Shock induced vaporization of anhydrite CaSO4 and calcite CaCO3

Discovery of abundant anhydrite (CaSO4) and gypsum (CaSO4.2H2O) in the otherwise carbonate sediments comprising the upper portion of the rocks contained within the Chicxulub impact crater has prompted research on the shock-induced vaporization of these minerals. We use a vaporization criterion determined by shock-induced entropy. We reanalyze the shock wave experiments of Yang [1]. He shocked 30% porous anhydrite and 46% porous calcite. Post-shock adiabatic expansion of the sample across a 5 mm-thick gap and then impact upon an aluminum witness plate backed by LiF window that is monitored with a VISAR. Reanalysis uses Herrman's P-alpha model [2] for porous materials, and a realistic interpolation gas equation-of-state for vaporization products. Derived values of the entropies for incipient and complete vaporization for anhydrite are 1.65±0.12 and 3.17±0.12 kJ(kg.K)–1, and for calcite these are 0.99±0.11 and 1.93±0.11 kJ(kg.K)–1. Corresponding pressures for incipient and complete vaporization along the Hugoniot of non-porous anhydrite are 32.5±2.5 and 122±13 GPa and for non-porous calcite are 17.8±2.9 and 54.1±5.3 GPa, respectively. These pressures are a factor of 2–3 lower than reported earlier by Yang

Shock temperatures in calcite (CaCO3): Implication for shock induced decomposition

The temperatures induced in crystalline calcite upon planar shock compression (95–160 GPa) are reported from two-stage light gas-gun experiments. The temperatures are obtained fitting 6-channel optical pyrometer radiances in the 450 to 900 nm range, to a Planck radiation law temperature varied from 3300 to 5400 K. Calculations demonstrate that the temperatures are some 400 to 1350 K lower than if either shock-induced melting and/or disproportionation of calcite behind the shock front was not occurring. Here calcite is modeled as disproportionating into a molecular liquid, or a solid CaO plus CO2 gas. For temperature calculations, specific heat at constant volume for one mole of CO2 is taken to be 6.7R as compared to 9R in the solid state; whereas calcite and CaO have their solid state values (15R and 6R). Calculations also suggest that the onset of decomposition in calcite to CaO and CO2 during loading occurs at ~75±10 GPa, along the Hugoniot whereas decomposition begins upon unloading from 18 GPa. The 18 GPa value is based on comparison of VISAR measurements of particle velocity profiles induced upon isentropic expansion with one-dimensional numerical simulation

Covariant hamiltonian spin dynamics in curved space-time

The dynamics of spinning particles in curved space-time is discussed, emphasizing the hamiltonian formulation. Different choices of hamiltonians allow for the description of different gravitating systems. We give full results for the simplest case with minimal hamiltonian, constructing constants of motion including spin. The analysis is illustrated by the example of motion in Schwarzschild space-time. We also discuss a non-minimal extension of the hamiltonian giving rise to a gravitational equivalent of the Stern-Gerlach force. We show that this extension respects a large class of known constants of motion for the minimal case.Comment: 14 pages, accepted version for Phys Lett B, added a footnote and two reference

Mass spectrometer calibration of Cosmic Dust Analyzer

The time of flight mass spectrometer of the Cosmic Dust Analyzer (CDA) instrument aboard the Cassini spacecraft, is expected to be placed in orbit about Saturn to sample the ring material and satellite impact ejecta. Upon impact of an incident dust particle against the target plate at velocities of 5-100 km/s, some 10–8 to 10–5 times the particle mass of positive valence, single-charged ions is induced. These are analyzed via a time-of-flight mass spectrometer. Initial experiments employing a pulsed N2 laser (>300 µJ/pulse, 4ns, 337nm) acting on a suite of samples are described. The laser beam is focussed to deliver the light pulses onto a laser power density (1011 W/cm2) to simulate the impact of particles. Laser ionization produced a charge of 4.6 pC per pulse for aluminum alloy. Estimating that each Al+1 ion require energy of 5.98 eV ionization energy/ion implies that 10–5% of the laser energy produced ions and the present system has a 5% efficiency of collecting the laser-irradiation induced ions. Employing a multi-channel plate detector in this mass spectrometer yields for Al-Mg-Cu alloy and kamacite (Fe-Ni mineral) targets well defined peaks at 24 (Mg+1), 27 (Al+1) and 64 (Cu+1), and 56 (Fe+1), 58 (Ni+1) and 60 (Ni+1) dalton, respectively

Spinning bodies in curved space-time

We study the motion of neutral and charged spinning bodies in curved space-time in the test-particle limit. We construct equations of motion using a closed covariant Poisson-Dirac bracket formulation which allows for different choices of the hamiltonian. We derive conditions for the existence of constants of motion and apply the formalism to the case of spherically symmetric space-times. We show that the periastron of a spinning body in a stable orbit in a Schwarzschild or Reissner-Nordstr{\o}m background not only precesses, but also varies radially. By analysing the stability conditions for circular motion we find the innermost stable circular orbit (ISCO) as a function of spin. It turns out that there is an absolute lower limit on the ISCOs for increasing prograde spin. Finally we establish that the equations of motion can also be derived from the Einstein equations using an appropriate energy-momentum tensor for spinning particles.Comment: 26 pages, 5 figures; v2: version accepted for publication; small changes in text and references adde

Mixed-surfactant system of dodecylbenzene sulfonate and alpha-olefin sulfonate: micellar and volumetric studies

Critical micelle concentrations of sodium salts of dodecylbenzene sulfonate, α-olefin (C16) sulfonate, and their mixtures have been evaluated by measuring the surface tensions of solutions at 298.15 K. Interaction parameters for mixed monolayer formation (βσ) and mixed-micelle formation (βM) have been calculated from the critical micelle concentration data. Densities of solutions of surfactants and their mixtures were measured with a vibrating-tube densimeter at 298.15 K. Apparent and partial molar volumes have been evaluated from solution density data. Results of the micellar properties have been eplained on the basis of a nonideal multicomponent mixed-micelle model. The mixed-surfactant system exhibits synergism in all aspects when the mole fraction of alpha-olefin sulfonate in the mixture is 0.2. Volumetric properties correlate well, as the partial molar volumes also show a minimum at the same composition of the mixture. Formation of a compact mixed micelle at this composition has been envisaged

VTrace-A Tool for Visualizing Traceability Links among Software Artefacts for an Evolving System

Traceability Management plays a key role in tracing the life of a requirement through all the specifications produced during the development phase of a software project. A lack of traceability information not only hinders the understanding of the system but also will prove to be a bottleneck in the future maintenance of the system. Projects that maintain traceability information during the development stages somehow fail to upgrade their artefacts or maintain traceability among the different versions of the artefacts that are produced during the maintenance phase. As a result the software artefacts lose the trustworthiness and engineers mostly work from the source code for impact analysis. The goal of our research is on understanding the impact of visualizing traceability links on change management tasks for an evolving system. As part of our research we have implemented a Traceability Visualization Tool-VTrace that manages software artefacts and also enables the visualization of traceability links. The results of our controlled experiment show that subjects who used the tool were more accurate and faster on change management tasks than subjects that didn’t use the tool

Influence of affluence on sustainable housing in Mysore, India

Mysore, the second largest city in the state of Karnataka, India, can be identified as an early adopter of sustainable design practices. Between 1903 and 1947 the use of local construction materials, the Swadeshi movement of 1905, robust planning and clear legislation resulted in sustainable urban development. However, post-colonial development fuelled by economic globalisation after the 1980s has transformed perceptions of the house among the growing middle class, becoming a commodity to demonstrate affluence and status. This paper examines the impact of changing social and cultural values on the aspirations of the growing middle classes on sustainable housing and neighbourhood development in Mysore. The methodology comprises literature and archive research to establish the historical content and review some important recent trends. Extensive fieldwork studies, including questionnaires over a wide range of participants (owners, builders and designers) and semistructured interviews with key players, including academics, architects and government agencies. The focus of development has shifted from community to individual, from energy conserving to a more consumerist attitude in the procurement of materials and finishes. The paper examines the impact of these changes. The results of the survey are summarised and reviewed under the categories of communities, site, entrance, house layout and materials

Traumatic Bone Cyst of Idiopathic Origin? A Report of Two Cases

Background: Traumatic bone cyst (TBC) is an uncommon non-epithelial lined cavity of the jaws. Traumatic bone cysts have been reported in the literature under a variety of names: solitary bone cyst, haemorrhagic bone cyst, extravasation cyst and simple bone cyst. The multitude of names applied to this lesion implies the lack of understanding of the true aetiology and pathogenesis. However, the term "traumatic bone cyst" is the most widely used name today (1).Case Details: A 15 years old male patient presented with a complaint of swelling with mild, intermittent and non-radiating pain in the lower left back teeth region. There was expansion of the buccal cortical plate. Radiograph showed a multilocular lesion straddling between the roots of the teeth. In addition, 21 years old male patient came with a complaint of swelling with mild, continuous pain in the lower left jaw region. OPG showed well defined radiolucency with scalloped borders extending from the periapical region of the 1st premolar until the 2nd molar. The radiolucency was seen extending between the roots of the involved teeth.Conclusion: The majority of TBCs are located in the mandibular body between the canine and the third molar. Clinically, the lesion is asymptomatic in the majority of cases and is often accidentally discovered on routine radiological examination, usually as a unilocular radiolucent area with a "scalloping effect”. Since material for histologic examination may be scanty or non-available it is very often difficult for a definite histologic diagnosis to be achieved (1).Keywords: Traumatic bone cyst, idiopathic origi