Encapsulated microbubbles and echogenic liposomes for contrast ultrasound imaging and targeted drug delivery

Micron- to nanometer-sized ultrasound agents, like encapsulated microbubbles and echogenic liposomes, are being developed for diagnostic imaging and ultrasound mediated drug/gene delivery. This review provides an overview of the current state of the art of the mathematical models of the acoustic behavior of ultrasound contrast microbubbles. We also present a review of the in vitro experimental characterization of the acoustic properties of microbubble based contrast agents undertaken in our laboratory. The hierarchical two-pronged approach of modeling contrast agents we developed is demonstrated for a lipid coated (Sonazoid $^\mathrm{TM})$ and a polymer shelled (poly D-L-lactic acid) contrast microbubbles. The acoustic and drug release properties of the newly developed echogenic liposomes are discussed for their use as simultaneous imaging and drug/gene delivery agents. Although echogenicity is conclusively demonstrated in experiments, its physical mechanisms remain uncertain. Addressing questions raised here will accelerate further development and eventual clinical approval of these novel technologies.     

Role of additives; sodium dodecyl sulphate and manganese chloride on morphology of Zn1−xMnxO nanoparticles and their photoluminescence properties

In the present study Zn_1−xMn_xO (x = 0, 0.05 and 0.1) nanoparticles (NPs) have been synthesised in aqueous solution phase at mild reaction temperature 100 °C in moderate alkaline medium (pH = 9.5), and the role of external additives; like sodium dodecyl sulphate and manganese chloride on the morphology and size of the products has been explored on the basis of transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectral analyses data. ZnO hexagonal nano-plates, core–shell like spherical/ellipsoidal Zn_0.95Mn_0.05O structures and thin sheets, thorn/needle mixed shaped Zn_0.9Mn_0.1O structures have been observed in TEM and SEM images. Zn(OH)₂ formed in moderate alkaline medium, converted to Zn(II) hydroxo complex ions on dissolution, which further recrystallizes to produce wurtzite ZnO at 100 °C. From XRD and EDX analysis, successful doping of Mn²⁺ ions at the Zn²⁺ sites in ZnO host has been proved. In the photoluminescence spectra, the observed blue shifts in NBE peaks and decrease of emissions intensity on Mn doping have thoroughly been discussed in the present investigation.     

Effect of Simulated Microgravity on the Activity of Regulatory Enzymes of Glycolysis and Gluconeogenesis in Mice Liver

Gravity supports all the life activities present on earth. Microgravity environments have effect on the biological functions and physiological status of an individual. The present study was undertaken to investigate the effect of simulated microgravity on important regulatory enzymes of carbohydrate metabolism in liver using HLS mice model. Following hind limb unloading of mice for 11 days the animal’s average body weights were found to be not different, while the liver weights were decreased and found to be significantly different (p < 0.05) from control mice. Further, in liver the specific activity of hexokinase enzyme was reduced (p < 0.02) and the phosphoenolpyruvate carboxykinase activity was significantly increased in simulated microgravity subjected mice compared to control (p < 0.003). Immunoblot analysis show decreased phosphofructokinase-2 activity in HLS mice compared to control. Liver lactate dehydrogenase activity significantly reduced in simulated microgravity subjected mice (p < 0.005). Thus in our study the rodents have adapted to simulated microgravity conditions, with decreased glycolysis and increased gluconeogenesis in liver and reciprocally regulated.     

Study of electrical and micro-structural properties of high-κ gate dielectric stacks deposited using pulse laser deposition for MOS capacitor applications

The electrical properties of hafnium oxide (HfO₂) gate dielectric as a metal–oxide–semiconductor (MOS) capacitor structure deposited using pulse laser deposition (PLD) technique at optimum substrate temperatures in an oxygen ambient gas are investigated. The film thickness and microstructure are examined using ellipsometer and atomic force microscope (AFM), respectively to see the effect of substrate temperatures on the device properties. The electrical J–V, C–V characteristics of the dielectric films are investigated employing Al–HfO₂–Si MOS capacitor structure. The important parameters like leakage current density, flat-band voltage (V_fb) and oxide-charge density (Q_ox) for MOS capacitors are extracted and investigated for optimum substrate temperature. Further, electrical studies of these MOS capacitors have been carried out by incorporating La₂O₃ into HfO₂ to fabricate HfO₂/La₂O₃ dielectric stacks at an optimized substrate temperature of 800 °C using a PLD deposition technique under oxygen ambient. These Al–HfO₂–La₂O₃–Si dielectric stacks MOS capacitor structure are found to possess better electrical properties than that of HfO₂ based MOS capacitors using the PLD deposition technique.     

An 8-bit low power DAC with re-used distributed binary cells architecture for reconfigurable transmitters

In this work an 8-bit DAC is presented which uses a new segmented architecture, where distributed binary cells are re-used in thermometric manner to realize the MSB unit cells. The DAC has been fabricated in 0.18 μm five-metal CMOS n-well process to be embedded in multi-standard reconfigurable wireless transmitters for low-speed applications. The proposed architecture has an inherent ability to reduce midcode glitch like the unary architecture, and the simulated midcode glitch is only 0.01 pV s. Simulation results show that the proposed DAC performs with an integral nonlinearity (INL) of 0.33 LSB and a differential nonlinearity (DNL) of 0.14 LSB. The DAC can achieve a maximum measured SFDR of 65.19 dB for 97.50 kHz signal at a sampling rate of 100 MSPS, without using any calibration or dynamic element matching (DEM) technique. For 1.07 MHz signal the measured SFDR is 56.84 dB at 100 MSPS sampling rate. At 50 MSPS sampling frequency and 146 kHz signal the SFDR of the DAC is 65.90 dB. The measured SFDR at 538 kHz signal is 63.62 dB for a sampling rate of 50 MSPS. Measured third order intermodulation distortion of the DAC is 58.55 dB, for a dual tone test with 1.03 MHz and 1.51 MHz signals at 50 MSPS sampling rate. Low power is also an important aspect in portable wireless devices. For 10.06 MHz signal and 100 MSPS sampling frequency, the power dissipation of the DAC is 20.74 mW with 1.8 V supply.     

Directional distribution of the ambient neutron dose equivalent from 145-MeV ¹⁹F projectiles incident on thick Al target

The directional distribution of the ambient neutron dose equivalent from 145-MeV (19)F projectiles bombarding a thick aluminium target is measured and analysed. The measurements are carried out with a commercially available dose equivalent meter at 0°, 30°, 60° and 90° with respect to the beam direction. The experimental results are compared with calculated doses from EMPIRE nuclear reaction code and different empirical formulations proposed by others. The results are also compared with the measured data obtained from an earlier experiment at a lower projectile energy of 110 MeV for the same target-projectile combination.     

Physicochemical Properties of L-Alanine in Aqueous Silver Sulphate Solutions at (298.15, 308.15, and 318.15)?K

Apparent molar volumes ${(\varphi_V)}$ and viscosity B coefficients for L-alanine in (0.005, 0.010, 0.015, and 0.020) mol · dm^?3 aqueous silver sulphate (Ag₂SO₄) solutions were determined from the solution density and viscosity measurements at (298.15, 308.15, and 318.15) K as a function of amino acid concentration. The standard partial molar volumes ${(\varphi_V^0)}$ and experimental slopes ${(S_V^\ast )}$ obtained from the Masson equation were interpreted in terms of solute?Csolvent and solute?Csolute interactions, respectively. To analyze solution viscosities in terms of viscosity B coefficients, the Jones?CDole equation was applied. The structure-making or -breaking ability of the amino acid has also been discussed in terms of the sign of ${(\delta^{2}\varphi_V^0/\delta T^{2})_{P}}$ . The activation parameters of viscous flow for the ternary solutions were also derived and explained in terms of transition state theory.     

Micelle-assisted bilayer formation of cetyltrimethylammonium bromide thin films studied with combinatorial spectroscopic ellipsometry and quartz crystal microbalance techniques

We report on a combinatorial approach to study the formation of ultra-thin organic films using in-situ spectroscopic ellipsometry and quartz crystal microbalance methods. In contrast to the quartz crystal microbalance, which is sensitive to the total mass attached to the surface, including coupled and entrapped solvent, spectroscopic ellipsometry only measures the amount of adsorbent on the surface. By using these two techniques in tandem, we define and determine the solvent fraction of cetyltrimethylammonium bromide thin films adsorbed onto a gold-coated quartz crystal. Cetyltrimethylammonium bromide thin films grown from aqueous solutions above the critical micelle concentration reveal critical phases in thickness and porosity evolution. We relate these effects to the mechanisms of formation and removal and the structure of cetyltrimethylammonium bromide films, which we determine to have systemic defects due to the presence of micelles.     

Optimization of enzymatic process parameters for increased juice yield from carrot (Daucus carota L.) using response surface methodology

The effects of enzyme concentration (50–650 mg/kg grated carrot), pectolytic and cellulolytic enzyme ratio (3:7–7:3), incubation time (30–150 min) and temperature (25–65 °C) on juice recovery and viscosity from grated carrot were studied. A central composite rotatable design (CCRD) was used in designing the treatment combinations of four variables at five levels. The process involved in treating the blanched grated carrot with mixture of crude pectolytic enzyme from Aspergillus foetidus and crude cellulolytic enzyme from Trichoderma ressi, keeping the samples at the desired time, followed by extraction of juice. Enzyme-treated grated carrot sample showed increased juice recovery as compared to control. A second-order response surface model adequately fitted the data. All the variables affected juice recovery and viscosity significantly. Enzyme concentration, pectolytic and cellulolytic enzyme ratio, incubation time and temperature had total and combined effect at linear, square and interactive level on both responses. The optimum condition was enzyme concentration, 210.7 mg/kg of grated carrot; pectolytic and cellulolytic enzyme ratio, 3.84:6.16; incubation time, 130 min and incubation temperature 47 °C. Under the optimal conditions, juice extracted from enzyme-treated grated carrot was 74.3% having juice viscosity 1.07 cP, corresponding to the increase in yield by 13.95% and decrease in viscosity by 0.45 cP.     

Adhesion and Debonding of Soft Elastic Films on Rough and Patterned Surfaces

With the help of simulations based on energy minimization, we have studied the effect of roughness of a rigid contactor with sinusoidal and step patterns on the adhesion-debonding cycle of a soft thin elastic film. The surface instability engendered by attractive forces between the contactor and the film produces a regularly spaced array of columns in the bonding phase. The inter-column spacing is governed largely by periodicity of the contactor pattern. Decreased periodicity of the pattern favors intermittent collapse of columns rather than a continuous peeling of contact zones. An increase in the amplitude of roughness decreases the maximum force required for debonding and increases the snap-off distance. The net effect results in a reduced work for debonding. Introduction of noise and increased step-size in simulations decreases the pull-off force and the snap-off distance, as in the case of a smooth contactor. Finally the study reveals that a patterned contactor can be used as a potential template in the patterning of soft interfaces.