Does size matter? Comparative population genetics of two butterflies with different wingspans

The dispersal ability of a species is central to its biology, affecting other processes like local adaptation, population and community dynamics, and genetic structure. Among the intrinsic, species-specific factors that affect dispersal ability in butterflies, wingspan was recently shown to explain a high amount of variance in dispersal ability. In this study, a comparative approach was adopted to test whether a difference in wingspan translates into a difference in population genetic structure. Two closely related butterfly species from subfamily Satyrinae, family Nymphalidae, which are similar with respect to all traits that affect dispersal ability except for wingspan, were studied. Melanitis leda (wingspan 60-80 mm) and Ypthima baldus (wingspan 30-40 mm) were collected from the same areas along the Western Ghats of southern India. Amplified fragment length polymorphisms were used to test whether the species with a higher wingspan (M. leda) exhibited a more homogenous population genetic structure, as compared to a species with a shorter wingspan (Y. baldus). In all analyses, Y. baldus exhibited greater degree of population genetic structuring. This study is one of the few adopting a comparative approach to establish the relationship between traits that affect dispersal ability and population genetic structure.

Thermoelectric properties of Co substituted synthetic tetrahedrite

Transition metal atom (Co) substituted synthetic tetrahedrite compounds Cu12-xCoxSb4S13 (x = 0, 0.5, 1.0, 1.5, 2.0) were prepared by solid state synthesis. X-Ray Diffraction (XRD) patterns revealed tetrahedrite as the main phase, whereas for the compounds with x = 0, 0.5 a trace of impurity phase Cu3SbS4 was observed. The surface morphology showed a large grain size with low porosity, which indicated appropriate compaction for the hot pressed samples. The phase purity, as monitored by Electron Probe Micro Analysis (EPMA) is in good agreement with the XRD data. The elemental composition for all the compounds almost matched with the nominal composition. The X-ray Photoelectron Spectroscopy (XPS) data showed that Cu existed in both +1 and +2 states, while Sb exhibited +3 oxidation states. Elastic modulus and hardness showed a systematic variation with increasing Co content. The electrical resistivity and Seebeck coefficient increased with increase in the doping content due to the decrease in the number of carriers caused by the substitution of Co2+ on the Cu1+ site. The positive Seebeck coefficient for all samples indicates that the dominant carriers are holes. A combined effect of resistivity and Seebeck coefficient leads to the maximum power factor of 1.76 mW m(-1) K-2 at 673 K for Cu11.5Co0.5Sb4S13. This could be due to the optimization in the carrier concentration by the partial substitution of Co2+ on both the Cu1+ as well as Cu2+ site at the same doping levels, which is also supported by the XPS data. The total thermal conductivity systematically decreased with increase of doping content as it is mainly influenced by the decrease of carrier thermal conductivity. The maximum thermoelectric figure of merit zT = 0.98 was obtained at 673 K for Cu11.5Co0.5Sb4S13. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A low-power, low-cost soil-moisture sensor using dual-probe heat-pulse technique

This paper presents the development and testing of an integrated low-power and low-cost dual-probe heat-pulse (DPHP) soil-moisture sensor in view of the electrical power consumed and affordability in developing countries. A DPHP sensor has two probes: a heater and a temperature sensor probe spaced 3 mm apart from the heater probe. Supply voltage of 3.3V is given to the heater-coil having resistance of 33 Omega power consumption of 330 mW, which is among the lowest in this category of sensors. The heater probe is 40 mm long with 2 mm diameter and hence is stiff enough to be inserted into the soil. The parametric finite element simulation study was performed to ensure that the maximum temperature rise is between 1 degrees C and 5 degrees C for wet and dry soils, respectively. The discrepancy between the simulation and experiment is less than 3.2%. The sensor was validated with white clay and tested with red soil samples to detect volumetric water-content ranging from 0% to 30%. The sensor element is integrated with low-power electronics for amplifying the output from thermocouple sensor and TelosB mote for wireless communication. A 3.7V lithium ion battery with capacity of 1150 mAh is used to power the system. The battery is charged by a 6V and 300 mA solar cell array. Readings were taken in 30 min intervals. The life-time of DPHP sensor node is around 3.6 days. The sensor, encased in 30 mm x 20 mm x 10 mm sized box, and integrated with electronics was tested independently in two separate laboratories for validating as well as investigating the dependence of the measurement of soil-moisture on the density of the soil. The difference in the readings while repeating the experiments was found out to be less than 0.01%. Furthermore, the effect of ambient temperature on the measurement of soil-moisture is studied experimentally and computationally. (C) 2015 Elsevier B.V. All rights reserved.

Self-assembly of Metallamacrocycles Employing a New Benzil-based Organometallic Bisplatinum(II) Acceptor

A benzil-based semi-rigid dinuclear organometallic acceptor 4,4'-bistrans-Pt(PEt3)(2)(NO3)(ethynyl)]benzil (bisPt-NO3) containing a Pt-ethynyl functionality was synthesized in good yield and characterized by multinuclear NMR (H-1, P-31, and C-13), electrospray ionization mass spectrometry (ESI-MS), and single-crystal X-ray diffraction analysis of the iodide analogue bisPt-I. The stoichiometric (1:1) combination of the acceptor bisPt-NO3 separately with four different ditopic donors (L-1-L-4; L-1 = 9-ethyl-3,6-di(1H-imidazol-1-yl)-9H-carbazole, L-2 = 1,4-bis((1H-imidazol-1-yl)methyl)benzene, L-3 = 1,3-bis((1H-imidazol-1-yl)methyl)benzene and L-4 = 9,10-bis((1H-imidazol-1-yl) methyl)anthracene) yielded four 2 + 2] self-assembled metallacycles M-1-M-4 in quantitative yields, respectively. All these newly synthesized assemblies were characterized by various spectroscopic techniques (NMR, IR, ESI-MS) and their sizes/shapes were predicted through geometry optimization employing the PM6 semi-empirical method. The benzil moiety was introduced in the backbone of the acceptor bisPt-NO3 due to the interesting structural feature of long carbonyl C-C bond (similar to 1.54 angstrom), which enabled us to probe the role of conformational flexibility on size and shapes of the resulting coordination ensembles.

Dispersible crystalline nanobundles of YPO4 and Ln (Eu, Tb)-doped YPO4: rapid synthesis, optical properties and bio-probe applications

Undoped and Ln(3+) (Eu and Tb)-doped crystalline nanobundles of YPO4 were prepared by a facile microwave-assisted route with water as a solvent and without using any surfactant. TEM investigations reveal that the as-prepared powder consists of lenticular-shaped nanobundles (similar to 100 nm in diameter) made of very small nanorods with diameter less than 10 nm and length varying from 20 to 50 nm. Each nanorod in turn is single crystalline, as revealed by HRTEM imaging. The as-prepared nanobundles are easily dispersible in various solvents, especially water, without any surface functionalization, which is critical for various bio-probe applications like cell and tissue imaging. The Eu- and Tb-doped YPO4 nanobundles show good photoluminescence properties and were further evaluated for their use as fluorescent biolabels. Our results show that HeLa cells labelled with Eu- and Tb-doped YPO4 nanobundles show bright red (Eu) and green (Tb) intracellular luminescence under a confocal microscope. Concentration-and time-dependent MTT cell viability assays show that the nanobundles show low toxicity towards cells which makes them promising in bioimaging field.

Strategy for Obtaining Bimodal Bubble Size Distribution in Water Blown Polyurethane Foams

Polyurethane foams with multimodal cell distribution exhibit superior mechanical and thermal properties. A technique for generating bimodal bubble size distribution exists in the literature, but it uses supercritical conditions. In the present work, an alternative based on milder operating conditions is proposed. It is a modification of reaction injection molding (RIM), using reactants already seeded with bubbles. The number density of the seeds determines if two nucleating events can occur. A bimodal bubble size distribution is obtained when this happens A mathematical model is used to test this hypothesis by simulating water blown free rise polyurethane foams. The effects of initial concentration of bubbles, temperature of the reactants, and the weight fraction of water are studied. The study reveals that for certain concentrations of initial number of bubbles, when initial temperature and weight fraction of water are high, it is possible to obtain a second nucleation event, leading to bimodal bubble size distribution.

Single-step, size-controlled synthesis of colloidal silver nanoparticles stabilized by octadecylamine

A single step process for the synthesis of size-controlled silver nanoparticles has been developed using a bifunctional molecule, octadecylamine (ODA). Octadecylamine complexes to Ag+ ions electrostatically, reduce them, and subsequently stabilizes the nanoparticles thus formed. Hence, octadecylamine simultaneously functions as both a reducing and a stabilizing agent. The amine-capped nanoparticles can be obtained in the form of dry powder, which is readily redispersible in aqueous and organic solvents. The particle size, and the nucleation and growth kinetics of silver nanoparticles could be tuned by varying the molar ratio of ODA to AgNO3. The UV-vis spectra of nanoparticles prepared with different concentrations of ODA displayed the well-defined plasmon band with maximum absorption around 425 nm. The formation of silver metallic nanoparticles was confirmed by their XRD pattern. The binding of ODA molecule on the surface of silver has been studied by FT-IR and NMR spectroscopy. The formation of well-dispersed spherical Ag nanoparticles has been confirmed by TEM analysis. The particle size and distribution are found to be dependent on the molar concentration of the amine molecule. Open aperture z-scans have been performed to measure the nonlinearity of Ag nanoparticles. (C) 2015 Published by Elsevier B.V.

Boron-doped carbon nanoparticles: Size-independent color tunability from red to blue and bioimaging applications

Here, we report the hydrothermal synthesis of boron-doped CNPs (B-CNPs) with different size/atomic percentage of doping and size-independent color tunability from red to blue. The variation of size/atomic percentage of B is achieved by simply varying the reaction time, while the color tunability is obtained by diluting the solution. With dilution, the luminescence spectra are not only blue-shifted, the intensity increases as well. The huge blue-shift in the emission energy (similar to 1 eV) is believed to be due to the increase in the interparticle distance. The quantum yield with optimum dilution is found to increase with boron doping though it is very low as compared to CNPs and nitrogen-doped CNPs. Finally, we show that B-CNPs with a quantum yield of 0.5% can be used for bioimaging applications. (C) 2015 Elsevier Ltd. All rights reserved.

Size Effects on Strength in the Transition from Single-to-Polycrystalline Behavior

During the transition from single crystalline to polycrystalline behavior, the available data show the strength increasing or decreasing as the number of grains in a cross section is reduced. Tensile experiments were conducted on polycrystalline Ni with grain sizes (d) between 16 and 140 mu m and varying specimen thickness (t), covering a range of lambda (-t/d) between similar to 0.5 and 20. With a decrease in lambda, the data revealed a consistent trend of strength being independent of lambda at large lambda, an increase in strength, and then a decrease in strength. Microstructural studies revealed that lower constraints enabled easier rotation of the surface grains and texture evolution, independent of the specimen thickness. In specimen interiors, there was a greater ease of rotation in thinner samples. Measurements of misorientation deviations within grains revealed important differences in the specimen interiors. A simple model is developed taking into account the additional geometrically necessary dislocations due to variations in the behavior of surface and interior grains, leading to additional strengthening. A suitable combination of this strengthening and surface weakening can give rise to wide range of possibilities with a decrease in lambda, including weakening, strengthening, and strengthening and weakening.

Probing Photoexcited Carriers in a Few-Layer MoS2 Laminate by Time-Resolved Optical Pump-Terahertz Probe Spectroscopy

We report the dynamics of photoinduced carriers in a free-standing MoS2 laminate consisting of a few layers (1-6 layers) using time-resolved optical pump-terahertz probe spectroscopy. Upon photoexcitation with the 800 nm pump pulse, the terahertz conductivity increases due to absorption by the photoinduced charge carriers. The relaxation of the non-equilibrium carriers shows fast as well as slow decay channels, analyzed using a rate equation model incorporating defect-assisted Auger scattering of photoexcited electrons, holes, and excitons. The fast relaxation time occurs due to the capture of electrons and holes by defects via Auger processes, resulting in nonradiative recombination. The slower relaxation arises since the excitons are bound to the defects, preventing the defect-assisted Auger recombination of the electrons and the holes. Our results provide a comprehensive understanding of the non-equilibrium carrier kinetics in a system of unscreened Coulomb interactions, where defect-assisted Auger processes dominate and should be applicable to other 2D systems.

Gauge invariance in the theoretical description of time-resolved angle-resolved pump/probe photoemission spectroscopy

Nonequilibrium calculations in the presence of an electric field are usually performed in a gauge, and need to be transformed to reveal the gauge-invariant observables. In this work, we discuss the issue of gauge invariance in the context of time-resolved angle-resolved pump/probe photoemission. If the probe is applied while the pump is still on, one must ensure that the calculations of the observed photocurrent are gauge invariant. We also discuss the requirement of the photoemission signal to be positive and the relationship of this constraint to gauge invariance. We end by discussing some technical details related to the perturbative derivation of the photoemission spectra, which involve processes where the pump pulse photoemits electrons due to nonequilibrium effects.

Growth mechanism of the interdiffusion zone between platinum modified bond coats and single crystal superalloys

Pt-modified beta-NiAl bond coats are applied over the superalloys for oxidation protection in jet engine applications. However, as shown in this study, it also enhances the growth of the interdiffusion zone developed between the bond coat and the superalloy along with brittle precipitates. Location of the Kirkendall plane indicates that a precipitate free sublayer grows from the bond coat, whereas another sublayer grows from the superalloy containing very high volume fraction of precipitates. With increasing Pt content, thickness of both the sublayers increases because of an increase in diffusion rates of the components. Quantitative electron probe microanalysis indicates high concentration of refractory components in the precipitates. Transmission electron microscopy shows that Rene N5 superalloy produces TCP phases mu and P, whereas CMSX-4 superalloy produces mu and sigma in the interdiffusion zone. With increasing Pt content in the bond coat, the average size of the precipitates decreases when coupled with Rene N5. Precipitates become much finer when the same bond coats are coupled with CMSX-4. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Growth mechanism of the interdiffusion zone between platinum modified bond coats and single crystal superalloys

Pt-modified beta-NiAl bond coats are applied over the superalloys for oxidation protection in jet engine applications. However, as shown in this study, it also enhances the growth of the interdiffusion zone developed between the bond coat and the superalloy along with brittle precipitates. Location of the Kirkendall plane indicates that a precipitate free sublayer grows from the bond coat, whereas another sublayer grows from the superalloy containing very high volume fraction of precipitates. With increasing Pt content, thickness of both the sublayers increases because of an increase in diffusion rates of the components. Quantitative electron probe microanalysis indicates high concentration of refractory components in the precipitates. Transmission electron microscopy shows that Rene N5 superalloy produces TCP phases mu and P, whereas CMSX-4 superalloy produces mu and sigma in the interdiffusion zone. With increasing Pt content in the bond coat, the average size of the precipitates decreases when coupled with Rene N5. Precipitates become much finer when the same bond coats are coupled with CMSX-4. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Thermal co-reduction approach to vary size of silver nanoparticle: its microbial and cellular toxicology

In recent years, silver nanoparticles (AgNPs) have attracted considerable interest in the field of food, agriculture and pharmaceuticals mainly due to its antibacterial activity. AgNPs have also been reported to possess toxic behavior. The toxicological behavior of nanomaterials largely depends on its size and shape which ultimately depend on synthetic protocol. A systematic and detailed analysis for size variation of AgNP by thermal co-reduction approach and its efficacy toward microbial and cellular toxicological behavior is presented here. With the focus to explore the size-dependent toxicological variation, two different-sized NPs have been synthesized, i.e., 60 nm (Ag60) and 85 nm (Ag85). A detailed microbial toxicological evaluation has been performed by analyzing minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), diameter of inhibition zone (DIZ), growth kinetics (GrK), and death kinetics (DeK). Comparative cytotoxicological behavior was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. It has been concluded by this study that the size of AgNPs can be varied, by varying the concentration of reactants and temperature called as ``thermal co-reduction'' approach, which is one of the suitable approaches to meet the same. Also, the smaller AgNP has shown more microbial and cellular toxicity.

Perturbation of nucleo-cytoplasmic transport affects size of nucleus and nucleolus in human cells

Size regulation of human cell nucleus and nucleolus are poorly understood subjects. 3D reconstruction of live image shows that the karyoplasmic ratio (KR) increases by 30-80% in transformed cell lines compared to their immortalized counterpart. The attenuation of nucleo-cytoplasmic transport causes the KR value to increase by 30-50% in immortalized cell lines. Nucleolus volumes are significantly increased in transformed cell lines and the attenuation of nucleo-cytoplasmic transport causes a significant increase in the nucleolus volume of immortalized cell lines. A cytosol and nuclear fraction swapping experiment emphasizes the potential role of unknown cytosolic factors in nuclear and nucleolar size regulation.