In situ transmission electron microscopy studies and real-time digital imaging

A newly designed CCD camera has been utilized for real-time and static image acquisitions. The performance of the camera is demonstrated for heating/cooling in-situ TEM experiments performed on a commercial high strength aluminium alloy using a double tilt heating holder. The real-time digital imaging capability of the new camera should facilitate the in-situ TEM that is now re-establishing itself as a strategic tool for materials characterization.     

Optimizing size and distribution of voids in phenolic resins through the choice of catalyst types

Phenolics are widely used for over a century in different industries due to their chemical resistance and thermomechanical properties. However, the presence of voids in phenolic resins has negative effects on the mechanical properties and a conventional approach is to avoid these by utilizing very long cure cycles. Our alternative approach investigates the tailoring of void size and distribution to achieve a better balance between processing time and mechanical properties. Therefore, we produced phenolic resin with a void-free microstructure by a long cure cycle as a reference. To alter the void size and distributions, we utilized different catalysts and a short cure cycle to obtain phenolic resins and test their flexural properties with respect to the reference. We investigated the fracture surfaces of all materials by SEM, FTIR and compared results to finite element modeling that confirmed the effects of different void size and distributions on the mechanical properties. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48249.     

Development and validation of a simple analytical method for the determination of 2,4,6-trichloroanisole in wine by GC–MS

A novel method for the residue analysis of wine spoilage compound 2,4,6-trichloroanisole is reported. Wine (60 ml) was extracted with 2 ml toluene in presence of 24 g MgSO₄ and 6 g NaCl. Cleanup of the toluene phase by dispersive solid phase extraction with mixture of 100 mg CaCl₂, 25 mg primary secondary amine and 50 mg MgSO₄ was effective in minimising co-extractives and matrix effects. Time-of-flight and tandem mass spectrometric parameters were optimised to achieve linearity over 0.25–500 ng ml⁻¹ and method detection limit 0.0083 ng ml⁻¹ which is well below the odour threshold of 0.04 ng ml⁻¹. Recoveries at 0.04, 0.2 and 0.8 ng ml⁻¹ were within 80–110% (±8%). The method was reproducible when tested for Argentinean wines with intra-laboratory Horwitz ratios being <0.20 in white and red wines at both the laboratories of India and Argentina. The method could be successfully applied for incurred wine samples.     

Dehydration of potato slices following brief dipping in osmotic solutions: Effect of conditions and understanding the mechanism of water loss

A novel variant of osmotic dehydration, named here as postdipping dehydration—where a material is dipped in a salt or sugar solution for a very short time followed by simple exposure to ambient conditions was explored with the aim of lowering water content of potato slices but at the same time not gain a high level of sugar/salt. The rate of water loss, which was rapid initially, was found to approach equilibrium. This article also explored whether the water loss process could subsequently be kick started once again, by employing a multistage process, where each stage consisted of osmotic solution dipping followed by ambient holding of the potato slices that had reached equilibrium in the earlier stage. Water loss values comparable to conventional osmotic dehydration could be achieved thus, but with significantly lower overall solid gain (<50%)—which can potentially yield a significantly healthy product option.     

A Fully-Passive Wireless Microsystem for Recording of Neuropotentials using RF Backscattering Methods

The ability to safely monitor neuropotentials is essential in establishing methods to study the brain. Current research focuses on the wireless telemetry aspect of implantable sensors in order to make these devices ubiquitous and safe. Chronic implants necessitate superior reliability and durability of the integrated electronics. The power consumption of implanted electronics must also be limited to within several milliwatts to microwatts to minimize heat trauma in the human body. In order to address these severe requirements, we developed an entirely passive and wireless microsystem for recording neuropotentials. An external interrogator supplies a fundamental microwave carrier to the microsystem. The microsystem comprises varactors that perform nonlinear mixing of neuropotential and fundamental carrier signals. The varactors generate third-order mixing products that are wirelessly backscattered to the external interrogator where the original neuropotential signals are recovered. Performance of the neuro-recording microsystem was demonstrated by wireless recording of emulated and in vivo neuropotentials. The obtained results were wireless recovery of neuropotentials as low as approximately 500 microvolts peak-to-peak (μV(pp)) with a bandwidth of 10 Hz to 3 kHz (for emulated signals) and with 128 epoch signal averaging of repetitive signals (for in vivo signals).     

A framework combining meshfree analysis and adaptive kriging for optimization of stiffened panels

Structural and Multidisciplinary Optimization - A framework is developed for structural optimization using an Element Free Galerkin (EFG) method for analyzing the structure, a kriging for surrogate...     

Development of a re‐aeration equation for the simulation of dissolved oxygen in degraded streams

Discharge of domestic and industrial wastewater into the water bodies is the prime source of degradation of the freshwater ecosystem. Re‐aeration of the river allows the rejuvenation of river water quality by absorbing oxygen from the atmosphere at the air‐water interface. An accurate estimation of the re‐aeration coefficient helps to determine the assimilative capacity of streams and wastewater management also. This paper aims to develop the re‐aeration equation and its validation by modelling dissolved oxygen of the Yamuna River. Predictive re‐aeration equations are used to identify their applicability to the study area and the new equation is designed using multivariate statistical regression techniques. QUAL2Kw model is used to validate the equation by modelling dissolved oxygen. Results indicate that the developed equation performs better than the predictive re‐aeration equations for the prediction of water quality.     

Template assisted synthesis of europium sulfide nanotubes

We report the template assisted synthesis of europium sulfide (EuS) nanotubes. These structures were fabricated by thermolysis of a single source precursor that was infused into porous alumina membranes. TEM and STEM analysis confirmed the formation of EuS nanotubes, while X-ray diffraction and selected area electron diffraction analysis probed their crystallinity. Room temperature optical spectroscopy identified an energy-band blue-shift in the absorption spectra into the UV, compared to bulk EuS. Interestingly, no such shift was observed in the photoluminescence. We attribute these changes to quantum confinement effects on the photoexcited charge carriers within the nanotubes' walls and strain-induced lattice deformations.     

Firefly Algorithm for Joint Estimation of Frequency Offsets and Channel in OFDMA Uplink

This paper addresses the problem of joint maximum-likelihood estimation of carrier frequency offsets, and channel responses in an orthogonal frequency division multiple access (OFDMA) uplink, which is a computationally-intensive, multiparameter, multidimensional problem. We propose to apply a recently-developed meta-heuristic algorithm called the firefly algorithm (FA) for the estimation of required parameters. We also introduce a new initialization procedure for the FA algorithm based on the separability of cost functions, which drastically reduces its computational complexity. A separate pilot OFDMA symbol is transmitted prior to the data symbols to estimate the parameters. The proposed technique is shown to achieve excellent performance at reduced computational complexity, especially at low signal-to-noise ratio. Also, it can be applied to OFDMA systems with any type of carrier assignment schemes. The significant features of the proposed estimation method are substantiated through extensive computer simulation studies and are compared with an important classical estimation technique available for the problem, to highlight its superiority.     

Balancing the Role of Priors in Multi-Observer Segmentation Evaluation

Comparison of a group of multiple observer segmentations is known to be a challenging problem. A good segmentation evaluation method would allow different segmentations not only to be compared, but to be combined to generate a “true” segmentation with higher consensus. Numerous multi-observer segmentation evaluation approaches have been proposed in the literature, and STAPLE in particular probabilistically estimates the true segmentation by optimal combination of observed segmentations and a prior model of the truth. An Expectation–Maximization (EM) algorithm, STAPLE’s convergence to the desired local minima depends on good initializations for the truth prior and the observer-performance prior. However, accurate modeling of the initial truth prior is nontrivial. Moreover, among the two priors, the truth prior always dominates so that in certain scenarios when meaningful observer-performance priors are available, STAPLE can not take advantage of that information. In this paper, we propose a Bayesian decision formulation of the problem that permits the two types of prior knowledge to be integrated in a complementary manner in four cases with differing application purposes: (1) with known truth prior; (2) with observer prior; (3) with neither truth prior nor observer prior; and (4) with both truth prior and observer prior. The third and fourth cases are not discussed (or effectively ignored) by STAPLE, and in our research we propose a new method to combine multiple-observer segmentations based on the maximum a posterior (MAP) principle, which respects the observer prior regardless of the availability of the truth prior. Based on the four scenarios, we have developed a web-based software application that implements the flexible segmentation evaluation framework for digitized uterine cervix images. Experiment results show that our framework has flexibility in effectively integrating different priors for multi-observer segmentation evaluation and it also generates results comparing favorably to those by the STAPLE algorithm and the Majority Vote Rule.