Crystal structure and anisotropy of iodine-intercalated Bi2Sr2Can?1CunOx

The electronic state and structural configuration of the intercalated iodine species in stage-1, I-Bi₂Sr₂Ca _n–1Cu _n O _x (n = l, 2), have been studied through polarization-resolved Raman and¹²⁹I Mössbauer spectroscopy. The polarization dependence of the Raman spectra and the Mössbauer measurement confirmed the dominant species to be triiodide ions, I ₃ ^– , with alignment of these linear molecules either along thea- orb-axis in the host crystals. Transport measurements such as thermoelectric power and Hall coefficient clearly indicated that hole carriers are doped into the CuO₂ planes upon intercalation, by whichT _c of the host superconductor is changed. Furthermore, based on resistivity measurements in a magnetic field, we suggest that the iodine intercalation leads to a decrease of the anisotropy both in normal and superconducting states, suppressing the extremely two-dimensional character of the Bi₂Sr₂Ca _n–1Cu _n O _x systems.     

The role of the surveyor

The surveyor provides guidance and assistance for cargo protection, besides ensuring that the palm, palm kernel and coconut oils conform to the contractual requirements. This involves quality and quantity check, inspection of storage facilities, conveying systems and transport vehicles and supervision of loading and discharge operations. Usually, the surveyor’s findings form the basis for settlement of the transaction. With the ever-developing technology customer requirements have become more and more sophisticated, and consequently the need for complex and sophisticated service is considerably increasing. In order to achieve the desired objective the surveyor, besides being neutral and reliable, must be endowed with adequate technical know-how and facilities. There are quite a few pitfalls that can occur during the course of manufacture, handling, transportation, transfer points, etc., and in order to prevent them, the surveyor should conduct a series of checks at various points to ensure that the quality of the oil is not affected. Adequate precautions and timely corrective measures would evidently ensure this requirement. Quality check is equally essential, with need for a well-equipped testing laboratory with accurate instruments, controlled and managed by adequately qualified and experienced chemists with the knowledge of updated technology. The surveyor can also assist in arbitration, insurance claims, general, commercial and maritime information, as his opinions and recommendations are unbiased, reliable and accurate, which helps make decision-making a less difficult task. Besides the buyer and seller, the surveyor also protects the interests of the financier, under-writer, shipowners and in certain cases the government departments.     

The occurrence of a furanoid fatty acid inHevea brasiliensis latex

Methyl esters from the triglyceride fraction of the neutral lipids of natural rubber latex were found by gas liquid chromatography to contain about 90% of a furanoid acid. Spectroscopic analysis identified the acid as 10,13-epoxy-11-methyloctadeca-10,12-dienoic acid.     

Ultrasonic assessment of early-age changes in the material properties of cementitious materials

After casting, cementitious materials exhibit a continuous change in the mechanical properties with time due to a chemical reaction known as hydration. In addition, these materials also exhibit a change in state, from a fluid to a solid, in the first few hours. Conventionally, changes in the material properties are obtained by monitoring the visco-elastic moduli with time before setting and the increase in the elastic material properties of the solid cementitious material, after setting. An ultrasonic test setup and the data analysis procedures, which provide for continuous monitoring of the hydrating cementitious materials from a very early age through setting are presented in this paper. The test procedures for obtaining the ultrasonic test data and the inversion subroutines for assessing the material properties of the cementitious material at different stages of hydration are discussed. The experimental test results obtained from mortar mixtures of varying compositions are presented. The observed experimental trends are explained considering wave propagation in visco-elastic materials. There is a two-stage increase in the value of shear modulus of mortar with time. Experimental evidence suggests that initially there is a larger relative increase in the viscous component of the shear modulus while later there is a larger relative increase in the elastic component.     

Analysis of Scaling and Instability in FRP-Concrete Shear Debonding for Beam-Strengthening Applications

The debonding mode of failure, which is observed in girders strengthened using externally attached fiber-reinforced polymer (FRP) sheets, is studied in this paper. A numerical analysis of the direct-shear response of FRP attached to concrete substrate is performed to study the initiation, formation, and propagation of an interfacial crack between the two adherents. The material response of the bimaterial interface, which includes postpeak softening, is incorporated into the numerical model. The load response obtained numerically is shown to be in close agreement with that determined experimentally from direct shear tests on concrete blocks strengthened with FRP sheets. An instability in the load response is predicted close to failure and the arc-length method is used to obtain the entire load response past the displacement-limit point. The instability in the load response is shown to be a result of snapback, where both the load and the displacement decrease simultaneously. The effect of the bonded length on the stress transfer between the FRP and concrete and on the ultimate failure is also analyzed. It is shown that there is a scaling in the load capacity when the bonded length does not allow for the establishment of the full stress-transfer zone associated with interface crack growth. From the results of the numerical analysis, a fundamental understanding of interfacial crack propagation and instability at failure in concrete members strengthened using externally bonded FRP is developed. Using a simple energy based formulation; it is shown that in strengthened girders, the instability at complete debonding of FRP from concrete translates into an explosive failure associated with a sudden release of energy.     

Maintenance-outsourcing contracts for a system with backup machines

In this paper, we consider a system with multiple components, each prone to failure, during which production is halted. Minimal repair is performed by an external contractor whenever a component breaks down. The contractor also conducts a general preventive maintenance (PM) for the whole system at pre-determined times. The contractor’s goal is to minimise maintenance-related costs; however, the system (made up of the contractor and the manufacturer, who gains revenue whenever the system is up) profit would be maximised if the revenue is also considered. Since these goals usually require different PM schedules, we propose a cost subsidisation scheme which coordinates the system. We then extend this basic model by considering the existence of a backup machine which will allow the system to continue running (albeit, generating a lower revenue) whenever a component fails. We show that the existence of such a machine reduces the profit difference between uncoordinated and coordinated systems.     

Direct observation of nanomechanical properties of chromatin in living cells

Precise manipulation of nanometer-sized magnetic particles using magnetic tweezers has yielded insights into the rheology of the cell cytoplasm. We present first results using this approach to study the nanomechanics of the cell nucleus. Using a custom-designed micro-magnetic-tweezers instrument, we can achieve sufficiently high magnetic forces enabling the application and measurement of controlled distortion of the internal nuclear structure on the nanometer scale. We precisely measure the elasticity and viscosity inside the nucleus of living HeLa cells. The high value of the Young's modulus (Y = 2.5 x 10(2) Pa) measured relative to the cytoplasm is explained by a large-scale model for in vivo chromatin structure using a polymer network model.     

Carbon nanotubes grown on stainless steel to form plate and probe electrodes for chemical/biological sensing

This paper describes the fabrication and evaluation of carbon nanotube (CNT) electrodes grown on stainless steel (SS) plate and wire for electrochemical sensor applications. Multi-wall carbon nanotubes with different diameters were grown on the SS plate and wire by chemical vapor deposition from an ethylene precursor. The SS provides a good electrical and mechanical connection to the CNT, and the SS is a tough substrate. The SS part of the electrode was electrically insulated from the analyte so that only the CNT were active in sensing. Cyclic voltammetry for the reduction of 6 mM K3Fe(CN)6 in a 1.0 M KNO3 supporting electrolyte was performed to examine the redox behavior of the CNT-SS electrode. The cyclic voltammograms showed sigmoidal-like shapes, indicating that mass transport around the electrodes is dominated by radial diffusion. Based on the cyclic voltammograms, the effective area of the CNT-SS electrodes and the number of individual CNTs were estimated. These results indicate that the CNT-SS plate and wire electrodes are good candidates to develop practical in vivo biosensors.     

Strategies for patterning biomolecules with dip-pen nanolithography

Dip-pen nanolithography (DPN) is an atomic force microscopy (AFM)-based lithography technique, which has the ability to fabricate patterns with a feature size down to approximately 15 nm using both top-down and bottom-up approaches. DPN utilizes the water meniscus formed between an AFM tip and a substrate to transfer ink molecules onto surfaces. A major application of this technique is the fabrication of micro- and nano-arrays of patterned biomolecules. To achieve this goal, a variety of chemical approaches has been used. This review concisely describes the development of DPN in the past decade and presents the related chemical strategies that have been reported to fabricate biomolecular patterns with DPN at micrometer and nanometer scale, classified into direct- and indirect DPN methodologies, discussing tip-functionalization strategies as well.