Zirconia bio-ceramic hollow fiber membranes were developed using a sequence of mixing, extrusion, phase inversion and sintering steps. ZrO2 partially stabilized by Y2O3 was chosen as the starting membrane material. The prepared membranes were characterized by SEM, EDX, XRD and gas permeation techniques. Effects of the starting ZrO2 particle size and sintering temperature on the physical properties of the resulted hollow fiber membranes were extensively studied. Sintered at 1400°C for 10 h, membranes made from 80 nm sized ZrO2 particles display cubic fluorite as the major crystalline phase and give rise to interesting microstructure for cell response. Without any surface modification, this tailor-made membrane with high mechanical strength and pore size less than 1 f. Lm was selected for further test of osteoblast attachment. In vitro bio-compatibility was evaluated by using mouse MC-3T3-E1 osteoblast cell culture. A series of cell interactions with fiber surface (i.e. cell adhesion, proliferation, formtion of bone nodules, mineralization, etc.) verified the bio-compatibility of the prepared membranes.

© 2006 Elsevier B.V. All rights reserved.

Key Words: Hollow fiber; Zirconia; Bio-ceramic membrane; Osteoblast cell; Macro-encapsulation; Osteoconduction; Gene delivery

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In the literature, a few biological cells have been used as templates to form microcapsules of a variety of shapes and sizes. In this study, we proved the concept that living cells like platelets can be encapsulated with polyelectrolytes using electrostatic layer-by-layer self-assembly (LBL), and, most importantly, the encapsulation process did not induce activation of the platelets. Glycol- chitosan and poly-L-glutamic acid were electrostatically deposited onto platelets, and the encapsulation was confrmed using confocal laser scanning microscopy and scanning electron microscopy. Transmission electron microscopy observation further confrmed that the encapsulation process was mild and the activation of platelets was negligible. The encapsulation of living biological cells like platelets can serve as a model system in a wide range of biomedical applications including local and sustained drug delivery, immune protection of artifcial tissues, and versatile artifcial blood.

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Reproductive units (RUs) of Trithuria, the sole genus of the early-divergent angiosperm family Hydatellaceae, are compared with flowers of their close relatives in Cabombaceae (Nymphaeales). Trithuria RUs combine features of flowers and inflorescences. They differ from typical flowers in possessing an "inside-out" morphology, with carpels surrounding stamens; furthermore, carpels develop centrifugally, in contrast to centripetal or simultaneous development in typical flowers. Trithuria RUs could be interpreted as pseudanthia of two or more cymose partial inflorescences enclosed within an involucre, but the bractlike involucral phyllomes do not subtend partial inflorescences and hence collectively resemble a typical perianth. Teratological forms of T. submersa indicate a tendency to fasciation and demonstrate that the inside-out structure-the primary feature that separates RUs of Hydatellaceae from more orthodox angiosperm flowers-can be at least partially modified, thus producing a morphology that is closer to an orthodox flower. The Trithuria RU could be described as a "nonflower", i.e., a structure that contains typical angiosperm carpels and stamens but does not allow recognition of a typical angiosperm flower. The term nonflower could combine cases of secondary loss of flower identity and cases of a prefloral condition, similar to those that gave rise to the angiosperm flower. Nonhomology among some angiosperm flowers could be due to iterative shifts between nonfloral construction and flower/inflorescence organization of reproductive organs. Potential testing of these hypotheses using evolutionary- developmental genetics is explored using preliminary data from immunolocalization of the floral meristem identity gene LEAFY in T. submersa, which indicated protein expression at different hierarchical levels.
Key Words: angiosperm,, development, evo-devo, flower, Hydatellaceae, immunolocalization, inflorescence, LEAFY, ontogeny, pseudanthium, Trithuria

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Kulik, M. M. 1988.Observations by scanning electron and bright-field microscopy on the mode of penetration of soybean seedlings by Phomopsis phaseo/i. Plant Disease 72:115-118.

Cotyledons, hypocotyls, and unifoliolate leaves of soybean seedlings at growth stage VI grown in pots in the greenhouse were inoculated by spraying with an aqueous suspension of 100,000 alpha conidia of Phomopsis phaseoli per milliliter. Plants were incubated in a moist chamber at 21-27 C for 24-144 hr. Scanning electron and bright-field microscopy were used to examine plant material collected at 24-hr intervals beginning 24 hr after inoculation. Conidia produced germ tubes 24-48 hr after inoculation. Germ tubes from conidia situated directly over or immediately adjacent to stomata sometimes produced appressoria. Germ tubes penetrated leaves and cotyledons via stomata but did not penetrate directly through the cuticle. Conidia were not observed on hypocotyls. A reticulum associated with conidia that may serve to anchor the conidium to the host surface also was observed.

Key Words: soybean pod and stem blight

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The morphology of specialized structures in the leaf epidermis of 32 species of basal (ANITA: Amborella, Nymphaeales, Illiciales, Trimeniaceae, and Austrobaileyaceae) angiosperms, representing all seven families and 11 of 14 genera, was investigated using light and scanning electron microscopy. Distribution, density, and size of structures were also measured, and character evolution was analyzed. Hydropotes are a synapomorphy of Nymphaeales and ethereal oil cells are a synapomorphy of Austrobaileyales, but uniseriate nonglandular trichomes appear to have arisen independently several times. Specialized structures are frequently characterized by adjacent epidermal cells that have striking similarities in their form and arrangement (i.e., architecture) to subsidiary cells of certain types of stomatal complexes. Additionally, forms intermediate to oil cells and stomata, to trichomes and stomata, and to hydropotes and oil cells are present in some taxa. Thus, all of these specialized structures and their adjacent epidermal cells form complexes that may be homologous with, and evolutionarily derived from stomatal complexes, and the specialized structure, or portion thereof, may be homologous to the stoma or guard mother cell. Improved knowledge of the morphology and evolution of these structures in the earliest branching extant angiosperm lineages has a bearing on many diverse areas of botany.
Key Words: Amborellaceae, Austrobaileyales, evolution, hydropotes, leaf epidermal anatomy, Nymphaeales, oil cells, trichomes.

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The epidermis of the aerial organs of higher plats is covered by a cuticle, which is an extracellular thick membrane consisting of a complex cutin matrix and a soluble epicuticular waxes deposited on its surface. The anatomy and chemistry of the waxes of leaves is functioning as a trap to collect water, protect plants against contamination and pests and pathogen attack, and fulfil other important functions (Seymur et al., 1996). During leaf development the wax layer grows by deposition on the leaf surface with special morphological and chemical features that are characteristic of the species and have taxonomic value (Stace, C.A. ,1989). Our observations of the surface of micro-propagated Agave plants by SEM show that the first deposition of waxes occurs inside and around the stomata. Micro- propagated plants lack epicuticular waxes and are therefore a good system to study the early stages of wax deposition. The SEM images of waxes around stomata from different species (own unpublished results) also suggest that waxes, or wax precursors are expelled as emulsion in water phase or in gas phases (O2 and CO2) to the surface of leaf through the stomata, during the process of water evaporation and oxygen/carbon dioxide gas exchange and are deposited on the more cold leaf surface by condensation (by facilitated diffusion).
Key Words: stomata

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Promalactis suzukiella (Matsumura) was discovered independently several times over the past 5 years throughout the northeastern United States by private collectors and biophotographers. These discoveries represent the first records of this species in the United States and validate its approximate distributional range. Color photographs and a redescription of the adult, including the male and female genitalia, are provided. The larva and pupa of Promalactis are described in detail for the first time, with scanning electron micrographs and chaetotaxal maps. A lectotype for Borkhausenia suzukiella Matsumura, 1931, is designated herein. The importance of "backyard collecting" and amateur biophotography is emphasized, and participants are encouraged to continue the documentation of their findings through meetings, publication, and the internet.
Key Words: Asia, invasive species, Japan, rotting wood, tree bark

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Recent models of pattern formation in insects have been derived largely from observations on regenerated cuticular patterns. Such models make assumptions about the behaviour of the underlying epidermal cells, their movement and patterns of cell division. The present study, designed to test these assumptions, looks at the patterns of wound healing and cell division after amputation at the trochanter-femur joint of the metathoracic leg in the cockroach. It shows that the wound is closed by cell migration and that regeneration occurs by dedifferentiation of the trochanter and distal coxa to form a blastema which grows and redifferentiates to form the new limb. The extent of the spread of dedifferentiation is confirmed by a scanning electron microscope study of the coxa after the moult following amputation. The results highlight the need for a greater knowledge of cell behaviour during pattern formation before we can begin to understand the processes involved in pattern formation.

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The study of light emission from porous silicon has attracted great interest since the first observation of its photoluminescence at room temperature. Recently, particular interest is devoted to supercritical fluid CO2 applications on the drying of this semiconductor. This fluid is inotoxic, non-flammable, unreactive under most conditions, leaves no liquid waste. It has a potential to ameliorate environmental safety and health impact and it enables innovative processing technologies and material protection. This talk reviews the mechanism of supercritical drying of porous silicon and the role of this fluid in this process.
Key Words: Porous silicon � Supercritical drying � Supercritical fluid CO2

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The effects of supercritical drying of diluted resorcinol-formaldehyde (RF) gels in CO2 and in acetone are compared. We show that, for both processes, depressurizing rate of the autoclave after drying has a significant influence on the resultant shrinkage, and hence on resultant bulk density, surface area and pore volumes. At depressurizing rates below 2 MPa/min, acetone leads to much lower shrinkage than does CO2, and is 1000 times cheaper. However, supercritical drying with CO2 remains interesting because it is faster, easier to control, less sensitive to the experimental conditions and cleaner. We indeed show that acetone is degraded and leads to various compounds that might partly remain in the porosity of the dried RF gels. Supercritical CO2 also clearly leads to the highest surface areas and micropore volumes, whereas supercritical acetone is in favour of higher mesopore volumes, especially at high depressurizing rates.
Key Words: Aerogel Supercritical drying Shrinkage Pore volume Surface area

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We report the synthesis and characterization of interconnected macroporous network structures of poly(ethylene glycol) (PEG) using cryogelation techniques. Novel monolithic networks containing a gradient of pore size in a layered fashion were created from a single precursor by manipulating their polymerization kinetics. Maintaining conditions that promote the rate of gelation compared to that of the nucleation of ice crystals leads to formation of either conventional hydrogel-like network structures or continuous heterogeneous networks containing layers of hydrogel-like and cryogel-like microstructures. In contrast, conditions promoting a faster rate of the nucleation of ice crystals compared to rate of gelation result in cryogels with a nearly homogeneous interconnected macroporous network. The rates of polymerization and nucleation of ice crystals were altered using a number of different parameters such as concentration of initiator, freezing temperature, and degree of supercooling. Compared to conventional hydrogels, the cryogels exhibit higher stress and strain at break; their mechanical and equilibrium swelling properties show a strong correlation with the network microstructure. Cell viability studies suggest no detrimental effect of these scaffolds on cell attachment and their distribution. Furthermore, a time dependent increase in chondrocyte proliferation was observed in cryogels over a long period of culture.

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The effect of SiO2 to TiO2 aerogels content on their local structure is evidenced from X-ray scattering measurements. TiO2-SiO2 aerogels were prepared by sol-gel method followed by supercritical drying with liquid CO2 and heat treatment. The local structure of TiO2-SiO2 system was investigated by analysing the atomic pair distribution function PDF , G(r) , obtained from X ray scattering data The modified coordination radius values obtained for the first coordination spheres by addition of SiO2 denotes a diminution of the atom packing in this system. The PDF of the 3000C heat treated TiO2 aerogel sample shows well-defined features allowing an unambiguous structure search and refinement. In particular, the first peak in the PDF of the precursor phase is quite narrow and centered at about 1.9 Å, which is the Ti-O distance in Ti-O6 octahedra. This observation shows that well-defined Ti-O6 octahedra are already formed during the homogeneous precipitation stage of the chemical process. Inspecting the data from the analysis of the atomic pair distribution function G(r) one remarks the occurrence of Si-O pair as a first coordination formation at a distance of 1.49 Å and the interatomic distances at 2.18 Å for the first Si---Si and 3.58 Å for the second Si---Si bond.

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Gelation of tannin-formaldehyde (TF) solutions was systematically investigated by changing pH and concentration of TF resin in water. In this way we constructed the TF phase diagram, from which chemical hydrogels could be described, and also synthesized thermoreversible tannin-based hydrogels. Conditions of non-gelation were also determined. Hydrogels were dried in supercritical CO2 , leading to a broad range of TF aerogels. The latter were investigated for volume shrinkage, total porosity, micro-, meso- and macropore volumes, Brunauer-Emmett-Teller (BET) surface area, microscopic texture, mechanical and thermal properties. All these properties are discussed in relation to each other, leading to an accurate and self-consistent description of these bioresource-based highly porous materials. The conditions for obtaining the highest BET surface area or mesopore volume were determined and explained in relation to the preparation conditions. The highest BET surface area, 880 m²g^-1 , is remarkably high for organic aerogels derived from a natural resource.
Key Words: aerogel, tannin, porosity, surface area, mechanical strength, thermal conductivity

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Polysaccharide aerogels are a good alternative as carriers for drug delivery, since they allow high loading of the active compounds in matrices that are non-toxic, biocompatible and from a renewable feedstock. In this work, barley and yeast β-glucans aerogels were produced by gelation in aqueous solution, followed by solvent exchange and drying with supercritical CO2. First, viscoelastic properties and melting profile of the hydrogels were determined. Then, the obtained aerogels were analyzed regarding morphology, mechanical properties and behavior in physiological fluid. Both in the hydrogels and in the aerogels, big differences were observed between barley and yeast ?-glucans due to their different chain structure and gelation behavior. Finally, impregnation of acetylsalicylic acid was performed at the same time as the drying of the alcogels with supercritical CO2. The release profile of the drug in PBS was analyzed in order to determine the mechanism governing the release from the β-glucan matrix.
Key Words: β-glucan, Acetylsalicylic acid Aerogel, Rheology, Supercritical drying,Supercritical impregnation

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Graphene oxide (GO)-based gels are attractive because of their ability to retain individual nanosheet properties in a three-dimensional (3D) bulk material. The final morphology and properties of these 3D gel networks depend strongly on the type and density of cross-links, and these gels can be dried and annealed to form aerogels with both high conductivity (560 S/m) and high surface area (1700 m²/g). The results show that both ammonia content and the parent nanosheet morphology (crumpled vs flat) have a strong influence on the cross-linked structure and composition; notably, nitrogen is found in the gels, suggesting that ammonia actively participates in the reaction rather than as a mere catalyst. The GO nanosheet morphology may be altered using spray-drying to obtain crumpled GO (cGO) nanosheets and form cGO gels; this allows for an additional handle in the creation of GO-based gels with tunable density, electrical conductivity, and surface area.

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Heat at intermediate temperatures (120-220°C) is in significant demand in both industrial and domestic sectors for applications such as water and space heating, steam generation, sterilization, and other industrial processes. Harnessing heat from solar energy at these temperatures, however, requires costly optical and mechanical components to concentrate the dilute solar flux and suppress heat losses. Thus, achieving high temperatures under unconcentrated sunlight remains a technological challenge as well as an opportunity for utilizing solar thermal energy. In this work, we demonstrate a solar receiver capable of reaching over 265°C under ambient conditions without optical concentration. The high temperatures are achieved by leveraging an artificial greenhouse effect within an optimized monolithic silica aerogel to reduce heat losses while maintaining high solar transparency. This study demonstrates a viable path to promote cost-effective solar thermal energy at intermediate temperatures.
Key Words: solar thermal conversion transparent aerogel artificial greenhouse effect light scattering radiative transfer

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We fabricate and investigate high-quality graphene devices with contactless, suspended top gates and demonstrate the formation of graphene pnp junctions with tunable polarity and doping levels. The device resistance displays distinct oscillations in the npn regime, arising from the Fabry-Perot interference of holes between the two pn interfaces. At high magnetic fields, we observe well-defined quantum Hall plateaus, which can be satisfactorily fit to theoretical calculations based on the aspect ratio of the device.

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Coupling high-quality suspended atomic membranes to specialized electrodes enables the investigation of many novel phenomena, such as spin or Cooper pair transport in these two-dimensional systems. However, many electrode materials are not stable in the acids that are used to dissolve underlying substrates. Here we present a versatile and powerful multilevel lithographical technique to suspend thin crystals, which can be applied to the vast majority of substrate, crystal and electrode materials. Using this technique, we fabricated suspended graphene devices with Al electrodes and a mobility of 5500 cm2 V^-1 s^-1 . We also demonstrate, for the first time, fabrication and measurement of a free-standing thin Bi2Se3 crystal, which has low contact resistance to electrodes and a mobility of >~580 cm2 V^-1 s^-1.

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We show that the optical transparency of suspended graphene is defined by the fine structure constant, α = e²/hc, the parameter that describes coupling between light and relativistic electrons and is traditionally associated with quantum electrodynamics rather than condensed matter physics. Despite being only one atom thick, graphene is found to absorb a significant (πα =2.3%) fraction of incident white light, which is a consequence of graphene's unique electronic structure. This value translates directly into universal dynamic conductivity G =e²/4h within a few % accuracy.

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Two-dimensional materials, such as graphene, molecular nanosheets, hexagonal boron nitride or transition metal dichalcogenides have recently attracted substantial interest due to their potential use in electronics, chemical and biological sensors, nanooptics, and catalysis. For most of these applications, the functional nanostructures have to be prepared lithographically. In this respect, extreme ultraviolet interference lithography provides both high-resolution patterning with an ultimate limit in the sub-10 nm range and high throughput capability. Here we present the preparation of nanopatterned 1 nm thick freestanding molecular nanosheets-carbon nanomembranes (CNMs)-and single layer graphene employing this method and their characterization with a helium ion microscope. We demonstrate periodic arrays of suspended nanostructures of CNMs and graphene including nanoribbons with width between 20 nm and 500 nm and nanomeshes with openings between 140 nm and 300 nm and mesh lines down to 90 nm.
Key Words: graphene, carbon nanomembrane, EUV interference lithography, nanoribbon, nanomesh

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Graphite's capacity of intercalating lithium in rechargeable batteries is limited (theoretically, 372 mAh g^-1) due to low diffusion within commensurately-stacked graphene layers. Graphene foam with highly enriched incommensurately-stacked layers was grown and applied as an active electrode in rechargeable batteries. A 93% incommensurate graphene foam demonstrated a reversible specific capacity of 1,540 mAh g^-1 with a 75% coulombic efficiency, and an 86% incommensurate sample achieves above 99% coulombic efficiency exhibiting 930 mAh g^-1 specific capacity. The structural and binding analysis of graphene show that lithium atoms highly intercalate within weakly interacting incommensurately-stacked graphene network, followed by a further flexible rearrangement of layers for a long-term stable cycling. We consider lithium intercalation model for multilayer graphene where capacity varies with N number of layers resulting Li_N+1C_2N stoichiometry. The effective capacity of commonly used carbon-based rechargeable batteries can be significantly improved using incommensurate graphene as an anode material.

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Five different procedure commonly used to rinse and dry released microstructure are compared: evaporation drying with deionized (DI) water or methanol, sublimation drying with t-butyl alcohol or p-dichlorobenzene, and supercritical drying with CO2. For objective comparison, identical test structure, made by the MCNC Multi-User MEMS Process (MUMPs), are used in evaluating drying techniques. The test chip contains arrays of surface-micromachined polysilicon cantilevers (2 µm thick, 2 µm gap from the substrate) with varying widths and lengths. Some beams feature dimples of tips to quantify their anti-stiction effect. This study revels, for the first time, that the maximum beam length obtainable increase as the beam width increase for the cases of sublimation and supercritical drying, opposite to previously known case of evaporation drying. Both sublimation drying methods as well as supercritical drying rendered good results, releasing cantilevers up to 700 µm in length without stiction. We also introduce a new setup that considerably improves the way sublimation is used to dry microstructure.
Key Words: release methods; stiction; surface micromachining

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In this paper, we describe high-precision experi- mental and numerical characterization of the positioning forces acting on Drosophila embryos that have self-assembled onto 2-D arrays of hydrophobic sites on a silicon substrate in water. The forces measured using a surface micromachined optical-encoder force sensor operating in reflection, are in good agreement with numerical simulations based on an extended surface energy model for the oil-based fluidic system. The positioning forces of ellipsoidal embryos on flat sites show a linear-spring-like re- lationship between the force and displacement on rectangular as well as cross-shaped sites. An average detachment force of 8.9 µN ± 13 µN was found for the immobilized embryos on 250 µm x 100 µm sites. The cross-shaped site has only 19.85% of the area of the rectangular site, but provides a comparable positioning force with a significant reduction in embryo clustering. In contrast, the positioning forces of flat silicon chips, similar in size to the embryos, are linear in the displacement only over a limited range (0 ~ 40 µm), and are then constant up to the detachment force (25.0 µN ± 3.5 µN). Our measurements also show significant hysteresis in the force vs. displacement, indicating that variations in the surface properties play an important role in the self-assembly process.
Key Words: Capillary force, Drosophila embryo, force sensor, optical encoder, self-assembly, surface energy, surface tension

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A microchip separation process operating by pulsed-wave IR laser irradiation was applied to microviscosimeters that are intended to operate as glucose sensors for continuous monitoring of blood sugar levels in diabetics. After its technological preparation the sensor should no more dry up, since the retreating water would stick a movable cantilever to the ground plate and thereby plastically deform the sensor's micromechanics. The cooling-free IR laser dicing process was thus chosen for the separation. It is shown that virtually particle free dices with lateral dimension down to some 100 µm could be prepared. The process is concluded to enable the dry, fast and clean separation of MEMS devices
Key Words: MEMS, glucose sensor, Si wafer, stealth dicing

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This paper presents the growth and release process effects on the deformation of suspended gold micro-structures. Cantilever type test structures, typically used for RF MEMS devices have been examined. The structures have a thickness of 2µm, produced by patterned gold electro deposition above a sacrificial photoresist layer, then removed by dry release in oxygen plasma ashing and wet release using critical point dryer (CPD). The growth process of gold electroplating is optimized for low residual stress using pulse power supply. Minimum stress 35-60 MPa is obtained at grain size 30-45nm and RMS roughness of the order of 5-8nm. The growth mechanism of structural layer and releasing methods are optimized to obtain planar MEMS structures. The main parameters considered are the initial stress during the growth of electroplated gold and the release process recipes developed for fabrication of metallic structural layer.
Key Words: RF MEMS, Plasma ashing, Critical Point Dryer (CPD), Electroplating, Microstructure, Deformation

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We report a novel electrostatic actuated nano-electromechanical optoelectronic (NEMO) tunable vertical-cavity surface-emitting laser (VCSEL) centered at 850 nm. By integrating a movable, single-layer {230 nm), high-index-f()ntrast subwavelength grating (HCG) as the VCSEL top mirror, single mode enililsion (SMSR >40 dB) and continuous wavelength tuning (-2.5 nm) was obtained at room temperature under CW operation. The small footprint of HCG enables the scaling down of each of the cantilever dimensions by a factor of 10, leading to 1000 times reduction in mass, which potentially increases the mechanical resonant frequency and tuning speed.
Key Words: NEMO, VCSEL

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We describe the use of a microfabricated cell culture substrate, consisting of a uniform array of closely spaced, vertical, elastomeric microposts, to study the effects of substrate rigidity on cell function. Elastomeric micropost substrates are micromolded from silicon masters comprised of microposts of different heights to yield substrates of different rigidities. The tips of the elastomeric microposts are functionalized with extracellular matrix through microcontact printing to promote cell adhesion. These substrates, therefore, present the same topographical cues to adherent cells while varying substrate rigidity only through manipulation of micropost height. this protocol describes how to fabricate the silicon micropost array masters (~2 weeks to complete) and elastomeric substrates (3 d), as well as how to perform cell culture experiments (1-14 d), immunofluorescence imaging (2 d), traction force analysis (2 d) and stem cell differentiation assays (1 d) on these substrates in order to examine the effect of substrate rigidity on stem cell morphology, traction force generation, focal adhesion organization and differentiation.

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Syntaxin-1 and 25-kDa Synaptosome-associated Protein (SNAP-25) are present in the plasma membrane of several different secretory cell types and are involved in the exocytosis process. In this work, the free-living amoeba Difflugia corona was studied in relation to ultrastructure, structural membrane proteins, and proteins such as Syntaxin-1 and SNAP-25. Our results obtained by scanning electron microscopy in the amoeba without its theca, showed many membrane projections and several pore-like structures. Using immunocytochemistry, we found structural proteins Syntaxin-1 and SNAP-25.
Key Words: amoeba, membrane proteins, pore-like, theca, ultrastructure

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Unconventional myosins interact with the dense cortical actin network during processes such as membrane trafficking, cell migration, and mechanotransduction. Our understanding of unconventional myosin function is derived largely from assays that examine the interaction of a single myosin with a single actin filament. In this study, we have developed a model system to study the interaction between multiple tethered unconventional myosins and a model F-actin cortex, namely the lamellipodium of a migrating fish epidermal keratocyte. Using myosin VI, which moves toward the pointed end of actin filaments, we directly determine the polarity of the extracted keratocyte lamellipodium from the cell periphery to the cell nucleus. We use a combination of experimentation and simulation to demonstrate that multiple myosin VI molecules can coordinate to efficiently transport vesiclesize cargo over 10 µm of the dense interlaced actin network. Furthermore, several molecules of monomeric myosin VI, which are nonprocessive in single molecule assays, can coordinate to transport cargo with similar speeds as dimers.
Key Words: TMR, tetramethylrhodamine

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We cloned two novel Trypanosoma cruzi proteins by using degenerate oligonucleotide primers prepared against conserved domains in mammalian serine/threonine protein phosphatases 1, 2A, and 2B. The isolated genes encoded proteins of 323 and 330 amino acids, respectively, that were more homologous to the catalytic subunit of human protein phosphatase 1 than to those of human protein phosphatase 2A or 2B. The proteins encoded by these genes have been tentatively designated TcPP1a and TcPP1 (3. Northern blot analysis revealed the presence of a major 2.3-kb mRNA transcript hybridizing to each gene in both the epimastigote and metacyclic trypomastigote developmental stages. Southern blot analysis suggests that each protein phospha- tase 1 gene is present as a single copy in the T. cruzi genome. The complete coding region for TcPP1 (3 was expressed in Escherichia coli by using a vector, pTACTAC, with the trp-lac hybrid promoter. The recombinant protein from the TcPP1 (3 construct displayed phosphatase activity toward phosphorylase a, and this activity was preferentially inhibited by calyculin A (50% inhibitory concentration [IC50], -2 nM) over okadaic acid (IC50, -100 nM). Calyculin A, but not okadaic acid, had profound effects on the in vitro replication and morphology of T. cruzi epimastigotes. Low concentrations of calyculin A (1 to 10 nM) caused growth arrest. Electron microscopic studies of the calyculin A-treated epimastigotes revealed that the organisms underwent duplication of organelles, including the flagellum, kinetoplast, and nucleus, but were incapable of completing cell division. At concentrations higher than 10 nM, or upon prolonged incubation at lower concentrations, the epimastigotes lost their characteristic elongated spindle shape and had a more rounded morphology. Okadaic acid at concentrations up to 1 11M did not result in growth arrest or morphological alterations to T. cruzi epimastigotes. Calyculin A, but not okadaic acid, was also a potent inhibitor of the dephosphorylation of 32P-labeled phosphorylase a by T. cruzi epimastigotes and metacyclic trypomastigote extracts. These inhibitor studies suggest that in T. cruzi, type 1 protein phosphatases are important for the completion of cell division and for the maintenance of cell shape.

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Background: Isolated hepatocytes removed from their microenvironment soon lose their hepatospecific functions when cultured. Normally hepatocytes are commonly maintained under limited culture medium supply as well as scaffold thickness. Thus, the cells are forced into metabolic stress that degenerate liver specific functions. This study aims to improve hepatospecific activity by creating a platform based on classical collagen sandwich cultures.
Results: The modified sandwich cultures replace collagen with self-assembling peptide, RAD16-I, combined with functional peptide motifs such as the integrin-binding sequence RGD and the laminin receptor binding sequence YIG to create a cell-instructive scaffold. In this work, we show that a plasma-deposited coating can be used to obtain a peptide layer thickness in the nanometric range, which in combination with the incorporation of functional peptide motifs have a positive effect on the expression of adult hepatocyte markers including albumin, CYP3A2 and HNF4-alpha.
Conclusions: This study demonstrates the capacity of sandwich cultures with modified instructive self-assembling peptides to promote cell-matrix interaction and the importance of thinner scaffold layers to overcome mass transfer problems. We believe that this bioengineered platform improves the existing hepatocyte culture methods to be used for predictive toxicology and eventually for hepatic assist technologies and future artificial organs.

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The bundle of stereocilia on inner ear hair cells responds to subnanometer deflections pro-duced by sound or head movement. Stereocilia are interconnected by a variety of links andalso carry an electron-dense surface coat. The coat may contribute to stereocilia adhesion orprotect from stereocilia fusion, but its molecular identity remains unknown. From a databaseof hair-cell-enriched translated proteins, we identify Polycystic Kidney and Hepatic Disease 1-Like 1 (PKHD1L1), a large, mostly extracellular protein of 4249 amino acids with a singletransmembrane domain. Using serial immunogold scanning electron microscopy, we showthat PKHD1L1 is expressed at the tips of stereocilia, especially in the high-frequency regionsof the cochlea. PKHD1L1-deficient mice lack the surface coat at the upper but not lowerregions of stereocilia, and they develop progressive hearing loss. We conclude that PKHD1L1is a component of the surface coat and is required for normal hearing in mice.

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Antarctic near-shore waters are amongst the most sensitive in the world to ocean acidification. Microbes occupying these waters are critical drivers of ecosystem productivity, elemental cycling and ocean biogeochemistry, yet little is known about their sensitivity to ocean acidification. A six-level, dose-response experiment was conducted using 650 L incubation tanks (minicosms) adjusted to a gradient in fugacity of carbon dioxide (fCO2) from 343 to 1641 µatm. The six minicosms were filled with near-shore water from Prydz Bay, East Antarctica, and the protistan composition and abundance was determined by microscopy during 18 days of incubation. No CO2-related change in the protistan community composition was observed during the initial 8 day acclimation period under low light. Thereafter, the response of both autotrophic and heterotrophic protists to fCO2 was species-specific. The response of diatoms was mainly cell size related; microplanktonic diatoms (> 20 µm) increased in abundance with low to moderate fCO2 (343-634 µatm) but decreased at fCO2 ≥ 953 µatm. Similarly, the abundance of Phaeocystis antarctica increased with increasing fCO2 peaking at 634 µatm. Above this threshold the abundance of micro-sized diatoms and P. antarctica fell dramatically, and nanoplanktonic diatoms (≤ 20 µm) dominated, therefore culminating in a significant change in the protistan community composition. Comparisons of these results with previous experiments conducted at this site show that the fCO2 thresholds are similar, despite seasonal and interannual differences in the physical and biotic environment. This suggests that near-shore microbial communities are likely to change significantly near the end of this century if anthropogenic CO2 release continues unabated, with profound ramifications for near-shore Antarctic ecosystem food webs and biogeochemical cycling.

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Crystalline metal�organic frameworks (MOFs) have emerged as a highly desirable class of solid-state materials. Some of their most attractive features include exceptionally high porosities as well as surface areas. A key aspect to the realization of high porosity is the removal of guest molecules from the framework while still maintaining its structural integrity (i.e., "activation"). This contribution highlights the strategies utilized to date for activating MOFs, including: (i) conventional heating and vacuum; (ii) solvent-exchange; (iii) supercritical CO2 (scCO2) exchange; (iv) freeze-drying; and (v) chemical treatment.

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Metal-organic frameworks comprising metal-carboxylate duster vertices and long, branched organic linkers are the most porous materials known, and therefore have attracted tremendous attention for many applications, including gas storage, separations, catalysis and drug delivery. To increase metal-organic framework porosity, the size and complexity of linkers has increased. Here we present a promising alternative strategy for constructing mesoporous metal-organic frameworks that addresses the size of the vertex rather than the length of the organic linker. This approach uses large metal-biomolecule clusters, in particular zinc-adeninate building units, as vertices to construct bio-MOF-100, an exclusively mesoporous metal-organic framework. Bio-MOF-100 exhibits a high surface area (4,300 m² g^-1), one of the lowest crystal densities (0.302 gcm^-3) and the largest metal-organic framework pore volume reported to date (4.3cm³g^-1).

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Recent progress in micro- and nanofabrication techniques enables the creation of hierarchically architected microlattices with dimensional control over six orders of magnitude, from centimeters down to nanometers. This hierarchical control facilitates the exploration of opportunities to exploit nano-sized material effects in structural materials. In this work, we present the fabrication, characterization, and properties of hollow metallic glass NiP microlattices. The wall thicknesses, deposited by electroless plating, were varied from 60 nm up to 600 nm, resulting in relative densities spanning from 0.02 to 0.2%. Uniaxial quasi-static compression tests revealed two different regimes in deformation: (i) Structures with a wall thickness above 150 nm failed by catastrophic failure at the nodes and fracture events at the struts, with significant micro- cracking and (ii) Lattices whose wall thickness was below 150 nm failed initially via buckling followed by significant plastic deformation rather than by post-elastic catastrophic fracture. This departure in deformation mechanism from brittle to deformable exhibited by the thin-walled structures is discussed in the framework of brittle-to-ductile transition emergent in nano-sized metallic glasses.
Key Words: Nanoscribe

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Most existing methods for additive manufacturing (AM) of metals are inherently limited to ~20-50?µm resolution, which makes them untenable for generating complex 3D-printed metallic structures with smaller features. We developed a lithography-based process to create complex 3D nano-architected metals with ~100?nm resolution. We first synthesize hybrid organic-inorganic materials that contain Ni clusters to produce a metal-rich photoresist, then use two-photon lithography to sculpt 3D polymer scaffolds, and pyrolyze them to volatilize the organics, which produces a >90 wt% Ni-containing architecture. We demonstrate nanolattices with octet geometries, 2 µm unit cells and 300-400-nm diameter beams made of 20-nm grained nanocrystalline, nanoporous Ni. Nanomechanical experiments reveal their specific strength to be 2.1-7.2 MPa g^(-1) cm^3, which is comparable to lattice architectures fabricated using existing metal AM processes. This work demonstrates an efficient pathway to 3D-print micro-architected and nano-architected metals with sub-micron resolution.
Key Words: Nanoscribe

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We investigate the mechanical behavior of 3D periodically architected metallic glass nanolattices, constructed from hollow beams of sputtered Zr-Ni-Al metallic glass. Nanolattices composed of beams with different wall thicknesses are fabricated by varying the sputter deposition time, resulting in nanolattices with median wall thicknesses of ~88 nm, ~57 nm, ~38 nm, ~30 nm, ~20 nm, and ~10 nm. Uniaxial compression experiments conducted inside a scanning electron microscope reveal a transition from brittle, catastrophic failure in thicker-walled nanolattices (median wall thicknesses of ~88 and ~57 nm) to deformable, gradual, layer-by-layer collapse in thinner-walled nanolattices (median wall thicknesses of ~38 nm and less). As the nanolattice wall thickness is varied, large differences in deformability are manifested through the severity of strain bursts, nanolattice recovery after compression, and in-situ images obtained during compression experiments. We explain the brittle-to-deformable transition that occurs as the nanolattice wall thickness decreases in terms of the "smaller is more deformable" material size effect that arises in nano-sized metallic glasses. This work demonstrates that the nano-induced failure-suppression size effect that emerges in small-scale metallic glasses can be proliferated to larger-scale materials by the virtue of architecting.
Key Words: Nanoscribe

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