Home About us Contact
|
Home About us Contact | ||
|
|
||
Dwell Time (dwell + time)
Selected AbstractsINHIBITION OF LISTERIA INNOCUA AND L. MONOCYTOGENES IN A LABORATORY MEDIUM AND COLD-SMOKED SALMON CONTAINING LIQUID SMOKEJOURNAL OF FOOD SAFETY, Issue 2 2001SUSAN M. VITT ABSTRACT Five commercial liquid smokes were tested in vitro and the most inhibitory to Listeria monocytogenes ATCC 19115 and L. innocua ATCC 33090 was Charsol Supreme. Chum salmon samples (100-g each) were brined, dipped for 15 s at varying concentrations of liquid smoke, inoculated with L. innocua, cold-processed and analyzed. Liquid smoke concentrations of 60,100% reduced L. innocua by 3-log10/g in the final product. Dwell times of 15 s to 5 min using 60% liquid smoke gradually decreased Listeria survival with an optimum 5-min dip. Isoeugenol was antilisterial in vitro but lacked synergism with liquid smoke in cold-smoked salmon. An immunoassay kit detected low inoculum levels (< 100 CFU/g) of L. innocua in one of three samples that were treated with liquid smoke for two and four minutes. Charsol Supreme was antilisterial but could not be relied on to totally eliminate Listeria in cold-smoked salmon. Panelists found the 0 to 2-min dipped sockeye salmon slightly desirable with no significant (p < 0.05) differences. The 5-min treatment was significantly (p < 0.05) darker, scored lower in desirability and flavor and contained 93 ppm of phenolic compounds. [source] The effects of acute exercise on attentional bias towards smoking-related stimuli during temporary abstinence from smokingADDICTION, Issue 11 2009Kate Janse Van Rensburg ABSTRACT Rationale Attentional bias towards smoking-related cues is increased during abstinence and can predict relapse after quitting. Exercise has been found to reduce cigarette cravings and desire to smoke during temporary abstinence and attenuate increased cravings in response to smoking cues. Objective To assess the acute effects of exercise on attentional bias to smoking-related cues during temporary abstinence from smoking. Method In a randomized cross-over design, on separate days regular smokers (n = 20) undertook 15 minutes of exercise (moderate intensity stationary cycling) or passive seating following 15 hours of nicotine abstinence. Attentional bias was measured at baseline and post-treatment. The percentage of dwell time and direction of initial fixation was assessed during the passive viewing of a series of paired smoking and neutral images using an Eyelink II eye-tracking system. Self-reported desire to smoke was recorded at baseline, mid- and post-treatment and post-eye-tracking task. Results There was a significant condition × time interaction for desire to smoke, F(1,18) = 10.67, P = 0.004, eta2 = 0.36, with significantly lower desire to smoke at mid- and post-treatment following the exercise condition. The percentage of dwell time and direction of initial fixations towards smoking images were also reduced significantly following the exercise condition compared with the passive control. Conclusion Findings support previous research that acute exercise reduces desire to smoke. This is the first study to show that exercise appears to also influence the salience and attentional biases towards cigarettes. [source] Dissociation between top-down attentional control and the time course of visual attention as measured by attentional dwell time in patients with mild cognitive impairmentEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2003Richard J. Perry Abstract Studies of the time course of visual attention have identified a temporary functional blindness to the second of sequentially presented stimuli in that the attentional cost of attending to one visual stimulus may lead to impairments in identifying a second stimulus presented within 500 ms of the first. This phenomenon is known as the attentional blink or attentional dwell time. The neural correlates of the attentional blink and its relationship to mechanisms that control attention are unknown. To examine this relationship we tested healthy controls and subjects in the preclinical stage of Alzheimer's disease, known as mild cognitive impairment (MCI), on a paradigm which affords quantification of both the attentional blink and the top-down control of attention. When subjects were asked to identify both a number and a letter that were rapidly and sequentially presented on a visual display, the detrimental effect that identifying the first stimulus had on the ability to identify the second served as a measure of the attentional blink. When asked to identify only one of the two stimuli, the ability to ignore the first stimulus was a function of their top-down attentional control. The MCI subjects demonstrated a normal attentional dwell time but in contrast they showed impaired top-down attentional control within the same paradigm. This dissociation suggests that these two aspects of visual attention are subserved by different neural systems. The possible neural correlates of these two attentional functions are discussed. [source] The economics and practicality of t-PA vs tunnel catheter replacement for hemodialysisHEMODIALYSIS INTERNATIONAL, Issue 1 2005Cairoli O. Kaiser Permanente Introduction:,Thrombolytic therapy is an important treatment modality for thrombosis-related catheter occlusion. Central venous access devices (CAVDs) are essential tools for the administration of many therapeutic modalities, especially for patients requiring lifetime therapy like hemodialysis. There are several reasons to salvage the occluded catheter. Catheter replacement results in an interruption of therapy delivery. This interruption may result in complications such as life-threatening metabolic and physiologic states. In addition, the patient's future access sites for CAVDs may be affected. The data released in the 2001 Annual Report , ESRD Clinical Performance Measures Project (Department of Health and Human Services, December 2001) shows 17% of prevalent patients were dialyzed with a chronic catheter continuously for 90 days or longer. In the pediatric population the data shows that 31% were dialyzed with a chronic catheter. The most common reasons for catheter placement included: no fistula or graft created (42%) and fistula and graft were maturing, not ready to cannulate (17%). Five percent of patients were not candidates for fistula or graft placement as all sites had been exhausted. Methods:,A short study was done in our medical center to evaluate the results of t-PA vs. changing the tunnel catheter. On an average a catheter costs about $400.00. If you add the cost of specialty personnel such as an interventional radiologist, radiology technician, radiology nurse, and the ancillaries such as the room, sutures, gauze, and tape, the total could reach $2000.00 easily. CathfloÔ Activase® costs around $60.00 for a single dose. T-PA was reconstituted by pharmacy personnel in single vials containing 2 mg/2 ml. Now with Cathflo, vials are stored in the renal clinic's refrigerator and when the need arises, the RN reconstitutes the medication. The RN, using established protocols, will instill Cathflo in the catheter following the volume requirements of the various tunnel catheters. After the t-PA is placed, the patient is sent home with instructions to return to their dialysis center the next day (arrangements are made by the RN as needed). In seventeen patients (17) with tunnel catheter malfunctions due to inadequate flow, not related to placement, t-PA was used. Of those 17 patients 2 were unable to use their catheter on their next dialysis treatment date, yielding an 88% success rate. This compares with clinical trials in which there is an 83% success rate with a dwell time of 4 hours, or an 89% rate on patients having a 2 hour dwell time (t-PA was repeated a second time if flow was not successfully restored. Results:,15/17 patients in our retrospective study showed that Cathflo worked successfully in restoring blood flow. Two catheters needed to be exchanged. The cost savings were significant when we compared the average cost of an exchange ($2000) versus using t-PA ($170 including nursing time). Conclusion:,Cathflo is not just safe and practical to use but also cost effective. [source] Observer-based stabilization of linear switching systemsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 14 2009Paolo Caravani Abstract The discrete component of the hybrid state of a discrete-time linear switching system is assumed to be uncontrolled and unobserved. Conditions of stabilizability for this class of systems are given in terms of a new definition of control invariance, based on the realization of a discrete observer that permits reconstruction of the discrete-state in certain intervals of the time basis. This paper highlights the relationship between the minimum dwell time of the system and its stabilizability. An almost complete characterization of stabilizability is offered in terms of certain subsets of the continuous-state space. These sets are amenable to tractable parametric procedures for controller synthesis. Copyright © 2008 John Wiley & Sons, Ltd. [source] Exponential H, filtering for switched linear systems with interval time-varying delayINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 5 2009Dong Wang Abstract This paper deals with the problem of exponential H, filtering for a class of continuous-time switched linear system with interval time-varying delay. The time delay under consideration includes two cases: one is that the time delay is differentiable and bounded with a constant delay-derivative bound, whereas the other is that the time delay is continuous and bounded. Switched linear filters are designed to ensure that the filtering error systems under switching signal with average dwell time are exponentially stable with a prescribed H, noise attenuation level. Based on the free-weighting matrix approach and the average dwell technology, delay-dependent sufficient conditions for the existence of such a filter are derived and formulated in terms of linear matrix inequalities (LMIs). By solving that corresponding LMIs, the desired filter parameterized matrices and the minimal average dwell time are obtained. Finally, two numerical examples are presented to demonstrate the effectiveness of the developed results. Copyright © 2008 John Wiley & Sons, Ltd. [source] Exponential H, filtering for uncertain discrete-time switched linear systems with average dwell time: A µ-dependent approachINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 11 2008Lixian Zhang Abstract In this paper, the problem of exponential H, filter problem for a class of discrete-time polytopic uncertain switched linear systems with average dwell time switching is investigated. The exponential stability result of the general discrete-time switched systems using a discontinuous piecewise Lyapunov function approach is first explored. Then, a new µ- dependent approach is proposed, which means the analysis or synthesis of the underlying systems is dependent on the increase degree µ of the piecewise Lyapunov function at the switching instants. A mode-dependent full-order filter is designed such that the developed filter error system is robustly exponentially stable and achieves an exponential H, performance. Sufficient existence conditions for the desired filter are derived and formulated in terms of a set of linear matrix inequalities, and consequently the minimal average dwell time and the corresponding filter are obtained from such conditions for a given system decay degree. A numerical example is presented to demonstrate the potential and effectiveness of the developed theoretical results. Copyright © 2007 John Wiley & Sons, Ltd. [source] Express guideway transit: A case for further development in transit automationJOURNAL OF ADVANCED TRANSPORTATION, Issue 2 2002Justin Batelaan Safe and reliable coupling and decoupling of cars from a moving train is feasible with further developments in linear motor propulsion and control of transit vehicles. This allows the last car of a train to decouple and stop at a station for a relative long dwell time, before it accelerates and is coupled to a following train. Controlled doors in front and rear of the transit vehicle permit passengers to walk through the train to the car which stops at their destination. A proposed transit system using these features is described and compared to Bombardier's Advanced Rapid Transit. Potential advantages are high schedule speed, uncrowded trains, smaller and more stations, low energy requirements and a smaller vehicle fleet. [source] In vitro monitoring of surface mechanical properties of poly(L -lactic acid) using microhardnessJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007C. Saiz-Arroyo Abstract Poly(L -lactic acid) (PLLA) was immersed in a simulated body fluid (SBF) solution at 37.5°C for distinct times. The variation of the surface mechanical properties of PLLA samples with immersion time was followed by microhardness. These measurements showed that PLLA microhardness decreased significantly (, 60%) after only 30 days of immersion. The results were explained in terms of hydrolytic degradation of the samples. The dependence of microhardness with the applied dwell time was also analyzed. The creep curves were successfully described by a power law. A decrease of the creep constant k as the immersion time increased was found. Differential scanning calorimetry was also used to analyze the changes in the physical properties of PLLA, namely in crystallinity degree (Xc) and glass transition temperature (Tg), as a function of the immersion time in SBF. A significant variation in the crystallinity degree of PLLA, initially nearly amorphous (Xc = 9%), was detected after only 3 days of immersion (Xc = 37%). The interpretation of this behavior was based on the hydrolysis process suffered by PLLA. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] JOURNAL of FOOD PROCESSING and PRESERVATION SEP 2000 Vol-24.4. DEVELOPMENT of A PROCESS FOR DETECTING NONTHERMAL EFFECTS of MICROWAVE ENERGY ON MICROORGANISMS AT LOW TEMPERATURE,JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 4 2000MICHAEL KOZEMPEL We developed an experimental process capable of isolating thermal and nonthermal effects of microwave energy relative to the destruction of microorganisms at low temperature. the concept combines instantaneous energy input to the food system by microwaves with rapid removal of thermal energy. the process used a double tube heat exchanger inside a continuous microwave dryer. the outer tube was transparent to microwaves, whereas the inner tube was stainless steel and was used for cooling the system. the microwave energy, 5,6 kW power, was absorbed by the process fluid in the annulus. the cooling water flowing in the inner tube removed the thermal energy from the process fluid to control temperature at or below 45C. the process was at turbulent flow to assure a uniform temperature and dwell time. There were no detected nonthermal effects from microwave energy for yeast, Pediococcus sp., Escherichia coli, Listeria innocua, or Enterobacter aerogenes in various test fluids, such as water, liquid egg, beer, apple juice, apple cider, and tomato juice. [source] Thermal Properties, Heat Sealability and Seal Attributes of Whey Protein Isolate/ Lipid Emulsion Edible FilmsJOURNAL OF FOOD SCIENCE, Issue 7 2001S-J. Kim ABSTRACT: From 5% w/v whey protein isolate (WPI), whey protein/lipid emulsion edible films were produced that were sorbitol- or glycerol-plasticized, containing butterfat (0.2% w/v) or candelilla wax (0.8% w/v). Thermal properties of the films determined by Differential Scanning Calorimetry (DSC) showed onset temperatures (To) of 126 to 127 °C for sorbitol- and 108 to 122 °C for glycerol-plasticized films. To values were used as the basis for heat sealing temperatures. Temperature (110, 120, 130 °C), pressure (296,445 kPa), and dwell time (1,3 s) affected seal strength. Optimum heat sealing temperature was 130 °C for sorbitol- and 110 °C for glycerol-plasticized films. All films were heat sealable with an impulse heat-sealer. Electron Spectroscopy for Chemical Analysis (ESCA) of the surfaces of both sealed and unsealed films showed increase in hydrogen and covalent bonds involving C-O-H and N-C, which may be the main forces responsible for the sealed joint formation of the films. [source] Release liner removal method for transdermal drug delivery systems (TDDS)JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2010Anna M. Wokovich Abstract A release liner removal test is a valuable test for assessing the quality of a transdermal drug delivery system (i.e., TDDS, patch). This test measures the force required to remove the release liner from a patch. The objective of the present study was to establish sample preparation and instrument parameters for measuring release liner removal adhesion for TDDS. Ten TDDS were evaluated (six drugs for a total of 29 lots). Patches which had a rate-controlling membrane were run as-is, since they could not be cut to a precise width without sacrificing their structural integrity. Patches that were square or rectangular in shape were run as-is, and the width of these patches was determined using a digital caliper. Patches which were not square or rectangular in shape and did not have a rate-controlling membrane were cut to a precise width using a specimen cutter. Double-sided tape was used to adhere the liner side of the transdermal system to a clean stainless steel test panel. A release liner peel adhesion method for TDDS is proposed using a dwell time of approximately 3,min, a peel angle of 90°, and a peel speed of 300,mm/min. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:3177,3187, 2010 [source] Theoretical Investigation of Heat Transfer in Glass FormingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2001Raymond Viskanta A theoretical study to investigate internal heat transfer in glass undergoing cooling between glass and mold, as well as plunger, during and after pressing, is described. A thermal model has been formulated to simulate the cooling. The heat-transfer analysis accounts for the spectral nature of radiation in glass, the dependence of the thermophysical properties of glass on temperature, and the contact heat transfer between and after pressing, as well as subsequent cooling. Heat exchange between glass and mold by contact conduction across a very small gap and that by thermal radiation are considered separately. Numerical solutions have been obtained for typical conditions simulating symmetric and nonsymmetric cooling, and the results obtained are presented and discussed. During the dwell time, thermal-contact conduction between glass and mold is the dominant mechanism for heat extraction from glass. Results show that radiation from the surface of the glass plays a relatively small role in the heat extraction from the glass, but that radiation from the interior of the glass is much more significant. [source] Epidural Catheter Analgesia in Dogs and Cats: Technique and Review of 182 Cases (1991,1999)JOURNAL OF VETERINARY EMERGENCY AND CRITICAL CARE, Issue 2 2001Bernie D. Hansen DVM, DACVECC Abstract Objective: To characterize the indications and techniques for catheterization of the epidural space to treat pain in dogs and cats in a veterinary teaching hospital intensive care unit, and describe the analgesic regimens used in those patients. To provide a detailed description of the technique of epidural catheterization in companion animals. Design: Retrospective case series and clinical practice review. Setting: The Veterinary Teaching Hospital at the North Carolina State University College of Veterinary Medicine. Animals: Records from 160 dogs and 22 cats that had epidural catheters placed were identified. Interventions: Epidural catheterization for the purpose of providing analgesia for a variety of surgical and medical disorders was performed on both awake and anesthetized patients. Measurements and main results: The most frequently used analgesic agents were preservative-free morphine and bupivacaine. 2The range of duration of catheter dwell time was 1.3,332 hours, with a mean duration of 50 hours and a median of 39 hours. Suspicion of catheter malpositioning prompted radiographic imaging of the catheter in 44 patients, and malpositioning was confirmed in 6 of those. Catheter tip positioning was recorded in 46 patients. The tip was located at L3-L6 in 16, and T5-L3 in 30. Twenty-seven of those 30 patients were catheterized to treat pain associated with thoracotomy, forelimb amputation, pancreatitis, or peritonitis. Fifty-one (28%) patients received no analgesics beyond those provided by the epidural catheter. Conclusions: Epidural administration of analgesia appeared to provide significant pain relief and was adequate as a sole analgesic treatment in some patients. Serious complications in these critically ill animals appeared to be uncommon. (J Vet Emerg Crit Care 2001; 11(2): 95,103) [source] Investigation on the oxidation behaviour of gamma titanium aluminides coated with thermal barrier coatingsMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 7 2008R. Braun Abstract In the present study, the applicability of thermal barrier coatings (TBCs) on ,-TiAl alloys was investigated. Two alloys with the chemical compositions of Ti-45Al-8Nb-0.2B-0.15C and Ti-45Al-1Cr-6Nb-0.4W-0.2B-0.5C-0.2Si were used. Before TBC deposition, the specimens were pre-oxidised in laboratory air or low partial pressure oxygen atmosphere. Yttria partially stabilised zirconia top coats were then deposited using electron-beam physical vapour deposition (EB-PVD). The oxidation behaviour of the ,-TiAl specimens with TBC was studied by cyclic oxidation testing in air at 850 and 900,°C. Post-oxidation analysis of the coating systems was performed using scanning electron microscopy with energy-dispersive X-ray spectroscopy (EDS). No spallation of the TBC was observed for pre-oxidised specimens of both alloys when exposed to air at 850,°C for 1100 cycles of 1,h dwell time at high temperature. SEM micrographs of the thermally grown oxide scale revealed outer mixed TiO2/Al2O3 protrusions with a columnar structure. The protrusions contained small particles of zirconia and a low amount of about 0.5 at% zirconium was measured by EDS analysis throughout this outer oxide mixture. The TBCs exhibited excellent adherence on the oxide scale. Intercolumnar gaps and pores in the root area of the TBC were filled with titania and alumina. Below the outer columnar oxide scale, a broad porous zone of predominant titania was observed. The transition region between the oxide scale and substrate consisted of a discontinuous nitride layer intermixed with alumina particles and intermetallic phases rich in niobium formed at the nitride layer/substrate interface. When thermally cycled at 900,°C, the oxide scales on the alloy Ti-45Al-8Nb-0.2B-0.15C pre-oxidised in low partial pressure oxygen spalled off after 540 cycles. For the sample with TBC, spallation was observed after 810 cycles. Failure occurred in the thermally grown oxide near the oxide/nitride layer interface. Microstructural examinations revealed again oxide scales with columnar structure beneath the zirconia top coat and good adherence of the TBC on the thermally grown oxides formed at 900,°C. [source] The Effect of pH on the Topography of Porphyrins in Lipid Membranes,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2005Irena Bronshtein ABSTRACT The effect of the acidity of the environment on the topography and photophysics of sensitizer molecules in homogeneous solutions, and when embedded in a lipid microenvironment, was studied. Four hematoporphyrin (HP) analogs were studied, which have chemical "spacers" of varying lengths between the chromophoric tetrapyrrole and the carboxylate moiety. These derivatives have essentially the same chemical attributes and reactivity as the parent compound, HP IX, which is used in clinical procedures of photodynamic therapy. The binding constants of these HP derivatives to membrane model systems increase with the length of carboxylate chain in the pH range 3.0,6.6. This effect of chain length is attributed to an increase in the hydrophobicity of the molecule on elongation of the alkyl chains. A strong pH dependence of the quenching efficiency of the porphyrins' fluorescence by iodide ions was observed in aqueous solution and is attributed to a unique electrostatic interaction between the fluorophore and the quencher. The quenching efficiency in liposomes, relative to the quenching in buffer, as a function of pH, shows that porphyrins in the neutral form penetrate deeper inside the lipid bilayer and are less exposed to external quenching than when negatively charged at the carboxylic moiety. This vertical displacement in the membrane is also evidenced in the effect of pH on the photosensitized oxidation efficiency of a membrane-bound chemical target. Increasing the pH causes a significant decrease in the sensitization efficiency in liposomes. This trend is attributed to the vertical localization, and protonation of the carboxylic groups on lowering the pH leads to sinking of the sensitizer into the lipid bilayer and to a consequent generation of singlet oxygen at a deeper point. This increases the dwell time of singlet oxygen within the bilayer, which results in greater photodamage to a membrane-residing singlet oxygen target. [source] Ca2+ -dependent components of inactivation of unitary cardiac L-type Ca2+ channelsTHE JOURNAL OF PHYSIOLOGY, Issue 1 2010Ira R. Josephson A Ca2+ ion-dependent inactivation (CDI) of L-type Ca2+ channels (LCC) is vital in limiting and shaping local Ca2+ ion signalling in a variety of excitable cell types. However, under physiological conditions the unitary LCC properties that underlie macroscopic inactivation are unclear. Towards this end, we have probed the gating kinetics of individual cardiac LCCs recorded with a physiological Ca2+ ion concentration (2 mm) permeating the channel, and in the absence of channel agonists. Upon depolarization the ensemble-averaged LCC current decayed with a fast and a slow exponential component. We analysed the unitary behaviour responsible for this biphasic decay by means of a novel kinetic dissection of LCC gating parameters. We found that inactivation was caused by a rapid decrease in the frequency of LCC reopening, and a slower decline in mean open time of the LCC. In contrast, with barium ions permeating the channel ensemble-averaged currents displayed only a single, slow exponential decay and little time dependence of the LCC open time. Our results demonstrate that the fast and slow phases of macroscopic inactivation reflect the distinct time courses for the decline in the frequency of LCC reopening and the open dwell time, both of which are modulated by Ca2+ influx. Analysis of the evolution of CDI in individual LCC episodes was employed to examine the stochastic nature of the underlying molecular switch, and revealed that influx on the order of a thousand Ca2+ ions may be sufficient to trigger CDI. This is the first study to characterize both the unitary kinetics and the stoichiometry of CDI of LCCs with a physiological Ca2+ concentration. These novel findings may provide a basis for understanding the mechanisms regulating unitary LCC gating, which is a pivotal element in the local control of Ca2+ -dependent signalling processes. [source] High Pressure Processing , a Database of Kinetic InformationCHEMIE-INGENIEUR-TECHNIK (CIT), Issue 8 2008R. Buckow Abstract Hydrostatic high pressure technology is relatively new to food industry and is more and more considered as an alternative to traditional preservation methods like heat processing. The inactivation of bacteria, spores, viruses and enzymes has been demonstrated in numerous papers, and various schemes for modelling the experimental inactivation data have been suggested. Although there are similarities to heat inactivation kinetics it is generally agreed that the heat process safety assessment with its typical indicator organisms cannot simply be transferred to high pressure treatment. In this paper a database is introduced which aims at the comparison of published kinetic high pressure inactivation data by using suitable mathematical modelling tools. For the sake of clarity, the functional associations of pressure, temperature and exposure time is presented by means of pressure-temperature diagrams (pT -diagrams), which show pressure-temperature combinations yielding to a desired reaction (e.g. inactivation) rate constant. Thus, the database software was particularly designed to enable the user to call up pressure-temperature dependent function equations for a number of micro-organisms, enzymes and food constituents and to visualize them in pT -diagrams for predetermined treatment times or as kinetics under predetermined p - T conditions. In addition, the database also features a simple calculator tool which allows the user to make an entry in three of the four process conditions (pressure level, temperature level, inactivation level, dwell time) and calculate the remaining forth process condition. The database is accessible through the internet and is continuously updated on the basis of the most recent publications and own experimental data. [source] Nitrogen-doped zirconia single crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2006T.-C. Rödel Abstract The aim of this work is the preparation of nitrogen-doped single crystals of cation-stabilized zirconia. Thin plates of these crystals were nitrided in a graphite heated resistance furnace with nitrogen as reaction gas. Several dwell times and reaction temperatures were tested and their effect on the amount of incorporated nitrogen is investigated. During nitridation at high temperatures a rock salt-type ,ZrN' layer grows on the surface, leading to the destruction of the crystal. In contrast to the fluorite-type bulk material, which can be described as a fast anion conductor, the surface layer shows electronic conductivity. For possible applications of the bulk material (solid electrolyte) the formation of the surface layer must be avoided. Therefore, the interface between surface epilayer and bulk material was investigated in detail by electron microscopy methods. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Size Effect on Properties of Varistors Made From Zinc Oxide Nanoparticles Through Low Temperature Spark Plasma SinteringADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Léna Saint Macary Abstract Conditions for the elaboration of nanostructured varistors by spark plasma sintering (SPS) are investigated, using 8-nm zinc oxide nanoparticles synthesized following an organometallic approach. A binary system constituted of zinc oxide and bismuth oxide nanoparticles is used for this purpose. It is synthesized at room temperature in an organic solution through the hydrolysis of dicyclohexylzinc and bismuth acetate precursors. Sintering of this material is performed by SPS at various temperatures and dwell times. The determination of the microstructure and the chemical composition of the as-prepared ceramics are based on scanning electron microscopy and X-ray diffraction analysis. The nonlinear electrical characteristics are evidenced by current,voltage measurements. The breakdown voltage of these nanostructured varistors strongly depends on grain sizes. The results show that nanostructured varistors are obtained by SPS at sintering temperatures ranging from 550 to 600,°C. [source] Dip-Pen Nanolithography Using the Amide-Coupling Reaction with Interchain Carboxylic Anhydride- Terminated Self-Assembled Monolayers,ADVANCED FUNCTIONAL MATERIALS, Issue 8 2006S. Chi Abstract Herein we report on a new type of dip-pen nanolithography (DPN), which utilizes an interfacial organic reaction,the amide-coupling reaction,between chemically activated surfaces and amine ink molecules transferred from an atomic force microscopy tip. As a representative of the chemically activated surfaces that could react with amine compounds, we formed a self-assembled monolayer terminating in interchain carboxylic anhydride (ICA) groups on gold, and generated chemically derived nanopatterns using alkylamines as ink molecules. Amine inks showed diffusive behavior similar to thiol inks on gold in conventional DPN, and the pattern sizes were controlled by changing the tip dwell times. In addition, nanopatterns of hydrolyzed ICAs were generated by taking advantage of the participation of the water meniscus in the DPN process and the chemical nature of the ICAs. [source] Development of a multi-residue method for the determination of 18 carbamates in tobacco by high-performance liquid chromatography/positive electrospray ionisation tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2006B. Mayer-Helm A multi-residue method for the determination of carbamates in tobacco was developed by high-performance liquid chromatography (HPLC) triple quadrupole mass spectrometry (MS). A rapid sample preparation consisted of an extraction step with methanol, centrifugation and 1:1 dilution with aqueous 10,mM ammonium acetate. After filtration these extracts were directly analysed by reversed-phase HPLC coupled to positive electrospray ionisation tandem mass spectrometry operated in the multiple reaction monitoring mode. Capillary voltage and dwell times were optimised to reduce matrix effects and to increase sensitivity. The method was validated for the determination of 18 carbamates in three main types of raw tobacco and three tobacco products. The interday accuracy ranged between 80 and 110% with a relative standard deviation (RSD) of <30%. The limits of quantification (LOQs) ranged between 0.01 and 0.04,ppm for almost all carbamates, except aldicarb sulfone, carbofuran, and pebulate, with LOQs between 0.10 and 0.20,ppm. These LOQs were clearly below the guidance residue levels defined by the Agrochemical Advisory Committee of CORESTA, an association of organisations having scientific research relative to tobacco. Copyright © 2006 John Wiley & Sons, Ltd. [source] Piecewise analysis and modeling of circuit pack temperature cycling dataBELL LABS TECHNICAL JOURNAL, Issue 3 2006Toby Joyce Temperature cycling environmental stress testing (EST) of circuit packs is a standard test procedure for the precipitation of latent defects in order to minimize early product lifecycle customer returns. EST is an expensive, energy-intensive bottleneck in the manufacturing process, one that is based on empiricisms that may be out of date. This presents great opportunity for optimization and test cost reduction. This paper describes the characterization of temperature cycling through analysis and modeling of process data in order to optimize the test parameters,ramp rate, temperature extremes, dwell times, and number of cycles. Failure data from circuit packs tested at a Lucent facility is analyzed using a regression technique and graphical inspection. The dwell and ramp periods of the test are considered in a piecewise manner. A cost model is applied based on distributions fitted to the failure data. The analysis yields a methodology for the dynamic, value-based optimization of temperature cycling EST. © 2006 Lucent Technologies Inc. [source] | |||||||||||||||||||||||||