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Continuous Flow (continuous + flow)
Terms modified by Continuous Flow Selected AbstractsEvaluation of the Heterogeneously Catalyzed Strecker Reaction Conducted Under Continuous FlowEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 33 2008Charlotte Wiles Abstract Building on our experience of micro-reaction technology, we present herein the evaluation of an integrated borosilicate glass micro reactor in which 51 ,-aminonitriles were synthesized via a series of continuous solution-phase and heterogeneously catalyzed reaction steps, affording analytically pure products in yields > 99.6,%. As an extension to this, the ability to selectivity synthesize aldehydic Strecker products in the presence of ketonic functionalities was also investigated, concluding with the chemoselective synthesis of 2-(4-acetylphenyl)-2-(phenethylamino)acetonitrile whereby the desired product was obtained in 99.8,% yield and quantitative purity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Towards Continuous Flow, Highly Enantioselective Allylic Amination: Ligand Design, Optimization and SupportingADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009Dana Popa Abstract A family of enantiopure diphenylphosphinooxazolines (PHOX) containing in their structures a sterically tunable alkoxymethyl group (-CH2OR) has been optimized for the palladium-catalyzed asymmetric allylic amination. The optimal catalyst (R=CH3), depicting very high catalytic activity and broad scope applicability, has been further modified to include an ,-alkynyloxy substituent of variable length for polymer supporting via click chemistry, and has been anchored onto slightly cross-linked azidomethyl poly(styrene). The length of a polymethylene chain connecting the PHOX unit with the 1,2,3-triazole linker has been optimized, and the first polymer-supported PHOX ligands for the highly enantioselective allylic amination have been prepared in this manner. Conditions for catalyst recovery and reuse in microwave-promoted amination reactions have been established, and the system has been finally adapted to continuous flow operation. [source] Preservation of Endothelium Nitric Oxide Release by Pulsatile Flow Cardiopulmonary Bypass When Compared With Continuous FlowARTIFICIAL ORGANS, Issue 11 2009Ettore Lanzarone Abstract The aim of this work is to analyze endothelium nitric oxide (NO) release in patients undergoing continuous or pulsatile flow cardiopulmonary bypass (CPB). Nine patients operated under continuous flow CPB, and nine patients on pulsatile flow CPB were enrolled. Plasma samples were withdrawn for the chemiluminescence detection of nitrite and nitrate. Moreover the cellular component was withdrawn for the detection of nitric oxide synthase (NOS) activity in the erythrocytes, and an estimation of systemic inflammatory response was carried out. Significant reduction in the intraoperative concentration with respect to the preoperative was observed only under continuous flow CPB for both nitrite and NOx (nitrite + nitrate) concentration (P = 0.010 and P = 0.016, respectively). Significant difference in intraoperative nitrite concentration was also observed between the groups (P = 0.012). Finally, erythrocytes showed a certain endothelial NOS activity, which did not differ between the groups, and no differences in the inflammatory response were pointed out. The significant reduction of NO2 - concentration under continuous perfusion revealed the strong connection among perfusion modality, endothelial NO release, and plasmatic nitrite concentration. The similar erythrocyte eNOS activity between the groups revealed that the differences in blood NO metabolites are mainly ascribable to the endothelium release. [source] A Microreactor for Microwave-Assisted Capillary (Continuous Flow) Organic Synthesis.CHEMINFORM, Issue 42 2005Eamon Comer Abstract For Abstract see ChemInform Abstract in Full Text. [source] Lower limb ulceration: a detailed study of aetiology in 555 patientsBRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 4 2000J. Naik Background: The purpose of the study was to investigate the aetiology of lower limb ulceration. Methods: The aetiology of lower limb ulceration was reviewed in 555 patients with 689 ulcerated limbs referred to a single-visit leg ulcer clinic. Results: The mean age of the patients was 70 (range 27,95) years and 335 (60 per cent) were women. The aetiology of the ulceration in 689 limbs was venous in 496 (72 per cent), arterial in 14 (2 per cent), mixed venous and arterial in 101 (15 per cent), with other causes in 78 (11 per cent). Of the 496 venous ulcers, 261 (53 per cent) had isolated superficial reflux, 233 (47 per cent) had deep venous reflux, of which 165 (71 per cent) had full-length and 68 (29 per cent) segmental reflux, and two patients had isolated perforator reflux. Deep venous obstruction was present in 16 limbs (3 per cent) with venous ulcers and 14 of these demonstrated continuous flow in the long saphenous vein (LSV). Of the 261 ulcerated legs with isolated superficial reflux, 197 (75 per cent) had LSV reflux only, 22 (8 per cent) had short saphenous vein (SSV) reflux only and 41 (16 per cent) had combined LSV and SSV reflux. Of those with LSV reflux, 65 per cent had a medial malleolar ulcer and 20 per cent had a lateral malleolar lesion. Of those with SSV reflux, 62 per cent had a lateral malleolar ulcer and 38 per cent had a medial malleolar ulcer. Conclusion: Half of the ulcerated legs have superficial venous reflux; these combined with the superficial and segmental deep venous reflux group comprise the 65 per cent of patients who may benefit from superficial venous surgery. Continuous flow in the LSV should alert the clinician to deep venous obstruction, in which circumstance compression therapy should be used with extreme caution. Duplex is central to the investigation of the ulcerated leg. © 2000 British Journal of Surgery Society Ltd [source] Supercritical extraction of borage seed oil coupled to conventional solvent extraction of antioxidantsEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 11 2008Carmen Soto Abstract This paper describes the extraction of borage seed oil by supercritical carbon dioxide (SC-CO2) and the further extraction of antioxidants from the SC-CO2 -defatted borage meal with organic solvents (water, methanol, ethanol and ethyl acetate). The optimal conditions for oil extraction were obtained at 303 and 323,K at 200,bar, 2.5,h and a continuous flow of CO2 of 1.5,L/h introduced through the bottom when the operating pressure and temperature were reached, attaining a yield of 60%. Borage oil is rich in unsaturated fatty acids; oleic acid, linoleic acid and linolenic acid accounted for 74% of the total fatty acid content under the above conditions. The highest extraction yield was achieved using water or methanol as extracting solvent from the SC-CO2 -defatted borage meal at 303,K and pressures of 200 and 150,bar for water and methanol, respectively. The most potent extracts, according to all methods tested, were obtained with water and methanol. [source] Numerical calculations of erosion in an abrupt pipe contraction of different contraction ratiosINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 1 2004M. A. Habib Abstract Erosion predictions in a pipe with abrupt contraction of different contraction ratios for the special case of two-phase (liquid and solid) turbulent flow with low particle concentration are presented. A mathematical model based on the time-averaged governing equations of 2-D axi-symmetric turbulent flow is used for the calculations of the fluid velocity field (continuous phase). The particle-tracking model of the solid particles is based on the solution of the governing equation of each particle motion taking into consideration the effect of particle rebound behaviour. Models of erosion were used to predict the erosion rate in mg/g. The effect of Reynolds number and flow direction with respect to the gravity was investigated for three contraction geometries considering water flow in a carbon steel pipe. The results show that the influence of the contraction ratio on local erosion is very significant. However, this influence becomes insignificant when the average erosion rates over the sudden contraction area are considered. The results also indicate the significant influence of inlet velocity variations. The influence of buoyancy is significant for the cases of low velocity of the continuous flow. A threshold velocity below which erosion may be neglected was indicated. Copyright © 2004 John Wiley & Sons, Ltd. [source] Experimental and modeling study of the oxidation of benzeneINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2003I. Da Costa This paper describes an experimental and modeling study of the oxidation of benzene. The low-temperature oxidation was studied in a continuous flow stirred tank reactor with carbon-containing products analyzed by gas chromatography. The following experimental conditions were used: 923 K, 1 atm, fuel equivalence ratios from 1.9 to 3.6, concentrations of benzene from 4 to 4.5%, and residence times ranging from 1 to 10 s corresponding to benzene conversion yields from 6 to 45%. The ignition delays of benzene,oxygen,argon mixtures with fuel equivalence ratios from 1 to 3 were measured behind shock waves. Reflected shock waves permitted to obtain temperatures from 1230 to 1970 K and pressures from 6.5 to 9.5 atm. A detailed mechanism has been proposed and allows us to reproduce satisfactorily our experimental results, as well as some data of the literature obtained in other conditions, such as in a plug flow reactor or in a laminar premixed flame. The main reaction paths have been determined for the four series of measurements by sensitivity and flux analyses. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 503,524, 2003 [source] Quality of applesauces processed by pulsed electric fields and HTST pasteurisation,INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 4 2009Z. T. Jin Summary A pilot plant scale continuous flow pulsed electric field (PEF) and high temperature short time (HTST) processing system was integrated with an aseptic packaging machine. Fuji applesauce and blueberry applesauce were processed with PEF followed by HTST pasteurisation (PEF + HTST). PEF + HTST processed Fuji applesauce from fresh Fuji apples demonstrated high and stable sensory scores during 9 months storage at 27 °C, and had comparative sensory quality with Meal Read-to-Eat (MRE) and commercial applesauce products stored at 4 °C. PEF + HTST processed blueberry applesauce from pre-pasteurised materials had lower sensory scores than PEF + HTST processed Fuji applesauce and was significantly less stable during the storage at 27 °C. PEF + HTST processed applesauces had aerobic count and mould and yeast count of <10 cfu mL,1 during storage. Electrical conductivity, pH and °Brix, were not significantly changed throughout storage time (P > 0.05). [source] Noninvasive Control of Adequate Cerebral Oxygenation During Low-Flow Antegrade Selective Cerebral Perfusion on Adults and Infants in the Aortic Arch SurgeryJOURNAL OF CARDIAC SURGERY, Issue 5 2008Álvaro Rubio M.D. Background: Aortic arch repair techniques using low-flow antegrade selective cerebral perfusion have been standardized to a certain degree. However, some of the often-stated beneficial effects have never been proven. Especially, the existence of an adequate continuous flow in both cerebral hemispheres during the surgical procedure still remains unclear as the monitoring of an effective perfusion remains a nonstandardized technique. Methods: Seventeen patients underwent surgical reconstruction of the aortic arch due to aortic aneurysm surgery (adult group n = 8 patients) or of the hypoplastic aortic arch due to hypoplastic left heart syndrome (HLHS) or aortic coarctation (infant group n = 9 patients) under general anesthesia and mild hypothermia (adult group 28 °C; infant group 25 °C). Mean weights were 92.75 ± 14.00 kg and 4.29 ± 1.32 kg, and mean ages were 58.25 ± 10.19 years and 55.67 ± 51.11 days in the adult group and the infant group, respectively. The cerebral O2 saturation measurement was performed by continuous plotting of the somatic reflectance oximetry of the frontal regional tissue on both cerebral hemispheres (rSO2, INVOS®; Somanetics Corporation, Troy, MI, USA). Results: During low-flow antegrade perfusion via innominate artery, continuous plots with similar values of O2 saturation (rSO2) in both cerebral hemispheres were observed, whereas a decrease in the rSO2 values below the desaturation threshold correlated with a displacement or an incorrect positioning of the arterial cannula in the right subclavian artery. Conclusions: Continuous monitorization of the cerebral O2 saturation during aortic arch surgery in adults and infants is a feasible technique to control an adequate cannula positioning and to optimize clinical outcomes avoiding neurological complications related to cerebral malperfusion. [source] Aerobic biological treatment of waste- waters containing dichloromethaneJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2007Sandra C Moura Abstract BACKGROUND: Volatilization has been advanced as one of the predominant phenomena contributing to volatile organic carbon emissions from wastewater treatment plants (WWTPs). In this study, strategies for minimizing such air stripping losses when treating a liquid stream containing dichloromethane (DCM), aiming at decreasing the overall emission inventory from WWTPs, were investigated. RESULTS: System R1, consisting of a continuous flow stirred tank reactor (CSTR) treating a liquid stream containing DCM at a concentration of 12 mmol dm,3 presented a biodegradation efficiency (BE) of 68%, based upon chloride release, with 10% of measurable losses, mainly due to volatilization, and 22% of unmeasurable losses. System R2 introduced operational designs aiming at decreasing DCM volatilization. In Experiment R2.1, a biotrickling filter, through which the air stripped from the CSTR was driven, was introduced leading to a reduction from 10% to 7% on the measurable losses. In Experiment R2.2, the air stripped from the CSTR was recirculated at a flow rate of 2.4 dm3 h,1 through the reactor medium before entering the biotrickling filter. The BE was improved from 69% to 82% and the losses associated with air stripping were successfully reduced to 2%. The proposed design, including air recirculation and the biotrickling filter, increased the ratio between the biodegradation rate and the volatilization rate from 7 to 41. CONCLUSIONS: Recirculation of the gaseous effluent through the reactor medium, which allowed for higher residence time within the bioreactor, was shown to be a successful strategy for improving the treatment process, thus minimizing DCM volatilization losses. Copyright © 2007 Society of Chemical Industry [source] Integrated synthesis and extraction of short-chain fatty acid esters by supercritical carbon dioxideAICHE JOURNAL, Issue 4 2010Marta Lubary Abstract We developed an efficient, integrated reaction-extraction process for the production of short-chain fatty acid ethyl esters (FAEE) from milk fat, using carbon dioxide as the only processing solvent. FAEE were synthesized using a short-chain fatty acid selective lipase. The expansion of the liquid mixture of reactants by dense carbon dioxide enhanced the apparent lipase selectivity. In situ extraction of FAEE by a continuous flow of supercritical carbon dioxide proved to increase the lipase production rate. When the integrated process was operated with alternated periods of synthesis and product removal, the overall selectivity for short-chain FAEE increased as well, as a result of the combination of the selectivities of lipase and extraction solvent. A two-fold increase of the lipase productivity was achieved at these conditions, compared to a single batch reaction. The developed process enables the synthesis and isolation of high-value fatty acid derivatives from a natural source such as milk fat. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Cooking up change in haute cuisine: Ferran Adrià as an institutional entrepreneurJOURNAL OF ORGANIZATIONAL BEHAVIOR, Issue 5 2007Silviya Svejenova Based on a longitudinal, inductive study of a critical case from a cultural sector, this article explores how institutional entrepreneurs initiate change. Our explanation points to four mechanisms: creativity that generates continuous flow of new ideas; theorization that takes stock of these ideas; reputation within and outside the field that endorses ideas as worthy of attention, and dissemination that brings ideas to the public domain. As novel ideas challenge received practices in the field, paradoxes of logics and identity emerge and provide potential for change. The study contributes to institutional theory by examining a preliminary, understudied stage of institutional change that provides a potential for change. Further, it shows how institutional entrepreneurs engage in the theorization and dissemination of their work. Finally, it reveals how reputation plays a critical role in the dissemination of new ideas and thus in the shaping up of the paradoxes and the potential for change. Copyright © 2007 John Wiley & Sons, Ltd. [source] Ultraviolet and visible Raman spectroscopic investigations of nanocrystalline carbon thin films grown by bias-assisted hot-filament chemical vapor depositionJOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2003S. Gupta Abstract The structural bonding in a series of nanocrystalline carbon thin films grown under different substrate biasing conditions was analyzed using Raman spectroscopy in both the visible and ultraviolet (uv) regimes of the spectrum. The nanocrystalline carbon thin films studied were deposited by the hot-filament chemical vapor deposition (HFCVD) technique using a 2% concentration of methane in hydrogen. The films were deposited on molybdenum substrates under various substrate biasing conditions. A positive bias (forward) produced a continuous flow of electrons from the filament on to the substrate, whereas a negative bias (negative) caused the substrate to be bombarded with positive ions. Films were also grown under no bias, for comparison. Differences in the Raman spectra obtained with visible (,L = 514.5 nm) and uv (,L = 244.0 nm) excitation sources were investigated. Apart from the basic features consisting of D and G bands at around 1360 and 1580 cm,1 in the case of visible Raman spectra, an extra feature at around 1060 cm,1, denoted a T band, appeared in the uv Raman spectra only. Hence, uv Raman scattering measurements clearly revealed the presence of sp3 -bonded carbon atoms. The position and its intensity ratio with respect to the G peak [(I(T)/I(G)] were used to provide a reliable means to measure the sp3 C bonding fraction, which is both semi-quantitative and non-destructive. The sp3 content estimated within the microstructure of n-C thin films was found to be around 60,80%. Further, probing the samples with two different photons (visible and uv) allowed us to estimate qualitatively the amount and clustering of sp2 sites. This technique provided a fast and reliable microstructural characterization of disordered carbons. The dispersion in the Raman features is specific to each carbon system and, therefore, can be used as a fingerprint. These findings point at the similarities of bias-assisted HFCVD nanocrystalline carbon (n-C) materials and the tetrahedrally bonded amorphous carbon (ta -C) materials grown by ion-beam assisted deposition (IBAD). Copyright © 2003 John Wiley & Sons, Ltd. [source] MASS LOAD ESTIMATION ERRORS UTILIZING GRAB SAMPLING STRATEGIES IN A KARST WATERSHED,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2003Alex W. Fogle ABSTRACT: Developing a mass load estimation method appropriate for a given stream and constituent is difficult due to inconsistencies in hydrologic and constituent characteristics. The difficulty may be increased in flashy flow conditions such as karst. Many projects undertaken are constrained by budget and manpower and do not have the luxury of sophisticated sampling strategies. The objectives of this study were to: (1) examine two grab sampling strategies with varying sampling intervals and determine the error in mass load estimates, and (2) determine the error that can be expected when a grab sample is collected at a time of day when the diurnal variation is most divergent from the daily mean. Results show grab sampling with continuous flow to be a viable data collection method for estimating mass load in the study watershed. Comparing weekly, biweekly, and monthly grab sampling, monthly sampling produces the best results with this method. However, the time of day the sample is collected is important. Failure to account for diurnal variability when collecting a grab sample may produce unacceptable error in mass load estimates. The best time to collect a sample is when the diurnal cycle is nearest the daily mean. [source] Extraction of favism-inducing agents from whole seeds of faba bean (Vicia faba L var major)JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 6 2005Jalal Jamalian Abstract The objective of the present study was to establish a suitable procedure by which favism-inducing glycosides vicine and convicine could be completely removed from whole seeds of faba beans without distorting their shape or reducing their nutritive value. Detoxification procedures carried out were extraction by water or, 10 g l,1 acid solutions (acetic, citric and phosphoric acid) using stepwise or continuous soaking procedures. Three cultivars of the beans were used in the study. In the stepwise soaking procedures, the seeds were soaked in either water or acid solution at 40 °C for different periods while in the continuous flow techniques, the solutions were constantly passed through a seed reservoir under different time,temperature,flow rate conditions. Extraction of vicine and convicine increased with increasing temperature and period of soaking and/or continuous flow of soaking solutions. Neither stepwise soaking nor autoclaving could effectively remove the favism factors from the whole seeds. The best results were obtained with continuous flow soaking in tap water, giving vicine- and convicine-free seeds. The protein contents of treated seeds were only slightly affected and their physical structure remained intact. Thus, it was concluded that the latter procedure was the method of choice for detoxification of dry whole seeds. Copyright © 2005 Society of Chemical Industry [source] The phage-driven microbial loop in petroleum bioremediationMICROBIAL BIOTECHNOLOGY, Issue 4 2010Eugene Rosenberg Summary During the drilling process and transport of crude oil, water mixes with the petroleum. At oil terminals, the water settles to the bottom of storage tanks. This drainage water is contaminated with emulsified oil and water-soluble hydrocarbons and must be treated before it can be released into the environment. In this study, we tested the efficiency of a continuous flow, two-stage bioreactor for treating drainage water from an Israeli oil terminal. The bioreactor removed all of the ammonia, 93% of the sulfide and converted 90% of the total organic carbon (TOC) into carbon dioxide. SYBR Gold staining indicated that reactor 1 contained 1.7 × 108 bacteria and 3.7 × 108 phages per millilitre, and reactor 2 contained 1.3 × 108 bacteria and 1.7 × 109 phages per millilitre. The unexpectedly high mineralization of TOC and high concentration of phage in reactor 2 support the concept of a phage-driven microbial loop in the bioremediation of the drainage water. In general, application of this concept in bioremediation of contaminated water has the potential to increase the efficiency of processes. [source] Nicotine, acetanilide and urea multi-level 2H-, 13C- and 15N-abundance reference materials for continuous-flow isotope ratio mass spectrometry,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2009Arndt Schimmelmann Accurate determinations of stable isotope ratios require a calibration using at least two reference materials with different isotopic compositions to anchor the isotopic scale and compensate for differences in machine slope. Ideally, the , values of these reference materials should bracket the isotopic range of samples with unknown , values. While the practice of analyzing two isotopically distinct reference materials is common for water (VSMOW-SLAP) and carbonates (NBS 19 and L-SVEC), the lack of widely available organic reference materials with distinct isotopic composition has hindered the practice when analyzing organic materials by elemental analysis/isotope ratio mass spectrometry (EA-IRMS). At present only L-glutamic acids USGS40 and USGS41 satisfy these requirements for ,13C and ,15N, with the limitation that L-glutamic acid is not suitable for analysis by gas chromatography (GC). We describe the development and quality testing of (i) four nicotine laboratory reference materials for on-line (i.e. continuous flow) hydrogen reductive gas chromatography-isotope ratio mass-spectrometry (GC-IRMS), (ii) five nicotines for oxidative C, N gas chromatography-combustion-isotope ratio mass-spectrometry (GC-C-IRMS, or GC-IRMS), and (iii) also three acetanilide and three urea reference materials for on-line oxidative EA-IRMS for C and N. Isotopic off-line calibration against international stable isotope measurement standards at Indiana University adhered to the ,principle of identical treatment'. The new reference materials cover the following isotopic ranges: ,2Hnicotine ,162 to ,45,, ,13Cnicotine ,30.05 to +7.72,, ,15Nnicotine ,6.03 to +33.62,; ,15Nacetanilide +1.18 to +40.57,; ,13Curea ,34.13 to +11.71,, ,15Nurea +0.26 to +40.61, (recommended , values refer to calibration with NBS 19, L-SVEC, IAEA-N-1, and IAEA-N-2). Nicotines fill a gap as the first organic nitrogen stable isotope reference materials for GC-IRMS that are available with different ,15N values. Comparative ,13C and ,15N on-line EA-IRMS data from 14 volunteering laboratories document the usefulness and reliability of acetanilides and ureas as EA-IRMS reference materials. Published in 2009 by John Wiley & Sons, Ltd. [source] A continuous flow mass spectrometry technique of argon isotope measurement for K/Ar geochronology,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2009Alexander V. Ignatiev A new method for the measurement of argon isotope composition in a continuous flow of helium for potassium/argon geochronology is described. Extraction of argon from geological samples in multiple-sample holders was carried out in a chamber by heating with a continuous Nd-YAG laser. The extracted and pre-concentrated argon is passed through a chromatographic capillary column in a flow of helium. Argon is separated from possible contaminants in the column and is injected through an open split into the ion source of an isotope ratio mass spectrometer. Measurement of the 36Ar, 38Ar and 40Ar isotopes was carried out in dynamic mode, using a triple-collector ion detector. These experiments have shown that continuous flow mass spectrometry can be used for the analysis of radiogenic argon in picogram quantities with an accuracy that is satisfactory for the solution of many geochronological problems. The method of argon isotope measurement in a continuous flow of helium is an alternative to the measurement of argon isotopes in the static mode. The sensitivity and accuracy of argon measurement by this method are comparable with those provided by the classical static method. The measurement of argon isotopes in a continuous flow of helium is simpler and more reliable than measurement in the static mode. Copyright © 2009 John Wiley & Sons, Ltd. [source] Awake tracheal intubation using the SensascopeÔ in 13 patients with an anticipated difficult airwayANAESTHESIA, Issue 5 2010R. Greif Summary We present the use of the SensaScopeÔ, an S-shaped rigid fibreoptic scope with a flexible distal end, in a series of 13 patients at high risk of, or known to have, a difficult intubation. Patients received conscious sedation with midazolam or fentanyl combined with a remifentanil infusion and topical lidocaine to the oral mucosa and to the trachea via a trans-cricoid injection. Spontaneous ventilation was maintained until confirmation of tracheal intubation. In all cases, tracheal intubation was achieved using the SensaScope. The median (IQR [range]) insertion time (measured from the time the facemask was taken away from the face until an end-expiratory CO2 reading was visible on the monitor) was 58 s (38,111 [28,300]s). In nine of the 13 cases, advancement of the SensaScope into the trachea was easy. Difficulties included a poor view associated with a bleeding diathesis and saliva, transient loss of spontaneous breathing, and difficulty in advancing the tracheal tube in a patient with unforeseen tracheal narrowing. A poor view in two patients was partially improved by a high continuous flow of oxygen. The SensaScope may be a valuable alternative to other rigid or flexible fibreoptic scopes for awake intubation of spontaneously breathing patients with a predicted difficult airway. [source] The Diamedica Draw-Over Vaporizer: a comparison of a new vaporizer with the Oxford Miniature VaporizerANAESTHESIA, Issue 1 2009W. A. English Summary The Diamedica Draw-Over Vaporizer (DDV) has been developed as an alternative to the Oxford Miniature Vaporizer (OMV). Both can function as draw-over or plenum vaporizers. The performances of these two vaporizers were compared under conditions simulating intermittent positive pressure ventilation (IPPV) and continuous flow (CF). Series 1 experiments were conducted with the vaporizers in water baths at 20, 25 and 30 °C. Vaporizers were tested at dial settings of 1,4% over a range of minute volumes (1.75,6 l.min,1) and flow rates (3,8 l.min,1). Series 2 experiments compared output of the vaporizers over time at ambient temperatures of 20, 25 and 30 °C. A minute volume of 6 l.min,1 (IPPV) and a gas flow of 8 l.min,1 (CF) were used with a vaporizer setting of 2%. Vapour concentrations were recorded at 5-min intervals. In series 1 IPPV experiments, the DDV vaporizer was more accurate, producing significantly fewer vapour concentrations 0.5% more than or less than setting (p = 0.013). The OMV tended to produce more favourable results under continuous flow (p = 0.42). In series 2 experiments, the accuracy of both vaporizers was similar but consistency of output over time was better for the DDV and consistency of output according to differences in ambient temperature was better for the DDV. The OMV produced more vapour concentrations that were markedly higher than dial setting, particularly at high ambient temperatures. The DDV is a suitable alternative to the OMV with some distinct advantages. These include a larger reservoir, tendency towards greater accuracy during IPPV and improved consistency of output. [source] In Vivo Assessment of a New Method of Pulsatile Perfusion Based on a Centrifugal PumpARTIFICIAL ORGANS, Issue 2 2010Jesús Herreros Abstract The aim of this study was to assess platelet dysfunction and damage to organs after extracorporeal circulation using a pump based on a new method that adds a pulsatile flow to the continuous flow provided by a centrifugal pump. The continuous component of the total flow (2,3 L/min) is created by a Bio-Pump centrifugal pump, while the pulsatile component is created by the pulsating of an inner membrane pneumatically controlled by an intra-aortic counterpulsation balloon console (systolic volume of 37.5 mL in an asynchronous way with a frequency of 60 bpm). Six pigs were subjected to a partial cardiopulmonary bypass lasting 180 min and were sacrificed 60 min after extracorporeal circulation was suspended. The hematological study included the measurement of hematocrit, hemoglobin, leukocytes, and platelet function. The new pump did not significantly alter either platelet count or platelet function. In contrast, hematocrit and hemoglobin were significantly reduced during extracorporeal circulation (approximately 5% P = 0.011, and 2 g/dL P = 0.01, respectively). The leukocyte count during extracorporeal circulation showed a tendency to decrease, but this was not significant. In general, the short-term use of the new pump (4 h) did not cause any serious morphological damage to the heart, lung, kidney, or liver. The results suggest that the hemodynamic performance of the new pump is similar to a conventional centrifugal pump and could therefore be appropriate for use in extracorporeal circulation. [source] Sealing Performance of a Magnetic Fluid Seal for Rotary Blood PumpsARTIFICIAL ORGANS, Issue 9 2009Yoshinori Mitamura Abstract A magnetic fluid (MF) for a rotary blood pump seal enables mechanical contact-free rotation of the shaft and, hence, has excellent durability. The performance of a MF seal, however, has been reported to decrease in liquids. We have developed a MF seal that has a "shield" mechanism and a new MF with a higher magnetization of 47.9 kA/m. The sealing performance of the MF seal installed in a rotary blood pump was studied. Under the condition of continuous flow, the MF seal remained in perfect condition against a pressure of 298 mm Hg (pump flow rate: 3.96 L/min). The seal was also perfect against a pressure of 170 mm Hg in a continuous flow of 3.9 L/min for 275 days. We have developed a MF seal that works in liquid against clinically used pressures. The MF seal is promising as a shaft seal for rotary blood pumps. [source] A Mathematical Model to Evaluate Control Strategies for Mechanical Circulatory SupportARTIFICIAL ORGANS, Issue 8 2009Lieke G.E. Cox Abstract Continuous flow ventricular assist devices (VADs) for mechanical circulatory support (MCS) are generally smaller and believed to be more reliable than pulsatile VADs. However, regarding continuous flow, there are concerns about the decreased pulsatility and ventricular unloading. Moreover, pulsatile VADs offer a wider range in control strategies. For this reason, we used a computer model to evaluate whether pulsatile operation of a continuous flow VAD would be more beneficial than the standard constant pump speed. The computer model describes the left and right ventricle with one-fiber heart contraction models, and the systemic, pulmonary, and coronary circulation with lumped parameter hemodynamical models, while the heart rate is regulated with a baroreflex model. With this computer model, both normal and heart failure hemodynamics were simulated. A HeartMate II left ventricular assist device model was connected to this model, and both constant speed and pulsatile support were simulated. Pulsatile support did not solve the decreased pulsatility issue, but it did improve perfusion (cardiac index and coronary flow) and unloading (stroke work and heart rate) compared with constant speed. Also, pulsatile support would be beneficial for developing control strategies, as it offers more options to adjust assist device settings to the patient's needs. Because the mathematical model used in this study can simulate different assist device settings, it can play a valuable role in developing mechanical circulatory support control strategies. [source] An Advanced Physiological Controller Design for a Left Ventricular Assist Device to Prevent Left Ventricular CollapseARTIFICIAL ORGANS, Issue 10 2003Yi Wu Abstract: A continuous flow left ventricle assist device (LVAD), which is mainly composed of a continuous flow blood pump and a physiological controller, has only one control input, the rotational speed of the pump, but at least three performance criteria to meet. The challenge for the physiological controller of a long-term continuous flow LVAD is the adaptability to different cardiovascular loading situations and the ability to handle systemic and parametric uncertainties with only one control input. The physiological LVAD controller presented in this article exhibits good performance in terms of the three performance criteria in different physiological loading conditions, such as disturbance, resting, and moderate exercise, for a patient with congestive heart failure. The collapse of the left ventricle, which is an inherent problem for a continuous flow LVAD, has been prevented because of the control algorithm design. [source] Perfusate Lactate Dehydrogenase Level and Intrarenal Resistance Could Not Be Adequate Markers of Perfusion Quality During Isolated Kidney PerfusionARTIFICIAL ORGANS, Issue 11 2000Berta Herrera Abstract: The main goal of this work was to study the influence of perfusion pressure and flow waveform during kidney perfusion, and the relationship between renal vascular resistance (RVR) and lactate dehydrogenase (LDH) concentration in the perfusate. Simultaneous constant pressure kidney perfusions were performed with either pulsatile or continuous flow at either 30 or 80 mm Hg of constant perfusion pressure. Mean flow, pressure, and RVR were displayed online during perfusion. Perfusate samples for LDH, creatine phosphatase kinase (CPK), and alkaline phosphatase (AP) determinations were taken. At the end of the perfusion, 2 ml of Evans blue was injected into the circuit to obtain images of perfusate distribution, and the kidneys were weighed. Also, hematoxylin/eosine studies were performed, showing more Bowman's space and tubular dilation in kidneys perfused with high pressure. We did not find differences in RVR between kidneys perfused at 30 and 80 mm Hg; nevertheless, perfusate distribution was better in the 80 mm Hg perfusions. We did not find any correlation between enzyme release and RVR in kidneys perfused with different mean pressures. These findings suggest that vascular resistance and LDH concentration cannot be independently considered as adequate markers of perfusate distribution. [source] Structure and species richness in wetland continua on sandy soils in subtropical and tropical AustraliaAUSTRAL ECOLOGY, Issue 7 2009RAYMOND L. SPECHT Abstract Net photosynthetic fixation of wetland plant communities is confined to the period of the year when the surface soil is not waterlogged and is thus well aerated. In the open-structured vegetation continuum across freshwater wetlands on sandy soils in subtropical and tropical Australia, the sum of the foliage projective covers (FPCs) of the overstorey and understorey strata remains constant, while that of the overstorey decreases to zero as seasonal waterlogging (and anaerobic conditions) in the surface root systems increases. Density and height of the overstorey trees , of only one or two species , and species richness (number of species per hectare) in the understorey decreases along this waterlogging gradient. Melaleuca paperbark trees, possessing surface roots with cortical aerenchyma, may form a closed-forest at the edge of the wetland continuum wherever there is a continuous flow of aerated water. As global warming progresses, an increase in air temperature in the atmosphere flowing over and through the wetland continuum during the short period of annual foliage-growth will affect the combined FPCs of overstorey and understorey strata, as well as the leaf-specific weights of all leaves throughout the plant community. With a reduction in net photosynthetic fixation, species richness of the plant community will slowly decline. [source] Trichloroethene and cis -1,2-dichloroethene concentration-dependent toxicity model simulates anaerobic dechlorination at high concentrations.BIOTECHNOLOGY & BIOENGINEERING, Issue 3 2010II: Continuous flow, attached growth reactors Abstract A model that was used to describe toxicity from high concentrations of chlorinated aliphatic hydrocarbons (CAHs) on reductively dechlorinating cultures in batch reactors (Sabalowsky and Semprini (in press)) was extended here to simulate observations in continuous flow suspended and attached growth reactors. The reductively dechlorinating anaerobic Evanite subculture (EV-cDCE) was fed trichloroethene (TCE) and excess electron donor to accumulate cis -1,2-dichloroethene (cDCE) in a continuous flow stirred tank reactor (CFSTR); and an attached growth recirculating packed column (RPC). A concentration-dependent toxicity model used to simulate the results of batch reactors in part I (Sabalowsky and Semprini (in press) Biotechnol Bioeng) also simulated well the observations for the CFSTR and RPC growth modes. The toxicity model incorporates cDCE and TCE toxicity coefficients that directly increase the cell decay coefficient in proportion with cDCE and TCE concentrations. Simulated estimates of the cDCE and TCE toxicity coefficients indicate reductively dechlorinating cells are most sensitive to high concentrations of cDCE and TCE in batch-fed growth, followed by CFSTR, with attached growth being least sensitive. The greater toxicity of TCE than cDCE, and ratio of the modeled toxicity coefficients, agrees with previously proposed models relating toxicity to partitioning in the cell wall (KM/B), proportional to octanol-water partitioning (KOW) coefficients. Biotechnol. Bioeng. 2010;107: 540,549. © 2010 Wiley Periodicals, Inc. [source] Microfluidic Tissue Model for Live Cell ScreeningBIOTECHNOLOGY PROGRESS, Issue 4 2007Philip J. Lee We have developed a microfluidic platform modeled after the physiologic microcirculation for multiplexed tissue-like culture and high-throughput analysis. Each microfabricated culture unit consisted of three functional components: a 50 ,m wide cell culture pocket, an artificial endothelial barrier with 2 ,m pores, and a nutrient transport channel. This configuration enabled a high density of cancer cells to be maintained for over 1 week in a solid tumor-like morphology when fed with continuous flow. The microfluidic chip contained 16 parallel units for "flow cell" based experiments where live cells were exposed to a soluble factor and analyzed via fluorescence microscopy or flow-through biochemistry. Each fluidically independent tissue unit contained ,500 cells fed with a continuous flow of 10 nL/min. As a demonstration, the toxicity profile of the anti-cancer drug paclitaxel was collected on HeLa cells cultured in the microfluidic format and compared with a 384-well dish for up to 5 days of continuous drug exposure. [source] Lower limb ulceration: a detailed study of aetiology in 555 patientsBRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 4 2000J. Naik Background: The purpose of the study was to investigate the aetiology of lower limb ulceration. Methods: The aetiology of lower limb ulceration was reviewed in 555 patients with 689 ulcerated limbs referred to a single-visit leg ulcer clinic. Results: The mean age of the patients was 70 (range 27,95) years and 335 (60 per cent) were women. The aetiology of the ulceration in 689 limbs was venous in 496 (72 per cent), arterial in 14 (2 per cent), mixed venous and arterial in 101 (15 per cent), with other causes in 78 (11 per cent). Of the 496 venous ulcers, 261 (53 per cent) had isolated superficial reflux, 233 (47 per cent) had deep venous reflux, of which 165 (71 per cent) had full-length and 68 (29 per cent) segmental reflux, and two patients had isolated perforator reflux. Deep venous obstruction was present in 16 limbs (3 per cent) with venous ulcers and 14 of these demonstrated continuous flow in the long saphenous vein (LSV). Of the 261 ulcerated legs with isolated superficial reflux, 197 (75 per cent) had LSV reflux only, 22 (8 per cent) had short saphenous vein (SSV) reflux only and 41 (16 per cent) had combined LSV and SSV reflux. Of those with LSV reflux, 65 per cent had a medial malleolar ulcer and 20 per cent had a lateral malleolar lesion. Of those with SSV reflux, 62 per cent had a lateral malleolar ulcer and 38 per cent had a medial malleolar ulcer. Conclusion: Half of the ulcerated legs have superficial venous reflux; these combined with the superficial and segmental deep venous reflux group comprise the 65 per cent of patients who may benefit from superficial venous surgery. Continuous flow in the LSV should alert the clinician to deep venous obstruction, in which circumstance compression therapy should be used with extreme caution. Duplex is central to the investigation of the ulcerated leg. © 2000 British Journal of Surgery Society Ltd [source] | |||||||||||||||||||||||||||||||||||||