Effect of Wearing Surgical Face Masks on Gas Detection from Respiration Using Photoacoustic Spectroscopy

Wearing surgical face masks is among the measures taken to mitigate coronavirus disease (COVID-19) transmission and deaths. Lately, concern was expressed about the possibility that gases from respiration could build up in the mask over time, causing medical issues related to the respiratory system. In this research study, the carbon dioxide concentration and ethylene in the breathing zone were measured before and immediately after wearing surgical face masks using the photoacoustic spectroscopy method. From the determinations of this study, the C₂H₄ was established to be increased by 1.5% after one hour of wearing the surgical face mask, while CO₂ was established to be at a higher concentration of 1.2% after one hour of wearing the surgical face mask, when the values were correlated with the baseline (control).     

A single microcystin in a toxic Microcystis bloom from the river Río de la Plata (Argentina)

Microcystis is one of the most common bloom-forming cyanobacteria genera in diverse ecosystems. More than 80% of its strains are toxic, mainly due to their ability to produce metabolites known as microcystins (MC). Here we report on a M. aeruginosa bloom that appeared in the summer of 2001 at a site of the Río de la Plata, within the city of Buenos Aires. The symptoms in mice indicated that the bloom was hepatotoxic. LC-PDA analysis revealed a similar high concentration (0.9–1?mg?g^–1?d w) of just one MC in the bloom biomass during the 3-month study period. During this period most of the MC (ca. 98 %) was found intracellularly, and the content remained almost the same. The molecular mass of the bloom MC was 1036?Da, as deduced from LC-ESI-MS data. Fragment ion analysis by LC-IT-MS-MS allowed identifying 6 out of the 7 amino acids, as well as their position in the molecule. The molecular mass of the unidentified amino acid residue was 155?Da. According to the data obtained, the MC under study was MC-XR, X representing the unidentified amino acid. This is the first report both on the characterisation of MCs in an urban site of the Río de la Plata waters, and on an Argentinean bloom exhibiting only one MC variant.     

Structural and magnetic properties of pulsed laser deposited SrRuO3/CoFe2O4/La2/3Sr1/3MnO3 magnetic oxide heterostructures on SrTiO3(001) and MgO(001)

We report on the growth of all-oxide SrRuO₃/CoFe₂O₄/La_2/3Sr_1/3MnO₃ and La_2/3Sr_1/3MnO₃/CoFe₂O₄/SrRuO₃ heterostuctures on SrTiO₃(001) and MgO(001) substrates by pulsed laser deposition. Structural analyses by X-ray diffraction and transmission electron microscopy clearly indicate the preservation of epitaxial relations when the La_2/3Sr_1/3MnO₃ layer is grown first, whereas trilayers with SrRuO₃ at the bottom are more disordered. Both the substrate material and the deposition sequence strongly influence the formation of various structural defects such as interfacial dislocations and sub-grain structures, and this is clearly reflected by a reduction of the saturation magnetization in the top electrode. When the substrate material and the deposition sequence are correctly chosen, however, the magnetic moments of the La_2/3Sr_1/3MnO₃ and SrRuO₃ layers reverse independently, and the La_2/3Sr_1/3MnO₃ layer retains bulk-like magnetic properties.     

Experimental NMR and MS study of benzoylguanidines. Investigation of E/Z isomerism

Molecules containing the guanidinic nuclei possess several pharmacological applications, and knowing the preferred isomers of a potential drug is important to understand the way it operates pharmacologically. Benzoylguanidines were synthesized in satisfactory to good yields and characterized by NMR, Electrospray Ionization Mass Spectrometry (ESI‐MS) and Fourrier Transform InfraRed Spectroscopy techniques (FTIR). E/Z isomerism of the guanidines was studied and confirmed by NMR analysis in solution (¹H‐¹³C Heteronuclear Single Quantum Coherence (HSQC) and Heteronuclear Multiple‐Bond Correlation (HMBC), ¹H‐¹⁵N HMBC, ¹H‐¹H Correlation Spectroscopy (COSY) and Nuclear Overhauser Effect Spectroscopy (NOESY) experiments) at low temperatures. Compounds with p‐Cl and p‐Br aniline moiety exist mainly as Z isomer with a small proportion of E isomer, whereas compounds with p‐NO2 moiety showed a decrease in proportion of isomer Z. The results are important for the application of these molecules as enzymatic inhibitors. Copyright © 2013 John Wiley & Sons, Ltd.     

A brief review of the methods used to evaluate vapour pressures and sublimation enthalpies

A brief review of the experimental methods used to evaluate vapour pressures and sublimation enthalpies is presented. The methods discussed have been used for determining the results of several substituted benzenes that were collected in a database, with the main purpose of developing new estimation methods of these thermodynamic properties. A critical evaluation of the two most used calorimetric techniques for determining enthalpies of sublimation is also addressed.     

Hiv-1 Specific Reverse Transcriptase Inhibitors: why are Tsao-Nucleosides so Unique?

1. INTRODUCTION

AIDS will still be one of the most important challenges for the Scientific Community in the approaching new century. Since the identification, in 1983-84,^1,2 of human immunodeficiency virus (HIV) as the etiological agent of AIDS, significant progress has been made in the treatment of HIV-infected patients. This has been in part due to the discovery and clinical use of an increasing number of anti-HIV drugs. However, while highly active antiretroviral therapy (HAART)³ approaches have reduced the morbidity and mortality, the intertwined problems of drug induced viral resistance, poor compliance with complex regimens and therapy failure continue. Therefore, there remains a pressing need for the development of new antiviral agents that can be used not only as first line therapeutic candidates, but also in the antiretroviral-experienced patient population.     

Multivariate optimization of the Kharasch–Sosnovsky allylic oxidation of olefins

The multivariate optimization method known as simplex is applied to the Kharasch–Sosnovsky allylic oxidation of double bonds. By applying this method, the amounts of three variables (copper source, oxidant, and additive) are optimized at the same time. Under the conditions thus obtained the reaction takes place in a considerable shorter time, being the alkene the limiting reagent. These conditions are applied to some monoterpenes and sesquiterpenes leading regioselectively to the corresponding benzoate esters, opening a route to the employment of this reaction in the synthesis of more complex molecules.     

Water flows induced by microwave electric fields in microsystems

AC electric fields are of increasing importance for the generation of fluid flows in microsystems. We analyse numerically the use of AC electric fields at microwave frequencies for electro-thermal actuation of water in microdevices. Water is heated because of its significant dielectric loss at microwave frequencies. Buoyancy and dielectric forces actuate in the liquid bulk, and the relative importance between them is studied. The microwave liquid actuation can be used for pure water as well as for water saline solutions, such as bio-fluids. Therefore, it is of interest for the Lab-on-a-Chip technology.