A naked singularity stable under scalar field perturbations

We prove the stability of a spacetime with a naked singularity under scalar field perturbations, where the perturbations are regular at the singularity. This spacetime, found by Janis, Newman and Winicour, and independently by Wyman, is sourced by a massless scalar field and also arises as a certain limit of a class of charged dilatonic solutions in string theory. This stability result opens up specific questions for investigation related to the cosmic censorship conjecture and the mechanism by which it is implemented in nature.Comment: 19 pages, version to appear in IJMPD, references adde

Avian Fauna

Avian Faun

Mangrove vegetation

Mangrove vegetation includes plants ranging from herbs, shrubs to tall trees. In favourable conditions the mangrove trees can form dense forests in intertidal habitats. However; only a few species form a massive canopy. The main characteristic features of these special type of plants are the tidal amplitude, defined by the species, and their ability to tolerate high salinity and stress. The majority of the plant groups have adaptations like prop and stilt roots for fixing support and the pneumatophores otherwise called the breathing roots for exchanging gases and the viviparous germination. In addition to these, the plants have leathery, dark, ever green leaves with deeply embeded stomata and aquous tissues

An Efficient Power Control Technique for High-Frequency Resonant Inverter in Induction Heating System

An efficacious and reliable power control technique has been developed which can be used to regulate the output power of a high-frequency full bridge series resonant inverter (HF-FBSRI) in an induction heating (IH) system. In this paper, a modified buck-boost converter is presented to control the DC link/bus voltage which maintains the IH system under resonant mode and optimizes the performance of the IH system. Controlled DC link/bus voltage has been applied to this HF- FBSRI to control the average output power in the IH system. Using this aimed control technique, a wide range of output powers has been controlled and consistent performance of the IH system has been achieved. ZVS switching technique has been used to reduce the switching losses. Varying average power has been obtained at different duty cycles ranging from 0.2 to 0.8 with variable DC link voltage and it has been corroborated using PSIM environment for an IH system rated at 5500W

EEG Based Gesture Mimicking by An Artificial Limb Using Cascade-Correlation Learning Architecture

Patients with prosthesis defects find it is very difficult to perform day-to-day basic tasks which involve employment of their limbs. This motivates us to develop a system where an artificial limb is employed to mimic the arm gestures of the patients for assisting them. Towards developing this system, we have taken the help from the electroencephalography (EEG) signals acquired from the brain of the patients to build a bypass network (BPN) to direct the artificial limb. Since difficulties are already present in the arm movements of the patients (here subjects), thus only gestures of those subjects are not sufficient to build the proposed system. This research finds tremendous applications in rehabilitative aid for the disable persons. To concretize our goal we have developed an experimental setup, where the target subject (for training phase healthy subjects are taken into account) is asked to catch a ball while his/her brain (occipital, parietal and motor cortex) signals using EEG acquisition device and body gestures using Kinect sensor are simultaneously acquired. These data are mapped using four cascade-correlation learning architecture (CCLA) to train artificial limb (we have used Jaco robot arm) to move accordingly. Utilizing the mapping results obtained from these four CCLAs, a BPN is developed. When a rehabilitative patient is unable to catch the ball, then in that scenario, the artificial limb is helpful for assisting the patient to catch the ball with a high accuracy of 85.65%. The proposed system can be implemented not only for ball catching experiment but also in several applications where an artificial limb needs to perform a locomotive task based on EEG and body gesture

First report of isolation and characterization of Photobacterium damselae subsp. damselae from cage-farmed cobia (Rachycentron canadum)

Cobia (Rachycentron canadum) has been considered as a potential species for aquaculture because of its fast growth and commercial value. As a consequence of successful spawning and seed production, there has been a significant demand for cage farming of cobia in India (Philipose et al. 2013). Not many reports are available on diseases of cage-farmed cobia. Globally, mortality due to pasteurellosis in cage-cultured cobia caused by Photobacterium damselae subsp. piscicida has been reported (Liu, Lin & Lee 2003). Vibriosis caused by Vibrio alginolyticus, V. harveyi, V. parahemolyticus and V. vulnificus has also been responsible for mortalities in cage-cultured cobia (Rajan et al. 2001; Liu et al. 2004). Photobacterium damselae subsp. damselae was originally isolated from the skin lesions of damsel fish, Chromis punctipinnis (Love et al. 1981). Subsequently, diseases caused by this pathogen have been reported in several cultivable fish species like seabream (Vera, Navas & Fouz 1991), eel (Ketterer & Eaves 1992), turbot (Fouz et al. 1992), ovate pompano (Zhao et al. 2009) and Asian seabass (Kanchanopas-Barnette et al. 2009). Infection caused by P. damselae subsp. damselae has also been recorded in marine mammals like dolphins (Fujioka et al. 1988) and several wild fish species (Han et al. 2009). Pathogenicity of this bacterium in several marine fish species and humans has been reviewed (Rivas, Lemos & Osorio 2013a). There have been no reports on mortality caused by this pathogen in cobia. This study was envisaged with the objectives to describe the disease epizootic caused by P. damselae subsp. damselae in cage-farmed cobia and characterize the pathogen

Association of Vibrio harveyi in mortality of mangrove red snapper (Lutjanus argentimaculatus, Forsskål, 1775) cultured in open sea cages

A case of vibriosis caused by Vibrio harveyi in adult mangrove red snappers reared in floating net cages is reported for the first time from India. The pathogen was confirmed using biochemical characterisation, by nested PCR and 16S rRNA gene sequencing. Histopathology revealed chronic nature of the disease. The outbreak of mortality was consequent to elevated water temperature and handling. Importance of stress factors as stimulus to outbreak of mortality is discussed

Controlled assembly of SNAP-PNA-fluorophore systems on DNA templates to produce fluorescence resonance energy transfer

The SNAP protein is a widely used self-labeling tag that can be used for tracking protein localization and trafficking in living systems. A model system providing controlled alignment of SNAP-tag units can provide a new way to study clustering of fusion proteins. In this work, fluorescent SNAP-PNA conjugates were controllably assembled on DNA frameworks forming dimers, trimers, and tetramers. Modification of peptide nucleic acid (PNA) with the O6-benzyl guanine (BG) group allowed the generation of site-selective covalent links between PNA and the SNAP protein. The modified BG-PNAs were labeled with fluorescent Atto dyes and subsequently chemo-selectively conjugated to SNAP protein. Efficient assembly into dimer and oligomer forms was verified via size exclusion chromatography (SEC), electrophoresis (SDS-PAGE), and fluorescence spectroscopy. DNA directed assembly of homo- and hetero-dimers of SNAP-PNA constructs induced homo- and hetero-FRET, respectively. Longer DNA scaffolds controllably aligned similar fluorescent SNAP-PNA constructs into higher oligomers exhibiting homo-FRET. The combined SEC and homo-FRET studies indicated the 1:1 and saturated assemblies of SNAP-PNA-fluorophore:DNA formed preferentially in this system. This suggested a kinetic/stoichiometric model of assembly rather than binomially distributed products. These BG-PNA-fluorophore building blocks allow facile introduction of fluorophores and/or assembly directing moieties onto any protein containing SNAP. Template directed assembly of PNA modified SNAP proteins may be used to investigate clustering behavior both with and without fluorescent labels which may find use in the study of assembly processes in cells

Power conversion techniques using multi-phase transformer: Configurations, applications, issues and recommendations

Recently, the superiority of multi-phase systems in comparison to three-phase energy systems has been demonstrated with regards to power generation, transmission, distribution, and utilization in particular. Generally, two techniques, specifically semiconductor converter and special transformers (static and passive transformation) have been commonly employed for power generation by utilizing multi-phase systems from the available three-phase power system. The generation of multi-phase power at a fixed frequency by utilizing the static transformation method presents certain advantages compared to semiconductor converters such as reliability, cost-effectiveness, efficiency, and lower total harmonics distortion (THD). Multi-phase transformers are essential to evaluate the parameters of a multi-phase motor, as they require a multi-phase signal that is pure sine wave in nature. However, multi-phase transformers are not suitable for variable frequency applications. Moreover, they have shortcomings with regard to impedance mismatching, the unequal number of turns which lead to inaccurate results in per phase equivalent circuits, which results in an imbalance output in phase voltages and currents. Therefore, this paper aims to investigate multi-phase power transformation from a three-phase system and examine the different static multiphase transformation techniques. In line with this matter, this study outlines various theories and configurations of transformers, including three-phase to five-, seven-, eleven-, and thirteen-phase transformers. Moreover, the review discusses impedance mismatching, voltage unbalance, and per phase equivalent circuit modeling and fault analysis in multi-phase systems. Moreover, various artificial intelligence-based optimization techniques such as particle swarm optimization (PSO) and the genetic algorithm (GA) are explored to address various existing issues. Finally, the review delivers effective future suggestions that would serve as valuable opportunities, guidelines, and directions for power engineers, industries, and decision-makers to further research on multi-phase transformer improvements towards sustainable operation and management.This work was supported by the Universiti Kebangsaan Malaysia under Grant Code GP-2021-K023221. This work also received partial financial support from Universiti Kebangsaan Malaysia under Grant Code GGPM-2020-006.Scopu

Sulfonated Styrene-(ethylene-co-butylene)-styrene/Montmorillonite Clay Nanocomposites: Synthesis, Morphology, and Properties

Sulfonated styrene-(ethylene-butylene)-styrene triblock copolymer (SSEBS) was synthesized by reaction of acetyl sulfate with SEBS. SSESB-clay nanocomposites were then prepared from hydrophilic Na-montmorillonite (MT) and organically (quaternary amine) modified hydrophobic nanoclay (OMT) at very low loading. SEBS did not show improvement in properties with MT-based nanocomposites. On sulfonation (3 and 6 weight%) of SEBS, hydrophilic MT clay-based nanocomposites exhibited better mechanical, dynamic mechanical, and thermal properties, and also controlled water–methanol mixture uptake and permeation and AC resistance. Microstructure determined by X-ray diffraction, atomic force microscopy, and transmission electron microscopy due to better dispersion of MT nanoclay particles and interaction of MT with SSEBS matrix was responsible for this effect. The resulting nanocomposites have potential as proton transfer membranes for Fuel Cell applications