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Temperature Rise (temperature + rise)
Selected AbstractsPain and Anatomical Locations of Radiofrequency Ablation as Predictors of Esophageal Temperature Rise During Pulmonary Vein IsolationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2008ARASH ARYANA M.D. Introduction: Esophageal temperature rise (ETR) during ablation inside left atrium has been reported as a marker for esophageal thermal injury. We sought to investigate the possible relationships between chest pain and ETR during radiofrequency (RF) ablation, and ETR and locations of RF application, in patients undergoing pulmonary vein (PV) isolation under moderate sedation. Methods and Results: We analyzed anatomical locations of each RF application and its association with esophageal temperature and presence/absence of pain. Data from 40 consecutive patients (mean age: 56 ± 10 years) were analyzed. There were a total of 4,071 RF applications resulting in 291 episodes of pain (7.1%) and 223 ETRs (5.5%). Thirty-five patients (87.5%) experienced at least one pain episode and 32 (80.0%) had at least one ETR. While 77.4% of posterior wall applications that caused pain also corresponded to an ETR (P < 0.0001), only 0.8% of pain-free posterior wall applications were associated with ETRs (P < 0.0001). The sensitivity and specificity of pain during ablation for ETR were 94% and 98%, respectively. No ETRs were observed during anterior wall applications. ETRs occurred more frequently during ablation on the left (86.1%) versus the right (13.9%), and in inferior (70.4%) versus superior (29.6%) segments. Conclusion: In patients undergoing PV isolation, ETR was encountered when ablating in the posterior left atrium with the distribution left > right and inferior > superior. Pain during ablation was associated with ETR, and lack of pain was strongly associated with absence of ETR. Pain during RF ablation may thus serve as a predictor of esophageal heating and potential injury. [source] Analysis of temperature distribution near the crack tip under constant amplitude loadingFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2008K. N. PANDEY ABSTRACT An analytical/numerical method has been developed to find the temperature rise near the crack tip under fatigue loading. The cyclic plastic zone ahead of the crack tip is assumed to be the shape of the source of heat generation and some fraction of plastic work done in cyclic plastic zone as heat generation. Plastic work during fatigue load was found by obtaining stress and strain distribution within the plastic zone by Hutchinson, Rice and Rosengren (HRR) crack tip singularity fields applied to small scale yielding on the cyclic stress strain curve. A two-dimensional conduction heat transfer equation, in moving co-ordinates, was used to obtain temperature distribution around the crack tip. Temperature rise was found to be a function of frequency of loading, applied stress intensity factor and thermal properties of the material. A power,law relation was found between the rise in temperature at a fixed point near the crack tip and range of stress intensity factor. [source] Pulp capping with adhesive resin-based composite vs. calcium hydroxide: a reviewDENTAL TRAUMATOLOGY, Issue 6 2000A. H. B. Schuurs Abstract , The results of some short-term experiments suggest that direct capping of a vital pulp with the modern resin-based composite systems may be as effective as capping with calcium hydroxide. Total cavity etching with 10% phosphoric acid seems to be safe for the exposed pulp, but unless annulled by calcium hydroxide 35% phosphoric acid may be disastrous. For hemostasis and cleaning of the pulp wound both sodium hypochlorite and saline seem suitable, whereas the effectiveness of a 2% chlorhexidine solution is questionable. Although hard-setting calcium hydroxide cements may induce the formation of dentin bridges, they appear not to provide an effective long-term seal against bacterial factors. Within a few years, the majority of mechanically exposed and capped pulps show infection and necrosis due to microleakage of such capping materials and tunnel defects in the dentin bridges. It is unknown whether newer types of resin containing calcium-hydroxide-products will act as a permanent barrier. The cytotoxicity of the resin-based composites and the temperature rise during polymerisation may not be of concern, but microleakage, sensitisation and allergic reactions may pose problems. Based on available data, pulp capping with resin-based composites may be said to be promising, but more and long-term research is mandatory before the method can be recommended. [source] Effect of irradiation type (LED or QTH) on photo-activated composite shrinkage strain kinetics, temperature rise, and hardnessEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 6 2002Norbert Hofmann This study compares commercially available light-emitting diode (LED) lights with a quartz tungsten halogen (QTH) unit for photo-activating resin-based composites (RBC). Shrinkage strain kinetics and temperature within the RBC were measured simultaneously using the ,deflecting disc technique' and a thermocouple. Surface hardness (Knoop) at the bottom of 1.5-mm thick RBC specimens was measured 24 h after irradiation to indicate degree of cure. Irradiation was performed for 40 s using either the continuous or the ramp-curing mode of a QTH and a LED light (800 mW cm,2 and 320 mW cm,2, respectively) or the continuous mode of a lower intensity LED light (160,mW cm,2). For Herculite XRV and Filtek Z250 (both containing only camphoroquinone as a photo-initiator) the QTH and the stronger LED light produced similar hardness, while in the case of Definite (containing an additional photo-activator absorbing at lower wavelength) lower hardness was observed after LED irradiation. The temperature rise during polymerization and heating from radiation were lower with LED compared to QTH curing. The fastest increase of polymerization contraction was observed after QTH continuous irradiation, followed by the stronger and the weaker LED light in the continuous mode. Ramp curing decreased contraction speed even more. Shrinkage strain after 60 min was greater following QTH irradiation compared with both LED units (Herculite, Definite) or with the weaker LED light (Z250). [source] Analysis of temperature distribution near the crack tip under constant amplitude loadingFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2008K. N. PANDEY ABSTRACT An analytical/numerical method has been developed to find the temperature rise near the crack tip under fatigue loading. The cyclic plastic zone ahead of the crack tip is assumed to be the shape of the source of heat generation and some fraction of plastic work done in cyclic plastic zone as heat generation. Plastic work during fatigue load was found by obtaining stress and strain distribution within the plastic zone by Hutchinson, Rice and Rosengren (HRR) crack tip singularity fields applied to small scale yielding on the cyclic stress strain curve. A two-dimensional conduction heat transfer equation, in moving co-ordinates, was used to obtain temperature distribution around the crack tip. Temperature rise was found to be a function of frequency of loading, applied stress intensity factor and thermal properties of the material. A power,law relation was found between the rise in temperature at a fixed point near the crack tip and range of stress intensity factor. [source] Test method for concrete spalling using small electric furnaceFIRE AND MATERIALS, Issue 4 2010Ren Zhao Abstract Concrete spalling can cause severe damage to concrete structure when exposed to fire. The spalling mechanisms are not very well understood. For the testing of spalling, full-scale structural members should be used, as spalling tests are sensitive to size effects. Full-scale testing in large furnace is costly and is not suitable for testing large number of concrete mixture trials. The standard and hydrocarbon fire time,temperature curves have rapid temperature rise during the initial phase. This temperature rise requires a gas furnace with high heating capacity and cannot be generated by electric muffle furnace commonly available in many laboratories. This paper presents a method to carry out spalling test in small-scale specimens with exposure to rapid temperature rise using a commonly available electric furnace in the laboratories. The tests are based on 150,mm diameter cylinders that are laterally confined to simulate full-scale structural members. The cylinder surface is exposed to rapid temperature rise by exposing through vertical and/or horizontal holes in pre-heated small electric furnace. Some unconfined 100,mm diameter cylinders were also exposed horizontally to test the performance of confinement. The paper shows that the hydrocarbon fire and standard fire exposure can be simulated by manipulating the exposure location of the surface of the concrete cylinder. Ordinary Portland cement concrete cylinders with different strengths were tested and different spalling patterns were observed. The spalling patterns matched the test results from a gas furnace fire test simulating the fire curves. The tests demonstrated that the method is an effective and convenient technique to predict the spalling risk of a concrete. Copyright © 2009 John Wiley & Sons, Ltd. [source] Determination of activation temperature of glass bulb sprinklers using a thermal liquid bathFIRE AND MATERIALS, Issue 4 2006Mohammed M. Khan Abstract A thermal liquid bath was used to determine the activation temperature of a wide range of temperature rated (57,182°C) glass bulb (3 and 5 mm diameters) sprinklers using water and glycerine. An optical switch and a thermocouple were installed adjacent to each sprinkler (within 10 mm) to record the activation of each glass bulb in the liquid bath having a uniform temperature distribution (±0.5°C). All the tests for determining the activation temperatures of glass bulb sprinklers were conducted in the liquid bath using a 0.277°C/min rate of temperature rise. Based on a heat transfer analysis, this rate is within the maximum allowable rate of rise of water and glycerine temperatures, which allows the glass bulb temperature to closely follow the liquid temperature. The sprinkler activation temperature was evaluated in terms of percentage rating, which is expressed as the percent variation of the average activation temperature, as measured in the liquid bath, from the nominal rated temperature. Sprinklers (93°C rated or lower) activation temperatures in water were consistently within ±3.5% of rating. In glycerine, the activation temperatures of sprinklers rated between 93 and 182°C performed within 3.5% of their rating. Copyright © 2005 John Wiley & Sons, Ltd. [source] Technical basis on structural fire resistance design in building standards law of JapanFIRE AND MATERIALS, Issue 2-4 2004Kazunori Harada Abstract Structural fire resistance design method came into effect due to the revision of Japan's building code (building standards law of Japan) in June 2001. The method includes standard methods to calculate (1) fire exposure to structural elements, (2) temperature rise of steel and RC elements during fire exposure and (3) structural end points such as ultimate steel temperature for buckling of columns, bending failure of beams and so on. This paper discusses the technical basis for design methods especially focused on steel framed buildings. The calculated values by design equations were compared with experimental values in order to examine the redundancies implied. In the final stage, all the redundancies were combined by Monte-Carlo method and first-order moment method (AFORM). Target safety index and corresponding partial safety factors were discussed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Effects of temperature and sediment properties on benthic CO2 production in an oligotrophic boreal lakeFRESHWATER BIOLOGY, Issue 8 2010IRINA BERGSTRÖM Summary 1. Temperature and many other physical and chemical factors affecting CO2 production in lake sediments vary significantly both seasonally and spatially. The effects of temperature and sediment properties on benthic CO2 production were studied in in situ and in vitro experiments in the boreal oligotrophic Lake Pääjärvi, southern Finland. 2. In in situ experiments, temperature of the water overlying the shallow littoral sediment varied seasonally between 0.5 and 15.7 °C, but in deep water (,20 m) the range was only 1.1,6.6 °C. The same exponential model (r2 = 0.70) described the temperature dependence at 1.2, 10 and 20 m depths. At 2.5 and 5 m depths, however, the slopes of the two regression models (r2 = 0.94) were identical but the intercept values were different. Sediment properties (wet, dry, mineral and organic mass) varied seasonally and with depth, but they did not explain a significantly larger proportion of variation in the CO2 output rate than temperature. 3. In in vitro experiments, there was a clear and uniform exponential dependence of CO2 production on temperature, with a 2.7-fold increase per 10 °C temperature rise. The temperature response (slope of regression) was always the same, but the basic value of CO2 production (intercept) varied, indicating that other factors also contributed to the benthic CO2 output rate. 4. The annual CO2 production of the sediment in Lake Pääjärvi averaged 62 g CO2 m,2, the shallow littoral at 0,3 m depth releasing 114 g CO2 m,2 and deep profundal (>15 m) 30 g CO2 m,2. On the whole lake basis, the shallow littoral at 0,3 m depth accounted for 53% and the sediment area in contact with the summer epilimnion (down to a depth c. 10 m) 75% of the estimated total annual CO2 output of the lake sediment, respectively. Of the annual production, 83% was released during the spring and summer. 5. Using the temperature-CO2 production equations and climate change scenarios we estimated that climatic warming might increase littoral benthic CO2 production in summer by nearly 30% from the period 1961,90 to the period 2071,2100. [source] Combined effects of elevated temperatures and reduced leaf litter quality on the life-history parameters of a saprophagous macroarthropodGLOBAL CHANGE BIOLOGY, Issue 1 2009JEAN-FRANCOIS DAVID Abstract Because soil macroinvertebrates strongly modify decomposition processes, it is important to know how their abundance will respond to global change. We investigated in laboratory microcosms, the effects of elevated temperatures and reduced leaf litter quality on the life-history traits of a saprophagous macroarthropod (development time, growth, survival and reproduction). Millipedes (Polydesmus angustus) from an Atlantic temperate forest were reared throughout their life cycle (,16 months) under two temperature regimes differing on average by 3.3 °C; in a factorial design, they were fed either on Atlantic leaf litter or on Mediterranean leaf litter with a higher C : N ratio; humidity was consistently high. The components of the population growth rate (r) were affected positively by the temperature rise and negatively by the switch from Atlantic to Mediterranean leaf litter. When both treatments were combined, litter effects offset temperature effects. These results show that the short-term response of saprophagous macroarthropods to warming is positive but depends on the availability of high-quality litter, which is difficult to predict in the global change context. In a parallel experiment, conspecific millipedes from a Mediterranean population, which have evolved for a long time in a warmer climate and on poor-quality litter, were reared at elevated temperatures on Mediterranean leaf litter. All components of r were higher than in the Atlantic population under the same conditions. This suggests that in the longer term, macroarthropods can overcome detrimental trophic interactions. Based on our study and the literature, we conclude that for decades the positive effects of warming on saprophagous macrofauna should exceed the negative effects of changes in litter quality. The abundance of those organisms in temperate forests could increase, which is confirmed by latitudinal patterns in Europe. Studies aimed at predicting the impacts of global change on decomposition will need to consider interactions with soil macroinvertebrates. [source] Climate warming, dispersal inhibition and extinction riskGLOBAL CHANGE BIOLOGY, Issue 3 2008MANUEL MASSOT Abstract Global warming impels species to track their shifting habitats or adapt to new conditions. Both processes are critically influenced by individual dispersal. In many animals, dispersal behaviour is plastic, but how organisms with plastic dispersal respond to climate change is basically unknown. Here, we report the analysis of interannual dispersal change from 16 years of monitoring a wild population of the common lizard, and a 12-year manipulation of lizards' diet intended to disentangle the direct effect of temperature rise on dispersal from its effects on resource availability. We show that juvenile dispersal has declined dramatically over the last 16 years, paralleling the rise of spring temperatures during embryogenesis. A mesoscale model of metapopulation dynamics predicts that in general dispersal inhibition will elevate the extinction risk of metapopulations exposed to contrasting effects of climate warming. [source] Performance of High Arctic tundra plants improved during but deteriorated after exposure to a simulated extreme temperature eventGLOBAL CHANGE BIOLOGY, Issue 12 2005Fleur L. Marchand Abstract Arctic ecosystems are known to be extremely vulnerable to climate change. As the Intergovernmental Panel on Climate Change scenarios project extreme climate events to increase in frequency and severity, we exposed High Arctic tundra plots during 8 days in summer to a temperature rise of approximately 9°C, induced by infrared irradiation, followed by a recovery period. Increased plant growth rates during the heat wave, increased green cover at the end of the heat wave and higher chlorophyll concentrations of all four predominating species (Salix arctica Pall., Arctagrostis latifolia Griseb., Carex bigelowii Torr. ex Schwein and Polygonum viviparum L.) after the recovery period, indicated stimulation of vegetative growth. Improved plant performance during the heat wave was confirmed at plant level by higher leaf photochemical efficiency (Fv/Fm) and at ecosystem level by increased gross canopy photosynthesis. However, in the aftermath of the temperature extreme, the heated plants were more stressed than the unheated plants, probably because they acclimated to warmer conditions and experienced the return to (low) ambient as stressful. We also calculated the impact of the heat wave on the carbon balance of this tundra ecosystem. Below- and aboveground respiration were stimulated by the instantaneous warmer soil and canopy, respectively, outweighing the increased gross photosynthesis. As a result, during the heat wave, the heated plots were a smaller sink compared with their unheated counterparts, whereas afterwards the balance was not affected. If other High Arctic tundra ecosystems react similarly, more frequent extreme temperature events in a future climate may shift this biome towards a source. It is uncertain, however, whether these short-term effects will hold when C exchange rates acclimate to higher average temperatures. [source] Carbon emission and sequestration by agricultural land use: a model study for EuropeGLOBAL CHANGE BIOLOGY, Issue 6 2002L. M. Vleeshouwers Abstract A model was developed to calculate carbon fluxes from agricultural soils. The model includes the effects of crop (species, yield and rotation), climate (temperature, rainfall and evapotranspiration) and soil (carbon content and water retention capacity) on the carbon budget of agricultural land. The changes in quality of crop residues and organic material as a result of changes in CO2 concentration and changed management were not considered in this model. The model was parameterized for several arable crops and grassland. Data from agricultural, meteorological, soil, and land use databases were input to the model, and the model was used to evaluate the effects of different carbon dioxide mitigation measures on soil organic carbon in agricultural areas in Europe. Average carbon fluxes under the business as usual scenario in the 2008,2012 commitment period were estimated at 0.52 tC ha,1 y,1 in grassland and ,0.84 tC ha,1 y,1 in arable land. Conversion of arable land to grassland yielded a flux of 1.44 tC ha,1 y,1. Farm management related activities aiming at carbon sequestration ranged from 0.15 tC ha,1 y,1 for the incorporating of straw to 1.50 tC ha,1 y,1 for the application of farmyard manure. Reduced tillage yields a positive flux of 0.25 tC ha,1 y,1. The indirect effect associated with climate was an order of magnitude lower. A temperature rise of 1 °C resulted in a ,0.05 tC ha,1 y,1 change whereas the rising CO2 concentrations gave a 0.01 tC ha,1 y,1 change. Estimates are rendered on a 0.5 × 0.5° grid for the commitment period 2008,2012. The study reveals considerable regional differences in the effectiveness of carbon dioxide abatement measures, resulting from the interaction between crop, soil and climate. Besides, there are substantial differences between the spatial patterns of carbon fluxes that result from different measures. [source] Assessing the results of scenarios of climate and land use changes on the hydrology of an Italian catchment: modelling studyHYDROLOGICAL PROCESSES, Issue 19 2010Daniela R. D'Agostino Abstract Hydrological models are recognized as valid scientific tools to study water quantity and quality and provide support for the integrated management and planning of water resources at different scales. In common with many catchments in the Mediterranean, the study catchment has many problems such as the increasing gap between water demand and supply, water quality deterioration, scarcity of available data, lack of measurements and specific information. The application of hydrological models to investigate hydrological processes in this type of catchments is of particular relevance for water planning strategies to address the possible impact of climate and land use changes on water resources. The distributed catchment scale model (DiCaSM) was selected to study the impact of climate and land use changes on the hydrological cycle and the water balance components in the Apulia region, southern Italy, specifically in the Candelaro catchment (1780 km2). The results obtained from this investigation proved the ability of DiCaSM to quantify the different components of the catchment water balance and to successfully simulate the stream flows. In addition, the model was run with the climate change scenarios for southern Italy, i.e. reduced winter rainfall by 5,10%, reduced summer rainfall by 15,20%, winter temperature rise by 1·25,1·5 °C and summer temperature rise by 1·5,1·75 °C. The results indicated that by 2050, groundwater recharge in the Candelaro catchment would decrease by 21,31% and stream flows by 16,23%. The model results also showed that the projected durum wheat yield up to 2050 is likely to decrease between 2·2% and 10·4% due to the future reduction in rainfall and increase in temperature. In the current study, the reliability of the DiCaSM was assessed when applied to the Candelaro catchment; those parameters that may cause uncertainty in model output were investigated using a generalized likelihood uncertainty estimation (GLUE) methodology. The results showed that DiCaSM provided a small level of uncertainty and subsequently, a higher confidence level. Copyright © 2010 John Wiley & Sons, Ltd. [source] Intracanal temperature rise evaluation during the usage of the System B: replication of intracanal anatomyINTERNATIONAL ENDODONTIC JOURNAL, Issue 4 2005J. C. Villegas Abstract Aim To evaluate and determine intracanal temperature rises at 2 and 4 mm from the working length (WL) necessary to obtain proper replication of intracanal anatomy with gutta-percha (GP) using the System B heat source during vertical condensation. Methodology A split-tooth model was prepared and artificial shallow depressions were cut in the buccal canal wall 2 and 4 mm from the WL. At the same level on the palatal wall holes were drilled to adapt two thermocouples. The canal was filled using GP in a vertical condensation technique by placing the System B plugger at 2 and 4 mm from the WL in groups A and B, respectively. Two control groups in which no GP was used were carried out placing the plugger 2 and 4 mm from the WL (groups A.c and B.c, respectively) and activating the heat source. Recording of temperature rise was carried out during the filling procedure for groups A and B and during activation for control groups A.c and B.c; the highest temperatures were recorded. After each filling was completed, 3 min were allowed for the GP to cool and the model divided to reveal the filling. Images of the GP were taken with a CCD camera to evaluate the presence of replication of artificial round depressions. In control groups, the temperature was recorded for 20 s after a 3 s activation of the heat source. The rise in temperature was compared between the groups individually at each level (2 or 4 mm) and statistically analysed using one-way anova and Fisher PLSD tests at 5% of significance level (P < 0.05). Results Mean temperature rises of 14 ± 3 and 12 ± 2 °C at 2 and 4 mm from the WL, respectively, were observed in group A fillings, and 4 ± 1 and 6 ± 1 °C at 2 and 4 mm, respectively, in group B fillings. Recordings at 2 mm showed significantly (P < 0.05) higher temperature rises with group A.c when compared with groups B and B.c. Replication of intracanal anatomy with GP was always found in group A fillings at both levels but only 4 mm from the WL in group B fillings. Conclusions Positioning the plugger close to WL and a temperature rise of 6 °C were necessary to obtain replication of intracanal anatomy. A mean temperature rise of 4 °C at 2 mm from WL (group B) resulted in no replication of intracanal anatomy. Further studies simulating clinical conditions are necessary. [source] Trans-admittance control for eliminating the temperature effect of piezoelectric transformer in the CCFL backlight moduleINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 8 2008Yu-Kang Lo Abstract A half-bridge (HB) resonant inverter for driving a cold cathode fluorescent lamp (CCFL) backlight module with a piezoelectric transformer (PT) is analyzed in this paper. The resonant inductance of the HB inverter is expressed as a function of the load current, the load resistance and the PT circuit parameters. Also, the trans-admittance of the PT-CCFL combination network is measured to track the operating frequency for the HB resonant inverter, which may be varied due to the temperature rise of PT. The lamp driving current and power can thus remain almost constant in a wide temperature range. Experiments show that the observed results match the theoretical analyses. Copyright © 2008 John Wiley & Sons, Ltd. [source] On the relationship between global warming, local warming in the Netherlands and changes in circulation in the 20th centuryINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 14 2003Geert Jan van Oldenborgh Abstract The temperature in De Bilt in the Netherlands has risen by 1 K over the 20th century. This rise parallels the rise in global temperature quite closely, albeit with a slightly higher amplitude. A linear relationship between the two, with a regression coefficient close to one, is an obvious first-order approximation. This is supported by the spatial homogeneity of global warming during the 20th century, the lack of seasonality in the temperature rise, and the residuals being almost white in time. The wind direction is used as a proxy for circulation type. Locally measured wind direction gives the same results as geostrophic wind direction from pressure stations, so that systematic errors are not likely to be large. The temperature in the Netherlands, on the edge of the continent, strongly depends on the wind direction. For most wind directions and seasons the average temperature per wind direction has increased. The exception is northeasterly winds in winter, in which the variability is too large to observe a trend. The increased temperature for each wind direction can explain the observed temperature rise in all seasons within the 95% error estimates. Changes in the distribution of wind directions explain most of the interannual variability of temperature. On longer time scales, these changes have led to cooler weather in the middle of the century, but no trend is discernible over the whole century. However, in late winter and spring there is clear evidence for a change in the frequency distribution of circulation patterns affecting the Netherlands over the second half of the 20th century. During the months of February to April, more days with southwesterly wind and fewer with northeasterlies have increased the temperature even more than the observed increase in temperature per wind direction. Copyright © 2003 Royal Meteorological Society [source] Studies on pyrolysis of vegetable market wastes in presence of heat transfer resistance and deactivationINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2005Ruby Ray Abstract In the present investigation, the pyrolysis of predried vegetable market waste (dp=5.03 mm) has been studied using a cylindrical pyrolyser having diameter of 250 mm under both isothermal and non-isothermal conditions within the temperature range of 523,923 K with an intention to investigate the effective contribution of different heat transfer controlling regime namely intra-particle, external along with kinetically control regime on the overall global rate of pyrolysis. Thermogravimetric method of analysis was utilized to obtain experimental data for both isothermal and non-isothermal cases by coupling a digital balance with the pyrolyser. The pyrolysis of vegetable market waste has been observed to exhibit deactivated concentration independent pyrolysis kinetics, analogous to catalytic poisoning, throughout the entire range of study. The deactivation is of 1st order up to 723 K and follows the 3rd order in the temperature range of 723 Rules-of-thumb of implementing short electric band heaters (length to diameter ratio <1.5) for external heating of pipe flowsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 2 2002X. D. Chen Abstract Short electric band heaters (L/Di<1.5) are constructed for the ease of implementation in small scale heating applications. They are usually mounted side-by-side in series along the external wall of a pipe for heating the fluid within the pipe. There are no rules-of-thumb available about designing such a system to achieve good uniformity of the temperature profile at the pipe inner surface beforehand. Non-uniformity can cause preferential fouling at hotter spots. This study focuses on the axial uniformity of heating along a pipe inside which the heated fluid if flowing. The situation has been simplified a great deal in mathematical terms from the corresponding conventional conjugate problem considered previously due to the small temperature rise in the fluid flow through one section of the pipe which is heated by one band heater. Similarity parameter sets have been deduced and verified by numerical simulations. The worst scenario of non-uniformity for such short band heaters, that is when L/Di=1.5, is presented in this paper. This may be used for designing a system to minimize the non-uniformity in terms of choosing the right pipe material, percentage of heater wire coverage in the band heater, etc. Copyright © 2002 John Wiley & Sons, Ltd. [source] Eigenvalue analysis of temperature distribution in composite wallsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2001Galip Oturanç Abstract The transient heat conduction problem in two-layer composite wall is solved analytically using spectral analysis. Eigenvalues and corresponding eigenfunctions of the spectral problem for the temperature distribution in composite walls are analysed using the Rouche Theorem. The number of eigenvalues is obtained and the temperature distribution of this complicated problem is given by a formula with calculated eigenvalues. The analytical solution obtained is in explicit form and provides easy determination of temperature rise in heating and thawing applications of composite materials. Copyright © 2001 John Wiley & Sons, Ltd. [source] Eclogites from the Chinese continental scientific drilling borehole, their petrology and different P-T evolutionsISLAND ARC, Issue 4 2007Yong-Feng Zhu Abstract Four phengite-bearing eclogites, taken from different depths of the Chinese continental scientific drilling (CCSD) borehole in the Sulu ultrahigh pressure terrane, eastern China, were studied with the electron microprobe. The compositional zonations of garnet and omphacite are moderate, whereas phengite compositions generally vary significantly in a single sample from core to rim by decrease of the Si content. Various geothermobarometric methods were applied to constrain the P-T conditions of these eclogites on the basis of the compositional variability of the above minerals. The constrained P-T path for sample B218 is characterized by pressure decrease from ca 3.0 GPa (ca 600°C) to 1.3 GPa (ca 550°C). Eclogite B310 yielded P-T conditions of 3.0 GPa and 750°C. The path for eclogite B1008 starts at about 650°C and 3.6,3.9 GPa (stage I) followed by a pressure decrease to 2.8,3.0 GPa and a significant temperature rise (stages II and IIIa, 750,810°C). Afterwards, this rock cooled down to 620,660°C at still high pressures (2.5,2.7 GPa, stage IIIb). Retrograde conditions were about 670°C and 1.3 GPa (stage IV). Eclogite B1039 yielded a P-T path starting at ca 600°C and 3.3,3.9 GPa (stage I). A pressure decrease to about 3.0 GPa (stage II, 590,610°C) and then a moderate isobaric temperature increase to ca 630°C (stage III) followed. Stage IV is characterized by temperatures of 650°C at pressures close to 1.3 GPa. During and after this stage (hydrous) fluids partially rich in potassium penetrated the rocks causing minor changes. Relatively high oxygen fugacities led to andradite and magnetite among the newly formed minerals. We think that the above findings can be best explained by mass flow in a subduction channel. Thus, we conclude that the assembly of UHP rocks of the CCSD site, eclogites, quartzofeldspathic rocks, and peridotites, cannot represent a crustal section that was already coherent at UHP conditions as it is the common belief currently. The coherency was attained after significant exhumation of these UHP rocks. [source] Cohesive-driven particle circulation in the solids conveying zone of a single-screw extruderADVANCES IN POLYMER TECHNOLOGY, Issue 2 2008Michael R. Thompson Abstract Aspects of heat transfer within the solids conveying zone of a single-screw extruder were studied by using a specially constructed drum testing apparatus. Experiments were conducted with linear low-density polyethylene, polystyrene (PS), and polypropylene (PP) samples by examining their transient temperature profile while the heated drum was stationary or moving. In accordance with classic solids conveying theory, the granular beds of PP and PS remained as plugs while the drum rotated. In such cases, the dominant modes of heat transfer for these systems are conduction through the contact area of a particle and conduction through the interstitial gas. An exception to this behavior was found with PE, in which the bed temperature increased more rapidly while the drum rotated. Visual observations of the bed showed that the particles circulated in the presence of shear and that this complex flow pattern increased in velocity as the drum temperature approached the onset temperature for melting the PE material. With strong correlation between the rate of circulation and the temperature rise in the bed, the movement of particles was assumed to act in a convective heat transfer mode bringing about more uniform heating of the polymer. The circulation phenomenon was attributed to dominant adhesive forces at the particle,drum interface overcoming the cohesive strength of the bulk. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:74,88, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20121 [source] Pain and Anatomical Locations of Radiofrequency Ablation as Predictors of Esophageal Temperature Rise During Pulmonary Vein IsolationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2008ARASH ARYANA M.D. Introduction: Esophageal temperature rise (ETR) during ablation inside left atrium has been reported as a marker for esophageal thermal injury. We sought to investigate the possible relationships between chest pain and ETR during radiofrequency (RF) ablation, and ETR and locations of RF application, in patients undergoing pulmonary vein (PV) isolation under moderate sedation. Methods and Results: We analyzed anatomical locations of each RF application and its association with esophageal temperature and presence/absence of pain. Data from 40 consecutive patients (mean age: 56 ± 10 years) were analyzed. There were a total of 4,071 RF applications resulting in 291 episodes of pain (7.1%) and 223 ETRs (5.5%). Thirty-five patients (87.5%) experienced at least one pain episode and 32 (80.0%) had at least one ETR. While 77.4% of posterior wall applications that caused pain also corresponded to an ETR (P < 0.0001), only 0.8% of pain-free posterior wall applications were associated with ETRs (P < 0.0001). The sensitivity and specificity of pain during ablation for ETR were 94% and 98%, respectively. No ETRs were observed during anterior wall applications. ETRs occurred more frequently during ablation on the left (86.1%) versus the right (13.9%), and in inferior (70.4%) versus superior (29.6%) segments. Conclusion: In patients undergoing PV isolation, ETR was encountered when ablating in the posterior left atrium with the distribution left > right and inferior > superior. Pain during ablation was associated with ETR, and lack of pain was strongly associated with absence of ETR. Pain during RF ablation may thus serve as a predictor of esophageal heating and potential injury. [source] Esophageal Temperature During Radiofrequency-Catheter Ablation of Left Atrium: A Three-Dimensional Computer Modeling StudyJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2006FERNANDO HORNERO M.D., Ph.D. Introduction: There is current interest in finding a way to minimize thermal injury in the esophagus during radiofrequency-catheter ablation of the left atrium. Despite the fact that the esophageal temperature is now being monitored during ablation, the influence of different anatomic and technical factors on the temperature rise remains unknown. Methods and Results: We implemented a three-dimensional computational model that included atrial tissue, epicardial fat, esophagus, aorta, and lung, all linked by connective tissue. The finite-element method was used to calculate the esophageal temperature distribution during a procedure of constant-temperature ablation with an 8-mm electrode, under different tissue conditions. Results showed that the distance between electrode and esophagus was the most important anatomic factor in predicting the esophageal temperature rise, the composition of the different tissues being of lesser importance. The measurement of the esophageal temperature in different sites of the lumen offered differences up to 3.7°C, especially for a short electrode,esophagus distance (5 mm). The difference in the convective cooling by circulating blood around electrode and endocardium did not show a significant influence on the esophageal temperature rise. Conclusion: Computer results suggest that (1) the electrode,esophagus distance is the most important anatomic factor; (2) the incorrect positioning of an esophageal temperature probe could give a low reading for the maximum temperature reached in the esophagus; and (3) the different cooling effect of the circulating blood flow at different atrial sites has little impact on the esophageal temperature rise. [source] NONCONTACT TEMPERATURE MONITORING OF A PELLETING PROCESS USING INFRARED THERMOGRAPHYJOURNAL OF FOOD PROCESS ENGINEERING, Issue 1 2007C. SALAS-BRINGAS ABSTRACT Contact methods are commonly used to determine temperature during food and feed manufacturing processes. This may, however, result in incorrect temperature measurements, because many food and feed materials easily agglomerate around the thermowell tip of the sensors, decreasing their time response; also, it is difficult to measure temperature from moving objects using contact methods. This article assesses the use of thermography to measure temperature throughout the manufacture of poultry feed. The experiment showed that precaution should be used when the temperature difference, between the meal at the outlet of the conditioner and pellets at the outlet of the pellet press, is associated with the temperature rise across the die. Precaution should also be used when the temperature of the pellets at the outlet of the pellet press is used as the peak temperature during the process. Temperature measurements through infrared emissions require improved instrument design to operate in a dusty, damp, steamy and oily environment. [source] Comparative Study of Thermal Inactivation of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes in Ground PorkJOURNAL OF FOOD SCIENCE, Issue 4 2004R. Y. Murphy ABSTRACT: Thermal inactivation of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes in ground pork was compared. The D (decimal reduction time at a certain heating temperature) values of E. coli O157:H7, Salmonella, and L. monocytogenes at 55 to 70°C were 33.44 to 0.048 min, 45.87 to 0.083 min, and 47.17 to 0.085 min, respectively. The z (temperature rise for 1 log10 reduction of D) value of E. coli O157:H7, Salmonella, and L. monocytogenes in ground pork was 4.94°C, 5.89°C, and 5.92°C, respectively. Significant difference was found on the D and z values between E. coli O157:H7 and Salmonella or between E. coli O157:H7 and L. monocytogenes. The D and z values of Salmonella in ground pork were not significantly different from L. monocytogenes. [source] Degree of conversion and temperature rise during polymerization of composite resin samples with blue diodesJOURNAL OF ORAL REHABILITATION, Issue 6 2001A. Kne To ensure an adequate clinical composite filling light source for photopolymerization is of great importance. In everyday clinical conditions commonly used unit for polymerization of composite material is halogen curing unit. The development of new blue superbright light emitting diodes (LED) of 470 nm wavelengths comes as an alternative to standard halogen curing unit of 450,470 nm wavelengths. The purpose of this study was to compare the degree of conversion (DC) and temperature rise of four hybrid composite materials: Tetric Ceram, Pertac II, Valux Plus and Degufill Mineral during 40 s illulmination with standard halogen curing unit Heliolux GTE of 600 mW cm,2 intensity, Elipar Highlight soft-start curing unit of 100 mW cm,2 (10 s) and 700 mW cm,2 (30 s) intensity and 16 blue superbright LED of minimal intensity of 12 mW cm,2 on the surface and 1 mm depth. The results revealed only a little bit higher DC values in case of polymerization with even 66 times stronger halogen curing units which showed twice higher temperature than blue diodes. Temperature and DC obtained are higher on the surface than on 1 mm depth regardless on the light source used. [source] Michael Polanyi and the discovery of co-catalysis: Discussion of an autobiographical letter from Michael Polanyi, FRS to Peter H. Plesch of 17 December 1963JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2004P. H. Plesch Abstract The origin of this memoir was a letter from Michael Polanyi (M. P.) to the present writer (P. H. P.) about their researches in the mid-1940s into the mechanism of what are now called cationic polymerizations, at the University of Manchester (England). M. P. analyzes his tactics and the mistakes made in directing this research. When the Manchester-trained researchers made little progress with what was a very recalcitrant problem, M. P. thinking that scientists from a different background might be more sucessful, got P. H. P., from Cambridge, to work with an Oxford-trained chemist. They recognized that the likely cause of the irreproducibility of these polymerizations was the apparatus used which permitted access of atmospheric moisture to the reaction mixtures containing the moisture-sensitive catalytic metal halides. Because the only method for following the very fast polymerizations was by monitoring the accompanying temperature rise, and the reactions had to be done below ambient temperature, the reaction vessel needed to be adiabatic, that is a Dewar (Thermos) flask; hence the problem of how to cool its contents. The solution was P. H. P.'s invention of the pseudo-Dewar vessel, the Dewar space of which, instead of being evacuated permanently, could be filled with air or evacuated. This device permitted the reaction mixture to be made up and cooled, and the reactions to be started without contact with the atmosphere. Thus it was found that isobutene polymerizations, which had stopped unaccountably, could be restarted by water vapor. P. H. P. termed water a "co-catalyst". The consequent "Manchester" theory recognized the monohydrate of TiCl4 as a protonic acid and saw the initiation as due to the protonation of the monomer, with the formation of a tert -carbenium ion, and these ions, formed repetitively, became the propagating species. The Manchester theory was rapidly accepted because it could also explain observations on other related reactions. The involvement of ions established a link with non-aqueous electrochemistry. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1537,1546, 2004 [source] Local Heating from Silver Nanoparticles and Its Effect on the Er3+ Upconversion in Oxyfluoride GlassesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010Chao Liu The effect of silver (Ag) nanoparticles on the upconversion emission properties of Er3+ ions in oxyfluoride glasses was investigated, and a mechanism of the energy transfer proposed. The integrated intensity ratios between 522 and 545 nm emission bands of Er3+ ions in glasses containing Ag nanoparticles were strongly dependent on the size of the Ag nanoparticles as well as on the intensity of the 800 nm excitation laser. When the absorption of Ag nanoparticles overlapped with the 2H11/2 and 4S3/2 energy levels in Er3+ ions, a strong energy transfer occurred from Er3+: 2H11/2, 4S3/2 levels to Ag nanoparticles. This energy was then converted to a temperature rise in the vicinity of Er3+ ions, eventually leading to the large increase in the integrated intensity ratios. The estimated effective temperature was approximately 200 K higher than the experimental temperature when the excitation power was 700 mW. [source] Pulpal effects of enamel ablation with a microsecond pulsed ,,=,9.3-µm CO2 laserLASERS IN SURGERY AND MEDICINE, Issue 4 2009Michal Staninec DDS Abstract Background and Objectives In vitro studies have shown that CO2 lasers operating at the highly absorbed 9.3 and 9.6-µm wavelengths with a pulse duration in the range of 10,20-microsecond are well suited for the efficient ablation of enamel and dentin with minimal peripheral thermal damage. Even though these CO2 lasers are highly promising, they have yet to receive FDA approval. Clinical studies are necessary to determine if excessive heat deposition in the tooth may have any detrimental pulpal effects, particularly at higher ablative fluencies. The purpose of this study was to evaluate the pulpal safety of laser irradiation of tooth occlusal surfaces under the conditions required for small conservative preparations confined to enamel. Study Design/Materials and Methods Test subjects requiring removal of third molar teeth were recruited and teeth scheduled for extraction were irradiated using a pulsed CO2 laser at a wavelength of 9.3 µm operating at 25 or 50 Hz using a incident fluence of 20 J/cm2 for a total of 3,000 laser pulses (36 J) for both rates with water cooling. Two control groups were used, one with no treatment and one with a small cut made with a conventional high-speed hand-piece. No anesthetic was used for any of the procedures and tooth vitality was evaluated prior to treatment by heat, cold and electrical testing. Short term effects were observed on teeth extracted within 72 hours after treatment and long term effects were observed on teeth extracted 90 days after treatment. The pulps of the teeth were fixed with formalin immediately after extraction and subjected to histological examination. Additionally, micro-thermocouple measurements were used to estimate the potential temperature rise in the pulp chamber of extracted teeth employing the same irradiation conditions used in vivo. Results Pulpal thermocouple measurements showed the internal temperature rise in the tooth was within safe limits, 3.3±1.4°C without water cooling versus 1.7±1.6°C with water-cooling, n,=,25, P<0.05. None of the control or treatment groups showed any deleterious effects on pulpal tissues and none of the 29 test-subjects felt pain or discomfort after the procedure. Only two test-subjects felt discomfort from "cold sensitivity" during the procedure caused by the water-spray. Conclusion It appears that this CO2 laser can ablate enamel safely without harming the pulp under the rate of energy deposition employed in this study. Lasers Surg. Med. 41:256,263, 2009. © 2009 Wiley-Liss, Inc. [source]
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