Estimation of Biogas Potential of the Food Waste Generated in a Hostel Mess

This research work focusses on the estimation of biogas production from the food waste collected from a hostel mess in National Institute of Technology Rourkela. Vikram Sarabhai Hall of residence being the biggest hostel in the institute generates enough food waste and has a huge biogas potential. This paper focusses on the theoretical estimation of biogas that is an initial step towards establishing a biogas plant at the backyard of the hostel. Along with the waste treatment technology available today, characterization and chemical analysis of the raw material supplied to the machine becomes exceptionally important when figuring out the design and operational parameters of the biogas plant. Thorough research both quantitative and qualitative parameters are very important prior to the establishment of any engineering model. A food waste sample was collected from the hostel mess. In order to do the qualitative analysis and characterisation of food waste, the sample was dried in hot air oven and further it was crushed using the mortar pistol to powdered form. This powdered sample was subsequently used for characterisation of the food waste. Characterisation process includes the carbohydrate estimation, protein estimation, cholesterol estimation and CHNS analysis. This research work includes an MATLAB tool that was used to theoretical estimate the methane generation if the CHNS data is known to us. Even though very few number of samples were analysed, the results are extremely valuable for the biogas plant designers

Heat Transfer Study of Porous Media with a Temperature Jump Condition

Conjugate heat transfer in a porous media is investigated with a temperature jump condition obtained from kinetic gas theory. The temperature jump appears alongside flow boundary condition when the pressure is low, and considered to be in non-continuum regime. This investigation focuses on both one-dimensional and two-dimensional porous media models. The length scale of the pores is 100 microns. The temperature is ambient, and the pressure is low enough to reach the slip-flow regime. The thermal behavior of porous media is investigated using a slot model with a gas trapped between two solid blocks. Aluminum oxide and air are considered as a baseline combination. The steady-state results show the change in the temperature jump and net heat flux as a function of Knudsen number for gas-solid systems. For unsteady cases, a change in the amplitude and phase of the heat flux is shown over the range of frequencies between 10 Hz and 10 kHz. The effects of different solid-gas combinations are also investigated. The results show that the properties of the gas has a significantly larger impact than those of the solid. Steady-state heat transfer in two-dimensional porous media is also investigated using a brick model with a rectangular cavity of 90% void fraction. The results show the effects of pressure, void fraction and solid-gas combinations on the effective thermal conductivity of the porous media model. A multi-cell structure is also investigated to study the effective thermal conductivity and edge effects when low number of cells are considered. Pressure dependent thermal properties of the gases and silica based solid non-porous materials are also investigated due to their very low thermal conductivity

Surface gravity from tidal acceleration

Surface gravity plays a pivotal role in the characterization of black holes and also in formulating the laws of black hole thermodynamics. Despite its significance, defining surface gravity in general spacetimes is a nontrivial task and thus has multiple definitions that lack equivalence in dynamical scenarios. This research endeavours to formulate the concept of surface gravity in terms of tidal acceleration, which is an alternative way of characterizing spacetime curvature. By integrating tidal acceleration from the horizon to infinity, we could retrieve surface gravity in familiar situations of Schwarzschild and Kerr spacetimes. We outline a generic procedure for calculating surface gravity and substantiate our proposal by investigating the surface gravity of stationary spacetimes and reproducing the results from the literature. Furthermore, we examine surface gravity in nonstationary spacetimes, with a focus on Vaidya spacetime as a model of evaporating black holes.Comment: 8 pages, 0 figure; Comments Welcome

Light propagation in Kerr spacetime

We explicitly solve the equations for the propagation of an electromagnetic wave up to the subleading order geometric optics expansion in the Kerr spacetime. This is done in two nontrivial steps. We first construct a set of parallel propagated null tetrad in Kerr spacetime. Two of the components of such tetrad give the propagation and polarization of an electromagnetic wave in geometric optics approximation. Then we use the parallel propagated tetrad to solve the modified trajectory equation in Kerr spacetime. We obtain the wavelength-dependent deviation of the trajectory of electromagnetic waves, which gives the mathematical description of the gravitational spin Hall effect in Kerr spacetime.Comment: 8 pages, 2 figures; Comments Welcom

Constraint on Primordial Magnetic Fields In the Light of ARCADE 2 and EDGES Observations

We study the constraints on primordial magnetic fields (PMFs) in the light of Experiment to Detect the Global Epoch of Reionization Signature (EDGES) low-band observation and Absolute Radiometer for Cosmology, Astrophysics and Diffuse Emission (ARCADE 2). In the presence of PMFs, 21 cm differential brightness temperature can modify due to the heating of the gas by decaying magnetic fields. ARCADE 2 observation detected excess radio radiation in the frequency range 3-90 GHz. Using the ARCADE 2 and EDGES observations, we find the upper constraint, at the length scale of 1 Mpc, on the primordial magnetic field $B_{\rm 1~Mpc}\lesssim 53.3$ pG for the nearly scale-invariant PMFs using 10% of observed excess radio radiation. However, taking into account the heating effects due to x-ray and VDKZ18 (Venumadhav et al. 2018), the upper constraint on the strength of the primordial magnetic fields can further be lowered to $B_{\rm 1~Mpc}\lesssim37$ pG.Comment: 7 pages, 4 figures, Heating effects due to x-ray and VDKZ18 adde

Spin optics for gravitational waves

We present geometric optics expansion in the subleading order for the circularly polarized gravitational waves on curved spacetimes. We call spin optics to the subleading order geometric optics expansion. Spin optics involves the modification of the standard eikonal function by including a specially chosen helicity dependent correction. We show that the techniques developed for the propagation of electromagnetic waves could be applied to gravitational waves, in the limit of spin optics also. However, we should account for the difference in their helicity.Comment: 11 pages, 1 figure; Minor edit

Rapid Bispecific Antibodies Based Homogeneous Immunoassay for Detection of Prostate-Specific Antigen (PSA)

Development of rapid and economical method for detection of prostate- specific antigen (PSA) in human blood. Methods: The usual procedure for the detection of prostate cancer markers in human is prostate-specific antigen (PSA) in blood (normal level ≤ 4 ng/mL) using heterogeneous immunoassay enzyme linked immunosorbent assay (ELISA). However, a rapid homogeneous immunoassay for the detection of PSA in serum, based on bispecific antibodies, is more convenient due to its speed, accuracy and obviating the need of multiple washing steps. The assay using bispecific antibody P57 (against PSA and peroxidase) and monospecific antibody B87 (against PSA) conjugated with glucose oxidase was developed in the presence of excess catalase. Similarly, in solid phase homogeneous immunoassay the monospecific antibody B87 (against PSA) and glucose oxidase were immobilized onto a solid support (plastic) and other reagents, bio-chemicals, and bispecific antibody P57 were taken in homogeneous solution. All variables, viz., glucose oxidase, peroxidase and catalase were optimized at different PSA concentrations. Results: Homogeneous immunoassay (HIA) showed linearity of PSA detection 1-10 ng/mL whereas, solid phase homogeneous immunoassay (SPHIA) showed in the range of 1-50 ng/mL suggesting SPHIA has a broader operating range, thus much better than HIA. Detection of PSA in a homogeneous solution can be completed in 90 minutes without involving any washing and incubation steps. Conclusions: Homogeneous assay is a rapid, economical method that eliminates all washing and incubation steps of conventional ELISA