Interface Engineering for Nanoelectronics.

Innovation in the electronics industry is tied to interface engineering as devices increasingly incorporate new materials and shrink. Molecular layers offer a versatile means of tuning interfacial electronic, chemical, physical, and magnetic properties enabled by a wide variety of molecules available. This paper will describe three instances where we manipulate molecular interfaces with a specific focus on the nanometer scale characterization and the impact on the resulting performance. The three primary themes include, 1-designer interfaces, 2-electronic junction formation, and 3-advancing metrology for nanoelectronics. We show the ability to engineer interfaces through a variety of techniques and demonstrate the impact on technologies such as molecular memory and spin injection for organic electronics. Underpinning the successful modification of interfaces is the ability to accurately characterize the chemical and electronic properties and we will highlight some measurement advances key to our understanding of the interface engineering for nanoelectronics.

Hyponatremic seizures secondary to oral water intoxication in infancy: association with commercial bottled drinking water.

In recent years, hyponatremic seizures resulting from water intoxication have been reported in the United States with an increasing frequency that some have likened to an epidemic. Infants of parents living in poverty and uninformed of the risks of feeding fluids other than infant formula to their babies are particularly at risk. Young infants with vomiting and diarrhea are especially prone to developing hyponatremia if fed fluids lacking sufficient sodium, but even those who are otherwise well may develop symptomatic hyponatremia as a result of being fed excess solute-free water. Most often tap water, either in the form of supplemental feedings or overly dilute formula, has been given in excessive amounts over relatively short periods of time. Less frequently, water in other forms such as juice, soda, or tea has been implicated. This report includes the cases of two infants treated at our institution for hyponatremic seizures and water intoxication after being fed with the same bottled drinking water product marketed for use in infants. The medical records of all infants

Exercise-induced changes in plasma potassium and the ventilatory threshold in man.

1. It has been reported that, during incremental exercise testing, the patterns of change in ventilation (VE) and arterial K+ (Ka+) are similar, suggesting that changing Ka+ may lead to the phenomenon of the ventilatory threshold through its action on the peripheral chemoreceptors. 2. Expiratory ventilation, oxygen consumption, CO2 production (VE, VO2, VCO2), arterialized venous PCO2 (Pav, CO2; see Methods), pH (pHav), K+ (Kav+) and lactate were measured during incremental exercise tests undertaken by six normal male subjects under control conditions and during lactic acidosis following severe exercise (experimental trial). 3. A ventilatory threshold, associated with a period of isocapnic buffering, was observed under both control and experimental conditions. During the control trial, plots of Kav+ against VO2 showed an inflexion close to the ventilatory threshold. Throughout the experimental trial Kav+ rose linearly relative to VO2. In both control and experimental trials Kav+ concentrations were similar at the ventilatory threshold. 4. These results suggest that the pattern of change of Ka+ cannot account for the phenomenon of the ventilatory threshold. The possibility that the peripheral chemoreceptor response is non-linear above a critical value of Ka+ requires further investigation.

Effects of lung reduction on rheotactic performance in amphibian larvae.

In this study we test the hypothesis that lung reduction in amphibians is a larval adaptation to reduce buoyancy and facilitate rheotaxis in lotic environments. Larvae of the spotted salamander Ambystoma maculatum (family Ambystomatidae) were raised from eggs with (= control) and without (= experimental) access to the air-water interface. The experimental larvae developed significantly smaller and more solidified lungs than the controls. Although mean snout-vent length did not differ between the control and experimental groups, the latter had a significantly greater mean body mass, indicating greater specific gravity in experimental versus controls. To evaluate rheotactic behavior, larvae were subjected to a water current in an artificial stream. The distance and time required to establish a purchase on the stream bottom were recorded. Although the times did not differ, the distances displaced downstream were significantly less in experimental than in control larvae. We conclude that lung reduction and solidification reduce buoyancy and enhance rheotactic ability in salamander larvae. These findings suggest that lunglessness in plethodontid salamanders evolved as an adaptation to stream environments.

Use of arterialized venous blood sampling during incremental exercise tests.

Close agreement between arterialized venous and arterial pH, PCO2, and lactate has previously been demonstrated during steady-state exercise. The purpose of the present study was to compare arterialized venous and arterial pH, PCO2, K+, lactate, pyruvate, and epinephrine during the constantly changing circumstances of an incremental exercise test. Eight normal subjects undertook an incremental exercise test (increasing by 20 W/min) to exhaustion on a cycle ergometer during which simultaneous arterial and arterialized venous samples were drawn over the last 20 s of each work load. Linear regression of arterialized venous on arterial values showed that r varied from 0.97 to 0.99 for the variables examined and, therefore, showed that accurate estimates of arterial values could be made from the arterialized venous results during incremental testing. For many purposes it could be assumed that arterialized venous values equaled arterial values without serious error.

Continuous, on-line DNA sequencing using a versatile infrared laser scanner/electrophoresis apparatus.

A new apparatus for continuously detecting fluorescently labeled DNA fragments is based on infrared fluorescence technology. This technology combines state-of-the-art developments in chemistry, laser technology, and detection, while achieving improved reliability, sensitivity, and flexibility for applications including DNA sequencing. DNA molecules labeled with a novel infrared fluorophore are detected during electrophoresis using a scanning infrared fluorescence microscope. The microscope consists of a laser diode for exciting the fluorophore and a silicon avalanche photodiode for detecting the infrared emission. Optimum conditions for detection and throughput are obtained by adjusting electrophoresis, scanning and imaging parameters. Typical DNA sequencing runs (test templates) allow identification of over 500 bases per sample with greater than 99% accuracy.

Cytophotometric evidence of variation in genome size of desmognathine salamanders.

The amount of DNA per haploid genome, the C-value, is often directly correlated with nuclear and cell volume, but inversely correlated with cell replication rate. Also, rates of cellular growth sometimes appear to be correlated with organismal developmental rates and life history patterns. Among vertebrates, salamanders exhibit the greatest variation in genome size. In the present study we have examined interspecific and intraspecific variation in blood cell DNA levels in the genus Desmognathus, which shows greater variation in life history traits than any other salamander genus. Specimens of Desmognathus quadramaculatus, D. monticola, D. ochrophaeus and D. wrighti were collected from nature at two localities in the southern Appalachian Mountains. Estimates of genome size in pg of DNA were obtained from blood smears by DNA-Feulgen cytophotometry, using erythrocyte nuclei of Xenopus laevis as an internal reference standard of 6.35 pg DNA per cell. C-values of Desmognathus are the smallest in the order Caudata. Although significant variation in DNA levels was found among the four species, the differences were small, and do not support previously proposed relationships between C-value and life-history variation.