Atomistic Insights into Interfacial Optimization Mechanism for Achieving Ultralow-Friction Amorphous Carbon Films under Solid-Liquid Composite Conditions

The combination of fluid lubricants and textured amorphous carbon (a-C) can provide an ultralow friction state, which can improve the reliability and service life of dynamic machinery. However, the coupling effects of the contact pressure and oil content on the friction-reducing efficiency is still lack of study, and the corresponding friction mechanism is also not fully understood, which cannot be achieved by experiment due to the limitation of in situ characterization. In this study, using the reactive molecular dynamics simulation, the insight into the evolution of interfacial structures induced by both contact pressures and oil contents on a-C surface was systematically investigated to explore the fundamental mechanism. In particular, the friction difference between textured and untextured a-C films was evaluated comparatively. Results indicate that the tribological performance strongly depends on the interfacial lubrication state, which is jointly determined by the oil content and contact pressure; the best operating condition to achieve ultralow friction coefficient (0.002) is obtained, and the evolution of friction coefficient with oil content and contact pressure is highly dominated by the lubricant mobility, cross-linking between mating a-C surfaces, or competition/synergy of the H stress state from the lubricant with interfacial passivation. Furthermore, the difference in friction reduction between textured and untextured systems is unveiled; with the increase of contact pressure, the role of texturing a-C surface in antifriction changes from positive to negative effect, which is related to the transformation of interfacial hybridized structure and anomalous flow of lubricant. These results can significantly enhance the understanding of composite lubrication systems through computation and also provide a roadmap for the R&D of the advanced lubrication system according to the working conditions.

Atomic-Scale Understanding on the Tribological Behavior of Amorphous Carbon Films under Different Contact Pressures and Surface Textured Shapes

The textured design of amorphous carbon (a-C) film can significantly improve the tribological performance and service life of moving mechanical components. However, its friction dependence on different texture shapes, especially under different load conditions, remains unclear. In particular, due to the lack of information regarding the friction interface, the underlying friction mechanism has still not been unveiled. Therefore, the effects of contact pressure and textured shapes on the tribological behavior of a-C films under dry friction conditions were comparatively studied in this work by reactive molecular dynamics simulation. The results show that under low contact pressure, the tribological property of a-C film is sensitive to the textured shape, and the system with a circular textured surface exhibits a lower friction coefficient than that with a rectangular textured surface, which is attributed to the small fraction of unsaturated bonds. However, the increase of contact pressure results in the serious reconstruction and passivation of the friction interface. On the one hand, this induces a growth rate of friction force that is much smaller than that of the normal load, which is followed by a significant decrease in the friction coefficient with contact pressure. On the other hand, the destruction or even disappearance of the textured structure occurs, weakening the difference in the friction coefficient caused by different textured shapes of the a-C surface. These results reveal the friction mechanism of textured a-C film and provide a new way to functionalize the a-C as a protective film for applications in hard disks, MEMS, and NEMS.

Autonomous Interfacial Assembly of Polymer Nanofilms via Surfactant-Regulated Marangoni Instability

Interfacial polymerization (IP) provides a versatile platform for fabricating defect-free functional nanofilms for various applications, including molecular separation, energy, electronics, and biomedical materials. Unfortunately, coupled with complex natural instability phenomena, the IP mechanism and key parameters underlying the structural evolution of nanofilms, especially in the presence of surfactants as an interface regulator, remain puzzling. Here, we interfacially assembled polymer nanofilm membranes at the free water-oil interface in the presence of differently charged surfactants and comprehensively characterized their structure and properties. Combined with computational simulations, an in situ visualization of interfacial film formation discovered the critical role of Marangoni instability induced by the surfactants via various mechanisms in structurally regulating the nanofilms. Despite their different instability-triggering mechanisms, the delicate control of the surfactants enabled the fabrication of defect-free, ultra-permselective nanofilm membranes. Our study identifies critical IP parameters that allow us to rationally design nanofilms, coatings, and membranes for target applications.

Insights into Superlow Friction and Instability of Hydrogenated Amorphous Carbon/Fluid Nanocomposite Interface

Hydrogenated amorphous carbon (a-C:H) film exhibits the superlubricity phenomena as rubbed against dry sliding contacts. However, its antifriction stability strongly depends on the working environment. By composting with the fluid lubricant, the friction response and fundamental mechanisms governing the low-friction performance and instability of a-C:H remain unclear, while they are not accessible by experiment due to the complicated interfacial structure and the lack of advanced characterization technique in situ. Here, we addressed this puzzle with respect to the physicochemical interactions of a-C:H/oil/graphene nanocomposite interface at atomic scale. Results reveal that although the friction capacity and stability of system are highly sensitive to the hydrogenated degrees of mated a-C:H surfaces, the optimized H contents of mated a-C:H surfaces are suggested in order to reach the superlow friction or even superlubricity. Interfacial structure analysis indicates that the fundamental friction mechanism attributes to the hydrogenation-induced passivation of friction interface and squeezing effect to fluid lubricant. Most importantly, the opposite diffusion of fluid oil molecules to the sliding direction is observed, resulting in the transformation of the real friction interface from a-C:H/oil interface to oil/oil interface. These outcomes enable an effective manipulation of the superlow friction of carbon-based films and the development of customized solid-fluid lubrication systems for applications.

Correction: Novel two-dimensional tetrahexagonal boron nitride with a sizable band gap and a sign-tunable Poisson's ratio

Correction for 'Novel two-dimensional tetrahexagonal boron nitride with a sizable band gap and a sign-tunable Poisson's ratio' by Mehmet Emin Kilic et al., Nanoscale, 2021, 13, 9303-9314, DOI: 10.1039/D1NR00734C.

Novel two-dimensional tetrahexagonal boron nitride with a sizable band gap and a sign-tunable Poisson's ratio

By performing first-principles calculations, a new two-dimensional (2D) boron nitride (th-BN) with perfectly ordered arrangements of tetragonal and hexagonal rings is predicted to be energetically, dynamically, thermally, and mechanically stable. The unique structure endows th-BN with anisotropic mechanical, electronic, and optical properties. Remarkably, th-BN exhibits exceptional mechanical properties such as high in-plane stiffness and sign-tunable Poisson's ratio (PR). The PR of th-BN gradually decreases with the increase of axial strain and even becomes negative at a very small strain (∼2%), which is novel, thereby offering the ability to become non-auxetic, auxetic, and partially auxetic 2D nanomaterials depending on the strain rate and direction. The structure can withstand tensile strain as large as 36%, and shows ultrahigh ideal strength that can even outperform graphene and hexagonal BN. The th-BN is a natural 2D semiconductor with an indirect wide band gap of 4.49 eV. The band gap can be tuned by applying lattice strain and hydrogenation. The full hydrogenated th-BN exhibits an indirect-to-direct band gap transition. The th-BN shows high optical absorption in the ultraviolet region. The optical absorption spectrum is highly direction-dependent and tunable by strain, suitable for high-performance optoelectronic device applications. Furthermore, th-BN can be stacked into two different configurations, and are dynamically stable and exhibit exotic electronic properties. The desirable direct band gap and anisotropic effective mass of the th-C/th-BN heterostructure suggest that th-BN can be a suitable substrate for tetrahexcarbon.

Automated Measurements of Key Morphological Features of Human Embryos for IVF

A major challenge in clinical In-Vitro Fertilization (IVF) is selecting the highest quality embryo to transfer to the patient in the hopes of achieving a pregnancy. Time-lapse microscopy provides clinicians with a wealth of information for selecting embryos. However, the resulting movies of embryos are currently analyzed manually, which is time consuming and subjective. Here, we automate feature extraction of time-lapse microscopy of human embryos with a machine-learning pipeline of five convolutional neural networks (CNNs). Our pipeline consists of (1) semantic segmentation of the regions of the embryo, (2) regression predictions of fragment severity, (3) classification of the developmental stage, and object instance segmentation of (4) cells and (5) pronuclei. Our approach greatly speeds up the measurement of quantitative, biologically relevant features that may aid in embryo selection.

Tailoring the Nanostructure of Graphene as an Oil-Based Additive: toward Synergistic Lubrication with an Amorphous Carbon Film

Graphene exhibits great potential as a lubricant additive to enhance the antifriction capacity of moving mechanical components in synergism with amorphous carbon (a-C) as a solid lubricant. However, it is particularly challenging for experiments to accurately examine the friction dependence on the physical nanostructure of the graphene additive and the corresponding interfacial reactions because of the inevitable complexity of the graphene structure fabricated in experiments. Here, we address this puzzle regarding the coeffect of the size and content of the graphene additive at the a-C interface using reactive molecular dynamics simulations. Results reveal that the friction-reducing behavior is more sensitive to graphene size than content. For each graphene structure, with increasing content, the friction coefficient always decreases first and then increases, while the friction behavior exhibits significant dependence on the graphene size when the graphene content is fixed. In particular, the optimized size and content of the graphene additive are suggested, in which an excellent antifriction behavior or even superlubricity can be achieved. Analysis of the friction interface indicates that with increasing graphene size, the dominated low-friction mechanism transforms from the high mobilities of the base oil and graphene additive in synergism to the passivation and graphene-induced smoothing of the friction interface. These outcomes disclose the roadmap for developing a robust solid-liquid synergy lubricating system.

Enabling reversible redox reactions in electrochemical cells using protected LiAl intermetallics as lithium metal anodes

Rechargeable electrochemical cells with metallic anodes are of increasing scientific and technological interest. The complex composition, poorly defined morphology, heterogeneous chemistry, and unpredictable mechanics of interphases formed spontaneously on the anodes are often examined but rarely controlled. Here, we couple computational studies with experimental analysis of well-defined LiAl electrodes in realistic electrochemical environments to design anodes and interphases of known composition. We compare phase behavior, Li binding energies, and activation energy barriers for adatom transport and study their effects on the electrochemical reversibility of battery cells. As an illustration of potential practical benefits of our findings, we create cells in which LiAl anodes protected by Langmuir-Blodgett MoS2 interphases are paired with 4.1 mAh cm-2 LiNi0.8Co0.1Mn0.1O2 cathodes. These studies reveal that small- and larger-format (196 mAh, 294 Wh kg-1, and 513 Wh liter-1) cells based on protected LiAl anodes exhibit high reversibility and support stable Li migration during recharge of the cells.

Role of the carbon source in the transformation of amorphous carbon to graphene during rapid thermal processing

A fast transfer-free synthesis of a graphene structure can be successfully achieved by Ni-catalysed transformation of amorphous carbon (a-C) during rapid thermal processing, but the role of the a-C structure in the a-C-to-graphene transformation is still unclear. In this paper, the dependence of the transformation of a-C to graphene, the diffusion behaviour of C, and the graphene quality on the a-C structures was comparatively investigated by reactive molecular dynamics simulation and Ni was selected as a catalyst. The results demonstrated that different a-C structures affected the diffusion of C into Ni layers and the re-dissolving behaviour of the grown graphitic structures, and thus dominated the remnant number of C atoms, which played a critical role in the formation and quality of graphene.

Accelerated Data-Driven Accurate Positioning of the Band Edges of MXenes

Functionalized MXene has emerged a promising class of two-dimensional materials having more than tens of thousands of compounds, whose uses may range from electronics to energy applications. Other than the band gap, these properties rely on the accurate position of the band edges. Hence, to synthesize MXenes for various applications, a prior knowledge of the accurate position of their band edges at an absolute scale is essential; computing these with conventional methods would take years for all the MXenes. Here, we develop a machine learning model for positioning the band edges with GW level of accuracy having a minimum root-mean-squared error of 0.12 eV. An intuitive model is proposed based on the combination of Perdew-Burke-Ernzerhof band edge and vacuum potential having a correlation of 0.93 with GW band edges. These models can be utilized to identify MXenes for a desired application in an accelerated manner.

Transformation of amorphous carbon to graphene on low-index Ni surfaces during rapid thermal processing: a reactive molecular dynamics study

The transformation of amorphous carbon to graphene on different Ni surfaces during rapid thermal processing was explored using reactive molecular dynamics simulation. Due to the difference in activation energy, Ni surfaces affected the diffusion behavior of C into Ni and thus modulated the remnant number of C atoms, dominating the formation and quality of graphene, which accorded with the developed empirical equation.

Nonocclusive Mesenteric Ischaemia Induced by Diltiazem Overdose: A Case Report

Acute mesenteric ischaemia is a rare complication of calcium channel blocker (CCB) overdose. A previous study reported a case of mesenteric ischaemia induced by poisoning with CCBs other than diltiazem. We present a case of nonocclusive mesenteric ischaemia (NOMI) induced by diltiazem poisoning. Through this case report, we wish to emphasize that the clinicians should keep the possibility of intestinal ischaemia in mind from the early phase of calcium channel blocker poisoning. In addition, close monitoring and intense abdominal examination including the abdominal computed tomography scan should be done if CCBs poisoning patients complained of an abdominal pain.

Bacterial Contamination of Computer and Hand Hygiene Compliance in the Emergency Department

Introduction

The aim of this study was to determine the degree and nature of bacterial contamination of computer equipment in three Korean emergency departments (ED).

Methods

Hand hygiene practices of ED doctors and nurses were observed before contact with computer equipment. Microbiological swab samples were obtained from 112 multiple-user computer keyboards and electronic mice in the ED of three teaching hospitals. Isolated organisms were identified by a clinical microbiologist using Gram stain, colony morphology, and susceptibility test.

Results

Of the 112 samples, 103 (92.0%) showed growth of organisms on culture. Thirty-eight (33.9%) pieces of computer equipment yielded multiple bacterial species. Coagulase-negative Staphylococcus was the most common microorganism isolated (85.7%). Methicillin-resistant Staphylococcus aureus was obtained from two keyboards in two hospitals (1.8%). Hand hygiene compliance was observed on 29.9% occasions. Hand hygiene compliance after patient contact (38.0%) was higher than after other environmental contact (20.7%).

Conclusions

Multiple user computer equipment in the ED may serve as reservoirs for nosocomial infection. Hand hygiene should be performed before and after using all ED equipment, including computer equipment.

Bacterial Contamination of Computer and Hand Hygiene Compliance in the Emergency Department

Introduction

The aim of this study was to determine the degree and nature of bacterial contamination of computer equipment in three Korean emergency departments (ED).

Methods

Hand hygiene practices of ED doctors and nurses were observed before contact with computer equipment. Microbiological swab samples were obtained from 112 multiple-user computer keyboards and electronic mice in the ED of three teaching hospitals. Isolated organisms were identified by a clinical microbiologist using Gram stain, colony morphology, and susceptibility test.

Results

Of the 112 samples, 103 (92.0%) showed growth of organisms on culture. Thirty-eight (33.9%) pieces of computer equipment yielded multiple bacterial species. Coagulase-negative Staphylococcus was the most common microorganism isolated (85.7%). Methicillin-resistant Staphylococcus aureus was obtained from two keyboards in two hospitals (1.8%). Hand hygiene compliance was observed on 29.9% occasions. Hand hygiene compliance after patient contact (38.0%) was higher than after other environmental contact (20.7%).

Conclusions

Multiple user computer equipment in the ED may serve as reservoirs for nosocomial infection. Hand hygiene should be performed before and after using all ED equipment, including computer equipment. (Hong Kong j.emerg.med. 2012;19:387-393)

Unexpected Roles of Interstitially Doped Lithium in Blue and Green Light Emitting Y2O3:Bi3+: A Combined Experimental and Computational Study

To enhance the photoluminescence of lanthanide oxide, a clear understanding of its defect chemistry is necessary. In particular, when yttrium oxide, a widely used phosphor, undergoes doping, several of its atomic structures may be coupled with point defects that are difficult to understand through experimental results alone. Here, we report the strong enhancement of the photoluminescence (PL) of Y₂O₃:Bi³⁺ via codoping with Li⁺ ions and suggest a plausible mechanism for that enhancement using both experimental and computational studies. The codoping of Li⁺ ions into the Y₂O₃:Bi³⁺ phosphor was found to cause significant changes in its structural and optical properties. Interestingly, unlike previous reports on Li⁺ codoping with several other phosphors, we found that Li⁺ ions preferentially occupy interstitial sites of the Y₂O₃:Bi³⁺ phosphor. Computational insights based on density functional theory calculations also indicate that Li⁺ is energetically more stable in the interstitial sites than in the substitutional sites. In addition, interstitially doped Li⁺ was found to favor the vicinity of Bi³⁺ by an energy difference of 0.40 eV in comparison to isolated sites. The calculated DOS showed the formation of a shallow level directly above the unoccupied 6p orbital of Bi³⁺ as the result of interstitial Li⁺ doping, which may be responsible for the enhanced PL. Although the crystallinity of the host materials increased with the addition of Li salts, the degree of increase was minimal when the Li⁺ content was low (<1 mol %) where major PL enhancement was observed. Therefore, we reason that the enhanced PL mainly results from the shallow levels created by the interstitial Li⁺.

Simulation Protocol for Prediction of a Solid-Electrolyte Interphase on the Silicon-based Anodes of a Lithium-Ion Battery: ReaxFF Reactive Force Field

We propose the ReaxFF reactive force field as a simulation protocol for predicting the evolution of solid-electrolyte interphase (SEI) components such as gases (C₂H₄, CO, CO₂, CH₄, and C₂H₆), and inorganic (Li₂CO₃, Li₂O, and LiF) and organic (ROLi and ROCO₂Li: R = -CH₃ or -C₂H₅) products that are generated by the chemical reactions between the anodes and liquid electrolytes. ReaxFF was developed from ab initio results, and a molecular dynamics simulation with ReaxFF realized the prediction of SEI formation under real experimental conditions and with a reasonable computational cost. We report the effects on SEI formation of different kinds of Si anodes (pristine Si and SiO_x), of the different types and compositions of various carbonate electrolytes, and of the additives. From the results, we expect that ReaxFF will be very useful for the development of novel electrolytes or additives and for further advances in Li-ion battery technology.

Monolayer BC2: an ultrahigh capacity anode material for Li ion batteries

Uniformly doped monolayered BC₂sheets show the highest ever reported specific capacity of 1667 mA h g⁻¹for B doped graphene sheets.

Mechanistic Insight into the Chemical Exfoliation and Functionalization of Ti3C2 MXene

MXene, a two-dimensional layer of transition metal carbides/nitrides, showed great promise for energy storage, sensing, and electronic applications. MXene are chemically exfoliated from the bulk MAX phase; however, mechanistic understanding of exfoliation and subsequent functionalization of these technologically important materials is still lacking. Here, using density-functional theory we show that exfoliation of Ti3C2 MXene proceeds via HF insertion through edges of Ti3AlC2 MAX phase. Spontaneous dissociation of HF and subsequent termination of edge Ti atoms by H/F weakens Al-MXene bonds. Consequent opening of the interlayer gap allows further insertion of HF that leads to the formation of AlF3 and H2, which eventually come out of the MAX, leaving fluorinated MXene behind. Density of state and electron localization function shows robust binding between F/OH and Ti, which makes it very difficult to obtain controlled functionalized or pristine MXene. Analysis of the calculated Gibbs free energy (ΔG) shows fully fluorinated MXene to be lowest in energy, whereas the formation of pristine MXene is thermodynamically least favorable. In the presence of water, mixed functionalized Ti3C2Fx(OH)1-x (x ranges from 0 to 1) MXene can be obtained. The ΔG values for the mixed functionalized MXenes are very close in energy, indicating the random and nonuniform functionalization of MXene. The microscopic understanding gained here unveils the challenges in exfoliation and controlling the functionalization of MXene, which is essential for its practical application.

Isolation of pristine MXene from Nb4AlC3 MAX phase: a first-principles study

Complete chemical transformation of MAX (Nb₄AlC₃) into pristine MXene (Nb₄C₃) in the presence of LiF.

Atomistics of the lithiation of oxidized silicon (SiOx) nanowires in reactive molecular dynamics simulations

The atomistic lithiation mechanism of silicon oxides (SiO_x) is clarified using the ReaxFF reactive molecular dynamics simulation.

A comparative first-principles study of the lithiation, sodiation, and magnesiation of black phosphorus for Li-, Na-, and Mg-ion batteries

Lithiation, sodiation, and magnesiation of black phosphorus are clarified and compared using first-principles calculations.

Functionalization effect on a Pt/carbon nanotube composite catalyst: a first-principles study

Chemical interactions between Pt and both pristine and defective carbon nanotubes (CNTs) that were functionalized with various surface functional groups, including atomic oxygen (–O), atomic nitrogen (–N), hydroxyl (–OH) and amine (–NH₂) groups, were investigated through first-principles calculations.

High performance gas diffusion layer with hydrophobic nanolayer under a supersaturated operation condition for fuel cells

Reliable operation of a proton exchange membrane fuel cell requires proper water management to prevent water flooding in porous carbon materials such as the gas diffusion layer (GDL). In contrast to the conventional GDL that uses the "wet" dip-coating process with solvent and expensive polytetrafluoroethylene, we have proposed a novel GDL with a controlled hydrophobic silicone (i.e., hexamethyldisiloxane) nanolayer by a highly efficient and cost-effective "dry" deposition process. The GDL with the nanolayer exhibited an increased contact angle, decreased contact angle hysteresis, and suppressed water condensation. Even though the GDL with the nanolayer had a higher electrical resistance than the pristine GDL, the cell performance of the GDL with an optimum nanolayer thickness of 8.6 nm was practically the same as that of the pristine GDL under normal operating conditions. Under a supersaturated condition, the GDL with optimum nanolayer thickness exhibited much higher cell performance than the pristine GDL over all current densities due to enhanced hydrophobicity. Long-term operational stability and dynamic response of the GDL with the nanolayer were much improved over those of the pristine GDL.

Pressure induced manifold enhancement of Li-kinetics in FCC fullerene

The reduction of the diffusion energy barrier for Li in electrodes is one of the required criteria to achieve better performances in Li ion batteries. Using density functional theory based calculations, we report a pressure induced manifold enhancement of Li-kinetics in bulk FCC fullerene. Scanning of the potential energy surface reveals a diffusion path with a low energy barrier of 0.62 eV, which reduces further under the application of hydrostatic pressure. The pressure induced reduction in the diffusion barrier continues till a uniform volume strain of 17.7% is reached. Further enhancement of strain increases the barrier due to the repulsion caused by C-C bond formation between two neighbouring fullerenes. The decrease in the barrier is attributed to the combined effect of charge transfer triggered by the enhanced interaction of Li with the fullerene as well as the change in profile of the local potential, which becomes more attractive for Li. The lowering of the barrier leads to an enhancement of two orders of magnitude in Li diffusivity at room temperature making pressurized bulk fullerene a promising artificial solid electrolyte interface (SEI) for a faster rechargeable battery.

Detecting gas molecules via atomic magnetization

Adsorptions of gas molecules were found to alter the directions and magnitudes of magnetic moments of transition metal (Co, Fe) atoms adsorbed on graphene.

Hierarchical structures of AlOOH nanoflakes nested on Si nanopillars with anti-reflectance and superhydrophobicity

A novel method to fabricate ultra-low reflective Si surfaces with nanoscale hierarchical structures is developed by the combination of AlOOH or boehmite nanoflakes nested on plasma-etched Si nanopillars. Using CF4 plasma etching, Si surfaces are nanostructured with pillar-like structures by selective etching with self-masking by fluorocarbon residues. AlOOH nanoflakes are formed by Al thin film coating with various thicknesses and subsequent immersion in boiling water, which induces the formation of nanoscale flakes through the hydrolysis reaction. AlOOH nanoflakes are formed on Si nanopillared surfaces for hierarchical structures, which are coated with a low-surface-energy material, resulting in a higher water wetting angle of over 150° and a very low contact angle hysteresis of less than 5°, and implying a self-cleaning surface. Reflectance reduced to 5.18% on average on hierarchical nanostructures in comparison to 9.63% on the Si nanopillar surfaces only. We found that Si nanopillars reduced reflection for wavelengths ranging from 200 to 1200 nm while AlOOH nanoflakes reduced reflection for wavelengths longer than 600 nm.

A molecular dynamics simulation study on the initial stage of Si(001) oxidation under biaxial strain

We have studied the very early stage of the room temperature oxidation of the externally-strained Si(001) surface using molecular dynamics simulation. It was found that the different treatment history of the sample under the same strain resulted in the difference in the number density of dimer. The as-prepared samples of different treatment history with 12.15% strain were used to investigate the initial oxidation behavior of Si(001). 500 times of independent deposition of single oxygen molecule onto the random position of clean Si(001) surface was simulated. Oxidation behavior was statistically analyzed for various dimer density of the surface which is dependent on strain-treatment history. Oxygen uptake and penetration depth profile showed an important role of dimers on the surface oxidation behavior.

Decoupling free-carriers contributions from oxygen-vacancy and cation-substitution in extrinsic conducting oxides

The intrinsic oxygen-vacancies and the extrinsic dopants are two major fundamental free-carrier sources for the extrinsic conducting oxides, such as Sn-doped In(2)O(3). Yet, the individual contributions of the above two free-carrier sources to the total carrier concentrations have never been unraveled. A carrier-concentration separation model is derived in this work, which can define the individual contributions to the total carrier concentration from the intrinsic oxygen-vacancies and the extrinsic dopants, separately. The individual contributions obtained from the present carrier-concentration separation model are verified by the two-state trapping model, photoluminescence, and positron annihilation lifetime (PAL) spectroscopy. In addition, the oxygen-vacancy formation energy of the Sn:In(2)O(3) thin film is determined to be 0.25 eV by PAL spectroscopy.

Bioinspired steel surfaces with extreme wettability contrast

The exterior structures of natural organisms have continuously evolved by controlling wettability, such as the Namib Desert beetle, whose back has hydrophilic/hydrophobic contrast for water harvesting by mist condensation in dry desert environments, and some plant leaves that have hierarchical micro/nanostructures to collect or repel liquid water. In this work, we have provided a method for wettability contrast on alloy steels by both nano-flake or needle patterns and tuning of the surface energy. Steels were provided with hierarchical micro/nanostructures of Fe oxides by fluorination and by a subsequent catalytic reaction of fluorine ions on the steel surfaces in water. A hydrophobic material was deposited on the structured surfaces, rendering superhydrophobicity. Plasma oxidization induces the formation of superhydrophilic surfaces on selective regions surrounded by superhydrophobic surfaces. We show that wettability contrast surfaces align liquid water within patterned hydrophilic regions during the condensation process. Furthermore, this method could have a greater potential to align other liquids or living cells.

Hydrodynamics of writing with ink

Writing with ink involves the supply of liquid from a pen onto a porous hydrophilic solid surface, paper. The resulting linewidth depends on the pen speed and the physicochemical properties of the ink and paper. Here we quantify the dynamics of this process using a combination of experiment and theory. Our experiments are carried out using a minimal pen, a long narrow tube that serves as a reservoir of liquid, which can write on a model of paper, a hydrophilic micropillar array. A minimal theory for the rate of wicking or spreading of the liquid is given by balancing the capillary force that drives the liquid flow and the resistance associated with flow through the porous substrate. This allows us to predict the shape of the front and the width of the line laid out by the pen, with results that are corroborated by our experiments.

Object level HSI-LIDAR data fusion for automated detection of difficult targets

Data fusion from disparate sensors significantly improves automated man-made target detection performance compared to that of just an individual sensor. In particular, it can solve hyperspectral imagery (HSI) detection problems pertaining to low-radiance man-made objects and objects in shadows. We present an algorithm that fuses HSI and LIDAR data for automated detection of man-made objects. LIDAR is used to define a set of potential targets based on physical dimensions, and HSI is then used to discriminate between man-made and natural objects. The discrimination technique is a novel HSI detection concept that uses an HSI detection score localization metric capable of distinguishing between wide-area score distributions inherent to natural objects and highly localized score distributions indicative of man-made targets. A typical man-made localization score was found to be around 0.5 compared to natural background typical localization scores being less than 0.1.

Dependence of Residual Stress of Diamond-Like Carbon Films on Precursor Gases and Process Parameters of RF PACVD

Residual compressive stress of diamond-like carbon (DLC) films was measured by beam deflection method. DLC films were deposited on thin Si wafers using r.f. plasma decomposition of methane and benzene. Negative bias voltage of the cathode was varied from -100 to -800 V and deposition pressure from 3 to 100 mTorr. When using benzene as precursor gas, the residual stress monotonically increases as increasing . (Here, Vb is the negative bias voltage of cathode and P the deposition pressure.) In case of using methane, however, the residual stress has a maximum value at between 70 and 100 V/mTorr1/2. Because of the difference in molecular size between benzene and methane, the mean free path of ions in benzene discharge is 5 times shorter than that in methane discharge. The contrasting behavior of residual stress is discussed in terms of the difference in ion energies at the specimen surface due to the difference in mean free path. On the other hand, total hydrogen concentration decreases as increasing in both cases. This result thus shows that the total hydrogen concentration cannot be a key to understand the behavior of residual stress.

A Method for Independent Measurement of Elastic Modulus and Poisson's Ratio of Diamond-Like Carbon Films

A simple method to measure the elastic modulus and Poisson's ratio of diamond-like carbon (DLC) films deposited on Si wafer was suggested. This method involved etching a side of Si substrate using the DLC film as an etching mask. The edge of DLC overhang free from constraint of Si substrate exhibited periodic sinusoidal shape. By measuring the amplitude and the wavelength of the sinusoidal edge, we can determine the strain of the film required to adhere to the substrate. Combined with independent stress measurement by laser reflection method, this method allows calculation of the biaxial elastic modulus, E/(1 − v), where E is the elastic modulus and v Poisson's ratio of the DLC films. By comparing the biaxial elastic modulus with plane-strain modulus, E/(1 −v2), measured by nano-indentation, we could further determine the elastic modulus and Poisson's ratio, independently. This method was employed to measure the mechanical properties of DLC films deposited by C6H6 r.f. glow discharge at the deposition pressure 1.33 Pa. The elastic modulus, E, increased from 94 to 128 GPa as the negative bias voltage increased from 400 to 550 V. Poisson's ratio was estimated to be about 0.22 in this bias voltage range. For the negative bias voltages less than 400 V, however, the present method resulted in negative Poisson's ratio. The limitation of the present method was discussed.

Cementless total hip replacement using second-generation components: a 12- to 16-year follow-up

We reviewed 123 second-generation uncemented total hip replacements performed on 115 patients by a single surgeon between 1993 and 1994. The acetabular component used in all cases was a fully porous-coated threaded hemispheric titanium shell (T-Tap ST) with a calcium ion stearate-free, isostatically compression-moulded polyethylene liner. The titanium femoral component used was a Taperloc with a reduced distal stem. No patient was lost to follow-up. Complete clinical and radiological follow-up was obtained for all 123 hips at a mean of 14 years (12 to 16). One femoral component was revised after a fracture, and three acetabular components for aseptic loosening. No additional femoral or acetabular components were judged loose by radiological criteria. Mild proximal femoral osteolysis was identified in two hips and minor acetabular osteolysis was present in four. The mean rate of penetration of the femoral head was 0.036 mm/year (0.000 to 0.227). These findings suggest that refinements in component design may be associated with excellent long-term fixation in cementless primary total hip replacement.

Long-lasting hydrophilicity on nanostructured Si-incorporated diamond-like carbon films

We investigated the long-lasting hydrophilic behavior of a Si-incorporated diamond-like carbon (Si-DLC) film by varying the Si fraction in DLC matrix through oxygen and nitrogen plasma surface treatments. The wetting behavior of the water droplets on the pure DLC and Si-DLC with the nitrogen or oxygen plasma treatment revealed that the Si element in the oxygen-plasma-treated Si-DLC films played a major role in maintaining a hydrophilic wetting angle of <10° for 20 days in ambient air. The nanostructured patterns with a roughness of ∼10 nm evolved because of the selective etching of the carbon matrix by the oxygen plasma in the Si-DLC film, where the chemical component of the Si-Ox bond was enriched on the top of the nanopatterns and remained for over 20 days.

Nanoscale patterning of microtextured surfaces to control superhydrophobic robustness

Most naturally existing superhydrophobic surfaces have a dual roughness structure where the entire microtextured area is covered with nanoscale roughness. Despite numerous studies aiming to mimic the biological surfaces, there is a lack of understanding of the role of the nanostructure covering the entire surface. Here we measure and compare the nonwetting behavior of microscopically rough surfaces by changing the coverage of nanoroughness imposed on them. We test the surfaces covered with micropillars, with nanopillars, with partially dual roughness (where micropillar tops are decorated with nanopillars), and with entirely dual roughness and a real lotus leaf surface. It is found that the superhydrophobic robustness of the surface with entirely dual roughness, with respect to the increased liquid pressure caused by the drop evaporation and with respect to the sagging of the liquid meniscus due to increased micropillar spacing, is greatly enhanced compared to that of other surfaces. This is attributed to the nanoroughness on the pillar bases that keeps the bottom surface highly water-repellent. In particular, when a drop sits on the entirely dual surface with a very low micropillar density, the dramatic loss of hydrophobicity is prevented because a novel wetting state is achieved where the drop wets the micropillars while supported by the tips of the basal nanopillars.

Wrinkled, dual-scale structures of diamond-like carbon (DLC) for superhydrophobicity

We present a simple two-step method to fabricate dual-scale superhydrophobic surfaces by using replica molding of poly(dimethylsiloxane) (PDMS) micropillars, followed by deposition of a thin, hard coating layer of a SiO(x)-incorporated diamond-like carbon (DLC). The resulting surface consists of microscale PDMS pillars covered by nanoscale wrinkles that are induced by residual compressive stress of the DLC coating and a difference in elastic moduli between DLC and PDMS without any external stretching or thermal contraction on the PDMS substrate. We show that the surface exhibits superhydrophobic properties with a static contact angle over 160 degrees for micropillar spacing ratios (interpillar gap divided by diameter) less than 4. A transition of the wetting angle to approximately 130 degrees occurs for larger spacing ratios, changing the wetting from a Cassie-Cassie state (C(m)-C(n)) to a Wenzel-Cassie state (W(m)-C(n)), where m and n denote micro- and nanoscale roughness, respectively. The robust superhydrophobicity of the Cassie-Cassie state is attributed to stability of the Cassie state on the nanoscale wrinkle structures of the hydrophobic DLC coating, which is further explained by a simple mathematical theory on wetting states with decoupling of nano- and microscale roughness in dual scale structures.

Biocompatible PEG Grafting on DLC-coated Nitinol Alloy for Vascular Stents

The surfaces of Nitinol (TiNi), a popular metal alloy for arterial stents were thin-coated with diamond-like carbon (DLC) and then grafted with poly(ethylene glycol) (PEG) to increase biocompatibility. The TiNi control, DLC-coated TiNi (TiNi—DLC), and the PEG-grafted TiNi—DLC (TiNi—DLC—PEG) surface characteristics and biocompatibility were evaluated. The hydrophilicity of the TiNi—DLC—PEG significantly increased and the amount of both oxygen and nitrogen on the TiNi—DLC—PEG also increased compared to the TiNi control and TiNi—DLC due to the grafted PEG. The ratio between albumin and fibrinogen was higher on the PEG-grafted surface than the other surfaces when tested with human blood components; the platelet adhesion decreased the most on the TiNi—DLC—PEG surface, indicating improved blood compatibility. For in vivo tests using a rat model, the samples that were implanted for 6 weeks formed fibrous tissue; the tissue layer was much thinner on the PEG-grafted sample than the other two groups. The present results indicate that PEG-grafted TiNi—DLC surface may be effective in enhancing biocompatibility of blood-contacting biomaterials including vascular stents.

Nanoscale ripples on polymers created by a focused ion beam

We show that focused ion beam irradiation results in the creation of peculiar one- and two-dimensional nanoscale features on the surface of polyimide-a common polymer in electronics, large scale structures, and the automobile industry, as well as in biomedical applications. The role of ion beam incident angle, acceleration voltage, and fluence on the morphology of the structural features is systematically investigated, and insights into the mechanisms of formation of these nanoscale features are provided. Moreover, by using the maskless patterning method of the focused ion beam system, we have developed a robust technique for controlled modification of the polymeric surface. The technique, which is analogous to using a gray glass with varying darkness to control the radiation from the sun, but at a much smaller scale, enables the ion intensity and angle to be controlled at each surface point of the polymer, giving rise to structural surface features with desired shape and morphology.

Accuracy of Web-based recording program for in-hospital resuscitation: laboratory study

OBJECTIVE

The purpose of this study was to assess the accuracy of a Web-based resuscitation recording program compared with the handwritten method.

METHODS

A Web site was developed to record in-hospital resuscitation events and a mock resuscitation was recorded using both the Web site and handwritten method by emergency nurses. Accurate recorded events and times were compared between the two methods through the use of a video clip. Paired t tests were used to compare differences in absolute timing error, the number of omitted events out of 11 reference events and total recorded events.

RESULTS

Twenty-one emergency nurses recorded simulated resuscitation events using both the handwritten and Web-based computerised recording system. The mean absolute timing errors were significantly lower using the computerised recording program (37.3 s (SD 17.1) versus 8.3 s (SD 5.3), p<0.001). The mean number of omissions for the computerised program was 1.8 (SD 0.8) compared with 1.4 (SD 1.1) for the handwritten method (p = 0.202). The mean number of total recorded events for the computerised program was 16.5 (SD 3.5) compared with 15.0 (SD 3.8) for the handwritten method (p = 0.063).

CONCLUSIONS

This study suggests that a Web-based recording program decreased timing error while causing no differences in the number of recorded or omitted events in a laboratory setting.

Microtensile strain on the corrosion performance of diamond-like carbon coating

Hydrogenated diamond-like carbon films (a-C:H DLC) were deposited on STS 304 substrates for the fabrication of vascular stents by means of the r.f. plasma-assisted chemical vapor deposition technique. This study provides reliable and quantitative data for the assessment of the effect of strain on the corrosion performance of DLC-coated systems in the simulated body fluid obtained through electrochemical techniques (potentiodynamic polarization test and electrochemical impedance spectroscopy) and surface analysis (scanning electron microscopy). The electrolyte used in this test was 0.89% NaCl solution at pH 7.4 and 37 degrees C. It was found that the corrosion resistance of the plastically deformed DLC coating was insufficient for use as a protective film in a corrosive body environment. This is due to the increase in the delamination area and degradation of the substrate's corrosion properties with increasing tensile deformation.