Microlens Parallax Asymmetries Toward the LMC

If the microlensing events now being detected toward the Large Magellanic Cloud (LMC) are due to lenses in the Milky Way halo, then the events should typically have asymmetries of order 1% due to parallax from the reflex motion of the Earth. By contrast, if the lenses are in the LMC, the parallax effects should be negligible. A ground-based search for such parallax asymmetries would therefore clarify the location of the lenses. A modest effort (2 hours per night on a 1 m telescope) could measure 15 parallax asymmetries over 5 years and so marginally discriminate between the halo and the LMC as the source of the lenses. A dedicated 1 m telescope would approximately double the number of measurements and would therefore clearly distinguish between the alternatives. However, compared to satellite parallaxes, the information extracted from ground-based parallaxes is substantially less useful for understanding the nature of the halo lenses (if that is what they are). The backgrounds of asymmetries due to binary-source and binary-lens events are estimated to be approximately 7% and 12% respectively. These complicate the interpretation of detected parallax asymmetries, but not critically.Comment: Submitted to ApJ, 17 pages, including 2 embedded figure

Climate change and biodiversity; impacts, vulnerability and mitigation in Indian perspective : A review

As per the nature of law, changes are bound to be happening in the system if any component of the system gets altered by any means. Change of climate and subsequently loss of biodiversity threatens the existence of human being. The loss of biodiversity, which has been happening worldwide, poses a serious threat to the anthro-pological system. An investigation of the current trend and future scenario shows that this loss is likely to continue in the foreseeable times. India has a huge variety of biodiversity and in the last few decades, its biodiversity has come under threat from climate change which accelerated by the anthropogenic activities of various sources of pollution. The review shows that climate change is a serious environmental challenge that undermines the determination for sustainable development. Climate change has become the most crucial environmental concern of the decade. Much attention is rightly focused on reducing carbon emissions and greenhouse gases from industrial, energy and transport sector through reduction in fuel consumption and use of renewable/green energy. However, as countries are looking for mitigation and adaptation processes, protection of natural habitats is a key factor of climate change strategies. Strengthened support for protected areas and more sustainable resource management can contribute to strategies as well as for protection of the biological resources and ecosystem. Climate change is developing as one of the greatest threats to biodiversity, increasing pressures on genetic resources, species and populations. Biodiver-sity conservation and sustainable development are the possible ways to curtail the impact of climate change. Although, adequate efforts have been made worldwide to tackle the environmental challenges, the adverse effects of climate change are still accelerating and the rate of loss of biodiversity is continuing globally

Microlens Parallaxes with SIRTF

The Space Infrared Telescope Facility (SIRTF) will drift away from the Earth at about 0.1 AU/yr. Microlensing events will therefore have different characteristics as seen from the satellite and the Earth. From the difference, it is possible in principle to measure v-tilde, the transverse velocity of the lens projected onto the observer plane. Since v-tilde has very different values for different populations (disk, halo, Large Magellanic Cloud), such measurements could help identify the location, and hence the nature, of the lenses. I show that the method previously developed by Gould for measuring such satellite parallaxes fails completely in the case of SIRTF: it is overwhelmed by degeneracies which arise from fact that the Earth and satellite observations are in different band passes. I develop a new method which allows for observations in different band passes and yet removes all degeneracies. The method combines a purely ground-based measurement of the "parallax asymmetry" with a measurement of the delay between the time the event peaks at the Earth and satellite. In effect, the parallax asymmetry determines the component of v-tilde in the Earth-Sun direction, while the delay time measures the component of v-tilde in the direction of the Earth's orbit.Comment: 21 pages plus 3 figure

Monovalent ions modulate the flux through multiple folding pathways of an RNA pseudoknot

The functions of RNA pseudoknots (PKs), which are minimal tertiary structural motifs and an integral part of several ribozymes and ribonucleoprotein complexes, are determined by their structure, stability and dynamics. Therefore, it is important to elucidate the general principles governing their thermodynamics/folding mechanisms. Here, we combine experiments and simulations to examine the folding/unfolding pathways of the VPK pseudoknot, a variant of the Mouse Mammary Tumor Virus (MMTV) PK involved in ribosomal frameshifting. Fluorescent nucleotide analogs (2-aminopurine and pyrrolocytidine) placed at different stem/loop positions in the PK, and laser temperature-jump approaches serve as local probes allowing us to monitor the order of assembly of VPK with two helices with different intrinsic stabilities. The experiments and molecular simulations show that at 50 mM KCl the dominant folding pathway populates only the more stable partially folded hairpin. As the salt concentration is increased a parallel folding pathway emerges, involving the less stable hairpin structure as an alternate intermediate. Notably, the flux between the pathways is modulated by the ionic strength. The findings support the principle that the order of PK structure formation is determined by the relative stabilities of the hairpins, which can be altered by sequence variations or salt concentrations. Our study not only unambiguously demonstrates that PK folds by parallel pathways, but also establishes that quantitative description of RNA self-assembly requires a synergistic combination of experiments and simulations.Comment: Supporting Information include

MACHOs, White Dwarfs, and the Age of the Universe

(Abridged Abstract) A favored interpretation of recent microlensing measurements towards the Large Magellanic Cloud implies that a large fraction (i.e. 10--50%) of the mass of the galactic halo is composed of white dwarfs. We compare model white dwarf luminosity functions to the data from the observational surveys in order to determine a lower bound on the age of any substantial white dwarf halo population (and hence possibly on the age of the Universe). We compare various theoretical white dwarf luminosity functions, in which we vary hese three parameters, with the abovementioned survey results. From this comparison, we conclude that if white dwarfs do indeed constitute more than 10% of the local halo mass density, then the Universe must be at least 10 Gyr old for our most extreme allowed values of the parameters. When we use cooling curves that account for chemical fractionation and more likely values of the IMF and the bolometric correction, we find tighter limits: a white dwarf MACHO fraction of 10% (30%) requires a minimum age of 14 Gyr (15.5 Gyr). Our analysis also indicates that the halo white dwarfs almost certainly have helium-dominated atmospheres.Comment: Final version accepted for publication, straight TeX formate, 6 figs, 22 page

From Patanjali to the "gospel of sweat": yoga's remarkable transformation from a sacred movement into a thriving global market

Movements seeking to infuse markets with moral values often end up utilizing the market mechanism and support from mainstream actors to scale up, even if it comes at the cost of diluting their founding ethos. However, this process can be particularly challenging for movements that are explicitly opposed to using a market mechanism as a means of scaling up. Our analysis of yoga between 1975 and 2016 reveals how a counter-cultural movement fundamentally opposed to a capitalist market economy but seeking to grow can paradoxically become syncretic with markets. We show how, before such a movement can be commodified, it must be de-essentialized, a process that requires stripping away key aspects of its history, context, and religious commitments and transforming collective goals into individual ones. This process involves not only external entrepreneurs looking to mine the movement, but also movement leaders seeking wider enrollment of resource-rich actors to scale the movement up. We show how codes borrowed from parallel movements and templates borrowed from markets can be instrumental in driving such a movement’s transformation. Through this “extreme” case of the yoga movement, we advance understandings of how movements can become syncretic with values and practices they fundamentally oppose

Selective and sensitive detection of CO gas by In2O3 thick film gas sensors

This study aims to provide a better fundamental understanding of the gas sensing mechanism of In2O3 gas sensors. In the present work In2O3 powder has been derived by calcinations of In2S3 powder prepared by flux method. Thick film of In2O3 has been deposited utilizing a relatively simple and low cost screen printing technique and characterized by scanning electron microscopy and X-ray diffraction. In2O3 thick film exhibits much higher sensitivity to CO at 150 °C. The corresponding sensitivity is 10.2 with good selectivity, and the response and recovery times are 6 and 14 s, respectively. The results indicate that the In2O3 thick film can be used to fabricate high performance CO sensors