Foliation of the Kottler–Schwarzschild–de Sitter spacetime by flat spacelike hypersurfaces

There exist Kruskal like coordinates for the Reissner–Nordstrom (RN) black hole spacetime which are regular at coordinate singularities. Non-existence of such coordinates for the extreme RN black hole spacetime has already been shown. Also the Carter coordinates available for the extreme case are not manifestly regular at the coordinate singularity, therefore, a numerical procedure was developed to obtain free fall geodesics and flat foliation for the extreme RN black hole spacetime. The Kottler–Schwarzschild–de Sitter (KSSdS) spacetime geometry is similar to the RN geometry in the sense that, like the RN case, there exist non-singular coordinates when there are two distinct coordinate singularities. There are no manifestly regular coordinates for the extreme KSSdS case. In this paper foliation of all the cases of the KSSdS spacetime by flat spacelike hypersurfaces is obtained by introducing a non-singular time coordinate.     

Thermal tunability in terahertz metamaterials fabricated on strontium titanate single-crystal substrates

We report an experimental demonstration of thermal tuning of resonance frequency in a planar terahertz metamaterial consisting of a gold split-ring resonator array fabricated on a bulk single-crystal strontium titanate (SrTiO?) substrate. Cooling the metamaterial starting from 409 K down to 150 K causes about a 43% shift in resonance frequency, and there is very little variation in resonance strength. The resonance shift is due to the temperature-dependent dielectric constant of the strontium titanate. The experiment opens up avenues for designing tunable terahertz devices by exploiting the temperature-sensitive characteristic of high dielectric constant substrates and complex metal oxide materials.     

Precursor Routes to Semiconductor Quantum Dots

Abstract

Quantum Dots are unique for two very important reasons both of which can potentially be commercially exploited: ? The electronic and optical properties of Quantum Dots are dependent on the particle size.

? As the Quantum Dot nanoparticle becomes smaller the ratio of the number of surface atoms to those in the interior increase. For example in very small particles greater than a third of all atoms reside on the surface. Such a high surface area is useful for catalysis.

The solutions to the right all contain the same semiconductor material (cadmium selenide, CdSe) but are different colours because unlike the bulk material, which is black, we have controlled the size and therefore the electronic and optical properties (colour) of the Quantum Dots. This property alone can be exploited for the use in a number of technologies such as security tagging and biological probes.

These small particles are one of the inventions spearheading a drive to control of materials with dimensions of the order of nanometres. The potential of the area of nanotechnology as being opened up by interactions between molecular biologists, chemists physisists and almost every type of engineer will be discussed. Applications of such technologies will range from computer chips through display screens to security printing. These new technologies will impact on all of our daily lives. Nanotechnology is attracting attention from all quarters from academia, venture capitalists to the general public. This lecture will explain why the area is both so topical and important.     

Spectrofluorimetric Determination of Nickel (ΙΙ) with Murexide

A very sensitive and selective spectrofluorimetric method has been developed for nickel (ΙΙ) determination in environmental samples. The method is based on measuring the decrease in fluorescence intensity of murexide after nickel (ΙΙ) binding. The intensity of the fluorescence emission peak was measured at ex/em 345/431 nm in several solutions with pH interval 3.0–7.0. The fluorescence intensity decrease was found to be linear in the concentration range of 0.007 mg.L^?1 to 0.1 mg.L^?1 and 0.1 mg.L^?1 to 20 mg.L^?1 of nickel (ΙΙ) by using 10^?4 M murexide at pH 3. The detection limit was found 0.004 mg.L^?1. Relatively large excesses of over 20 cations and anions do not interfere. The method was successfully applied to the analysis of nickel (ΙΙ) in sea, rain and ground water. This method is very precise and accurate (R.S.D.?=?0.42 % for the determination of 0.05 mg.L?¹ nickel in 10 replicates).     

Molecular Cloning,Computational and Expression Analysis of Anthocyanidin Reductase in Tea (Camellia sinensis)

Tea [Camellia sinensis (L.) O. Kuntze] is one of the most popular non-alcoholic beverages rich in phenolic compounds, which includes epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), epicatechin (EC) and catechin (C). Anthocyanidin reductase (ANR) is responsible for catechin biosynthesis in plants, and analysis of its protein sequences and structures will be valuable for further research in the field. We have screened our dormant bud-specific complementary DNA (cDNA) library and reported 1,322-bp cDNA encoding CsANR. Analysis of the sequence revealed the presence of 1,011-bp open reading frame with coding capacity for a polypeptide of 337 amino acids, flanked by 1,123- and 196-bp 5′ and 3′ untranslated regions, respectively. Theoretical molecular weight (MW) and isoelectric point (pI) of the deduced ANR protein were predicted (using ProtParam) to be 36.4 kDa and 6.54. For the first time, we have reported 3D model of ANR from C. sinensis. Quality of the predicted model was analysed with PROCHECK analysis. Molecular docking of modelled ANR revealed similar binding pockets for both substrates and products. Expression analyses of CsANR and accumulation pattern of catechins were observed to be varied with developmental age of tissue and seasonal condition. Variation in accumulation pattern of catechins and its fractions was found to be correlated with expression pattern of ANR.     

Susceptibility Against Grey Blight Disease-Causing Fungus Pestalotiopsis sp. in Tea (Camellia sinensis (L.) O. Kuntze) Cultivars Is Influenced by Anti-oxidative Enzymes

Reactive oxygen species (ROS) production is the first level of response by a host during stress. Even though the ROS are toxic to cell, when present in a limited amount, they act as a signalling molecule for the expression of defence-related genes and later are scavenged by either enzymatic or non-enzymatic mechanisms of the host. The different anti-oxidative enzymes like glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APO), peroxidase (POD) and polyphenol oxidase (PPO) were estimated, and their activities were compared between infected and healthy leaves of the tolerant and susceptible cultivars of tea. The infected leaves of the susceptible cultivars registered higher amount of enzyme activity when compared with the tolerant cultivars. The study reveals that the more anti-oxidative enzymes, the more susceptible the cultivar will be.     

Selective fluorination of m-tyrosine by OF2

Fluorine-18 labeled aromatic amino acids are routinely used as tracers in positron emission tomography (PET) to study in vivo metabolic processes. The most versatile method for the production of such radiotracers is electrophilic fluorination of the aromatic amino acid with [¹⁸F]F₂, which is most commonly produced by the gas-phase nuclear reaction ¹⁸O(p, n)¹⁸F. Although [¹⁸F]F₂ is the major product, considerable amounts of [¹⁸F]OF₂ (up to 20%) are also produced. Electrophilic fluorination reactions of l-phenylalanine, 3-nitro-l-tyrosine, 4-nitro-dl-phenylalanine, 3,4-dihydroxyphenyl-l-alanine (l-DOPA), 3-O-methyl-l-DOPA, 3,4-dimethoxy-l-phenylalanine, p-tyrosine and o-tyrosine in H₂O and of m-tyrosine in anhydrous HF (aHF), CF₃SO₃H, CF₃COOH, CH₃COOH, HCOOH and H₂O using OF₂ were investigated. Although F₂ is an efficient fluorinating agent in aHF, electrophilic fluorination reactions using OF₂ were shown to be most efficient in less acidic media such as H₂O. In addition, and contrary to reports that OF₂ and F₂ have similar reactivities, m-tyrosine was the only aromatic system studied that was fluorinated by OF₂ and this was optimum in H₂O for the fluorinated m-tyrosine isomers (total yield, 4.35 ± 0.04%). The presence of [¹⁸F]OF₂ byproduct has no significant impact on the fluorination of aromatic amino acids investigated in this study and the subsequent production of their corresponding ¹⁸F-labeled radiotracers for patient use.     

Differential electrochemical behaviour of phytofabricated and chemically synthesized silver nanoparticles towards hydrogen peroxide sensing**

Silver nanoparticles (AgNPs) are one of the most widely used nanomaterials for biomedical applications. However, the impact of its synthesis by chemical and plant-mediated routes on its differential electrochemical behaviour has not been examined till date. Here, we report for the first time the differential study of the electrochemical behaviour of the AgNPs synthesized by different routes. First, the AgNPs were obtained by different routes (chemical and phytofabrication) and extensively characterized to compare their physical properties. Thereafter, a comparison of electron transfer kinetics between chemically synthesized (Ag−C) and phyto-fabricated (Ag-Phy) nanoparticles (NPs) has been studied by electrochemical techniques such as potentiodynamic cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). To further investigate the electrocatalytic properties of both types of AgNPs, we have used the peroxide moieties (H₂O₂), and the Ag−C NPs-based sensor probe has been reported to have four times better sensitivity than the Ag−Phy NPs-based sensor. The AgNPs modified sensor probes have also been tested in real-world environments to explore the consistency of their performance in complex matrices by using clinical urine samples, where we found comparable sensitivity to the standard conditions.     

Preparation,characterization and analysis of novel polyimides with anthracene,carbazole and fluorene pendent architecture

Two series of new organosoluble and thermally stable polyimides containing anthracene, and fluorene pendants were prepared by a two-step solution polycondensation reaction of new synthesized diamines with commercially available dianhydrides. All intermediates and polymers were fully characterized by FTIR, NMR, and elemental analysis and their properties including solubility and thermal stability were studied. All the resulting polymers were amorphous with inherent viscosities ranged from 0.61 to 0.84 dL/g and were readily soluble in many organic solvents.     

Synthesis and antimicrobial activity of quinoline-based 2-pyrazolines

A series of 2-pyrazolines was prepared in a reaction of quinolinylchalcones with phenyl hydrazine under both conventional and microwave-induced heating. Structures of the synthesized compounds were characterized by spectroscopic data and CHN analyses. All prepared compounds were tested for antimicrobial activity against bacterial strains, viz. Staphylococcus aureus, Salmonella typhii, Escherichia coli, and Shigella dysentery. Almost all synthesized compounds have shown antimicrobial activity; however, compounds with a chloro group as a substituent have been found to be more effective.