Laser discrimination by stimulated emission of a phosphor

A method for discriminating sources of UV, near infrared, and far infrared laser radiation was discovered. This technology is based on the use of a single magnesium sulfide phosphor doubly doped with rare earth ions, which is thermally/optically stimulated to generate colors correlatable to the incident laser radiation. The phosphor, after initial charging by visible light, exhibits green stimulated luminescence when exposed to a near infrared source (Nd: YAG laser). On exposure to far infrared sources (CO2 laser) the phosphor emission changes to orange color. A UV laser produces both an orange red as well as green color. A device using this phosphor is useful for detecting the laser and for discriminating between the near infrared, far infrared, and UV lasers. The technology is also capable of infrared laser diode beam profiling since the radiation source leaves an imprint on the phosphor that can be photographed. Continued development of the technology offers potential for discrimination between even smaller bandwidths within the infrared spectrum, a possible aid to communication or wavemixing devices that need to rapidly identify and process optical signals

Microzonation Studies for Delhi, Jabalpur & Dehradun as Impacted by Bhuj Earthquake

History of earthquakes in our country demonstrate vulnerability to seismic hazards. The recent past, devastating earthquakes in urban areas in India causing heavy economical losses in terms of loss of life, property, disruption of services and damage to environment have been of great concern; the experiences have prompted to carry out in-depth studies and come out with solutions and policies which will go a long way in minimizing the damages caused by seismic ground motions. In this context, microzonation of urban areas have assumed new dimensions. Delhi, the capital city of India has a long seismic history and is being affected by local as well as by the Himalayan earthquakes. The Jabalpur urban agglomeration lies in the field of recurrent seismicity ascribed to the reverse activation of Son-Narmada South Fault. Dehradun, the capital city of Uttaranchal is located in the foot hills of Himalayas and is sitting on a tectonically isolated block confined between main boundary thrust & Himalayan Frontal Thrust. Macroseismic surveys of the earthquake effects have unraveled site-dependent ground amplifications increasing the vulnerability of the built environment to seismic hazards. Hence, a need is felt to carry out prognostic damage scenario of existing building stocks in urban area, review the existing codal provision of buildings so that appropriate disaster mitigation measures can be evolved. Keeping this in view, CBRI, Roorkee (India) has carried out studies to generate inputs on vulnerability of engineered and non-engineered structures and anthropic parameters of population living in dwelling susceptible to damage and other exposure factors for fourth level seismic risk microzonation with engineering seismological perspective. The paper briefly describes the microzonation studies initiated in India for Delhi, the capital city of India, Jabalpur & Dehradun, the capital of newly formed Indian state, Uttaranchal. The paper presents two approaches namely Demand Capacity Ratio (DCR) approach & Rapid Screening Procedure(RSP) for assessment of seismic vulnerability of existing building stocks

Comments on black holes I: The possibility of complementarity

We comment on a recent paper of Almheiri, Marolf, Polchinski and Sully who argue against black hole complementarity based on the claim that an infalling observer 'burns' as he approaches the horizon. We show that in fact measurements made by an infalling observer outside the horizon are statistically identical for the cases of vacuum at the horizon and radiation emerging from a stretched horizon. This forces us to follow the dynamics all the way to the horizon, where we need to know the details of Planck scale physics. We note that in string theory the fuzzball structure of microstates does not give any place to 'continue through' this Planck regime. AMPS argue that interactions near the horizon preclude traditional complementarity. But the conjecture of 'fuzzball complementarity' works in the opposite way: the infalling quantum is absorbed by the fuzzball surface, and it is the resulting dynamics that is conjectured to admit a complementary description.Comment: 34 pages, 6 figures, v3: clarifications & references adde

Explosions of water clusters in intense laser fields

Energetic, highly-charged oxygen ions, $O^{q+}$ ($q\leq 6$), are copiously produced upon laser field-induced disassembly of highly-charged water clusters, $(H_2O)_n$ and $(D_2O)_n$, $n\sim$ 60, that are formed by seeding high-pressure helium or argon with water vapor. $Ar_n$ clusters (n$\sim$40000) formed under similar experimental conditions are found undergo disassembly in the Coulomb explosion regime, with the energies of $Ar^{q+}$ ions showing a $q^2$ dependence. Water clusters, which are argued to be considerably smaller in size, should also disassemble in the same regime, but the energies of fragment O$^{q+}$ ions are found to depend linearly on $q$ which, according to prevailing wisdom, ought to be a signature of hydrodynamic expansion that is expected of much larger clusters. The implication of these observations on our understanding of the two cluster explosion regimes, Coulomb explosion and hydrodynamic expansion, is discussed. Our results indicate that charge state dependences of ion energy do not constitute an unambiguous experimental signature of cluster explosion regime.Comment: Submitted to Phys. Rev.

Annihilation Diagrams in Two-Body Nonleptonic Decays of Charmed Mesons

In the pole-dominance model for the two-body nonleptonic decays of charmed mesons $D \rightarrow PV$ and $D \rightarrow VV$, it is shown that the contributions of the intermediate pseudoscalar and the axial-vector meson poles cancel each other in the annihilation diagrams in the chiral limit. In the same limit, the annihilation diagrams for the $D \rightarrow PP$ decays vanish independently.Comment: 9 pages (+ 3 figures available upon request), UR-1316, ER-40685-766, IC/93/21

Role of Shrubs in Rangeland Based Livestock Production System in Western Rajasthan, India

Rangeland covers ~ 51% of the terrestrial surface of the Earth, and supports half of the world‟s livestock. More than 80 % of forage consumed by domestic livestock is supplied by rangelands in Africa and Asia. Hot arid regions of India cover an area of 31.7 million hectares and out of which Rajasthan state constitutes ~ 61.8 % of the entire area. The crop production in this area is low, unstable and risky. Livestock sustains arid farming systems by virtue of their potential to reduce risk, alleviate poverty, important providers of nutrients and traction for growing crops in smallholder systems and the imparting sustainability of household. The hot arid region of Rajasthan has about 29.08 million livestock. Pastures and grazing lands, residential area and wayside grazing lands, crop by-products and residues, fodder crops etc. are the major feed resources. For the small ruminants and camels, the rangelands are the major source of feed supply. Shrubs are vital component of rangeland vegetation and cover \u3e 70 % of desert landscapes from Aravalli to the international border of the Indian part of Thar desert. They are an important source of feed and assure feed availability in a drought situation. They have remarkable morpho-physiological adaptations to different land forms and survive under harsh edapho-climatic conditions. During recent past, a rapid decline population of browse shrubs is noticed due to their over exploitation, destruction of natural habitat, expending irrigation facilities, increasing agricultural mechanization and changes in land use pattern. In the present paper key species, fodder production and nutritive value of shrubs of hot arid rangelands are discussed

Histološke i biokemijske promjene u jetri i bubrezima štakora izazvane torijevim nitratom

The histopathological and biochemical alterations in rat\u27s liver and kidney induced by daily intraperitoneal administration of thorium nitrate were studied. The activity of alkaline phosphatase and adenosine triphosphatase was found to be inhibited at various intervals and the pathomorphological changes were found to be related to the duration of treatment. The results indicate that the effect of thorium is cumulative and that the biochemical alterations occur prior to histological changes.Toksikološka svojstva torija slabo su istražena, iako torij postaje sve važniji elemenat u industriji. Njegova se upotreba širi, pa se upotrebljava i u medicinskoj dijagnostici (torijev dioksid - thorotrast). U ovom su radu istraživani učinci torijevih soli na bubrege i jetru štakora kojima je torijev nitrat injiciran intraperitonealno u dozi od 10 mg/kg svakog dana kroz 120 dana. Kontrolnim je životinjama injicirana fiziološka otopina na jednak način. U prvih 60 dana pokusa samo je nekoliko štakora uginulo, a nakon toga vremena smrtnost se povećala. Tek nakon 30 dana uočene su histološke promjene jetre u obliku kongestije vena i sinusoida i taj je nalaz postajao sve izrazitiji tijekom vremena. U kasnijoj su fazi nađena degenerativna i nekrotična žarišta. Slične su promjene nađene i u bubrežnom parenhimu. Ovim je promjenama prethodilo smanjenje aktivnosti alkalne fosfataze i adenozin trifosfataze u jetri i u još većoj mjeri u bubregu

Computational Fluid Dynamics in Aerospace Industry in India

The role of computational fluid dynamics (CFD) in the design of fighter aircraft, transport aircraft, launch vehicle and missiles in India is explained. Indigenous developments of grid generators, 3-D Euler and Navier-Stokes solvers using state-of-the-art numerical techniques and physical models have been described. Applications of these indigenous softwares for the prediction of various complex aerodynamic flows over a wide range of Mach number, angle of attacks, are presented. Emergence of CFD methods as an efficient tool for aerospace vehicle design is highlighted.Defence Science Journal, 2010, 60(6), pp.639-652, DOI:http://dx.doi.org/10.14429/dsj.60.58

The information paradox: A pedagogical introduction

The black hole information paradox is a very poorly understood problem. It is often believed that Hawking's argument is not precisely formulated, and a more careful accounting of naturally occurring quantum corrections will allow the radiation process to become unitary. We show that such is not the case, by proving that small corrections to the leading order Hawking computation cannot remove the entanglement between the radiation and the hole. We formulate Hawking's argument as a `theorem': assuming `traditional' physics at the horizon and usual assumptions of locality we will be forced into mixed states or remnants. We also argue that one cannot explain away the problem by invoking AdS/CFT duality. We conclude with recent results on the quantum physics of black holes which show the the interior of black holes have a `fuzzball' structure. This nontrivial structure of microstates resolves the information paradox, and gives a qualitative picture of how classical intuition can break down in black hole physics.Comment: 38 pages, 7 figures, Latex (Expanded form of lectures given at CERN for the RTN Winter School, Feb 09), typo correcte