The rate at which energy decays in a viscously damped hinged Euler–Bernoulli beam

We study the best decay rate of the solutions of a damped Euler–Bernoulli beam equation with a homogeneous Dirichlet boundary conditions. We show that the fastest decay rate is given by the supremum of the real part of the spectrum of the infinitesimal generator of the underlying semigroup, if the damping coefficient is in L^∞(0,1)$L^{\infty }(0,1)$.     

Nonionic Surfactants from Recycled Poly(ethylene terephthalate) as Corrosion Inhibitors of Steel in 1 M HCl

Recycled poly(ethylene terephthalate) (PET) can be modified to produce nonionic surfactants. Recycling of PET waste was carried out in presence of triethanolamine and manganese acetate as catalyst. The produced oligomers were reacted with stearic acid and polyethylene glycol, PEG, which have different molecular weights 400, 1,000, and 4,000. The inhibition of corrosion of steel in 1 molar hydrochloric acid solution in the presence of the prepared surfactants is studied by weight loss and electrochemical polarization measurements. The polarization curves indicate that these compounds act as mixed‐type inhibitors. The inhibition efficiency increases with the increase of inhibitor concentration to reach their critical micelle concentrations. The temperature effect on the corrosion behavior of steel in 1 M HCl with and without surfactants is studied in the temperature range from 308 to 343 K. The adsorption of inhibitors on the steel surface is found to increase with increasing the temperature. From the adsorption isotherm, some thermodynamic data for the adsorption process are calculated and discussed.     

SYNTHESIS AND SOME REACTIONS OF 2-MERCAPTO-3,5,7-TRIPHENYLPYRIDO[2,3-d]-PYRIMIDINE-4(3H)-ONE

Abstract

2-Mercapto-3,5,7-triphenylpyrido[2,3-d]pyrimidine-4(3H)-one (II) was synthesized by the interaction of ethyl-2-amino-4,6-diphenylincotinate (I) with phenyl isothiocyanate in pyridine. The reaction of II with different reagents was carried out to give some condensed heterocyclic systems.     

Aptamers: Potential Diagnostic and Therapeutic Agents for Blood Diseases

Aptamers are RNA/DNA oligonucleotide molecules that specifically bind to a targeted complementary molecule. As potential recognition elements with promising diagnostic and therapeutic applications, aptamers, such as monoclonal antibodies, could provide many treatment and diagnostic options for blood diseases. Aptamers present several superior features over antibodies, including a simple in vitro selection and production, ease of modification and conjugation, high stability, and low immunogenicity. Emerging as promising alternatives to antibodies, aptamers could overcome the present limitations of monoclonal antibody therapy to provide novel diagnostic, therapeutic, and preventive treatments for blood diseases. Researchers in several biomedical areas, such as biomarker detection, diagnosis, imaging, and targeted therapy, have widely investigated aptamers, and several aptamers have been developed over the past two decades. One of these is the pegaptanib sodium injection, an aptamer-based therapeutic that functions as an anti-angiogenic medicine, and it is the first aptamer approved by the U.S. Food and Drug Administration (FDA) for therapeutic use. Several other aptamers are now in clinical trials. In this review, we highlight the current state of aptamers in the clinical trial program and introduce some promising aptamers currently in pre-clinical development for blood diseases.     

A Glossary for Chemical Approaches towards Unlocking the Trove of Metabolic Treasures in Actinomycetes

Actinobacterial natural products showed a critical basis for the discovery of new antibiotics as well as other lead secondary metabolites. Varied environmental and physiological signals touch the antibiotic machinery that faced a serious decline in the last decades. The reason was exposed by genomic sequencing data, which revealed that Actinomycetes harbor a large portion of silent biosynthetic gene clusters in their genomes that encrypt for secondary metabolites. These gene clusters are linked with a great reservoir of yet unknown molecules, and arranging them is considered a major challenge for biotechnology approaches. In the present paper, we discuss the recent strategies that have been taken to augment the yield of secondary metabolites via awakening these cryptic genes in Actinomycetes with emphasis on chemical signaling molecules used to induce the antibiotics biosynthesis. The rationale, types, applications and mechanisms are discussed in detail, to reveal the productive path for the unearthing of new metabolites, covering the literature until the end of 2020.     

Selenium Occurrence,Distribution and Speciation in the Cockle Anadara trapezia and the Mullet Mugil cephalus

Data on the factors affecting the accumulation of selenium in the cockle Anadara trapezia and mullet Mugil cephalus are presented, together with the distribution and speciation of selenium in tissues. Selenium concentration in whole cockles showed a small but significant decrease with weight. No further decrease in selenium concentration was apparent once an organism reached 0.25 g dry weight. Selenium concentration in cockles was not dependent on sex. The tissue distribution of selenium concentration in cockles was in the order gill>intestine>adductor>mantle >foot. Selenium concentrations in liver tissues of mullet increased with the whole weight of the fish. In contrast, selenium concentrations in muscle, stomach, heart and kidney tissues were fairly low and constant in fish weighing less than 200 g (20 cm in length). Fish of greater weight and size (>250 g and >30 cm) had higher and more variable selenium concentrations. No differences in selenium concentration between male and female fish occurred; however, the sex of many of the fish could not be distinguished. The tissue distribution of selenium concentration in mullet was in the order liver>stomach>heart>muscle>kidney. Most of the selenium recovered from both the cockle tissues and the mullet muscle tissues was found to be associated with proteins and to be present as selenocysteine. A conceptual model is presented for selenium transformations in marine organisms based on the formation of selenoamino-acids and subsequent incorporation into proteins. © 1997 by John Wiley & Sons, Ltd.     

Synthesis of some new spiroindoline derivatives incorporated with pyrazoloheterocycles

Indole-2,3-dione ( 1 ) was treated with malonic acid ( 2 ) in a mixture of ethanol/pyridine to afford 1-[3-(2-oxoindolinylidene)]acetic acid ( 3 ). Compound 3 reacted with thionyl chloride to give the corresponding acid chloride ( 4 ). The acid chloride 4 reacted with arenes in the presence of AlCl₃ to yield 3-(2-oxoindolinylidene)acetophenones 5a–c . Compounds 5a–c reacted with 3-methylpyrazolin-5-one derivatives 6a , b to give 3-aracyl-3-[4′-(3′-methylpyrazolin-5-onyl)]-indoline-2-one derivatives 7a–f . Compounds 7a–f were treated with phosphorus pentoxide in phosphoric acid, with ammonium acetate or methanolic methylamine and with phosphorus pentasulfide to give spiro[indoline-3,4′-(pyrazolo[4,5-b]pyran)]-2-ones 8a–f , spiro[indoline-3,4′-(pyrazolo[4,5-b]-dihydropyridine)]-2-ones 9a–f , 10a–f and spiro[indoline-3,4′-(pyrazolo[4,5-b]thiopyran)]-2-ones 10a–f , respectively. All of the synthesized spiroheterocycle derivatives were identified by conventional spectroscopic methods (IR, ¹H NMR) and elemental analyses. © John Wiley & Sons, Inc.