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.

Establishing gold and platinum standards to 1 terapascal using shockless compression.

New techniques are advancing the frontier of high-pressure physics beyond 1 terapascal, leading to new discoveries and offering stringent tests for condensed-matter theory and advanced numerical methods. However, the ability to absolutely determine the pressure state remains challenging, and well-calibrated pressure-density reference materials are required. We conducted shockless dynamic compression experiments at the National Ignition Facility and the Z machine to obtain quasi-absolute, high-precision, pressure-density equation-of-state data for gold and platinum. We derived two experimentally constrained pressure standards to terapascal conditions. Establishing accurate experimental determinations of extreme pressure will facilitate better connections between experiments and theory, paving the way toward improving our understanding of material response to these extreme conditions.

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.

Online symptom checker diagnostic and triage accuracy for HIV and hepatitis C.

We sought to address the prior limitations of symptom checker accuracy by analysing the diagnostic and triage feasibility of online symptom checkers using a consecutive series of real-life emergency department (ED) patient encounters, and addressing a complex patient population - those with hepatitis C or HIV. We aimed to study the diagnostic and triage accuracy of these symptom checkers in relation to an emergency room physician-determined diagnosis. An ED retrospective analysis was performed on 8363 consecutive adult patients. Eligible patients included: 90 HIV, 67 hepatitis C, 11 both HIV and hepatitis C. Five online symptom checkers were utilised for diagnosis (Mayo Clinic, WebMD, Symptomate, Symcat, Isabel), three with triage capabilities. Symptom checker output was compared with ED physician-determined diagnosis data in regards to diagnostic accuracy and differential diagnosis listing, along with triage advice. All symptom checkers, whether for combined HIV and hepatitis C, HIV alone or hepatitis C alone had poor diagnostic accuracy in regards to Top1 (<20%), Top3 (<35%), Top10 (<40%), Listed at All (<45%). Significant variations existed for each individual symptom checker, as some appeared more accurate for listing the diagnosis in the top of the differential, vs. others more apt to list the diagnosis at all. In regards to ED triage data, a significantly higher percentage of hepatitis C patients (59.7%; 40/67) were found to have an initial diagnosis with emergent criteria than HIV patients (35.6%; 32/90). Symptom checker diagnostic capabilities are quite inferior to physician diagnostic capabilities. Complex patients such as those with HIV or hepatitis C may carry a more specific differential diagnosis, warranting symptom checkers to have diagnostic algorithms accounting for such complexity. Symptom checkers carry the potential for real-time epidemiologic monitoring of patient symptoms, as symptom entries and subsequent symptom checker diagnosis could allow health officials a means to track illnesses in specific patient populations and geographic regions. In order to do this, accurate and reliable symptom checkers are warranted.

Prevalence of Anxiety Disorders in Hong Kong Chinese Children With ADHD.

OBJECTIVE: This study examined the prevalence and correlates of anxiety disorders in Chinese children with ADHD. METHOD: Overall, 120 children with ADHD aged 6 to 12 years were recruited, and the parent version of computerized Diagnostic Interview Schedule for Children-Version 4 was administrated to their primary caretakers. RESULTS: The prevalence rate of anxiety disorders was 27.5%, which is consistent with the reports of previous Asian and Western studies. Among the children with ADHD and anxiety disorders, more than 50% of them also had comorbid oppositional defiant disorder or conduct disorder (ODD/CD), which yielded an adjusted odds ratio of 3.0 in multivariable analysis for anxiety disorder, with comorbid ODD/CD. In addition, anxiety disorders were positively associated with inattention symptoms in children with both disorders. CONCLUSION: Clinicians should perform screening and careful assessment for anxiety symptoms in children with ADHD, particularly those suffering from comorbid ODD/CD.

Prevalence of motor problems in children with attention deficit hyperactivity disorder in Hong Kong.

INTRODUCTION: Local data on the occurrence of motor problems in children with attention deficit hyperactivity disorder are not available but an understanding of this important issue may enable better planning of medical services. We aimed to determine the prevalence of motor problems in children with attention deficit hyperactivity disorder in a local population. METHODS: In this descriptive cross-sectional study, children aged 6 to 9 years diagnosed with attention deficit hyperactivity disorder over a period of 6 months from 1 July to 31 December 2011 were recruited from the Joint Paediatric and Child Psychiatric ADHD Program in New Territories East Cluster in Hong Kong. Movement Assessment Battery for Children and Developmental Coordination Disorder Questionnaire-Chinese version were used to determine the presence of motor problems. RESULTS: Data from 95 participants were included in the final analysis. The number of children who had no, borderline, or definite motor problems was 63, 15, and 17, respectively. It is estimated that up to one third of local children with attention deficit hyperactivity disorder might have developmental coordination disorder. CONCLUSIONS: Motor problems are common in local children with attention deficit hyperactivity disorder and figures are comparable with those from other parts of the world. Despite the various limitations of this study, the magnitude of the problem should not be overlooked.

Validation of the Developmental, Dimensional and Diagnostic Interview (3Di) Among Chinese Children in a Child Psychiatry Clinic in Hong Kong.

Autism spectrum disorder (ASD) is a disorder with high levels of co-morbidities. The Developmental, Dimensional and Diagnostic Interview (3 Di) is a relatively new instrument designed to provide dimensional as well as categorical assessment of autistic behaviours among children with normal intelligence. Its sound psychometric properties and relatively short administration time make it a versatile instrument. The 3 Di was translated into Chinese (Cantonese) and its applicability among 194 clinic children was examined. Results found excellent reliability and validity, and achieved a sensitivity of 95% and specificity of 77%. It was able to capture the diagnosis of ASD among children presenting with attention deficit hyperactivity disorder. However, although the disorder of ASD is considered universal, the use of a western instrument in a Chinese context should also take note of cultural influences that may impact on the manifestation of its symptoms.

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.