Towards Supramolecular Catalysis with Small Self-assembled Peptides

Self-assembly of small peptides offers unique opportunities for the bottom-up construction of supramolecular catalysts that aim to emulate the efficiency and selectivity of natural enzymes. Small, information-rich, simple molecules based on amino acids can self-organise autonomously into complex systems with emergent catalytic properties. The power of noncovalent interactions can be used to construct supramolecular peptidic tertiary structures. Moreover, specific functional groups present in amino acid side-chains may present either a catalytic activity by themselves or be able to bind cofactors such as metal ions. In this scenario, although relevant progress has been achieved in recent years, promising applications in biomaterials science are foreseen. In this review, we discuss the state-of-the-art of this approach at the interface between supramolecular chemistry and peptide science.     

Development of Novel Iron Crosslinked CMC Nanoadsorbents for the Remediation of Arsenic Ions

Iron crosslinked carboxy methyl cellulose (CMC) nanoparticles prepared by the process of emulsion crosslinking were studied for the removal of arsenic(V) ions from aqueous solution. Batch and column studies were conducted in order to investigate the efficiency of nanoparticles towards arsenic remediation. The Langmuir and Freundlich equations were applied to describe the biosorption isotherm. The results obtained from fixed bed studies showed that the column demonstrates fairly well at lowest flow rate and also, bed exhaustion time was found to increase with increasing bed height. The bed depth service time (BDST) model was used to analyze the experimental data and the model parameters were evaluated. Antibacterial studies were also conducted which confirms that Fe-CMC nanoparticles are efficient towards the removal of bacteriological contamination also.     

The Einstein relation in nanostructured materials: simplified theory and suggestion for experimental determination

An attempt is made to study the Einstein relation for the diffusivity–mobility ratio (DMR) in quantum wells (QWs) and quantum well wires (QWWs) of tetragonal compounds on the basis of a newly formulated electron energy spectrum taking into account the combined influences of the anisotropies in effective electron mass, the spin–orbit splitting, and the presence of crystal field splitting, respectively. The results for quantum-confined III–V compounds form a special case of our generalized analysis. The DMR has also been studied for QWs and QWWs of II–VI and IV–VI materials. Taking QWs and QWWs of CdGeAs₂, InAs, CdS and PbSe as examples, it was found that the DMR increases with increasing carrier statistics and decreasing film thickness respectively in various oscillatory manners emphasizing the influence of dimensional quantizations and the energy band constants in different cases. An experimental method of determining the DMR in nanostructures with arbitrary dispersion laws has also been suggested and the present simplified analysis is in agreement with the suggested relationship. The well-known results for nanostructures with parabolic energy bands have also been obtained as special cases from this generalized analysis under certain limiting conditions.     

Electric field effect on metallic particle contamination in a common enclosure gas insulated busduct

Sulphur hexaflouride (SF₆) is generally found to be very sensitive to field perturbations such as those caused by conductor surface imperfections and by conducting particle contaminants. A study of CIGRE group suggests that 20% of failures in gas insulated substations (GIS) is due to the existence of various metallic contaminations in the form of loose particles. The presence of contamination can therefore be a problem with gas-insulated substations operating at high fields. If the effects of these particles could be eliminated, then this would improve the reliability of compressed gas insulated substation. It would also offer the possibility of operating at higher fields to affect a potential reduction in the GIS size with subsequent savings in the cost of manufacture and installation. The purpose of this paper is to develop techniques, which will formulate the basic equations that will govern the movement of metallic particles like aluminum and copper in a bus duct. The simulation considers the electric field effect on particle movement and the results have been presented and analyzed     

Elastic Scattering Spectroscopy as a Diagnostic Tool for Apoptosis in Cell Cultures

Apoptosis, ldquoprogrammed cell death,rdquo is a cellular process exhibiting distinct biochemical and morphological changes. There is much interest regarding the role of apoptosis in cancer and the response to cancer treatment. Although apoptosis can occur spontaneously in malignant tumors and often significantly retards their growth, the initial response to successful cancer treatment is often massive apoptosis. In typical in vitro studies, current apoptosis detection methods require cell culture disruption via fixation, trypsinization, and/or staining. Our aim is to develop a nondisruptive optical method of detecting and tracking apoptosis in living cells and tissues, initially focusing on cell cultures. Such a method would allow for real-time evaluation of apoptotic progression of the same cell culture over time without perturbation or alteration. We report initial studies on the use of in vitro elastic scattering spectroscopy (ESS) to monitor changes in light-scattering properties of cells due to apoptotic morphology changes. For a sequence of times post treatment, we have measured the angle-dependent scattering at a single wavelength and also the wavelength-dependent scattering at discrete angles, of treated and control cell cultures. A novel polar nephelometer, developed in our laboratory, was used to obtain the angle-dependent scattering for the range of 90-145. Wavelength-dependent ESS measurements were made with a spectrometer, for several discrete near-forward angles. The results indicate that light scattering measurements can reliably discriminate between treated and control cells, correlating well with benchmark assays for apoptosis.     

Transient performance of a single-phase self-regulated self-excited induction generator using a three-phase machine

This paper presents the transient behavior of a three-phase star connected self-excited induction generator (SEIG) using three capacitors connected in series and parallel with a single-phase load. The voltage regulation of this generator is very small due to the effect of three capacitors. The dynamic model of the above generator has been developed based on stationary reference frame d–q-axes theory incorporating the effect of cross-saturation. The steady-state model of the scheme has also been developed. The simulated results of both the transient analysis for the different dynamic conditions, such as initiation of self-excitation, load perturbation and short-circuit and the steady-state analysis are compared with the experimental results. Both the simulated and experimental results are in close agreement with each other.     

适用于长距离输电网络的通用电压崩溃指标

首先提出一个广义电压崩溃指标（Generalized Voltage Collapse Index,缩写为GVCI）,定义为含有大容抗的长距离辐射型输电系统（架空线或海底电缆）距离最大稳定极限负荷的当前负荷裕度．GVCI为瞬时值,可用于保护和控制装置的整定,通过相量测量单元（PMU）所提供的局部测量值实现控制和保护功能．用一个简单的两母线双回线系统对所提出的GVCI指标的有效性进行了测试,通过扩展GVCI,用解析方式分析有载调压变压器（OLTC）的运行对电压崩溃的影响;并将GVCI与分析电压崩溃时常用的L指标进行了比较,讨论GVCI在地理位置偏远的风力发电场的可能应用．     

Separation of hematite from banded hematite jasper (BHJ) by magnetic coating

The separation of iron oxide from banded hematite jasper(BHJ) assaying 47.8% Fe, 25.6% Si O2 and 2.30%Al2O3 using selective magnetic coating was studied. Characterization studies of the low grade ore indicate that besides hematite and goethite,jasper, a microcrystalline form of quartzite, is the major impurity associated with this ore. Beneficiation by conventional magnetic separation technique could yield a magnetic concentrate containing 60.8% Fe with 51% Fe recovery. In order to enhance the recovery of the iron oxide minerals, fine magnetite, colloidal magnetite and oleate colloidal magnetite were used as the coating material. When subjected to magnetic separation, the coated ore produces an iron concentrate containing 60.2% Fe with an enhanced recovery of56%. The AFM studies indicate that the coagulation of hematite particles with the oleate colloidal magnetite facilitates the higher recovery of iron particles from the low grade BHJ iron ore under appropriate conditions.     

Failure analysis of titanium alloy (Ti6Al4V) fastener used in aerospace application

Titanium alloy fasteners are being used in space programme. These fasteners are coated with MoS₂, which serves the purpose of solid lubricant. During the trial assembly of flight spin motor to the bracket mounted on subsystem, one of the two fasteners failed such that the head of the bolt had sheared off the shank. Metallographic analysis carried out on the failed fasteners revealed variations in the microstructures all along the shank axis. Microstructure consisted of equiaxed primary alpha in transformed beta matrix within lower portion of the shank, while it was elongated primary alpha with little bulging all along prior beta grain boundaries as well as acicular alpha at some other location towards the head side, features, typical of, as if worked above beta transus temperatures.This paper highlights the details of investigations carried out on the failed fasteners.