Ga droplet morphology on GaAs(001) studied by Lloyd's mirror photoemission electron microscopy.

We apply Lloyd's mirror photoemission electron microscopy (PEEM) to study the surface shape of Ga droplets on GaAs(001). An unusual rectangular-based droplet shape is identified and the contact angle is determined in situ. It is shown that quenching does not appreciably affect droplet shape and ex situ measurements of the contact angle by atomic force microscopy are in good agreement with Lloyd's mirror PEEM. Extension of Lloyd's mirror technique to reconstruct general three-dimensional (3D) surface shapes and the potential use of synchrotron radiation to improve vertical resolution is discussed.

Imaging surface topography using Lloyd's mirror in photoemission electron microscopy.

We use Lloyd's mirror to modulate electron photoemission in photoemission electron microscopy. This results in the projection of Lloyd's fringes on to three-dimensional (3D) surface objects. An iterative reconstruction method is used to correct for distortions in the fringe pattern due to the cathode immersion lens, thereby providing a quantitative interpretation of surface shape. It is therefore possible to extract 3D height information directly from a two-dimensional, plan-view image. The technique is of sufficient intensity and contrast to study real-time changes in surface topography and we apply the method to study unusual contact-line dynamics during the reactive wetting of metal droplets.

Treatment of coronary artery disease in hemodialysis patients: PTCA vs. stent.

This retrospective study examined the utilization of coronary stent placement versus PTCA in hemodialysis patients with obstructive coronary disease. Prior studies have demonstrated suboptimal results with PTCA owing primarily to high rates of restenosis. We identified 19 hemodialysis patients who received a percutaneous coronary intervention who were matched with individuals without renal failure undergoing same vessel revascularization. Our study found that 71% of hemodialysis patients receiving PTCA had a recurrent cardiac event defined by subsequent angina, myocardial infarction, or cardiac death. At follow-up, 30% of patients who received stent placement had recurrent cardiac events. Intracoronary stent placement is both safe and feasible and produces more favorable clinical outcomes in the management of coronary disease in hemodialysis patients.

Adrenocortical activity in at-risk and normally developing adolescents: individual differences in salivary cortisol basal levels, diurnal variation, and responses to social challenges.

The purpose of this study was to examine adrenocortical activity (basal, diurnal variation, and responses to social stressors) in adolescents at risk for psychopathology. Salivary cortisol levels were examined in normally developing and at-risk youth with internalizing and externalizing symptoms ranging from subclinical to clinical levels. Adolescents showed expected patterns of diurnal variation, with high early morning cortisol levels and a pattern of decline throughout the day. Females showed higher midday and late afternoon levels than males, and these patterns interacted with risk status. Internalizing problems sometimes were associated with gradual rather than steep declines in basal cortisol production. Both immediate and delayed cortisol reactivity to a social performance stressor were associated with internalizing symptoms. There was no evidence of relations between externalizing problems and underarousal of the hypothalamic-pituitary-adrenal (HPA) system. These and other results suggest that gender is an important moderating factor linking psychopathology. development, and context with HPA axis functioning in adolescence.

Selective photon-stimulated desorption of hydrogen from GaAs surfaces.

Photon-stimulated desorption of H(+) from hydrogenated GaAs (110) and (100) surfaces was studied as a function of photon energy. Distinct peaks, observed around As 3d core-level binding energy for desorption from the GaAs (100) surface and in the As 3d and Ga 3p region for desorption from the GaAs (110) surface, show a striking similarity with the fine structure (spin-orbit splitting) measured in the photoemission from As 3d and Ga 3p levels. These results provide clear evidence for direct desorption processes and represent a basis for selective modification of hydrogenated GaAs surfaces.

Recent advances in dobutamine stress echocardiography.

Dobutamine stress echocardiography (DSE) is a reliable cardiac risk stratifier that has widespread applicability because of its clinical accuracy and cost effectiveness. Dobutamine has positive inotropic and chronotropic effects and is commonly used in patients who cannot exercise or achieve an adequate heart rate response with exercise. Recently available long-term results from several independent clinical trials, combined with enhancements in image quality, have improved the ability to detect significant coronary artery disease and determine myocardial viability. Dobutamine stress echocardiography has an excellent safety profile with clinical results superior to regular exercise electrocardiography and comparable with exercise echocardiography and radionucleotide perfusion stress imaging. Low-dose dobutamine response can accurately predict dysfunctional yet viable myocardial regions that may improve with revascularization. Clinical studies are now available refining the common use of DSE preoperatively in female patients with valvular disease, as well as in the emergency department. Dobutamine stress echocardiography does have some limitations in discriminating particular regions of ischemia when multiple ventricular segments are involved and when the imaging is suboptimal. It can be applied using minimal additional resources in an otherwise functioning echocardiography laboratory and, with appropriate training, can result in clinical results comparable with those of large-scale multicenter trials. Ongoing improvements in technology and the development of new reagents such as myocardial contrast agents hold promise for further advancement in the near future.

A sequential developmental field defect of the vertebrae, ribs, and sternum, in a young woman of the 12th century AD.

Changes in the vertebral column are often noted in skeletal material. Descriptions of these anomalies are often lacking, and their developmental origins are not often discussed. The skeleton of a young woman from the medieval cemetery of Tirup, in Denmark, has multiple defects of the axial skeleton, including extra thoracic and lumbar vertebrae, border shifting, extra ribs, block vertebra, and deformed sternum. This case study is particularly interesting because of the number and diversity of anomalies seen; the rarity of these defects, even in living populations; and her survival to adult age. Careful analysis of the bones and use of the morphogenetic method of determining development stages has led to the conclusion that the initial defect probably occurred very early in development, during blastogenesis, with the initial development of at least two extra somitomeres in the paraxial mesoderm. These extra elements in turn led to problems in union and differentiation, and later chondrification and ossification of the vertebra. The malformations of the vertebrae also induced changes in the ribs and sternum. The initial error of segmentation is identified as a developmental field defect, and the cascade of anomalies seen is a developmental sequence caused by the initial field defect. The genetic and environmental causes of developmental field defects are reviewed.

The association of the combination of sumatriptan and methysergide in myocardial infarction in a premenopausal woman.

Acute myocardial infarction occurred in a 43 year-old premenopausal woman with controlled hypertension and no known coronary artery disease following the use of the antimigraine medications sumatriptan succinate injectable form and methysergide maleate. The use of sumatriptan is contraindicated within 24 hours of using ergotamine or ergotamine-type medications such as methysergide. This contraindication is based on the theoretical possibility of prolonged vasospasm with the combined use. Methysergide is primarily a serotonin type 2 (5-HT2) antagonist, although it does act as a partial agonist at 5-HT1 receptors. It is believed that a major component of coronary artery vasospasm is possibly due to 5-HT supersensitivity mediated by 5-HT1Dbeta receptor activation. Drugs that selectively stimulate the 5-HT(D) receptors, such as sumatriptan, are potentially hazardous in people with underlying coronary artery disease, and agents with additional agonistic properties at these receptors may potentiate this effect. Physicians should be warned to inquire about prior 24-hour medication use before prescribing antimigraine medication.

Validity of electrocardiographic estimates of left ventricular hypertrophy and mass in African Americans (The Charleston Heart Study).

The Cornell voltage criteria and the Novacode computer model for estimating left ventricular mass were compared to echocardiographic left ventricular mass in African Americans from the Charleston Heart Study. The diagnostic accuracy of these electrocardiographic models compared with the echocardiogram is similar to the previous study in whites.

Individual differences in emotion regulation and behavior problems in preschool children.

Emotion regulation (ER) was assessed during a negative mood induction in 79 preschoolers who varied in degree of behavior problems. Facial expressivity during the induction was used to identify 3 ER groups: inexpressive, modulated expressive, and highly expressive. Group differences in ER were significantly related to heart rate and skin conductance. Inexpressive preschoolers had the highest heart rate, lowest vagal tone, and smallest autonomic nervous system (ANS) change during the induction. Highly expressive preschoolers had the slowest heart rate, highest vagal tone, and largest ANS change. The inexpressive and highly expressive groups had more externalizing symptoms than the modulated group at preschool age and at follow-up at the end of 1st grade. Inexpressive preschoolers appeared to have more depressed and anxious symptoms at follow-up.

Steroid-induced osteonecrosis of the humeral head.

Steroid-induced osteonecrosis is a disease of modern medicine. Prevention remains the hallmark of management; however, as long as there are medical conditions requiring steroid therapy, osteonecrosis will remain a problem. An understanding of the pathophysiology, in addition to the clinical and radiographic manifestations of this disease process, will aid the physician in the unique challenge of diagnosing and treating osteonecrosis of the humeral head.

Effect of catheter positioning on the variability of measured gradient in aortic stenosis.

The purpose of this study was to quantify the variation in measured aortic valve gradient and calculated aortic valve area when different techniques of cardiac catheterization were utilized. Hemodynamic assessment of aortic stenosis severity requires an accurately determined pressure gradient. In aortic stenosis, the presence of intraventricular pressure gradients and downstream pressure recovery within the aorta means that a range of aortic valve gradients could be measured in a given patient depending upon catheter position and measurement technique. To quantify the degree of variation in measured gradient and calculated aortic valve area, we generated transvalvular gradients by nine different techniques in 15 patients (11 men, 4 women; 29-86 years old). Patients were divided into those with severe aortic stenosis (aortic valve area < or = 0.6 cm2, n = 6) and those with moderately severe aortic stenosis (aortic valve area 0.61-0.90 cm2, n = 9). Considerable variation in measured gradient and calculated aortic valve area was observed. The maximum variation in gradient was similar in severe and moderately severe aortic stenosis groups (33 mm Hg. vs. 32 mm Hg., p = NS). However, the variation in gradient as a percent of maximum gradient was greater (P < 0.05) in the moderately severe aortic stenosis group. The maximum variation in calculated aortic valve area was 0.1 cm2 in the severe group and 0.3 cm2 in the moderately severe group (P < 0.01). An intraventricular gradient, present in 13 of 15 (87%) patients, was partially responsible for the variation in pressure gradient measurement and calculated aortic valve area.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac valvular disease and stroke.

Cerebrovascular accidents secondary to thromboembolic complications of native valve disease as well as prosthetic valves continue to be a major medical problem. The role of anticoagulation in various abnormalities is discussed in this article.