Nanoscale solid-state quantum computing.

Most experts agree that it is too early to say how quantum computers will eventually be built, and several nanoscale solid-state schemes are being implemented in a range of materials. Nanofabricated quantum dots can be made in designer configurations, with established technology for controlling interactions and for reading out results. Epitaxial quantum dots can be grown in vertical arrays in semiconductors, and ultrafast optical techniques are available for controlling and measuring their excitations. Single-walled carbon nanotubes can be used for molecular self-assembly of endohedral fullerenes, which can embody quantum information in the electron spin. The challenges of individual addressing in such tiny structures could rapidly become intractable with increasing numbers of qubits, but these schemes are amenable to global addressing methods for computation.

Laser use in fixed, removable, and implant dentistry.

Laser use in reconstructive dental procedures (fixed, removable, or implant) provides a more controlled environment at the operative site. Control is a prerequisite for successful prosthetics and is accomplished by the unique ability of the laser to interact photo/thermally with biologic tissues using the lightest touch or none at all. Hemostasis is the result of this interaction by coagulating and sealing small blood and lymph vessels and vaporizing soft tissue. This hemostasis allows for more exact soft tissue contours to replicate or improve the periodontium before reconstruction, whether fixed or removable. The biologic seal is a unique phenomenon that occurs in the jaws of periimplant tissues of patients as a result of implant treatment. The biologic seal is paramount to the longevity and service of the implant. Use of dental laser technology provides the advanced laser and reconstructive dentist with the tool to improve the seal and improve the prognosis of the implant. The seal must be maintained by good oral hygiene and prophylactic procedures, however.

Large visible gas bubbles in the internal jugular vein: a common occurrence during supine radical neck surgery?

STUDY OBJECTIVE: To establish the frequency of large visible bubbles or collections of bubbles in the jugular vein during radical neck dissection in the supine position. DESIGN: Prospective observation by at least two investigators of random consecutive patients scheduled for radical neck surgery. SETTING: Operating room suite in a university hospital specializing in head and neck cancer surgery. PATIENTS: Twelve consecutive ASA physical status II and III patients undergoing modified radical dissection for cancer. INTERVENTIONS: General anesthesia with fentanyl, oxygen (O2) 30% to 40%, nitrous oxide (N2O) 60% to 70%, and isoflurane 0.5% to 1.5%, with mechanical ventilation. Table position horizontal. Modified radical neck dissections performed by attending surgeons. Surgical field (jugular vein) carefully observed by the surgeons and an independent anesthesiologist investigator for the presence of bubbles during the dissection. MEASUREMENTS AND MAIN RESULTS: Easily visible bubbles were observed in the jugular veins of 42% (5 of 12) of the consecutive radical neck dissection patients studied. Some of the collections of bubbles were large (greater than 2.5 cm in diameter). In one case, the appearance and subsequent disappearance of bubbles was followed by a transient drop in arterial blood pressure (BP) and in end-tidal carbon dioxide (PETCO2), which was suggestive of a diagnosis of central venous air embolization. CONCLUSIONS: We theorize that some unexplained, undesirable intraoperative events (hypotension, arrhythmia, and hypoxemia) during radical neck dissection could be a result of venous air embolus or paradoxical air embolus. The anesthesia community should be aware of the high frequency of these visible bubbles in the jugular veins during radical neck surgery, even in the supine position. At minimum, this phenomenon is a frequent event of intellectual interest. At worst, these bubbles may be harbingers of significant central air embolism.

Renal ischemic injury in the dog: characterization and effect of various pharmacologic agents.

Renal ischemia has been implicated as a major factor in the pathogenesis of acute renal failure. Despite several differences between the intrarenal norepinephrine infusion and renal artery occlusion models, they have been assumed to be prototypic models of ischemic renal injury. In our previous studies, an intrarenal infusion of norepinephrine caused a marked reduction in inulin clearance 3 hours after infusion. This reduction could be significantly attenuated by the concurrent infusion of mannitol, furosemide, or bradykinin. The effects of these three protective agents were evaluated before and after variable durations of renal artery occlusion to establish the similarities between the models and the magnitude of versatility of these protective agents. In the renal artery occlusion model, capsular fascia was stripped to eliminate collateral flow and ensure maximal renal ischemia. Three hours after 120 minutes of renal artery occlusion (n = 7), inulin clearance returned to 5.7% +/- 2.2% (SEM) of the control values and was not statistically different from that observed in the norepinephrine model. Intrarenal infusion of mannitol, furosemide, or bradykinin prior to and during the occlusion period, however, had no protective effect. Shorter durations of renal artery occlusion were evaluated to ensure an equivalent or decreased severity of acute renal failure compared with the norepinephrine model. After 90 or 60 minutes of renal artery occlusion, the clearance of inulin returned to 10.9% +/- 3.3% (n = 8) and 31.1% +/- 8.2% (n = 4) of control values, respectively. An intrarenal infusion of mannitol, furosemide, or bradykinin still had no significant protective effect, despite the decreased insult in the 60-minute renal artery occlusion studies. In summary, these findings demonstrate fundamental differences between renal artery occlusion and the norepinephrine model of renal functional impairment, and they suggest that the insult associated with norepinephrine infusion may involve factors other than cessation of blood flow.

Neuraminidase and contractile responses to norepinephrine in rat tail artery.

Sialic acids are negatively charged groups in the carbohydrate side chains of glycolipids and glycoproteins which line the external membrane surface. The goal of this study was to characterize the effect of neuraminidase, which selectively cleaves sialic acids, on contractile activity in vascular smooth muscle. Helically cut strips of rat tail artery were mounted in an organ chamber and isometric contractions were recorded. Following treatment with neuraminidase (0.2 U/ml, 1 h), contractile responses to norepinephrine were significantly greater than control responses. Phasic contractions to norepinephrine in calcium-free medium were not altered by neuraminidase, whereas following calcium depletion with EGTA, contractile responses to added calcium were greater in enzyme-treated strips than in control when activated with norepinephrine. The augmentation of norepinephrine-induced contractions following neuraminidase treatment was reversed by incubation of the arterial strips with N-acetylneuraminic acid (10(-4) M). Neuraminidase had no effect on contractile responses to potassium chloride, angiotensin II, and caffeine. Biochemical assay indicated that approximately 63% of the total sialic acid residues were removed from the arterial strips during incubation with the enzyme. It is concluded that a component for the control of the transmembrane calcium movement in response to norepinephrine is dependent on the presence of sialic acid residues.