3,908 research outputs found
Molecular beacons: nucleic acid hybridization and emerging applications
Molecular beacons (MBs) are a novel class of nucleic acid probes that become fluorescent when bound to a complementary sequence. Because of this characteristic, coupled with the sequence specificity of nucleic acid hybridization and the sensitivity of fluorescence techniques, MBs are very useful probes for a variety of applications requiring the detection of DNA or RNA. We survey various applications of MBs, including the monitoring of DNA triplex formation, and describe recent developments in MB design that enhance their sensitivity
Novel ZnO nanostructures over gold and silver nanoparticle assemblies
We report the growth of well-oriented nest (reticulum)-like and lotus flower-like submicron structures of ZnO, over gold and silver nanoparticle assemblies, respectively. The structures were grown by a convenient chemical bath deposition method in a nutrient solution made of zinc nitrate (Zn(NO3)2 · 6H2O) and methyl amine (CH3NH2) at low temperature. SEM, XRD, Raman, UV-Vis and fluorescence spectra were used to study the morphology, crystallinity and phase purity of the structures. The ZnO submicron structures were found to be in the hexagonal wurtzite phase
Differential Evolution Algorithm with Diversified Vicinity Operator for Optimal Routing and Clustering of Energy Efficient Wireless Sensor Networks
Due to large dimension of clusters and increasing size of sensor nodes, finding the optimal route and cluster for large wireless sensor networks (WSN) seems to be highly complex and cumbersome. This paper proposes a new method to determine a reasonably better solution of the clustering and routing problem with the highest concern of efficient energy consumption of the sensor nodes for extending network life time. The proposed method is based on the Differential Evolution (DE) algorithm with an improvised search operator called Diversified Vicinity Procedure (DVP), which models a trade-off between energy consumption of the cluster heads and delay in forwarding the data packets. The obtained route using the proposed method from all the gateways to the base station is comparatively lesser in overall distance with less number of data forwards. Extensive numerical experiments demonstrate the superiority of the proposed method in managing energy consumption of the WSN and the results are compared with the other algorithms reported in the literature
Flow-induced transverse electrical potential across an assembly of gold nanoparticles
We report the generation of a potential difference, of the order of tens of millivolts, induced by the flow of polar liquids over an assembly of gold nanoparticles. The device consisted of two conducting glass plates, one of which contained the gold nanoparticle multilayer assembly. The potential generated is in transverse direction to the flow and is dependent on the nature of the flowing liquid. We propose a simple theoretical model to account qualitatively for the generation of the flow-induced transverse potential
Conceptual design study of a coal gasification combined-cycle powerplant for industrial cogeneration
A conceptual design study was conducted to assess technical feasibility, environmental characteristics, and economics of coal gasification. The feasibility of a coal gasification combined cycle cogeneration powerplant was examined in response to energy needs and to national policy aimed at decreasing dependence on oil and natural gas. The powerplant provides the steam heating and baseload electrical requirements while serving as a prototype for industrial cogeneration and a modular building block for utility applications. The following topics are discussed: (1) screening of candidate gasification, sulfur removal and power conversion components; (2) definition of a reference system; (3) quantification of plant emissions and waste streams; (4) estimates of capital and operating costs; and (5) a procurement and construction schedule. It is concluded that the proposed powerplant is technically feasible and environmentally superior
Entanglement entropy and multifractality at localization transitions
The von Neumann entanglement entropy is a useful measure to characterize a
quantum phase transition. We investigate the non-analyticity of this entropy at
disorder-dominated quantum phase transitions in non-interacting electronic
systems. At these critical points, the von Neumann entropy is determined by the
single particle wave function intensity which exhibits complex scale invariant
fluctuations. We find that the concept of multifractality is naturally suited
for studying von Neumann entropy of the critical wave functions. Our numerical
simulations of the three dimensional Anderson localization transition and the
integer quantum Hall plateau transition show that the entanglement at these
transitions is well described using multifractal analysis.Comment: v3, 5 pages, published versio
Issues in Physics Practicals in an Open and Distance Learning Environment
This paper reviews the objectives of physics practicals in physics education in relation to the
hilosophy of open and distance learning programme. The various issues that arise in the
implementation of physics experiment based on an existing practical model are presented. Two
major concerns are the effectiveness of the practical sessions and sustaining the fundamentals
of the open and distance learning programme. A new practical physics model is then proposed,
which enables students to experience physics experiments without violating the open and
distance learning programme fundamentals. (Authors' abstract
Rapid self-assembly of α-synuclein observed by in situ atomic force microscopy
Self-assembly of α−synuclein resulting in protein aggregates of diverse morphology has been implicated in the pathogenesis of Parkinson’s disease and other neurodegenerative disorders known as synucleinopathies. Apart from its biomedical relevance, this aggregation process is representative of the interconversion of an unfolded protein into nanostructures with typical amyloid features. We have used in situ tapping mode atomic force microscopy (AFM) to continuously monitor the self-assembly of wild-type α-synuclein, its disease-related mutants A30P and A53T, and the C-terminally truncated variant α-synuclein(1-108). Different aggregation modes were observed depending on experimental conditions, i.e. pH, protein concentration, polyamine concentration, temperature and the supporting substrate. At pH 7.5, in the absence of the biogenic polyamines spermidine or spermine, elongated sheets 1.1(±0.2)nm in height and presumably representing individual β-sheet structures, were formed on mica substrates within a few minutes. Their orientation was directed by the crystalline substructure of the substrate. In contrast, sheet formation was not observed with hydrophobic highly oriented pyrolytic graphite (HOPG) substrates, suggesting that negatively charged surfaces promote α-synuclein self-assembly. In the presence of spermidine or spermine 5.9(±1.0) nm high spheroidal structures were preferentially formed, sharing characteristics with similar structures previously reported for several amyloidogenic proteins and linked to neurotoxicity. Alpha-synuclein spheroid formation depended critically on polyamine binding to the Cterminus, revealing a promoting effect of the C-terminus on α-synuclein assembly in the bound state. In rare cases, fibril growth from spheroids or preformed aggregates was observed. At pH 5.0, fibrils were formed initially and incorporated into amorphous aggregates in the course of the aggregation process, providing evidence for the potential of amyloid fibril surfaces to act as nucleation sites in amorphous aggregation. This study provides a direct insight into different modes of α-synuclein self-assembly and identifies key factors modulating the aggregation process
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