Observation of an Alfvén Wave Parametric Instability in a Laboratory Plasma.

A shear Alfvén wave parametric instability is observed for the first time in the laboratory. When a single finite ω/Ω_{i} kinetic Alfvén wave (KAW) is launched in the Large Plasma Device above a threshold amplitude, three daughter modes are produced. These daughter modes have frequencies and parallel wave numbers that are consistent with copropagating KAW sidebands and a low frequency nonresonant mode. The observed process is parametric in nature, with the frequency of the daughter modes varying as a function of pump wave amplitude. The daughter modes are spatially localized on a gradient of the pump wave magnetic field amplitude in the plane perpendicular to the background field, suggesting that perpendicular nonlinear forces (and therefore k_{⊥} of the pump wave) play an important role in the instability process. Despite this, modulational instability theory with k_{⊥}=0 has several features in common with the observed nonresonant mode and Alfvén wave sidebands.

Nonlinear excitation of acoustic modes by large-amplitude Alfvén waves in a laboratory plasma.

The nonlinear three-wave interaction process at the heart of the parametric decay process is studied by launching counterpropagating Alfvén waves from antennas placed at either end of the Large Plasma Device. A resonance in the beat wave response produced by the two launched Alfvén waves is observed and is identified as a damped ion acoustic mode based on the measured dispersion relation. Other properties of the interaction including the spatial profile of the beat mode and response amplitude are also consistent with theoretical predictions for a three-wave interaction driven by a nonlinear ponderomotive force.

Quantitative study of guide-field effects on Hall reconnection in a laboratory plasma.

The effect of guide field on magnetic reconnection is quantitatively studied by systematically varying an applied guide field in the Magnetic Reconnection Experiment (MRX). The quadrupole field, a signature of two-fluid reconnection at zero guide field, is altered by a finite guide field. It is shown that the reconnection rate is significantly reduced with increasing guide field, and this dependence is explained by a combination of local and global physics: locally, the in-plane Hall currents are reduced, while globally guide field compression produces an increased pressure both within and downstream of the reconnection region.

Laboratory measurements of the physics of auroral electron acceleration by Alfvén waves.

While the aurora has attracted attention for millennia, important questions remain unanswered. Foremost is how auroral electrons are accelerated before colliding with the ionosphere and producing auroral light. Powerful Alfvén waves are often found traveling Earthward above auroras with sufficient energy to generate auroras, but there has been no direct measurement of the processes by which Alfvén waves transfer their energy to auroral electrons. Here, we show laboratory measurements of the resonant transfer of energy from Alfvén waves to electrons under conditions relevant to the auroral zone. Experiments are performed by launching Alfvén waves and simultaneously recording the electron velocity distribution. Numerical simulations and analytical theory support that the measured energy transfer process produces accelerated electrons capable of reaching auroral energies. The experiments, theory, and simulations demonstrate a clear causal relationship between Alfvén waves and accelerated electrons that directly cause auroras.

Experimental allergic neuritis induced by sensitization with galactocerebroside.

Thirteen of 31 rabbits immunized repeatedly with bovine brain galactocerebroside developed experimental allergic neuritis, manifested by flaccid paresis and hypesthesia of four limbs, 2 to 11 months after the initial inoculation. Electrophysiological studies revealed multifocal conduction block of peripheral nerves. Perivenular demyelinative lesions associated with phagocytic mononuclear cells occurred in spinal ganglia, roots, and less frequently in distal nerves.

Primary cerebral fibrosarcoma in a child.

OBJECTIVE: To describe the case of a primary cerebral fibrosarcoma in a child. CLINICAL CASE: A 6-year-old boy presented with a history of headache, drowsiness, vomiting and seizures. He was referred to our institution and died shortly upon arrival to the ER. The autopsy revealed a large left frontoparietal mass with histopathologic features characteristic of fibrosarcoma. Immunohistochemical and ultrastructural studies allowed the exclusion of other mimickers such as meningiomas, and neoplasms of glial or neuronal origin. No other growths were found in the CNS or in other parts of the body. CONCLUSIONS: Brain fibrosarcoma is an exceedingly uncommon tumor. Only 41 cases have been reported to date. The diagnosis of fibrosarcoma must be based on the identification of a predominant herringbone architectural pattern, and immunohistochemical features, although the latter are of limited diagnostic value, its importance being that they facilitate the exclusion of other entities considered in the differential diagnosis.

Penile cancer associated with so-called low-risk human papilloma virus. Report of five cases from rural Venezuela.

Penile cancer is uncommon in western countries. It has been related to human papilloma virus (HPV) types 16 and 18. We describe five cases of carcinoma of the penis in men from a rural Venezuelan town that were related to HPV types 6, 11, 53, which represent a rather low risk for cancer.

T4-thyrotoxicosis.

A 41-year-old man had thyrotoxicosis, diffuse goiter, exophthalmos, high titer of antithyroglobulin antibodies but undetectable long-acting thyroid stimulator. Initially, he had both elevated serum thyroxine (T4) and reverse triiodothyronine (rT3) levels, but normal serum triiodothyronine (T3) and free triiodothyronine (FT3) levels and 24-hour radioactive iodine uptake. Observations prior to radioactive iodine therapy uptake. Observations prior to radioactive iodine therapy showed a persistently normal T3 level in spite of development of atrial fibrillation. Iodine excess was not present, nor were any drugs or systemic illnesses that cause preferential monodeiodination of T4 to rT3 instead of T3. The data support the concept that (1) thyroxine is not just a prohormone for triiodothyronine but is metabolically active itself; (2) Graves' disease can be a cause of T4-thyrotoxicosis. We conclude that a normal serum T3 level does not rule out thyrotoxicosis.

Transient diabetes insipidus with elevated serum osmolarity associated with 'benign' febrile illness.

A 38-year-old physician developed polyuria and hypodipsia four days after the onset of an upper respiratory tract infection. Subsequent investigation showed a concentration defect with dehydration that partially corrected with vasopressin injection (Pitressin) administration compatible with partial central diabetes insipidus (DI). Skull roentgenograms, EEG, and lumbar puncture were normal. The polyuria and hypodipsia slowly resolved without treatment. Normal urinary concentration ability was achieved by the 48th day, but a residual elevation in serum osmolarity persisted for one year. Review of the literature failed to show previous documentation of transient DI with elevated serum osmolarity from an acute, febrile illness. The mechanism is speculative, but may be related to a subclinical encephalitis. The true frequency of this syndrome and its relationship to the frequent observation of transient polydipsia and polyuria in "benign" febrile illness remains to be determined.

Treatment guidelines for patients with thyroid nodules and well-differentiated thyroid cancer. American Thyroid Association.

A set of minimum clinical guidelines for use by primary care physicians in the evaluation and management of patients with thyroid nodules or thyroid cancer was developed by consensus by an 11-member Standards of Care Committee (the authors of the article) of the American Thyroid Association, New York, NY. The participants were selected by the committee chairman and by the president of the American Thyroid Association based on their clinical experience. The committee members represented different geographic areas within the United States, to reflect different practice patterns. The guidelines were developed based on the expert opinion of the committee participants, as well as on previously published information. Each committee participant was initially assigned to write a section of the document and to submit it to the committee chairman, who revised and assembled the sections into a complete draft document, which was then circulated among all committee members for further revision. Several of the committee members further revised and refined the document, which was then submitted to the entire membership of the American Thyroid Association for written comments and suggestions, many of which were incorporated into a final draft document, which was reviewed and approved by the Executive Council of the American Thyroid Association.

The effect of dietary fiber supplementation in man. II. Alteration in fecal physiology and bacterial flora.

Fecal weight and water content and fecal quantitative and qualitative bacterial studies were compared on six volunteer subjects during regular diet periods and when on 5.4 g of diet fiber supplementation. There was a statistical mean stool weight increase for the group from 103 +/- 40 g to 226 +/- 90 g. The water content of the stool remained constant under the diet conditions of this study. The total anaerobic counts increased significantly while the subjects were on the high fiber diet. Trends in bacterial genus changes appeared but were not significant and total aerobic counts were stable.

Low fiber content of Connecticut diets.

Recent theories have postulated that low fiber diets are related to colon cancer and diverticulosis, and to atherosclerosis. These theories are based on British and African diet history information. There has been no recent assessment of fiber intake in an area of high incidence of colonic disease in the United States. Using recall diet histories in subjects with no disease and with colon disease, and correcting our data to account for any loss in recall history, we find a low daily fiber intake in all 21 subjects evaluated, mean 3.5 g, range 1.6 to 11 g. There was no statistical difference in intake among patients with or without colon disease. The data agree with the British findings. Since the incidence of the diseases in question is not uniform in the United States it is suggested that diet surveys are needed in areas where colon carcinoma is of low incidence.

Pure follicular thyroid carcinoma: impact of therapy in 214 patients.

Records of 214 patients with pure follicular thyroid carcinoma were reviewed in detail to evaluate the circumstances of initial presentation and therapy on ultimate outcome. Mean followup was 8.8 yr. The only deaths directly attributable to the thyroid carcinoma occurred in patients with distant metastases at the time of presentation. There were 20 recurrences in the 182 patients considered free of disease after initial therapy. Overall recurrence rate was not affected by the presence of positive cervical nodes or extent of thyroid surgery. Postoperative recurrence rate was decreased by both radioiodine and thyroid-hormone therapy. Extensive histologic invasion of the capsule of the nodule and thyroid appeared to be associated with an increase in recurrence rate. Postoperative thyroid-hormone is required therapy in all patients with pure follicular thyroid carcinoma. Radioiodine therapy is indicated in patients with extensive invasion and we favor its use in all patients.

The increasing incidence of hypothyroidism within one year after radioiodine therapy for toxic diffuse goiter.

Patients treated with 10 mCi of I-131 for toxic diffuse goiter in the period January 1974--June 1976 were evaluated for development of hypothyroidism. Fifty percent were hypothyroid within 3 mo and 69% within 1 yr of treatment. Our data suggest that there is a higher incidence of hypothyroidism after standard doses of I-131 in the 1970s as contrasted with treatment groups in the 1950s and 1960s. The pathophysiology of this increased incidence is not known with certainty; however, infrequent use of thionamide medication, together with recent increases in dietary iodine, may render the gland more radiosensitive.

Theoretical analysis of the growth mode for thin metallic films on oxide substrates

We show how the growth mode of a thin metallic film on an insulating substrate can be predicted theoretically by combining thermodynamic considerations with ab initio calculations for ordered metal/insulator interfaces at low coverage. Our approach is illustrated by calculations for Ag film deposited on an MgO substrate. Ab initio calculations predict high mobility of adsorbed Ag atoms on MgO, even at low temperatures, which greatly aids their aggregation.

Epiglottitis following preparation for allogeneic bone marrow transplantation.

We describe a 7-year-old boy who developed acute, airway-threatening, non-infectious epiglottitis following high-dose cytosine arabinoside and total body irradiation preparative regimen for allogeneic BMT. Unlike gastrointestinal symptoms and oropharyngeal mucositis, acute epiglottitis is a previously unreported early complication following allogeneic BMT preparation. The pathogenesis of epiglottitis in our patient was presumably multifactorial, resulting from the combination of chemotherapy and irradiation. We recommend that this diagnosis be considered in the differential diagnosis of patients with significant upper airway symptoms following BMT preparation.

Maternal mortality in New York City, 1981-1983.

The maternal mortality ratio in New York City during the 3-year period of 1981-1983 was 36.1 deaths per 100,000 live births. Eight (7%) of 120 deaths occurred more than 42 days after termination of the pregnancy. Eighteen (15%) of the cases involved white, non-Hispanic women, 66 (55%) were black, and 32 (27%) were Hispanic. Fifty-seven deaths were associated with cesarean delivery, although most of these could not be attributed to the mode of delivery. Sixty-six (55%) of the deaths were classified as direct maternal deaths. The age ranged from 16-44 years, with 83 (69%) of the women aged 20-34, 11 (9%) 19 or less, and 26 (22%) aged 35 or older. Increasing age and parity were associated with greater maternal mortality ratios. The leading causes of pregnancy-associated mortality were found to be ectopic pregnancy, pulmonary embolism, anesthetic complications, amniotic fluid embolism, intracranial hemorrhage, hypertensive diseases of pregnancy, infection, and cardiac disease. Abortion-related mortality was about nine times less than the maternal mortality ratio, and the cesarean death-to-case rates could be considered roughly comparable to overall maternal mortality.

Deaths from ectopic pregnancy, United States, 1979 to 1980.

During the 1970s in the United States, the number of hospitalizations for ectopic pregnancy increased more than twofold, and ectopic pregnancy emerged as a leading cause of maternal mortality. All known deaths from ectopic pregnancy in the United States from January 1, 1979, to December 31, 1980, were investigated by the Centers for Disease Control to determine incidence, characteristics, and risk factors for fatal ectopic pregnancy. Deaths were reported primarily by state health departments; numbers and characteristics of women who had ectopic pregnancies were obtained through the National Hospital Discharge Survey of the National Center for Health Statistics. Eighty-six deaths were confirmed among an estimated 102,100 cases of ectopic pregnancy, for an overall death-to-case rate of 0.8 per 1000. Women of black and other races had a relative risk of death 3.2 times that of white and Hispanic women. Continued surveillance should help to reduce the number of deaths through the education of women and health professionals.

Antepartum pituitary infarction.

Antepartum pituitary infarction occurs only in insulin-dependent diabetic patients. It is manifested by severe headache, followed by decreasing insulin requirements. Delivery is frequently premature, with high fetal wastage and increased maternal mortality. During the puerperium, the first manifestation of pituitary deficiency, other than a lower insulin requirement than would be expected, is failure to lactate. Subsequent evaluation of pituitary function reveals variable deficiencies with loss of growth hormone and gonadotropins being most frequent. This case is the eighth report of this entity, and it represents the first patient to survive a pituitary infarction prior to the third trimester of pregnancy. Recognition of this syndrome is critical in order to ensure that the mother's health and the viability of the offspring be preserved.

Ectopic pregnancy mortality, United States, 1979 to 1980: clinical aspects.

Ectopic pregnancy has recently become a major cause of maternal mortality in the United States. Despite its increasing public health impact, relatively little is known about the clinical epidemiology of this condition. Therefore, the authors investigated all reported deaths from ectopic pregnancy in the United States occurring in 1979 and 1980, to determine characteristics of, and risk factors for, fatal ectopic pregnancy. Most women (85%) died from hemorrhage. Abdominal and interstitial implantations were more likely to become symptomatic later in gestation and to be fatal than were tubal implantations. Of those deaths for which circumstances were known, more prompt diagnosis and treatment of ectopic pregnancy by health professionals might have prevented one-half of the deaths. One-third of the deaths might have been prevented if the women had notified or visited a physician more promptly after the onset of symptoms. Timelier action by women and health professionals could reduce ectopic pregnancy mortality.