Impacts and atmospheric erosion on the early Earth

It was suggested that heating and/or vaporization of accreting carbonaceous-chondrite-type planetestimals could result in the release of their volatile components. Modeling of this process strongly suggests that substantial atmospheres/hydrospheres could develop this way. During most of the accretionary process, impact velocities generally differed from the escape velocity of the growing proto-planet because most of the collisions were between bodies in nearly matching orbits. Toward the end of accretion, however, collisions were rarer but more energetic, involving large planetestimals and higher impact velocities. Such impacts result in a net loss of atmosphere from a planet, and the cumulative effect impacts during the period of heavy bombardment might have dramatically depleted the original atmospheres. Models developed to study atmospheric erosion by impacts on Mars and the interaction of the vapor plume produced by KT impactor on Earth are applied to the case of the evolution of Earth's atmosphere

Jetting and the origin of tektites

The scientific consensus is that tektites were produced by impacts on the Earth, but the exact mechanism by impacts might form tektites is still unclear. The most widely cited mechanism is jetting, which results from the extremely high pressures generated at the intersection of two bodies whose surfaces converge obliquely at high speed. Theory of jetting for thin plates is extended to the case of the impact of the sphere onto a half-space. The calculations are done for the impact of a silicate sphere onto a silicate target for impact speeds of 15, 20, and 25 km/sec, spanning the range of reasonable impact speeds for asteroids. The angle of impact is varied from 0 to 75 deg. The mass jetted, the jet velocity, projectile fraction in the jet, azimuthal distribution of the jet, and the phase of the jetted material are calculated as functions of time. The total mass jetted and the overall mass-averages of jet velocity, etc. are also calculated

An approach to high speed ship ride quality simulation

The high speeds attained by certain advanced surface ships result in a spectrum of motion which is higher in frequency than that of conventional ships. This fact along with the inclusion of advanced ride control features in the design of these ships resulted in an increased awareness of the need for ride criteria. Such criteria can be developed using data from actual ship operations in varied sea states or from clinical laboratory experiments. A third approach is to simulate ship conditions using measured or calculated ship motion data. Recent simulations have used data derived from a math model of Surface Effect Ship (SES) motion. The model in turn is based on equations of motion which have been refined with data from scale models and SES of up to 101 600-kg (100-ton) displacement. Employment of broad band motion emphasizes the use of the simulators as a design tool to evaluate a given ship configuration in several operational situations and also serves to provide data as to the overall effect of a given motion on crew performance and physiological status

Melt droplet formation in energetic impacts

Impacts between rocky bodies at velocities exceeding about 15 km/sec are capable of melting or vaporizing both the impacting object and a portion of the target. Geological materials initially shocked to high pressure approach the liquid-vapor phase boundary from the liquid side as they decompress, breaking up into an expanding spray of liquid droplets. A simple theory is presented for estimating the sizes of these droplets as a function of impactor size and velocity. It is shown that these sizes are consistent with observations of microtektites and spherules found in the Cretaceous-Tertiary boundary layer, the Acraman impact structure, Archean beds in South Africa and lunar regolith. The model may also apply to the formation of chondrules

Production of impact melt in craters on Venus, Earth, and the moon

Impact craters imaged by Magellan clearly show large amounts of flow-like ejecta whose morphology suggests that the flows comprise low-viscosity material. It was suggested that this material may be either turbidity flows or very fine-grained ejecta, flows of ejecta plus magma, or impact melts. The last of these hypotheses is considered. If these flows are composed of impact melts, there is much more melt relative to the crater volume than is observed on the moon. The ANEOS equation of state program was used for dunite to estimate the shock pressures required for melting, with initial conditions appropriate for Venus, Earth, and the moon. A simple model was then developed, based on the Z-model for excavation flow and on crater scaling relations that allow to estimate the ratio of melt ejecta to total ejecta as a function of crater size on the three bodies

Value and Truth in Literature: The Critic versus the Reader from Henry James\u27 Perspective as Applied to Reader Response Theory

Based on Reader Response Theory, without an audience and interpretation a piece of literature does not have value and does not elicit a truth. It has to communicate. Further, Henry James in his work is not only saying that interpretation by a reader is of vital importance in creating value and truth, he implies that there are different types of readers and he specifically, in the works cited, seems to differentiate between the role of a literary critic and a casual reader. He creates narrators at varied levels of education and knowledge on purpose to elicit from the reader different points-of-view. But, he does not tell the reader what to believe about his narrator. He purposefully leaves a sense of ambiguity about the reliability of the narrator to be interpreted by the reader. This creates layers of possible interpretations that change with different approaches to the reading. This is in line with Reader Response Theory in that it considers interpretation of text by the reader as something dynamic and oscillating. James is concerned as Stanley Fish is with the reliability of the reader, and because he often wrote about a part of society that was in great flux, the Fish proposal of a community of readers would have appealed to James. The conclusion drawn is that human truths cannot be labelled nor categorized. Henry James knew this. He calls this truth \u27it\u27 and equates \u27it\u27 to heart and the artistic muse. So, the base of the argument is that the literary critic alone cannot determine both value and truth in a text. To get to the heart, the \u27it,\u27 it takes the emotionally invested reader and it changes and mutates with each reading. If we are still reading a piece hundreds of years later it is because it imparts a human truism. Value has been determined by the system of literary interpretation; however, due to the fluctuating ambiguity of interpretation no definitive \u27truth\u27 can be determined. Truth cannot be pigeon-holed. Truth is a dynamic process of interaction of opposing elements in constant flux as both Henry James and Reader Response Theory concludes

Nasal Carriage of Staphylococcus aureus in Australian (pre-clinical and clinical) Medical Students

The nasal carriage of Staphylococcus aureus in 808 Australian medical students was studied. Five groups of students experienced varying degrees of clinical exposure in a hospital environment ranging from 0 to 42 months. The overall percentage of carriers among the five groups did not vary. However, with increasing clinical exposure there was a decrease in the percentage of isolates sensitive to all antibiotics tested, and an increase in the carriage of S. aureus resistant to three or more antibiotics. No carriers of methicillin-resistant S. aureus (MRSA) were detected. The comparative rates of S. aureus carriage between female and male students varied. The relevance of medical students as nasal carriers of S. aureus in the hospital environment today is discussed

Use of Pneuma Tic Pulse Stimulus for Inducement of Large Amplitude Flexural Waveforms in Web Materials for the Purpose of Local Tension Measurement

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