from the A and B chains of fibronectin, all promoted keratinocyte adhesion in a concentration-dependent manner. To further define putative cell-binding domains within the 33/66kD fibronectin fragments, we studied three chemically synthesized peptides derived from the amino acid sequence of the 33-kD fragment of the fibronectin A chain: FN-C/H-I (YEKPGSPPREVVPRPRPGV), FN-C/H-II (KNNQKSEPLIGRKKT) and CS1 (DELPQLVTLPHPNLHGPEILDVPST). Substrata coated with either FN-C/H-I or FN-C/H-II promoted keratinocyte adhesion in a concentration-dependent and saturable manner, whereas peptide CS1 promoted no significant keratinocyte adhesion. In solution, both exogenous FN-C/H-I and FN-C/H-II partially inhibited keratinocyte adhesion to the 33/66-kD fibronectin fragments. Furthermore, antibodies prepared against these peptides also inhibited keratinocyte adhesion to the 33/66-kD fibronectin fragments. These data indicate that keratinocyte adhesion to fibronectin is mediated by multiple distinct amino acid sequences, at least two of which are localized to the carboxy-terminal heparin binding domain of fibronectin

Human immune responses to infective stage larval-specific chitinase of filarial parasite, Onchocerca volvulus, Ov-CHI-1.

BACKGROUND: Ov-CHI-1 is a chitinase specifically expressed in the infective stage larvae of the human filarial parasite Onchocerca volvulus. Evidence has show that it could be a vaccine candidate, however, there is no data available regarding the immunological status of people naturally exposed to infective stage larvae and thus provoked by this antigen. METHOD: We analysed the Ov-CHI-1-specific immune response present in four endemic foci of human onchocerciasis (Ecuador, Nigeria, Togo and Cameroon) by enzyme-linked immunosorbent assays and T-cell proliferation assays. RESULTS: In these foci of infection, antibodies to Ov-CHI-1 were found to be present in only 22% of individuals from Ecuador, but were detected in 42–62% of infected individuals in the three foci from West Africa (Nigeria, Togo and Cameroon). There was found to be no relationship between antibody level and age, gender, or infection intensity as indicated by microfilarial density and numbers of skin nodules. The isotype response to Ov-CHI-1 was dominated by the presence of IgG3, IgG1 was present to a lesser extent. Our results show a positive correlation between N- and C-termini of Ov-CHI-1 in their ability to provoke humoral and cellular immune responses in the human. Peripheral blood mononuclear cell (PBMC) proliferative responses to Ov-CHI-1 when assayed, were found to be significantly higher in the individuals from endemic areas and there was a statistically elevated response to Ov-CHI-1 in the infected individuals when compared to putative immune individuals. CONCLUSION: Ov-CHI-1 is an antigen that we have found strongly induces both humoral and cellular immune responses in humans

Conflicting expectations in transforming government service processes: the story of e-payment for social welfare in Ireland

Despite its clear potential and attractiveness as a solution to a broad range of societal problems, E-Government has not been adopted to levels predicted in early 2000 literature. Whilst case studies of punctual development of E-Government initiatives abound, few countries have progressed to high levels of maturity in the systematic use of ICT in the relationship between government and citizens. At the same time, the current period brings challenges in terms of access to public services and costs of delivering these services which make the large scale use of ICT by governments more attractive than ever, if not even a necessity. This paper presents a detailed case study of a specific E-Government initiative in Ireland in the area of E-payments for G2C, in the social welfare area. Locating the current initiative in its historical context, it analyses the varied motivations and conflicting requirements of the numerous stakeholders and discusses the constraints that bear on the potential scenarios that could be followed at this point in time

Cash or non-cash: that is the question - the story of e-payment for social welfare in Ireland part 2

E-Government in its various forms and extensions, notably T-Government, is often presented as the panacea for resolving such complex social problems as social exclusion, lack of governance transparency, poor value for money and other ailments of modern societies. Yet, E-Government has not been adopted up to predicted levels. Many case studies investigating success factors, maturity models, and the application of acceptance models have been presented over the last 15 years, but a deep understanding of the potential impact and consequences of E-Government is still lacking. This is especially true for those initiatives that involve socio-economic and cultural contexts, which makes their evaluation and the prediction of their impact difficult. This paper reports on an on-going E-Government initiative in Ireland aimed at implementing E-payments for G2C, notably in the social welfare area. Three sets of personal surveys have been carried out to understand the perceived impact of governmental plans of moving from an almost fully cash-based payment system to a fully electronic based solution. Early results indicate that perceived pre-requisites for the planned change may be misleading. The impact on recipients’ lives cannot solely be measured in terms of economic gains: the consequences of such implementation may well reach further than expected