Numerical study of linearized unsteady stagnation flow

The stability of stagnation point flow has long been recognized as an important problem in aerodynamic analysis. Boundary layer disturbances located near the stagnation line can have a significant effect on the overall properties of an airfoil. One example of current interest is the analysis of unsteady multi-phase stagnation flows for application to problems involving aircraft icing. In this study, numerical methods which can be used to address the stability and non-parallel unsteady development of such stagnation point problems are investigated for linearized single phase aerodynamic flows using both two-dimensional and three-dimensional methods. A streamfunction-vorticity formulation is evaluated for two-dimensional linearized stagnation flows. In addition, a primitive variable formulation is developed for three-dimensional linearized stagnation flows. The two methods are tested for grid refinement, and results obtained using the three-dimensional method are compared with those from the two-dimensional method. As expected, it is found that three-dimensional disturbances decay at a faster rate than two-dimensional ones

Informed Refusal: Physician Liability for Failure to Inform of the Risks Associated with Refusing Diagnostic Tests

This Comment explores the validity and development of patient control over the medical information-gathering and decision-making process. The author argues that, traditionally, the doctrine of informed consent governed the presentation of information about methods of treatment by a physician to allow a patient to make an informed choice. The author further argues that recent decisions in California and Washington have extended the consent doctrine in order to promote patient participation in diagnostic decision-making. The author considers the policies and problems underlying informed refusal in the diagnostic process, and suggests that informed refusal should be favored by advocates of patient autonomy

Sedimentology and kinematics of a large, retrogressive growth-fault system in Upper Carboniferous deltaic sediments, western Ireland

Growth faulting is a common feature of many deltaic environments and is vital in determining local sediment dispersal and accumulation, and hence in controlling the resultant sedimentary facies distribution and architecture. Growth faults occur on a range of scales, from a few centimetres to hundreds of metres, with the largest growth faults frequently being under-represented in outcrops that are often smaller than the scale of feature under investigation. This paper presents data from the exceptionally large outcrops of the Cliffs of Moher, western Ireland, where a growth-fault complex affects strata up to 60 m in thickness and extends laterally for 3 km. Study of this Namurian (Upper Carboniferous) growth-fault system enables the relationship between growth faulting and sedimentation to be detailed and permits reconstruction of the kinematic history of faulting. Growth faulting was initiated with the onset of sandstone deposition on a succession of silty mudstones that overlie a thin, marine shale. The decollement horizon developed at the top of the marine shale contact for the first nine faults, by which time aggradation in the hangingwall exceeded 60 m in thickness. After this time, failure planes developed at higher stratigraphic levels and were associated with smaller scale faults. The fault complex shows a dominantly landward retrogressive movement, in which only one fault was largely active at any one time. There is no evidence of compressional features at the base of the growth faults, thus suggesting open-ended slides, and the faults display both disintegrative and non-disintegrative structure. Thin-bedded, distal mouth bar facies dominate the hangingwall stratigraphy and, in the final stages of growth-fault movement, erosion of the crests of rollover structures resulted in the highest strata being restricted to the proximity of the fault. These upper erosion surfaces on the fault scarp developed erosive chutes that were cut parallel to flow and are downlapped by the distal hangingwall strata of younger growth faults

Effect of Negative Ions Upon Rates of Reaction of Zinc With Hydrochloric and Perchloric Acids

The rate of evolution of hydrogen by the action hydrochloric acid and perchloric acid on zinc was measured volumetrically as a function of various negative ion concentrations. Increasing zinc ion concentration retards the rate of the reaction. A four to one ratio of chloride to zinc ion reaccelerates the rate, suggesting the formation of Zn Cl4-- which removes the excess zinc ion from the reaction. Other complexing ions, thiocyanate, bromide and iodide ion, accelerate the reaction as does chloride. Sulfate, like perchlorate, has little effect. The results explain the fact that hydrochloric acid reacts with zinc at a higher rate than does perchloric acid of equal concentration and similar strength

A Mathematical Theory of Stochastic Microlensing II. Random Images, Shear, and the Kac-Rice Formula

Continuing our development of a mathematical theory of stochastic microlensing, we study the random shear and expected number of random lensed images of different types. In particular, we characterize the first three leading terms in the asymptotic expression of the joint probability density function (p.d.f.) of the random shear tensor at a general point in the lens plane due to point masses in the limit of an infinite number of stars. Up to this order, the p.d.f. depends on the magnitude of the shear tensor, the optical depth, and the mean number of stars through a combination of radial position and the stars' masses. As a consequence, the p.d.f.s of the shear components are seen to converge, in the limit of an infinite number of stars, to shifted Cauchy distributions, which shows that the shear components have heavy tails in that limit. The asymptotic p.d.f. of the shear magnitude in the limit of an infinite number of stars is also presented. Extending to general random distributions of the lenses, we employ the Kac-Rice formula and Morse theory to deduce general formulas for the expected total number of images and the expected number of saddle images. We further generalize these results by considering random sources defined on a countable compact covering of the light source plane. This is done to introduce the notion of {\it global} expected number of positive parity images due to a general lensing map. Applying the result to microlensing, we calculate the asymptotic global expected number of minimum images in the limit of an infinite number of stars, where the stars are uniformly distributed. This global expectation is bounded, while the global expected number of images and the global expected number of saddle images diverge as the order of the number of stars.Comment: To appear in JM

Mercury Concentrations in Spotted Seatrout (Cynoscion nebulosus) from Northwest Florida

We determined total mercury concentrations in dorsal muscle tissue of 112 spotted seatrout (Cynoscion nebulosus) collected between 1993 and 1996 from Pensacola Bay and Choctawhatchee Bay, FL. We describe the relationships of length, weight, age, and sex to total mercury concentrations in this species. Fish ranged in size from 235 to 613 mm total length (TL), with a mean of 463 mm TL. The majority (84%) of the fish collected were female. The mean total mercury concentration detected in all fish combined was 0.40 ± 0.15 ppm, and in individual fish, total mercury concentration ranged from 0.11 to 0.88 ppm. We detected no significant differences in mercury concentrations between sexes. Total mercury concentration was positively correlated with fish TL and weight. However, no relationship was evident between total mercury concentration and age. Mercury concentrations detected in the majority of spotted seatrout examined from northwest Florida were below the State of Florida\u27s limited-consumption advisory of 0.5 ppm

Next generation system modeling of NTR systems

The topics are presented in viewgraph form and include the following: nuclear thermal rocket (NTR) modeling challenges; current approaches; shortcomings of current analysis method; future needs; and present steps to these goals

What Accounts for the Education Gender Gap in Pakistan’s Khyber Pakhtunkhwa Province?

There are competing explanations for the persistence of the education gender gap in Pakistan’s Khyber Pakhtunkhwa Province (KPK). Three reasons are given for this persistence, specifically parental and societal attitudes opposed to girls’ education and women’s employment outside the home; a lack of both family and public resources; and low labor market returns to women’s education. We seek to contribute to this debate by analyzing the results of a survey of a random sample of 642 families in the Dir District of KPK with a high-school-aged girl that attended at least some primary school. Our study shows that guardians of a high school aged girl, irrespective of the guardian’s gender, report very strong support for girls’ education and for women’s careers outside the home. These findings contradict the widespread belief that the persistence of the education gender gap in KPK is due to parental or societal attitudes opposed to girls’ education and women’s careers. Rather than parental attitudes opposed to girls’ education, respondents report that the lack of family resources is an important impediment to girls’ school attendance. To test the authenticity of the expressions of strong support for girls’ education, we examine the ability of the survey responses to predict girls’ school attendance beyond the 5th class by estimating a model of the determinants of girls’ school attendance beyond the 5th class