Estimation of bending of micromachined gold cantilever due to residual stress

Electroplated gold is widely used as the material for the micromachined beam structures due to its excellent electrical and mechanical properties. This work attempts to analyze the surface micromachined gold cantilever beams under inherently present stress gradient. The structure is analyzed by using finite element method simulation at different intrinsic stress gradients. The gold layers are deposited using cyanide electroplating bath operated at different current densities. Residual stresses in electroplated gold layers deposited on photoresist coated silicon samples are estimated by using X-ray diffraction technique. Cantilever beam structures are fabricated using surface micromachining technique. The tip deflections of the fabricated cantilever beams are found to be ~16 and 8 μm corresponding to the 1.0 and 0.7 mA/cm² current densities (mean), respectively. The corresponding intrinsic stress gradients are estimated to be ?13.9 and ?7.2 MPa/μm, respectively. Simulated and measured values of residual stresses are well matched.     

Ember: A Smartphone Web Browser Interface for the Blind

Ember is a smartphone web browser interface for the blind. It was designed exclusively for the blind, keeping in mind their needs and requirements. With large screen targets and easy Braille based text entry, Ember aims to make browsing an enjoyable experience for the blind user. Furthermore, Ember has a verbal command option for easier input. A simple way to find targets on the interface has been incorporated with Ember, by using a screen guard with projections at six points that correspond to the six dots used in Braille. After testing, it was found that twenty-five out of twenty-eight volunteers, on an average, could navigate faster using the Ember audio navigation method than the traditional web browser, and the learning curve for the Ember interface is less steeper than the learning curve for the traditional browser. The Ember keypad was also tested against the QWERTY keypad and the SmartBraille, a well-recognized keypad for Braille-based text entry, and was found to be more intuitive and natural to use.     

Innovations in science education: Challenging and changing teachers’ roles and beliefs

Abstract:

This qualitative case study sought to identify and explore new roles adopted by three science teachers when the context of teaching and learning science was drastically changed. The study was conducted in a school utilizing student‐centred, self‐paced learning, where traditional classrooms have been replaced by subject‐specific resource areas and seminar rooms. Students do not follow a fixed daily schedule; instead, they plan their own school day and move freely between resource areas at self‐directed, often irregular intervals, according to daily and weekly goals. Through interviews, classroom observation, and personal journals, the study explored the ways in which the teachers perceived and implemented their roles in the changed context.     

Role and Optimization of the Active Oxide Layer in TiO2‐Based RRAM

TiO₂ is commonly used as the active switching layer in resistive random access memory. The electrical characteristics of these devices are directly related to the fundamental conditions inside the TiO₂ layer and at the interfaces between it and the surrounding electrodes. However, it is complex to disentangle the effects of film “bulk” properties and interface phenomena. The present work uses hard X‐ray photoemission spectroscopy (HAXPES) at different excitation energies to distinguish between these regimes. Changes are found to affect the entire thin film, but the most dramatic effects are confined to an interface. These changes are connected to oxygen ions moving and redistributing within the film. Based on the HAXPES results, post‐deposition annealing of the TiO₂ thin film was investigated as an optimisation pathway in order to reach an ideal compromise between device resistivity and lifetime. The structural and chemical changes upon annealing are investigated using X‐ray absorption spectroscopy and are further supported by a range of bulk and surface sensitive characterisation methods. In summary, it is shown that the management of oxygen content and interface quality is intrinsically important to device behavior and that careful annealing procedures are a powerful device optimisation technique.     

Wastewater for agriculture: A reuse-oriented planning model and its application in peri-urban China

The benefits of Integrated Water Resources Management (IWRM) are widely known but its recommendations remain thinly implemented. Designing wastewater treatment plants for reuse in irrigation is a particularly underutilized IWRM opportunity that could potentially increase agricultural yields, conserve surface water, offset chemical fertilizer demand, and reduce the costs of wastewater treatment by eliminating nutrient removal processes. This paper presents a novel planning model, consisting of a reuse-centric performance assessment and optimization model to help design wastewater treatment plants for reuse in agriculture. The performance assessment and optimization model are described, and their coupled application is demonstrated in the peri-urban district of Pixian, China. Based on the results of the performance assessment, two reuse scenarios are evaluated: wastewater to supplement business as usual (BAU) irrigation, and wastewater to replace BAU irrigation. The results indicate that wastewater supplementation could increase profits by $20 million (M) annually; alternatively, wastewater replacement could conserve 35 Mm³ of water in local rivers each year.     

Lapping assisted dissolved wafer process of silicon for MEMS structures

Dissolved wafer process (DWP) is being extensively used to fabricate complex micro-electro-mechanical system (MEMS) structures. Etching non-uniformity, increased surface roughness and duration of DWP is often influence MEMS devices yields. This paper presents a modified DWP involving lapping and polishing followed by chemical etching of silicon to release MEMS based structure. The lapping experiments are performed using silicon-carbide (SiC) and alumina (Al₂O₃) abrasive. The polishing of the silicon samples is also done. The lapped and polished surfaces are compared with etched silicon surfaces in KOH and EDP solutions. The lapping-polishing process is found to be 2.5 (Al₂O₃)–3 (SiC) times faster than a standard etching processes based on KOH and EDP solutions. The average roughness (R_a) of the lapped–polished silicon surfaces are found to be 19.2 and 32.9 nm corresponding to SiC and Al₂O₃ abrasive respectively. The R_a value of EDP and KOH etched silicon surfaces are found to be 16.2 and 238.3 nm respectively. Based on the lapping—polishing results, SiC based lapping followed by polishing of silicon surface can be used as an alternate of etching of silicon during DWP. In this paper, a two-step DWP, involving lapping-polishing followed by EDP chemical etching of silicon, is used to fabricate suspended comb-type microaccelerometer structure.     

Food safety considerations and research priorities for the cultured meat and seafood industry

Cell-cultured meat and seafood offer a sustainable opportunity to meet the world's increasing demand for protein in a climate-changed world. A responsible, data-driven approach to assess and demonstrate safety of cell-cultured meat and seafood can support consumer acceptance and help fully realize the potential of these products. As an initial step toward a thorough demonstration of safety, this review identifies hazards that could be introduced during manufacturing, evaluates applicability of existing safety assessment approaches, and highlights research priorities that could support safe commercialization. Input was gathered from members of the cultured meat and seafood industry, researchers, regulators, and food safety experts. A series of workshops were held with 87 industry representatives and researchers to create a modular manufacturing process diagram, which served as a framework to identify potential chemical and biological hazards along the steps of the manufacturing process that could affect the safety of a final food product. Interviews and feedback on draft documents validated the process diagram and supported hazard identification and evaluation of applicable safety methods. Most hazards are not expected to be novel; therefore, safety assessment methods from a range of fields, such as conventional and novel foods, foods produced from biotechnology, pharmaceuticals, and so forth, are likely to be applicable. However, additional assessment of novel inputs or products with significant differences from existing foods may be necessary. Further research on the safety of the inputs and associated residues, potential for contamination, and development of standardized safety assessment approaches (particularly animal-free methods) is recommended.     

Synthesis and Biological Studies of Dodecameric Cationic Antimicrobial Peptides Containing Tetrahydrofuran Amino Acids

We report here a concise route to synthesize various stereoisomers of tetrahydrofuran amino acids (TAAs) and the synthesis of TAA-containing linear cationic dodecapeptides. Some of these linear peptides show slightly better antimicrobial activities than their tetra- and octameric congeners, but no activity against Mycobacterium tuberculosis, for which octapeptides exhibited by far the best results; this implies that antibacterial activity is dependent on the length of these linear peptides. All the dodecapeptides described here were found to be toxic in nature against Vero cells. The study helps to delineate the optimal length of this series of linear peptides and select potential leads in the development of novel cationic peptide-based antibiotics.     

Conjugated linoleic acids attenuate FSH- and IGF1-stimulated cell proliferation; IGF1, GATA4, and aromatase expression; and estradiol-17β production in buffalo granulosa cells involving PPARγ, PTEN, and PI3K/Akt

Conjugated linoleic acid (CLA) has drawn much interest in last two decades in the area ranging from anticancer activity to obesity. A number of research papers have been published recently with regard to CLA's additional biological functions as reproductive benefits. However, not much is known how this mixture of isomeric compounds mediates its beneficial effects particularly on fertility. In this study, we demonstrated the cross talk between downstream signaling of CLA and important hormone regulators of endocrine system, i.e. FSH and IGF1, on buffalo granulosa cell function (proliferation and steroidogenesis). Experiments were performed in primary serum-free buffalo granulosa cell culture, where cells were incubated with CLA in combination with FSH (25?ng/ml) and IGF1 (50?ng/ml). Results showed that 10?μM CLA inhibits FSH- and IGF1-induced granulosa cell proliferation; aromatase, GATA4, and IGF1 mRNA; and estradiol-17β production. Western blot analysis of total cell lysates revealed that CLA intervenes the IGF1 signaling by decreasing p-Akt. In addition, CLA was found to upregulate peroxisome proliferator-activated receptor-gamma (PPARG) and phosphatase and tensin homolog (PTEN) level in granulosa cells. Further study using PPARG- and PTEN-specific inhibitors supports the potential role of CLA in granulosa cell proliferation and steroidogenesis involving PPARG, PTEN, and PI3K/Akt pathway.