Silicon nanowires for sequence-specific DNA sensing: device fabrication and simulation

Highly sensitive, sequence-specific and label-free DNA sensors were demonstrated by monitoring the electronic conductance of silicon nanowires (SiNWs) with chemically bonded single-stranded (ss) DNA or peptide nucleic acid (PNA) probe molecules. For a 12-mer oligonucleotide, tens of pM of target ss-DNA in solution was recognized when the complementary DNA oligonucleotide probe was attached to the SiNW surfaces. In contrast, ss-DNA samples of ×1000 concentration with a single-base mismatch produce only a weak signal due to nonspecific binding. In order to gain a physical understanding of the change in conductance of the SiNWs with the attachment of the DNA targets and the probes, process and device simulations of the two-dimensional cross sections of the SiNWs were performed. The simulations explained the width dependence of the SiNW conductance and provided understanding to improve the sensor performance. PACS 85.35.-p; 87.83.+a; 07.07.Df     

Selective synthesis of ureas and tetrazoles from amides controlled by experimental conditions using conventional and microwave irradiation

An efficient synthetic procedure has been achieved for selective synthesis of 1,5-disubstituted tetrazoles and diaryl ureas from secondary amides in situ in the presence of NaN₃ and POCl₃ as solvent, both by conventional and microwave methods. The reaction conditions were optimized to yield selectively either tetrazoles or urea derivatives from reasonable to excellent yields. These conversions have been tested and verified with various secondary amide precursors. The synthesized compounds were characterized by ¹H NMR, ¹³C NMR and ESI-MS spectroscopic techniques.     

Antimicrobial flavonoids isolated from Indian medicinal plant Scutellaria oblonga inhibit biofilms formed by common food pathogens

Scutellaria oblonga Benth., a hitherto phytochemically unexplored Indian medicinal folklore plant was extracted with acetone and subjected to chromatography to yield nine flavonoids, for the first time from this plant. Antimicrobial assays were performed against 11 foodborne pathogens, and three molecules (Techtochrysin, Negletein and Quercitin-3-glucoside) depicted significant activity. These molecules were assessed for their rate of antibacterial action using time–kill curves which depicted complete inhibition of most of the bacteria within 12–16 h. The significant biofilm-reducing capability exhibited by these three molecules formed a significant finding of the current study. In most of the experiments, a 90–95% reduction in biofilms was observed. Thus, flavonoids as natural molecules from S. oblonga could be further researched to be used as potent antimicrobial and antibiofilm agents.     

Mathematical modeling and analysis of the molar concentrations of ethanol,acetaldehyde and ethyl acetate inside the catalyst particle

Mathematical modeling of the molar concentrations profile of ethanol, acetaldehyde and ethyl acetate inside the catalyst particle is presented. This kinetic mechanism is based on the system of non-linear reaction diffusion equations. Modified Adomian decomposition method is employed to derive the general analytical expressions of molar concentrations of ethanol, acetaldehyde and ethyl acetate for all possible values of the parameters Φ_i, γ_i and α_i (i = 1, 2, 3). Analytical results are compared with the numerical results, a satisfactory agreement is noted. Valid and invalid region of the solution for all concentrations are provided. These analytical results are useful to understand the behavior of the system.     

Application of He’s variational iteration method in nonlinear boundary value problems in enzyme– substrate reaction diffusion processes: part 1. The steady-state amperometric response

A mathematical model of amperometric biosensors has been developed. In this paper, He’s variational iteration method is implemented to give approximate and analytical solutions of non-linear reaction diffusion equations containing a non linear term related to Michaelis–Menten kinetic of the enzymatic reaction. The variational iteration method which produces the solutions in terms of convergent series, requiring no linearization or small perturbation. These analytical results are compared with available limiting case result and are found to be in good agreement.     

Equilibrium theory-based design of simulated moving bed processes under reduced purity requirements linear isotherms

The design of simulated moving bed processes under reduced purity requirements for systems whose isotherm is linear is considered. Based on the equilibrium theory of chromatography, explicit equations to uniquely identify the separation region that will ensure specified extract and raffinate purities are derived. The identification of the region requires only the knowledge of Henry constants of the solutes, the concentration of the solutes in the feed and the purity specifications. These results are validated using numerical simulations.     

Kinetics and dissociation mechanism of heptaaqua-<Emphasis Type="Italic">p</Emphasis>-nitrophenolatostrontium(II) nitrophenol

A single crystal of heptaaqua-p-nitrophenolatostrontium(II) nitrophenol (HNSN) was grown, and the structure was confirmed by UV–Vis–NIR, FT-IR, FT-NMR, and high-resolution X-ray diffraction (HRXRD) analyses. The dielectric loss, dielectric constant, and the mechanical strength of the crystal have already been reported. The dynamic, non-isothermal thermal analysis was carried out at different heating rates, and TG and DTG data were used for the interpretation of the mechanisms and kinetics of decomposition by means of a model fitting method, Coats–Redfern equation, and a model-free method, Kissinger and Flynn–Wall method. The values of activation energy (E) and the pre-exponential factor (ln A) of each stage of thermal decomposition at various linear heating rates were calculated.     

Analytical solution of nonlinear diffusion processes in modified electrode

The system of coupled nonlinear diffusion equations are solved analytically for the transport and kinetics of electrons and reactant in the layer of a modified electrode. Analytical expressions of concentrations of mediator and substrate are presented using Homotopy perturbation method. A simple expression of electrochemical rate constant K _ME⁺ is also obtained for all values of reaction parameters. The available limiting case results are compared with our results and are found to be in good agreement.     

A study on the antimicrobial efficacy of RF oxygen plasma and neem extract treated cotton fabrics

The paper deals with a thorough investigation on the antimicrobial activity of RF oxygen plasma and Azadirachtin (neem extract) treated cotton fabric. The hydrophilicity of cotton fabric was found to improve when treated with RF oxygen plasma. The process parameters such as electrode gap, time of exposure and oxygen pressure have been varied to study their effect on improving the hydrophilicity of the cotton fabric. The static immersion test has been carried out to assess the hydrophilicity of the oxygen plasma treated samples and the process parameters were optimized based on these test results. The formation of carbonyl group during surface modification in the plasma treated sample was analysed using FTIR studies. The surface morphology has been studied using SEM micrographs.The antimicrobial activity was imparted to the RF oxygen plasma treated samples using methanolic extract of neem leaves containing Azadirachtin. The antimicrobial activity of these samples has been analysed and compared with the activity of the cotton fabric treated with neem extract alone. The investigation reveals that the surface modification due to RF oxygen plasma was found to increase the hydrophilicity and hence the antimicrobial activity of the cotton fabric when treated with Azadirachtin.     

Branch-and-bound algorithms for scheduling in permutation flowshops to minimize the sum of weighted flowtime/sum of weighted tardiness/sum of weighted flowtime and weighted tardiness/sum of weighted flowtime,weighted tardiness and weighted earliness of jobs

The problem of scheduling in permutation flowshops is considered in this paper with the objectives of minimizing the sum of weighted flowtime/sum of weighted tardiness/sum of weighted flowtime and weighted tardiness/sum of weighted flowtime, weighted tardiness and weighted earliness of jobs, with each objective considered separately. Lower bounds on the given objective (corresponding to a node generated in the scheduling tree) are developed by solving an assignment problem. Branch-and-bound algorithms are developed to obtain the best permutation sequence in each case. Our algorithm incorporates a job-based lower bound (integrated with machine-based bounds) with respect to the weighted flowtime/weighted tardiness/weighted flowtime and weighted tardiness, and a machine-based lower bound with respect to the weighted earliness of jobs. The proposed algorithms are evaluated by solving many randomly generated problems of different problem sizes. The results of an extensive computational investigation for various problem sizes are presented. In addition, one of the proposed branch-and-bound algorithms is compared with a related existing branch-and-bound algorithm.