15,583 research outputs found
Anomaly mediated neutrino-photon interactions at finite baryon density
We propose new physical processes based on the axial vector anomaly and
described by the Wess-Zumino-Witten term that couples the photon, Z-boson, and
the omega-meson. The interaction takes the form of a pseudo-Chern-Simons term,
. This term
induces neutrino-photon interactions at finite baryon density via the coupling
of the Z-boson to neutrinos. These interactions may be detectable in various
laboratory and astrophysical arenas. The new interactions may account for the
MiniBooNE excess. They also produce a competitive contribution to neutron star
cooling at temperatures >10^9 K. These processes and related axion--photon
interactions at finite baryon density appear to be relevant in many
astrophysical regimes.Comment: 4 pages, 2 figures; references adde
Zinc abundances in Galactic bulge field red giants: implications for DLA systems
Zinc in stars is an important reference element because it is a proxy to Fe
in studies of damped Lyman-alpha systems, permitting a comparison of chemical
evolution histories of bulge stellar populations and DLAs. In terms of
nucleosynthesis, it behaves as an alpha element because it is enhanced in
metal-poor stars. The aim of this work is to derive the iron-peak element Zn
abundances in 56 bulge giants from high resolution spectra. These results are
compared with data from other bulge samples, as well as from disk and halo
stars, and damped Lyman-alpha systems, in order to better understand the
chemical evolution in these environments. High-resolution spectra were obtained
using FLAMES+UVES on the Very Large Telescope. We find [Zn/Fe]=+0.24+-0.02 in
the range -1.3 < [Fe/H] < -0.5 and [Zn/Fe]=+0.06+-0.02 in the range -0.5 <
[Fe/H] -0.1, it shows a spread of -0.60 < [Zn/Fe]
< +0.15, with most of these stars having low [Zn/Fe]<0.0. These low zinc
abundances at the high metallicity end of the bulge define a decreasing trend
in [Zn/Fe] with increasing metallicities. A comparison with Zn abundances in
DLA systems is presented, where a dust-depletion correction was applied for
both Zn and Fe. Finally, we present a chemical evolution model of Zn enrichment
in massive spheroids, representing a typical classical bulge.Comment: Accepted in Astronomy & Astrophysics, in press Date of acceptance:
13/05/2015. 19 pages, 14 Figs in Astronomy & Astrophysics, 201
An In Vitro Comparison of A Novel Self-Assembling Peptide Matrix Gel and Selected Desensitizing Toothpastes in Reducing Fluid Flow by Dentine Tubular Occlusion
Objectives: The objective of this explorative in vitro study was to evaluate the ability of a novel self-assembling peptide matrix gel with calcium phosphate in effectively occluding dentine tubules compared to selected desensitizing toothpastes. Methods: Mid-coronal dentine discs with a thickness of 1 mm were sectioned from caries-free human molars. The discs were etched with 6% citric acid for 2 minutes, halved and subjected to a 2-minute brushing with a novel gel (SAPM) and three selected desensitizing toothpastes ([SRP], [SRR] and [CSP]). The ability of the desensitizing gel and toothpastes to occlude the dentine tubules was assessed and compared before and after brushing using Scanning Electron Microscopy (SEM) on both etched and fractured dentine surfaces. The SEM observations were supplemented by hydraulic conductance measurements using a modified Pashley model before and after tooth brushing (n=5). Results: The results demonstrated that there was a reduction in both the number and the diameter of the open dentine tubules, which was evident for all the treated dentine discs. The particles that occluded the open dentine tubules, however had different morphologies and distribution. The selfassembling peptide matrix gel (SAPM) demonstrated greater reduction in the number of open tubules compared to the other desensitizing toothpastes. Reductions in the hydraulic conductance measurements were observed for all tested materials (mean [SD, %]: SAPM 55.1 [12.5], SRP 64.9 [18.5], SRR 39.1 [17.1] and CSP 27.6 [6.8]). No statistically differences were observed between the SAPM and SRP, SRR toothpastes (paired t-Test; ≤0.05) although a significant difference was noted between the SAPM and the CSP toothpastes. There was an overall trend for reduction for the SAPM compared to the SRR toothpaste. Conclusion: The results would suggest that a novel self-assembling peptide matrix gel (SAPM) was effective in blocking the dentine tubules and may therefore have the potential to be an effective desensitizing product for the treatment of Dentine Hypersensitivity
The Chemical Enrichment History of the Small Magellanic Cloud and Its Gradients
We present stellar metallicities derived from Ca II triplet spectroscopy in
over 350 red giant branch stars in 13 fields distributed in different positions
in the SMC, ranging from 1\arcdeg\@ to 4\arcdeg\@ from its center.
In the innermost fields the average metallicity is [Fe/H] . This value
decreases when we move away towards outermost regions. This is the first
detection of a metallicity gradient in this galaxy. We show that the
metallicity gradient is related to an age gradient, in the sense that more
metal-rich stars, which are also younger, are concentrated in the central
regions of the galaxy.Comment: 30 pages, 13 figures, accepted for publication in Astronomical
Journa
Towards preventing and managing conflict of interest in nutrition policy? An analysis of submissions to a consultation on a draft WHO tool
Background: With multi-stakeholder approaches central to efforts to address global health challenges, debates around conflict of interest (COI) are increasingly prominent. The World Health Organization (WHO) recently developed a proposed tool to support member states in preventing and managing COI in nutrition policy. We analysed responses to an online consultation to explore how actors from across sectors understand COI and the ways in which they use this concept to frame the terms of commercial sector engagement in health governance. Methods: Submissions from 44 Member States, international organisations, non-governmental organizations (NGOs), academic institutions and commercial sector actors were coded using a thematic framework informed by framing theory. Respondents’ orientation to the tool aligned with two broad frames, ie, a ‘collaboration and partnership’ frame that endorsed multi-stakeholder approaches and a ‘restricted engagement’ frame that highlighted core tensions between public health and food industry actors. Results: Responses to the WHO tool reflected contrasting conceptualisations of COI and implications for health governance. While most Member States, NGOs, and academic institutions strongly supported the tool, commercial sector organisations depicted it as inappropriate, unworkable and incompatible with the Sustainable Development Goals (SGDs). Commercial sector respondents advanced a narrow, individual-level understanding of COI, seen as adequately addressed by existing mechanisms for disclosure, and viewed the WHO tool as unduly restricting scope for private sector engagement in nutrition policy. In contrast, health-focused NGOs and several Member States drew on a more expansive understanding of COI that recognised scope for wider tensions between public health goals and commercial interests and associated governance challenges. These submissions mostly welcomed the tool as an innovative approach to preventing and managing such conflicts, although some NGOs sought broader exclusion of corporate actors from policy engagement. Conclusion: Submissions on the WHO tool illustrate how contrasting positions on COI are central to understanding broader debates in nutrition policy and across global health governance. Effective health governance requires greater understanding of how COI can be conceptualised and managed amid high levels of contestation on policy engagement with commercial sector actors. This requires both ongoing innovation in governance tools and more extensive conceptual and empirical research
Origin of the unusually low nitrogen abundances in young populations of the Large Magellanic Cloud
It is a longstanding problem that HII regions and very young stellar
populations in the Large Magellanic Cloud (LMC) have the nitrogen abundances
([N/H]) by a factor of ~7 lower than the solar value. We here discuss a new
scenario in which the observed unusually low nitrogen abundances can be closely
associated with recent collision and subsequent accretion of HI high velocity
clouds (HVCs) that surround the Galaxy and have low nitrogen abundances. We
show that if the observed low [N/H] is limited to very young stars with ages
less than ~10^7 yr, then the collision/accretion rate of the HVCs onto the LMC
needs to be ~ 0.2 M_sun/yr (corresponding to the total HVC mass of 10^6-10^7
M_sun) to dilute the original interstellar medium (ISM) before star formation.
The required accretion rate means that even if the typical mass of HVCs
accreted onto the LMC is ~ 10^7 M_sun, the Galaxy needs to have ~2500 massive
HVCs within the LMC's orbital radius with respect to the Galactic center. The
required rather large number of massive HVCs drives us to suggest that the HVCs
are not likely to efficiently dilute the ISM of the LMC and consequently lower
the [N/H]. We thus suggest the transfer of gas with low [N/H] from the Small
Magellanic Cloud (SMC) to the LMC as a promising scenario that can explain the
observed low [N/H].Comment: 24pages, 6 figures, accepted in Ap
Ca II Triplet Spectroscopy of Small Magellanic Cloud Red Giants. I. Abundances and Velocities for a Sample of Clusters
We have obtained near-infrared spectra covering the Ca II triplet lines for a
number of stars associated with 16 SMC clusters using the VLT + FORS2. These
data compose the largest available sample of SMC clusters with
spectroscopically derived abundances and velocities. Our clusters span a wide
range of ages and provide good areal coverage of the galaxy. Cluster members
are selected using a combination of their positions relative to the cluster
center as well as their abundances and radial velocities. We determine mean
cluster velocities to typically 2.7 km/s and metallicities to 0.05 dex (random
errors), from an average of 6.4 members per cluster. (continued in paper)Comment: 68 pages, 15 figures, Accepted to AJ Reason for the replacement:
section 7 and fig. 9 have been modified according referee suggestion
Fermentation kinetics including product and substrate inhibitions plus biomass death: a mathematical analysis
Fermentation is generally modelled by kinetic equations giving the time
evolutions for biomass, substrate, and product concentrations. Although these
equations can be solved analytically in simple cases if substrate/product
inhibition and biomass death are included, they are typically solved
numerically. We propose an analytical treatment of the kinetic equations
--including cell death and an arbitrary number of inhibitions-- in which
constant yield needs not be assumed. Equations are solved in phase space, i.e.
the biomass concentration is written explicitly as a function of the substrate
concentration.Comment: 4 pages, 4 figure
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