Secondary Electron Emission from Surfaces with Small Structure

It is found that for objects possessing small surface structures with differing radii of curvature the secondary electron emission (SEE) yield may be significantly higher than for objects with smooth surfaces of the same material. The effect is highly pronounced for surface structures of nanometer scale, often providing a more than 100% increase of the SEE yield. The results also show that the SEE yield from surfaces with structure does not show an universal dependence on the energy of the primary, incident electrons as it is found for flat surfaces in experiments. We derive conditions for the applicability of the conventional formulation of SEE using the simplifying assumption of universal dependence. Our analysis provides a basis for studying low-energy electron emission from nano structured surfaces under a penetrating electron beam important in many technological applications.Comment: 6 pages, 8 figures, Published in Phys. Rev. B, 21 September 2015, http://journals.aps.org/prb/abstract/10.1103/PhysRevB.92.12543

Perioperative antiplatelet therapy: the case for continuing therapy in patients at risk of myocardial infarction

Recent clinical data show that the risk of coronary thrombosis after antiplatelet drugs withdrawal is much higher than that of surgical bleeding if they are continued. In secondary prevention, aspirin is a lifelong therapy and should never be stopped. Clopidogrel is regarded as mandatory until the coronary stents are fully endothelialized, which takes 3 months for bare metal stents, but up to 1 yr for drug-eluting stents. Therefore, interruption of antiplatelet therapy 10 days before surgery should be revised. After reviewing the data on the use of antiplatelet drugs in cardiology and in surgery, we propose an algorithm for the management of patients, based on the risk of myocardial ischaemia and death compared with that of bleeding, for different types of surgery. Even if large prospective studies with a high degree of evidence are still lacking on different antiplatelet regimens during non-cardiac surgery, we propose that, apart from low coronary risk situations, patients on antiplatelet drugs should continue their treatment throughout surgery, except when bleeding might occur in a closed space. A therapeutic bridge with shorter-acting antiplatelet drugs may be considere

Preoperative evaluation of patients with, or at risk of, coronary artery disease undergoing non‐cardiac surgery

The increasing number of patients with coronary artery disease undergoing major non‐cardiac surgery justifies guidelines concerning preoperative evaluation, stress testing, coronary angiography, and revascularization. A review of the recent literature shows that stress testing should be limited to patients with suspicion of a myocardium at risk of ischaemia, and coronary angiography to situations where revascularization can improve long‐term survival. Recent data have shown that any event in the coronary circulation, be it new ischaemia, infarction, or revascularization, induces a high‐risk period of 6 weeks, and an intermediate‐risk period of 3 months. A 3‐month minimum delay is therefore indicated before performing non‐cardiac surgery after myocardial infarction or revascularization. However, this delay may be too long if an urgent surgical procedure is requested, as for instance with rapidly spreading tumours, impending aneurysm rupture, infections requiring drainage, or bone fractures. It is then appropriate to use perioperative beta‐block, which reduces the cardiac complication rate in patients with, or at risk of, coronary artery disease. The objective of this review is to offer a comprehensive algorithm to help clinicians in the preoperative assessment of patients undergoing non‐cardiac surgery. Br J Anaesth 2002; 89: 747-5

Prämedikationsqualität und Patientenzufriedenheit nach Prämedikation mit Midazolam, Clonidin oder Placebo: Randomisierte Doppelblindstudie mit altersangepasster Dosierung

Zusammenfassung: Hintergrund: Die Prämedikation hat u.a. zum Ziel, Angstgefühle und innere Unruhe vor einem chirurgischen Eingriff zu lindern und gleichzeitig möglichst wenig unerwünschte Wirkungen zu verursachen. Es gibt bisher keine Untersuchungen, die die Wirkungen und Nebenwirkungen von Clonidin (Catapresan®), Midazolam (Dormicum®) und Placebo in altersabhängig unterschiedlicher Dosierung verglichen und deren Akzeptanz beim Patienten untersucht haben. Patienten und Methoden: In dieser randomisierten, placebokontrollierten Studie wurden 139 erwachsene Patienten untersucht und 60min vor der Narkoseeinleitung mit Clonidin, Midazolam oder Placebo prämediziert. Angst, Sedierungstiefe und Nebenwirkungen wurden an 6 aufeinanderfolgenden Zeitpunkten erfasst. Ergebnisse: Midazolam zeigte eine stärkere anxiolytische und sedative Wirkung als Clonidin. Die Prämedikation mit Midazolam verminderte die Sauerstoffsättigung. Es gab keine klinisch relevanten Veränderungen in der Hämodynamik in allen Gruppen. Midazolam und Clonidin verminderten das Risiko für "postoperative nausea and vomiting" (PONV). Midazolam zeigte die geringsten Nebenwirkungen. Placebo wurde von den Patienten weitaus am schlechtesten beurteilt, im Gegensatz zu Clonidin und Midazolam, das am besten beurteilt wurde. Schlussfolgerung: Die sedierende und anxiolytische Wirkung von Midazolam ist stärker als diejenige von Clonidin. Midazolam wurde von den Patienten besser angenommen als Clonidin, Clonidin siginfikant besser als Placebo. Die meisten Patienten würden Midazolam wieder wähle

Adaptive data acquisition multiplexing system and method

A reconfigurable telemetry multiplexer is described which includes a monitor-terminal and a plurality of remote terminals. The remote terminals each include signal conditioning for a plurality of sensors for measuring parameters which are converted by an analog to digital converter. CPU's in the remote terminals store instructions for prompting system configuration and reconfiguration commands. The measurements, instructions, and the terminal's present configuration and status data are transmitted to the monitor-terminal and displayed. In response to menu-driven prompts generated and displayed at the monitor-terminal, data generation request commands, status and health commands, and the like are input at the monitor-terminal and transmitted to the remote terminals. The CPU in each remote terminal receives the various commands, stores them in electrically alterable memory, and reacts in accordance with the commands to reconfigure a plurality of aspects of the system. The CPU in each terminal also generates parameter measurements, status and health signals, and transmits these signals of the respective terminals to the monitor-terminal for low data rate operator viewing and to higher rate external transmission/monitor equipment. Reconfiguration may be in real time during the general period of parameter measurement acquisition, and may include alteration of the gain, automatic gain rescaling, bias, and or sampling rates associated with one or more of the parameter measurements made by the remote terminals

Effects on coagulation of balanced (130/0.42) and non-balanced (130/0.4) hydroxyethyl starch or gelatin compared with balanced Ringer's solution: an in vitro study using two different viscoelastic coagulation tests ROTEM™ and SONOCLOT™†

Background Hydroxyethyl starch (HES) solutions compromise blood coagulation. Low molecular weight, low-substituted HES products, and electrolyte-balanced solutions might reduce this effect. We compared the effects of in vitro haemodilution on blood coagulation with a balanced 6% HES 130/0.42 solution (HESBAL), a saline-based 6% HES 130/0.4 solution (HESSAL), a balanced lactated Ringer's solution (RL) and a saline-based 4% gelatin solution (GEL). Methods Blood was obtained from 10 healthy male volunteers and diluted with the test solutions by 33% and 66%. Quality of clot formation was measured using two viscoelastic coagulation tests: SONOCLOT™ and activated rotation thromboelastometry ROTEM™. Results Of 16 parameters measured by the viscoelastic devices, we found three statistically significant differences compared with baseline for RL, but 11 for GEL, 10 for HESSAL, and 11 for HESBAL in the 33% haemodilution group (P=0.01). Comparing the different solutions, we observed a significant difference between crystalloids and colloids but none between GEL and HES. In the 66% dilution group, effects on blood coagulation were increased when compared with the 33% dilution group. We found no differences in coagulation impairment between balanced and non-balanced HES products and no differences in the detection of impaired blood coagulation due to haemodilution between the two viscoelastic coagulation tests. Conclusions Both ROTEM™ and SONOCLOT™ are sensitive tests for the detection of impaired blood coagulation due to haemodilution. There are fewer effects on blood coagulation using crystalloids compared with colloids. The effects of GEL and HES are similar. There is no difference between balanced HES 130/0.42 and non-balanced HES 130/0.

Amyloid-beta Leads to Impaired Cellular Respiration, Energy Production and Mitochondrial Electron Chain Complex Activities in Human Neuroblastoma Cells

Evidence suggests that amyloid-beta (Aβ) protein is a key factor in the pathogenesis of Alzheimer's disease (AD) and it has been recently proposed that mitochondria are involved in the biochemical pathway by which Aβ can lead to neuronal dysfunction. Here we investigated the specific effects of Aβ on mitochondrial function under physiological conditions. Mitochondrial respiratory functions and energy metabolism were analyzed in control and in human wild-type amyloid precursor protein (APP) stably transfected human neuroblastoma cells (SH-SY5Y). Mitochondrial respiratory capacity of mitochondrial electron transport chain (ETC) in vital cells was measured with a high-resolution respirometry system (Oxygraph-2k). In addition, we determined the individual activities of mitochondrial complexes I-IV that compose ETC and ATP cellular levels. While the activities of complexes I and II did not change between cell types, complex IV activity was significantly reduced in APP cells. In contrast, activity of complex III was significantly enhanced in APP cells, as compensatory response in order to balance the defect of complex IV. However, this compensatory mechanism could not prevent the strong impairment of total respiration in vital APP cells. As a result, the respiratory control ratio (state3/state4) together with ATP production decreased in the APP cells in comparison with the control cells. Chronic exposure to soluble Aβ protein may result in an impairment of energy homeostasis due to a decreased respiratory capacity of mitochondrial electron transport chain which, in turn, may accelerate neurons demis

Synchnonization, zero-resistance states and rotating Wigner crystal

We show that rotational angles of electrons moving in two dimensions (2D) in a perpendicular magnetic field can be synchronized by an external microwave field which frequency is close to the Larmor frequency. The synchronization eliminates collisions between electrons and thus creates a regime with zero diffusion corresponding to the zero-resistance states observed in experiments with high mobility 2D electron gas (2DEG). For long range Coulomb interactions electrons form a rotating hexagonal Wigner crystal. Possible relevance of this effect for planetary rings is discussed.Comment: 4 pages, 4 fig