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Heavy-electron metals exhibit highly correlated electronic behavior at liquid helium temperatures, with conduction-electron masses some hundred times the free-electron mass. Whether "normal," antiferromagnetic, or superconducting, their electronic behavior differs drastically from their ordinary metallic counterparts. The physical origin of the large mass and unusual superconducting and magnetic properties is the strong coupling between the conduction electrons and the local f-electron moment fluctuations characteristic of these materials.

Wood, as a natural biomass material, has long been a research focus. Superhydrophobic modified wood, in particular, has shown great promise in a myriad of engineering applications such as architecture, landscape, and shipbuilding. However, commercial development has encountered significant resistance due to preparation difficulties and sometimes unsatisfactory performance. In this study, hydrophobic/superhydrophobic wood comodified with methyltrimethoxysilane (MTMS) and 1 H ,1 H ,2 H ,2 H -perfluorodecyltrimethoxysilane (PFDTMS) was fabricated by a one-step sol-gel method that uses an in situ growth process. Low-molecular-weight MTMS was allowed to permeate the three-dimensional porous wood interior. Then, acid-base catalysts were used to regulate the hydrolytic condensation process of MTMS and PFDTMS composite silanes to generate micro/nano hierarchical structures with low surface energy on the wood surface. The physicochemical characteristics of modified wood were investigated and the reaction mechanism established. The modified wood displayed excellent internal hydrophobicity/surface superhydrophobicity, water-moisture resistance, and dimensional stability at low fluorine concentrations. The resulting superhydrophobic surface provided stain resistance, self-cleaning ability, and loading capacity in water while exhibiting good mechanochemical stability; wood mechanical strength was also enhanced. This methodology created a superhydrophobic surface and bulk hydrophobization of wood in one step. Beyond wood, this approach is expected to provide a promising approach for functional modification of other porous composite materials.

The wetting behavior of fiber networks, which are central to many research and industrial applications, can be difficult to predict accurately owing to their complex, heterogeneous structure. The cylindrical pore model, widely used to interpret and predict the forced wetting of hydrophobic porous materials, often does not yield correct results when working with fibrous networks like paper substrates and non-woven fabrics. This is because these materials exhibit variation in pore size, fiber length, and fiber diameter, as well as a reentrant pore geometry. Quantitative prediction of the critical wetting resistance of hydrophobized papers to arbitrary entrant liquids requires a more sophisticated analytical approach that considers this unique fibrous structure and the effect of stochastic variations within the pore matrix. In this work, we directly measure the critical breakthrough pressure for different porous substrates across various wetting entrant liquids. To isolate the effects of the structure and stochastics on critical wetting behavior of fibrous networks, we analyze additional materials strategically chosen for their subsets of structural features. Ultimately, we formulate a method that demonstrates physical reasonableness, numerical accuracy, and the ability to elucidate the effects of pore size, pore size distribution, fiber diameter, fiber diameter distribution, surface wettability, and liquid surface tension on critical breakthrough pressure of liquids through hydrophobic fibrous networks.

A fully enclosed paper microfluidic device has been fabricated using pentafluoroethane (PFE) plasma deposition followed by O 2 plasma etching. Structures with one and two non-interacting, fully enclosed hydrophilic channels were generated in a single paper sheet using metal masks. Furthermore, by performing an additional O 2 plasma step with a secondary mask, pinholes were created at the reaction zones for reagent loading. Finally, to demonstrate the functionality of the device, a glucose assay was performed. Quantitative analysis of glucose assays showed that the device can be used for the clinically relevant range of glucose. To our knowledge, this is the first time that such structures have been fabricated without paper stacking. Multi-layer devices have enhanced functionality relative to a single channel device, because the design space for creating networks of channels within the paper substrate is greatly expanded. The fluid-filled channels in the fabricated device are isolated, thereby preventing contamination due to handling and environmental exposure. Fluid evaporation can be inhibited by sealing the device with adhesive tape without contaminating the enclosed channels. The method described is a dry process and compatible with roll-to-roll technology, thus facilitating large scale production. The novel method to fabricate enclosed μ-PADs overcomes many of the limitations experienced with current approaches and thus offers an alternative means to develop low-cost point-of-care diagnostics for resource-limited settings.

Roughness contrast patterns were generated on copper surfaces by a simple one-step site-selective oxidation process using a felt-tipped ink pen masking method. The patterned surface exhibited strong underwater oil wettability contrast which allows oil droplet confinement. Oil droplets placed on two patterned smooth dots (reservoirs) connected by a patterned smooth channel will spontaneously exchange liquid as a result of Laplace pressure differences until their shapes have reached equilibrium. In our experiments, residual solubility of the oil in water was overcome by using saturated oil-in-water solutions as the aqueous medium. In the saturated solution, the dependence of pattern geometry and oil viscosity on transported volume and the flow rate in the underwater oil transport process was investigated for dichloromethane and hexadecane. Experimental results were in good agreement with a simple model for Laplace pressure-driven flow. Depending on droplet curvatures, oil can be transported from large to small reservoirs or vice versa. The model predictions enable the design of reservoir and channel dimensions to control liquid transport in the water-solid surface-oil system. The patterning technique was extended to more complex patterns with multiple reservoirs for smart oil separation and mixing processes. The concepts demonstrated in this study can be employed to seed droplet arrays with specific initial drop volumes and achieve subsequent droplet mixing at controlled flow rates for potential lab-on-a-chip applications ranging from oil-droplet-based miniature reactors and sensors to high-throughput assays.

The economical use of water-repellent coatings on polymeric materials in commercial and industrial applications is limited by their mechanical wear robustness and long-term durability. In this study, we demonstrate that polyethylene terephthalate (PET) fabric modified with inorganic, methyltrimethoxysilane (MTMS)-based coatings shows excellent resistance against various types of wear damage, thereby mimicking superhydrophobic biological materials. These features were facilitated by the rational design of coating processing that also enabled tunable hierarchical surface structure. A series of custom and standard testing protocols revealed that coating-to-substrate adhesion was remarkably high, as was the resistance to various mechanical abradents. The most intriguing characteristic observed during aging and abrasion cycles was the enhancement in non-wettability or 'rejuvenation' reflected by water droplet roll-off behavior, a characteristic of self-cleaning materials. Water-repellent properties of coated polyester were also enhanced by prolonged thermal annealing and were maintained after custom laundry. The developed technology offers opportunities to design low cost, durable and functional textiles for both indoor and outdoor applications., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Bacterial adhesion to stainless steel 316L (SS316L), which is an alloy typically used in many medical devices and food processing equipment, can cause serious infections along with substantial healthcare costs. This work demonstrates that nanotextured SS316L surfaces produced by electrochemical etching effectively inhibit bacterial adhesion of both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus , but exhibit cytocompatibility and no toxicity toward mammalian cells in vitro. Additionally, the electrochemical surface modification on SS316L results in formation of superior passive layer at the surface, improving corrosion resistance. The nanotextured SS316L offers significant potential for medical applications based on the surface structure-induced reduction of bacterial adhesion without use of antibiotic or chemical modifications while providing cytocompatibility and corrosion resistance in physiological conditions., Competing Interests: The authors declare no competing financial interest.

Underwater oil droplets stretched and pinned by dual-dot oleophilic patterns on a superoleophobic substrate have been split into two nearly equal-volume daughter droplets using an underwater superoleophobic blade at substantially lower cutting speeds than reported in previous studies. A "liquid exchange model" based on Laplace pressure-driven liquid transport has been proposed to explain the mechanism of the underwater droplet split process. The dependence of droplet geometrical shape (curvature) and liquid properties (surface tension, viscosity) on the critical cutting speed that allows equal-volume split was investigated. Results demonstrate that critical cutting speed increases with increased curvature and surface tension of the split droplet, and decreases with increased droplet viscosity, which agrees with the proposed model. The ability to reproducibly split a single bulk oil droplet into daughter droplets with nearly equal volume facilitates the development of new functions for underwater microreactors.

Surface modification of cellulose-based paper, which displays roll-off properties for water and oils (surface tension ≥23.8 mN·m -1 ) and good repellency toward n-heptane (20.1 mN·m -1 ), is reported. Droplets of water, diiodomethane, motor oil, hexadecane, and decane all "bead up", i.e., exhibit high contact angles, and roll off the treated surface under the influence of gravity. Unlike widely used approaches that rely on the deposition of nanoparticles or electrospun nanofibers to create superamphiphobic surfaces, our method generates a hierarchical structure as an inherent property of the substrate and displays good adhesion between the film and substrate. The two-step combination of plasma etching and vapor deposition used in this study enables fine-tuning of the nanoscale roughness and thereby facilitates enhanced fundamental understanding of the effect of micro- and nanoscale roughness on the paper wetting properties. The surfaces maintain their "roll-off" properties after dynamic impact tests, demonstrating their mechanical robustness. Furthermore, the superamphiphobic paper has high gas permeability due to pore-volume enhancement by plasma etching but maintains the mechanical flexibility and strength of untreated paper, despite the presence of nanostructures. The unique combination of the chemical and physical properties of the resulting superamphiphobic paper is of practical interest for a range of applications such as breathable and disposable medical apparel, antifouling biomedical devices, antifingerprint paper, liquid packaging, microfluidic devices, and medical testing strips through a simple surface etching plus coating process.

Engaging individual members of clinical teams in practice improvement initiatives is a challenge. In this commentary, we first summarize evidence supporting enhanced practitioner engagement through the creation of a work environment that builds on mutually respectful relationships and valued interdependencies. We then propose a phased, collaborative process that employs practice talk, a term that describes naturally occurring, collegial conversations among members of clinical teams. Planned interactions among team members, facilitated by individuals trained in dialogic techniques, enable health care providers and support staff to share their experiences and expertise, agree on what improvements they would like to make, and test the success of these changes. Participants would be encouraged to express their own suggestions for better practice and disclose strategies that are already working. Dissent would be regarded as an opportunity rather than a barrier. Iterative, sense-making conversations would generate a shared vision, enabling team members to engage in the entire process. Given that practice improvement ultimately depends on frontline providers, we encourage the exploration of innovative engagement strategies that will enable entire clinical teams to develop the collaborative learning skills needed to accomplish their goals., (© 2015 The Alliance for Continuing Education in the Health Professions, the Society for Academic Continuing Medical Education, and the Council on Continuing Medical Education, Association for Hospital Medical Education.)

Cellulose-based paper remains a vital component of modern day society; however, its use is severely limited in certain applications because of hydrophilic and oleophilic properties. In this manuscript we present a novel method to create superamphiphobic paper by combining the control of fiber size and structure with plasma etching and fluoropolymer deposition. The heterogeneous nature of the paper structure is drastically different from that of artificially created superamphiphobic surfaces. By refining the wood fibers, smaller diameter fibers (fibrils) are created to support fluid droplets. After oxygen plasma etching and deposition of a fluoropolymer film, paper samples are able to support motor oil contact angles of 149 ± 3°, although these structures readily absorb n-hexadecane. Exchange of water in the pulp solution with sec-butanol provides additional control over fiber spacing to create superamphiphobic substrates with contact angles >150° for water, ethylene glycol, motor oil, and n-hexadecane.

In this work, we present a method to render stainless steel surfaces superhydrophobic while maintaining their corrosion resistance. Creation of surface roughness on 304 and 316 grade stainless steels was performed using a hydrofluoric acid bath. New insight into the etch process is developed through a detailed analysis of the chemical and physical changes that occur on the stainless steel surfaces. As a result of intergranular corrosion, along with metallic oxide and fluoride redeposition, surface roughness was generated on the nano- and microscales. Differences in alloy composition between 304 and 316 grades of stainless steel led to variations in etch rate and different levels of surface roughness for similar etch times. After fluorocarbon film deposition to lower the surface energy, etched samples of 304 and 316 stainless steel displayed maximum static water contact angles of 159.9 and 146.6°, respectively. However, etching in HF also caused both grades of stainless steel to be susceptible to corrosion. By passivating the HF-etched samples in a nitric acid bath, the corrosion resistant properties of stainless steels were recovered. When a three step process was used, consisting of etching, passivation and fluorocarbon deposition, 304 and 316 stainless steel samples exhibited maximum contact angles of 157.3 and 134.9°, respectively, while maintaining corrosion resistance.

CZTS: Atlanta. A supercritical CO(2) continuous-flow reactor is employed to deposit micro- and nanoparticles of copper zinc tin sulfide (CZTS), a promising material for thin-film solar cells, onto a silicon wafer. The image shows a chemical map of deposited CZTS particles (scale bar: 15 μm), and a Raman spectrum with a peak characteristic of CZTS., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We have studied the electronic characteristics of multilayer epitaxial graphene under a perpendicularly applied electric bias. Ultraviolet photoemission spectroscopy measurements reveal that there is notable variation of the electronic density-of-states in valence bands near the Fermi level. Evolution of the electronic structure of graphite and rotational-stacked multilayer epitaxial graphene as a function of the applied electric bias is investigated using first-principles density-functional theory including interlayer van der Waals interactions. The experimental and theoretical results demonstrate that the tailoring of electronic band structure correlates with the interlayer coupling tuned by the applied bias. The implications of controllable electronic structure of rotationally fault-stacked epitaxial graphene grown on the C-face of SiC for future device applications are discussed., (This journal is © The Royal Society of Chemistry 2012)

This communication presents a novel label-free biosensing method to monitor DNA hybridization via infrared attenuated total reflection (IR-ATR) spectroscopy using surface-modified ZnSe waveguides. Well-defined carboxyl-terminated monolayers were formed at H-terminated ZnSe by direct photochemical activation. Chemical activation of the acidic function was obtained by using succinimide/carbodiimide linkers. The sequential surface modification reactions were characterized by XPS and IR-ATR spectroscopy. Finally, a single stranded DNA probe with a C6-NH(2) 5' modifier was coupled to the ester-terminated surface via peptide bonding, and the hybridization of the immobilized DNA sequence with its complementary strand was directly evaluated by IR-ATR spectroscopy in the mid-infrared (MIR) spectral regime (3-20 μm) without requiring an additional label. A shift of the vibrational modes corresponding to the phosphodiester and deoxyribose structures of the DNA backbone was observed. Hence, this approach substantiates a novel strategy for label-free DNA detection utilizing mid-infrared spectroscopy as the optical sensing platform.

Current integrated circuit (IC) manufacturing consists of more than 800 process steps, nearly all of which involve reactions at surfaces that significantly impact device yield and performance. From initial surface preparation through film deposition, patterning, etching, residue removal, and metallization, an understanding of surface reactions and interactions is critical to the successful continuous scaling, yield, and reliability of electronic devices. In this review, some of the most important surface reactions that drive the development of microelectronic device fabrication are described. The reactions discussed do not constitute comprehensive coverage of this topic in IC manufacture but have been selected to demonstrate the importance of surface/interface reactions and interactions in the development of new materials, processing sequences, and process integration challenges. Specifically, the review focuses on surface reactions related to surface cleaning/preparation, semiconductor film growth, dielectric film growth, metallization, and etching (dry and wet).

Superoleophobic surfaces display contact angles >150 degrees with liquids that have lower surface energies than does water. The design of superoleophobic surfaces requires an understanding of the effect of the geometrical shape of etched silicon surfaces on the contact angle and hysteresis observed when different liquids are brought into contact with these surfaces. This study used liquid-based metal-assisted etching and various silane treatments to create superoleophobic surfaces on a Si(111) surface. Etch conditions such as the etch time and etch solution concentration played critical roles in establishing the oleophobicity of Si(111). When compared to Young's contact angle, the apparent contact angle showed a transition from a Cassie to a Wenzel state for low-surface-energy liquids as different silane treatments were applied to the silicon surface. These results demonstrated the relationship between the re-entrant angle of etched surface structures and the contact angle transition between Cassie and Wenzel behavior on etched Si(111) surfaces.

Improvement of the robustness of superhydrophobic surfaces is critical in order to achieve commercial applications of these surfaces in such diverse areas as self-cleaning, water repellency and corrosion resistance. In this study, the mechanical robustness of superhydrophobic surfaces was evaluated on hierarchically structured silicon surfaces. The effect of two-scale hierarchical structures on robustness was investigated using an abrasion test and the results compared to those of superhydrophobic surfaces fabricated from polymeric materials and from silicon that contains only nanostructures. Unlike the polymeric and nanostructure-only surfaces, the hierarchical structures retained superhydrophobic behavior after mechanical abrasion.

Superhydrophobic paper substrates were patterned with high surface energy black ink using commercially available desktop printing technology. The shape and size of the ink islands were designed to control the adhesion forces on water drops in two directions, parallel ('drag-adhesion') and perpendicular ('extensional-adhesion') to the substrate. Experimental data on the adhesion forces shows good agreement with classical models for 'drag' (Furmidge equation) and 'extensional' adhesion (modified Dupré equation). The tunability of the two adhesion forces was used to implement four basic unit operations for the manipulation of liquid drops on the paper substrates: storage, transfer, mixing and sampling. By combining these basic functionalities it is possible to design simple two-dimensional lab-on-paper (LOP) devices. In our 2D LOP prototype, liquid droplets adhere to the porous substrate, rather than absorbing into the paper; as a result, liquid droplets remain accessible for further quantitative testing and analysis, after performing simple qualitative on-chip testing. In addition, the use of commercially available desktop printers and word processing software to generate ink patterns enable end users to design LOP devices for specific applications.

A method for the preparation of inorganic superhydrophobic silica coatings using sol-gel processing with tetramethoxysilane and isobutyltrimethoxysilane as precursors is described. Incorporation of isobutyltrimethoxysilane into silica layers resulted in the existence of hydrophobic isobutyl surface groups, thereby generating surface hydrophobicity. When combined with the surface roughness that resulted from sol-gel processing, a superhydrophobic surface was achieved. This surface showed improved UV and thermal stability compared to superhydrophobic surfaces generated from polybutadiene by plasma etching. Under prolonged UV tests (ASTM D 4329), these surfaces gradually lost superhydrophobic character. However, when the as-prepared superhydrophobic surface was treated at 500 degrees C to remove the organic moieties and covered with a fluoroalkyl layer by a perfluorooctylsilane treatment, the surface regained superhydrophobicity. The UV and thermal stability of these surfaces was maintained upon exposure to temperatures up to 400 degrees C and UV testing times of 5500 h. Contact angles remained >160 degrees with contact angle hysteresis approximately 2 degrees.

Silicon is employed in a variety of electronic and optical devices such as integrated circuits, photovoltaics, sensors, and detectors. In this paper, Au-assisted etching of silicon has been used to prepare superhydrophobic surfaces that may add unique properties to such devices. Surfaces were characterized by contact angle and contact angle hysteresis. Superhydrophobic surfaces with reduced hysteresis were prepared by Au-assisted etching of pyramid-structured silicon surfaces to generate hierarchical surfaces. Consideration of the Laplace pressure on hydrophobized hierarchical surfaces gives insight into the manner by which contact is established at the liquid/composite surface interface. Light reflectivity from the etched surfaces was also investigated to assess application of these structures to photovoltaic devices.

Pinhole-free insulation of micro- and nanoelectrodes is the key to successful microelectrochemical experiments performed in vivo or in combination with scanning probe experiments. A novel insulation technique based on fluorocarbon insulation layers deposited from pentafluoroethane (PFE, CF3CHF2) plasmas is presented as a promising electrical insulation approach for microelectrodes and combined atomic force microscopy-scanning electrochemical microscopy (AFM-SECM) probes. The deposition allows reproducible and uniform coating, which is essential for many analytical applications of micro- and nanoelectrodes such as, e.g., in vivo experiments and SECM experiments. Disk-shaped microelectrodes and frame-shaped AFM tip-integrated electrodes have been fabricated by postinsulation focused ion beam (FIB) milling. The thin insulation layer for combined AFM-SECM probes renders this fabrication technique particularly useful for submicro insulation providing radius ratios of the outer insulation versus the disk electrode (RG values) suitable for SECM experiments. Characterization of PFE-insulated AFM-SECM probes will be presented along with combined AFM-SECM approach curves and imaging.

Most of the artificial superhydrophobic surfaces that have been fabricated to date are not biodegradable, renewable, or mechanically flexible and are often expensive, which limits their potential applications. In contrast, cellulose, a biodegradable, renewable, flexible, inexpensive, biopolymer which is abundantly present in nature, satisfies all the above requirements, but it is not superhydrophobic. Superhydrophobicity on cellulose paper was obtained by domain-selective etching of amorphous portions of the cellulose in an oxygen plasma and subsequently coating the etched surface with a thin fluorocarbon film deposited via plasma-enhanced chemical vapor deposition using pentafluoroethane as a precursor. Variation of plasma treatment yielded two types of superhydrophobicity : "roll-off" (contact angle (CA), 166.7 degrees +/- 0.9 degrees ; CA hysteresis, 3.4 degrees +/- 0.1 degrees ) and "sticky" (CA, 144.8 degrees +/- 5.7 degrees ; CA hysteresis, 79.1 degrees +/- 15.8 degrees ) near superhydrophobicity. The nanometer scale roughness obtained by delineating the internal roughness of each fiber and the micrometer scale roughness which is inherent to a cellulose paper surface are robust when compared to roughened structures created by traditional polymer grafting, nanoparticle deposition, or other artificial means.

In this study, plasma-polymerized films are evaluated as enrichment membranes deposited at the surface of mid-infrared transparent waveguides for liquid-phase chemical sensing utilizing evanescent field absorption spectroscopy. Fluorocarbon films were deposited onto zinc selenide (ZnSe) waveguides from plasma-polymerized pentafluoroethane (CF(3)CHF(2)) vapor. Excellent optical transmission of ZnSe waveguides after plasma deposition confirms compatibility of the infrared transparent substrate with this low-temperature, solvent-free film deposition process. The liquid-phase enrichment characteristics for plasma membranes were investigated via evanescent field absorption spectroscopy of a model analyte (tetrachloroethylene); the limits of detection were below 300 ppb (v/v) in water. Plasma-polymerized films are known for their excellent mechanical and chemical stability, while offering tunable chemical and physical characteristics during the deposition process. Future application of this coating strategy for depositing robust enrichment membranes with tunable batch production capability imparts an attractive route toward application-oriented development of next-generation mid-infrared chemical sensors applicable in harsh environments.

Silicon surface hydrophobicity has been varied by using silane treatments on silicon pyramid surfaces generated by KOH anisotropic etching. Results demonstrated that by altering the surface hydrophobicity, the apparent contact angle changed in accord with the Wenzel equation for surface structures with inclined side walls. Hierarchical structures were also constructed from Si pyramids where nanostructures were added by Au-assisted electroless HF/H2O2 etching. Surface hydrophobicity and superhydrophobicity were achieved by surface modification with a variety of silanes. Stability of the Cassie state of superhydrophobicity is described with respect to the Laplace pressure as indicated by the water droplet meniscus in contact with the hierarchical structures. The contact angle hysteresis observed is also discussed with respect to water/substrate adhesion.

Surfaces of hexagonally packed silica spheres have been functionalized with silanes containing different hydrocarbon or fluorocarbon chains. The resulting chemical and physical structures were studied to establish the effect of surface hydrophobicity on the measured contact angles on the rough surfaces. The results were used to assess the effects of surface modifications on the parameters in the Cassie equation. To achieve superhydrophobicity via a biomimetic approach, we created two-scale structures by first forming hexagonally packed SiO2 spheres, followed by Au deposition on the spheres and heat treatment to form Au nanoparticles on sphere surfaces. Contact angles over 160 degrees were achieved. This work provides improved understanding of the effect of the surface roughness and solid surface fraction on superhydrophobicity.

Electrowetting is one approach to reducing the interfacial tension between a solid and a liquid. In this method, an electrical potential is applied across the solid/liquid interface which modifies the wetting properties of the liquid on the solid without changing the composition of the solid and liquid phases. Electrowetting of aligned carbon nanotube (CNT) films is investigated by the sessile drop method by dispensing deionized (DI) water or 0.03 M NaCl droplets (contacted by Au wire) onto aligned CNT films assembled on a copper substrate. The results demonstrate that electrowetting can greatly reduce the hydrophobicity of the aligned CNTs; the contact angle saturation for DI water and 0.03 M NaCl droplets occurs at 98 and 50 degrees , respectively. The combined effects of the geometrical roughness and the electrical potential on the contact angle are briefly discussed and modeled. Such a strategy may be invoked to controllably reduce the interfacial tension between carbon nanotubes (CNTs) and polymer precursors when infiltrating the monomers into the prealigned nanotube films.

A novel method is presented to monitor carbon nanotube (CNT) growth by formation of CNT stacks. By this process, CNT growth kinetics are investigated for densely packed CNT films in the gas-diffusion-controlled regime. CNT stacks are fabricated by water-assisted selective etching and the cyclic introduction of ethylene into the chemical vapor deposition (CVD) reactor. Formation of the CNT stacks allows monitoring of the CNT growth evolution, thereby providing insight into the growth kinetics. A parabolic increase of CNT length versus time is observed, indicating a gas-diffusion-controlled growth mode. The densely packed, well-aligned CNT films act as porous barrier layers to the diffusion of ethylene precursor to the catalyst nanoparticles, since these films form via a base-growth mode under the conditions invoked in our system. By adjustment of CNT growth time and temperature, a quantitative time-evolution analysis is performed to investigate the CNT growth model and extract the gas precursor mass transfer coefficient in the CNT films. The self-diffusion of gases in the densely packed CNT films is found to be Knudsen diffusion with a diffusion coefficient on the order of 10(-4) cm(2)/s.

To circumvent the high carbon nanotube (CNT) growth temperature and poor adhesion with the substrates that currently plague CNT implementation, we proposed using CNT transfer technology enabled by open-ended CNTs. The process is featured with separation of CNT growth and CNT device assembly. Field emission testing of the as-assembled CNT devices is in good agreement with the Fowler-Nordheim (FN) equation, with a field enhancement factor of 4,540. This novel technique shows promising applications for positioning CNTs on temperature-sensitive substrates and for the fabrication of field emitters, electrical interconnects, and thermal management structures in microelectronics packaging.

Well-aligned, high-purity carbon nanotube (CNT) stacks of up to 10 layers fabricated in one batch process have been formed by water-assisted selective etching of carbon atoms. Etching takes place at the CNT caps as well as at the interface between CNTs and metal catalyst particles. This simple process generates high-purity CNTs and opens the CNT ends by removing the nanotube caps. High-resolution transmission electron microscopy indicates that the process does not damage CNT wall structures. A mechanism for stacked growth of CNT layers is proposed.

Considerable effort has been expended on theoretical studies of superhydrophobic surfaces with two-tier (micro and nano) roughness, but experimental studies are few due to the difficulties in fabricating such surfaces in a controllable way. The objective of this work is to experimentally study the wetting and hydrophobicity of water droplets on two-tier rough surfaces for comparison with theoretical analyses. To compare wetting on micropatterned silicon surfaces with wetting on nanoscale roughness surfaces, two model systems are fabricated: carbon nanotube arrays on silicon wafers and carbon nanotube arrays on carbon nanotube films. All surfaces are coated with 20 nm thick fluorocarbon films to obtain low surface energies. The results show that the microstructural characteristics must be optimized to achieve stable superhydrophobicity on microscale rough surfaces. However, the presence of nanoscale roughness allows a much broader range of surface design criteria, decreases the contact angle hysteresis to less than 1 degrees , and establishes stable and robust superhydrophobicity, although nanoscale roughness could not increase the apparent contact angle significantly if the microscale roughness dominates.

A new method to extract complex refractive indices of films with biaxial symmetry from polarized transmission and reflection spectra is described. Theoretical analysis demonstrates that the reflectance/transmittance ratio (R/T ratio) of two films of different thicknesses but with the same optical anisotropy is a simple function of the refractive index (n) and extinction coefficient (k). For films with biaxial symmetry, components of n and k on symmetric axes can be extracted from either s- or p-polarized R/T ratios if the film thickness values are known. The R/T ratio method can generate n and k spectra within a particular wavelength range without assuming a specific relationship among n, k, and wavelength, which is an advantage over many currently available techniques. The R/T ratio method is used to extract the anisotropic complex refractive indices of a polyimide film with known uniaxial symmetry. The resultant n and k spectra compare well with simulations based on known n and k values. The accuracy of n and k spectra is affected mostly by data error in reflection and transmission spectra collection, thickness variation across sample films, and error in sample alignment.

A technique is formulated to determine both thickness and refractive indices of free-standing films with biaxial symmetry from polarized transmission spectra. The films must be transparent and show little dispersion in refractive indices in the wavelength range where the transmission spectra are collected. Methods are proposed to correct the errors caused by imperfect polarization of incident radiation and thickness variation across the sampling area. Anisotropic refractive indices and thickness of poly(biphenyl dianhydride-p-phenylenediamine) films which exhibit uniaxial optical anisotropy are determined from polarized transmission spectra. The refractive index and thickness values compare well to those obtained from waveguide prism coupler and profilometer measurements.

The BPD/DS, if properly performed, has the best long-term weight loss of any bariatric operation. It is easy to reverse or revise, has the least marginal ulcers, cures the highest percentage of co-morbidities, has the least failures, and permits normal although smaller meals. It is our opinion that the BPD/DS should be considered as the gold standard bariatric operation.

Objectives: To examine issues of employment and race for persons with spinal cord injury (SCI), by assessing the type of work that was being done before and after injury and by placing this in the context of patterns for the general population., Design: Retrospective, cross-sectional analysis., Setting: Centers funded as part of the federally sponsored Model Spinal Cord Injury Systems (MSCIS) Project., Participants: Two samples: 5925 African Americans and whites with SCI who are part of the MSCIS and a subset of 577 people with SCI., Interventions: Not applicable., Main Outcome Measures: Demographic information, occupational status, employment rate, job census codes, Craig Hospital Assessment and Reporting Technique-Short Form, and Satisfaction With Life Scale., Results: Racial disparities were found in employment rates before injury and at 1, 5, 10, 15, and 20 years after SCI. Differences were also found in the types of jobs that were held before SCI with patterns for participants similar to those of African Americans and whites in the general population. No differences were found in the types of jobs held by African Americans and whites with SCI at 1 year after injury. After injury, African Americans had lower economic self-sufficiency scores, regardless of employment status, and lower social integration scores among those who were not employed., Conclusions: Racial disparities found in employment patterns among persons with SCI mirrored patterns among the general population.

We present a multiscale simulation of a crack in silicon under tensile loading that is consistent with experiment; fracture is brittle with a modest lattice-trapping energy barrier to crack propagation. Our multiscale molecular-dynamics simulation has a tight-binding description of bonding near the crack tip embedded in an empirical-potential (EP) region. Forces on atoms in the tight-binding region are computed using a Green's function method. Comparing our multiscale simulation with EP simulations shows that the EP models severely overestimate lattice trapping, explaining the failure of the Griffith criterion and the dramatic differences in crack morphology. A two-length-scale model for the lattice-trapping energy barrier correctly predicts the critical load for brittle fracture. We argue that lattice trapping plays an important role in the brittle-to-ductile transition.

Objective: A study was designed to directly compare individuals with tetraplegia and paraplegia to further explore neurological and functional outcomes and their impact on the expense of rehabilitation when controlling for level of completeness, age at the time of injury, and length of stay., Methods: A sample was drawn from the National Spinal Cord Injury Database consisting of 2069 individuals, 1005 with paraplegia and 1064 with tetraplegia., Results: Significant demographic differences were found between the 2 groups with regard to age, ethnicity, marital status, and employment status. Significant differences were found between the groups with regard to all individual outcome variables (p < .001) and expenses (p < .05). On average, patients with paraplegic injuries evidenced greater change and efficiency on a functional independence measure than patients with tetraplegia. In contrast, patients with tetraplegia showed greater changes and efficiency with regard to ASIA Motor Index scores. Higher rehabilitation expenses were found for patients with tetraplegia.

Objective: To examine the ability of the Motor Index Score (MIS), in combination with demographic variables, to predict return to work during a 3-year period for individuals with spinal cord injury (SCI)., Methods: Prospectively collected data, between 1986 and 1995, submitted to the National Spinal Cord Injury Statistical Center were analyzed to determine the prediction of return to work utilizing variables of education, ethnicity, age, marital status, gender, and MIS. Individuals, aged 18 to 65 yrs, employed at the time of their injury, were evaluated at discharge from rehabilitation and at 1 (YR1), 2 (YR2), and 3 (YR3) years postinjury (sample sizes of 1,857, 1,486, and 1,177, respectively)., Results: The most important predictors of return to work were education, MIS, ethnicity, and age at onset of SCI. These variables resulted in a high rate of accuracy for predicting across all 3 yrs (YR1, 81%; YR2, 82%; YR3, 77%)., Conclusions: The ability to predict return to work after SCI was shown utilizing MIS and demographic variables, with nearly 80% accuracy. This suggests that return to work after SCI is a dynamic process, with the level of importance of each variable changing with time postinjury.

Background: This paper evaluates biliopancreatic diversion combined with the duodenal switch, forming a hybrid procedure which is a combination of restriction and malabsorption., Methods: The evaluation is of the first 440 patients undergoing this procedure who had had no previous bariatric surgery. The mean starting weight was 183 kg, with 41% of our patients considered super morbidly obese (BMI > 50)., Results: There was an average maximum weight loss of 80% excess weight by 24 months postoperation; this continued at a 70% level for 8 years. Major complications were found in almost 9% of the cases. There were two perioperative deaths, one from pulmonary embolism and one from acute pulmonary obstruction. There were 36 type II diabetics, all of whom have discontinued medication following the surgery. Seventeen revisions were performed to correct excess weight loss and low protein levels. There have been no marginal ulcers, no cases of dumping syndrome, no foreign material used, and the procedure is a pyloric saving procedure which is functionally reversible., Conclusions: This operation has vastly improved the lives of seriously obese patients with many comorbidities. All type II diabetics have essentially been cured of their disease. The procedure was tolerated well and patients are quite satisfied. There was minimal regain of weight with this method.

The authors describe a vertical banded gastroplasty with complete division of the staple-line performed via the laparoscope

Unwed pregnant adolescents were contrasted with nulligravid teenagers seeking contraception. Pregnant subjects were less likely to employ or plan to use contraceptives. Gravid subjects more often described their boyfriends as happy about the pregnancy and expressed a desire for a pregnancy. Nulligravid youngsters described their parents as more disapproving of their premarital sexual activity. There is a need for counseling programs, including adolescents of both sexes, and aimed at the modification of attitudes toward contraception.