Contact angle of a hemispherical bubble: an analytical approach

We have calculated the equilibrium shape of the axially symmetric Plateau border along which a spherical bubble contacts a flat wall, by analytically integrating Laplace’s equation in the presence of gravity, in the limit of small Plateau border sizes. This method has the advantage that it provides closed-form expressions for the positions and orientations of the Plateau border surfaces. Results are in very good overall agreement with those obtained from a numerical solution procedure, and are consistent with experimental data. In particular we find that the effect of gravity on Plateau border shape is relatively small for typical bubble sizes, leading to a widening of the Plateau border for sessile bubbles and to a narrowing for pendant bubbles. The contact angle of the bubble is found to depend even more weakly on gravity

Deliriumin the ICU setting ‐ a subjective and theoretical survey before the implementation of the Confusion Assessment Method for the ICU in an unit

Background and Goal of Study: The current definition of delirium comprises acute change or fluctuation in mental status and inattention, accompanied by either altered level of consciousness or disorganized thinking. It is a frequent condition in the ICU and it is associated with longer hospital stay, increase in mortality at 6 months and long-term cognitive impairment, but remains under diagnosed. The Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) has been validated and implemented in many ICUs and its use is recommended by the Society of Critical Care Medicine. It is our purpose to evaluate the individual perspective and the objective knowledge of our staf f about delirium before the implementation of the CAM-ICU. Materials and Methods: Anonymous survey to our ICU clinical staf f which contained subjective and ‘true or false’ questions. Data was analised with the sof tware SPSS version 17.0. The Wilcoxon test was used to compare autoperception of knowledge about delirium and the content of answers regarding its definiton. Results: Forty two questionnaires were returned (participation rate of 73%), 11 from physicians and 31 from nurses. Overall, 61,9% of inquiries think they can give a definition for delirium in the ICU and 50% claim to be able to evaluate delirium. 28,6% of the respondents - 63,6% of the physicians and 16,1% of the nurses - know the CAM-ICU. From these only a quarter has received education on this method, 75% think it’s easy to apply and 66% don’t see its use as an increase in the daily workload. We found a high rate of wrong and ‘I don’t know’ answers to questions about operationalization, diagnosis and outcome. The subjects’ auto-perception on their knowledge about delirium [Likert scale] was compared to their ability to answer questions related to its definiton - ‘attention deficit is essencial for diagnosis’ [true], Wilcoxon test Z=-4,699 (p< 0,001); ‘disorganized thinking is essential for diagnosis’ [false], Wilcoxon test Z=-4,437 (p< 0,001). Conclusions: The respondents’ auto perception of knowledge about delirium doesn’t translate in the ability of giving an appropriate definition and making an adequate evaluation. Most of the inquiries don’t know the CAM-ICU, but those who do believe it’s easy to apply and its use won’t increase the workload. We performed educational sessions about delirium and the CAM-ICU in our unit to encourage our clinical staf f to deal properly with this hazardous condition

Proton conductivity of Nafion-azolebisphosphonates membranes for PEM fuel cells

Energy systems with cleaner and sustainable sources are crucial challenges of the 21st century to deal with the environmental threat of global warming and the declining reserves of fossil fuels. Fuel cells are electrochemical devices that convert the chemical energy stored in a fuel directly into electrical energy, providing electrical energy with high efficiency and low environmental impact. Among them, proton exchange membrane fuel cells (PEMFCs) are considered promising power sources, due to their high power density and high power-to-weight ratio but their performance depends crucially on their proton exchange membranes [1]. Usually, these membranes are made of organic polymers containing acidic functionalities (ex. Nafion® ), which proton transport properties strongly depend on their water content and, consequently, limit their operation temperatures up to 90ºC. Preliminary studies have demonstrated that incorporation of aryl-bisphosphonic acids into Nafion, by casting, results in an enhancement of the proton conductivity of the membrane. The aim of this work was the preparation of new Nafion membranes doped with azolebisphosphonates derivatives, which could act as a source of protons and also function as proton acceptors, facilitating the intermolecular transmission of protons through the membrane

Sustained-Release Bupropion Overdose: A Case Report

Bupropion is an atypical antidepressant with a unique aminoketone structure similar to amphetamines. A narrow therapeutic margin is evident from observational studies that show seizure activity with doses of 400-600 mg or higher. A 38-year old woman took an overdose of 6 grams of bupropion with 110 grams of alcohol. She presented to the Emergency Department with agitation, visual hallucinations and myoclonus of the upper limbs; eyes spontaneously open with isochoric and light reactive pupils with horizontal nystagmus; afebrile, normotensive (121/63 mm Hg) and tachycardic (120 beats/minute). The electrocardiogram revealed a sinus tachycardia with prolonged QT interval (QT/QTc: 0.46/ 0.537) and a QRS complex length in the upper limit of normal. Arterial blood gases revealed metabolic acidosis (pH = 7.16) with increased anion-gap (value=18). She developed mal epilepticus needing thiopental induced coma and Intensive Care Unit (ICU) admission. She suffered prolonged symptoms including seizures before fully recovering. The narrow therapeutic range and the increasing use in the treatment of smoking cessation boosted the number of intentional and unintentional poisoning by this drug. Previous reports of bupropion overdose almost all involve the immediate release formulation. There are some reports of overdose with sustained-release formulation, but there is limited information on its spectrum of toxicity

Cyclic deformation of bidisperse two-dimensional foams

In-plane deformation of foams was studied experimentally by subjecting bidisperse foams to cycles of traction and compression at a prescribed rate. Each foam contained bubbles of two sizes with given area ratio and one of three initial arrangements: sorted perpendicular to the axis of deformation (iso-strain), sorted parallel to the axis of deformation (iso-stress), or randomly mixed. Image analysis was used to measure the characteristics of the foams, including the number of edges separating small from large bubbles N-sl, the perimeter (surface energy), the distribution of the number of sides of the bubbles, and the topological disorder mu(2)(N). Foams that were initially mixed were found to remain mixed after the deformation. The response of sorted foams, however, depended on the initial geometry, including the area fraction of small bubbles and the total number of bubbles. For a given experiment we found that (i) the perimeter of a sorted foam varied little; (ii) each foam tended towards a mixed state, measured through the saturation of N-sl; and (iii) the topological disorder mu(2)(N) increased up to an "equilibrium" value. The results of different experiments showed that (i) the change in disorder, Delta mu(2)(N), decreased with the area fraction of small bubbles under iso-strain, but was independent of it under iso-stress; and (ii) Delta mu(2)(N) increased with Delta N-sl under iso-strain, but was again independent of it under iso-stress. We offer explanations for these effects in terms of elementary topological processes induced by the deformations that occur at the bubble scale

The KLa influence on ethanol production by Pichia stipitis

Nowadays, there is a great interest in the development of technologies for ethanol production as an alternative combustible, since it can be used instead of petrol or to blend with petrol, reducing the country’s dependence on oil and imported fuel. It is known that the ethanol production by fermentation is influenced by several process conditions such as pH, temperature, medium composition, oxygen availability, among others. Determining the most suitable fermentation conditions is of large importance for the establishment of a successful technology. In the present work, the influence of oxygen transfer volumetric rate (KL a) on xylose to ethanol bioconversion by the yeast Pichia stipitis NRRL Y-7124 was evaluated using a semi-defined fermentation medium containing 90 g/l xylose. The assays were carried out in a bioreactor at 30°C, under different aeration conditions (0.5, 1.0, and 1.5 vvm) and stirring rates (200, 300 and 400 rpm) which resulted in KL a values of 2.3, 18.7 and 65.8 h-1 respectively. According to the results, the bioconversion was dependent on the aeration rate employed, the highest ethanol production (27.1 g/l) being achieved when using a KL a of 2.3 h-1. The increase of this parameter to 18.7 and 65.8 h-1 promoted decreases of 52% and 100% on ethanol production, respectively. By using a KL a of 65.8 h-1 the ethanol production was totally deviated to biomass production. Such results are of interest for the development of a suitable technology for ethanol production by Pichia stipitis