Design and Simulation of PVDF‐MOSFET Based MEMS Hydrophone

Abstract

Modeling has become a vital tool of investigation in all fields, since experimenting with real systems is not only costly, but also time‐consuming and even impossible in some situations. This work presents the design and simulation of an integrated PVDF‐based MEMS hydrophone with improved sensitivity, which contains a MOSFET sense amplifier. The piezoelectric polymer, polyvinylidene fluoride (PVDF), senses the input acoustic signal. As hydrophone size decreases, it becomes necessary to provide an amplifier or buffer in close proximity to avoid sensitivity loss due to interconnect capacitance. This suggests the concept of hydrophones merged with electronics in an integrated circuit environment. So, the integration of PVDF with an on‐chip MOSFET is implemented. The extended gate electrode of the MOSFET is placed over an epitaxial layer isolated from the silicon substrate and is padded with a dielectric layer, SU‐8, which significantly reduces the extended gate capacitance and, therefore, increases the sensor sensitivity. The variation of the transducer output when the input acoustic signal is applied is studied. The simulation is done using the MEMS simulation software, Coventorware.     

A longitudinal examination of parenting behaviors and perceived discrimination predicting Latino adolescents' ethnic identity.

Characteristics of the familial and societal context were examined as predictors of Latino adolescents' (N = 323; 49.5% female) ethnic identity. Consistent with previous work, familial ethnic socialization significantly predicted future levels of ethnic identity exploration, resolution, and affirmation for both male adolescents and female adolescents, although the association was significantly stronger for female adolescents than male adolescents for exploration and resolution. Furthermore, for male adolescents, higher levels of familial ethnic socialization were significantly associated with a faster rate of growth for ethnic identity resolution. In addition, paternal warmth–support emerged as a significant longitudinal predictor of male adolescents', but not female adolescents', ethnic identity exploration. Finally, perceived discrimination was significantly associated with male adolescents', but not female adolescents', ethnic identity exploration and affirmation. Significant gender differences in the relations of interest highlight the need to consider variability in the process of ethnic identity formation by gender. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Polyester composites of short pineapple fiber and glass fiber: Tensile and impact properties

The tensile and impact performance of intimately mixed (IM) hybrid composites based on glass fiber (GF) and pineapple leaf fiber (PALF) was investigated. The composite was fabricated at constant volume fraction of fiber 0.3 V_f (fiber 0.3 and matrix 0.7). Keeping the volume fraction of matrix a constant (0.7 V_f), we have varied the PALF/GF ratio from 0 to 1. Incorporation of 0.1 volume fraction of GF increases the tensile strength of the hybrid composite by about 28%. The tensile strength showed a further increase when the volume fraction is changed to 0.7 and 0.9 V_f of GF. Intimately mixed hybrid composites exhibited higher impact strength than the individual fiber composites; the composite of PALF/GF ratio 70:30 showed maximum impact strength of 1203 J/m. A positive hybrid effect is observed for impact properties. Scanning electron micrographs of the fractured surfaces were examined to understand the fiber‐matrix adhesion. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Route to co-acrylic modified alkyd resins via a controlled polymerization technique

Acrylic modified alkyds were achieved from sequential polymerization of acrylic monomers in the presence of alkyd macro-RAFT agents. Macro-RAFT agents were reached by end-capping a soya-based alkyd with a carboxy-functional trithiocarbonate. The resulting material was then utilized as the RAFT chain transfer agent to affix acrylic blocks onto the alkyd backbone. Butyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate were the acrylic monomers used to achieve the acrylic blocks both individually and in combination. The resulting materials were characterized by various analytical techniques including size-exclusion chromatography (SEC), Fourier transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. Size exclusion chromatography confirms the controlled nature of this approach to acrylated-alkyds and corroborates the NMR spectra that distinctly show the presence of acrylic blocks. Side reactions with the pendant fatty acids and the formation of homopolyacrylate are also distinguished from the analytical results, however, they are suppressed. Pseudo-first-order kinetics behavior and conversion versus molecular weight plots show that the RAFT-mediated reaction afforded a more controlled free radical process for the synthesis of acrylated-alkyd materials. Use of the alkyd macro-RAFT agent provided a new path to acrylated-alkyds that affords a more controlled way to tailor specific material properties.     

A Modelling Approach to Estimate the Level and Molecular Weight Distribution of β-Glucan During the Baking of an Oat-Based Bread

Oat and oat products containing β-glucans are associated with many health claims. Both the level and molecular weight of β-glucans play an important role in determining the physiological efficacy of β-glucan in terms of health benefits, including reducing blood cholesterol levels. The objective of this study was to develop a probabilistic model to investigate the effect of various process stages in bread making on the level of β-glucan (BG) and its molecular weight (Mw) distribution using Monte Carlo simulation techniques. Various composite flours were formulated by substituting wheat flour (WF) with oat whole flour (OWF), oat refined flour (ORF), oat bran (OB) or rolled oats (RO). The baseline model predicted an overall mean reduction of 49% in BG in baked bread. The mean Mw of β-glucan in all composite flours was reduced following processing and baking from 1.22 to 0.77 × 10⁶ (g/mol) for OWF + WF, 1.07 to 0.68 × 10⁶ (g/mol) for ORF + WF, 1.17 to 0.75 × 10⁶ (g/mol) for OB + WF and 1.25 to 0.80 × 10⁶ (g/mol) for RO + WF. In all formulated breads, high molecular weight β-glucan was observed to be more susceptible to degradation compared with medium molecular weight and to lower molecular weight. A sensitivity analysis highlighted the negative influence of WF on β-glucan content and the BG reduction with fermentation time. The scenario analysis showed a positive influence on the level of BG with increase addition of oat flour in all formulated breads. The model was validated with experimental data and values were found to be within the confidence interval of predicted BG levels. This model facilitates the optimisation of various steps in the bread making process and highlights the potential for oat flour to improve the nutritional quality of baked bread.     

Dynamic mechanical analysis of pineapple leaf/glass hybrid fiber reinforced polyester composites

The dynamic mechanical properties of randomly oriented intimately mixed hybrid composites based on pineapple leaf fibers (PALF) and glass fibers (GF) in unsaturated polyester (PER) matrix were investigated. The PALFs have high‐specific strength and improve the mechanical properties of the PER matrix. In this study, the volume ratio of the two fibers was varied by incorporating small amounts of GF such as PALF/GF, 90/10, 80/20, 70/30, and 50/50, keeping the total fiber loading constant at 40 wt%. The dynamic modulus of the compositeswas found to increase on GF addition. The intimately mixed (IM) hybrid composites with PALF/GF, 80/20 (0.2 V_f GF) showed highest E′ values and least damping. Interestingly, the impact strength of the composites was minimum at this volume ratio. The composites with 0.46 V_f GF or PALF/GF (50/50) showed maximum damping behavior and highest impact strength. The results were compared with hybrid composites of different layering patterns such as GPG (GF skin and PALF core) and PGP (PALF skin and GF core). IM and GPG hybrid composites are found more effective than PGP. The activation energy values for the relaxation processes in different composites were calculated. The overall results showed that hybridization with GF enhanced the performance properties. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Axially aligned electrically conducting biodegradable nanofibers for neural regeneration

In this study, electrically conducting axially aligned nanofibers have developed to provide both electrical and structural cues. Poly(lactide-co-glycolide) (PLGA) with poly(3-hexylthiophene) (PHT) was electrospun into 2D random (196 ± 98 nm) and 3D axially aligned nanofibers (200 ± 80 nm). Electrospun random and aligned PLGA–PHT fibers were characterized for surface morphology, mechanical property, porosity, degradability, and electrical conductivity. The pore size of random PLGA–PHT nanofibers (6.0 ± 3.3 μm) were significantly higher than the aligned (1.9 ± 0.4 μm) (P < 0.05) and the Young’s modulus of aligned scaffold was significantly lower than the random. Aligned nanofibers showed significantly lesser degradation rate and higher electrical conductivity (0.1 × 10^?5 S/cm) than random nanofibers (P < 0.05). Results of in vitro cell studies indicate that aligned PLGA–PHT nanofibers have a significant influence on the adhesion and proliferation of Schwann cells and could be potentially used as scaffold for neural regeneration.     

Antioxidant and antiglycemic potential of Peltophorum pterocarpum plant parts

The leaf and bark extracts of Peltophorum pterocarpum were evaluated for their DPPH, ABTS, and galvinoxyl radicals scavenging activity, phenolic content, α-glucosidase, α-amylase and aldose reductase inhibition, and advanced glycation end-products formation inhibition activities. These extracts showed a far more significant antiglycemic activity compared to the commercial carbohydrate inhibitor, acarbose. The active compound in P. pterocarpum leaf extracts was identified to be quercetin-3-O-β-d-galactopyranoside. Our findings provide a strong rationale for further in vivo studies and to establish P. pterocarpum’s capability as an antiglycemic agent.     

Preparation and Characterisation of Pelletised Glass Electrolytes for Fuel Cells

This paper reports on the preparation and characterisation of pelletised glass electrolytes that were fabricated with a proton conducting glass derived from a sol–gel technique, and several kinds of binders. The electrolytes, consisting of a glass powder that had been pulverised by planetary ball milling and mixed with an orthophosphoric acid binder, gave rise to a maximum proton conductivity of 1.3 × 10^–2 S cm^–1 measured at 80 °C and 80% relative humidity. The pore diameter of the PGE was in this case ∼2 nm. The hydrogen gas permeability was analysed as a function of the temperature and was found to be on the order of 10^–10 mol cm^–1 s^–1 Pa^–1 at 100 °C. Current–voltage measurements were carried out at room temperature using the PGE under H₂ and O₂ flow. Power densities were obtained from the I–V curves during fuel cell operation at 80 °C and 100% R.H.     

Composition and Characteristics of Cleome icosandra L. Seed Oil

Cleome icosandra grows wild in abundance all over India. The seeds contain 26% of oil. The iodine value of the fresh and the stored oils was found to be 125–126 and saponification value as 205. The oil contains only a small amount of saturated acids (21–22%), viz. myristic (1–1.2%), palmitic (13–14%) and stearic [6–7%] and high amounts of unsaturated acids, viz. oleic (12–14%), linoleic (65–66%). Due to the high linoleic content the oil polymerises during storage. The degree of polymerisation is higher with the oil extracted from stored seeds which was kept over a period of three months than the oil obtained from fresh seeds under identical conditions. The short crop period, ease of collection of seeds from forest areas and the desirable tendency of polymerisation suggest the exploitation of this oil for industrial use.