Analysis of the Ordinary and Extraordinary Ionospheric Modes for NVIS Digital Communications Channels.

Sensor networks have become more popular in recent years, now featuring plenty of options and capabilities. Notwithstanding this, remote locations present many difficulties for their study and monitoring. High-frequency (HF) communications are presented as an alternative to satellite communications, being a low-cost and easy-to-deploy solution.

Hybrid Repair of Type B Aortic Dissection With Thoracoabdominal Aortic Aneurysmal Degeneration in the Setting of Marfan Syndrome.

Aneurysmal degeneration of the thoracoabdominal aorta after aortic dissection is a well-documented sequela of Marfan syndrome (MFS). Hybrid technique (HT), an emerging treatment modality for complex aortic pathologies, decreases morbidity and mortality relative to open surgery. However, outcome data regarding HT in genetic aortopathies such as MFS is limited.

Ureteral Arterial Fistula - A Role for Open Operation in the 21st Century.

Background: Ureteral arterial fistula is a rare and challenging clinical entity. The diagnosis and management of ureteral arterial fistula present a unique disease process that requires a dual specialty approach, involving both vascular and urologic surgeons. There are different options for repair, including both open and endovascular techniques.

NVIS Multicarrier Modulations for Remote-Sensor Applications.

The number of Internet of Things (IoT) devices has experienced a large growth during the last decade, as well as the data volume gathered from remote sensors. Satellites are still a suitable communication method and may be preferable for a remote ubiquitous sensor network (USN), which sometimes are located in places without much communications infrastructure where coverage is the principal drawback. Alternatively, the proposed solution for this article aims at a near-vertical incidence skywave (NVIS) channel for high frequencies (HF) with a low-cost platform, allowing a low-power transmissions coverage area up to 250 km for USN.

Direct Retrograde Bypass is Preferable to Antegrade Bypass for Open Mesenteric Revascularization.

Background: Mesenteric bypass grafts can be constructed either antegrade or retrograde. There is debate regarding which is the optimal approach. We have modified the technique for retrograde mesenteric revascularization using a direct open retrograde revascularization (DORR) technique.

Burn effects on soil properties associated to heat transfer under contrasting moisture content.

The aim of this work is to investigate the topsoil thickness affected by burning under contrasting soil moisture content (field capacity versus air-dried conditions). A mollic horizon of an Aleppo pine forest was sampled and burned in the laboratory, recording the temperature continuously at the topsoil surface and at soil depths of 1, 2, and 3cm. Changes in soil properties were measured at 0-1, 1-2, 2-3, and 3-4cm.

Straw management effects on CO2 efflux and C storage in different Mediterranean agricultural soils.

The crop residues buried in semiarid soils as a carbon sink are evaluated. Both C-CO2 evolved and C sequestered from agricultural soils amended with barley straw were measured seasonally over 2 farming seasons in a semiarid environment (NE Spain). Six experimental soils with low organic matter content and contrasted properties were selected.

An amine-catalyzed enantioselective [3+2] cycloaddition of azomethine ylides and α,β-unsaturated aldehydes: applications and mechanistic implications.

The catalytic enantioselective [3+2] cycloaddition between azomethine ylides and α,β-unsaturated aldehydes catalyzed by α,α-diphenylprolinol has been studied in detail. In particular, the reaction has been extended to the use of 2-alkenylidene aminomalonates generated in situ as azomethine ylide precursors. These reactions lead to the formation of pyrrolidines containing a 5-alkenyl side chain with potential for chemical manipulation.

Organocatalytic enantioselective synthesis of 2,3-dihydropyridazines.

We have developed an efficient procedure for the easy and straightforward preparation of functionalized dihydropyridazines as highly enantiopure materials by reaction of pyruvaldehyde 2-tosyl hydrazone with a variety of α,β-unsaturated aldehydes using a chiral secondary amine as catalyst. The overall process consists of a cascade reaction involving an initial aza-Michael reaction, in which the stereocentre is installed, followed by an intramolecular aldol reaction/dehydration step.

Organocatalytic enantioselective (3+2) cycloaddition using stable azomethine ylides.

We have developed a highly efficient procedure for carrying out the catalytic enantioselective (3+2) cycloaddition between enals and stable azomethine ylides such as isoquinolinium and phthalizinium methylides. Under the optimized reaction conditions highly substituted chiral pyrroloisoquinolines and pyrrolophthalazines have been obtained in high yields and excellent diastereo- and enantioselectivities.

Role of pseudoephedrine as chiral auxiliary in the "acetate-type" aldol reaction with chiral aldehydes; asymmetric synthesis of highly functionalized chiral building blocks.

We have studied in depth the aldol reaction between acetamide enolates and chiral α-heterosubstituted aldehydes using pseudoephedrine as chiral auxiliary under double stereodifferentiation conditions, showing that high diastereoselectivities can only be achieved under the matched combination of reagents and provided that the α-heteroatom-containing substituent of the chiral aldehyde is conveniently protected. Moreover, the obtained highly functionalized aldols have been employed as very useful starting materials for the stereocontrolled preparation of other interesting compounds and chiral building blocks such as pyrrolidines, indolizidines, and densely functionalized β-hydroxy and β-amino ketones using simple and high-yielding methodologies.

5-Mercaptotetrazoles as synthetic equivalents of nitrogen-containing functional groups. The case of the organocatalytic enantioselective aza-Michael reaction.

5-Mercaptotetrazoles have been identified as useful and versatile Michael donors in enantioselective amine-catalyzed aza-Michael reactions with α,β-unsaturated aldehydes, showing excellent behavior as N-nucleophiles instead of their usual trend to react as S-nucleophiles. In addition several unprecedented chemical modifications on the tetrazolothione moiety have been carried out leading to the enantioselective preparation of different compounds incorporating nitrogen-containing functionalities such as oxazinimines, formamidines, ureas and isoureas.

Understanding the toxicity of aggregated zero valent copper nanoparticles against Escherichia coli.

Copper nanoparticles are used in wide variety of applications and in the current study we report the antimicrobial activity of these particles. Influence of pH, temperature, aeration rate, concentration of nanoparticles and concentration of bacteria on the toxicity of copper nanoparticles against Escherichia coli have been studied using a centroid mixture design of experiment. The linear and quadratic regression model shows that the toxicity of copper nanoparticles not only depends on the primary effect of the parameters tested (pH, temperature, aeration, concentration of E.

The organocatalytic [3+2] cycloaddition of azomethine ylides and alpha,beta-unsaturated aldehydes as a convenient tool for the enantioselective synthesis of pyrrolizidines and indolizidines.

We have developed a simple and straightforward procedure for the enantioselective preparation of densely substituted bicyclic and tricyclic nitrogen heterocycles using conveniently substituted enantiopure pyrrolidines as common synthetic intermediates, which are easily accessible by our recently developed organocatalytic enantioselective [3+2] cycloaddition of alpha,beta-unsaturated aldehydes and azomethine ylides. The designed synthetic pathway makes use of a ring-closing metathesis reaction for building up the pyrrolizidine and indolizidine skeletons, while the access to the hexahydrocyclopenta[a]pyrrolizine structure has been carried out relying on a fully diastereoselective intramolecular Pauson-Khand reaction.

Optimization of the fermentation media for sophorolipid production from Candida bombicola ATCC 22214 using a simplex centroid design.

This article describes the use of a simplex centroid mixture experimental design to optimize the fermentation medium in the production of sophorolipids (SLs) using Candida bombicola. In the first stage, 16 media ingredients were screened for the ones that have the most positive influence on the SL production. The sixteen ingredients that were chosen are five different carbohydrates (fructose, glucose, glycerol, lactose, and sucrose), five different nitrogen sources (malt extract, peptone extract, soytone, urea, and yeast extract), two lipid sources (mineral oil and oleic acid), two phosphorus sources (K(2)HPO(4) and KH(2)PO(4)), MgSO(4), and CaCl(2).

Alkaline sucrose as a solvent for delivery of water-insoluble drugs.

Alkaline sucrose solution was demonstrated to be a good solvent for the solubilization of water-insoluble drugs. At high concentration and alkaline pH, sucrose solubilizes water-insoluble molecules through intramolecular conformations. Tetracyline and chloramphenicol, when dissolved in alkaline sucrose solution, retained their bactericidal activity.

Highly regio- and stereoselective addition of organolithium reagents to extended conjugate amides using (S,S)-(+)-pseudoephedrine as chiral auxiliary.

The conjugate addition of organolithium reagents to polyunsaturated conjugate amides containing (S,S)-(+)-pseudoephedrine as chiral auxiliary has been studied in detail. The reaction proceeded with good 1,4-selectivity and excellent stereoselectivity, affording the corresponding addition products with good yields and as highly diastereoenriched isomers. Removal of the chiral auxiliary by reduction or hydrolysis has allowed the preparation of polyfunctionalized chiral building blocks incorporating an alkene moiety suitable for further transformations.

Organocatalytic enantioselective synthesis of highly functionalized polysubstituted pyrrolidines.

The organocatalytic conjugate addition of different aldehydes to beta-nitroacrolein dimethyl acetal, generating the corresponding highly functionalized nitroaldehydes in high yields and with high stereoselectivities, has been studied in detail. These transformations have been achieved by using both readily available starting materials in a 1:1 ratio as well as commercially available catalysts at a 10 mol % catalyst loading. Furthermore, a very short and efficient protocol has been devised for the preparation of highly enantioenriched pyrrolidines containing two or three contiguous stereocenters starting from the obtained Michael adducts.

(S,S)-(+)-pseudoephedrine alpha-iminoglyoxylamide as a chiral glycine cation equivalent: a modular and flexible approach to enantioenriched alpha-amino ketones.

We have studied the ability of an alpha-imino glyoxylamide derived from (S, S)-(+)-pseudoephedrine as a valuable chiral electrophile for the preparation of alpha-amino carbonyl compounds. In this context, the addition of Grignard reagents to the azomethine moiety of this chiral electrophile afforded the expected alpha-amino amide adducts in good yields and diastereoselectivities. Moreover, these adducts have been transformed into enantioenriched alpha-amino ketones by exploiting the ability of pseudoephedrine amides to undergo selective monoaddition to the carbamoyl group with organolithium reagents.

Organocatalytic enantioselective aza-Michael reaction of nitrogen heterocycles and alpha,beta-unsaturated aldehydes.

The asymmetric organocatalytic aza-Michael reaction of several nitrogen heterocycles and alpha,beta-unsaturated aldehydes has been studied in detail; under the optimised conditions, the conjugate addition products have been obtained in high to excellent enantioselectivities.