Modeling Hydrodynamic Cavitation

A simplified and unified model has been proposed to study the cavitation phenomena in hydraulic devices, with emphasis on the venturi tube and high-speed homogenizer. A turbulence model analogous to the acoustic cavitation has been developed and the dynamics of the cavities as a cluster has been considered. The prediction of the cavitation inception number has been made for various operating conditions and has been compared with the experimental observations. The effect of operating parameters, such as inlet pressure and fully recovered downstream pressure, has been studied numerically and compared with the data in the literature for the case of the venturi. The predicted cavitation intensities were compared indirectly with the experimental results. It has been found that optimum operating conditions do exist at which the observable cavitational effect is maximum. In the case of the high-speed homogenizer, the predicted effects as a function of rotational speed have been compared with the results of the aqueous KI decomposition reaction and have been found to match well. The study concludes with the recommendations and methods for possibly optimizing hydrodynamic cavitation phenomena for maximum effect.     

A stochastic approach to the mode of deformation and contact between rough surfaces

The real area of contact between a rough and an ideally flat surface is evaluated from the spectral moments of the profile of the rough surface. A stochastic criterion for plastic deformation of the asperities is developed and applied to determine the percentage of plastic and elastic deformation in the total area of contact at a given separation. An illustration is given to delineate the theory through experimental profile data obtained from a ground surface.     

Graphene Oxide Attenuates Toxicity of Amyloid-β Aggregates in Yeast by Promoting Disassembly and Boosting Cellular Stress Response

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease, with the aggregation of misfolded amyloid-β (Aβ) peptides in the brain being one of its histopathological hallmarks. Recently, graphene oxide (GO) nanoflakes have attracted significant attention in biomedical areas due to their capacity of suppressing Aβ aggregation in vitro. The mechanism of this beneficial effect has not been fully understood in vivo. Herein, the impact of GO on intracellular Aβ42 aggregates and cytotoxicity is investigated using yeast Saccharomyces cerevisiae as the model organism. This study finds that GO nanoflakes can effectively penetrate yeast cells and reduce Aβ42 toxicity. Combination of proteomics data and follow-up experiments show that GO treatment alters cellular metabolism to increases cellular resistance to misfolded protein stress and oxidative stress, and reduces amounts of intracellular Aβ42 oligomers. Additionally, GO treatment also reduces HTT103QP toxicity in the Huntington's disease (HD) yeast model. The findings offer insights for rationally designing GO nanoflakes-based therapies for attenuating cytotoxicity of Aβ42, and potentially of other misfolded proteins involved in neurodegenerative pathology.     

Environmental impact assessment of river valley projects in upper Teesta basin of Eastern Himalaya with special reference to fish conservation: a review

Teesta river basin in Eastern Himalaya is being subjected to cascade hydropower development. To assess the impacts of this developmental activity on fish fauna of the basin, fish habitats of the four largest tributaries in the basin were selected for the present study. A total of 18 large hydroelectric projects are planned on these rivers. Here, a total of 11 EIAs and 2 carrying capacity studies in Teesta basin were reviewed. Our investigations show that after commissioning all the projects, 52–88% of the free-flowing river stretches will be diverted and 7.6–24% of the riverine ecosystems will be converted into semi lacustrine ecosystems in different rivers. The cascade hydropower development is likely to affect more than 100 fish species. All the EIA reports reviewed have investigated fish species richness, impacts on fish fauna and fishery management plans. EIA studies and management plans, however, do not adequately address important ecological and conservation issues due to various limitations. An integrated fish conservation plan for the upper Teesta basin is suggested in this contribution.     

Structural, dielectric and multiferroic properties of Er and La substituted BiFeO3 ceramics

Erbium (Er) and lanthanum (La) substituted BiFeO₃ (BFO) ceramics have been prepared through conventional solid solution route. X-ray diffraction data indicated a gradual phase transition from rhombohedral to monoclinic structure in Bi_0·9?x La_0·1Er _x FeO₃ (x = 0·05, 0·07 and 0·1) (BLEFO _{x = 0·05, 0·07, 0·1}) ceramics. Differential thermal analysis (DTA) measurements of BFO samples showed a ferroelectric transition at 835°C, whereas it is shifted to 792°C for BLEFO _{x = 0·1}. The Raman spectra of BLEFO _{x = 0·05, 0·07, 0·1} samples showed the shift of Raman modes to higher wavenumbers and suppression of A₁ modes indicating decrease in ferroelectricity. The Raman spectra also indicated the structural transformation due to Er and La substitution in BFO. On subsequent erbium doping, the intrinsic dielectric constant is found to decrease from 68 (for pure BFO) to 52 for BLEFO _{x = 0·05} to 43 for BLEFO _{x = 0·07} but increased to 89 for BLEFO _{x = 0·1} when compared to pure BFO. The increase in Er content resulted in the increase in spontaneous magnetization (0·1178 emu/g at 8T for BLEFO _{x = 0·1}) due to collapse of spin cycloid structure. Ferroelectric remnant polarization of BLEFO _{x = 0·05} and BLEFO _{x = 0·07} decreases when compared to pure BFO while small remnant polarization (close to paraelectric behaviour) is evident for BLEFO _{x = 0·1}.     

PMN–PT based relaxor ferroelectrics as very smart materials

The basic classification of smart materials and structures is reviewed briefly. The role of nonlinear response for achieving field-tunability of properties is described in simple terms. The observation of the two-way shape-memory effect in a solid solution of lead magnesium niobate (PMN) and lead titanate (PT) for the nominal atomic composition 65:35 is reported. Possible factors influencing the occurrence of the two-way effect are discussed. It is argued that such relaxor ferroelectric ceramics can function as smart materials (rather than serving merely as components of smart structures), because they can meet the “information-reduction” criterion. And they qualify to be called very smart because they have a fairly large number of smartness attributes, including the two-way shape-memory attribute reported here.     

Evaluation of the stability of paper basis-weight profiles using multivariate time series

In the papermaking process, a major concern is maintaining uniform basis weight in the paper sheet. Basis weight, the weight per unit area of the paper, can vary as a function of both time and position across the width of the paper machine. In this short paper, a quantitative index for evaluating the stability, i.e., the similarity of consecutive basis-weight profiles taken across the width of a paper machine, is presented and used to analyze the stability of two production paper machines. The index is determined from autoregressive moving average multivariate time-series models developed for the profile data. With this approach, a more consistent estimate of basis-weight stability can be obtained with fewer profiles by removing the correlation imparted by the papermaking process. Moreover, the parameters of the model can be used to analyze possible sources of basis-weight instability.     

Non-Coherent Pulse Detection with a Large Predetection Bandwidth

For a non-coherent detection circuit with a broad-band pre-detection filter and narrow-band post-detection-filter, equations are obtained for the probability of detection of a pulsed sinusoidal signal embedded in white noise. The equations can be used to calculate the detection probability directly from envelope form, noise power at the input of the circuit and the impulse response of the postdetection filter. The application of the equations is illustrated with reference to a sliding correlator acquisition circuit for PN-code generators.