10,257 research outputs found

    Did Prepayments Sustain the Subprime Market?

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    This paper demonstrates that the reason for widespread default of mortgages in the subprime market was a sudden reversal in the house price appreciation of the early 2000's. Using loan-level data on subprime mortgages, we observe that the majority of subprime loans were hybrid adjustable rate mortgages, designed to impose substantial financial burden on reset to the fully indexed rate. In a regime of rising house prices, a financially distressed borrower could avoid default by prepaying the loan and our results indicate that subprime mortgages originated between 1998 and 2005 had extremely high prepayment rates. Most important, prepayment rates on subprime mortgages were extremely high (i) not just for ARMs but FRMs as well, (ii) even before the reset dates on hybrid-ARMs and (iii) despite prepayment penalties on the contract. However, a sudden reversal in house price appreciation increased default in this market because it made this prepayment exit option cost-prohibitive. In short, prepayments sustained the subprime boom and the extremely high default rates on 2006-2007 vintages were largely due to the inability of these mortgages to prepay (an option that was available for mortgages of earlier vintages).mortgages;subprime;refinance;prepayment;crisis

    X-rays from Saturn: A study with XMM-Newton and Chandra over the years 2002-05

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    We present the results of the two most recent (2005) XMM-Newton observations of Saturn together with the re-analysis of an earlier (2002) observation from the XMM-Newton archive and of three Chandra observations in 2003 and 2004. While the XMM-Newton telescope resolution does not enable us to resolve spatially the contributions of the planet's disk and rings to the X-ray flux, we can estimate their strengths and their evolution over the years from spectral analysis, and compare them with those observed with Chandra. The spectrum of the X-ray emission is well fitted by an optically thin coronal model with an average temperature of 0.5 keV. The addition of a fluorescent oxygen emission line at ~0.53 keV improves the fits significantly. In accordance with earlier reports, we interpret the coronal component as emission from the planetary disk, produced by the scattering of solar X-rays in Saturn's upper atmosphere, and the line as originating from the Saturnian rings. The strength of the disk X-ray emission is seen to decrease over the period 2002 - 2005, following the decay of solar activity towards the current minimum in the solar cycle. By comparing the relative fluxes of the disk X-ray emission and the oxygen line, we suggest that the line strength does not vary over the years in the same fashion as the disk flux. We consider possible alternatives for the origin of the line. The connection between solar activity and the strength of Saturn's disk X-ray emission is investigated and compared with that of Jupiter. We also discuss the apparent lack of X-ray aurorae on Saturn and conclude that they are likely to lie below the sensitivity threshold of current Earth-bound observatories. A similar comparison for Uranus and Neptune leads to the same disappointing conclusion.Comment: 10 pages, 5 figures; to be published in 'Astronomy and Astrophysics

    Effect of Growth Media on Seed Germination and Seedling Growth in Papaya (Carica papaya L.) Cv. Red Lady

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    The study was carried out to explore the effect of growth media on seed germination and seedling growth in papaya cv. Red Lady. Three types of media with three levels of cocopeat were studied. The experiment was laid out in Completely Randomized Design, with nine treatment combinations, and replicated thrice. Results showed that the medium Vermicompost + Sand + Pond soil (1:1:1) with 2cm cocopeat layer on top of the polybag (T9) gave highest germination rate (92.71%), maximum speed of emergence (493.34), highest seed vigour (89.33), maximum germination index (7.18), highest germination value (25.58), the least time required for imbibition (9.37 days) and minimum time taken to germination (3.22 days). Medium T9 was also found to be the best for growth of 'Red Lady' papaya seedlings as it gave the highest values for seedling growth parameters like seedling height (23.05cm), leaf area (339.26cm2), number of leaves (9.84), stem diameter (3.32mm), number of roots (16.68), root length (9.93cm), total biomass (4.89g plant-1) and lowest root/shoot ratio (0.21). This treatment significantly reduced seedling mortality and produced maximum number of healthy seedlings (92.69%) in minimum number of days (35.24), showing the highest net profit (Rs. 3470.65/1000 seedlings) and benefit:cost ratio (1.84) seedling production

    Electrochemical incineration of wastes

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    The novel technology of waste removal in space vehicles by electrochemical methods is presented to convert wastes into chemicals that can be eventually recycled. The important consideration for waste oxidation is to select a right kind of electrode (anode) material that should be stable under anodic conditions and also a poor electrocatalyst for oxygen and chlorine evolution. On the basis of long term electrolysis experiments on seven different electrodes and on the basis of total organic carbon reduced, two best electrodes were identified. The effect of redox ions on the electrolyte was studied. Though most of the experiments were done in mixtures of urine and waste, the experiments with redox couples involved 2.5 M sulfuric acid in order to avoid the precipitation of redox ions by urea. Two methods for long term electrolysis of waste were investigated: (1) the oxidation on Pt and lead dioxide electrodes using the galvanostatic methods; and (2) potentiostatic method on other electrodes. The advantage of the first method is the faster rate of oxidation. The chlorine evolution in the second method is ten times less then in the first. The accomplished research has shown that urine/feces mixtures can be oxidized to carbon dioxide and water, but current densities are low and must be improved. The perovskite and Ti4O7 coated with RuO2 are the best electrode materials found. Recent experiment with the redox agent improves the current density, however, sulphuric acid is required to keep the redox agent in solution to enhance oxidation effectively. It is desirable to reduce the use of acid and/or find substitutes

    Multi-Hazard In-Plane Response of Steel-plate Composite (SC) Walls: Out-of-plane and Accident Thermal Loadings

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    Steel-plate composite (SC) walls have been used for the third generation of nuclear power plants, and are being considered for small modular reactors of the future. Modular SC walls are also being considered for commercial applications, owing to their structural efficiency and construction economy. Walls in important structures may be subjected to a combination of loadings due to cascading hazards. Experimental and numerical studies were conducted to evaluate the in-plane response of SC walls (with boundary elements) and wall piers (without boundary elements) subjected to out-of-plane and accident thermal loadings. First series of experiments comprised of four SC wall pier specimens. One control specimen was subjected to in-plane loading (no out-of-plane loading). Three specimens were subjected to different magnitudes of out-of-plane loading in combination with in-plane loading. Experimental results indicate that the in-plane response of wall piers with aspect ratios greater than or equal to 0.6 is flexure dominated. Introducing an out-of-plane force results in out-of-plane shear and moment in the wall piers. Wall piers subjected to out-of-plane shear equal to their nominal shear strength (per US codes) develop flexural yielding and failure due to interaction between the in-plane and out-of-plane moments. Shear failure does not occur for these wall piers. The wall pier specimen subjected to an out-of-plane shear force that is 2.5 times the nominal shear strength (per US codes) was forced into a shear failure mode by the interaction of in-plane shear and out-of plane shear. The second series of experiments involved subjecting one SC wall and one SC wall pier specimen to different magnitudes and durations of accident temperatures in combination with in-plane loading. Experimental results indicate that typical accident temperatures (up to 232˚C) do not result in significant reduction in in-plane strength of walls and wall piers. The strength for accident temperatures can be estimated using existing strength equations (per US codes). However, accident thermal loads result in a significant reduction in the stiffness of wall and wall piers. The reduction is primarily due to concrete cracking and depends on the magnitude of accident temperature. Stiffness reductions of up to 40% of the ambient stiffness were observed. Three-dimensional finite element models were developed for the two series of experiments. Additionally, a fiber-based model was developed to evaluate biaxial moment interaction for SC wall piers. The fiber model was then updated to include axial force-moment interaction and vector shear failure. Results from the numerical models compare favorably with experimental observations and provide additional insights into the behavior of the specimens. Experimental and numerical results formed the basis of strength and stiffness recommendations for SC walls and wall piers subjected to combined in-plane and accident thermal loading. The results were also employed to recommend an interaction surface for in-plane and out-of-plane moments. The recommendations are intended to help designers consider the simultaneous presence of multiple demands due to cascading hazards

    The Role of Opacities in Stellar Pulsation

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    We examine the role of opacities in stellar pulsation with reference to Cepheids and RR Lyraes, and examine the effect of augmented opacities on the theoretical pulsation light curves in key temperature ranges. The temperature ranges are provided by recent experimental and theoretical work that have suggested that the iron opacities have been considerably underestimated. For Cepheids, we find that the augmented opacities have noticeable effects in certain period ranges (around logP1\log P \approx 1) even though there is a degeneracy with mixing length. We also find significant effects in theoretical models of B-star pulsators.Comment: 6 pages, 3 Figures, Proceeding for the "Workshop on Astrophysical Opacities

    Spatial heterogeneity in the radiogenic activity of the lunar interior: Inferences from CHACE and LLRI on Chandrayaan-1

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    In the past, clues on the potential radiogenic activity of the lunar interior have been obtained from the isotopic composition of noble gases like Argon. Excess Argon (40) relative to Argon (36), as compared to the solar wind composition, is generally ascribed to the radiogenic activity of the lunar interior. Almost all the previous estimates were based on, 'on-the-spot' measurements from the landing sites. Relative concentration of the isotopes of 40Ar and 36Ar along a meridian by the Chandra's Altitudinal Composition Explorer (CHACE) experiment, on the Moon Impact Probe (MIP) of India's first mission to Moon, has independently yielded clues on the possible spatial heterogeneity in the radiogenic activity of the lunar interior in addition to providing indicative 'antiquity' of the lunar surface along the ground track over the near side of the moon. These results are shown to broadly corroborate the independent topography measurements by the Lunar Laser Ranging Instrument (LLRI) in the main orbiter Chandrayaan-1. The unique combination of these experiments provided high spatial resolution data while indicating the possible close linkages between the lunar interior and the lunar ambience

    Contrast inversion in neutral atom microscopy using atomic cluster beams

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    This work explores the possibility of atomic cluster beams as a probe for neutral atom microscopy (NAM) measurements. Using a beam of Kr clusters with mean size \sim 104^4 atoms/cluster we demonstrate that topographical contrast can be obtained, similar to that in the case of monoatomic beams. Further, using atomically thin films of MoS2_2 grown on SiO2_2/Si substrate we show that NAM imaging using Kr clusters is also possible in domains where topographical contrast is not expected. Surprisingly, these images show an inverted contrast pattern when compared to the case of monoatomic beams. We attempt to understand these observations on the basis of angular distributions resulting from cluster-surface scattering. Finally, we discuss the implications of these results towards achieving a high lateral resolution neutral atom microscope using atomic cluster beams.Comment: Main manuscript: 10 pages, 6 figures and Supplementary information: 5 pages, 5 figure

    Modulated structure in the martensite phase of Ni1.8Pt0.2MnGa: a neutron diffraction study

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    7M orthorhombic modulated structure in the martensite phase of Ni1.8Pt0.2MnGa is reported by powder neutron diffraction study, which indicates that it is likely to exhibit magnetic field induced strain. The change in the unit cell volume is less than 0.5% between the austenite and martensite phases, as expected for a volume conserving martensite transformation. The magnetic structure analysis shows that the magnetic moment in the martensite phase is higher compared to Ni2MnGa, which is in good agreement with magnetization measurement
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