Photoresist patterned thick-film piezoelectric elements on silicon

A fundamental limitation of screen printing is the achievable alignment accuracy and resolution. This paper presents details of a thick-resist process that improves both of these factors. The technique involves exposing/developing a thick resist to form the desired pattern and then filling the features with thick film material using a doctor blading process. Registration accuracy comparable with standard photolithographic processes has been achieved resulting in minimum feature sizes of <50 ?m and a film thickness of 100 ?m. Piezoelectric elements have been successfully poled on a platinised silicon wafer with a measured d 33 value of 60 pCN?1

A study of the macro-invertebrates of Lakes Naivasha, Oloidien and Sonachi, Kenya

Des prélèvements de macro-invertébrés ont été faits dans le lac Naivasha en décembre-janvier 1982-83 et en juillet-août 1984, et dans les deux lacs avoisinants, Oloidien et Sonachi, seulement en 1984. On a remarqué une différence considérable dans les listes faunistiques obtenues au cours des deux visites. La comparaison avec les listes obtenues par les expéditions de Percy Sladen (1929) and Cambridge (1930-31) a aussi révélé un changement majeur à long terme, y compris un changement complet des faunes d'oligochètes et de mollusques. Le changement à court terme de 1982/83 à 1984 est attribué aux importantes fluctuations naturelles du niveau de l'eau. Parmi les autres facteurs qui ont pu causer les changements à long terme, on cite la disparition des macrophytes submergés, broutés par des espèces introduites, Coypou (#Myocaster coypus) et écrevisse (#Procambarus Clarkii), l'introduction des espèces étrangères et des pratiques agricoles entraînant l'enlèvement d'une grande quantité de papyrus et l'emploi toujours croissant de l'eau du lac pour l'irrigation. (Résumé d'auteur

Conjugatable water-soluble Pt(ii) and Pd(ii) porphyrin complexes: Novel nano- and molecular probes for optical oxygen tension measurement in tissue engineering

Measurement of oxygen tension in compressed collagen sheets was performed using matrix-embedded optical oxygen sensors based on platinum(II) and palladium(II) porphyrins supported on polyacrylamide nanoparticles. Bespoke, fully water-soluble, mono-functionalised Pt(II) and Pd(II) porphyrin complexes designed for conjugation under mild conditions were obtained using microwave-assisted metallation. The new sensors display a linear response (1/τ vs. O₂) to varying oxygen tension over a biologically relevant range (7.0 × 10⁻⁴ to 2.7 × 10⁻¹ mM) in aqueous solutions; a behaviour that is maintained following conjugation to polyacrylamide nanoparticles, and following embedding of the nanosensors in compressed collagen sheets, paving the way to innovative approaches for real-time resolution of oxygen gradients throughout 3D matrices useful for tissue regeneration

Flexural performance of concrete slabs reinforced with GFRP rebars

The use of non-metallic fibre reinforced polymer (FRP) reinforcement as an alternative to steel reinforcement in concrete is gaining acceptance mainly due to its high corrosion resistance. High strength-to-weight ratio, high stiffness-to-weight ratio and ease of handling and fabrication are added advantages. Other benefits are that they do not influence to magnetic fields and radio frequencies and they are thermally non-conductive. However, the stress-strain relationship for Glass FRP is linear up to rupture when the ultimate strength is reached. Unlike steel reinforcing bars, GFRP rebars do not undergo yield deformation or strain hardening before rupture. Also, GFRP reinforcement possesses a relatively low elastic modulus of elasticity compared with that of steel. As a consequence, for GFRP reinforced sections, larger deflections and crack widths are expected than the ones obtained from equivalent steel reinforced sections for the same load. This paper presents a comparison of the experimental results with those predicted by the ACI 440 code in terms of; measured cracking moment, load-deflection relationships, ultimate capacity, modes of failure, stresses and crack width. This is to investigate the suitability of using the existing ACI design equations for predicting the flexural behaviour of samples reinforced with GFRP rebars. In this investigation, it appears that the ACI code equations on the whole over predict (i.e. crack widths and midspan deflection) the experimental results. On the other hand, the maximum experimental moment satisfies the ACI condition (i.e. unfactored design moment)

Verification of shrinkage curvature code prediction models

An attempt is made to theoretically and experimentally verify the shrinkage curvature models presented in Eurocode 2 and BS 8110. These codes claim that the models originally derived and proven for uncracked sections are suitable, with modification, for predicting the behaviour of cracked sections, although this claim has never been proven experimentally. To achieve verification, an alternative theoretical approach is initially proposed in this paper. In this theoretical model, the effect of shrinkage, creep and the variation in the neutral axis position of the section are taken into account. The stresses developed in the steel and concrete at a cracked section according to this theoretical model are then applied to a finite-element (FE) model representing a portion of the beam from the crack to mid-way between the crack and an adjacent crack. Ultimately, the mean curvature is determined. Experimentally, pairs of beams were cast and subjected to a level of flexural loading to produce a stabilised crack pattern in the constant-moment zone. The behaviour of the beams was monitored for up to 180 days. For any pair of beams, one beam was cast using a high-shrinkage concrete and the other with a low-shrinkage concrete. Each concrete type, however, exhibits similar creep. Therefore, shrinkage curvature can be obtained by subtracting the long-term movements of one beam from the other. These experimentally defined curvatures were compared with the mean curvatures obtained from the FE analysis. The comparison showed reasonable agreement. The curvatures were also compared with uncracked and cracked curvatures predicted by the codes. The curvatures derived in this investigation fell within the boundaries of the uncracked and cracked curvatures predicted by the codes and, for the fully cracked case, the curvatures were closer to the uncracked boundary

Resonance-Induced Effects in Photonic Crystals

For the case of a simple face-centered-cubic photonic crystal of homogeneous dielectric spheres, we examine to what extent single-sphere Mie resonance frequencies are related to band gaps and whether the width of a gap can be enlarged due to nearby resonances. Contrary to some suggestions, no spectacular effects may be expected. When the dielectric constant of the spheres $\epsilon_s$ is greater than the dielectric constant $\epsilon_b$ of the background medium, then for any filling fraction $f$ there exists a critical $\epsilon_c$ above which the lowest lying Mie resonance frequency falls inside the lowest stop gap in the (111) crystal direction, close to its midgap frequency. If $\epsilon_s <\epsilon_b$, the correspondence between Mie resonances and both the (111) stop gap and a full gap does not follow such a regular pattern. If the Mie resonance frequency is close to a gap edge, one can observe a resonance-induced widening of a relative gap width by $\approx 5$.Comment: 14 pages, 3 figs., RevTex. For more info look at http://www.amolf.nl/external/wwwlab/atoms/theory/index.htm

Reliable UHF long-range textile-integrated RFID tag based on a compact flexible antenna filament

This paper details the design, fabrication and testing of flexible textile-concealed RFID tags 1 for wearable applications in a smart city/ smart building environment. The proposed tag designs aim 2 to reduce the overall footprint, enabling textile integration whilst maintaining the read range. The 3 proposed RFID filament is less than 3.5 mm in width and 100 mm in length. The tag is based on an 4 electrically small (0.0033λ 2) high-impedance planar dipole antenna with a tuning loop, maintaining a 5 reflection coefficient less than −21 dB at 915 MHz, when matched to a commercial RFID chip mounted 6 alongside the antenna. The antenna strip and the RFID chip are then encapsulated and integrated in 7 a standard woven textile for wearable applications. The flexible antenna filament demonstrates a 1.8 8 dBi gain which shows a close agreement with the analytically calculated and numerically simulated 9 gains. The range of the fabricated tags has been measured and a maximum read range of 8.2 m was 10 recorded at 868 MHz. Moreover, the tag's maximum calculated range at 915 MHz is 18 m, which 11 is much longer than the commercially available laundry tags of larger length and width, such as 12 Invengo RFID tags. The reliability of the proposed RFID tags has been investigated using a series 13 of tests replicating textile-based use case scenarios which demonstrates its suitability for practical 14 deployment. Washing tests have shown that the textile-integrated encapsulated tags can be read after 15 over 32 washing cycles, and that multiple tags can be read simultaneously while being washed

Ultrastructure and complex polar architecture of the human pathogen Campylobacter jejuni

Campylobacter jejuni is one of the most successful food-borne human pathogens. Here we use electron cryotomography to explore the ultrastructure of C. jejuni cells in logarithmically growing cultures. This provides the first look at this pathogen in a near-native state at macromolecular resolution (∼5 nm). We find a surprisingly complex polar architecture that includes ribosome exclusion zones, polyphosphate storage granules, extensive collar-shaped chemoreceptor arrays, and elaborate flagellar motors

Effective calculation of LEED intensities using symmetry-adapted functions

The calculation of LEED intensities in a spherical-wave representation can be substantially simplified by symmetry relations. The wave field around each atom is expanded in symmetry-adapted functions where the local point symmetry of the atomic site applies. For overlayer systems with more than one atom per unit cell symmetry-adapted functions can be used when the division of the crystal into monoatomic subplanes is replaced by division into subplanes containing all symmetrically equivalent atomic positions

Inversion of Randomly Corrugated Surfaces Structure from Atom Scattering Data

The Sudden Approximation is applied to invert structural data on randomly corrugated surfaces from inert atom scattering intensities. Several expressions relating experimental observables to surface statistical features are derived. The results suggest that atom (and in particular He) scattering can be used profitably to study hitherto unexplored forms of complex surface disorder.Comment: 10 pages, no figures. Related papers available at http://neon.cchem.berkeley.edu/~dan