Detection of individual spin species via frequency-modulated charge pumping.

We utilize a frequency-modulated charge pumping methodology to measure quickly and conveniently single "charge per cycle" in highly scaled Si/SiO2 metal-oxide-semiconductor field effect transistors. This is indicative of detection and manipulation of a single interface trap spin species located at the boundary between the SiO2 gate dielectric and Si substrate (almost certainly a Pb type center). This demonstration in sub-micrometer devices in which Dennard scaling of the gate oxide has yielded extremely large gate oxide leakage currents eliminates interference between the charge pumping current and the leakage phenomenon. The result is the ability to measure single trap charge pumping reliably and easily, which would otherwise be completely inaccessible due to oxide leakage. This work provides a unique and readily available avenue for single spin species detection and manipulation, which can be applied as a quantized standard of electrical current as well as to serve as a potentially useful platform for developing quantum engineering technologies. Finally, we discuss potential underlying physical mechanisms that are involved in producing a seemingly contradictory measure of both odd and even integer values for charge per cycle.

Effect of injectate volume and temperature on thermodilution cardiac output determination.

Six combinations of injectate volume (10, 5, and 3 ml) and temperature (0 degree C and room temperature [RT]) are recommended by the manufacturers of thermodilution cardiac output catheters and computers. We prospectively studied the accuracy and variability associated with these six combinations in critically ill patients requiring intermittent mandatory ventilation. The six methods were similar in their average estimation of cardiac output but differed markedly in their reproducibility. The 10 ml 0 degree C and 10 ml RT combinations produced the least variability. The 5 ml 0 degree C and 5 ml RT combinations produced more variability. Variability was much greater with the remaining two combinations. The 3 ml RT combination resulted in an average range of 1.71 1/min within each set of three repeat measurements and an average absolute difference of 1.51 1/min from the values obtained with 10 ml 0 degree C (each the mean of three injections). We recommend the use of 10 ml 0 degree C or 10 ml RT for cardiac output determinations in critically ill patients. If it is important to minimize volume administration, the use of 5 ml injectate is acceptable for an estimation of cardiac output. The use of 3 ml injectate volumes is rarely, if ever, justified because the small reduction in volume administration results in a large increase in variability.

Aminophylline potentiates sodium nitroprusside-induced hypotension in the dog.

The biochemical mechanisms by which nitroso-vasodilators cause smooth muscle relaxation remain controversial. One theory states that the effects of nitroso-vasodilators are mediated by increased intracellular levels of cyclic GMP due to activation of guanylate cyclase. To test this hypothesis, the authors examined the effects of sodium nitroprusside (SNP) in anesthetized dogs with an without pretreatment with the phosphodiesterase inhibitor aminophylline. Aminophylline pretreatment resulted in a 2.8-fold potentiation of the hypotensive effects of a continuous infusion of SNP. Potentiation also was seen for the effects of SNP on stroke volume, heart rate, and plasma cyclic GMP levels. These results support the hypothesis that nitroso-vasodilators exert their effects via guanylate cyclase activation. The authors advise caution when vasodilator therapy with agents such as SNP, nitroglycerin, or hydralazine is instituted in patients receiving aminophylline and when aminophylline is either instituted or discontinued in patients on vasodilator therapy.

Activity of neurons in the ventral tegmental region of the behaving monkey.

To investigate the functions of neurons in the ventral tegmental area, recordings were made of the activity of 257 single neurons in this area in the behaving monkey. Four main types of neuronal response were found in the ventral part of the tegmentum. First, neurons with activity phasically related to mouth or arm movements were found. Most of these were located relatively far lateral, close to the junction of the midbrain reticular formation with the zona incerta, or were in the substantia nigra, pars reticulata. Second, neurons were found which responded differentially in a visual discrimination task on trials on which the monkey had to initiate a licking response compared with trials on which he did not, and which also altered their firing rate tonically while mouth movements were being made in other situations (differential motor neurons). These were found mainly in the midbrain reticular formation, consistent with the view that populations of neurons in these regions are involved in the execution of movements. Third, neurons which also responded differentially in the visual discrimination task, but did not respond when the same movements were made in other situations, were found in the ventral tegmental area, in a region medial to and in some cases immediately dorsal to the substantia nigra pars compacta. Fourth, neurons which responded to cues such as a tone which enabled the monkey to prepare for performance on each trial of the visual discrimination task were found in the ventral tegmental area close to the midline. These third and fourth types of neurons were thus found in the region where neurons of the mesocortical and mesolimbic pathways are located. Their responses are similar to those of neurons found in the striatum, and it is suggested that they are important in enabling the animal to prepare for and then to engage in particular behavioral responses.

Acute hemodynamic effects of nitroglycerin in pulmonary hypertension.

Therapy of pulmonary hypertension is limited by the low potency and adverse effects of current pulmonary vasodilators. The hemodynamic effects of nitroglycerin in human pulmonary hypertension are not known. We administered nitroglycerin to nine patients with chronic pulmonary hypertension. Nitroglycerin increased cardiac index 40% (p less than 0.01), increased stroke volume 40% (p less than 0.01), decreased pulmonary vascular resistance 40% (p less than 0.01), and decreased mean pulmonary artery pressure 15% (p less than 0.01). Pulmonary vascular resistance decreased more than 25% in eight of the nine patients. In four patients the effects of intravenous nitroglycerin were reproduced by topical nitroglycerin preparations; cardiac index increased 50%, stroke volume increased 48%, pulmonary vascular resistance decreased 43%, and mean pulmonary artery pressure decreased 19%. Five of six patients treated with long-acting nitrates had substantial improvement of their symptoms. We conclude that therapy with nitroglycerin can be effective in patients with severe pulmonary hypertension.

Pulmonary vasodilator effects of nitroglycerin and sodium nitroprusside in canine oleic acid-induced pulmonary hypertension.

The hemodynamic effects of nitroglycerin (TNG) and sodium nitroprusside (SNP) were studied in a canine model of pulmonary hypertension. Oleic acid administration resulted in pulmonary hypertension with a 133% increase in pulmonary vascular resistance (PVR), a 40% increase in mean pulmonary artery pressure (MPAP), and a 28% decrease in cardiac output (CO). In this model, subsequent TNG administration increased CO 40%, decreased PVR 43%, and decreased MPAP 12%; pulmonary hemodynamics during TNG administration were not significantly different from those prior to oleic acid administration. SNP produced systemic hypotension but did not alter either PVR or MPAP and increased CO only 14%. The efficacy of TNG in this model may relate to its ability to dilate preferentially the pulmonary vascular bed.