Volumetric quantification of fluid flow reveals fish's use of hydrodynamic stealth to capture evasive prey

In aquatic ecosystems, predation on zooplankton by fish provides a major pathway for the transfer of energy to higher trophic levels. Copepods are an abundant zooplankton group that sense hydromechanical disturbances produced by approaching predators and respond with rapid escapes. Despite this capability, fish capture copepods with high success. Previous studies have focused on the predatory strike to elucidate details of this interaction. However, these raptorial strikes and resulting suction are only effective at short range. Thus, small fish must closely approach highly sensitive prey without triggering an escape in order for a strike to be successful. We use a new method, high-speed, infrared, tomographic particle image velocimetry, to investigate three-dimensional fluid patterns around predator and prey during approaches. Our results show that at least one planktivorous fish (Danio rerio) can control the bow wave in front of the head during the approach and consumption of prey (copepod). This alters hydrodynamic profiles at the location of the copepod such that it is below the threshold required to elicit an escape response. We find this behaviour to be mediated by the generation of suction within the buccopharyngeal cavity, where the velocity into the mouth roughly matches the forward speed of the fish. These results provide insight into how animals modulate aspects of fluid motion around their bodies to overcome escape responses and enhance prey capture.     

Phase Evolution in the AuCu/Sn System by Solid-State Reactive Diffusion

The interfacial reactions between several Au(Cu) alloys and pure Sn were studied experimentally at 200°C. Amounts of Cu in the AuSn₄ and AuSn₂ phases were as low as 1 at.%. On the basis of these experimental results there is no continuous solid solution between (Au,Cu)Sn and (Cu,Au)₆Sn₅. The copper content of (Au,Cu)Sn was determined to be approximately 7–8 at.%. Substantial amounts of Au were present in the (Cu,Au)₆Sn₅ and (Cu,Au)₃Sn phases. Two ternary compounds were formed, one with stoichiometry varying from (Au_40.5Cu₃₉)Sn_20.5 to (Au_20.2Cu_59.3)Sn_20.5 (ternary “B”), the other with the composition Au₃₄Cu₃₃Sn₃₃ (ternary “C”). The measured phase boundary compositions of the product phases are plotted on the available Au–Cu–Sn isotherm and the phase equilibria are discussed. The complexity and average thickness of the diffusion zone decreases with increasing Cu content except for the Au(40 at.%Cu) couple.     

Fabrication,physiochemical and optoelectronic characterization of SiO2/CdS core–shell nanostructures

Silica/CdS core–shell nanostructures have been developed using a simple wet chemical route. This method utilizes silica spheres formation followed by successive ionic layer adsorption and reaction method assisted CdS shell layer formation. The morphological studies revealed the uniformity in size distribution with core size of 250 nm and shell thickness of 9 nm. The electron microscopic images also indicate the irregular morphology of CdS shell layer. The structural studies indicate the simple cubic system of CdS shell with no other trace for impurities in the crystal structure. This CdS layer exhibit the band gap energy of 2.66 eV, due to weak quantum confinement and numerous defects presence. The studies on room temperature photoluminescence measurement indicate the emission properties and the corresponding electronic energy levels of defect states. Further, the physiochemical understanding of core–shell formation mechanism clearly matches with the motive behind the defects present in the CdS shell layer.     

Thermoelectric properties of Zn doped Cu2SnSe3

Zn doped ternary compounds Cu₂Zn_xSn_1−xSe₃ (x = 0, 0.025, 0.05, 0.075) were prepared by solid state synthesis. The undoped compound showed a monoclinic crystal structure as a major phase, while the doped compounds showed a cubic crystal structure confirmed by powder XRD (X-Ray Diffraction). The surface morphology and elemental composition analysis for all the samples were studied by SEM (Scanning Electron Microscopy) and EPMA (Electron Probe Micro Analyzer), respectively. SEM micrographs of the hot pressed samples showed the presence of continuous and homogeneous grains confirming sufficient densification. Elemental composition of all the samples revealed an off-stoichiometry, which was determined by EPMA. Transport properties were measured between 324 K and 773 K. The electrical resistivity decreased up to the samples with Zn content x = 0.05 in Cu₂Zn_xSn_1−xSe₃, and slightly increased in the sample Cu₂Zn_0.075Sn_0.925Se₃. This behavior is consistent with the changes in the carrier concentration confirmed by room temperature Hall coefficient data. Temperature dependent electrical resistivity of all samples showed heavily doped semiconductor behavior. All the samples exhibit positive Seebeck coefficient (S) and Hall coefficient indicating that the majority of the carriers are holes. A linear increase in Seebeck coefficient with increase in temperature indicates the degenerate semiconductor behavior. The total thermal conductivity of the doped samples increased with a higher amount of doping, due to the increase in the carrier contribution. The total and lattice thermal conductivity of all samples showed 1/T dependence, which points toward the dominance of phonon scattering at high temperatures. The maximum 1/TZT = 0.48 at 773 K was obtained for the sample Cu₂SnSe₃ due to a low thermal conductivity compared to the doped samples.     

Microwave assisted hydrothermal synthesis and characterization of ZnO–TNT composites

TiO₂ nanotubes with different contents of ZnO (3–40 wt.% ZnO) have been successfully synthesized by microwave assisted hydrothermal process by using commercial TiO₂-P25 as a precursor. The phase and crystallinity of the obtained ZnO–TNT were analyzed by X-ray Diffraction (XRD). The surface area of the ZnO–TNT was determined by BET method. The effect of the different contents of ZnO on morphology of TiO₂ nanotubes was investigated by SEM and TEM. Optical properties and band gap energy of ZnO–TNT were calculated by using UV–vis DRS spectroscopy and modified Kubelka–Munk equation. Photocatalytic performance of ZnO–TNT was investigated by degradation of rhodamine B (RhB) dye under UV and visible light irradiation. Increasing ZnO content in TNT gradually decreased the diameter and length of nanotubes. Furthermore, addition of 40 wt.% ZnO into the TNT exceeded the saturation limit of ion exchangeability of Zn²⁺ and Na⁺ ions and aggregation of finely dispersed ZnO particles on the surface of TNT were observed. The ZnO–TNT has shown relatively larger band gap energies than that of TiO₂-P25. However, ZnO–TNT has shown considerable increase in photo-activity for degradation of RhB dye in visible light as compared to UV light irradiation.     

Synthesis and properties of siloxane-crosslinked polyurethane-urea/silica hybrid films from castor oil

A novel hybrid diol (HD) crosslinker has been synthesized with hydrolyzable –Si–OR groups from 3-amino propyl trimethoxy silane and 3-glycidoxy propyl trimethoxy silane. Its chemical structure was confirmed by Fourier transform infrared spectroscopy, ¹H and ¹³C nuclear magnetic resonance spectroscopy to introduce it as a crosslinker in the castor oil, a renewable resource, to develop functional organic inorganic hybrid coatings. A series of castor oil-based organic–inorganic hybrid materials were prepared from castor oil, isophorone diisocyanate, and the different weight percentages of synthesized HD. Dynamic mechanical thermal analysis, thermogravimetric analysis, differential scanning calorimetry, and the universal testing machine were employed to characterize the hybrid films. The measured properties were found to be strongly influenced by the weight ratio of HD to the castor oil-based polyurethanes. The glass transition temperatures (T _g) for the cured hybrid films were found to be 26–72°C. Antibacterial activity, in vitro hydrolytic degradation, and swelling properties of the hybrid films have been studied. The cured hybrid films exhibited excellent antibacterial activity, which was enhanced with addition of the HD. The alkoxy silane-crosslinked castor oil-based coatings have shown better mechanical and viscoelastic properties in comparison to the control (uncrosslinked castor oil-based polyurethane-urea) coatings. The results showed that the weight percent of the HD is the main factor that controls the thermal, antimicrobial, mechanical, swelling, and degradation properties of these hybrid films.     

Influence of laminate thickness reduction on the deformation mechanism of coextruded multilayered PC/PMMA films

The influence of the morphology of multilayered composites of poly(methyl‐methacrylate) (PMMA) and polycarbonate (PC) fabricated by layer multiplying coextrusion technique on their mechanical and especially their micromechanical deformation behavior was investigated. Electron microscopic studies revealed that the PC/PMMA multilayered composites have a well‐oriented, uniform, and continuous layered architecture. With decreasing layer thickness of each polymer in the composite, the elongation at break of the films was found to increase significantly which was correlated with a transition from a two‐component behavior (for single‐layer thickness of ≥8 μm) to an one‐component behavior (for single‐layer thickness of ≤250 nm). Rheo‐optical measurements using FTIR spectroscopy revealed that the molecular orientation during stretching of the PMMA phase remains unchanged for all the investigated films, whereas the PC orientation function decreases with decreasing layer thickness. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Proliposomes of lisinopril dihydrate for transdermal delivery: Formulation aspects and evaluation

We formulated and evaluated proliposomal gel of relatively low bioavailable drug lisinopril dihydrate (LDH) for transdermal delivery. Several proliposomal gel formulations of lisinopril dihydrate were prepared by modified coacervation phase separation method and examined for formation of liposomes by optical microscope and characterized by transmission electron microscopy. The formulations were evaluated for size, zeta potential, entrapment efficiency, rheological behavior, ex vivo drug permeation, skin irritation and stability. Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) studies were performed to understand the phase transition behavior and mechanism for skin permeation, respectively. The microscopic examination revealed the formation of liposomes from proliposomal gel, and the size of the vesicles was found to be in the range of 385 nm to 635 nm. Entrapment efficiency was high for the formulation containing greater amounts of phosphatidylcholine. The DSC studies indicated the amorphous form of LDH in proliposomal gel formulation. Ex vivo permeation studies revealed sustained permeation of drug from proliposomal gels studied. The stability studies reveal that the proliposomal formulations are more stable when stored at refrigeration temperature (4 °C). In conclusion, proliposomal gels offer potential and prove to be efficient carriers for improved and sustained transdermal delivery of lisinopril dihydrate.     

Effect of Co and V complexes on polymerization of methyl methacrylate initiated by AlEt2Br‐TEMPO catalyst

2,2,6,6‐Tetramethyl piperidinoxy (TEMPO) activated with diethyl aluminum bromide was employed as an initiator system for methyl methacrylate polymerization. Effect of addition of Co(acac)₃ and VO(acac)₂ complexes to the initiators system on methyl methacrylate polymerization were studied in benzene solvent. Various reaction parameters such as Al/TEMPO, monomer concentration, reaction temperature and time applied to the polymerization were investigated. The polymer yields, molecular weight and molecular weight distributions can be controlled with the addition of Co(acac)₃ to the initiator system. PMMA's of molecular weight distributions, as low as 1.10 was obtained under relatively mild conditions, in the temperature range 40–60°C in benzene solvent. However, Co and V complexes did not influence the micro structure of the PMMA's formed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis,structure and properties of polyimide–silica hybrid composites based on biphenyltetracarboxylic dianhydride

A simple and efficient way of synthesizing nanocomposite films using a dispersion technique is reported, with the resulting films having improved mechanical and thermal properties. Nano‐SiO₂ was used in a biphenyltetracarboxylic dianhydride‐based poly(amic acid) precursor and found to be dispersed up to 7 wt% without any additives. The composites were cast to make 10 µm solid films to establish structure and property relationships between liquid and solid film. The structures of the liquid composite materials were studied using NMR and Fourier transform infrared spectroscopy. Solid film properties such as tensile strength, contact angles and thermal behaviour were evaluated for comparison. The properties of the composite films were found to be enhanced compared to polyimide film itself. Atomic force microscopy and macroscale mechanical measurements showed that composite films with more dipolar bonding interactions have higher elastic moduli and are more deformable. They yield higher adhesion energies, and therefore composite coatings offer greater adhesion. There was a limitation in the film formation beyond 5 wt% of silica. Copyright © 2011 Society of Chemical Industry