Microscopic Forces and Flows due to Temperature Gradients

Nano-scale fluid flow is unlike transport on the macro-scale. Pressure gradients typically dominate effects on a large scale while thermal gradients contribute negligibly to the motion of fluid. The situation entirely reverses on the nano-scale. At a microscopic level, flows induced by thermal gradients are caused by forces that act on atoms or molecules near an interface. These thermo-osmotic forces cannot, at present, be derived analytically or measured experimentally. Clearly, it would be useful to calculate these forces via molecular simulations, but direct approaches fail because in the steady-state, the average force per particle vanishes, as the thermo-osmotic force is balanced by a gradient in shear stress. In our journey to indirectly calculate the osmotic force, we met another unknown in the field of molecular theory at interfaces: the microscopic pressure tensor. The latter is an open problem since the microscopic pressure near an interface is not uniquely defined. Using local thermodynamics theories, we relate the thermo-osmotic force to the gradient of the microscopic pressure tensor. Yet, because the pressure is not uniquely defined, we arrive at multiple answers for the thermo-osmotic force, where at most one can be correct. To resolve the latter puzzle, we develop a direct, non-equilibrium simulation protocol to measure the thermo-osmotic force, whereby a thermal gradient is imposed and the osmotic force is measured by eliminating the shear force. Surprisingly, we find  that the osmotic force cannot be derived from the gradient of well-known microscopic pressure expressions. We, therefore, derive a thermodynamic expression that gets close. In this work, we report the first, direct calculation of the thermo-osmotic force while simultaneously showing that standard microscopic pressure expressions fail to predict pressure gradients.Raymond and Beverly Sackler Fund for the Physics of Medicin

Load-Aware Modeling and Analysis of Heterogeneous Cellular Networks

Random spatial models are attractive for modeling heterogeneous cellular networks (HCNs) due to their realism, tractability, and scalability. A major limitation of such models to date in the context of HCNs is the neglect of network traffic and load: all base stations (BSs) have typically been assumed to always be transmitting. Small cells in particular will have a lighter load than macrocells, and so their contribution to the network interference may be significantly overstated in a fully loaded model. This paper incorporates a flexible notion of BS load by introducing a new idea of conditionally thinning the interference field. For a K-tier HCN where BSs across tiers differ in terms of transmit power, supported data rate, deployment density, and now load, we derive the coverage probability for a typical mobile, which connects to the strongest BS signal. Conditioned on this connection, the interfering BSs of the $i^{th}$ tier are assumed to transmit independently with probability $p_i$, which models the load. Assuming - reasonably - that smaller cells are more lightly loaded than macrocells, the analysis shows that adding such access points to the network always increases the coverage probability. We also observe that fully loaded models are quite pessimistic in terms of coverage.Comment: to appear, IEEE Transactions on Wireless Communication

Resistance of Some Timbers of Andaman Islands Against Marine Borer Attack at Five Ports of India

Six species of structural timbers grown in Andaman area have been examined for natural resistance to marine wood boring organisms at Bombay, Cochin, Goa, Visakhapatnam and Port Blair. Pterocarpus dalbergeioides(Andaman padauk), has been found to be one of the most suitable timbers comparable with teak in performance. Lagerstroemia hypoleuca(Pyinma), has shown a prolonged life and high degree of durability particularly at Bombay. Some important mechanical properties of these timbers have been compared with that of teak so that they may by considered as substitutes

Resistance of Some Timbers of Andhra Pradesh Against Marine Borer Attack at Four Ports on India

Observations on the underwater durability of thirteen species of times growth in Andhra Pradesh against marine borer attack at four ports of Naval interest are recorded. Intensity of borer attack was found to vary from port to port, maximum observed being at Port Blair, with Goa, Bombay and Visakhapatnam following in that order. Comparison of borer activity in the harbours studies with past observations has revealed that a change in eco-systems may be occurring at Visakhapatnam harbour

How does technology pathway choice influence economic viability and environmental impacts of lignocellulosic biorefineries?

Background: The need for liquid fuels in the transportation sector is increasing, and it is essential to develop industrially sustainable processes that simultaneously address the tri-fold sustainability metrics of technological feasibility, economic viability, and environmental impacts. Biorefineries based on lignocellulosic feedstocks could yield high-value products such as ethyl acetate, dodecane, ethylene, and hexane. This work focuses on assessing biochemical and biomass to electricity platforms for conversion of Banagrass and Energycane into valuable fuels and chemicals using the tri-fold sustainability metrics. Results: The production cost of various products produced from Banagrass was $1.19/kg ethanol,$1.00/kg ethyl acetate, $3.01/kg dodecane (jet fuel equivalent),$2.34/kg ethylene and $0.32/kW-h electricity. The production cost of different products using Energycane as a feedstock was$1.31/kg ethanol, $1.11/kg ethyl acetate,$3.35/kg dodecane, and $2.62/kg ethylene. The sensitivity analysis revealed that the price of the main product, feedstock cost and cost of ethanol affected the profitability the overall process. Banagrass yielded 11% higher ethanol compared to Energycane, which could be attributed to the differences in the composition of these lignocellulosic biomass sources. Acidification potential was highest when ethylene was produced at the rate of 2.56 × 10−2 and 1.71 × 10−2 kg SO2 eq. for Banagrass and Energycane, respectively. Ethanol production from Banagrass and Energycane resulted in a global warming potential of − 12.3 and − 40.0 g CO2 eq./kg ethanol. Conclusions: Utilizing hexoses and pentoses from Banagrass to produce ethyl acetate was the most economical scenario with a payback period of 11.2 years and an ROI of 8.93%, respectively. Electricity production was the most unprofitable scenario with an ROI of − 29.6% using Banagrass/Energycane as a feedstock that could be attributed to high feedstock moisture content. Producing ethylene or dodecane from either of the feedstocks was not economical. The moisture content and composition of biomasses affected overall economics of the various pathways studied. Producing ethanol and ethyl acetate from Energycane had a global warming potential of − 3.01 kg CO2 eq./kg ethyl acetate

Modeling and Analysis of K-Tier Downlink Heterogeneous Cellular Networks

Cellular networks are in a major transition from a carefully planned set of large tower-mounted base-stations (BSs) to an irregular deployment of heterogeneous infrastructure elements that often additionally includes micro, pico, and femtocells, as well as distributed antennas. In this paper, we develop a tractable, flexible, and accurate model for a downlink heterogeneous cellular network (HCN) consisting of K tiers of randomly located BSs, where each tier may differ in terms of average transmit power, supported data rate and BS density. Assuming a mobile user connects to the strongest candidate BS, the resulting Signal-to-Interference-plus-Noise-Ratio (SINR) is greater than 1 when in coverage, Rayleigh fading, we derive an expression for the probability of coverage (equivalently outage) over the entire network under both open and closed access, which assumes a strikingly simple closed-form in the high SINR regime and is accurate down to -4 dB even under weaker assumptions. For external validation, we compare against an actual LTE network (for tier 1) with the other K-1 tiers being modeled as independent Poisson Point Processes. In this case as well, our model is accurate to within 1-2 dB. We also derive the average rate achieved by a randomly located mobile and the average load on each tier of BSs. One interesting observation for interference-limited open access networks is that at a given SINR, adding more tiers and/or BSs neither increases nor decreases the probability of coverage or outage when all the tiers have the same target-SINR.Comment: IEEE Journal on Selected Areas in Communications, vol. 30, no. 3, pp. 550 - 560, Apr. 201

Anti-Inflammatory Activity of Calotropis gigantea and Tridax procumbens on Carrageenin-Induced Paw Edema in Rats

The anti-inflammatory activities of extract of Calotropis gigantea R.Br. and Tridax procumbens Linn., were assessed on carrageenin-induced paw edema along with standard drug, Ibuprofen. The Ibuprofen significantly reduced paw edema at the dose of 200mg/Kg bw orally. The oral administration equi-effective dose (ED50) of C. gigantea (600mg/Kg bw) and T. procumbens (400 mg/Kg bw) individually revealed about 20-35% more activity than the one rendered by administration of 50mg/Kg bw of Ibuprofen. The effect of C. gigantea and T. procumbens along with various dose regimen of Ibuprofen showed greater anti-inflammatory activities than the Ibuprofen alone