Dynamically controlled dielectrophoresis using resonant tuning

Electrically polarizable micro- and nanoparticles and droplets can be trapped using the gradient electric field of electrodes. But the spatial profile of the resultant dielectrophoretic force is fixed once the electrode structure is defined. To change the force profile, entire complex lab-on-a-chip systems must be re-fabricated with modified electrode structures. To overcome this problem, we propose an approach for the dynamic control of the spatial profile of the dielectrophoretic force by interfacing the trap electrodes with a resistor and an inductor to form a resonant resistor–inductor–capacitor (RLC) circuit. Using a dielectrophoretically trapped water droplet suspended in silicone oil, we show that the resonator amplitude, detuning, and linewidth can be continuously varied by changing the supply voltage, supply frequency, and the circuit resistance to obtain the desired trap depth, range, and stiffness. We show that by proper tuning of the resonator, the trap range can be extended without increasing the supply voltage, thus preventing sensitive samples from exposure to high electric fields at the stable trapping position. Such unprecedented dynamic control of dielectrophoretic forces opens avenues for the tunable active manipulation of sensitive biological and biochemical specimen in droplet microfluidic devices used for single-cell and biochemical reaction analysis.     

Kinetic investigations into the synthesis of disulphides via tetrathiomolybdate as a sulphur-transfer reagent

Kinetic and mechanistic aspects of the conversion of halides to disulphides using benzyl triethyl ammonium tetrathiomolybdate as sulphur-transfer reagent were investigated. The reaction follows a 1:1 stoichiometry with overall second-order kinetics and involves the formation of monosulphides in addition to disulphides. In the light of our observations, we propose a nucleophilic substitution: carbon–metal–carbon (S_N-CMC) reaction mechanism. The proposed mechanism, besides accounting for all of our experimental observations, also explains many aspects of such reactions that have been reported earlier by various groups.     

Biologically active organotin(IV) schiff base complexes

Organotin(IV) complexes with the general formulae R₃ML [R: alkyl (Et, Ph and Bz), M: Sn and L: 1,3-bis(2- hydroxybenzylidene)thiourea were synthesized. The newly synthesized schiff base and its complexes were characterized by elemental analysis, melting point, molecular weight determination, IR and NMR [¹H, ¹³C and ¹¹⁹Sn] spectral methods. In the light of these techniques, a tetrahedral geometry around the tin atom is proposed for the synthesized complexes. The experimental data have been compared with those in the literature which were found to coincide very well with the assigned structures. The ligands and their tin(IV) complexes were screened in vitro for their antibacterial activities. It was found that they possessed significant antibacterial activity and the effect of Ph₃SnL was possibly superior to those of Et₃SnL, Bz₃SnL and ligand. These findings add new insights onto the synthesis of antibacterial drugs as the synthesized compounds showed promising antimicrobial activity.     

Synthesis,Structural Investigations and Biological Screening of Diorganotin（Ⅳ） Complexes Derived from 5,5-Diethyl Sodium Barbital

Some biologically important tin（Ⅳ） complexes derived from 5,5-diethyl sodium barbital have been synthesized and characterized through various analytical and spectroscopic techniques such as IR, ^1H-, ^13C-NMR and ^119mSn mossbauer. On the basis of these spectroscopic techniques, octahedral geometry has been assigned to all the novel compounds. These complexes, soluble in DMSO and DMF, were screened against a wide range of microorganisms. The results proved that the diphenyltin（Ⅳ） and dibutyltin（Ⅳ） complexes exhibit excellent activity against all types of microorganisms, while the rest of the compounds show significant activity that can be used during the biological study.     

Optimal control of a vector borne disease with horizontal transmission

The paper presents the optimal control applied to a vector borne disease with direct transmission in host population. First, we show the existence of the control problem and then use both analytical and numerical techniques to investigate that there are cost effective control efforts for prevention of direct and indirect transmission of disease. In order to do this three control functions are used, one for vector-reduction strategies and the other two for personal (human) protection and blood screening, respectively. We completely characterize the optimal control and compute the numerical solution of the optimality system using an iterative method.     

Approximate conservation laws of nonlinear perturbed heat and wave equations

We construct approximate conservation laws for non-variational nonlinear perturbed (1+1) heat and wave equations by utilizing the partial Lagrangian approach. These perturbed nonlinear heat and wave equations arise in a number of important applications which are reviewed. Approximate symmetries of these have been obtained in the literature. Approximate partial Noether operators associated with a partial Lagrangian of the underlying perturbed heat and wave equations are derived herein. These approximate partial Noether operators are then used via the approximate version of the partial Noether theorem in the construction of approximate conservation laws of the underlying perturbed heat and wave equations.     

Efficient catalytic effect of CuO nanostructures on the degradation of organic dyes

An efficient catalytic effect of petals and flowers like CuO nanostructures (NSs) on the degradation of two organic dyes, methylene blue (MB) and rhodamine B (RB) were investigated. The highest degradation of 95% in CuO petals and 72% in flowers for MB is observed in 24 h. For RB, the degradation was 85% and 80% in petals and flowers, respectively for 5 h. It was observed that CuO petals appeared to be more active than flowers for degradation of both dyes associated to high specific surface area. The petals and flower like CuO NSs were synthesized using the chemical bath method at 90 °C. The grown CuO NSs were characterized using scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD).     

How changes in cell mechanical properties induce cancerous behavior

Tumor growth and metastasis are ultimately mechanical processes involving cell migration and uncontrolled division. Using a 3D discrete model of cells, we show that increased compliance as observed for cancer cells causes them to grow at a much faster rate compared to surrounding healthy cells. We also show how changes in intercellular binding influence tumor malignancy and metastatic potential. These findings suggest that changes in the mechanical properties of cancer cells is the proximate cause of uncontrolled division and migration and various biochemical factors drive cancer progression via this mechanism.     

Power spectral density of subsonic jet noise

The scaling of the power scaling density (PSD) of the far field noise for subsonic, unheated, axisymmetric jets has been examined based on data obtained from the literature as well as from new experiments. It has been demonstrated that the PSD scales as the Strouhal number (St_D) alone for most locations, except at shalloow angles (θ<30°) where the best scaling results with the Helmholtz number times the Doppler factor, H_D(1?M_c cos θ). In contrast to the common assumption, scaling with St_D times the Doppler factor only degraded the collapse of the data. Also, a “source convection Mach number”, M_c = 0·5 M, rather than the commonly used value of 0·67 M, yielded the best collapse, M_c = 0·5 M agreeing with the recent measurement of jet large-scale structure convection velocity. At θ = 90°, the amplitude of the PSD varies as U^6·5, which agrees with the observed U^7·5 variation of the overall intensity; a similar power law assumed at θ ～- 30° yields an exponent 8·5 for the PSD. Contrary to claims in the literature, the PSD amplitude was not observed to vary sharply about any critical Reynolds number. For shallow angles, the scaling on H_D (1 ? M_c cos θ) also contrasts simple H_D scaling previously observed on the basis of one-third octave spectra.     

Dynamic response of cable-stayed bridges to moving vehicles using the structural impedance method

The importance of dynamic interactions between cable-stayed bridges and heavy moving vehicles, such as trucks and locomotives, has been recognised by bridge engineers for a long time. A structural impedance algorithm is developed for analysing the dynamic response of cable-stayed bridges subjected to traversing vehicles. The bridge deck is modelled as an elastic plate, and the cables are idealised as springs for simplicity. The vehicles are modelled as a series of masses with suspension systems moving with different speeds and accelerations. A comprehensive computer program, CABLESIM, is developed for the static and dynamic analyses of a cable-stayed bridge. The accuracy of the numerical procedure and its computer implementation is verified with the available analytical and experimental results. A parametric study is conducted to investigate the effects of vehicle velocity, girder depth, different types of cable arrangements, and traffic load on the dynamic response of the deck. The numerical results are expected to be important in assessing the dynamics of cable-stayed bridge components and in determining the safety and allowable traffic conditions.