Synthesis of the Beryllium 3131A Spectral Region

The Beryllium spectral region of the Sun, Procyon and 4 stars in the open cluster NGC6633 up to Teff = 7500K have been synthesised using ATLAS9 model atmospheres and the MOOG spectral synthesis program. The line list used for these syntheses has been modified from the ATLAS9 line list to improve the quality of the fits in light of the improved opacities in the new version of the MOOG code. Significant changes have been made to the Mn I line at ATLAS9 wavelength 3131.037A and an OH line has been added at 3131.358A. In addition there are a number of minor changes to gf-values throughout the synthesised region thus improving the fit for the spectra across the temperature range considerably.Comment: 4 pages, 3 figures. To appear in the proceedings of the Workshop "ATLAS 12 and related codes", Trieste, July 11-15, 200

Fiber-optic chemical sensing with Langmuir-Blodgett overlay waveguides

Fiber-optic chemical sensing has been demonstrated with a side-polished single- mode optical fiber, evanescently coupled to chemically sensitive Langmuir- Blodgett (LB) overlay waveguides. The sensors exhibit a channel-dropping response centered on a wavelength that is dependent on the thickness and the refractive index of the overlay waveguide. It has been shown that pH-sensitive organic dyes proved to be suitable materials fur the formation of an overlay waveguide whereas LB deposition provides the required thickness control. A theoretical model of the sensor response, based on the Kramers-Kronig relations and phase matching of the guided modes within the optical fiber and overlay waveguide, shows good agreement with experimental results

TWEAKing death

Smac mimetics (inhibitor of apoptosis [IAP] antagonists) are synthetic reagents that kill susceptible tumor cells by inducing degradation of cellular IAP (cIAP) 1 and cIAP2, nuclear factor κB activation, tumor necrosis factor (TNF) α production, TNF receptor 1 occupancy, and caspase-8 activation. In this issue of The Journal of Cell Biology, Vince et al. (see p. 171) report remarkable similarities in the events leading to tumor cell death triggered by the cytokine TWEAK (TNF-like weak inducer of apoptosis) and IAP antagonists. Although the mechanistic details differ, a common and necessary feature that is also shared by TNF receptor 2 signaling is reduction in the level of cIAP1 and, in some cases, cIAP2 and TNF receptor-associated factor 2. These findings not only extend our appreciation of how cell death pathways are kept in check in tumors, they reinforce the possible utility of induced cIDE (cIAP deficiency) in the selective elimination of neoplastic cells

The Li Overabundance of J37: Diffusion or Accretion?

In September 2002 the discovery of a super Li-rich F-dwarf (J37) in NGC 6633, an iron poor analogue of the better studied Hyades and Praecepe open clusters, was announced. This unique star was thought to be the smoking gun for the action of diffusion, models of which predict a narrow "Li-peak" at approximately the correct temperature. However, with more detailed studies into J37s abundance pattern this star provides firm evidence for the accretion of planetesimals or other material from the circumstellar environment of new born stars. Thanks to the specific predictions made about the behaviour of Be abundances, (the most striking of which being no Be in super-Li-rich dwarfs subject to diffusion) the opposing diffusion/accretion predictions can be tested. Initial modelling of the Be line indicates that J37 is as Be rich as it is Li rich; log N(Be) = 2.25 +/- 0.25, and so is broadly consistent with an accretion-fuelled enhancement. However, that both Li and Be are enhanced by much more than the iron-peak elements (as determined in previous studies) suggests that diffusion also plays a role in increasing the abundances of Li and Be specifically. Furthermore, a new data set from the UVES/UT2 combination has allowed the elemental abundance of Iron to be measured, and the set of preliminary stellar parameters determined; Teff ~ 7340 K, log g ~ 4.1, microturbulence ~ 4.3 km/s, [Fe/H] ~ 0.50. This again provides distinct evidence for the effects of accretion in J37 and requires a new synthesis of the Be doublet.Comment: 5 pages, 2 figures. Poster presented at IAU Symposium 224 "The A Star Puzzle", 7-13 July 2004, Poprad, Slovaki

Beryllium Enhancement as Evidence for Accretion in a Lithium-Rich F Dwarf

The early F dwarf star ``J37'' in the open cluster NGC6633 shows an unusual pattern of photospheric abundances, including an order of magnitude enhancement of lithium and iron-peak elements, but an under-abundance of carbon. As a consequence of its thin convection zone these anomalies have been attributed to either radiative diffusion or the accretion of hydrogen-depleted material. By comparing high resolution VLT/UVES spectra of J37 (and other F stars in NGC 6633) with syntheses of the Be ii doublet region at 3131 Ang, we establish that J37 also has a Be abundance (A(Be)=3.0+/-0.5) that is at least ten times the cosmic value. This contradicts radiative diffusion models that produce a Li over-abundance, as they also predict photospheric Be depletion. Instead, since Be is a highly refractory element, it supports the notion that J37 is the first clear example of a star that has accreted volatile-depleted material with a composition similar to chondritic meteorites, although some diffusion may be necessary to explain the low C and O abundances.Comment: Accepted for publication in MNRAS letters, 5 page

Activation of the Lck Tyrosine Kinase Targets Cell Surface T Cell Antigen Receptors for Lysosomal Degradation

AbstractThe mechanism by which TCR expression is regulated was explored by expressing a constitutively active form of the tyrosine kinase Lck (Lck505F) in T cells. Expression of Lck505F down-regulated TCR levels, an effect that was even more pronounced in CD45− T cells, in which the activity of this tyrosine kinase is further enhanced. Cells expressing Lck505F synthesized all TCR subunits, but lysosomal degradation of assembled receptors was enhanced. TCRs were rapidly internalized and degraded after removal of a tyrosine kinase inhibitor that had permitted cell surface expression. Finally, TCR levels on thymocytes were increased by an Lck inhibitor, and activation- but not phorbol ester–induced internalization of TCRs on Jurkat cells was prevented by inhibition or loss of Lck. These studies identify a regulated nonreceptor tyrosine kinase–mediated pathway for targeting cell surface receptors for lysosomal degradation

Carbon Deficiency in Externally-Polluted White Dwarfs: Evidence for Accretion of Asteroids

Existing determinations show that n(C)/n(Fe) is more than a factor of 10 below solar in the atmospheres of three white dwarfs that appear to be externally-polluted. These results are not easily explained if the stars have accreted interstellar matter, and we re-interpret these measurements as evidence that these stars have accreted asteroids of a chrondritic composition.Comment: 23 pages, 6 figures, accepted for Ap

Vaccine Hesitancy and Support for Employer Vaccine Mandates

This study investigated COVID-19 vaccine hesitancy and support for employer vaccine mandates and support for termination for non-vaccinated employees among a national sample in New Zealand. A total of 1852 individuals participated in the study. Results indicated participants who are able to get vaccinated are less likely to support employer mandated vaccinations and the rights of employers to terminate employees who refuse to get vaccinated. However, individuals who self-identify that they can get vaccinated and have higher confidence in the COVID-19 vaccine are more likely to get vaccinated. Age and confidence in the vaccine influence support for mandates, while age and political affiliation influenced support for employer right to terminate a non-vaccinated employee. Understanding support, or lack thereof, for such initiatives is essential as businesses and nations respond to growing COVID concerns.fals