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The identification of bivalve larvae and early postlarvae in plankton and benthic samples has long been a challenge, hampering both basic and applied research efforts in marine, estuarine, and freshwater environments. The usefulness of published optical micrographs of the early life-history stages of bivalves is limited because of the great morphological similarity of the imaged articulated shells, particularly at the early (straight-hinge) developmental stages. While a number of techniques have been refined in recent years and show promise for use in routine identifications of larval and post-larval bivalves (e.g., single-step nested multiplex polymerase chain reaction; in situ hybridization protocols through color coding with taxon-specific, dye-labeled DNA probes; coupled fluorescence in situ hybridization and cell sorting; and image analysis techniques using species-specific shell birefringence patterns under polarized light), no adequate comprehensive reference source exists that accurately depicts the morphology and morphometry of the shells of larval and post-larval stages of target bivalve species in a consistent format to assist in identification of such stages. To this end, scanning electron micrograph (SEM) sequences are presented of the disarticulated shell valves of laboratory-reared larval and post-larval stages of 56 species of bivalve molluscs from a wide spectrum of marine, estuarine, and freshwater habitats. Emphasis is placed on the usefulness of the morphology and morphometries of consistently-oriented, disarticulated shell valves and associated hinge structures in discriminating the early life-history stages of these various bivalve species. Although the scanning electron micrograph sequences presented accurately depict the gross morphologies/morphometries and hinge structures of the disarticulated shell valves of the larvae and/or postlarvae of the 56 species of bivalves, it is important to emphasize that a scanning electron microscope is not necessary to observe even fine hinge structures associated with the early ontogenetic stages of these species. Such structures are readily visible using a wide range of optical compound microscopes equipped with high-intensity reflected light sources, although the disarticulated shell valves must be viewed in several planes of focus to discern the often subtle details seen clearly in the scanning electron micrographs. These morphological characters provide researchers with invaluable aids for the routine identification of the early life-history stages of these species isolated from plankton and benthic samples. KEY WORDS: bivalve, larvae, postlarvae, identification, scanning electron microscopy, Part 1 of 3 INTRODUCTION The identification of bivalve larvae and early postlarvae has been important for many ecological research efforts in marine, estuarine, and freshwater environments for over a [...]

Experimental data on the generation and detection of characteristic X-radiation of elements in electron probe microanalysis of dielectric samples in the low vacuum mode without the deposition of conducting coatings are discussed. The main advantage of the considered method of analysis is the stability of the intensity ratio between diagnostic analyte lines in the wide range of currents of the electron probe and gas phase pressure in the chamber in the range 60-130 Pa, sufficient for obtaining undistorted images of the surface of dielectrics. The stability of the intensity ratio ensures obtaining correct data of the quantitative analysis of nonconducting samples without the deposition of conducting coatings. The main features of low-vacuum microanalysis for the range of gas phase pressures used are discussed, which can create additional difficulties in the study. Among such features is a possibility of the manifestation of reflexes of gas-phase elements, significant underestimation of the relative emission intensity from lighter elements in the composition of the studied samples, loss of scanning locality in the analysis of small sites on the sample surface. An example of the correct quantitative elemental analysis of a dielectric surface without the deposition of an electroconductive coating for a number of aluminosilicates is presented. Keywords: X-ray electron probe surface analysis, dielectric materials, effect of charge accumulation, low-vacuum scanning electron microscopy, intensity of characteristic emission line, local surface analysis DOI: 10.1134/S1061934818030103, Energy dispersive X-ray spectroscopy is one of the most efficient and widely applied methods of the rapid determination of the elemental composition of surfaces. Because of their compactness, systems of [...]

Abstract: Amorphous chromium-containing solid nanoparticles and hollow spheres were formed as the intermediate product during the synthesis of [Cr.sub.2][O.sub.3] by gamma radiolysis of dichromate solution. Scanning transmission X-ray microscopy (STXM) [...]

Abstract: Dwarf mistletoes (DM), genus Arceuthobium, are dioecious parasitic flowering plants having prolonged life cycles lasting six years, culminating with explosive discharge of the single seed from the fruit. Arceuthobium [...]

Numerous techniques have focused on the ability of p-sulfonated calix[n]arene to form complexes with tryptophan. Scanning electron microscopy and Fourier transform infrared spectroscopy were utilized to study the organization and molecular structure of different layers of the electrode surface. Scanning electron microscopy results showed that SC4A displayed a cubic structure whereas SC6A and SC8A displayed dendrite structures. The electrochemical properties and potential complex formation between SCnA and tryptophan were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. Cyclic voltammetry experiments showed that the gold electrode was successfully functionalized by self-assembled cysteamine and SC4A. Electrochemical impedance spectroscopy results showed the observation of the tryptophan-SCnA interaction and indicated that SC4A had the highest sensitivity to tryptophan and allowed 2.04 µg [L.sup.-1] tryptophan to be detected. Electrochemical impedance spectroscopy analysis and molecular modeling calculation confirmed that SC4A has higher tryptophan sensitivity than SC6A and SC8A. Key words: Fourier transform infrared spectroscopy, molecular modeling calculation, cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy. De nombreuses techniques ont ete axees sur la capacite des calix[n]arenes p-sulfones a former des complexes avec le tryptophane. La microscopie electronique a balayage et la spectroscopie infrarouge a transformee de Fourier ont ete utilisees pour etudier l'organisation et la structure moleculaire de differentes couches de la surface de l'electrode. Les resultats de la microscopie electronique a balayage ont montre que SC4A presentait une structure cubique alors que SC6A et SC8A possedaient des structures dendritiques. Les proprietes electrochimiques et la formation possible d'un complexe entre SCnA et le tryptophane ont ete caracterisees par voltammetrie cyclique et spectroscopie d'impedance electrochimique. Les experiences de voltammetrie cyclique ont montre que l'electrode en or etait fonctionnalisee avec succes par autoassemblage de cysteamine et de SC4A. Les resultats de la spectroscopie d'impedance electrochimique ont permis d'observer l'interaction tryptophane-SCnA et ont revele que SC4A avait une sensibilite elevee au tryptophane et qu'une concentration en tryptophane de 2,04 µg [L.sup.-1] pouvait etre detectee de cette technique d'analyse. Les calculs de modelisation moleculaire et les resultats de la spectroscopie d'impedance electrochimique ont confirme que SC4A presentait une plus grande sensibilite au tryptophane que SC6A et SC8A. [Traduit par la Redaction] Mots-cles : spectroscopie infrarouge a transformee de Fourier, calculs de modelisation moleculaire, voltammetrie cyclique, spectroscopie d'impedance electrochimique, microscopie electronique a balayage., Introduction As the third major class of host molecules, calixarenes, (1) which are synthesized by the condensation between p-alkylphenol and formaldehyde under basic conditions, have attracted much attention due to [...]

In this study, we investigated the influence of TiO2 content and thickness of polystyrene (PS) template on film-formation behavior of PS/Ti[0.sub.2] composites using fluorescence and ultraviolet-visible techniques in conjunction with scanning electron microscopy. Films were prepared by coating PS templates with various layers of Ti[0.sub.2] using dip-coating method. The results showed that PS latexes present complete film formation on top surface of composites. After extraction of PS, a well-defined interconnected porosity were obtained for thin films when Ti[0.sub.2] content was increased, whereas thick samples did not present any interconnected porous structures above a certain Ti[0.sub.2] layer. POLYM. ENG. SCI., 54:288-302, 2014. © 2013 Society of Plastics Engineers, INTRODUCTION Polymer latexes are being used in a broad range of fields from adhesives, inks, paints, coatings, drug delivery systems, and films to cosmetics (1). In many of these applications, [...]

Immobilization of gold nanoparticles on planar sur-faces is of great interest to many scientific communities; chemists, physicists, biologists, and the various communities working at the interfaces between these disciplines. Controlling the immobilization step, especially nanoparticles dispersion and coverage, is an important issue for all of these communities. We studied the parameters that can influence this interaction, starting with the nature of the terminal chemical function. Thus, we have carefully grafted silanes terminated by either amine or thiol groups starting from aminopropyltriethoxysilane (APTES) or mercaptopropyltriethoxysilane. We also changed the chain length for thiolterminated layers through covalent grafting of mercaptoundecanoic acid (MUA) on APTES-modified layers, and the protocol of nanoparticles deposition to evaluate whether other factors must be taken into consideration to rationalize this interaction. The formed layers were characterized by X-ray photoelectron spectroscopy and gold nanoparticles deposition was monitored by scanning electron microscopy and surface-enhanced Raman scattering. We observed significant differences in terms of nanoparticles dispersion and density depending on the nature of the chemical layer on silicon. The use of ultrasounds during the deposition process was very efficient to limit aggregates formation. The optimal deposition procedures were obtained through the use of APTES and APTES/MUA functionalization. They were compared in terms of coverage, dispersion, and densities of isolated nanoparticles. The APTES/MUA surfaces clearly showed better results that may arise from both the longer chain and the dilution of thiol end groups. Keywords Gold nanoparticles. Silicon surface. Silane grafting. Surface functionalization. XPS. Scanning electron microscopy, Introduction The fabrication of solid substrates with gold nanoparticles assemblies immobilized on their surface is currently the subject of growing interest because of the key role these substrates could play [...]

Poly(benzoxazine-co-urethane) was prepared by melt-blending bisphenol-S/aniline-type benzoxazine (BS-a) with isocyanate-terminated polyurethane (PU) prepoly-mer based on 2,4-toluene diisocyanate and poly(ethylene glycol), followed by thermally activated polymerization of the blend. The copolymerization reaction between BS-a and PU prepolymer was monitored using Fourier transform infrared spectroscopy. The morphology, dynamic mechanical properties, and thermal stability of the poly(benzoxazine-co-urethane) were studied using scanning electron microscopy, dynamic mechanical analysis, and thermogravimetry. Homogeneous morphology is shown in scanning electron micrographs of the fracture surfaces of poly(benzoxa-zine-co-urethane)s with different urethane weight fractions, and the roughness of the surface increases with urethane content increasing. Correspondingly, a single glass transition temperature ([T.sub.g]) is shown on the dynamic mechanical analysis curves of the poly(ben-zoxazine-co-urethane)s, and the [T.sub.g] is higher than that of the polybenzoxazine. With increase in the urethane content, the [T.sub.g] and water absorption of poly(benzoxa-zine-co-urethane) increase, whereas the storage modulus and thermal stability decrease. POLYM. ENG. SCI., 53:2633-2639, 2013. © 2013 Society of Plastics Engineers, INTRODUCTION Benzoxazines is a newly developed class of thermosetting phenolic resins, and they can be used as matrix resins for high-performance composite because their corresponding polybenzoxazines possess many unique advantages, [...]

INTRODUCTION A handful of publications describe the termite abdomen, all from observations by light microscopy (Geyer, 1951; Matsuda, 1976; Tuxen, 1970; Belyaeva, 2006). Scanning electron microscopy could reveal morphological features [...]

In this preliminary study, we demonstrate an environmentally friendly process for the green synthesis of gold nanometre scale particles using the leaf extract from an indigenous Australian plant Eucalyptus macrocarpa as both the stabilising agent and the reducing agent. The synthesis process is straightforward, clean and non-toxic. It also has the advantages of being performed at room temperature and does not need complex processing equipment. Formation of the gold nanometre sized particles was confirmed and characterised by UV-visible spectroscopy, X-ray diffraction, transmission electron microscopy and field emission scanning electron microscopy. The antibacterial activity of the synthesised gold particles was also quantified using the sensitivity method of Kirby--Bauer. Keywords Gold * Nano-particles * Green synthesis * Antibacterial * Eucalyptus macrocarpa, Introduction Metallic nanometre scale particles, in particular colloidal gold nanoparticles (Au NPs), have attracted considerable interest in many fields such as medicine, biotechnology, materials science, photonics and electronics (1-4). The [...]

In this study, nonspinnable short staple cotton fibers were microfibrillated in disc refiner followed by nanofibrillation in high pressure homogenizer and their properties evaluated. The extent of fibrillation was improved by increased number of repeated passes. Refining as a pretreatment process helps to circumvent the fiber clogging problem in homogenizer nozzle. Microfibrillation by 30 passes in refining produced the fibrils of size 416 ± 177 nm and subsequent nanofibrillation by 15 passes in homogenization resulted in 112 ± 49 nm as revealed by scanning electron microscopy. While refining process does not significantly affect the crystalline index of fibers, homogenization reduced it by 10% due to very high shear and impact forces and hydrodynamic cavitation. The degree of polymerization of cotton fibers was reduced significantly (35.4%) during this two-stage process. Fourier transform infrared spectroscopy proved that there is no change in the molecular structure of cotton fibrils during this two-stage fibrillation process. Thus produced nanofibrils having potential application as fillers in composites which can be used for various application food packaging, much films membranes etc. add value to the cotton fibers that are not suitable for spinning in textile industries due to their very short length. POLYM. ENG. SCI., 53:1590-1597, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION Cellulose is a renewable, biodegradable and the most abundant biopolymer available in the biosphere (1) and it is produced in nature at an annual rate of [10.sup.11]-[10.sup.12] tons (2). [...]

Au(111) surfaces modified by exposure to a dilute solution of a Ti(IV)/dithiothreitol ligand to metal charge transfer complex (Ti[(DTT).sub.2]) show a remarkable response to continuous scanning by scanning tunneling microscopy (STM). Vacancy islands on the gold surface, which are formed during the self-assembly of the molecular overlayer, coarsen and even merge during STM scanning at negative sample bias. In certain instances, the vacancy islands even line up to form parallel nanostructures. We believe the effect is due to mechanical interactions between tip and sample, which is enhanced by electrostatic effects. The Ti[(DTT).sub.2] complex is anchored to the gold surface via Au-S bonds, but due to the fact that there are multiple thiol groups, there may be 'uncoordinated' thiols left 'dangling'. The tip-induced modification involves the interaction of the tip with these 'dangling' sulfurs, which in turn causes movement of single complex molecules with the attached sulfur-bonded gold. Under negative sample bias, the electric field weakens the binding between the sulfur-bonded gold atoms and the surrounding gold atoms in the surface allowing for the observed tip-induced dynamics. In contrast with the Ti[(DTT).sub.2] complex, a similar Ti(IV)/3-mercapto-1,2-propanediol complex (Ti[(MPD).sub.2]) does not exhibit any tip-induced effects. In this case, there are no dangling sulfurs to interact with the STM tip. In addition, similarly prepared dithiothreitol, dithiothreitol titanium isopropoxide, and 3-mercapto-1,2-propanediol self-assembled monolayers (without dangling sulfurs) do not exhibit the tip-induced effect. Key words: self-assembled monolayers, scanning tunneling microscopy, nanostructured films, dithiothreitol, titanium isopropoxide. Les surfaces d'Au(111) modifiees par exposition a une solution diluee du complexe de transfert de charge ligand vers metal Ti(IV)/dithiothreitol (Ti[(DTT).sub.2]) presentent une reponse remarquable au balayage continu aumoyen d'unmicroscope a effet tunnel (STM). Les ilots lacunaires formes a la surface de l'or durant l'auto-assemblage de la couche moleculaire superficielle grossissent et fusionnentmeme durant le balayage STMsous tension de polarisation sur l'echantillon negative. Dans certains cas, les ilots lacunaires s'alignent meme pour former des nanostructures paralleles. Nous pensons que l'effet resulte d'interactions mecaniques entre la pointe et l'echantillon et est accentue par des effets electrostatiques. Le complexe Ti[(DTT).sub.2] est ancre a la surface de l'or par des liaisons Au-S, mais comme il existe de multiples groupements thiols, certains de ceux-ci pourraient etre <> et demeurer <>. La modification induite par la pointe met en jeu l'interaction de cette derniere avec ces atomes de souffre <> laquelle, a son tour, cause le mouvement de molecules complexes individuelles avec l'or lie au souffre attache. Sous tension de polarisation negative sur l'echantillon, le champ electrique affaiblit la liaison entre les atomes d'or lies au souffre et les atomes d'or qui les entourent dans la surface, donnant ainsi lieu a la dynamique induite par la pointe que l'on observe. Contrairement au complexe Ti[(DTT).sub.2], le complexe similaire Ti(IV)/3-mercapto-1,2-propanediol (Ti[(MPD).sub.2]) ne manifeste aucun effet induit par la pointe. Dans ce cas, il n'existe pas d'atomes de souffre ballants pour interagir avec la pointe STM. En outre, desmonocouches auto-assemblees de dithiothreitol, de dithiothreitol isopropoxyde de titane et de 3-mercapto-1,2-propanediol (sans atomes de souffre ballants) preparees de maniere similaire ne presentent pas l'effet induit par la pointe. [Traduit par la Redaction] Mots-cles : monocouches auto-assemblees, microscope tunnel a balayage, films nanostructures, dithiothreitol, isopropoxyde de titane., Introduction Titanium dioxide (Ti[O.sub.2]) has many useful electrical and optical properties that make Ti[O.sub.2] thin films attractive for use in a wide variety of current and potential applications. These range [...]

This paper describes selected properties of pure and doped strontium titanate single crystals. Data obtained using optical and cathode-luminescence, X-ray fluorescence, scanning electron microscope measurements of the crystals over plasma treatment, and crystallographic structure related oxidation state of the component and doped ions have been analyzed too. Colour centres in near stoichiometry crystals, quasi-ordered structures of nano-scale size pyramids generated by plasma flow on the surface, and ordered oxygen vacancy structures in the samples are presented in this paper. PACS Nos: 78.70D, 76.30 Nous presentons les resultats d'une recherche sur des proprietes choisies de monocristaux de titanate de strontium purs et dopes. Nous avons analyse aussi des donnees sur la luminescence optique et de cathode, la fluorescence X, des mesures SEM des cristaux traites au plasma et l'etat d'oxydation reliee a la structure cristallographique pour les ions du composant pur et dope. Nous presentons les centres F dans des cristaux pres de la stachiometrie, les structures quasi ordonnees de pyramides a l'echelle nano generees par flux de plasma sur la surface et des lacunes ordonnees d'oxygene dans les echantillons. [Traduit par la Redaction], 1. Introduction Interest in pure and doped oxides similar to SrTi[O.sub.3] (STO) with perovskite-type crystallographic structures--[O.sup.1.sub.h], Pm3m--has been stable for a long time [1-4]. A number of investigations have recently [...]

Five sources of data force extensive revision of ideas about the nature and evolution of monocot xylem: scanning electron microscopy (SEM) studies of thick sections; availability of molecular phylogenies covering a relatively large number of families and genera; information on ecology and habitat; data concerning habit; and observations from xylem physiology. These five new sources of data, absent from the studies of Cheadle, plus added information from light microscopy, lead to a fresh understanding of how xylem has evolved in monocots. Tracheary elements hitherto recorded as vessel elements with scalariform end walls prove in a number of instances, to retain pit membranes (often porous or reticulate) in the end walls. There is not an inexorable progression from 'primitive' to 'specialized' xylem in monocots; apparent accelerations or reversions are also possible. The latter include such changes as the result of production of narrower vessel elements; or production of less metaxylem, which is probably heterochronic in nature (an extreme form of juvenilism). Tracheary elements intermediate between vessel elements and tracheids must be recognized for what they are, and not forced into mutually exclusive categories. Original data on tracheids and various types of vessel elements is related here to ecology and habit of groups such as Asteliaceae, Boryaceae, Cyclanthaceae, Orchidaceae, Pandanaceae, Taccaceae, Typhaceae, dracaenoid Asparagaceae, and Zingiberales. Data from palm xylem shows a nearly unique syndrome of features that can be explained with the aid of information from physiology and ecology. Vessellessness of stems and leaves characterizes a large number of monocot species; the physiological and ecological significance of these is highlighted. An understanding of how nonpalm arborescent monocots combine an all-tracheid stem xylem with addition of bundles and vegetative modifications is attempted. The effect of the disjunction between xylems of adventitious roots and stems, providing a physiologically demonstrated valve ('rectifier') effect is discussed. 'Ecological iteration' has occurred in some monocot lineages, so that early-departing branches in some cases may have more 'specialized' xylem because of entry into xeric habitats, whereas nearby crown groups, which may have retained 'primitive' xylem, probably represent long occupation of mesic habitats. Cheadle's use of xylem for 'negations' of phyletic pathways can no longer be accepted. Symplesiomorphic mesomorphic xylem patterns do characterize many of the earlier-departing branches in the monocots as a whole, however. Cheadle's idea that monocots and non-monocot angiosperms attained vessels independently is improbable in the light of molecular trees for angiosperms. Vessels in roots seem an adaptation to major swings in moisture availability to adventitious roots as compared to taproots. The commonness of all-tracheid plans in stems and leaves in earlier-departing monocot clades is a feature that requires further clarification but is primarily related to the xylem disjunction that adventitious roots have. Secondary vessellessness or something very close to it can be hypothesized for Campynemataceae, Philesiaceae, Taccaceae, and some Orchidaceae. Eleven salient shifts in our conceptual views of monocot xylem are proposed and conclude the paper. Monocot xylem is not a collection of historical information, but a rigorously parsimonious system related to contemporary habits and habitats. Keywords Ecological plant anatomy. Heterochrony. Microstructure. Monocot cambium * Neotracheids * Vessellessness * Xylem evolution, Introduction Evolutionary concepts in plant anatomy are limited by the fields of knowledge available and taken into account. Certainly we have good descriptive accounts of monocot anatomy in general, based [...]

The production of injection-molded parts free from surface appearance defects is of great importance in the manufacturing of high-quality products. A particular surface defect which occurs on components manufactured from an acrylonitrile-butadiene-styrene copolymer (ABS) is here described. The defect has been called ghost marks and is characterized by a local change in gloss or lightness which is only visually detectable in certain viewing angles and conditions of illumination. By means of scanning electron microscopy, small-scale deformations of the surface texture were observed in the area of the defect which in turn alters the light scattering properties of the surface. The light scattering properties were evaluated by means of a multiangle spectrophotometer. The holding pressure during the injection molding process was shown to play a significant role in the formation of the ghost marks possibly imposing forces causing the deformation of the surface texture. The deformations may also occur from nonuniform thermal surface shrinkage during cooling. The type of texture and wall thickness also influences the occurrence of ghost marks. POLYM. ENG. SCI., 52:459-466, 2012. © 2011 Society of Plastics Engineers, INTRODUCTION The perceived quality relates to the impression that a customer gains in the sensory interaction with a product and is of great concern especially in the development and production [...]

Nanoscale semiconductor heterostructures such as tetrapods can be used to mimic light-harvesting processes. We used single-particle light-harvesting action spectroscopy to probe the impact of particle morphology on energy transfer and carrier relaxation across a heterojunction. The generic form of an action spectrum [in our experiments, photoluminescence excitation (PLE) under absorption in CdS and emission from CdSe in nanocrystal tetrapods, rods, and spheres] was controlled by the physical shape and resulting morphological variation in the quantum confinement parameters of the nanoparticle. A correlation between single-particle PLE and physical shape as determined by scanning electron microscopy was demonstrated. Such an analysis links local structural non-uniformities such as CdS bulbs forming around the CdSe core in CdSe/CdS nanorods to a tower probability of manifesting excitation energy-dependent emission spectra, which in turn is probably related to band alignment and electron delocatization at the heterojunction interface. 10.1126/science.1198070

This Article reports the use of scanning electrochemical microscopy (SECM) for the quantitative study of acid-induced dissolution. An ultramicroelectrode (UME) is used to generate a flux of protons galvanostatically just above a sample surface, creating controlled acid challenges relevant to acid erosion. The electrochemical technique produces etch features in the sample, which are characterized by white fight interferometry (WLI). The technique has been applied to bovine enamel where understanding the kinetics of dissolution is important in the context of acid erosion. Dissolution has been observed as a fast process, but the high rates of mass transport in SECM allow the surface kinetics of dissolution to be evaluated. Key attributes of SECM for these studies are the ability to deliver high, controllable, and local acid challenges in a defined way and that multiple dissolution measurements can be performed on one sample, eliminating intersample variability effects. A novel moving boundary finite element model has been designed to describe the etching process, which allows the etch kinetics to be evaluated quantitatively, simply by measuring the size and shape of etch features over time. 10.1021/ac101662h

We describe highly localized electrochemical measurements and imaging using a simple, mobile them pipet cell. Each channel (diameter < 500 nm) of a tapered them pipet is filled with electrolyte solution and a Ag/AgCl electrode, between which a bias is applied, resulting in a conductance current across a thin meniscus of solution at the end of the pipet, which is typically deployed in air or a controlled gaseous environment. When the position of the pipet normal to a surface of interest is oscillated, an oscillating component in the conductance current is generated when the meniscus at the end of the probe comes into contact with the surface and undergoes periodic (reversible) deformation, so as to modulate the solution resistance. This oscillating current component can be used to maintain gentle contact of the solution from the pipet cell with the surface and as a set point for high resolution topographical imaging with the pipet. Simultaneously, the mean conductance current that flows between the pipet channels can be measured and is sensitive to the local nature of the interface, informing one, for example, on wettability and ion flow into or out of the surface investigated. Furthermore, conductor or semiconductor surfaces can be connected as a working electrode, with one of the electrodes in the pipet serving as a quasi-reference electrode. This pipet cell then constitutes part of a dynamic electrochemical cell, with which direct voltammetric--amperometric imaging can be carried out simultaneously with conductance and topographical imaging. This provides multifunctional electrochemical maps of surfaces and interfaces at high spatial resolution. The prospects for the use of this new methodology widely are highlighted through exemplar studies and a brief discussion of future applications. 10.1021/ac102191u

Changes in HeLa cell morphology, membrane permeability, and viability caused by the presence of Triton X-100 (TX100), a nonionic surfactant, were studied by scanning electrochemical microscopy (SECM). No change in membrane permeability was found at concentrations of 0.15 mM or lower during an experimental period of 30 to 60 min. Permeability of the cell membrane to the otherwise impermeable, highly charged hydrophilic molecule ferrocyanide was seen starting at concentrations of TX100 of about 0.17 mM. This concentration level of TX100 did not affect cell viability. Based on a simulation model, the membrane permeability for ferrocyanide molecules passing though the live cell membrane was 6.5 [+ or -] 2.0 x [10.sup.-6] m/s. Cells underwent irreversible permeabilization of the membrane and structural collapse when the TX100 concentration reached the critical micelle concentration (CMC), in the range of 0.19 to 0.20 mM. The impermeability of ferrocyanide molecules in the absence of surfactant was also used to determine the height and diameter of a single living cell with the aid of the approach curve and probe scan methods in SECM. live and intact cells | hydrophilic molecules | Comsol Multiphysics Simulation doi/ 10.1073/pnas.1011614107

Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability. biological imaging | Schottky emission source | structural dynamics | nanomaterials imaging doi/ 10.1073/pnas.1009321107

A new scanning electrochemical microscopy (SECM) tip positioning method that allows surface topography and activity to be resolved simultaneously and independently is presented. The tip, controlled by a piezoelectric positioner operated in closed loop, is oscillated normal to the substrate surface. Changes in the oscillation amplitude, caused by the intermittent contact (IC) of the tip with the substrate surface, are used as a feedback signal to control the tip height. The method is illustrated with amperometric feedback approach curve measurements to inert (insulating) and active (conducting) substrates using 12.5 and 1 [micro]m radii Pt disk electrodes. Imaging of gold bands on a glass substrate demonstrates the capabilities for simultaneous topography and activity mapping. The prospect for using IC methodology more widely with other types of tips is highlighted briefly. 10.1021/ac101099e

[La.sub.0.7][Sr.sub.0.3]Mn[O.sub.3] is a conducting ferromagnet at room temperature. Combined with thin SrTi[O.sub.3] layers, the resulting heterostructures could be used as highly spin-polarized magnetic-tunnel-junction memories. However, when shrunk to dimensions below an apparent critical thickness, the structures become insulating and ferromagnetic ordering is suppressed. Interface spin and charge modulations are thought to create an interfacial dead layer, thus fundamentally limiting the use of this material in atomic-scale devices. The thickness of this dead layer, and whether it is intrinsic, is still controversial. Here we use atomic-resolution electron spectroscopy to demonstrate that the degradation of the magnetic and transport properties of [La.sub.0.7][Sr.sub.0.3]Mn[O.sub.3]/SrTi[O.sub.3] multilayers correlates with atomic intermixing at the interfaces, and the presence of extended two-dimensional cation defects in the [La.sub.0.7][Sr.sub.0.3]Mn[O.sub.3] layers (in contrast to three-dimensional precipitates in thick films). When these extrinsic defects are eliminated, metallic ferromagnetism at room temperature can be stabilized in five-unit-cell-thick manganite layers in superlattices, placing the upper limit for any intrinsic dead layer at two unit cells per interface. electron energy loss spectroscopy | manganites | scanning transmission electron microscopy doi/ 10.1073/pnas.1005693107

One of the great challenges in surface chemistry is to assemble aromatic building blocks into ordered structures that are mechanically robust and electronically interlinked--i.e., are held together by covalent bonds. We demonstrate the surface-confined growth of ordered arrays of poly(3,4-ethylenedioxythiophene) (PEDOT) chains, by using the substrate (the 110 facet of copper) simultaneously as template and catalyst for polymerization. Copper acts as promoter for the Ullman coupling reaction, whereas the inherent anisotropy of the fcc 110 facet confines growth to a single dimension. High resolution scanning tunneling microscopy performed under ultrahigh vacuum conditions allows us to simultaneously image PEDOT oligomers and the copper lattice with atomic resolution. Density functional theory calculations confirm an unexpected adsorption geometry of the PEDOToligomers, which stand on the sulfur atom of the thiophene ring rather than lying flat. This polymerization approach can be extended to many other halogen-terminated molecules to produce epitaxially aligned conjugated polymers. Such systems might be of central importance to develop future electronic and optoelectronic devices with high quality active materials, besides representing model systems for basic science investigations. metal-catalyzed coupling reaction | molecular wires | cis-polythiophene | scanning probe microscopy | polymerization mechanism doi/ 10.1073/pnas.1000726107

A multiscaled electrochemical probe is presented for Scanning Electrochemical Microscopy (SECM) experiments. It is fabricated by wet chemical etching followed by sputter-coating of an ordered optical fiber bundle. Owing to the optical fiber bundle preparation, the global electrode may present different shapes. After the chemical etching step, each one of these shapes is conserved and finally decorated with 6000 nanotips. Numerical simulations and approach curves are used to study the probe properties and the influence of the global shape and of the nanotips. The numerical simulations show that the approach curves do not depend on the shape of the electrode but rather on the total height of the protuberance of its electroactive part. Such new SECM probes are then used to pattern a Teflon surface. Indeed, by controlling the time scale of the applied potential pulses, the thickness of the reaction layer is confined at each nanotip, and the nanotip pattern is electrochemically transferred onto the non-conductive surface. Both scales (i.e., global electrode shape and nanotip array) thus show distinct and complementary features for positioning the probe and for the subsequent electrochemical patterning. 10.1021/ac100399q

Single-bounce attenuated total reflection infrared spectroscopy in the 3-20 [micro]m range (mid-infrared, MIR) has been combined with scanning electrochemical microscopy (SECM) for in situ spectroscopic detection of electrochemically induced localized surface modifications using an ultramicroelectrode (UME). In this study, a novel current-independent approach for positioning the UME in aqueous electrolyte solution is presented using either changes of infrared (IR) absorption intensity associated with borosilicate glass (BSG), which is used as shielding material of the UME wire, or by monitoring IR changes of the water spectrum within the penetration depth of the evanescent field due to displacement of water molecules in the volume between the sample surface and the UME within the evanescent field. The experimental results show that the UME penetrates into the exponentially decaying evanescent field in close vicinity (a few micrometer) to the attenuated total reflection (ATR) crystal surface. Hence, the resulting intensity changes of the IR absorption spectra for borosilicate glass (increase) and for water (decrease) can be used to determine the position of the UME relative to the ATR crystal surface independent of the current measured at the UME. 10.1021/ac902781h

The combination of scanning electrochemical microscopy (SECM) with single-bounce attenuated total reflection Fourier-transformed infrared spectroscopy (FT-IR-ATR) has been developed for in situ studies on electrochemically induced processes at IR waveguide surfaces via evanescent field absorption spectroscopy. The feasibility of the combined microelectrochemical FT-IR setup was demonstrated by spectroscopically monitoring micro-structured polymer depositions induced via feedback mode SECM using a 25 [micro]m Pt disk ultramicroelectrode (UME). The surface of a ZnSe ATR crystal was initially coated with 2,5.di-(2-thienyl)-pyrrole (SNS) layer, which was then locally polymerized during Ru[(bpy).sub.3.sup.2+] mediated feedback mode SECM experiments. The polymerization reaction was simultaneously monitored by recording absorption intensity changes of SNS specific IR bands, thereby providing information on the polymerization mechanism and on the percentage of surface modification. 10.1021/ac9027802

The impact properties of core-shell acrylate (CS-ACR)/chlorinated polyethylene (CPE)/poly(vinyl chloride) (PVC) blends under different temperatures were investigated. The fracture surface morphologies of the blends were observed by scanning electron microscopy (SEM). The results show that there exists significant synergistic effect between CS-ACR particles and CPE in toughening PVC, and the impact properties of the blends generally correlate well with SEM morphologies. Besides, with increasing CS-ACR content, ductile-brittle transition point of the ternary blends remarkably shifts to a lower temperature. Dynamic mechanical analysis exhibited that intensity and area of low-temperature tan δ peaks of the CPE/PVC blends increase obviously after the addition of CS-ACR particles, which to some extent are just in line with the changes in impact strength and ductile-brittle transition point of the blends. POLYM. ENG. SCI., 50:295-301, 2010. [C] 2009 Society of Plastics Engineers, INTRODUCTION As is well known, poly(vinyl chloride) (PVC) is one of the most versatile thermoplastic resins used today. It has been widely used in pipes, sheets, and other profiles because [...]

Nanomaterials continue to attract widespread attention in many scientific and technological fields. The sizes and shapes of nanomaterials determine their physical and chemical properties. We have developed an analytical system for single nanomaterials that combines capillary electrophoresis (CE) with a highly sensitive detection method. In this manuscript, we combined CE with Raman spectroscopy or with scanning probe microscopy (SPM) for the analysis of individual single-wailed carbon nanotubes (SWNTs). To combine CE with these detection techniques, we fabricated a fraction collection system that can collect droplets of small volume (

The electrochemical oxidation of formic acid was studied by the tip generation-substrate collection (TG-SC) mode of scanning electrochemical microscopy (SECM), extending the number of applications of SECM in electrocatalysis. Formic acid was generated at a Hg on Au ultramicroelectrode (UME) tip by reduction of C[O.sub.2] in a 0.1 M KHC[O.sub.3] solution saturated with this gas. The electrocatalytic activity of different Pd-Co bimetallic compositions was evaluated using a Pd-Co electrocatalyst array formed by spots deposited onto glassy carbon (GC) as a SECM substrate. The SECM tip, which generated a constant formic acid flux, was scanned above the array and the oxidation current generated when formic acid was collected by active electrocatalyric spots was displayed as a function of tip position. This generated a SECM image that showed the electrocatalytic activity of each spot. SECM screening identified [Pd.sub.50][Co.sub.50] (Pd/Co = 50:50, atomic ratio) as a better electrocatalyst toward the formic acid oxidation than pure Pd or Pt in 0.1 M KHC[O.sub.3] solution and this result was confirmed by cyclic voltammetry. Positive feedback was observed for the most active compositions of Pd-Co which suggests fast reaction kinetics and chemical reversibility during the oxidation of formic acid to C[O.sub.2]. Moreover this feedback increases the contrast between active and non-active spots in this imaging mode.

A soft stylus microelecirode probe has been developed to carry out scanning electrochemical microscopy (SECM) of rough, tilted, and large substrates in contact mode. It is fabricated by first ablating a microchannel in a polyethylene terephthalate thin film and filling it with a conductive carbon ink. After curing the carbon track and lamination with a polymer film, the V-shaped stylus was cut thereby forming a probe, with the cross section of the carbon track at the tip being exposed either by UV-photoablation machining or by blade cutting followed by polishing to produce a crescent moon-shaped carbon microelectrode. The probe properties have been assessed by cyclic voltammetry, approach curves, and line scans over electrochemically active and inactive substrates of different roughness. The influence of probe bending on contact mode imaging was then characterized using simple patterns. Boundary element method simulations were employed to rationalize the distance-dependent electrochemical response of the soft stylus probes.

In this study, we have demonstrated that a scanning probe microscope (SPM) can be used for thermally assisted nanosampling (TAN) with subsequent analysis by capillary electrophoresis (CE). Localized thermomechanical analysis (L-TMA) and photothermal Fourier-transform infrared (PT-FTIR) microspectroseopy can also be employed using the same probe, thus illustrating how a single instrument can carry out a number of different complementary analytical measurements. Benzoic acid and 4-hydroxy-benzoic acid were manipulated with a heated Wollaston wire probe and successfully deposited onto the surface of a piece of CE capillary tubing. The deposited samples were then separated with CE. L-TMA and PT-FTIR were also used to characterize these materials. We have also demonstrated how a nanosample of a nonparticulate material can be taken and then deposited onto the surface of an inert matrix. TAN of a nonparticulate material was explored using polyethylene as the analyte and fluorene as the matrix. These examples show that thermal probe techniques provide a versatile 'tool box' of modes of analysis with the potential to analyze a wide range of samples in a spatially resolved way.

Nanowires with nanometer-scale gaps are an emerging class of nanomaterials with potential applications in electronics and optics. Here, we demonstrate that the feedback mode of scanning electrochemical microscopy (SECM) allows for spatially resolved detection of a nanogap on the basis of its electrical conductivity. A gapped nanoband is used as a model system to describe a mechanism of a unique feedback effect from a nanogap. Interestingly, both experiments and numerical simulations confirm that a peak current response is obtained when an SECM lip is laterally scanned above an insulating nanogap formed in an unbiased nanoband. On the other hand, no peak current response is expected for a highly conductive nanogap, which must be extremely narrow or rifled with highly conductive molecules for efficient electron transport.

The purpose of this study was to develop a scanning electrochemical microscopy (SECM) and scanning electrogenerated chemiluminescence (SECL) setup to visualize the localized enzymatic activity using glucose oxidase as a model. Combination of SECM and electrogenerated chemiluminescence (ECL) was made possible by integrating a photomultiplier tube (PMT) within a SECM setup which is mounted on top of an inverted microscope. An enzyme--polymer spot formed on a glass slide and placed on top of the entrance window of the PMT was used as a model sample to evaluate the potential of the combined SECM/ECL setup. Hydrogen peroxide, which was locally generated by the glucose oxidase (GOx)-catalyzed reaction, reacted with oxidized luminol which was simultaneously electrochemically generated at the positioned SECM electrode tip. By using the phase-sensitive lock-in amplifier, the potential applied to the SECM lip was sinusoidally swept to invoke an associated oscillation of the ECL Thus, sensitivity of SECL could be substantially enhanced. Images of the local immobilized enzyme activity obtained both by ECL and generator/collector (GC) mode of SECM were compared to elucidate the pathway in which the SECM and SECL signals are generated.

Scanning ion conductance microscopy (SICM) is a scanned probe microscopy technique in which the probe is a fine glass pipet filled with a contact (reference) electrode and an electrolyte solution. The current flow between the reference electrode and a second reference electrode positioned in bulk solution when the two electrodes are biased externally can be used as a feedback signal to maintain a constant separation between the tip and a surface during imaging. In usual practice the tip position is modulated over a small amplitude perpendicular to the surface, and the resulting alternating current (AC) is used as the feedback signal, although the direct current can also be used. A comprehensive model for the current response is reported. Laplace's equation has been solved for the electrolyte solution for a range of tip geometries, enabling the factors controlling the tip current to be identified. The approach developed is shown to represent an improvement over earlier semiempirical treatments. To explore the influence of surface topography on the (AC) current response, various surfaces have been considered, including a lip moved toward a planar surface (in the normal direction) and tips scanned over a pit and a step in the surface. The results have allowed a critical assessment of the SICM response as a means of probing surface topography. Features identified through simulation have been found in experiments through studies of two model substrates for which imaging results are reported. In typical experimental practice, the response of the SICM tip to surface features occurs over much greater lateral distances than the size of the pipet aperture.

In this paper, we propose a method of position error signal (PES) generation for read-only-memory (ROM) type scanning probe microscopy (SPM)-based data storage (SDS) systems. Conventionally, PES is generated by using servo bursts similar to those of hard disk drives. Recently, it was reported that stripe patterned media enables the generation of PES without using servo bursts as hard disk drives. In this paper, we report the fabrication of patterned media and its experimental results. Servo patterns are nanoimprinted on polymer medium film. We succeed in reading data and the servo patterns with a 1 x 3 cantilever. We also demonstrate track follow control with the PES of the ROM type SDS through simulations. Index Terms--Position error signal, scanning probe microscopy, SPM-based data storage.

The alignment of deposited minerals in tissues such as bone and teeth plays a critical role in the mechanical properties of these tissues. Therefore, assessment of features that are characteristic of aligned biominerals could aid in the development of novel biomaterials and engineered tissues that can be used to replace damaged or defective human tissues. In this study, we demonstrate that light scattering spectroscopy can serve as a useful tool for the noninvasive characterization of mineralization on aligned organic substrates. Specifically, we used silk films with oriented and nonoriented secondary structures as a protein matrix for control of mineralization. The mineral deposits displayed self-affine fractal morphologies with the oriented films yielding a significantly higher Hurst parameter, which in turn suggests higher levels of fractal organization. In addition, the value of the upper bound of fractal correlation lengths was significantly smaller for the oriented than for the nonoriented films and correlated well with the size of the corresponding nanocrystalline mineral beads identified by scanning electron microscope imaging. OCIS codes: 160.1435, 290.1350, 290.5855.

Field emission scanning electron microscopy (FESEM), two-dimensional X-ray diffraction (2DXRD), and transmission electron microscopy coupled with selected area electron diffraction (TEMSAED) analyses of the reactant/product textural relationship show that the thermal decomposition of Iceland spar single crystals according to the reaction CaC[O.sub.3(s)] [right arrow], Ca[O.sub.(s)] + C[O.sub.2(g)] is pseudomorphic and topotactic. This reaction begins with the formation of a mesoporous structure made up of up to four sets of oriented rod-shaped CaO nanocrystals on each rhombohedral cleavage face of the calcite pseudomorph. The four sets formed on [(10[bar.1]4).sub.calcite] display the following topotactic relationships: (1) [(1[bar.2]10).sub.calcite][parallel][(110).sub.CaO]; (2) [([bar.1]104).sub.calcite[parpendicular to]][(110).sub.Cao]; (3) [([bar.1]018).sub.calcite]][parallel][(110).sub.CaO]; and (4) [(0[bar.1]14).sub.calcite[perpendicular to]] [(110).sub.CaO]; with [[841].sub.calcite][parallel][[1[bar.1]O].sub.CaO] in all four cases. At this stage, the reaction mechanism is independent of [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (i.e., air or high vacuum). Strain accumulation leads to the collapse of the mesoporous structure, resulting in the oriented aggregation of metastable CaO nanocrystals (~5 nm in thickness) that form crystal bundles up to ~1 [micro]m in cross-section. Finally, sintering progresses up to the maximum T reached (1150 [degrees]C). Oriented aggregation and sintering (plus associated shrinking) reduce surface area and porosity (from 79.2 to 0.6 [m.sup.2]/g and from 53 to 47%, respectively) by loss of mesopores and growth of micrometer-sized pores. An isoconversional kinetic analysis of non-isothermal thermogravimetric data of the decomposition of calcite in air yields an overall effective activation energy [E.sub.[alpha]] = 176 [+ or -] 9 k J/ mol (for [alpha] > 0.2), a value which approaches the equilibrium enthalpy for calcite thermal decomposition (177.8 kJ/mol). The overall good kinetic fit with the F I model (chemical reaction, first order) is in agreement with a homogeneous transformation. These analytical and kinetic results enable us to propose a novel model for the thermal decomposition of calcite that explains how decarbonation occurs at the atomic scale via a topotactic mechanism, which is independent of the experimental conditions. This new mechanistic model may help reinterpret previous results on the calcite/CaO transformation, having important geological and technological implications. Keywords: Calcite, lime, thermal decomposition, CaO nanocrystals, TEM-SAED, oriented aggregation, kinetics, topotactic