Shape optimization for a composite crack-length sensor

Conductive polymeric sensors can be used as crack-length gages. They have the advantages of being inexpensive, versatile in size and require inexpensive instrumentation. They also measure crack length continuously. The shape of these gages can be varied in several ways to improve their sensitivity. The gages with the 'optimized' or tapered shape overcome the principal disadvantages of rectangular gages, namely poor sensitivity at small crack lengths.     

An investigation of the losipescu and asymmetrical four-point bend tests

The Iosipescu shear test, utilizing a notched specimen in bending and a modification—the asymmetrical four-point bend (AFPB) test—were evaluated as shear tests for composites. This paper summarizes the results of an extensive numerical and experimental investigation of the Iosipescu and AFPB test methods. Finite-element analyses were conducted to assess the influence of notch parameters and load locations on the stress state in the specimen. The shear moduli and the shear strengths were experimentally measured for a quasiisotropic graphite/epoxy laminate using both the Iosipescu and the AFPB test methods. The tests were conducted for various combinations of notch parameters and load locations. The test results indicate that changes in the notch geometry and load locations aimed at improving the stress distribution in the test section resulted in unexpected changes in the failure mode. Paper was presented at the 1985 SEM Spring Conference on Experimental Mechanics held in Las Vegas, NV on June 9–14.     

Shifting of Fluorescence Peak in CdS Nanoparticles by Excitation Wavelength Change

CdS nanoparticles with different size are prepared by chemical bath deposition method. These particles show strong fluorescence at emission wavelength of 507 nm. It has been observed that this emission peak changes through a range of 147 nm, by varying the excitation wavelengths through 370–480 nm.The emission peak can thus be tuned by varying the excitation wavelengths. This peak emission wavelength shift is due to the selective excitation of vibronic levels in the surface state of the CdS nanoparticles.     

Catalyst-free synthesis of 3-substituted-3-hydroxy-2-oxindoles by reaction of isatin and cyclic enaminone in water

An easy protocol for the synthesis of enaminone attached 3-substituted-3-hydroxy-2-oxindoles has been demonstrated by reaction of isatin and cyclic enaminone in water. The developed catalyst-free reaction has the advantage of being atom-economical, eco-friendly, and benign reaction conditions. The broader substrate scope, experimentally simple procedures, and easy purification of products with high yield further make this method attractive and useful.     

Effect of chlorine on the adsorption of oxygen on Cu and Ag surfaces

Based on XPS and UVPS studies, it is shown that oxygen is preferentially adsorbed molecularly in the singlet state on Cu and Ag surfaces containing presorbed chlorine. Adsorption of chlorine on Cu and Ag surfaces containing presorbed atomic oxygen causes a disappearance of the oxygen. Extended Hückel calculations predict the observed behaviour.     

Nanoparticle-induced multi-functionalization of silicon: A plug and play approach

Here, we demonstrate a “plug and play” approach to achieve multi-functionalization of Si. In this approach, externally synthesized functional nanoparticles are introduced onto device quality Si wafers and the surface chemical bonds are manipulated. Sonochemically synthesized Fe₂O₃ nanoparticles are introduced onto Si from an alcohol suspension. On annealing this sample in ultra-high vacuum, the oxygen atoms change the bonding partner from Fe to Si and desorb as SiO at 750 °C. This results in the formation of nanoparticles of Fe on the surface and exhibits ferromagnetic behavior. Deposition of a thin layer (2 nm) of Si onto the sample containing the metallic Fe nanoparticles followed by annealing at 560 °C leads to optically active Si. Photoluminescence measurements show that this sample emits light at three different wavelengths, namely 1.57, 1.61 and 1.63 μm, when excited by He–Ne or Ar lasers. Oxidation of this material results in the formation of a selective capping layer of SiO₂. Thus we obtain multi-functional Si in an “all in one” form and we believe that this approach is universal.     

Facile synthesis of mosquitocidal silver nanoparticles using Mussaenda glabra leaf extract: characterisation and impact on non-target aquatic organisms

Plant-borne compounds have been proposed for extracellular synthesis of mosquitocidal nanoparticles. However, their impact against mosquito natural enemies has been scarcely studied. Here, we synthesised silver nanoparticles (Ag NPs) using Mussaenda glabra leaf extract as reducing and stabilising agent. Biofabricated Ag NPs were characterised by UV–vis spectrophotometry, X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Compared to the leaf aqueous extract, biosynthesised Ag NPs showed higher toxicity against mosquito vectors Anopheles subpictus, Aedes albopictus and Culex tritaeniorhynchus with LC₅₀ of 17–19 μg/mL, respectively. Ag NPs were found safer to non-target organisms Diplonychus indicus and Gambusia affinis, with respective LC₅₀ values ranging from 1446 to 8628 μg/mL. Overall, M. glabra-fabricated Ag NPs are a promising and eco-friendly tool against larval populations of mosquito vectors of medical and veterinary importance, with negligible toxicity against other non-target aquatic organisms.     

Carbohydrate-Derived Dienes as Building Blocks for Pharmaceutically Relevant Molecules

Carbohydrate-based dienes are valuable building blocks for a variety of highly functionalized carbo- and oxa-cycles by virtue of their high degree of inherent stereochemical information, and suitability in various synthetic transformations. Research into the chemistry of carbohydrate-based dienes has been expanding over the last decades due to its unique applications in the construction of diverse and complex structural frameworks. In this review, we describe the main transformations of this interesting class of molecule and highlight their utility in the construction of diverse ring systems important for drug development.