Physical processes in planetary rings

A summary of research performed in 1990 is presented. The subject areas covered include perturbed narrow rings and the dynamics of circumplanetary dust. Progress made in the area of perturbed narrow rings includes: (1) the possible discovery of an undocumented moonlet in the environs of Saturn's F ring; and (2) the investigation of the consequences of a close satellite perturbing a narrow ring using numerical simulation. Progress made in the area of circumplanetary dust includes: (1) studies of the motion of circumplanetary dust under the action of radiation pressure and various electromagnetic processes; and (2) the initiation of a systematic explanation of the curious consequences of some of the perturbations that act on small particles

Investigations of planetary ring phenomena

Faint planetary rings, their dynamical behavior and physical properties, were the main focus of the research efforts. The motion of weakly-charged dust through the gravitational and magnetic fields of Jupiter were examined. Several topics concerning features of Saturn's rings were addressed. The origin and fate of the Uranian ring dust is presently being studied

Debris about asteroids: Where and how much?

We summarize several recent findings on the size and shape of the region within which material can stably orbit an asteroid. If the asteroid (with assumed density 2.38 g/cu cm) circles the Sun at 2.55 AU, co-planar prograde material will remain trapped whenever started on unperturbed circular orbits at less than about 220 R(sub A) (asteroid radii); co-planar retrograde particles are stable out twice as far. Our 3-D stability surface, which encloses several hundred numerically calculated orbits that start with various inclinations, is shaped like a sphere with its top and bottom sliced off; its dimensions scale like the Hill radius =(mu/3)(exp 1/3)R, where mu is the asteroid-to-solar mass ratio and R is the asteroid's orbital radius. If the asteroid moves along an elliptical orbit, a fairly reliable indicator of the dimensions of the hazard zone is the size of its Hill sphere at the orbit's pericenter. Grains with radii less than a few mm will be lost through the action of radiation forces which can induce escape or cause collisions with the asteroid on times scales of a few years; interplanetary micrometeoroids produce collisional break-up of these particles in approximately 10(exp 4) yrs. The effects of Jupiter and of asteroids that pass close to the target asteroid allow particles to diffuse from the system, again shrinking the hazard zone. None of the considered sources-primordial formation, debris spalled off the asteroid during micrometeoroid impact, captured interplanetary particles, feeder satellites, etc., seem capable of densely populating distant orbits from the asteroid. No certain detections of debris clouds or of binary asteroids have been made. Thus, it seems highly unlikely that a spacecraft fly-by targeted at 100 R(sub A) from the asteroid over its orbital pole would encounter any material

Osteoporotic and Neoplastic Compression Fracture Classification on Longitudinal CT

Classification of vertebral compression fractures (VCF) having osteoporotic or neoplastic origin is fundamental to the planning of treatment. We developed a fracture classification system by acquiring quantitative morphologic and bone density determinants of fracture progression through the use of automated measurements from longitudinal studies. A total of 250 CT studies were acquired for the task, each having previously identified VCFs with osteoporosis or neoplasm. Thirty-six features or each identified VCF were computed and classified using a committee of support vector machines. Ten-fold cross validation on 695 identified fractured vertebrae showed classification accuracies of 0.812, 0.665, and 0.820 for the measured, longitudinal, and combined feature sets respectively.Comment: Contributed 4-Page Paper to be presented at the 2016 IEEE International Symposium on Biomedical Imaging (ISBI), April 13-16, 2016, Prague, Czech Republi

Organization and support of research and development

Thesis (M.B.A.)--Boston Universit

The Effect of Adrenocorticotropin on the Nucleic Acids and Histochemistry of the Guinea-Pig Adrenal Cortex

The effect of adrenocorticotropin (Armour ACTHar gel) on the mean amount of deoxyribonucleic acid (DNA) per nucleus, and the scatter about this mean, in adrenal nuclei from mature guinea-pigs was studied, using cytophotometry of Feulgen stained nuclear smears. The results were compared with those from chemical analysis of the same material. The mean adrenal nuclear DM content was similar to that in a control specimen mounted on the same slide in each instance, except after administration of adrenocorticotropin for 5 and 7 days. Cytophotometric analyses showed a highly statistically significant increase (P<0.01) in mean adrenal nuclear DNA content after treatment of the animals with ACTH for 5 and 7 days, Chemical analyses gave values for adrenal nuclear DNA which were slightly higher than those for pooled kidney nuclei. The significance of these findings is discussed. Statistical analysis of the results indicates that only specimens on the same slide are to be compared when using cyto-photometry of the Feulgen reaction. If specimens on different slides are used for comparison a large error is introduced. The effect of ACTH was also studied on adrenocortical ribonucleic acid (RNA), plasmalogens, alkaline and acid phosphatase, ascorbic acid and glycogen in mature guinea-pigs after treatment with ACTH for similar periods of time (1, 3, 5, 7, 10, 14 and 21 days) and also for 3, 6, 12 and 18hr and for 28 days. A gradual increase in adrenocortical ribonucleic acid occurred with ACTH treatment. This increase was found in all zones of the adrenal cortex. Depletion of lipid and of plasmalogens was evident in the zona fasciculata and zona reticularis after ACTH administration for 3, 6, 12 and 18 hr. In the other experimental groups of animals an increase in lipid and plasmalogens occurred with continued ACTH administration. At 28 days, however, some depletion of these substances was found in the zona reticularis. ACTH administration caused an increased concentration of alkaline and acid phosphatase in all adrenocortical zones. The increase was most evident after treatment with ACTH for 5 and 7 days, when hyperplasia was maximal. Ascorbic acid depletion was observed after ACTH treatment for 3, 6, 12 and 18 hr and for 1 day. The adrenocortical content and distribution of ascorbic acid was normal in adrenals of guinea-pigs receiving ACTH for longer periods. Glycogen depletion occurred at 12 and 18 hr only. The findings are discussed and compared with results of other authors who studied the pituitary-adrenal relationship. It is evident that ribonucleic acid, alkaline and acid phosphatase and ascorbic acid have important roles in adrenocortical Physiology. The results suggest that ribonucleic acid and phosphatases are probably concerned with adrenocortical hyperplasia. It seems more likely, however, that ascorbic acid and glycogen are concerned with secretion of adrenocortical hormones, as depletion of these substances occurred when secretion of ketosteroids was probably at a maximum

Shakespeare\u27s Elizabethan public.

Of all the arts drama is the most democratic. Other forms of artistic and aesthetic expression, literature, music, painting, may be cultivated in solitude. Not so the drama. It is demanded by the public; produced for the public and unless it is approved by the public its doom is certain. Why it is that the drama cannot at any time break away from the tastes, prejudices, and ideals of the public for which it was written, M. Edelstand Du Meril has clearly state: “But the inspiration of the work (the drama) hasn’t at all that egotistical spirit, disdainful of the outside world, which characterizes the other forms of art; this is no longer a monologue of the poet singing to himself for his own pleasure; this author tries by what his drama represents to awaken in others the poetical ideas which have inspired him and are for him real….The serious end of drama, then, depends upon the ideas of the poet in regard to nature and the destiny of man, and his ideas are intimately bound up with the religion and the philosophy of his time…..If a dramatist doesn’t wish to employ his gifts in an effort condemned to failure in advance, he must - and this is one of the first duties of the artist - consider his public, respect their sentiments, and skillfully conform to their ideas and customs.” Knowledge of all this Shakespeare not only possessed but utilized in all his works. In order, then, to appreciate our great literary master in all his fullness, we must have an adequate conception of the conditions under which he lived and wrought, and of the public for the satisfaction of whose desires his work of dramatic creation was being done. Rightly to interpret the drama of our own day, which his, after all, only the reflection of our current life and manners, we must grasp the meaning of the most vital elements in the lives of men and women about us. So, also, to appreciate Shakespeare as a dramatist, must we understand the Elizabethans, the public for which he wrote. Then and only then can we attain an adequate conception of what the Elizabethan drama was. A play is what it is because the people for whose amusement and edification it was originally written and presented were what they were. The spectators at any stage presentation bring with them all the prejudices and pre-conceptions natural to their own day and generation, so that no matter whether the scene be laid in remote antiquity or far-away climes, the spirit of the drama must ring a responsive note in the hearts of the people who assemble to behold it