DNA sensing by amplifying the number of near-infrared emitting, oligonucleotide-encapsulated silver clusters

A bifunctional oligonucleotide integrates in situ synthesis of a fluorogenic silver cluster with recognition of a target DNA sequence. With the template C(3)AC(3)AC(3)GC(3)A, a complex forms with 10 silver atoms that possesses electronic transitions in the near-infrared and that is detected at nanomolar concentrations using diode laser excitation. Pendant to this cluster encoding region, the recognition component binds a target DNA strand through hybridization, and decoupling of these two regions of the composite sensor renders a modular sensor for specific oligonucleotides. A target is detected using a quencher strand that bridges the cluster template and recognition components and disturbs cluster binding, as indicated by static quenching. Competitive displacement of the quencher by the target strand restores the favored cluster environment, and our key finding is that this exchange enhances emission through a proportional increase in the number of emissive clusters. DNA detection is also accomplished in serum-containing buffers by taking advantage of the high brightness of this fluorophore and the inherently low endogenous background in the near-infrared spectral region. Cluster stability in this biological environment is enhanced by supplementing the solutions with Ag(+).     

Chemical-induced pH-mediated molecular switch

The transmembrane protein α-hemolysin pore has been used to develop ultrasensitive biosensors, study biomolecular folding and unfolding, investigate covalent and noncovalent bonding interactions, and probe enzyme kinetics. Here, we report that, by addition of ionic liquid tetrakis(hydroxymethyl)phosphonium chloride solution to the α-hemolysin pore, the α-hemolysin channel can be controlled open or closed by adjusting the pH of the solution. This approach can be employed to develop a novel molecular switch to regulate molecular transport and should find potential applications as a "smart" drug delivery method.     

Performance analysis of a packet assembly function

A general packet assembly function in which the bundle is completed whenever any one of a number of conditions is satisfied is analyzed. These conditions subsume those most commonly found in practice. The analysis yields the distribution of bundle size. In several useful cases, closed form expressions for the mean bundle size is obtained     

Numerical simulation data for assessment of particle-laden turbulent flow models

This paper presents a collection of numerical simulation data which provides a reference for the assessment of various statistical/stochastic models in incompressible homogeneous particle-laden turbulent flows. Four different homogeneous flow configurations are studied, namely, homogeneous shear flow, homogeneous plane strain flow, homogeneous axisymmetric expansion and contraction. An Eulerian-Lagrangian formulation is used for the two-phase flow simulation. A Fourier pseudospectral method is used for the solution of the Eulerian carrier-phase equations without resorting to any turbulence model. The Lagrangian equations for the dispersed phase are integrated using a modified Stokes drag. For the shear flow, both monodispersed and polydispersed particles have been considered. In this paper, only the results that are relevant for assessment of various statistical models for both the fluid and dispersed phases are presented.     

On the development of a three-dimensional transient thermal model to predict ingot cooling behavior during the start-up phase of the direct chill-casting process for an AA5182 aluminum alloy ingot

The control of the heat transfer during the start-up phase of the direct-chill (DC) casting process for aluminum sheet ingots is critical from the standpoint of defect formation. Process control is difficult because of the various inter-related phenomena occurring during the cast start-up. First, the transport of heat to the mold is altered as the ingot base deforms and the sides are pulled inward during the start-up phase. Second, the range of temperatures and water flow conditions occurring on the ingot surface as it emerges from the mold results in the full range of boiling-water heat-transfer conditions—e.g., film boiling, transition boiling, nucleate boiling, and convection—making the rate of transport highly variable. For example, points on the ingot surface below the point of water impingement can experience film boiling, resulting in the water being ejected from the surface, causing a dramatic decrease in heat transfer below the point of ejection. Finally, the water flowing down the ingot sides may enter the gap formed between the ingot base and the bottom block due to butt curl. This process alters the heat transfer from the base of the ingot and, in turn, affects the surface temperature on the ingot faces, due to the transport of heat within the ingot in the vertical direction. A comprehensive mathematical model has been developed to describe heat transfer during the start-up phase of the DC casting process. The model, based on the commercial finite-element package ABAQUS, includes primary cooling via the mold, secondary cooling via the chill water, and ingot-base cooling. The algorithm used to account for secondary cooling to the water includes boiling curves that are a function of ingot-surface temperature, water flow rate, impingement-point temperature, and position relative to the point of water impingement. In addition, a secondary cooling algorithm accounts for water ejection, which can occur at low water flow rates (low heat-extraction rates). The algorithm used to describe ingot-base cooling includes both the drop in contact heat transfer due to gap formation between the ingot base and bottom block (arising from butt curl) as well as the increase in heat transfer due to water incursion within the gap. The model has been validated against temperature measurements obtained from two 711×1680 mm AA5182 ingots, cast under different start-up conditions (nontypical “cold” practice and nontypical “hot” practice). Temperature measurements were taken at various locations on the ingot rolling and narrow faces, ingot base, and top surface of the bottom block. Ingot-based deflection data were also obtained for the two test conditions. Comparison of the model predictions with the data collected from the cast/embedded thermocouples indicates that the model accounts for the processes of water ejection and water incursion and is capable of describing the flow of heat in the early stages of the casting process satisfactorily.     

Comparison of key informant and survey methods for ascertainment of childhood epilepsy in West Bengal, India

BACKGROUND: This study aimed to compare efficacy and cost of key informants and survey for ascertainment of childhood epilepsy within a treatment context in rural India. METHODS: The study was set in a non-governmental, community programme for the functional and socioeconomic rehabilitation of children with disabilities in rural West Bengal, India. Ascertainment was by two methods: house-to-house survey of 15000 households and also by 430 key informants including village leaders, health workers and 670 schoolchildren. Methods were compared for positive predictive value, and sensitivity by capture-recapture technique. Ninety four children were enrolled into treatment. Predictors of treatment success were determined by multiple logistic regression analysis, giving adjusted odds ratios for remission. The costs of identifying one case and one treatment success were measured by costing personnel, materials and overheads. RESULTS: The survey was four times as sensitive as key informants although the positive predictive values were similar (36%, 40%). The survey had an absolute sensitivity of only 59%. Identification by key informants strongly predicted successful treatment outcome (odds ratio [OR] = 4.74, 95% confidence interval [CI] : 1.19-18.85). The cost of finding one case was US$11 and US$14, and of finding one successful treatment outcome US$35 and US$67 for informants and survey respectively. Key informants were essential in attaining longer term programme objectives. CONCLUSIONS: In the context of a treatment programme, key informants were the more cost-effective method, but community involvement was traded against low sensitivity in the short term. Overall ascertainment costs were significant in the context of primary health care in India.     

Reliability bounds and other inequalities for discrete life distributions

In this paper we give sharp bounds on the reliability of discrete IFR, IFRA, NBU, DFR, DFRA and NWU classes, based on one known moment. Subsequently the discrete analogues of several continuous-time results related to maintained systems are also presented.     

Exact piezothermoelastic axisymmetric solution of a finite transversely isotropic cylindrical shell

This work presents an exact piezothermoelastic solution of a finite transversely isotropic piezoelectric cylindrical shell under axisymmetric thermal, pressure and electrostatic excitation. The general solution of the governing equations is obtained in terms of potential functions which satisfy the boundary conditions at the ends. The axisymmetric loadings are expanded as a Fourier series in the axial coordinate. The coefficients in the infinite set of potential functions are obtained by solving sets of six algebraic equations resulting from the satisfaction of boundary conditions at the inner and outer surfaces of the shell for each Fourier component. The inverse problem of inferring the applied temperature and pressure fields from the given measured distribution of electrical potential difference between the inner and outer surfaces of the shell has also been solved. Numerical results are presented for typical pressure, thermal and electrostatic loadings.