Validation of implosion modeling through direct-drive shock timing experiments at the National Ignition Facility

Precise modeling of shocks in inertial confinement fusion implosions is critical for obtaining the desired compression in experiments. Shock velocities and postshock conditions are determined by laser-energy deposition, heat conduction, and equations of state. This paper describes experiments at the National Ignition Facility (NIF) [E. M. Campbell and W. J. Hogan, Plasma Phys. Control. Fusion 41, B39 (1999)10.1088/0741-3335/41/12B/303] where multiple shocks are launched into a cone-in-shell target made of polystyrene, using laser-pulse shapes with two or three pickets and varying on-target intensities. Shocks are diagnosed using the velocity interferometric system for any reflector (VISAR) diagnostic [P. M. Celliers et al., Rev. Sci. Instrum. 75, 4916 (2004)0034-674810.1063/1.1807008]. Simulated and inferred shock velocities agree well for the range of intensities studied in this work. These directly-driven shock-timing experiments on the NIF provide a good measure of early-time laser-energy coupling. The validated models add to the credibility of direct-drive-ignition designs at the megajoule scale.

Structure and density of silicon carbide to 1.5 TPa and implications for extrasolar planets

There has been considerable recent interest in the high-pressure behavior of silicon carbide, a potential major constituent of carbon-rich exoplanets. In this work, the atomic-level structure of SiC was determined through in situ X-ray diffraction under laser-driven ramp compression up to 1.5 TPa; stresses more than seven times greater than previous static and shock data. Here we show that the B1-type structure persists over this stress range and we have constrained its equation of state (EOS). Using this data we have determined the first experimentally based mass-radius curves for a hypothetical pure SiC planet. Interior structure models are constructed for planets consisting of a SiC-rich mantle and iron-rich core. Carbide planets are found to be ~10% less dense than corresponding terrestrial planets.

Metastability of Liquid Water Freezing into Ice VII under Dynamic Compression

The ubiquitous nature and unusual properties of water have motivated many studies on its metastability under temperature- or pressure-induced phase transformations. Here, nanosecond compression by a high-power laser is used to create the nonequilibrium conditions where liquid water persists well into the stable region of ice VII. Through our experiments, as well as a complementary theoretical-computational analysis based on classical nucleation theory, we report that the metastability limit of liquid water under nearly isentropic compression from ambient conditions is at least 8 GPa, higher than the 7 GPa previously reported for lower loading rates.

Equation of State of CO_{2} Shock Compressed to 1 TPa

Equation-of-state (pressure, density, temperature, internal energy) and reflectivity measurements on shock-compressed CO_{2} at and above the insulating-to-conducting transition reveal new insight into the chemistry of simple molecular systems in the warm-dense-matter regime. CO_{2} samples were precompressed in diamond-anvil cells to tune the initial densities from 1.35  g/cm^{3} (liquid) to 1.74  g/cm^{3} (solid) at room temperature and were then shock compressed up to 1 TPa and 93 000 K. Variation in initial density was leveraged to infer thermodynamic derivatives including specific heat and Gruneisen coefficient, exposing a complex bonded and moderately ionized state at the most extreme conditions studied.

Probing the Solid Phase of Noble Metal Copper at Terapascal Conditions

Ramp compression along a low-temperature adiabat offers a unique avenue to explore the physical properties of materials at the highest densities of their solid form, a region inaccessible by single shock compression. Using the National Ignition Facility and OMEGA laser facilities, copper samples were ramp compressed to peak pressures of 2.30 TPa and densities of nearly 30  g/cc, providing fundamental information regarding the compressibility and phase of copper at pressures more than 5 times greater than previously explored. Through x-ray diffraction measurements, we find that the ambient face-centered-cubic structure is preserved up to 1.15 TPa. The ramp compression equation-of-state measurements shows that there are no discontinuities in sound velocities up to 2.30 TPa, suggesting this phase is likely stable up to the peak pressures measured, as predicted by first-principal calculations. The high precision of these quasiabsolute measurements enables us to provide essential benchmarks for advanced computational studies on the behavior of dense monoatomic materials under extreme conditions that constitute a stringent test for solid-state quantum theory. We find that both density-functional theory and the stabilized jellium model, which assumes that the ionic structure can be replaced by an ionic charge distribution by constant positive-charge background, reproduces our data well. Further, our data could serve to establish new international secondary scales of pressure in the terapascal range that is becoming experimentally accessible with advanced static and dynamic compression techniques.

Shock Compression of Liquid Deuterium up to 1 TPa

We present laser-driven shock compression experiments on cryogenic liquid deuterium to 550 GPa along the principal Hugoniot and reflected-shock data up to 1 TPa. High-precision interferometric Doppler velocimetry and impedance-matching analysis were used to determine the compression accurately enough to reveal a significant difference as compared to state-of-the-art ab initio calculations and thus, no single equation of state model fully matches the principal Hugoniot of deuterium over the observed pressure range. In the molecular-to-atomic transition pressure range, models based on density functional theory calculations predict the maximum compression accurately. However, beyond 250 GPa along the principal Hugoniot, first-principles models exhibit a stiffer response than the experimental data. Similarly, above 500 GPa the reflected shock data show 5%-7% higher compression than predicted by all current models.

Diabetes in African Americans

African Americans have a high risk for type 2 diabetes. Genetic traits, the prevalence of obesity, and insulin resistance all contribute to the risk of diabetes in the African American community. African Americans have a high rate of diabetic complications, because of poor glycaemic control and racial disparities in health care in the USA. African Americans with diabetes may have an atypical presentation that simulates type 1 diabetes, but then their subsequent clinical course is typical of type 2 diabetes. Culturally sensitive strategies, structured disease management protocols, and the assistance of nurses, diabetic educators, and other health care professionals are effective in improving the outcome of diabetes in the African American community.

Meningioma metastatic to thyroid gland

OBJECTIVE

To describe the first reported case of meningioma metastasizing to and completely infiltrating the thyroid gland.

METHODS

We present a detailed case report, including radiographic, histologic, and immunostaining findings, in a patient with an atypical meningioma who had a progressively enlarging thyroid mass that proved to be a metastatic meningioma.

RESULTS

A 49-year-old man had a meningioma in the parieto-occipital region that had spread locally to the scalp and bone by the time of surgical resection. Local recurrence during the following year prompted repeated surgical resection, tumor embolization, radiotherapy, and chemotherapy. Despite aggressive therapy, the tumor progressed. A thyroid mass was first noted 2 years after the meningioma was diagnosed. Enlargement of the mass caused airway obstruction, necessitating an emergency thyroidectomy. Histologic examination of the thyroidectomy specimen showed that the thyroid gland had been extensively replaced by metastatic meningioma.

CONCLUSION

To our knowledge, this is the first reported case of metastatic meningioma extensively infiltrating the thyroid gland. This case report expands the spectrum of tumors that metastasize to the thyroid gland.

HbA1c predicts length of stay in patients admitted for coronary artery bypass surgery

Diabetes mellitus is associated with coronary artery disease, and diabetic patients are frequently referred for coronary bypass graft surgery. It is well known that HbA1c, which reflects long-term glycemic control, is related to diabetic morbidity and mortality. It is not known whether HbA1c is related to postoperative length of stay among patients who undergo coronary artery bypass surgery. The authors evaluated 135 patients who underwent bypass surgery at the Westchester Medical Center (Valhalla, NY). HbA1c was measured in all patients preoperatively; a value of 7% or greater was used as a threshold for uncontrolled hyperglycemia. A postoperative length of stay of 6 days or more was used as the cutoff for an extended length of stay. Linear regression was used to assess the relationship between HbA1c, adjusted for age, and length of stay in days. Logistic regression, with length of stay a binary variable <6, > or =6 days, was used to assess the accuracy of HbA1c <7%, > or =7%, adjusted for age, in predicting length of stay. An HbA1c of 7% or greater was found to be a strong predictor of a length of stay of 6 days or longer. These data suggest that HbA1c can be used as a surrogate marker for cardiac and noncardiac morbidity that prolongs hospitalization after coronary artery bypass surgery.

Diabetes mellitus in the elderly

Diabetes mellitus is prevalent among the elderly. Although the principles of management of diabetes are fundamentally the same in both the young and elderly, many aspects of the disease and its manifestations are unique to the elderly. Older patients may have atypical presentations of diabetes. Numerous factors may impair adequate nutrition and dietary and exercise compliance in the elderly. Pharmacologic therapy, with either sulfonylureas or insulin, entails a particular risk for hypoglycemia among the elderly, who are more susceptible to hypoglycemia and are more likely to have neuroglycopenic symptoms. Diabetic hyperosmolar coma occurs predominantly in the older type II diabetic population. It requires aggressive hydration and insulin therapy, but most patients can ultimately be managed without insulin. The macrovascular complications (coronary and peripheral vascular disease) are the major source of morbidity and mortality among elderly diabetics, but microvascular complications (nephropathy, retinopathy, neuropathy) also occur and often respond to a variety of therapeutic interventions.

The physiologic evaluation of the lung resection candidate

The evaluation of patients with lung cancer should include an assessment of physiologic risk. This assessment begins with simple pulmonary function studies such as spirometry and diffusing capacity. Abnormalities of these test results should stimulate further assessment with quantitative lung scanning and noninvasive exercise testing. Resection should not be recommended in patients with extremely high risk; however, because of the poor prognosis, patients must be integrally involved in the decision to not resect the lung cancer.

Empty sella turcica in intracranial sarcoidosis. Pituitary insufficiency, primary polydipsia, and changing neuroradiologic findings

A 37-year-old man with visual loss was found to have hypopituitarism and primary polydipsia associated with sarcoidosis. Neuroradiologic studies demonstrated a dramatic evolution of CNS lesions, including a left thalamic infarct, an enhancing suprasellar mass, and ultimately an empty sella turcica. The patient has been clinically stable in spite of these changes. This case is likely to be the first reported of CNS sarcoidosis with an empty sella turcica documented by computed tomography.

A variant of adrenomyeloneuropathy with hypothalamic-pituitary dysfunction and neurologic remission after glucocorticoid replacement therapy

Adrenomyeloneuropathy is a syndrome comprising spastic paraparesis, polyneuropathy, primary adrenocortical insufficiency and variable hypogonadism. We describe a 32 year old man who presented with contractures, peripheral neuropathy, primary adrenocortical insufficiency adn secondary hypogonadism. Abnormal responses of growth hormone, gonadotropins, prolactin and thyrotropin to provocative stimuli were found, without radiographic evidence of a pituitary or hypothalamic lesion. Almost complete recovery from the neurologic abnormalities occurred with glucocorticoid replacement therapy. The clinical features of this patient support a diagnosis of adrenomyeloneuropathy. The hypothalamic-pituitary dysfunction extends the clinical features of this patient support a diagnosis of adrenomyeloneuropathy. The hypothalamic-pituitary dysfunction extends the clinical spectrum of this disease. Remission of the paraparesis coincident with glucocorticoid replacement has not been reported previously.

Effects of dietary composition on adipose tissue hexokinase-II and glucose utilization in normal and streptozotocin-diabetic rats

The control of adipose tissue hexokinase isoenzymes in response to altered dietary composition was investigated. Rats that were fasted and then refed carbohydrate-free diets increased their HK-II activity in epididymal fat pads above the level in fasted animals. However the ultimate activity of HK-II achieved during refeeding with seven diets of varying composition was dependent mainly on dietary carbohydrate; the effect of dietary carbohydrate overcame poor growth due to protein deficiency or decreased food intake. Fat pads from animals fed for three weeks from weaning with 19 per cent protein diets showed a marked increase in HK-II on 51 per cent carbohydrate over those on a carbohydrate-free diet but no further increase on 81 per cent carbohydrate. However, adipocytes from rats on 81 per cent carbohydrate had significantly higher HK-II than those from rats on 51 per cent carbohydrate.

In streptozotocin-diabetic rats there was no difference in adipose tissue HK-II between rats on 19 per cent protein-51 per cent carbohydrate and those on 19 per cent protein carbohydrate-free diets. Treatment of diabetic rats with 3 U. lente insulin daily brought HK-II into the range for normal rats, but once again there was no difference between the two diets. The treated rats showed marked weight gain but were still hyperglycemie.

Adipocytes from rats on the 19 per cent protein carbohydrate-free diet showed lower HK-II and glucose conversion to CO2 and triglyceride than adipocytes from rats on the 51 per cent carbohydrate diet. There was a high correlation of HK-II to both pathways of glucose utilization on both diets. However, the slope of the regression line of triglyceride production on HK-II was much lower on the carbohydrate-free than on the basal diet. Adipocytes from rats on the 81 per cent carbohydrate diet had HK-II activity and glucose utilization that fell within the 95 per cent confidence limits for the relationship derived from adipocytes from rats on the 51 per cent carbohydrate diet. Values for glucose utilization in adipocytes from treated diabetic rats on the carbohydrate-free diet were above the expected range for this diet for both CO2 and triglyceride production; CO2 production was also above the expected range for diet in treated diabetic rats on the 51 per cent carbohydrate diet. Glucose conversion to both end products was higher for a given level of HK-II in the treated diabetic animals on the 51 per cent carbohydrate diet than on the carbohydrate-free diet.

These data indicate that diet has a major effect on HK-II that is probably mediated by carbohydrate and is dependent on insulin. Although there appears to be a relationship between HK-H and glucose utilization in a given diet-and-treatment group, there is a departure from the normal relationship in adipocytes from rats on a high-fat carbohydrate-free diet or from partially treated diabetic rats.