A history of the Lonar crater, India: An overview

The origin of the circular structure at Lonar, India, described variously as cauldron, pit, hollow, depression, and crater, has been a controversial subject since the early nineteenth century. A history of its origin and other aspects from 1823 to 1990 are overviewed. The structure in the Deccan Trap Basalt is nearly circular with a breach in the northeast, 1830 m in diameter, 150 m deep, with a saline lake in the crater floor. Over the years, the origin of the Lonar structure has risen from volcanism, subsidence, and cryptovolcanism to an authentic meteorite impact crater. Lonar is unique because it is probably the only terrestrial crater in basalt and is the closest analog with the Moon's craters. Some unresolved questions are suggested. The proposal is made that the young Lonar impact crater, which is less than 50,000 years old, should be considered as the best crater laboratory analogous to those of the Moon, be treated as a global monument, and preserved for scientists to comprehend more about the mysteries of nature and impact cratering, which is now emerging as a fundamental ubiquitous geological process in the evolution of the planets

General relativistic treatment of LISA optical links

LISA is a joint space mission of the NASA and the ESA for detecting low frequency gravitational waves in the band $10^{-5} - 1$ Hz. In order to attain the requisite sensitivity for LISA, the laser frequency noise must be suppressed below the other secondary noises such as the optical path noise, acceleration noise etc. This is achieved by combining time-delayed data for which precise knowledge of time-delays is required. The gravitational field, mainly that of the Sun and the motion of LISA affect the time-delays and the optical links. Further, the effect of the gravitational field of the Earth on the orbits of spacecraft is included. This leads to additional flexing over and above that of the Sun. We have written a numerical code which computes the optical links, that is, the time-delays with great accuracy $\sim 10^{-2}$ metres - more than what is required for time delay interferometry (TDI) - for most of the orbit and with sufficient accuracy within $\sim 10$ metres for an integrated time window of about six days, when one of the arms tends to be tangent to the orbit. Our analysis of the optical links is fully general relativistic and the numerical code takes into account effects such as the Sagnac, Shapiro delay, etc.. We show that with the deemed parameters in the design of LISA, there are symmetries inherent in the configuration of LISA and in the physics, which may be used effectively to suppress the residual laser noise in the modified first generation TDI. We demonstrate our results for some important TDI variables

Optimising the directional sensitivity of LISA

It was shown in a previous work that the data combinations canceling laser frequency noise constitute a module - the module of syzygies. The cancellation of laser frequency noise is crucial for obtaining the requisite sensitivity for LISA. In this work we show how the sensitivity of LISA can be optimised for a monochromatic source - a compact binary - whose direction is known, by using appropriate data combinations in the module. A stationary source in the barycentric frame appears to move in the LISA frame and our strategy consists of "coherently tracking" the source by appropriately "switching" the data combinations so that they remain optimal at all times. Assuming that the polarisation of the source is not known, we average the signal over the polarisations. We find that the best statistic is the `network' statistic, in which case LISA can be construed of as two independent detectors. We compare our results with the Michelson combination, which has been used for obtaining the standard sensitivity curve for LISA, and with the observable obtained by optimally switching the three Michelson combinations. We find that for sources lying in the ecliptic plane the improvement in SNR increases from 34% at low frequencies to nearly 90% at around 20 mHz. Finally we present the signal-to-noise ratios for some known binaries in our galaxy. We also show that, if at low frequencies SNRs of both polarisations can be measured, the inclination angle of the plane of the orbit of the binary can be estimated.Comment: 16 pages, 8 figures, submitted to Phys Rev

Experimental evaluation of critical heat flux in downward-facing boiling on flat plate relevant to in-vessel retention in Indian PHWRs

Retention of corium inside the CV and cool it by calandria vault water is essential to mitigate severe accidents in PHWRs. The thermal failure of CV can be prevented by effective decay heat removal on the outer surface of CV using vault water, which depends on the heat transfer behaviour from the outer surface of CV to the vault water. Determination of limiting heat removal capability of vault water through outer surface of calandria vessel is very important. Since, the calandria vessel has a very large diameter and length, the bottom most part of the calandria vessel almost behaves as a flat surface with downward natural convection heat transfer. In order to estimate critical heat flux (CHF) in this configuration with local boiling, experiments need to be carried out on a downward facing flat plate simulating the bottom portion of PHWR calandria vessel. Studies on critical heat flux in downward-facing boiling on flat plate is very limited in literature. Limited experiments on CHF on curved surfaces have been conducted in the past owing to its importance for in vessel retention in PWRs. Since CHF depends on the geometry and material of construction, operating parameters, the results of above experiments cannot be extrapolated to PHWRs. In order to estimate limiting heat removal capability for PHWR configuration with local boiling on outer surface of CV, experiments were carried out on downward facing flat plate and estimated the CHF of downward facing flat plate and compared the CHF value with other experiments performed for curved surface

Implementing a Public Private Partnership Model for Managing Urban Health in Ahmedabad

Governments in many developing countries acknowledge they are facing difficulties in their attempt to meet the basic health needs of their populations. They rely on contracting out to private (for-profit and not-for-profit) organizations as a strategy to meet the needs of underserved populations. For the most part, the public sector chooses to contract out primary healthcare services to the private sector to expand access, increase the availability of medicines and medical supplies, and improve the quality of care. In both urban and rural settings, private for-profit and non-profit health service providers serve both the rich and the poor. Communities often recognize private sector healthcare providers to be more responsive to their healthcare needs and preferences in terms of services available, suitable timings and geographical access etc. Private sector has always played a significant role in the delivery of health services in developing countries. Public-private-partnership (PPP) is an approach under which services are delivered by the private sector, while the responsibility for providing the resources rests with the government. Establishing a PPP requires a legal framework acceptable to all the partners, clarity on the commitment of resources, roles and responsibilities of each partner, as well as accountability to provide a given set of services at a desired level of quality and affordable user charges. Formalizing such an arrangement between partners requires conceptualising a framework for Public Private Partnership (PPP) to manage the delivery of health services. In this paper, we describe the design, development and implementation of a PPP for managing urban health services in Ahmedabad city, Gujarat. Our model has succeeded in bringing together compatible public and private partners to plan and deliver quality healthcare services to meet the community needs of Vasna ward, in Ahmedabad. The new Vasna Urban Health centre was inaugurated on July 23, by the Chief Minister of Guajarat. This new centre now serves about 120 outpatients everyday as against an average of 10 outpatients daily earlier.