Mass function of haloes: scale invariant models

Press-Schechter theory gives a simple, approximate functional form of the mass function of dark matter haloes. Sheth and Tormen (ST) refined this mass function to give an improved analytical fit to results of N-body simulations. These forms of the halo mass function are universal (independent of cosmology and power spectrum) when scaled in suitable variables. Using large suites of LCDM N-body simulations, studies in the last few years have shown that this universality is only approximate. We explore whether some of the deviations from universality can be attributed to the power spectrum by computing the mass function in N-body simulations of various scale-free models in an Einstein-de Sitter cosmology. This choice of cosmology does not introduce any scale into the problem. These models have the advantage of being self-similar, hence stringent checks can be imposed while running these simulations. This set of numerical experiments is designed to isolate any power spectrum dependent departures from universality of mass functions. We show explicitly that the best fit ST parameters have a clear dependence on power spectrum. Our results also indicate that an improved analytical theory with more parameters is required in order to provide better fits to the mass function.Comment: 8 pages, four figure

Evolution of the AGN UV luminosity function from redshift 7.5

Determinations of the UV luminosity function of AGN at high redshifts are important for constraining the AGN contribution to reionization and understanding the growth of supermassive black holes. Recent inferences of the luminosity function suffer from inconsistencies arising from inhomogeneous selection and analysis of AGN data. We address this problem by constructing a sample of more than 80,000 colour-selected AGN from redshift z=0 to 7.5. While this sample is composed of multiple data sets with spectroscopic redshifts and completeness estimates, we homogenise these data sets to identical cosmologies, intrinsic AGN spectra, and magnitude systems. Using this sample, we derive the AGN UV luminosity function from redshift z=0 to 7.5. The luminosity function has a double power law form at all redshifts. The break magnitude $M_*$ of the AGN luminosity function shows a steep brightening from $M_*\sim -24$ at z=0.7 to $M_*\sim -29$ at z=6. The faint-end slope $\beta$ significantly steepens from $-1.7$ at $z<2.2$ to $-2.4$ at $z\simeq 6$. In spite of this steepening, the contribution of AGN to the hydrogen photoionization rate at $z\sim 6$ is subdominant (< 3%), although it can be non-negligible (~10%) if these luminosity functions hold down to $M_{1450}=-18$. Under reasonable assumptions, AGN can reionize HeII by redshift z=2.9. At low redshifts (z<0.5), AGN can produce about half of the hydrogen photoionization rate inferred from the statistics of HI absorption lines in the IGM. Our global analysis of the luminosity function also reveals important systematic errors in the data, particularly at z=2.2--3.5, which need to be addressed and incorporated in the AGN selection function in future in order to improve our results. We make various fitting functions, luminosity function analysis codes, and homogenised AGN data publicly available.Comment: 30 pages, 15 figures; accepted in MNRAS; code, data, and various fits at https://github.com/gkulkarni/QL

Carbon Nanoelectronic Heterodyne Sensors : A New Paradigm for Chemical and Biological Detection.

In 1959, in his famous talk ‘There is plenty of room at the bottom’, physicist Richard Feynman had envisaged a new era of science where one could build electronic systems which would sense and interact with a world only a few atoms in size. To build such systems we not only need new materials but also new transduction strategies. The hunt for new materials has led us back to carbon, a material known since antiquity. Carbon nanotube and graphene-two allotropes of carbon, possess structural, electronic, optical and mechanical properties perfect for building fast, robust and sensitive nano-systems. However, the available sensing technologies are still incapable of high fidelity detection critical for studying nanoscale events in complex environments like ligand-receptor binding, molecular adsorption/desorption, π-π stacking, catalysis, etc. In this thesis, I first introduce a fundamentally new nanoelectronic sensing technology based on heterodyne mixing to investigate the interaction between charge density fluctuations in a nanoelectronic sensor caused by oscillating dipole moment of molecule and an alternating current drive voltage which excites it. By detecting molecular dipole instead of associated charge, we address the limitations of conventional charge-detection based nanoelectronic sensing techniques. In particular, using a carbon nanotube heterodyne platform, I demonstrate for the first time, biological detection in high ionic background solutions where conventional charge-detection based techniques fail due to fundamental Debye screening effect. Next, we report the first graphene nanoelectronic heterodyne vapor sensors which can detect a plethora of vapor molecules with high speed (~ 0.1 second) and high sensitivity (< 1 part per billion) simultaneously; recording orders-of-magnitude improvement over existing nanoelectronic sensors which suffer from fundamental speed-sensitivity tradeoff issue. Finally, we use heterodyne detection as a probe to quantify the fundamental non-covalent binding interaction between small molecules and graphene by analyzing the real-time molecular desorption kinetics. More importantly, we demonstrate for the first time, electrical tuning of molecule-graphene binding kinetics by electrostatic control of graphene work function signifying the ability to tailor chemical interactions on-demand. Our work not only lays a foundation for next-generation of rapid and sensitive nanoelectronic detectors, but also provides an insight into the fundamental molecule-nanomaterial interaction.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111436/1/girishsk_1.pd

Conceptual study of Rasa Sindoora in management of Shotha Roga w.s.r. to Brihat-Trayi

“Rogamadou Parikshet Tatoanataram Aushadham” Physician should first of all diagnose the disease then he should select proper medicine. Diagnosis is not complete without elucidation of all factors related to disease. For the diagnosis of the disease Nidaan Panchaka is very useful entity. Except Chikitsa, Nidaan Panchaka includes all the necessary information related to disease. Here we consider the Nidaan Panchaka of Shotha according to Brihat Trayi and its management with Rasa Sindoor one of the unique preparation in Rasashastra

Chemical enrichment of Damped Lyman Alpha systems as a direct constraint on Population III star formation

Damped Ly-alpha absorbers (DLAs) can be used to measure gas-phase metallicities at large cosmological lookback times with high precision. Relative abundances can still be measured accurately deep into the reionization epoch (z > 6) using transitions redward of Ly-alpha. Here we study chemical evolution of DLAs using a constrained model for evolution of galaxies and IGM to determine the degree to which DLA abundance measurements can probe Population III enrichment. We find that if the critical metallicity of Population III to II transition is < 10^-4 Zsun, the cosmic Population III SFR is zero for z<8. Nevertheless, at high redshift (z ~ 6) Population III chemical signatures are retained in low-mass galaxies (halo mass < 10^9 Msun). This is because photoionization feedback suppresses star formation in these galaxies until relatively low redshift (z ~ 10), and the chemical record of early Population III star formation is retained. We model DLAs as these galaxies by assigning to them a mass-dependent H I absorption cross section and predict distribution of DLA abundance ratios. We find that these distributions are anchored towards abundance ratios set by Population II yields, but exhibit a tail that depends on the Population III IMF for z > 5. Thus, a sample of DLA abundance measurements at high redshift holds the promise to constrain Population III IMF. A sample of just 10 DLAs with relative abundances measured to an accuracy of 0.1 dex is sufficient to constrain the Population III IMF at 4-sigma. These constraints may prove stronger than other probes such as metal-poor stars and individual DLAs. Our results provide a global picture of the cosmic thermal, ionization, and chemical evolution, and can rule out certain Population III scenarios.Comment: 21 pages, 12 figures; this version accepted in Ap