Climate change, local institutions and adaptation experience: the village tank farming community in the dry zone of Sri Lanka

Farmers are in a continuous process of, individually and as community groups, adjusting to the observed variability in climate parameters. Climate shocks are considered by farmers in their decision-making as factors affecting risk and uncertainty, and farmers make their choices so as to minimize such risks. The overall outcome of these individual and community efforts is known as ‘climate adaptation’, which itself is a continuous process. Farmers are traditionally supported by local institutions in this process, which are also currently in a state of transformation. This study examines the climate adaptation responses of the village tank farming community in the dry zone of Sri Lanka in the context of transforming socioeconomic conditions and with the objective of identifying policy implications for adaptation to global climate change. The study was conducted in six Divisional Secretariat areas in the Anuradhapura District of the North Central Province. Both, primary and secondary data was collected in the study. The major sources of primary data included a series of focus group discussions and key informant interviews conducted with village tank farmers and local officers. The findings reveal that there are two major forms of voluntary adaptation responses by farmers against climate shocks: 1) aligning of farming activities with the recognized seasonal pattern of rainfall; and 2) management of rain water harvested in commonly owned village tanks. Farmers’ adaptation responses have been facilitated by local institutions that helped to adopt joint adaptation responses. However, recent socioeconomic dynamics introduced by rapid population increase, spread of commercial opportunities and change in agricultural technology have drastically altered conditions in the village tanks in favor of developing a commercial farming system. As a result, local institutions that traditionally facilitated the climatic adaptation responses are also in a state of transition. Therefore, farmers face problems in adapting to the impending risks and uncertainties of global climate change. The paper emphasizes the need for appropriate policy measures to facilitate the adaptive capacity of farmers.Length: pp.147-156Climate changeAdaptationFarmersArid landsVillagesTanksCommon property

Cosmic Needles versus Cosmic Microwave Background Radiation

It has been suggested by a number of authors that the 2.7K cosmic microwave background (CMB) radiation might have arisen from the radiation from Population III objects thermalized by conducting cosmic graphite/iron needle-shaped dust. Due to lack of an accurate solution to the absorption properties of exceedingly elongated grains, in existing literature which studies the CMB thermalizing process they are generally modelled as (1) needle-like spheroids in terms of the Rayleigh approximation; (2) infinite cylinders; and (3) the antenna theory. We show here that the Rayleigh approximation is not valid since the Rayleigh criterion is not satisfied for highly conducting needles. We also show that the available intergalactic iron dust, if modelled as infinite cylinders, is not sufficient to supply the required opacity at long wavelengths to obtain the observed isotropy and Planckian nature of the CMB. If appealing to the antenna theory, conducting iron needles with exceedingly large elongations (10^4) appear able to provide sufficient opacity to thermalize the CMB within the iron density limit. But the applicability of the antenna theory to exceedingly thin needles of nanometer/micrometer in thickness needs to be justified.Comment: 13 pages, 4 figures; submitted to ApJ

Finite Source Sizes and the Information Content of MACHO-Type Lens Search Light Curves

If the dark halo matter is primarily composed of MACHOs toward the lower end of the possible detection range ($< 10^{-3}$ $M_{\odot}$) a fraction of the lens detection events should involve the lens crossing directly in front of the disk of the background star. Previously, Nemiroff (1987) has shown that each crossing would create an inflection point in the light curve of the MACHO event. Such inflection points would allow a measure of the time it took for the gravitational lens to cross the stellar disk. Given an independent estimate of the stellar radius by other methods, one could then obtain a more accurate estimate of the velocity of the lens. This velocity could then, in turn, be used to obtain a more accurate estimate of the mass range for the MACHO or disk star doing the lensing.Comment: in press: ApJ (Lett.), 10 pages in Plain TeX version 3.0, 1 figure available by FA

The Most Magnetic Stars

Observations of magnetic A, B and O stars show that the poloidal magnetic flux per unit mass has an upper bound of 10^-6.5 G cm^2/g. A similar upper bound is found for magnetic white dwarfs even though the highest magnetic field strengths at their surfaces are much larger. For magnetic A and B stars there also appears to be a well defined lower bound below which the incidence of magnetism declines rapidly. According to recent hypotheses, both groups of stars may result from merging stars and owe their strong magnetism to fields generated by a dynamo mechanism as they merge. We postulate a simple dynamo that generates magnetic field from differential rotation. The growth of magnetic fields is limited by the requirement that the poloidal field stabilizes the toroidal and vice versa. While magnetic torques dissipate the differential rotation, toroidal field is generated from poloidal by an Omega dynamo. We further suppose that mechanisms that lead to the decay of toroidal field lead to the generation of poloidal. Both poloidal and toroidal fields reach a stable configuration which is independent of the size of small initial seed fields but proportional to the initial differential rotation. We pose the hypothesis that strongly magnetic stars form from the merging of two stellar objects. The highest fields are generated when the merge introduces differential rotation that amounts to critical break up velocity within the condensed object. Calibration of a simplistic dynamo model with the observed maximum flux per unit mass for main-sequence stars and white dwarfs indicates that about 1.5x10^-4 of the decaying toroidal flux must appear as poloidal. The highest fields in single white dwarfs are generated when two degenerate cores merge inside a common envelope or when two white dwarfs merge by gravitational-radiation angular momentum loss.Comment: accepted by MNRAS 8 pages, 3 figure

The open cluster initial-final mass relationship and the high-mass tail of the white dwarf distribution

Recent studies of white dwarfs in open clusters have provided new constraints on the initial - final mass relationship (IFMR) for main sequence stars with masses in the range 2.5 - 6.5 Mo. We re-evaluate the ensemble of data that determines the IFMR and argue that the IFMR can be characterised by a mean initial-final mass relationship about which there is an intrinsic scatter. We investigate the consequences of the IFMR for the observed mass distribution of field white dwarfs using population synthesis calculations. We show that while a linear IFMR predicts a mass distribution that is in reasonable agreement with the recent results from the PG survey, the data are better fitted by an IFMR with some curvature. Our calculations indicate that a significant (~28%) percentage of white dwarfs originating from single star evolution have masses in excess of ~0.8 Mo, obviating the necessity for postulating the existence of a dominant population of high-mass white dwarfs that arise from binary star mergers.Comment: 5 pages, 2 color Postscript figures. Accepted for publication in MNRA

COLOR RESOLVED CHERENKOV IMAGING ALLOWS FOR DIFFERENTIAL SIGNAL DETECTION IN BLOOD AND MELANIN CONTENT

Cherenkov imaging in radiation therapy allows a video display of the irradiation beam on the patient’s tissue, for visualization of the treatment. High energy radiation from a linear accelerator (Linac) results in the production of spectrally-continuous broadband light inside tissue due to the Cherenkov effect; this light is then attenuated by tissue features from transport and exits from the delivery site. Progress with the development of color Cherenkov imaging has opened the possibility for some level of spectroscopic imaging of the light-tissue interaction and interpretation of the specific nature of the tissue being irradiated. Generally, there is a linear relationship between Cherenkov emission and dose in a homogenous medium; however human tissue has multiple factors of scatter and absorption that result in the distortion of this linear relationship. This project investigated what color Cherenkov imaging could be used for, in the situation of tissue with different levels of pigmentation present in skin and/or different levels of hemoglobin present inside the tissue. A custom-developed time-gated three-channel intensified camera was used to image the Red Green and Blue (RGB) Cherenkov emission from tissue phantoms that had synthetic epidermal layers and blood. The hypothesis was that RGB color Cherenkov imaging would allow for the detection of signals that varied uniquely in these channels in response to changes in blood content or melanin content, because of their different absorption spectra in the RGB channels. Oxy-hemoglobin in the blood is highly absorbing in the blue & green, but not as much in the red, whereas the melanin is highly absorbing across the channels, falling slightly from blue through green and red. The results showed that these spectral absorption differences did indeed lead to different amounts of exiting light, predominantly in the red wavelength band, where melanin has a higher relative absorption than blood. This observation leads to the provision for future color distortion corrections, and interpretation of more accurate Cherenkov imaging via color-based modeling or correction for dose quantification. Based on this work, it is possible to separate the effects of attenuation from skin color or blood volume based upon the colors seen in the Cherenkov images, as these are emissions that are specific to the patient

Level correlations in integrable systems

We derive a simple analytical expression for the level correlation function of an integrable system. It accounts for both the lack of correlations at smaller energy scales and for global rigidity (level number conservation) at larger scales. We apply our results to a rectangle with incommensurate sides and show that they are in excellent agreement with the limiting cases established in the semiclassical theory of level rigidity.Comment: 5 page