1,995 research outputs found
Health Transfers: An Application of Health-Health Analysis to Assess Food Safety Regulations
The authors apply a Health-Health Analysis to risks associated with harvesting Gulf oysters to evaluate that approach to managing health and safety risks
Effects of Collisions with Rocky Planets on the Properties of Hot Jupiters
Observed Hot Jupiters exhibit a wide range of physical properties. For a
given mass, many planets have inflated radii, while others are surprisingly
compact and may harbor large central cores. Motivated by the observational
sample, this paper considers possible effects from collisions of smaller rocky
planets with gas giant planets. In this scenario, the Jovian planets migrate
first and enter into (approximately) 4 day orbits, whereas rocky planets (mass
= 0.1-20 that of Earth) migrate later and then encounter the gaseous giants.
Previous work indicates that the collision rates are high for such systems.
This paper calculates the trajectories of incoming rocky planets as they orbit
within the gaseous planets and are subjected to gravitational, frictional, and
tidal forces. These collisions always increase the metallicity of the Jovian
planets. If the incoming rocky bodies survive tidal destruction and reach the
central regions, they provide a means of producing large planetary cores. Both
the added metallicity and larger cores act to decrease the radii of the gas
giants at fixed mass. The energy released during these collisions provides the
Jovian planet with an additional heat source; here we determine the radial
layers where kinetic energy of the colliding body is dissipated, including the
energy remaining upon impact with the existing core. This process could have
long-term effects if the colliding body deposits significant energy deep in the
interior, in regions of high opacity. Both Hot Jupiters and newly formed gas
giants have inflated radii, large enough to allow incoming rocky planets to
survive tidal disruption, enhance the central core mass, and deposit
significant energy (in contrast, denser giant planets with the mass and radius
of Jupiter are expected to tidally destroy incoming rocky bodies).Comment: 35 pages, 11 figures, accepted to PAS
Destruction of Refractory Carbon in Protoplanetary Disks
The Earth and other rocky bodies in the inner solar system contain
significantly less carbon than the primordial materials that seeded their
formation. These carbon-poor objects include the parent bodies of primitive
meteorites, suggesting that at least one process responsible for solid-phase
carbon depletion was active prior to the early stages of planet formation.
Potential mechanisms include the erosion of carbonaceous materials by photons
or atomic oxygen in the surface layers of the protoplanetary disk. Under
photochemically generated favorable conditions, these reactions can deplete the
near-surface abundance of carbon grains and polycyclic aromatic hydrocarbons by
several orders of magnitude on short timescales relative to the lifetime of the
disk out to radii of ~20-100+ au from the central star depending on the form of
refractory carbon present. Due to the reliance of destruction mechanisms on a
high influx of photons, the extent of refractory carbon depletion is quite
sensitive to the disk's internal radiation field. Dust transport within the
disk is required to affect the composition of the midplane. In our current
model of a passive, constant-alpha disk, where alpha = 0.01, carbon grains can
be turbulently lofted into the destructive surface layers and depleted out to
radii of ~3-10 au for 0.1-1 um grains. Smaller grains can be cleared out of the
planet-forming region completely. Destruction may be more effective in an
actively accreting disk or when considering individual grain trajectories in
non-idealized disks.Comment: 15 pages, 9 figures, Accepted for publication in Ap
Effectiveness of Subgingival Scaling and Root Planing: Single Versus Multiple Episodes of Instrumentation
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142277/1/jper0367.pd
Renal revascularization in Takayasu arteritis–induced renal artery stenosis
AbstractPurposeThis study was undertaken to define the long-term effects of renal revascularization on blood pressure, and renal and cardiac function in patients with Takayasu arteritis–induced renal artery stenosis (TARAS).MethodsTwenty-seven patients (25 women; mean age, 27 years) with TARAS underwent intervention. Primary, primary assisted, and secondary patency rates were determined, and the late effects on blood pressure, renal and cardiac function, and survival were analyzed.ResultsAll patients had hypertension (mean blood pressure, 167/99 mm Hg; 2.5 antihypertensive medications per patient). Mean estimated glomerular filtration rate in patients not receiving hemodialysis was 76 mL/min, and in five patients serum creatinine concentration was greater than 1.5 mg/dL. Three patients were hemodialysis-dependent, and two had intractable congestive heart failure. Forty interventions were performed, including 32 aortorenal bypass procedures, two repeat implantations, four nephrectomies, and two transluminal angioplasty procedures. Postoperative morbidity was 19%. There were no deaths. During follow-up (mean, 68 months), three graft stenoses, all due to intimal hyperplasia, and three graft occlusions occurred. Two of three graft stenoses were successfully revised. At 1, 3, and 5 years of follow-up, primary patency was 87%, 79%, and 79%, respectively; primary assisted patency was 93%, 89%, 89%, respectively; and secondary patency was 93%, 89%, and 89%, respectively. Intervention resulted in a decrease in blood pressure to a mean of 132/79 mm Hg (P < .0001), and the need for antihypertensive medications was reduced to one per patient (P < .01). Mean glomerular filtration rate increased to 88 mL/min (P < .005), and two patients no longer required hemodialysis. Congestive heart failure resolved in both patients, and did not recur. There were three deaths during follow-up, with 5-year and 10-year actuarial survival of 96% and 80%, respectively.ConclusionsRenal revascularization to treat TARAS is durable, has a salutary effect on blood pressure, and enhances long-term renal and cardiac function. This response establishes renal revascularization as a successful and durable intervention for TARAS, and a benchmark to which other therapies should be compared
Special Project -- Legal Issues Arising from the Mexican Economic Crisis
The economic crisis in Mexico, which profoundly altered the financial and political course of that nation, has also had a significant impact on persons and corporations having business ties to Mexico. Foreign investors and businesses now are required to follow new Mexican rules that often differ dramatically from those previously in effect. The impact of the crisis has not been confined to changes in Mexican law. A substantial number of issues have arisen that will have significant bearing on United States and international law.
The Special Project discusses the changes in the legal environment following the crisis, with its focus upon issues confronting private persons, principally foreign businesses and investors. The Introduction and Overview summarizes the history and structure of Mexico\u27s regulation of foreign investment and recounts the events of the crisis. The first section of the Special Project examines the problems faced by foreign lenders and creditors. Specifically, it addresses the following: (1) the Mexican regulations that set forth the schedules for repayment of amounts owed to foreign creditors; (2) the possibilities for relief should the obligations be dishonored; (3) the efficacy of leading proposals for the restructuring of Mexican and international debt; and (4) the recently promulgated laws and regulations that will govern future international lending activity by United States banks. The second section explores the problems of investors in devalued peso-denominated accounts and the applicability of United States securities laws to those obligations. Section three addresses the immigration problem now exacerbated by the economic crisis and discusses the scope, effect, and wisdom of the proposed Simpson-Mazzoli Bill. The fourth section studies transborder environmental issues that recently have arisen as a result of Mexico\u27s desire for rapid industrial development
Managing Your Farm and Ranch Operation
4 pp.A good manager invests time in careful planning, which includes developing a vision and a mission statement to guide the business enterprise. This publications discusses management of finances, people, equipment and land resources
A survey approach for finding cases of epilepsy.
Identify persons with epilepsy by first looking for
prescriptions for particular antiseizure drugs. Follow these prescriptions from the pharmacies to the
physicians who wrote them for patients. Ask the
physicians whether the patients have epilepsy. Finally, contact the patients who do have epilepsy to
elicit information about the impact of that condition
on their lives.
With these steps, it may be possible to carry out
successfully a probability survey of epilepsy in the
United States population. To learn more about this
approach, a field test was funded by the National
Institute of Neurological and Communicative Disorders and Stroke (NINCDS) of the Public Health
Service. From 1978 through 1982, the work was
planned, carried out, and evaluated by Research
Triangle Institute, Research Triangle Park, NC.
Epilepsy is a sensitive topic to ask about in a
survey. Also, the condition is sufficiently rare to
render ordinary survey approaches inefficient. Even
if rarity were not an issue, there would be the problem of response error because a person with
epilepsy does not, as a rule, have much clinical
information on his or her condition. Better information lies with the physician who provides the care,
but many physicians are busy with their practices.
Furthermore, their record systems are usually not
designed for easy retrieval of information, unless
the names of patients are available. In the survey
approach considered here, the names of patients
are obtained through a random sampling of prescriptions for antiseizure drugs.
The field test was divided into three phases with
special activities reserved for each. The most important problem confronted was how to safeguard
the confidentiality of relationships between pharmacist and patient and between physician and patient. Special guidelines on confidentiality were put
into effect for the data collection. These guidelines,
however, contributed to serious problems of nonresponse-especiallyfor physicians. This article provides a brief account of the field test, including a
rationale for the survey strategy of finding cases
of epilepsy through prescriptions for antiseizure
drugs
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