Towards More Precise Survey Photometry for PanSTARRS and LSST: Measuring Directly the Optical Transmission Spectrum of the Atmosphere

Motivated by the recognition that variation in the optical transmission of the atmosphere is probably the main limitation to the precision of ground-based CCD measurements of celestial fluxes, we review the physical processes that attenuate the passage of light through the Earth's atmosphere. The next generation of astronomical surveys, such as PanSTARRS and LSST, will greatly benefit from dedicated apparatus to obtain atmospheric transmission data that can be associated with each survey image. We review and compare various approaches to this measurement problem, including photometry, spectroscopy, and LIDAR. In conjunction with careful measurements of instrumental throughput, atmospheric transmission measurements should allow next-generation imaging surveys to produce photometry of unprecedented precision. Our primary concerns are the real-time determination of aerosol scattering and absorption by water along the line of sight, both of which can vary over the course of a night's observations.Comment: 41 pages, 14 figures. Accepted PAS

Stakes sensitivity and credit rating: a new challenge for regulators

The ethical practices of credit rating agencies (CRAs), particularly following the 2008 financial crisis, have been subject to extensive analysis by economists, ethicists, and policymakers. We raise a novel issue facing CRAs that has to do with a problem concerning the transmission of epistemic status of ratings from CRAs to the beneficiaries of the ratings (investors, etc.), and use it to provide a new challenge for regulators. Building on recent work in philosophy, we argue that since CRAs have different stakes than the beneficiaries of the ratings in the ratings being accurate, what counts as knowledge (and as having ‘epistemic status’) concerning credit risk for a CRA may not count as knowledge (as having epistemic status) for the beneficiary. Further, as it stands, many institutional investors (pension funds, insurance companies, etc.) are bound by law to make some of their investment decisions dependent on the ratings of officially recognized CRAs. We argue that the observation that the epistemic status of ratings does not transmit from CRAs to beneficiaries makes salient a new challenge for those who think current regulation regarding the CRAs is prudentially justified, namely, to show that the harm caused by acting on a rating that does not have epistemic status for beneficiaries is compensated by the benefit from them acting on a CRA rating that does have epistemic status for the CRA. Unlike most other commentators, therefore, we offer a defeasible reason to drop references to CRAs in prudential regulation of the financial industry

Molecular mechanisms for the regulation of histone mRNA stem-loop-binding protein by phosphorylation

As DNA is replicated during cell division, it must be packaged by histones. To match the level of available histones to DNA replication, histone mRNA expression is controlled by a 3′-end stem-loop structure unique to replication-dependent histone mRNAs. In Drosophila, this regulation is mediated by histone mRNA stem-loop–binding protein (dSLBP), which has minimal tertiary structure when not bound to RNA. We show here that phosphorylation of dSLBP dramatically increases binding affinity for stem-loop RNA. The phosphorylated C-terminal tail of dSLBP does not contact RNA. Instead, increased negative charge on the C-terminal tail and stabilization of structural elements by a phosphorylation site within the RNA-binding domain promote more compact conformations that should reduce the entropic barrier to binding histone mRNA

NMR Solution Structure of the Focal Adhesion Targeting Domain of Focal Adhesion Kinase in Complex with a Paxillin LD Peptide: EVIDENCE FOR A TWO-SITE BINDING MODEL

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that is regulated by integrins. Upon activation, FAK generates signals that modulate crucial cell functions, including cell proliferation, migration, and survival. The C-terminal focal adhesion targeting (FAT) sequence mediates localization of FAK to discrete regions in the cell called focal adhesions. Several binding partners for the FAT domain of FAK have been identified, including paxillin. We have determined the solution structure of the avian FAT domain in complex with a peptide mimicking the LD2 motif of paxillin by NMR spectroscopy. The FAT domain retains a similar fold to that found in the unliganded form when complexed to the paxillin-derived LD2 peptide, an antiparallel four-helix bundle. However, noticeable conformational changes were observed upon the LD2 peptide binding, especially the position of helix 4. Multiple lines of evidence, including the results obtained from isothermal titration calorimetry, intermolecular nuclear Overhauser effects, mutagenesis, and protection from paramagnetic line broadening, support the existence of two distinct paxillin-binding sites on the opposite faces of the FAT domain. The structure of the FAT domain-LD2 complex was modeled using the program HADDOCK based on our solution structure of the LD2-bound FAT domain and mutagenesis data. Our model of the FAT domain-LD2 complex provides insight into the molecular basis of FAK-paxillin binding interactions, which will aid in understanding the role of paxillin in FAK targeting and signaling

Sequential Star Formation in RCW 34: A Spectroscopic Census of the Stellar Content of High-mass Star-forming Regions

We present VLT/SINFONI integral field spectroscopy of RCW 34 along with Spitzer/IRAC photometry of the surroundings. RCW 34 consists of three different regions. A large bubble has been detected on the IRAC images in which a cluster of intermediate- and low-mass class II objects is found. At the northern edge of this bubble, an HII region is located, ionized by 3 OB stars. Intermediate mass stars (2 - 3 Msun) are detected of G- and K- spectral type. These stars are still in the pre-main sequence (PMS) phase. North of the HII region, a photon-dominated region is present, marking the edge of a dense molecular cloud traced by H2 emission. Several class 0/I objects are associated with this cloud, indicating that star formation is still taking place. The distance to RCW 34 is revised to 2.5 +- 0.2 kpc and an age estimate of 2 - 1 Myrs is derived from the properties of the PMS stars inside the HII region. The most likely scenario for the formation of the three regions is that star formation propagates from South to North. First the bubble is formed, produced by intermediate- and low-mass stars only, after that, the HII region is formed from a dense core at the edge of the molecular cloud, resulting in the expansion as a champagne flow. More recently, star formation occurred in the rest of the molecular cloud. Two different formation scenarios are possible: (a) The bubble with the cluster of low- and intermediate mass stars triggered the formation of the O star at the edge of the molecular cloud which in turn induces the current star-formation in the molecular cloud. (b) An external triggering is responsible for the star-formation propagating from South to North. [abridged]Comment: 19 pages, 11 figures, accepted by Ap

Mapping genetic determinants of host susceptibility to Pseudomonas aeruginosa lung infection in mice.

Background: P. aeruginosa is one of the top three causes of opportunistic human bacterial infections. The remarkable variability in the clinical outcomes of this infection is thought to be associated with genetic predisposition. However, the genes underlying host susceptibility to P. aeruginosa infection are still largely unknown. Results: As a step towards mapping these genes, we applied a genome wide linkage analysis approach to a mouse model. A large F2 intercross population, obtained by mating P. aeruginosa-resistant C3H/HeOuJ, and susceptible A/J mice, was used for quantitative trait locus (QTL) mapping. The F2 progenies were challenged with a P. aeruginosa clinical strain and monitored for the survival time up to 7 days post-infection, as a disease phenotype associated trait. Selected phenotypic extremes of the F2 distribution were genotyped with high-density single nucleotide polymorphic (SNP) markers, and subsequently QTL analysis was performed. A significant locus was mapped on chromosome 6 and was named P. aeruginosa infection resistance locus 1 (Pairl1). The most promising candidate genes, including Dok1, Tacr1, Cd207, Clec4f, Gp9, Gata2, Foxp1, are related to pathogen sensing, neutrophils and macrophages recruitment and inflammatory processes. Conclusions: We propose a set of genes involved in the pathogenesis of P. aeruginosa infection that may be explored to complement human studie

Evidence for Quantum Interference in SAMs of Arylethynylene Thiolates in Tunneling Junctions with Eutectic Ga-In (EGaIn) Top-Contacts

This paper compares the current density (J) versus applied bias (V) of self-assembled monolayers (SAMs) of three different ethynylthiophenol-functionalized anthracene derivatives of approximately the same thickness with linear-conjugation (AC), cross-conjugation (AQ), and broken-conjugation (AH) using liquid eutectic Ga-In (EGaIn) supporting a native skin (~1 nm thick) of Ga2O3 as a nondamaging, conformal top-contact. This skin imparts non-Newtonian rheological properties that distinguish EGaIn from other top-contacts; however, it may also have limited the maximum values of J observed for AC. The measured values of J for AH and AQ are not significantly different (J ≈ 10-1 A/cm2 at V = 0.4 V). For AC, however, J is 1 (using log averages) or 2 (using Gaussian fits) orders of magnitude higher than for AH and AQ. These values are in good qualitative agreement with gDFTB calculations on single AC, AQ, and AH molecules chemisorbed between Au contacts that predict currents, I, that are 2 orders of magnitude higher for AC than for AH at 0 < |V| < 0.4 V. The calculations predict a higher value of I for AQ than for AH; however, the magnitude is highly dependent on the position of the Fermi energy, which cannot be calculated precisely. In this sense, the theoretical predictions and experimental conclusions agree that linearly conjugated AC is significantly more conductive than either cross-conjugated AQ or broken conjugate AH and that AQ and AH cannot necessarily be easily differentiated from each other. These observations are ascribed to quantum interference effects. The agreement between the theoretical predictions on single molecules and the measurements on SAMs suggest that molecule-molecule interactions do not play a significant role in the transport properties of AC, AQ, and AH.

What anti-realism about hinges could possibly be?

The paper addresses the issue of what epistemic anti-realism could possibly be, in the context of “hinge epistemology.” According to this new epistemological trend, justification depends on evidence together with general background assumptions—for example, that there is an external world, that our sense organs are mostly reliable, that we are not the victims of persistent and lucid dreams what has regularly happened in the past will happen in the future, that people are generally reliable informants, and so on. The paper then addresses two issues. First, whether these assumptions are arbitrary, as relativists would claim. Second, how we should conceive of their metaphysical status. It responds negatively to the first question and puts forward an anti-realist conception of hinges to respond to the latter. Central to the proposal is that the kind of truth that can be predicated of hinges is of a minimalist kind. The paper also explores the compatibility of minimalism about hinges' truth and alethic pluralism