Estructuras geopolíticas en América Latina

Fil: James, Preston E.. Unión Geográfica Internaciona

The Role of the Plastic Industry in Industrial Arts Education

Statement of the Problem The purpose of this study was to determine the historical development and scope of the plastics industry. It was also ascertained in this study how the plastics industry could be interpreted in industrial arts education programs. Method of Study Used A review of available literature was made to identify the history and scope of the plastics industry, processes, products, type and cost of equipment, and the availability of visual aids to be used in teaching industrial plastics. Results Industrial processes applicable to industrial arts education have been described in this study. Also, a course of study for industrial plastics has been developed for all industrial arts education programs. Conclusion It was concluded by this study that the plastics industry has had a major significance on society. Therefore, it is necessary that all youth be acquainted with it in industrial arts education

Ferrets exclusively synthesize Neu5Ac and express naturally humanized influenza A virus receptors

Mammals express the sialic acids ​N-acetylneuraminic acid (​Neu5Ac) and ​N-glycolylneuraminic acid (​Neu5Gc) on cell surfaces, where they act as receptors for pathogens, including influenza A virus (IAV). ​Neu5Gc is synthesized from ​Neu5Ac by the enzyme cytidine monophosphate-N-acetylneuraminic acid hydroxylase (CMAH). In humans, this enzyme is inactive and only ​Neu5Ac is produced. Ferrets are susceptible to human-adapted IAV strains and have been the dominant animal model for IAV studies. Here we show that ferrets, like humans, do not synthesize ​Neu5Gc. Genomic analysis reveals an ancient, nine-exon deletion in the ferret CMAH gene that is shared by the Pinnipedia and Musteloidia members of the Carnivora. Interactions between two human strains of IAV with the sialyllactose receptor (sialic acid—α2,6Gal) confirm that the type of terminal sialic acid contributes significantly to IAV receptor specificity. Our results indicate that exclusive expression of ​Neu5Ac contributes to the susceptibility of ferrets to human-adapted IAV strains

Cerebrovascular events and outcomes in hospitalized patients with COVID-19: The SVIN COVID-19 Multinational Registry

Background Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) has been associated with a significant risk of thrombotic events in critically ill patients. Aim To summarize the findings of a multinational observational cohort of patients with SARS-CoV-2 and cerebrovascular disease. Methods Retrospective observational cohort of consecutive adults evaluated in the emergency department and/or admitted with coronavirus disease 2019 (COVID-19) across 31 hospitals in four countries (1 February 2020–16 June 2020). The primary outcome was the incidence rate of cerebrovascular events, inclusive of acute ischemic stroke, intracranial hemorrhages (ICH), and cortical vein and/or sinus thrombosis (CVST). Results Of the 14,483 patients with laboratory-confirmed SARS-CoV-2, 172 were diagnosed with an acute cerebrovascular event (1.13% of cohort; 1130/100,000 patients, 95%CI 970–1320/100,000), 68/171 (40.5%) were female and 96/172 (55.8%) were between the ages 60 and 79 years. Of these, 156 had acute ischemic stroke (1.08%; 1080/100,000 95%CI 920–1260/100,000), 28 ICH (0.19%; 190/100,000 95%CI 130–280/100,000), and 3 with CVST (0.02%; 20/100,000, 95%CI 4–60/100,000). The in-hospital mortality rate for SARS-CoV-2-associated stroke was 38.1% and for ICH 58.3%. After adjusting for clustering by site and age, baseline stroke severity, and all predictors of in-hospital mortality found in univariate regression (p \u3c 0.1: male sex, tobacco use, arrival by emergency medical services, lower platelet and lymphocyte counts, and intracranial occlusion), cryptogenic stroke mechanism (aOR 5.01, 95%CI 1.63–15.44, p \u3c 0.01), older age (aOR 1.78, 95%CI 1.07–2.94, p = 0.03), and lower lymphocyte count on admission (aOR 0.58, 95%CI 0.34–0.98, p = 0.04) were the only independent predictors of mortality among patients with stroke and COVID-19. Conclusions COVID-19 is associated with a small but significant risk of clinically relevant cerebrovascular events, particularly ischemic stroke. The mortality rate is high for COVID-19-associated cerebrovascular complications; therefore, aggressive monitoring and early intervention should be pursued to mitigate poor outcomes

Exploiting the labile site in dinuclear [Pd2L2]n+ metallo-cycles: multi-step control over binding affinity without alteration of core host structure

While Nature often controls supramolecular processes through regulation giving multiple levels of activity, synthetic metallosupramolecular systems have generally been binary (e.g. on/off) when they have control over molecular recognition events, and have often relied upon drastic chemical transformations or complete disassembly to enforce this control. We report here a new low symmetry ligand with a bidentate and a monodentate site (L). In combination with Pd2+, this ligand forms a [2 + 2] metallo-macrocycle, [Pd2L2L′2]n+, where L′ is the monodentate ancillary ligand that occupies the fourth and final coordination site of the metal ions. This assembly is structurally simple, but displays nuanced, multi-step binding affinity toward a neutral diplatinate guest employed for proof-of-concept. This complexity is introduced through varying the identity of L′, which can either be solvent (DMSO) or the halides chloride, bromide or iodide. The identity of L′ alters the cationic charge of the complex (neutral DMSO versus monoanionic halides) or otherwise influences the electron deficiency of the binding site of the host through varied strength of halide-ligand intra-molecular hydrogen bonding. Cycling between these different complexes was demonstrated, except for L′ = chloride which is non-reversible. This system therefore is able to interact with a platinate guest with four different graduations of affinity in response to stimuli, while still retaining the same simple core cationic structure. In addition to multi-setting binding affinity, we believe this is the first example of the use of variable intramolecular hydrogen bonding strength in switchable ancillary ligands to alter the electronic character and hence the π-π recognition characteristics of a metallosupramolecular host.DP would like to thank the ARC for a DECRA Fellowship, and the Royal Society of New Zealand for a Rutherford Postdoctoral Fellowship. BH would like to gratefully acknowledge the MBIE Catalyst Fund for a PhD scholarship. RV would like to thank the University of Otago for a PhD scholarship. The authors would like to thank the Australia National University, the University of Canterbury, the University of Otago, and the MacDiarmid Institute for additional funding. The authors acknowledge the contribution of the NeSI high performance computing facilities to the results of this research. New Zealand’s national facilities are provided by the New Zealand eScience Infrastructure and funded jointly by NeSI’s collaborator institutions and through the Ministry of Business, Innovation & Employment’s Research Infrastructure program. https://www.nesi.org.nz

The propagation of uncertainties in stellar population synthesis modeling I: The relevance of uncertain aspects of stellar evolution and the IMF to the derived physical properties of galaxies

The stellar masses, mean ages, metallicities, and star formation histories of galaxies are now commonly estimated via stellar population synthesis (SPS) techniques. SPS relies on stellar evolution calculations from the main sequence to stellar death, stellar spectral libraries, phenomenological dust models, and stellar initial mass functions (IMFs). The present work is the first in a series that explores the impact of uncertainties in key phases of stellar evolution and the IMF on the derived physical properties of galaxies and the expected luminosity evolution for a passively evolving set of stars. A Monte-Carlo Markov-Chain approach is taken to fit near-UV through near-IR photometry of a representative sample of low- and high-redshift galaxies with this new SPS model. Significant results include the following: 1) including uncertainties in stellar evolution, stellar masses at z~0 carry errors of ~0.3 dex at 95% CL with little dependence on luminosity or color, while at z~2, the masses of bright red galaxies are uncertain at the ~0.6 dex level; 2) either current stellar evolution models, current observational stellar libraries, or both, do not adequately characterize the metallicity-dependence of the thermally-pulsating asymptotic giant branch phase; 3) conservative estimates on the uncertainty of the slope of the IMF in the solar neighborhood imply that luminosity evolution per unit redshift is uncertain at the ~0.4 mag level in the K-band, which is a substantial source of uncertainty for interpreting the evolution of galaxy populations across time; 4) The more plausible assumption of a distribution of stellar metallicities, rather than a fixed value as is usually assumed, can have significant effects on the interpretation of colors blueward of the V-band. (ABRIDGED)Comment: 21 pages, 17 figures, ApJ in pres

The propagation of uncertainties in stellar population synthesis modeling III: model calibration, comparison, and evaluation

Stellar population synthesis (SPS) provides the link between the stellar and dust content of galaxies and their observed spectral energy distributions. In the present work we perform a comprehensive calibration of our own flexible SPS (FSPS) model against a suite of data. Several public SPS models are intercompared, including the models of Bruzual & Charlot (BC03), Maraston (M05) and FSPS. The relative strengths and weaknesses of these models are evaluated, with the following conclusions: 1) The FSPS and BC03 models compare favorably with MC data at all ages, whereas M05 colors are too red and the age-dependence is incorrect; 2) All models yield similar optical and near-IR colors for old metal-poor systems, and yet they all provide poor fits to the integrated J-K and V-K colors of both MW and M31 star clusters; 4) All models predict ugr colors too red, D4000 strengths too strong and Hdelta strengths too weak compared to massive red sequence galaxies, under the assumption that such galaxies are composed solely of old metal-rich stars; 5) FSPS and, to a lesser extent, BC03 can reproduce the optical and near-IR colors of post-starburst galaxies, while M05 cannot. Reasons for these discrepancies are explored. The failure at predicting the ugr colors, D4000, and Hdelta strengths can be explained by some combination of a minority population of metal-poor stars, young stars, blue straggler and/or blue horizontal branch stars, but not by appealing to inadequacies in either theoretical stellar atmospheres or canonical evolutionary phases (e.g., the main sequence turn-off). We emphasize that due to a lack of calibrating star cluster data in regions of the metallicity-age plane relevant for galaxies, all of these models continue to suffer from serious uncertainties that are difficult to quantify. (ABRIDGED)Comment: 26 pages, 16 figures, submitted to ApJ. The FSPS code can be downloaded at http://www.astro.princeton.edu/~cconroy/SPS