Optimizing interpolation of shoot density data from a Posidonia oceanica seagrass bed

A case study on the optimization of Posidonia oceanica density interpolation, using a data set from a large meadow at Porto Conte Bay (NW Sardinia, Italy), is presented. Ordinary point kriging, cokriging and a weighted average based on inverse square distance were used to interpolate density data measured in 36 sampling stations. The results obtained from different methods were then compared by means of a leave-one-out cross-validation procedure. The scale at which interpolation was carried out was defined on the basis of the Hausdorff dimension of the variogram. Optimizing spatial scale and data points search strategy allowed obtaining more accurate density estimates independently of the interpolation method

Inducing charges and currents from extra dimensions

In a particular variant of Kaluza-Klein theory, the so-called induced-matter theory (IMT), it is shown that any configuration of matter may be geometrically induced from a five-dimensional vacuum space. By using a similar approach we show that any distribution of charges and currents may also be induced from a five-dimensional vacuum space. Whereas in the case of IMT the geometry is Riemannian and the fundamental equations are the five-dimensional Einstein equations in vacuum, here we consider a Minkowskian geometry and the five-dimensional Maxwell equations in vacuum.Comment: 8 pages. Accepted for publication in Modern Physics Letters

Distribution and Intracellular Localization of Titanium in Plants After Titanium Treatment

The physiological role of titanium in plants has not been elucidated yet, but a higher rate of growth , greater chlorophyll content and higher productivity, among others , may be attributed to this element. We have investigated the distribution of titanium in wheat seedlings after Titavit (a Ti ·ascorbate containing plant conditioner) treatment applied either through the leaf or through the root. In field experiments, we also sprayed spinach plants with Titavit. We have found a practically unidirectional tran slocation of Ti from the shoot into the root, and a preferential local ization of Ti in the nuclear cell fraction as seen by JCP-AES (inductively coupled plasma atomic emission spectrometry). Electron microscopic X·ray microanalysis after chemical fixation showed little or no accumulation of Ti in the cells of the treated organs . However, if there was in appreciable Xray emission at 4.5 keV (Ti), it was recorded from the nucleoplasm and nucleolus. The comparison of ICPAES and X-ray analyses leads us to the conclusion that the majority of Ti may be in a diffusible form in the treated cells, except the nuclei, where Ti may be bound firmly

Predictors of the perceived risk of COVID-19 and adherence to confinement guidelines in the context of the COVID-19 pandemic

INTRODUCTION: Complete adherence to public health guidelines is essential to reduce the spread of COVID-19. Studies on the factors associated with increased/decreased adherence to these measures have the potential to inform public policies directed at increasing adherence, and thus helping to control the spread of the current pandemic. OBJECTIVES: This study aimed at assessing the demographic and psychosocial predictors of the perceived risk of the COVID-19 and adherence to confinement guidelines during the first mandatory lockdown in Portugal. METHODS: A convenience sample of 430 adults living in Portugal between March 19(th) and May 2(nd,) 2020 completed an online survey asking participants about the perceived risk of the COVID-19 and adherence to confinement guidelines. Participants also completed a sociodemographic questionnaire and measures of psychological function. Multiple regression analysis was performed. RESULTS: Teleworking and Risk and COVID-19 controllability were significant predictors of the perceived risk of COVID-19 as measured by the perceived risk of being infected with COVID-19. Teleworking participants and those perceiving COVID-19 as less controllable reported a higher perceived risk of being infected with COVID-19 than those who were not in telework and perceived COVID-19 as a controllable condition. Adherence to confinement guidelines was predicted by the mental health status and perceived risk of COVID-19. Participants who reported worse mental health status, who perceived COVID-19 as a dangerous condition, and who trusted the public health system reported greater adherence to confinement guidelines. CONCLUSIONS: The results of this study will be discussed considering their implications to public health policymaking to promote adherence to public health policies. DISCLOSURE: No significant relationships

Solvation of alkane and alcohol molecules. Energy contributions

In this work we conduct a systematic ab initio study of the solvation of small alkane, monoalcohol and diol molecules, in polar solvents with different properties. A choice of basis set suitable for the type of compounds under study is presented. The various components of the solvent–solute interaction and the cavitation energy are treated individually and their variation with chain length and introduction of hydroxy groups assessed. The use of solute molecules in which controlled changes are imposed allows for an estimation of the relative contributions, thus eliminating accidental error cancellation.Fundacão para a Ciência e Tecnologia SAPIENS POCTI/35415/QUI/200

The "K-Correction" for Irradiated Emission Lines in LMXBs: Evidence for a Massive Neutron Star in X1822-371 (V691 CrA)

We study the K-correction for the case of emission lines formed in the X-ray illuminated atmosphere of a Roche lobe filling star. We compute the K-correction as function of the mass ratio 'q' and the disc flaring angle 'alpha' using a compact binary code where the companion's Roche lobe is divided into 10^5 resolution elements. We also study the effect of the inclination angle in the results. We apply our model to the case of the neutron star low-mass X-ray binary X1822-371 (V691 CrA), where a K-emission velocity K_em=300 +-8 km/s has been measured by Casares et al. (2003). Our numerical results, combined with previous determination of system parameters, yields 1.61Msun < M_NS < 2.32Msun and 0.44Msun < M_2 < 0.56Msun for the two binary components(i. e. 0.24 < q < 0.27), which provide a compelling evidence for a massive neutron star in this system. We also discuss the implications of these masses into the evolutionary history of the binary.Comment: 6 pages, 5 figures. Accepted for publication in Ap

The Nature of the Secondary Star in the Black Hole X-Ray Transient V616 Mon (=A0620-00)

We have used NIRSPEC on Keck II to obtain $K$-band spectroscopy of the low mass X-ray binary V616 Mon (= A0620$-$00). V616 Mon is the proto-typical soft x-ray transient containing a black hole primary. As such it is important to constrain the masses of the binary components. The modeling of the infrared observations of ellipsoidal variations in this system lead to a derived mass of 11.0 M_{\sun} for the black hole. The validity of this derivation has been called into question due to the possiblity that the secondary star's spectral energy distribution is contaminated by accretion disk emission (acting to dilute the variations). Our new $K$-band spectrum of V616 Mon reveals a late-type K dwarf secondary star, but one that has very weak $^{\rm 12}$CO absorption features. Comparison of V616 Mon with SS Cyg leads us to estimate that the accretion disk supplies only a small amount of $K$-band flux, and the ellipsoidal variations are not seriously contaminated. If true, the derived orbital inclination of V616 Mon is not greatly altered, and the mass of the black hole remains large. A preliminary stellar atmosphere model for the $K$-band spectrum of V616 Mon reveals that the carbon abundance is approximately 50% of the solar value. We conclude that the secondary star in V616 Mon has either suffered serious contamination from the accretion of supernova ejecta that created the black hole primary, or it is the stripped remains of a formerly more massive secondary star, one in which the CNO cycle had been active.Comment: 20 pages, 5 figure

The Decay D0→Kˉ∗0π−e+νeD^0\to \bar K^{*0} \pi^- e^+ \nu_e in the Context of Chiral Perturbation Theory

We study the decay $D^0\rightarrow \bar K^{*0} \pi^- e^+ \nu_e$, using $SU(2)_L \otimes SU(2)_R$ chiral perturbation theory for heavy charmed mesons and vector mesons, in the kinematic regime where $p_M \cdot p_\pi/m_M$ (here $M = D^0$ or $\bar K^{*0}$) is much smaller than the chiral symmetry breaking scale, $\Lambda_{\chi SB}$ ( $\Lambda_{\chi SB} \sim$ 1 GeV). We present the leading diagrams and amplitude, and calculate the rate, in the region where, to leading order in our calculations, the $\bar K^{*0}$ is at zero recoil in the $D^0$ rest frame. The rate thus calculated is given in terms of a known form factor and depends on the $DD^* \pi$ coupling constant $g_D$ of the heavy (charmed) meson chiral perturbation theory Lagrangian. A measurement of the above decay, in the aforementioned kinematic regime, can result in the extraction of an experimental value for $g_D$, accurate at the level of our approximations, and give us a measure of the validity of approaches based on chiral perturbation theory in studying similar processes.Comment: 17 pages, Latex, 2 embedded postscript figure

Do item-writing flaws reduce examinations psychometric quality?

Background The psychometric characteristics of multiple-choice questions (MCQ) changed when taking into account their anatomical sites and the presence of item-writing flaws (IWF). The aim is to understand the impact of the anatomical sites and the presence of IWF in the psychometric qualities of the MCQ. Results 800 Clinical Anatomy MCQ from eight examinations were classified as standard or flawed items and according to one of the eight anatomical sites. An item was classified as flawed if it violated at least one of the principles of item writing. The difficulty and discrimination indices of each item were obtained. 55.8 % of the MCQ were flawed items. The anatomical site of the items explained 6.2 and 3.2 % of the difficulty and discrimination parameters and the IWF explained 2.8 and 0.8 %, respectively. Conclusions The impact of the IWF was heterogeneous, the Writing the Stem and Writing the Choices categories had a negative impact (higher difficulty and lower discrimination) while the other categories did not have any impact. The anatomical site effect was higher than IWF effect in the psychometric characteristics of the examination. When constructing MCQ, the focus should be in the topic/area of the items and only after in the presence of IWF.This work was supported by the IJUP Project under Grant Number PP_IJUP2011 67info:eu-repo/semantics/publishedVersio