A parametrisation for dissipative behaviours–the matrix case

We study linear, time-invariant dynamical systems that are dissipative with respect to a generalised power defined by a quadratic differential form. We address several cases, in an increasing order of complexity, and show how dissipative systems can be parametrised. In this process, we also establish a number of results for polynomial matrices that are of independent interest. The present article is a generalisation of our earlier work that dealt with single-input single-output dissipative systems (Pendharkar, I., and Pillai, H.K. (2004), ‘A Parametrization for Dissipative Behaviours’, Systems and Control Letters, 51, 123–132).     

Piezoelectric nanoribbons for monitoring cellular deformations

Methods for probing mechanical responses of mammalian cells to electrical excitations can improve our understanding of cellular physiology and function. The electrical response of neuronal cells to applied voltages has been studied in detail, but less is known about their mechanical response to electrical excitations. Studies using atomic force microscopes (AFMs) have shown that mammalian cells exhibit voltage-induced mechanical deflections at nanometre scales, but AFM measurements can be invasive and difficult to multiplex. Here we show that mechanical deformations of neuronal cells in response to electrical excitations can be measured using piezoelectric PbZr(x)Ti(1-)(x)O(3) (PZT) nanoribbons, and we find that cells deflect by 1?nm when 120?mV is applied to the cell membrane. The measured cellular forces agree with a theoretical model in which depolarization caused by an applied voltage induces a change in membrane tension, which results in the cell altering its radius so that the pressure remains constant across the membrane. We also transfer arrays of PZT nanoribbons onto a silicone elastomer and measure mechanical deformations on a cow lung that mimics respiration. The PZT nanoribbons offer a minimally invasive and scalable platform for electromechanical biosensing.     

Combustion synthesis of 5 and 10 mol% YO1.5 doped ThO2 powders

Nanocrystalline 5 and 10 mol% YO_1.5 doped ThO₂ powders were prepared by the combustion technique using citric acid as a fuel and nitrates as oxidants. The auto-ignition of the fuel-deficient precursors (prepared by thermal dehydration of the aqueous solutions containing metal nitrates and citric acid in required molar ratio) directly resulted in the well crystalline powders of the desired solid solutions along with traces of carbonaceous material. The as-prepared and calcined powders were characterized by X-ray diffraction (XRD), high-temperature XRD and by their sinterability. The YO_1.5 doped ThO₂ powders when cold-pressed and sintered at 1300 °C for 2 h resulted in ?95% of their theoretical densities with nanograin microstructure.     

In Vitro Study of Hydroxyapatite Coatings on Fibrin Functionalized/Pristine Graphene Oxide for Bone Grafting

Fibrin functionalized graphene oxide (FGO) and graphene oxide (GO) were used as nucleation sites for the growth of hydroxyapatite (HA). The growth of HA on GO/FGO was done by wet precipitation method, and they were characterized for their physicochemical properties. Cytotoxicity was confirmed by reactive oxygen species assay and cell viability assay; alkaline phosphatase assay, alizarin red test, and protein expression studies showed that FGHA was an excellent composite for osteoblast cell growth and maturation. Alamar blue assay was used to study the enzymatically degraded cytocompatibility of enzymatically degraded components. Results proved that FGHA might be tried as an osteoinductive material, in orthopedic defects.     

CO2 emissions mitigation potential of solar home systems under clean development mechanism in India

The Government of India has taken several initiatives for promotion of solar energy systems in the country during the last two decades. A variety of policy measures have been adopted which include provision of financial and fiscal incentives to the potential users of solar energy systems however, only 0.4 million solar home systems (SHSs) have been installed so far that is far below their respective potential. One of the major barriers is the high costs of investments in these systems. The clean development mechanism (CDM) of the Kyoto Protocol provides industrialized (Annex-I) countries with an incentive to invest in emission reduction projects in developing (non-Annex-I) countries to achieve a reduction in carbon dioxide (CO₂) emissions at lowest cost that also promotes sustainable development in the host country. SHSs could be of interest under the CDM because they directly displace greenhouse gas (GHG) emissions while contributing to sustainable rural development, if developed correctly. In this study an attempt has been made to estimate the CO₂ mitigation potential of SHSs under CDM in India.     

Demand projections of petroleum products and natural gas in India

Indian economy has moved into a dynamic phase. It is necessary to see how energy demand will grow in this phase. In this paper, econometric models are developed for the various petroleum products separately with the aim of capturing variables that are specific to the individual fuel. This study projects the demand of fuels up to 2011–2012, end period for the 11th Five Year Plan, under two scenarios of annual gross domestic product (GDP) growth of 6% and 8%. The demand of petroleum products for the year 2011–2012 is estimated to be 147 and 162 million tons in the business as usual scenario of 6% and optimistic scenario of 8% GDP growth, respectively. Similarly, the demand of natural gas for the year 2011–2012 has been estimated to be 46 and 49 billion cubic meters for 6% and 8% growth, respectively. The projections suggest the level of preparedness that will be required from the oil and gas sector to enable India achieve the GDP growth target that it aims to.     

Enhanced piezoelectricity and stretchability in energy harvesting devices fabricated from buckled PZT ribbons

The development of a method for integrating highly efficient energy conversion materials onto soft, biocompatible substrates could yield breakthroughs in implantable or wearable energy harvesting systems. Of particular interest are devices which can conform to irregular, curved surfaces, and operate in vital environments that may involve both flexing and stretching modes. Previous studies have shown significant advances in the integration of highly efficient piezoelectric nanocrystals on flexible and bendable substrates. Yet, such inorganic nanomaterials are mechanically incompatible with the extreme elasticity of elastomeric substrates. Here, we present a novel strategy for overcoming these limitations, by generating wavy piezoelectric ribbons on silicone rubber. Our results show that the amplitudes in the waves accommodate order-of-magnitude increases in maximum tensile strain without fracture. Further, local probing of the buckled ribbons reveals an enhancement in the piezoelectric effect of up to 70%, thus representing the highest reported piezoelectric response on a stretchable medium. These results allow for the integration of energy conversion devices which operate in stretching mode via reversible deformations in the wavy/buckled ribbons.     

Synthesis and photoluminescence properties of Eu<Superscript>3+</Superscript>-activated SrZnO<Subscript>2</Subscript>

Synthesis, X-ray diffraction, and photoluminescence (PL) investigations of SrZnO₂ doped with Eu³⁺ were carried out in order to characterize the material. The emission spectra showed a broad band emission at 525 nm attributed to oxygen defect centers in the host matrix, along with peaks corresponding to the ⁵D₀ → ⁷F _j (j = 1, 2) transitions of Eu ion under 250 nm excitation. PL decay time studies were done to confirm these investigations. Time-resolved emission spectrometric (TRES) study was carried out to extract the emission spectra of the Eu ion which was buried under the broad band emission. After giving suitable delay times and by choosing a proper time gate, transitions due to ⁵D₀ → ⁷F _j (j = 0, 1, 2, 3, and 4) could be observed. Judd–Ofelt intensity parameters and other radiative properties for the system were evaluated from this emission spectrum and decay time data by adopting standard procedure. The color coordinates of the system were also evaluated and plotted on a standard CIE index diagram. The observations showed that the SrZnO₂:Eu³⁺material has near white light emission (also considering the emission from host) whereas, the extracted emission spectrum due to only Eu ions has a near red emission.     

RHEOLOGICAL PROPERTIES OF BOMBAY HIGH CRUDE OIL IN RELATION TO ITS n-ALKANE COMPONENTS

ABSTRACT

Bombay High crude oil is very waxy in nature and has a high pour point (30^°C), The wax present in it largely consists of solid n-alkanes. Changes in the rheological properties of the crude oil after removal of n-alkanes by urea adduction have been determined. Influence of the concentration of n-alkane components on the rheological properties of non adductable components of crude oil have also been studied.     

LOW TEMPERATURE FLOW CHARACTERISTICS OF SOME WAXY CRUDE OILS IN RELATION TO THEIR COMPOSITION : PART I WITH AND WITHOUT POUR POINT DEPRESSANT ADDITIVES

ABSTRACT

The yield stress, plastic viscosity and apparent viscosity and the dependence of the latter on the shear rate have been studied at different temperatures below pour point of Lingala (Krishna-Godavari basin, Eastern coast), Duliajan (Eastern region of Assam), Rava (Godavari basin) and Bombay-High (off-shore western region) indigenous crude oils

Four different commercial pour point depressant additives have been used to study their effects on the pour point, yield stress and plastic viscosity

From this study it has been found that wax concentration and its composition are primarily responsible for the variation in the pour point, and crude base composition has a small effect. However, the response of the pour point depressant additive in effecting the change in the pour point is primarily governed by the liquid matrix. As the temperature is lowered both the yield stress and plastic viscosity increase in case of each crude oil. However, the magnitude is dependent on the nature of the crude oil. With pour point depressant additives, the yield stress and plastic viscosity are decreased and this decrease is a function of nature of the liquid matrix of the crude oil and concentration of the additive