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Significant advances are being made in the incorporation of enzymes into functional materials, which leverage their inherent substrate specificity, efficient catalytic activity, and sustainable origin. These engineered "dead" materials, however, lack the incredible systems‐level control of enzyme activity that living organisms have evolved over millennia. This gap is now being bridged by the rapidly emerging field of engineered living materials (ELMs), which couples the tools of advanced synthetic biology with modern materials science. In this review, the impressive array of methodologies used to fabricate the extensive library of functional enzyme‐based dead materials is discussed, and the design strategies that facilitate their creation unpacked. The spectacular suite of natural and synthetic genetic and post‐translational control systems for enzymes in living organisms is then described. Finally, key recent examples of ELMs that utilize enzyme activity are reviewed, highlighting the central role of the living component in providing responsivity and adaptability to this new class of materials. [ABSTRACT FROM AUTHOR]

The synthesis of a porous shape‐changing interpenetrating network (IPN) bioink for the fabrication of large‐scale (cm) reversibly thermosensitive structures is described. The poly(N‐isopropylacrylamide) (PNIPAm) IPN is generated in situ within an ionically crosslinked alginate hydrogel at room temperature and under aerobic conditions using a horseradish peroxidase (HRP)/glucose oxidase (GOx) bienzymatic initiation system. Mechanical testing assessment of the IPN hydrogels confirm mechanical reinforcement via covalent single network interdigitation. Furthermore, the thermosensitive bioink can be used to print biohybrid reactors containing genetically engineered phosphotriesterase‐expressing E. coli capable of hydrolyzing toxic organophosphorus compounds. Herein, increasing the bioink pore size using the contractile‐thermosensitive response of the IPN improves the temperature‐dependent theoretical mass‐transfer‐limited enzyme catalyzed reaction rate, providing a plausible route to externally regulated enzymatic catalysis within bioprinted structures. [ABSTRACT FROM AUTHOR]

Provides information on a study that examined laser-induced stress during high-power laser ablation of solids. Methodology of the study; Results and discussion on the study; Conclusion.

Presents a study that demonstrated the detection of laser-induced melt at the surface of a solid in real time using a photothermal deflection technique. Details of the experiment; Theoretical analysis; Results and discussion.

Photothermal deflection (PTD) techniques have been used to monitor various laser-heating processes, including melt, vaporization, and ablation of solids. To interpret the complex signal response resulting from transient phase changes at a surface, the temporal profile of the PTD signal response must be considered. In doing so, the case of the linear heating of a target without phase change is first studied here. Numerical and experimental work is presented to show the effect on the shape, magnitude, and phase of a PTD signal due to changes in (1) the thermophysical properties of the target material and deflecting medium, (2) the dimensions and boundary conditions of the target, (3) the distance of the probe beam from the surface of the target, and (4) the modulation frequency of the heating source. Copper and lead target materials heated in air are used in the experimental work. The PTD signals show qualitative agreement with the temperature gradient normal to the surface calculated using. a numerical finite-difference two-dimensional thermal-diffusion model. The results also show that an unusual phenomenon occurs when heating with a laser or other finite-sized heating source. When the thermal diffusivity of the target and deflecting medium are different and the probe beam is close to the surface, a local maximum is observed in the time-response profile of the PTD signal during the heating cycle. The maximum occurs as a result of asymmetric changes in the temperature field over time. The shape of the PTD signal, therefore, can provide information about the laser-heating process at a surface in real time. [ABSTRACT FROM AUTHOR]

The EUROfusion Consortium is setting up – as part of the EU Fusion Roadmap – the framework for the implementation of the (pre)conceptual design phase of the DEMO reactor. Configuration management needs have been identified as one of the key elements of this framework and is the topic of this paper, in particular the configuration of the CAD design data. The desire is to keep the definition and layout of the corresponding systems “light weight” and relatively easy to manage, whilst simultaneously providing a level of detail in the definition of the design configuration that is fit for the purpose of a conceptual design. This paper aims to describe the steps followed during the definition of the configuration management system of the DEMO design data in terms of (i) the identification of the appropriate product data management system, (ii) the description of the philosophy of the configuration management of the design data, and (iii) the introduction of the most important enabling processes. [ABSTRACT FROM AUTHOR]

Abstract: In the ITER equatorial ports containing ICRH antennas, parasitic electrical resonances can be excited in the nominal 20mm clearance gap between the port walls and the plug contained within it. RF calculations have established that these resonances can be effectively mitigated by a series of suitably located electrically conducting contacts between the port and plug. These contacts must allow installation and removal of the antenna but must also make reliable electrical contact during antenna operation. In addition, the contacts must be compliant enough to survive deflection of the port during seismic and disruption events without transmitting large forces to the vacuum vessel. The distance to be spanned is subject to significant uncertainty, due to the large manufacturing tolerances of the surrounding components, and this also must be considered during the design process. This paper outlines progress made in the design of the grounding system, as well as detailing a number of concepts which have been investigated and abandoned, leading up to the current reference design. The current reference design is a simple and robust mechanical solution consisting of sprung Copper-plated Inconel flaps which use part of the range of the shimming system included in the antenna design as the actuation mechanism. This paper also details practical testing of a number of aspects of the design, including building and testing a prototype to validate mechanical and thermal analyses. [Copyright &y& Elsevier]

Abstract: In this report, SrTi(1−x)Fe(x)O(3−δ) photocatalyst powder was synthesized by a high temperature solid state reaction method. The morphology, crystalline structures of obtained samples, was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM), respectively. The electronic properties and local structure of the perovskite STFx (0≤x≤1) systems have been probed by extended X-ray absorption fine structure (EXAFS) spectroscopy. The effects of iron doping level x (x=0–1) on the crystal structure and chemical state of the STFx have been investigated by X-ray photoelectron spectroscopy and the valence band edges for electronic band gaps were obtained for STFx by ultraviolet photoelectron spectroscopy (UPS). A single cubic perovskite phase of STFx oxide was successfully obtained at 1200°C for 24h by the solid state reaction method. The XPS results showed that the iron present in the STFx perovskite structure is composed of a mixture of Fe3+ and Fe4+ (SrTi(1−x)[Fe3+, Fe4+](x)O(3−δ)). When the content x of iron doping was increased, the amount of Fe3+ and Fe4+ increased significantly and the oxygen lattice decreased on the surface of STFx oxide. The UPS data has confirmed that with more substitution of iron, the position of the valence band decreased. [Copyright &y& Elsevier]

Abstract: Details are presented for the formulation, fabrication, and mechanical characterization of mesoscopic freestanding polydimethylsiloxane (PDMS) elastomer membranes, 10.0 μm thick and 5.0 mm in diameter, used to probe the rheology of a living epithelial sheet. In what is described as a composite diaphragm inflation (CDI) experiment, freestanding PDMS membranes are utilized as substrates for the culture of a sheet of epithelial cells. Together, the cell layer and the PDMS elastomer form a composite diaphragm (CD) that is suitable for mechanical testing in an axisymmetric membrane inflation experiment. In order to distinguish the rheological behavior of the epithelial sheet from the mechanical response of the elastomer using inflation test data, freestanding PDMS membranes should exhibit a highly compliant yet mechanically invariant finite load-deformation response when subjected to multiple inflation cycles following intermittent periods of cell culture. Given these considerations, we describe a method for preparing freestanding PDMS elastomer membrane specimens that are optically transparent, tensed, and wrinkle-free. Surface modifications intended to facilitate cell culture, namely water vapor plasma and ultraviolet light treatments, were shown to dramatically stiffen the mechanical response of the membranes, rendering them unusable as CD substrates. In this study, only PDMS membranes with physiosorbed collagen demonstrated the mechanical compliance, fatigue resistance, and environmental stability necessary for reliable use in CDI experiments. [Copyright &y& Elsevier]

One of the most pervasive problems afflicting people throughout the world is inadequate access to clean water and sanitation. Problems with water are expected to grow worse in the coming decades, with water scarcity occurring globally, even in regions currently considered water-rich. Addressing these problems calls out for a tremendous amount of research to be conducted to identify robust new methods of purifying water at lower cost and with less energy, while at the same time minimizing the use of chemicals and impact on the environment. Here we highlight some of the science and technology being developed to improve the disinfection and decontamination of water, as well as efforts to increase water supplies through the safe re-use of wastewater and efficient desalination of sea and brackish water. [ABSTRACT FROM AUTHOR]

Details are given for the design, calibration, and operation of an apparatus for measuring the finite load-deformation behavior of a sheet of living epithelial cells cultured on a mesoscopic freestanding elastomer membrane, 10 μm thick and 5 mm in diameter. Although similar in concept to bulge tests used to investigate the mechanical properties of micromachined thin films, cell-elastomer composite diaphragm inflation tests pose a unique set of experimental challenges. Composite diaphragm (CD) specimens are extremely compliant (E<50 kPa), experience large displacements when subject to small inflation pressures (∼100 Pa), and must be continuously immersed in a bath of liquid culture medium during the acquisition of load-deformation measurements. Given these considerations, we have constructed an inflation apparatus consisting of an air-piston-cylinder pump integrated with a modular specimen mounting fixture that constitutes a horizontally semi-infinite reservoir of liquid culture medium. In a deformation-controlled inflation test, pressurized air is used to inflate a CD specimen into the liquid reservoir with minimum disturbance of the liquid-air interface. Piston displacements and absolute pump chamber air pressures are utilized as feedback to cycle the displaced (or inflated) CD volume V in a 0.05 Hz triangular or sinusoidal wave form (VMIN=0 μl, VMAX<=40 μl) while simultaneously recording the inflation pressure acting at the fixed boundary of the specimen, p(r=a). Using a carefully prescribed six-cycle inflation test protocol, the apparatus is shown to be capable of measuring the [V,p(r=a)] inflation response of a cell-elastomer CD with random uncertainties estimated at ±0.45 μl and ±2.5 Pa, respectively. [ABSTRACT FROM AUTHOR]

The dependence of the contact potential difference (CPD) reading on the ac driving amplitude in scanning Kelvin probe microscope (SKPM) hinders researchers from quantifying true material properties. We show theoretically and demonstrate experimentally that an ac driving amplitude dependence in the SKPM measurement can come from a systematic error, and it is common for all tip sample systems as long as there is a nonzero tracking error in the feedback control loop of the instrument. We further propose a methodology to detect and to correct the ac driving amplitude dependent systematic error in SKPM measurements. The true contact potential difference can be found by applying a linear regression to the measured CPD versus one over ac driving amplitude data. Two scenarios are studied: (a) when the surface being scanned by SKPM is not semiconducting and there is an ac driving amplitude dependent systematic error; (b) when a semiconductor surface is probed and asymmetric band bending occurs when the systematic error is present. Experiments are conducted using a commercial SKPM and CPD measurement results of two systems: platinum-iridium/gap/gold and platinum-iridium/gap/thermal oxide/silicon are discussed. [ABSTRACT FROM AUTHOR]

Integrating multiple analytical processes into microfluidic devices is an important research area required for a variety of microchip-based analyses. A microfluidic system is described that achieves preparative separations by intelligent fraction collection of attomole quantities of sample. The device consists of a main microfluidic channel used to perform electrophoresis, which is interconnected at 90° to two vertically displaced channels via a nanocapillary array membrane. The membrane interconnect contains nanometer-diameter pores that provide fluidic communication between the channels. Sample injection and analyte collection are controlled by application of an electrical bias between the microfluidic channels across the nanocapillary array. After the separation, the automated transfer of the FTTC-labeled Arg, Gln, and Gly bands occurs; a fluorescence detector located at the separation! collection channel interconnect is used to generate a triggering signal that initiates suitable voltages to allow near-quantitative transfer of analyte from the separation channel to the second fluidic layer. The ability to achieve such sample manipulations from mass-limited samples enables a variety of postseparation processing events. [ABSTRACT FROM AUTHOR]

Describes a homologous pair of human and mouse Krüppel-associated box-zinc finger (ZNF) gene clusters. Assumption that duplication and loss of ancestral cluster members occurred differently in the primate and rodent lineages after divergence; Existence of phylogenetic relationships between human and mouse genes; Expansion of Krüppel-type ZNF genes to significant numbers in mammals.

Presents a study that developed a design for a high-temperature, high voltage (HV) insulator. Background on the use of standard HV vacuum insulating ceramic materials as HV vacuum insulators; Analysis of the thermal behavior of the insulators; Results and implications.

High resolution and precise surface morphology is a primary goal of laser-assisted chemical etching (LACE) for microfabrication. However, the interaction of the laser light with the process gas can change the intensity incident to the target surface due to self-induced, thermally developed inhomogeneities within the gas. The exponential relationship between LACE rates and surface temperature means that very small changes in intensity, and thus surface temperature distribution, has a very large effect on the etch profile. This paper models both the inhomogeneous light–process gas interaction and the etching to predict the regimes in time and absorption path length where this effect needs to be considered. Numerical calculations of LACE microfabrication of borosilicate glass in a sulfur hexafluoride process gas with a 10.6 μm wavelength laser beam are given that show how the surface morphology of the glass wafer is changed by the inhomogeneous interaction. [Copyright &y& Elsevier]

Respiratory syncytial virus (RSV) causes severe infections in infants, immunocompromised or elderly individuals resulting in annual epidemics of respiratory disease. Currently, limited clinical surveillance and the lack of predictable seasonal dynamics limit the public health response. Wastewater-based epidemiology (WBE) has recently been used globally as a key metric in determining prevalence of severe acute respiratory syndrome coronavirus 2 in the community, but its application to other respiratory viruses is limited. In this study, we present an integrated genomic WBE approach, applying reverse-transcription quantitative polymerase chain reaction and partial G-gene sequencing to track RSV levels and variants in the community. We report increasing detection of RSV in wastewater concomitant with increasing numbers of positive clinical cases. Analysis of wastewater-derived RSV sequences permitted identification of distinct circulating lineages within and between seasons. Altogether, our genomic WBE platform has the potential to complement ongoing global surveillance and aid the management of RSV by informing the timely deployment of pharmaceutical and nonpharmaceutical interventions. [ABSTRACT FROM AUTHOR]

“Flash heating” that transiently generates high temperatures above 1000 °C has great potential in synthesizing new materials with unprecedently properties. Up to now, the realization of “flash heating” still relies on the external power, which requires sophisticated setups for vast energy input. In this study, a mechanochemically triggered, self‐powered flash heating approach is proposed by harnessing the enthalpy from chemical reactions themselves. Through a model reaction between Mg3N2/carbon and P2O5, it is demonstrated that this self‐powered flash heating is controllable and compatible with conventional devices. Benefit from the self‐powered flash heating, the resulting product has a nanoporous structure with a uniform distribution of phosphorus (P) nanoparticles in carbon (C) nanobowls with strong P─‐C bonds. Consequently, the P/C composite demonstrates remarkable energy storage performance in lithium‐ion batteries, including high capacity (1417 mAh g−1 at 0.2 A g−1), robust cyclic stability (935 mAh g−1 at 2 A g−1 after 800 cycles, 91.6% retention), high‐rate capability (739 mAh g−1 at 20 A g−1), high loading performance (3.6 mAh cm−2 after 100 cycles), and full cell cyclic stability (90% retention after 100 cycles). This work broadens the flash heating concept and can potentially find application in various fields. [ABSTRACT FROM AUTHOR]

Presents a comparison of laser ablation mass removal and incident power density during solid sampling for inductively coupled plasma atomic emission spectroscopy. Influence of the quantity of material ablated on the sensitivity of chemical analysis; Dependence of the mass removal rate on laser power density.

The article focuses on water desalination using a nanochannel based desalinator powered by a battery. This method, introduced by Jongyoon Han and fellow researchers from the Massachusetts Institute of Technology and Pohang University of Science and Technology, has the ability to divide a stream of sea water into desalted and saltier streams and remove cells, viruses and microorganisms. The fact that this type of water desalination technique uses the lowest energy is also mentioned.

Examines laser-induced stresses resulting from high-power laser material interactions. Demonstration of the difference of stress power from stress in the far field; Relation of the change in P to the general energy balance; Change in the rate of laser energy coupling into the medium.

Abstract: The correlation of gene and protein expression changes in biological systems has been hampered by the need for separate sample handling and analysis platforms for nucleic acids and proteins. In contrast to the simple, rapid, and flexible workflow of quantitative PCR (qPCR) methods, which enable characterization of several classes of nucleic acid biomarkers (i.e. DNA, mRNA, and microRNAs), protein analysis methods such as Western blotting are cumbersome, laborious, and much less quantitative. However, TaqMan® Protein Assays, which use the proximity ligation assay (PLA™) technology, now expand the range of qPCR applications to include the direct detection of proteins through the amplification of a surrogate DNA template after antibody binding. Here we describe an integrated qPCR approach for measuring relative changes in gene and protein expression from the same starting sample and on a single analytical platform that pairs TaqMan® Gene Expression (GEx) Assays with TaqMan® Protein Assays. We have monitored the changes in mRNA, microRNA, and protein expression of relevant biomarkers in the pluripotent human embryonal carcinoma cell line, NTERA2, upon differentiation to neuronal cells. In addition, TaqMan® Protein Assays have been used to monitor protein expression in induced pluripotent stem cells (iPSC) that have been reprogrammed from human somatic cells. The data presented establishes a general paradigm utilizing real-time PCR instruments and reagents for studying the relationship between the stem cell transcriptome and proteome. [Copyright &y& Elsevier]

Abstract: An electrostatically driven valve-less peristaltic micropump for gas chromatography has been developed. A stepwise chamber was first fabricated using a three-dimensional (3D) fabrication technique known as detachment lithography; the stepwise design was intended to decrease the dead volume of the device and the operation voltage by inducing zipping action. The pump itself was fabricated with a silicon substrate and a polyimide (PI) diaphragm and operated by four electrodes with a 4-phase sequencing actuation. The pump was operated in a range starting from a voltage of 60V and frequency of 4Hz with a flow rate of 18.2μl/min, up to a voltage of 90V at a frequency of 6Hz with a maximum flow rate of 33.1μl/min. The results showed that the minimum operating voltage of the stepwise chamber was approximately 30% lower than that of a vertical chamber with the same depth, and the power consumption per unit flow rate was also decreased by about 10%. [Copyright &y& Elsevier]

Abstract: Microwave-assisted chemical vapor deposition has been used to generate high quality, high-k dielectric films on silicon at high deposition rates with film thicknesses varying from 50 nm to 110 μm using inexpensive equipment. Characterization of the post deposition products was performed by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Auger electron spectroscopy and Raman spectroscopy. Film growth was determined to occur via rapid formation and accumulation of tantalum oxide clusters from tantalum (v) ethoxide (Ta(OC2H5)5) vapor on the deposition surface. [Copyright &y& Elsevier]

This article demonstrates how to prepare microfabricated columns (microcolumns) for organophosphonate and organosulfur compound separation that rival the performance of commercial capillary columns. Approximately 16 500 theoretical plates were generated with a 3 m long OV-5-coated microcolumn with a 0.25 μm phase thickness using helium as the carrier gas at 20 cm/s. Key to the advance was the development of deactivation procedures appropriate for silicon microcolumns with Pyrex tops. Active sites in a silicon-Pyrex microcolumn cause peak tailing and unwanted adsorption. Experimentally, we found that organosilicon hydride deactivation lowers adsorption activity in microcolumns more than silazane and silane treatments. But without further treatment, the phosphonate peaks continue to tail after the coating process. We found that heat treatment with pinacolyl methylphosphonic acid (PMP) eliminated the phosphonate peak tailing. In contrast, conventional resilylation employing N, O-bis(trimethylsilyl)acetamide, hexamethyldisilazane, and 1-(trimethylsilyl)imidazole does not eliminate peak tailing. Column activity tests show that the PMP treatment also improves the peaks for 2,6- dimethyl aniline, 1-octanol, and 1-decanol implying a decrease in the column's hydrogen bonding sites with the PMP treatment. FT-IR analysis shows that exposure to PMP forms a bond to the stationary phase that deactivates the active sites responsible for organophosphonate peak tailing. [ABSTRACT FROM AUTHOR]

An experimental technique is presented to measure reflectance at high sample temperature with respect to room temperature in the infrared using Fourier transform infrared fitted with a reflectometer. Sample temperature artifacts are accounted for by sequential measurements taken with the lamp source on and with the lamp source off. The sequential measurements are shown mathematically to correct for the modulation of sample and detector thermal emissions. Further, the technique is applied to a polyimide (PMDA-ODA) film on a layer of gold deposited on a thermally oxidized Si wafer. It is shown that the optical properties (index of refraction and extinction coefficient) remain relatively constant with temperature (from room temperature to 380 °C) in the 4000–6000 cm-1 spectral region. The significant changes that occur with temperature are the change in thickness of the film and also the spectral properties in the 2000–4000 cm-1 region. Also, by using a Lorentz oscillator model, it is shown that this method is able to discern that spectral features corresponding to the OH stretching bands at 3630 and 3470 cm-1 show significant variation with increasing temperature. [ABSTRACT FROM AUTHOR]

The application of parallel computational methods to the modeling of laser light interactions with a thermally self-induced inhomogeneous medium is described. In these processes, laser light dynamically changes the local refractive index through heat absorption, which in-turn alters the beam profile. The mathematical model couples the 3-D heat diffusion and paraxial wave equations resulting in a system of non-linear equations. An explicit, finite-difference method (FDM) for solving the heat diffusion equation is coupled with an implicit FDM solution of the paraxial wave equation. The reasons for choosing these schemes are presented, along with a mixed-mode parallelization method in which OpenMP is used for the explicit solver, and MPI for the implicit solver. Finally, convergence, stability, accuracy and code performance is presented. [Copyright &y& Elsevier]

One of the objectives of Curriculum 2000 is to increase the breadth of the curriculum followed by 16–19 year olds. In this paper A level and AS uptake for the years 2001 and 2002 are considered. There was considerable diversity in the uptake of A levels, with nearly 21,000 different combinations of A levels being present in 2002 A level results. Although it is true that biology, chemistry and mathematics is the most common combination of A levels, only 2.2 per cent of candidates took this precise combination. There has been a decline in the percentage of candidates taking three science A levels. In 2002, when only A levels are considered, 35 per cent of candidates could be described as specialists, falling to 21 per cent when AS results are included. AS qualifications appear to have been successful in broadening the curriculum. [ABSTRACT FROM AUTHOR]

Crossed microfluidic channels are fabricated in poly(dimethylsiloxane) (PDMS) monoliths in planes above and below a 6–10 μm thick nanoporous polycarbonate nuclear track-etched (PCTE) membrane to form a three-dimensional hybrid microfluidic and nanofluidic system. The use of commercially available nanoporous membranes allows quick and economical fabrication of nanochannel architectures to provide fluidic communication between microfluidic layers. More importantly, these nanoporous membranes add functionality to the system as gateable interconnects. These nanofluidic interconnects enable control of net fluid flow based on a number of different physical characteristics of the sample stream, the microfluidic channels and the nanochannels, leading to hybrid fluidic architectures of considerable versatility. Because the nanofluidic membrane can have surfaces with excess charge of either polarity, the net flow direction inside the microdevices is principally controlled by two factors: the magnitude of the electrical and physical flow impedance of the nanoporous membrane relative to that of the microchannels and the surface chemical functionalities which determine the polarity of the excess charge in the nanochannels. The nanochannel impedance may be manipulated by varying membrane pore size. Flow control is investigated by monitoring electrokinetic transport of both neutral and negatively charged fluorescent probes, by means of laser-induced fluorescence and fluorescence microscopy, while varying solution and nanochannel properties. When the pore size of the PCTE membrane is small, the impedance is large and the polarity of the nanochannel surface charge determines the overall direction of the net electroosmotic flow. When the combined impedance of the upper and lower microchannels exceeds 30 times the impedance of the nanochannel membrane, the direction of the flow is based on the negative surface charge of the PDMS microchannels. [Copyright &y& Elsevier]

Free electrons in metal films absorb laser light and then transfer the absorbed photon energy to the metal lattice through electron-lattice collisions, which can result in lattice heating, thermal stress, melting, and evaporation. This work studies nanosecond laser heating of gold films both theoretically and experimentally. A two-step radiation heating model is utilized to characterize transient temperatures of the electron system and the lattice system. Results show that in the nanosecond regime electrons and the lattice are in thermal equilibrium and the classical Fourier heat conduction model is applicable. Microstructures and morphology of films before and after laser pulse heating are characterized with optical and electron microscopes. Two different types of thermal and mechanical responses of gold films are observed. For thin films, thermal stress plays a significant role in laser-film interactions, which can lead to structure changes of films at a temperature much lower than the melting point. For thick films, structure changes are due mainly to melting. [ABSTRACT FROM PUBLISHER]

The BioMedical Admissions Test (BMAT) has been used to select students for healthcare courses for 15 years. Recently, the candidature has included an increasing number of test takers who did not complete their schooling in the UK. In line with responsibilities to promote widening participation, a revision of the Section 2 Scientific Knowledge and Applications specification was conducted, to support the preparation of candidates from under-represented groups and international candidates. The process was guided by validity frameworks established in language testing research, with a particular focus on consequential validity and washback. Candidate surveys are reported to illustrate the focus on test preparation. Issues identified in the review demonstrate the impact of international test-takers' linguistic backgrounds and differences in teaching approaches, and possible interactions between these are discussed. It is recommended that admissions test developers make use of holistic frameworks of validity from other contexts to systematically interrogate a wide range of validity evidence relating to their tests. [ABSTRACT FROM AUTHOR]

Focused-ion beam (FIB) milling provides rapid fabrication of individual cylindrical submicrometer channels with reproducible dimensions (±5% diameters) through 8‐μm thick poly(methylmethacrylate) (PMMA) films. PMMA films are spincast on sacrificial Si carriers and sputter-coated with Au before the 30‐kV gallium FIB milling process. By adding a trace amount of poly(ethyleneoxide) and poly(dimethylsiloxane) to the PMMA solution before casting, the films can be released for subsequent mounting in microfluidic devices to create hybrid microfluidic-nanofluidic multilevel architectures. In situ FIB sectioning demonstrates the smooth cylindrical surface within the pore. Placing a milled film in contact with an aqueous fluorescein solution fills the channel by capillary action, as verified by confocal fluorescence microscopy. Confocal fluorescence of dyed films reveals that the pores span the thickness of the PMMA film. Small arrays of channels with a defined number and density and arbitrary in-plane spatial arrangement are fabricated with this process, allowing a unique testbed for high aspect ratio nanofluidic devices. [ABSTRACT FROM AUTHOR]

Using sum-frequency vibrational spectroscopy, we found that water structure at nanoporous silica/water interfaces depended on the nanoporous film structure. For a periodic, self-assembled nanoporous film with monosized 2 nm pores occupying 20% of the top surface area, the surface vibrational spectrum was dominated by water in contact with silica, bare or covered by silane, at the top surface. It resembled the spectral characteristic of the hydrophilic water/silica or the hydrophobic water/silane interface. For a fractal nanoporous film with pores ranging from 5 to 50 nm in size occupying 90% of the top surface, the spectrum for a trimethyl silane-coated superhydrophobic porous film resembled largely that of a water/air interface. Only when the silane was completely removed would the spectrum revert to that characteristic of a hydrophilic water/silica interface. The surface charging behaviors of the bare nanoporous films in water with different pH were monitored by spectroscopic measurements and atomic force microscopy force measurements. The point of zero charge for the periodic porous film is around pH 2, similar to that of the flat silica surface. The point of zero charge could only be determined to be pH<6 for the fractal porous film because the thin fractal solid network limited the amount of surface charge and therefore, the accuracy of the measurements. [ABSTRACT FROM AUTHOR]

The electrical conduction behavior of undoped ultrananocrystalline diamond (UNCD) and its dependence on deposition temperature and chemical structure are presented. UNCD films were grown using a microwave plasma-enhanced chemical vapor deposition technique at deposition temperatures of 400 °C and 800 °C. The chemical structure of the UNCD films is characterized with several tools including: Elastic recoil detection analysis, Fourier transform infrared spectroscopy, electron energy loss spectroscopy, Raman spectroscopy, and environmental scanning electron microscope. The results show a higher content of sp2-bonded carbon for the 800 °C deposition samples (∼65%) in comparison with the 400 °C samples (∼38%). In both kinds of films, the hydrocarbon bonds have the saturated sp3 structures, while there is lower hydrogen content in the 800 °C samples (∼8%) than in the 400 °C samples (∼10%). For conduction properties, experiments are conducted using a probe station and conductive-atomic force microscopy. Experimental data show that the samples deposited at 800 °C are several orders of magnitude more conductive than the 400 °C samples. The conduction occurs primarily along the grain boundary for both types of samples. The conductivity of both types of films also shows field dependent nonlinear behavior. Both the Poole–Frenkel models and single and overlapping Coulombic potential models show that the conduction is directly correlated with the sp2 bond carbon density, and the role of the hydrocarbon bonds in the conduction path is formed by the network of the sp2 bonded carbon. [ABSTRACT FROM AUTHOR]

This paper presents the combined use of mathematical modeling and Auger depth profiling to study and quantify the oxidation of Ta films over a wide range of temperatures. The thermal oxidation of tantalum films (∼700 nm) is studied using direct measurements of species concentration by means of Auger depth profiling. The oxidation temperature range of this study extends from 300 to 700 °C and the oxidation period varies from 5 s to 12.5 h. The Auger depth profiles revealed that the metallic film oxidizes to first form low valence oxides of Ta that progressively convert to tantalum pentoxide with increasing temperature and time. A first-order reaction diffusion model is used to quantify the diffusion of oxygen through a film that is evolving in composition. The Auger depth profiling and reaction-diffusion model are used to estimate the actual diffusivity values for oxygen in the evolving Ta/Ta-oxide thin-film matrix, rather than more conventional techniques that estimate either the initial diffusion of oxygen through a semi-infinite metal or give a depth- and time-integrated value for the diffusivity. A comparison between the actual diffusivity values estimated in this work and the depth- and time-integrated version using the same model revealed that the integrated values are higher than the actual diffusion values by greater than 300% for the temperature range tested. Moreover, these depth- and time-integrated values for diffusivity values match over the applicable temperature ranges the diffusivity values given in the literature, which are essentially integrated average values for Ta/Ta oxide matrix. Furthermore, using the Auger depth profiles, the oxide growth rates are quantified as a function of temperature and compared with available literature. The growth rate of the oxide that is observed to be logarithmic at 300 °C is seen to have a parabolic growth at 500 °C and then a multistep growth behavior (a combination of parabolic and linear growth) at 700 °C. These growth rates and the transition from one growth type to another strongly correlate to the change in surface and film morphology and also the transition from amorphous to crystalline Ta2O5. [ABSTRACT FROM AUTHOR]

Ceramic components will be used for electrical insulation and optical transparency on the heating and diagnostic systems of fusion reactors. As these form the boundary for the radioactive confinement, a defined procedure is required to demonstrate structural integrity. The established design codes are incompatible with ceramic materials for various reasons, predominantly the brittle nature of ceramics. CCFE and others have started to develop an in-house design code for the use of brittle materials in pressure vessels, this paper discusses the rationale behind the rules. The difficulty of reconciling the statistical nature of failure in ceramics with the deterministic nature in codes is addressed and it is suggested that the only way to achieve this is by a proof testing approach. The inherent weakness of the proof testing methodology, quantifying the strength loss during the qualification test is discussed. Further work is required to determine the validity of the rules experimentally. [ABSTRACT FROM AUTHOR]

The Ion Cyclotron Heating and Current Drive (ICH&CD) system will reside in ITER equatorial port plugs 13 and 15. Shutdown dose rates (SDDR) within the port interspace are required to be less than 100 μSv/h at 10 6 s cooling. A significant contribution to the SDDR results from neutrons streaming down gaps around the port frame, and the mitigation of this streaming is the main subject of these analyses. An updated MCNP model of the antenna was created and integrated into an ITER reference model. Shielding plates were defined in the port gaps, and scoping studies conducted to assess their effectiveness in several configurations, based on which a front dog-leg arrangement was selected for high resolution 3-D activation analysis using MCR2S. It was concluded that the selected configuration reduced the SDDR from ∼500 μSv/h to 220 μSv/h but were still in excess of dose rate requirements. Approximately 30% of this was due to cross-talk from neighbouring ports. In addition, increased dose rates were observed in the port interspace along the lines of sight of the removable vacuum transmission lines. Design optimisation is continuing, however an integrated approach is needed with regard to ITER port plug design and the shielding of surrounding systems. [ABSTRACT FROM AUTHOR]

Embedded RF contacts are integrated within the ITER ICRH launcher to allow assembling, sliding and to lower the thermo-mechanical stress. They have to withstand a peak RF current up to 2.5 kA at 55 MHz in steady-state conditions, in the vacuum environment of the machine. The contacts have to sustain a temperature up to 250 °C during several days in baking operations and have to be reliable during the whole life of the launcher without degradation. The RF contacts are critical components for the launcher performance and intensive R&D is therefore required, since no RF contacts have so far been qualified at these specifications. In order to test and validate the anticipated RF contacts in operational conditions, CEA has prepared a test platform consisting of a steady-state vacuum pumped RF resonator. In collaboration with ITER Organization and the CYCLE consortium (CYclotron CLuster for Europe), an R&D program has been conducted to develop RF contacts that meet the ITER ICRH launcher specifications. A design proposed by CYCLE consortium, using brazed lamellas supported by a spring to improve thermal exchange efficiency while guaranteeing high contact force, was tested successfully in the T-resonator up to 1.7 kA during 1200 s, but failed for larger current values due to a degradation of the contacts. Details concerning the manufacturing of the brazed contacts on its titanium holder, the RF tests results performed on the resonator and the non-destructive tests analysis of the contacts are given in this paper. [ABSTRACT FROM AUTHOR]

Abstract: Ionic transport through synthetic nanoporous membranes has received great attention in applications related to biosensing, fuel cell, and desalination. Past work has demonstrated that charge selectivity can be achieved by applying a potential across a metallized conductive membrane. However, challenges arise for improving charge selectivity as a result of irreversibility of the system from the anion adsorption at the membrane surface. This study demonstrates how charge selectivity can be improved with the presence of a well grown self-assembled monolayer (SAM), which can aid in applications that use chemical separation processes based on the surface charge of the nanopore. In this work, the transport and selectivity properties of gold-coated conductive nano-capillary-array-membranes (NCAMs) are studied using charged species methyl viologen paraquat, (MV2+) and napathalenedisulfonate disodium salt (NDS2−). The selectivity coefficients for MV2+ and NDS2− increased with the functionalization of undecanethiol on the gold-coated NCAM surface. With the presence of a SAM, the selectivity coefficients increased by 44% for MV2+ and 200% for NDS2−. The influence of ionic transport from the diffuse layer potential at the walls and surface of the nanopore is also discussed. [Copyright &y& Elsevier]

To treat wastewater containing paraquat, the interaction of the herbicide with unmodified and modified (i.e., chemically treated) proprietary silicas is explored using liquid chromatography-mass spectrometry and ultraviolet-visible spectrometry. Strong adsorption and rapid exchange kinetics (i.e., more than 80% within 30 s) of the contaminant onto both unmodified and modified silica surfaces indicate that paraquat adsorption is inherent to the unmodified silica. Although activated carbon sequesters paraquat more effectively than silica at long times (i.e., after 2 h), considering both constant mass and constant area approaches in loading the adsorbents, the best performance in the short-term (i.e., at least up to 150 s) interaction was achieved by using unmodified silicas. Comparison of data fitting to a competitive binding model with or without consideration of homogeneous solid diffusion indicates that, at least for times relevant to water-treatment applications, the competitive binding model is an appropriate mathematical tool to explain experimental adsorption data. Addition of is also attempted to initiate paraquat decomposition; however, silica is not an effective catalyst for peroxide decomposition paraquat. [ABSTRACT FROM AUTHOR]

Abstract: Interactions of supercritical water (SCW) with several carbon (including polycrystalline graphite, highly ordered pyrolytic graphite (HOPG), pyrolytic carbon, and diamond) and selected ceramic materials under oxic or anoxic conditions are investigated. Wettability and surface/material properties of samples, before and after the SCW exposure, are characterized with sessile drop contact angle measurement, profilometry, XPS, XRD, and ToF-SIMS. All tested ceramic materials became more hydrophilic during the SCW exposure, mainly due to hydrolysis reactions. Carbon samples exposed to oxic SCW became more hydrophilic as a result of surface oxidation. Carbon materials, except HOPG and diamond, became more hydrophobic when exposed to anoxic SCW because of degradation of hydrophilic oxygen functionalities. HOPG and diamond became more hydrophilic after anoxic SCW exposure mainly due to the removal of hydrophobic hydrocarbon contaminants. Hydrophobicity of different carbon samples exposed to SCW are explained based on the abundance of surface hydrophilic sites (i.e., oxygen functionalities, reactive carbon dangling bonds or defects), hydrocarbon impurities, and surface roughness. [Copyright &y& Elsevier]

Hydrogen sulphide is found in raw fuels such as natural gas and coal/biomass-derived syngas. It is poisonous to catalysts and corrosive to metals and therefore needs to be removed. This is often achieved using metal oxides as reactive adsorbents, but metal oxides perform poorly when subjected to repeated cycles of sulphidation and re-oxidation as a result of complex structural and chemical changes. Here, we show that Zn-Ti-O-based adsorbents with nanofibrous morphology can sustain their initial reactivity and sulphur removal capacity over multiple regeneration cycles. These nanostructured sorbents offer rapid reaction rates that overcome the gas-transport limitations of conventional pellet-based sorbents and allow all of the material to be used efficiently. Regeneration can be carried out at the same temperature as the sulphidation step because of the higher reactivity, which prevents sorbent deterioration and reduces energy use. The efficient regeneration of the adsorbent is also aided by structural features such as the growth of hierarchical nanostructures and preferential stabilization of a wurtzite phase in the sulphidation product. [ABSTRACT FROM AUTHOR]

We report on the fabrication and characterization of electrostatic gas micro-pumps integrated with polyimide check valves. Touch-mode capacitance actuation, enabled by a fixed silicon electrode and a metal/polyimide diaphragm, creates the suction and push-out of the ambient gas; the gas flow is rectified by the check valves located at the inlet and outlet of the pump. The fabricated pumps were tested with various actuation voltages at different frequencies and duty cycles; an emphasis was placed on investigating the effect of valve flow conductance on the gas pumping characteristics. The pump with higher valve conductance could increase the operating frequency of the pump and affect the pumping characteristics from a pulsating flow to a continuous flow, leading to a higher gas flow rate. This electrostatic pump has a flow control resolution of 1 &mgr;L min-1; it could generate a gas flow up to 106 &mgr;L min-1. [ABSTRACT FROM AUTHOR]

Species transport in nanocapillary membrane systems has engaged considerable research interest, presenting technological challenges and opportunities, while exhibiting significant deviations from conventionally well understood bulk behavior in microfluidics. Nonlinear electrokinetic effects and surface charge of materials, along with geometric considerations, dominate the phenomena in structures with characteristic lengths below 100 nm. Consequently, these methods have enabled 3D micro- and nanofluidic hybrid systems with high-chemical selectivity for precise manipulation of mass-limited quantities of analytes. In this review, we present an overview of both fundamental developments and applications of these unique nanocapillary systems, identifying forces that govern ion and particle transport, and surveying applications in separation, sensing, mixing, and chemical reactions. All of these developments are oriented toward adding important functionality in micro-total analysis systems. [ABSTRACT FROM AUTHOR]

The electrochemical interfacial properties of a well-ordered self-assembled monolayer (SAM) of 1-undecanethiol (UDT) on evaporated gold surface have been investigated by electrochemical impedance spectroscopy (EIS) in electrolytes without a redox couple. Using a constant-phase element (CPE) series resistance model, prolonged incubation times (up to 120 h) show decreasing monolayer capacitance approaching the theoretical value for 1-undecanethiol. Using the CPE exponent α as a measure of ideality, it was found that the monolayer approaches an ideal dielectric (α = 0.992) under prolonged incubation, which is attributed to the reduction of pinholes and defects in the monolayer during coalescence and annealing of SAM chains. The SAMs behave as insulators until a critical potential, Vc, is exceeded in both cathodic and anodic regimes, where electrolyte ions are believed to penetrate the monolayers. Using a Randles circuit model for these cases, the variation of the capacitance and charge transfer resistance with applied dc potential shows decreased permeability to ionic species with prolonged incubation time. The E1S data show that UDT (methylene chain length n = 10), incubated for 120 h, forms a monolayer whose critical voltage range extends from -0.3 to 0.5 V versus Ag/AgCl, previously attained only for alkanethiol at n = 15. At low frequencies where ion diffusion occurs, almost pure capacitive phase (-89 deg) was attained with lengthy incubation. [ABSTRACT FROM AUTHOR]

Abstract: A micro-flame ionization detector (micro-FID) design is presented that is targeted for use in a portable gas sensor. Our micro-FID is based on a diffusion flame and features a folded flame structure that is more sensitive than a counter-flow flame designs. Unlike conventional FIDs that use a premixed or open diffusion flame, an air–hydrogen diffusion flame is employed and tested in an encapsulated structure of Quartz–Macor–Quartz layers. Diffusion flames are generally known to be more controllable and stable than premixed flames, where the stability of the micro-FID plays an important role for portable gas sensors. Various channel designs for oxidant and fuel flows meeting with different angles at the burner cavity are tested to obtain a stable flame and high output sensitivity over methane test samples. To verify the empirically designed microchannel, we simulate the temperature distribution in the microchannel by using computational fluid dynamics (CFD) software. To gauge the sensitivity of the device, the collected electric charges per mole (C/mol) is calculated and taken as a reference value of ionization efficiency. The result of the folded flame design is 1.959×10−2 C/mol for methane that is about 34 times higher than the result using a counter-flow flame, which is 5.73×10−4 C/mol for methane, while one of the commercial macro FIDs’ is 10−1 C/mol. This result shows that the micro-FID using the folded flame structure has higher ionization efficiency with less leakage of the analytes than of the classical counter-flow flame design. [Copyright &y& Elsevier]