Carbon nanotubes have previously been grown on Ni coated glass, aligned vertical to the substrate over a multi-centimeter square area1. Under vacuum, the aligned nanotubes were grown below 666° C (strain point of the best display glass) by plasma-enhanced hot filament, chemical vapor deposition. It was found, the size and alignment of the nanotubes could be varied by changing the dwell time and the thickness of the catalytic Ni layer by plasma etching. in more recent, ongoing studies, the size of carbon nanotubes is varied by changing the growth temperature and dwell time under acetylene/nitrogen atmosphere using chemical vapor deposition onto W and Ni coated Si.

Multiwall carbon nanotube films are grown using a thermally-activated chemical vapor deposition process. Thin Ni catalyst layers are sputtered onto W-coated Si(100) and reduced in a 600°C CO anneal. Nanotubes then grow at temperatures ranging from 630 - 790°C in an acetylene/nitrogen mixture.

The problem of phase retrieval from intensity measurements plays an important role in many fields of physical research, e.g. optics, electron and x-ray microscopy, crystallography, diffraction tomography and others. in practice the recorded images contain information only on the intensity distribution I(x,y) = ψ*ψ*= |A|2 of the imaging wave function ψ = A*exp(-iϕ) and the phase information (ϕ(x,y) is usually lost. in general, the phase problem can be solved either by special holographic/interferometric methods, or by noninterferometric approaches based on intensity measurements in far Fraunhofer zone or in the Fresnel zone at two adjacent planes orthogonal to the optical axis. The latter approach uses the transport-of-intensity equation (TIE) formalism, introduced originally by Teague [1] and developed later in [2]. Applications of TIE to nonmagnetic materials and magnetic inductance mapping were successfully made in [3,4]. However, this approach still needs further improvement both in mathematics and in practical solutions, since the result is very sensitive to many experimental parameters.

Due to their ability to undergo a refractive index change (Δn) induced by appropriate UV irradiation and thermal development, Photo-Thermo-Refractive (PTR) glasses are candidate materials for use in optical applications such as hologram recording, optical data storage, or spectral filters. Although this induced index modulation (Δn) has been characterized in terms of its optical ramifications, glass scientists are working to understand more clearly, the underlying mechanisms associated with the photo-induced crystallization process. For example, the phase, concentration and size of crystals responsible for the induced index change, the diffusion and growth process leading to the resultant optical behavior, and the precise role of the active components of PTR glasses, has yet to be completely elucidated. Numerous techniques have been employed to address these questions and this paper reports results of sample preparation and analysis of PTR glasses using Transmission Electron Microscopy (TEM).

Electronic phase separation is known to occur in complex oxides ranging from high-Tc superconductors to colossal magnetoresisitive (CMR) manganites. Accumulating experimental evidences show regions of temperature dependent conducting and insulating regions, whose exact origin is unknown. Theoretically, it is has been shown that these systems are unstable from the strong interplay between the lattice, charge and spin degrees of freedom.

The key to understand the electronic phase separation in complex oxides is the structure. Electron diffraction is the only probe that covers the length scales from angstroms to microns. Characterization at these length scales is critical (electronic phase separations are typically about nanometers in sizes). Traditionally, electron diffraction has been played important roles in discovering the new types of phase separations, but has contributed little to the quantitative understanding. The reason is the strong interaction of electrons with matter, which gives both strong inelastic background and multiple scattering.

Uncoated ceramics are difficult to analyze because specimen charging can reduce the energy of the electron beam at the specimen. This effect may decrease the measured k-ratio to a fraction of its expected value. Thin carbon coatings are the usual solution to this problem. However, the coating procedure takes time, and the same coating thickness also must be applied to the standard. in the environmental SEM (ESEM). surface charge can be mitigated at the higher accelerating voltages normally used for x-ray microanalysis. in the ESEM, electrons are accelerated toward an electrically biased electron detector producing a cascade of electrons and ions from the imaging gas (water vapor) as part of the secondary electron imaging process. Positive ions drift toward the specimen and neutralize negative surface charge; however, the degree of neutralization is a function of a number of operating variables.

Recently, a promising new route to prepare nano phase composites with fine transition metal particles (2 - 50nm) has been proposed via dehydroxylation and dehydration process. Thermal and mechanical dehydroxylation process has also been used to form ultra fine powders of NiO-Ni(OH). We have found a substantially increased carbonation rate at room temperature (RT) for partially dehydroxylated brucite (Mg(OH)2) single crystal fragments. BET measurements confirm the increase in the surface area of partially dehydroxylated (90%) single-crystal Mg(OH)2 fragments, which directly contributes to the increase in carbonation reactivity. As dehydroxylation proceeds rapidly in a TEM column, due to high vacuum and electron beam effects, the atomic level nature of the process has not been understood until recently.6 We have observed the development of nanocrystals during in situdehydroxylation of Mg(OH)2.

Experiments were performed using a PHILIPS-430 electron microscope operated at 300KV, fitted with a differentially pumped environmental-cell (E-cell) and a Gatan Imaging Filter (GIF).

The application of modern transmission electron microscopes (TEM) in catalytic research has accelerated the progress in understanding the mechanism of catalytic reactions. For instance, using environmental TEM, the novel glide shear defect process was revealed as an efficient mechanism for the release of the structural oxygen of vanadyl pyrophosphate in the n-butane oxidation [1]. On the other hand, electron energy-loss spectroscopy (EELS), which is nowadays commercially available on modern TEM, appears unknown in the catalytic community. in fact, core-loss EELS is a powerful tool to identify the chemical state of elements and to study the modification of this sate in various compounds.

Fig.l shows EELS-spectra of various vanadium oxides in which the oxidation state of vanadium varies from 2+ (VO) to 5+ (V2O5). The first two features, marked as V L3 and V L2 edges, are attributed to the excitations from V 2p3/2and V 2p1/2core levels to the unoccupied V 3dstates, respectively.

Carbon nanotube (NT) growth by chemical vapor deposition (CVD) requires a catalyst -typically a transition metal- to nucleate NT growth because of the low synthesis temperatures as compared to arc-discharge or laser ablation methods. The catalyst can be introduced to the CVD system by preprepared nano-scale catalyst particles sitting on fine support powders, thin catalyst films deposited on substrates by sputter deposition, or floating catalysts. The floating-catalyst CVD method is an in-situprocess in which the organo-metallic precursors (e.g. metallocenes) decomposed to form nanoscale catalyst particles. Floating catalyst methods can produce both multi-wall carbon nanotubes (MWNTs), single-wall nanotubes, and even C-N nanotubes and facilitate continuous growth processes. in this study we employ a variety of electron imaging, diffraction and spectroscopy techniques to investigate the growth mechanisms and kinetics of multi-walled NTs (MWNTs) produced by the floating-catalyst CVD method.

The vasculature of two recessive dwarf mutants, nana-1 (nal) (FIG 1) and nana-2 (na2) (FIG 2) of maize (Zea mays)were studied. All the plants used in this study were grown at the field station of University of Western Ontario, London, Ontario, Canada, in the summer of 2000. The specimens were fixed in methanol, serially sectioned with a razor blade using a specially made jig. The image was obtained by using a modified Acer 620T flat-bed scanner in liquid (Cheng et al., 2001). The optical sections were obtained by twophoton florescence microscopy using an Olympus Fluorview FL300 confocal microscope equipped with a Spectra-Physics Mai-Tai tunable ultra-fast Ti-sapphire laser. Excitation wavelengths was set at 780nm NIR with a pulse width of l00fs, <550nm autofluorescence was detected. Extended focus views were generated by using AutoQuant's AutoVisualize-3D™ software.

Different from the parallel arranged longitudinal vascular bundles commonly found in the internodes of wild type, nal/nalhas a complex stem vasculature (FIG 3)(Cheng et al., 2000a; 2000b).

The semaphorin family consists of a set of secreted and transmembrane proteins which contain a domain of approximately 500 amino acids called the semaphorin domain. The investigation of the role of semaphorin proteins in the nervous system has established them as chemorepellents of axons. Recent studies have identified the semaphorin proteins on the surface of cells in the immune system and in the genomes of two lytic viruses. These strongly suggest the possible involvement of the semaphorin proteins in the immune system. This study aims to understand the expression patterns of four semaphorin genes, Sema3B, Sema4A, Sema4F, and Sema6C in the lymphoid tissues of wild type mice. These proteins were chosen to represent the three subfamilies III, IV, and VI. The first family contains secreted proteins which have immunoglobulin domains (III), the second contains transmembrane proteins which have immunoglobulin domains (IV), and the third contains transmembrane proteins which do not have immunoglobulin domains (VI).

During fertilization in the sea squirt, Ascidia ceratodes,the penetration process of requires mitochondrial translocation, a process that defines sperm activation in this species, to generate the driving force for passage through the vitelline coat. When a sperm cell come into contact with an egg, the mitochondrion translocates off the head and migrates along the tail via an actimmyosin-dependent process. The presence of actin and myosin on the head and tail has been demonstrated. However, the nature of the relative distribution of filamentous actin (F-actin) and monomeric actin (G-actin) has not been thoroughly studied. And, whereas the signaling cascade that leads to myosin activation has been studied, the events leading to actin polymerization and whether it is required for mitochondrial translocation has not.

This project addresses two research questions: What is the distribution of F-actin and G-actin in unactivated and activated sperm cells? And, can preexisting F-actin support mitochondrial translocation or must actin polymerization occur simultaneously with the mitochondrial translocation process?

The earliest events in ascidian fertilization require sperm-egg recognition, sperm activation and penetration of the egg's protective barriers before sperm-egg fusion can occur. Species selective recognition is known to depend on recognition by sperm of egg N-acetylglucosamine sites. Binding to these sites triggers the defining event of ascidian sperm activation called mitochondrial translocation. in this process, the mitochondrion becomes anchored to follicles cells surrounding the egg and then rounds up, moves to the base of the head and translocates onto the tail. This actimmyosin-dependent process provides the force for penetration. Activation of myosin depends on a signaling pathway that leads to internal Ca2+ release and external Ca2+ entry.

In order for actimmyosin interactions to provide the force for penetration, the mitochondrion must be anchored to the outer surface of the egg complex. Presumably this anchor must also attach to actin filaments that serve as the track for the mitochondrial translocation process.

Among land plants, lower vascular plants produce the most elaborate of all male gametes. in order to characterize the degree of variability in sperm cell architecture among ferns, this scanning electron microscope study was undertaken on three highly disparate genera: Ceratopteris(a derived leptosporangiate fern) Angiopteris(a derived eusporangiate fern) and Psilotum(a putatively basal eusporangiate fern).

Mature gametophytes were placed in 0.01M phosphate buffer (pH ca. 7.2) or distilled water until spermatozoids were released. Gametophyte portions were removed and the spermatozoid suspension fixed with 2% glutaraldehyde in 0.05M phosphate buffer. Post-fixation utilized 1% aqueous osmium tetroxide for lhr, followed by rinsing and dehydration in ethanol (10 min @ 25, 50, 75 and 100%). The dehydrated pellet was suspended in 100% hexamethyldisilazane, immediately centrifuged and the pellet deposited onto clean glass coverslips. Specimens were dried at 60°C, sputtered with ca. 350 A of palladium/gold and imaged in a Hitachi S570 SEM.

Toxic dinoflagellates gained notoriety for their devastation to coastal and island economies, causing damages totaling in the millions of dollars that included losses of harvestable resources, clean-up costs, as well as cancellation of holiday reservations in popular tourist/recreational areas.3 These red tide blooms sparked an urgency for obtaining information pertaining to the dynamics of toxin production, but understanding the mechanisms of toxin production have proven to be difficult to pin point. This study tested the hypothesis that cells grown under various light intensities undergo structural and compositional changes and served as a basis for future biochemical studies of Prorocentrumhoffmanianum.

We examined ultrastructural changes to the chloroplast in cells from monocultures of Prorocentrum hoffmanianum grown in three different light intensities, via a transmission electron microscope and a fluorescent light microscope. The full or normal growth chamber intensity of ca. 5000 lux represented the control group referred to as the full light treatment.

Mature sperm cells of Ceratopteris richardiiare spiraled over three revolutions and contain a locomotory apparatus with approximately 70 flagella attached at the cell anterior (Fig. 1). Abundant organelles are dispersed along the inner surface of an elongated, coiled nucleus (Figs. 1, 3, 8). The cytoskeleton comprises a network of microfilaments that encases the nucleus (Fig. 6) and two distinct microtubule arrays: a microtubular ribbon (spline) and flagella with anchoring basal bodies (Fig. 3). This study uses light, fluorescence, transmission electron (TEM), and scanning electron microscopy (SEM) to characterize cell organization in a motility impaired mutant sperm line of Ceratopteris.Because motility mutations likely involve the cytoskeleton, emphasis was placed on observing microtubule and actin arrays in the mutant compared to wild-type spermatozoids. Protocols follow Hoffman and Vaughn for TEM and Schmitt and Renzaglia for SEM. Microfilament arrays in relation to the nucleus were examined by rhodamine-phalloidin and DAPI fluorescence.

The field number of the objective lens limits the field of view in a conventional compound microscope; even at very low magnification, the microscope does not allow observation of large pieces of specimen at once. This made the observation of organs and large pieces of tissue sections inconvenient. in the course of studying the development of maize stem, we encountered the need of digitizing large hand sections for 3D reconstruction. Splicing a series of images that are taken at different positions to form a montage is not acceptable, because the jointed image suffers from mismatch due to lens distortion. Considering the resolution needed in our study, one alternative is to use a consumer flatbed scanner designed for a personal computer. in order to adapt the conventional scanner for wet tissue scanning, an Acer 620TPC flatbed scanner, equipped with a trans-illuminator, was modified (FIG 1).

Thermal environment exerts a strong influence on lizard life histories by constraining seasonal activity time, fecundity, growth, and embryonic development. in cold climates, extending the duration of egg retention within the female's body permits embryos to develop more rapidly than would be possible at ambient nest temperatures. The duration of egg retention time in the oviduct is largely constrained by the ability of the growing embryo to uptake oxygen and release carbon dioxide. Parchment shelled eggs of most squamates (lizards, snakes, and amphisbaenians) while permeable to water and gases, also acts as a diffusive barrier to gas exchange. As a result, most taxa with extended egg retention exhibit a concomitant reduction in eggshell thickness.

To assess the influence of thermal environment on egg retention time, I sampled eggs from the lizards Sceloporus occidentalis and Sceloporus graciosus(Phrynosomatidae) from three populations at high, intermediate, and low elevation, in the San Gabriel Mountains of Southern California.

A database cataloguing SEM micrographs of pollen specimens can be useful for several purposes. The primary reason would be for educational purposes. The images could be used to study pollen structure, as well as the relationship between pollen and pollinator species. Identification of pollen can be of potential use for medical purposes (such as combating allergic reactions to pollen), and for comparison in a forensic investigation. At the Biology Department of California State University, San Bernardino an ongoing project is underway to construct a database of pollen samples, focusing on local species. The micrographs are created at the Electron Microscope and Images Analysis Center located in the School of Natural Sciences at Cal State San Bernardino using a Hitachi S-2700 SEM. The database will be made available to the public and updated periodically via the Biology Department website (http://biology.csusb.edu).

All specimens were first fixated by placing the pollen grains in a syringe filter and injecting a 2% formaldehyde/4% glutaraldehyde formula and incubating overnight.

Electrodeposition of molybdenum dioxide (using the step edges of highly oriented pyrolytic graphite as nucleation templates) is used to form precursor nanowires ranging in diameter from 10 nm to one micron with many exceeding one-half millimeter in length. Subsequent treatment with hydrogen gas above 500°C reduces the wires to conductive metallic molybdenum. (Science, December 15, 2000, 290 (5499) 2120, selected as cover story). Currently, this is the only method which exists to create millions of ordered nanowire arrays with such high aspect ratios. A film of either polystyrene or cyanoacrylate polymer is used to lift the wires off of the conductive graphite substrate making electronically isolated wires. Electronically isolated wires such as these hold promise to be sensors, electronic interconnects or as precursors for growing more complex electrodeposited circuitry.

The discovery of a method to deposit nanowires is just the beginning. By using a piece of a double-sided copper-clad circuit board as a support, the polymer containing nanowires can be made into a robust sensor device.

Introduction: “In time, and with water, everything changes.” —Leonardo da Vinci The crystallization of soluble salts in porous building materials is a widespread weathering process that results in damage to important monuments and archaeological sites. Salt weathering by thenardite (sodium sulfate) and mirabilite (sodium sulfate decahydrate) is especially destructive, yet is still not fully understood. Halite (sodium chloride) in contrast, is one of the least damaging salts. Previous work has also demonstrated the importance of airflow in salt weathering. Here we present new data that help explain why sodium sulfate is so damaging and also show how crystallization modifiers and changes in airflow can reduce salt damage in laboratory experiments.

Damage Mechanism: The behavior of sodium sulfate was documented using saturated solutions and oolites from Monks Park limestone (a stone well known to be vulnerable to salt damage) as test samples. Damage was evaluated based on the degree of cracking of the oolite.