On the Electronic Spectroscopy of Closed Shell Cations Derived From Resonance Stabilized Radicals: Insights From Theory and Franck-Condon Analysis

Context. Recent attention has been directed on closed-shell aromatic cations as potential carriers of the diffuse interstellar bands. The spectra of mass-selected, matrix-isolated benzylium, and tropylium cations were recently reported. The visible spectrum of benzylium exhibits a large Franck-Condon (FC) envelope, inconsistent with diffuse interstellar band carriers. Aims. We perform a computational analysis of the experimentally studied benzylium spectrum before extending the methods to a range of larger, closed-shell aromatic cations to determine the potential for this class of systems as diffuse interstellar band carriers. Methods. Density functional theory (DFT), time-dependant ((TD)DFT), and multi-configurational self-consistent field second-order perturbation theory (MRPT2) methods in concert with multidimensional FC analysis is used to model the benzylium spectrum. These methods are extended to larger closed-shell aromatic hydrocarbon cations derived from resonance-stabilized radicals, which are predicted to show strong S0 → Sn transitions in the visible region. The ionization energies of a range of these systems are also calculated by DFT. Results. The simulated benzylium spectrum was found to yield excellent agreement with the experimental spectrum showing an extended progression in a low frequency (510 cm-1) ring distortion mode. The FC progression was found to be significantly quenched in the larger species: 1-indanylium, 1-naphthylmethylium, and fluorenium. Excitation and ionization energies of the closed-shell cations were found to be consistent with diffuse interstellar band carriers, with the former lying in the visible range and the latter straddling the Lyman limit in the 13−14 eV range. Conclusions. Large closed-shell polycyclic aromatic hydrocarbon cations remain viable candidate carriers of the diffuse interstellar bands

Biased efficacy estimates in phase-III dengue vaccine trials due to heterogeneous exposure and differential detectability of primary infections across trial arms.

Vaccine efficacy (VE) estimates are crucial for assessing the suitability of dengue vaccine candidates for public health implementation, but efficacy trials are subject to a known bias to estimate VE toward the null if heterogeneous exposure is not accounted for in the analysis of trial data. In light of many well-characterized sources of heterogeneity in dengue virus (DENV) transmission, our goal was to estimate the potential magnitude of this bias in VE estimates for a hypothetical dengue vaccine. To ensure that we realistically modeled heterogeneous exposure, we simulated city-wide DENV transmission and vaccine trial protocols using an agent-based model calibrated with entomological and epidemiological data from long-term field studies in Iquitos, Peru. By simulating a vaccine with a true VE of 0.8 in 1,000 replicate trials each designed to attain 90% power, we found that conventional methods underestimated VE by as much as 21% due to heterogeneous exposure. Accounting for the number of exposures in the vaccine and placebo arms eliminated this bias completely, and the more realistic option of including a frailty term to model exposure as a random effect reduced this bias partially. We also discovered a distinct bias in VE estimates away from the null due to lower detectability of primary DENV infections among seronegative individuals in the vaccinated group. This difference in detectability resulted from our assumption that primary infections in vaccinees who are seronegative at baseline resemble secondary infections, which experience a shorter window of detectable viremia due to a quicker immune response. This resulted in an artefactual finding that VE estimates for the seronegative group were approximately 1% greater than for the seropositive group. Simulation models of vaccine trials that account for these factors can be used to anticipate the extent of bias in field trials and to aid in their interpretation

Spotting the diffusion of New Psychoactive Substances over the Internet

Online availability and diffusion of New Psychoactive Substances (NPS) represent an emerging threat to healthcare systems. In this work, we analyse drugs forums, online shops, and Twitter. By mining the data from these sources, it is possible to understand the dynamics of drugs diffusion and their endorsement, as well as timely detecting new substances. We propose a set of visual analytics tools to support analysts in tackling NPS spreading and provide a better insight about drugs market and analysis

Pancreatic Cyst Fluid Vascular Endothelial Growth Factor A and Carcinoembryonic Antigen: A Highly Accurate Test for the Diagnosis of Serous Cystic Neoplasm

Background Accurate differentiation of pancreatic cystic lesions is important for early detection and prevention of pancreatic cancer, as well as avoidance of unnecessary surgical intervention. Serous cystic neoplasms (SCNs) have no malignant potential, but can mimic the following premalignant mucinous cystic lesions: mucinous cystic neoplasm and intraductal papillary mucinous neoplasm (IPMN). We recently identified vascular endothelial growth factor (VEGF)-A as a novel pancreatic fluid biomarker for SCN. We hypothesize that combining cyst fluid CEA with VEGF-A will improve the diagnostic accuracy of VEGF-A. Methods Pancreatic cyst/duct fluid was collected from consenting patients undergoing surgical cyst resection with corresponding pathologic diagnoses. Pancreatic fluid VEGF-A and CEA levels were detected by ELISA. Results One hundred and forty-nine patients with pancreatic cystic lesions met inclusion criteria. Pathologic diagnoses included pseudocyst (n = 14), SCN (n = 26), mucinous cystic neoplasm (n = 40), low-/moderate-grade IPMN (n = 34), high-grade IPMN (n = 20), invasive IPMN (n = 10), and solid pseudopapillary neoplasm (n = 5). Vascular endothelial growth factor A was significantly elevated in SCN cyst fluid compared with all other diagnoses (p 5,000 pg/mL, VEGF-A alone has 100% sensitivity and 83.7% specificity to distinguish SCNs from other cystic lesions. With a threshold of ≤10 ng/mL, CEA alone identifies SCN with 95.5% sensitivity and 81.5% specificity. Sensitivity and specificity of the VEGF-A/CEA combination are 95.5% and 100%, respectively. The c-statistic increased from 0.98 to 0.99 in the receiver operating characteristic analysis when CEA was added to VEGF-A alone. Conclusions Although VEGF-A alone is a highly accurate test for SCN, the combination of VEGF-A with CEA approaches the gold standard for pathologic diagnosis, importantly avoiding false positives. Patients with a positive test indicating benign SCN can be spared a high-risk surgical pancreatic resection

Weak Lensing Effects on the Galaxy Three-Point Correlation Function

We study the corrections to the galaxy three-point correlation function (3PCF) induced by weak lensing magnification due to the matter distribution along the line of sight. We consistently derive all the correction terms arising up to second order in perturbation theory and provide analytic expressions as well as order of magnitude estimates for their relative importance. The magnification contributions depend on the geometry of the projected triangle on the sky plane, and scale with different powers of the number count slope and redshift of the galaxy sample considered. We evaluate all terms numerically and show that, depending on the triangle configuration as well as the galaxy sample considered, weak lensing can in general significantly contribute to and alter the three-point correlation function observed through galaxy and quasar catalogs.Comment: 24 pages, 11 figures; version accepted for publication in Phys. Rev. D; v2: typos corrected, figure caption clarifie

Near-optimal mean value estimates for multidimensional Weyl sums

We obtain sharp estimates for multidimensional generalisations of Vinogradov's mean value theorem for arbitrary translation-dilation invariant systems, achieving constraints on the number of variables approaching those conjectured to be the best possible. Several applications of our bounds are discussed

Impact of high CO2 on the geochemistry of the coralline algae Lithothamnion glaciale

Coralline algae are a significant component of the benthic ecosystem. Their ability to withstand physical stresses in high energy environments relies on their skeletal structure which is composed of high Mg-calcite. High Mg-calcite is, however, the most soluble form of calcium carbonate and therefore potentially vulnerable to the change in carbonate chemistry resulting from the absorption of anthropogenic CO2 by the ocean. We examine the geochemistry of the cold water coralline alga Lithothamnion glaciale grown under predicted future (year 2050) high pCO2 (589 μatm) using Electron microprobe and NanoSIMS analysis. In the natural and control material, higher Mg calcite forms clear concentric bands around the algal cells. As expected, summer growth has a higher Mg content compared to the winter growth. In contrast, under elevated CO2 no banding of Mg is recognisable and overall Mg concentrations are lower. This reduction in Mg in the carbonate undermines the accuracy of the Mg/Ca ratio as proxy for past temperatures in time intervals with significantly different carbonate chemistry. Fundamentally, the loss of Mg in the calcite may reduce elasticity thereby changing the structural properties, which may affect the ability of L. glaciale to efficiently function as a habitat former in the future ocean

Dark matter halo concentrations in the Wilkinson Microwave Anisotropy Probe year 5 cosmology

We use a combination of three large N-body simulations to investigate the dependence of dark matter halo concentrations on halo mass and redshift in the WMAP year 5 cosmology. The median relation between concentration and mass is adequately described by a power-law for halo masses in the range 10^11 - 10^15 Msol/h and redshifts z < 2, regardless of whether the halo density profiles are fit using NFW or Einasto profiles. Compared with recent analyses of the Millennium Simulation, which uses a value of sigma_8 that is higher than allowed by WMAP5, z = 0 halo concentrations are reduced by factors ranging from 23 per cent at 10^11 Msol/h to 16 per cent at 10^14 Msol/h. The predicted concentrations are much lower than inferred from X-ray observations of groups and clusters.Comment: 6 pages, 4 figures, Accepted by MNRAS letters. Version 4: Typo fixe

Phase diagram and phase transitions in ferroelectric tris-sarcosine calcium chloride and its brominated isomorphs

Tris-sarcosine calcium chloride [(TSCC), (CH3NHCH2COOH)3CaCl2] is a uniaxial ferroelectric (FE) with a displacive second-order phase transition near Tc=130 K. A continuous range of solid solutions can be made by substituting Br for Cl, which lowers Tc to 0 K at ∼72% Br. Such a quantum critical point differs from that in pseudocubic FEs, such as O-18 SrTiO3 or doped KTaO3. For many years, this system was thought to have only two phases, paraelectric and FE, at ambient pressure. However, we find from dielectric and resonant ultrasound spectroscopy that there are four phase transitions in TSCC and in TSCC:Br (for 0 < Br < 40%): Order-disorder of the sarcosine methyl group at 185 K; displacive FE transition at 130 K (in pure TSCC); a second FE transition [previously hypothesized to be antiferroelectric (AFE) but probably not] at 64 K; and a new anomaly at ∼45 K which might be due to a phase transition or to Debye-like freezing of orientational disorder of some part of the sarcosine molecule. The probable sequence of structures is (upon cooling): Pnma with Z=4(D2h16) ambient 500 K > T > 185 K, disordered; Pnma with Z=4(D2h16)185 K>T>130 K (ordered); Pn21a with Z=4(C2v9)130 K>T>64 K (FE); P21a (C2h5) with Z =4, 64 K > T > 45 K (not AFE); T < 45 K, unknown structure. A sixth hexagonal structure at high temperatures (>500 K) is hypothesized to be D6h3(P63/mcm) with Z =2, but the samples decompose first at 503 K (230 °C)

The nature of iron-oxygen vacancy defect centers in PbTiO3

The iron(III) center in ferroelectric PbTiO3 together with an oxygen vacancy forms a charged defect associate, oriented along the crystallographic c-axis. Its microscopic structure has been analyzed in detail comparing results from a semi-empirical Newman superposition model analysis based on finestructure data and from calculations using density functional theory. Both methods give evidence for a substitution of Fe3+ for Ti4+ as an acceptor center. The position of the iron ion in the ferroelectric phase is found to be similar to the B-site in the paraelectric phase. Partial charge compensation is locally provided by a directly coordinated oxygen vacancy. Using high-resolution synchrotron powder diffraction, it was verified that lead titanate remains tetragonal down to 12 K, exhibiting a c/a-ratio of 1.0721.Comment: 11 pages, 5 figures, accepted in Phys. Rev.