Rapid vertical mixing rates in deep waters of the Andaman Basin

The Andaman Basin is an enclosed region in the northeastern Indian Ocean with its deep water below approximately 1800 m almost isolated with respect to horizontal ventilation by the Andaman-Nicobar Islands separating it from the Bay of Bengal. The physical and chemical properties including radiocarbon ((14)C) measured at two stations of the Andaman Basin show negligible variation with depth in the waters below 1300 m, indicating a well-mixed water mass. This study attempts to derive the mixing rates for deep waters of the Andaman Basin. Model calculations based on (14)C profile measurements indicate rapid vertical mixing (vertical advection velocity, w>200 m year(-1)) in waters deeper than 1800 m of the basin. For a basin with deep water thickness of 1000 m below 1800 m, deduced mixing rate of >200 m year(-1) translates to mixing time of <5 years. As shown for other regions, the possible mechanism responsible for such high vertical mixing rates could be the internal waves generated from tidal currents flowing through rough topography. In addition, Andaman Basin is underlain with a young crust and is known for its high heat flow, which also could contribute to the high vertical mixing.     

Selective Zinc(II)‐Ion Fluorescence Sensing by a Functionalized Mesoporous Material Covalently Grafted with a Fluorescent Chromophore and Consequent Biological Applications

A highly ordered 2D‐hexagonal mesoporous silica material is functionalized with 3‐aminopropyltriethoxysilane. This organically modified mesoporous material is grafted with a dialdehyde fluorescent chromophore, 4‐methyl‐2,6‐diformyl phenol. Powder X‐ray diffraction, transmission electron microscopy, N₂ sorption, Fourier transform infrared spectroscopy, and UV‐visible absorption and emission have been employed to characterize the material. This material shows excellent selective Zn²⁺ sensing, which is due to the fluorophore moiety present at its surface. Fluorescence measurements reveal that the emission intensity of the Zn²⁺‐bound mesoporous material increases significantly upon addition of various concentrations of Zn²⁺, while the introduction of other biologically relevant (Ca²⁺, Mg²⁺, Na⁺, and K⁺) and environmentally hazardous transition‐metal ions results in either unchanged or weakened intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Zn²⁺, evident from the large binding constant value (0.87 × 10⁴ M ^?1). Thus, this functionalized mesoporous material grafted with the fluorescent chromophore could monitor or recognize Zn²⁺ from a mixture of ions that contains Zn²⁺ even in trace amounts and can be considered as a selective fluorescent probe. We have examined the application of this mesoporous zinc(II) sensor to cultured living cells (A375 human melanoma and human cervical cancer cell, HeLa) by fluorescence microscopy.     

Temporal response of biochemical and biological sensors with bimodal surface adsorption from a finite sample

Microsystem Technologies - The importance of adsorption-based biochemical/biological sensors in biochemistry and biophysics is paramount. Their temporal response gives information about the...     

Effect of pre-mastication on dispersion of nanoclay in presence of carbon black in an inner liner compound: Studies on physicomechanical and functional properties

The present study demonstrates the use of “pre-mastication” technique for getting higher dispersion of organoclay, Cloisite 15A, in an inner liner compound based on 70:30 bromobutyl and natural rubber blend, in presence of higher concentration of carbon black (60 phr) for the improvement of functional properties like fatigue cut growth and air permeability resistance. Studies have showed that the organoclay was almost equally distributed within the blend both in absence as well as in presence of carbon black. The vulcanization curve showed a marked increase in cure acceleration as well as a significant rise in the maximum torque value because of higher crosslinking aided by the participation of the quaternary amine present in Cloisite 15A; however, in the carbon black loaded compound, the cure acceleration was not so pronounced because of engaging interaction between amine and functional groups of carbon black. The microscopic study revealed a good dispersion of Cloisite 15A within the elastomer blend- in presence of carbon black. The anisotropic platelets of Cloisite 15A and carbon black particles jointly formed “nano units”, which occluded a portion of elastomer segments vis-a-vis partial intercalation within the clay gallery. Such a reinforcing model was instrumental in improving the physicomechanical and functional properties under static and dynamic conditions. The organoclay displayed a much-improved properties at 2 and 4 phr doses in presence of 60 phr carbon black because of formation of enough “nano units” while deterioration was observed at 6 phr dose due to clay aggregation. Based on the results obtained on functional properties it was concluded that the 4 phr of organoclay compounded in “pre-mastication” mode delivered the best improvement and thus it was recommended for future up-scaling study.     

Understanding the influence of anti-reversion agent and metal oxide dose on natural rubber–carbon black system

Sulfidic linkages that are formed during the vulcanization process of natural rubber (NR) are unstable at a higher temperature and can be reversed into conjugated diene. To overcome such issue and to build a compound that is hostile to inversion and with increasing service life, anti-reversion agent (ARA), for example, N,N′-4,4′-diphenylmethyene bismaleimide (BMDM), is added into the formulation. This work explains the conjugation reaction mechanism of conjugated diene and BMDM by means of gas chromatography–mass spectrometry and Fourier transform infrared spectroscopy. The first phase of this study is associated with the change in ARA dosage keeping ZnO dosage the same. It is observed that 5 phr of BMDM and 2 phr ZnO combination (ARA4) shows lowest reversion at 160°C. The modulus value at 300% elongation increased 12% by the incorporation of BMDM as compared to the compound of no BMDM (ARA1). The second part is all about keeping BMDM dosage the same at 5 phr level and varying ZnO phr by 3, 4, and 5. From the overall results, it is observed that at a suitable dosage of BMDM and ZnO (5 phr BMDM and 3 phr ZnO combination [ARA5]), least reversion can be achieved and vulcanizates containing optimized BMDM and ZnO show better retention properties after aerobic aging as compared to ARA1.     

Design and of analysis of SPDT Ohmic RF MEMS switch

Microsystem Technologies - This paper reports on the simulation and analysis of Ohmic SPDT (single pole double throw) switch for telecommunication application. A comparative study is performed by...     

Thermal simulation of machining of alumina with wire electrical discharge machining process using assisting electrode

Journal of Mechanical Science and Technology - Electrical discharge machining or Wire electrical discharge machining have proven to be an alternate mean for machining nonconducting materials to a...     

Fractional dynamical model for the generation of ECG like signals from filtered coupled Van-der Pol oscillators

In this paper, an incommensurate fractional order (FO) model has been proposed to generate ECG like waveforms. Earlier investigation of ECG like waveform generation is based on two identical Van-der Pol (VdP) family of oscillators, which are coupled by time delays and gains. In this paper, we suitably modify the three state equations corresponding to the nonlinear cross-product of states, time delay coupling of the two oscillators and low-pass filtering, using the concept of fractional derivatives. Our results show that a wide variety of ECG like waveforms can be simulated from the proposed generalized models, characterizing heart conditions under different physiological conditions. Such generalization of the modelling of ECG waveforms may be useful to understand the physiological process behind ECG signal generation in normal and abnormal heart conditions. Along with the proposed FO models, an optimization based approach is also presented to estimate the VdP oscillator parameters for representing a realistic ECG like signal.     

PMaude: Rewrite-based Specification Language for Probabilistic Object Systems

We introduce a rewrite-based specification language for modelling probabilistic concurrent and distributed systems. The language, based on PMaude, has both a rigorous formal basis and the characteristics of a high-level rule-based programming language. Furthermore, we provide tool support for performing discrete-event simulations of models written in PMaude, and for statistically analyzing various quantitative aspects of such models based on the samples that are generated through discrete-event simulation. Because distributed and concurrent communication protocols can be modelled using actors (concurrent objects with asynchronous message passing), we provide an actor PMaude module. The module aids writing specifications in a probabilistic actor formalism. This allows us to easily write specifications that are purely probabilistic – and not just non-deterministic. The absence of such (un-quantified) non-determinism in a probabilistic system is necessary for a form of statistical analysis that we also discuss. Specifically, we introduce a query language called Quantitative Temporal Expressions (or QuaTEx in short), to query various quantitative aspects of a probabilistic model. We also describe a statistical technique to evaluate QuaTEx expressions for a probabilistic model.     

Fast deterministic broadcast and gossiping algorithms for mobile ad hoc networks

We present a mobility resilient deterministic broadcast algorithm with worst-case time complexity of O(nlogn)$O(nlogn)$ for ad hoc networks where the nodes possess collision detection capabilities; n$n$ is the total number of nodes in the network. The algorithm is based on a breadth-first traversal of the network and allows multiple simultaneous transmissions by the nodes. The idea of this broadcast algorithm is then extended to develop a mobility resilient deterministic gossiping algorithm having O(Dnlogn)$O(Dnlogn)$ worst-case run time (D$D$ is the diameter of the network graph), which is an improvement over the existing algorithms. Simulation results show that on an average, the time for completing the broadcast or gossiping is significantly lower than the theoretical worst-case time requirement.