Temperature Standard Deviation Research Articles

Fluid filling of the digestive tract for improved proton resonance frequency shift-based MR thermometry in the pancreas.

To demonstrate that fluid filling of the digestive tract improves the performance of respiratory motion-compensated proton resonance frequency shift (PRFS)-based magnetic resonance (MR) thermometry in the pancreas. In seven volunteers (without heating), we evaluated PRFS thermometry in the pancreas with and without filling of the surrounding digestive tract. All data acquisition was performed at 1.5T, then all datasets were analyzed and compared with three different PRFS respiratory motion-compensated thermometry methods: gating, multibaseline, and referenceless. The temperature precision of the different methods was evaluated by assessing temperature standard deviation over time, while a simulation experiment was used to study the accuracy of the methods. Without fluid intake, errors in temperature precision in the pancreas up to 10°C were observed for all evaluated methods. After liquid intake, temperature precision improved to median values between 1.8 and 2.9°C. The simulations showed that gating had the lowest accuracy, with errors up to 7°C. Multibaseline and referenceless thermometry performed better, with a median error in the pancreas between -3 and +3°C after fluid intake, for all volunteers. Preparation of the digestive tract near the pancreas by filling it with fluid improved MR thermometry precision and accuracy for all common respiratory motion-compensated methods evaluated. These improvements are attributed to reducing field inhomogeneity in the pancreas. 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:692-701.

Smoothing effect of the thermal interface material on the temperature distribution in a stepwise varying width microchannel cooling device

The impact of the thermal interface material (TIM) layer on the performance of a stepwise varying width microchannel cooling device is analysed. A numerical model shows that the TIM layer, besides its well known negative impact on the temperature, also generates a smoothing effect on the temperature distribution. In this study, an analytical model is used to define a nondimensional parameter, called Smoothing Resistance ratio, as the quotient between the origin of the temperature non uniformities and the TIM thermal resistance that flatten the temperature distribution. The relationship between the temperature uniformity of the cooled device, expressed through the temperature standard deviation, and the Smoothing Resistance ratio is shown to be linear. These results lead to the definition of a new design procedure for this kind of cooling device, which aims to reduce the Smoothing Resistance ratio. Two solutions are identified and their drawbacks are analysed.

The relative effect of particles and turbulence on acoustic scattering from deep sea hydrothermal vent plumes revisited.

The relative importance of suspended particles and turbulence as backscattering mechanisms within a hydrothermal plume located on the Endeavour Segment of the Juan de Fuca Ridge is determined by comparing acoustic backscatter measured by the Cabled Observatory Vent Imaging Sonar (COVIS) with model calculations based on in situ samples of particles suspended within the plume. Analysis of plume samples yields estimates of the mass concentration and size distribution of particles, which are used to quantify their contribution to acoustic backscatter. The result shows negligible effects of plume particles on acoustic backscatter within the initial 10-m rise of the plume. This suggests turbulence-induced temperature fluctuations are the dominant backscattering mechanism within lower levels of the plume. Furthermore, inversion of the observed acoustic backscatter for the standard deviation of temperature within the plume yields a reasonable match with the in situ temperature measurements made by a conductivity-temperature-depth instrument. This finding shows that turbulence-induced temperature fluctuations are the dominant backscattering mechanism and demonstrates the potential of using acoustic backscatter as a remote-sensing tool to measure the temperature variability within a hydrothermal plume.

Dual-echo Z-shimmed proton resonance frequency-shift magnetic resonance thermometry near metallic ablation probes: Technique and temperature precision.

To improve the precision of proton resonance frequency-shift magnetic resonance thermometry near ablation probes by recovering near-probe image signals that are typically lost due to magnetic susceptibility-induced field distortions. A dual-echo gradient-recalled echo sequence was implemented, in which the first echo was under- or over-refocused in the slice dimension to recover image signal and temperature precision near a probe, and the second echo was fully refocused to obtain image signal everywhere else in the slice. A penalized maximum likelihood algorithm was implemented to estimate a single temperature map from both echoes. Agar phantom and ex vivo experiments with and without microwave heating at 3 T evaluated how much temperature precision was improved near a microwave ablator compared to a conventional single-echo scan as a function of slice and needle orientation in the magnet. The number of near-probe voxels with temperature standard deviation σ>1°C was decreased by 51% in the phantom experiment, averaged across orientations, and by 31% in the pork. Temperature maps near the probe were more smoother and more complete in all orientations. Dual-echo z-shimmed temperature imaging can recover image signal for more precise temperature mapping near metallic ablation probes. Magn Reson Med 78:2299-2306, 2017. © 2017 International Society for Magnetic Resonance in Medicine.

Real-time monitoring of tissue displacement and temperature changes during MR-guided high intensity focused ultrasound.

The therapy endpoint most commonly used in MR-guided high intensity focused ultrasound is the thermal dose. Although namely correlated with nonviable tissue, it does not account for changes in mechanical properties of tissue during ablation. This study presents a new acquisition sequence for multislice, subsecond and simultaneous imaging of tissue temperature and displacement during ablation. A single-shot echo planar imaging sequence was implemented using a pair of motion-encoding gradients, with alternated polarities. A first ultrasound pulse was synchronized on the second lobe of the motion-encoding gradients and followed by continuous sonication to induce a local temperature increase in ex vivo muscle and in vivo on pig liver. Lastly, the method was evaluated in the brain of two volunteers to assess method's precision. For thermal doses higher than the lethal threshold, displacement amplitude was reduced by 21% and 28% at the focal point in muscle and liver, respectively. Displacement value remained nearly constant for nonlethal thermal doses values. The mean standard deviation of temperature and displacement in the brain of volunteers remained below 0.8 °C and 2.5 µm. This new fast imaging sequence provides real-time measurement of temperature distribution and displacement at the focus during HIFU ablation. Magn Reson Med 78:1911-1921, 2017. © 2017 International Society for Magnetic Resonance in Medicine.

Assessment of the Thermal Performance of Building Integrated Vegetation System through Small Scale Model

This study presents method for evaluating the performance of thermal condition in building with BIVS (Building Integrated Vegetation System) using small scale model. The building model, which has the volume of 1m (W)×1m (D)×1m (H) and the wall-thickness of 0.1m, was used for field test. Experimental Site is located in Suwon, Korea. Thermal sensors are installed at and inside each layers of BIVS and building structures. The datum of temperature and relative humidity is recorded by connecting to data logger. Sedum middendorffianum and Liriope platyphylla are used for experimental plants. It takes two weeks for experiment in sunny summer. The mean and standard deviation of temperature and relative humidity in ambient air, one room in building that installed BIVS and the other in control building are 26.9±4.1°C and 79.9±16.9%, 24.8±1.5°C and 92.2±0.7%, 24.8±2.1°C and 91.1±1.8% respectively. BIVS can decrease indoor temperature to almost 3°C in similar relative humidity condition. The thermal insulation property of BIVS planted the Sedum middendorffianum is better than that of Liriope platyphylla.

Investigation of phase change material based battery thermal management at cold temperature using lattice Boltzmann method

The power and energy densities of battery will decrease at cold temperature and the heat preservation is necessary to keep the working temperature. In this paper, the lattice Boltzmann model for phase change material based battery thermal management cold temperature is constructed and the effects of thermal conductivity, latent heat and environmental temperature have been considered. The results show that with the latent heat of phase change material (PCM), the temperature of battery decreases slowly and the temperature distribution can be guaranteed. However, once the PCM adjacent to the interface of battery and PCM, the temperature of battery drops faster and the temperature standard deviation rises sharply. Besides, the lower thermal conductivity, greater latent heat and higher environmental temperature are able to slow down the solidification process of PCM and keeps the temperature of battery. However, with larger latent heat of PCM, the battery temperature distribution gets more non-uniform, which is able to decrease the cycle life of battery.

Controls on Arctic glacier-fed river water temperature

ABSTRACTThe impact of climate change on Arctic rivers is expected to be severe. There is therefore a need for greater understanding of Arctic river temperature processes. This study quantifies the spatio-temporal variability of water temperatures in the Kårsa River, Sweden. Water temperature was monitored over two summers within the main proglacial channel and within braids fed by different sources. Longitudinal and lateral temperature patterns were assessed in relation to prevailing hydro-meteorology. Temperature metrics in the main channel increased with distance downstream but were moderated by a large lake, while temperatures in the braids were dependent upon channel source. The high temperature standard deviation and inter-site differences within the braids highlight the importance of braided channels for creating thermal habitat heterogeneity. Temperatures were dependent on hydro-meteorological conditions, with sensitivity to air temperature maximized during cooler, rainy conditions. These results shed new light on Arctic river temperature patterns and their controlling processes.

Feasibility of real-time MR thermal dose mapping for predicting radiofrequency ablation outcome in the myocardium in vivo

BackgroundClinical treatment of cardiac arrhythmia by radiofrequency ablation (RFA) currently lacks quantitative and precise visualization of lesion formation in the myocardium during the procedure. This study aims at evaluating thermal dose (TD) imaging obtained from real-time magnetic resonance (MR) thermometry on the heart as a relevant indicator of the thermal lesion extent.MethodsMR temperature mapping based on the Proton Resonance Frequency Shift (PRFS) method was performed at 1.5 T on the heart, with 4 to 5 slices acquired per heartbeat. Respiratory motion was compensated using navigator-based slice tracking. Residual in-plane motion and related magnetic susceptibility artifacts were corrected online. The standard deviation of temperature was measured on healthy volunteers (N = 5) in both ventricles. On animals, the MR-compatible catheter was positioned and visualized in the left ventricle (LV) using a bSSFP pulse sequence with active catheter tracking. Twelve MR-guided RFA were performed on three sheep in vivo at various locations in left ventricle (LV). The dimensions of the thermal lesions measured on thermal dose images, on 3D T1-weighted (T1-w) images acquired immediately after the ablation and at gross pathology were correlated.ResultsMR thermometry uncertainty was 1.5 °C on average over more than 96% of the pixels covering the left and right ventricles, on each volunteer. On animals, catheter repositioning in the LV with active slice tracking was successfully performed and each ablation could be monitored in real-time by MR thermometry and thermal dosimetry. Thermal lesion dimensions on TD maps were found to be highly correlated with those observed on post-ablation T1-w images (R = 0.87) that also correlated (R = 0.89) with measurements at gross pathology.ConclusionsQuantitative TD mapping from real-time rapid CMR thermometry during catheter-based RFA is feasible. It provides a direct assessment of the lesion extent in the myocardium with precision in the range of one millimeter. Real-time MR thermometry and thermal dosimetry may improve safety and efficacy of the RFA procedure by offering a reliable indicator of therapy outcome during the procedure.

Monitoring and Material Simulation of Automatic-Cooling System for Waterfowl Incubator

In order to reduce the required manpower and biosecurity control risk for waterfowl breeding eggs, this study developed waterfowl automatic eggs cooling incubator which using the concept of pre-heating and pre-wetting type front control thermal system and add the automatic watering eggs cooling system, trolley egg rack, pneumatic eggs overturning system and monitoring system. The front control thermal system preheats and pre-wet the air to the required environment for hatching and import into incubator for the hatching test. The test results show that the hatching environment uniformity of automatic eggs cooling incubator developed by this study is better than the traditional incubator’s environment. The monitoring system can stable control the variation for three hatching parameters of temperature, humidity and carbon dioxide concentration. Besides the combination of automatic watering eggs cooling system for hatching process can significantly reduce the required manpower for watering eggs cooling and biosecurity control risk, the average hatching ratio is 82.06% that can satisfy the requirement of general professional goose breeding eggs incubator. The test using computational fluid dynamics simulation software (CFD) to simulate the variable turbulent wind speed. On the premise of using temperature as the respondence to conduct the optimization design of response surface methodology. The results shows that the incubator temperature standard deviation decreased from 0.26°C to 0.14°C when three turbulent wind speed changed from 4.25 m/s, 3.50 m/s and 4.63 m/s to 2 .00m/s, 5 .00m/s and 3.81 m/s. There is a further increase for the uniformity of the temperature field.

A Characterization of the Quality of the Stratospheric Temperature Distributions from SABER based on Comparisons with COSMIC Data

AbstractGlobal stratospheric temperature measurement is an important field in the study of climate and weather. Dynamic and radiative coupling between the stratosphere and troposphere has been demonstrated in a number of studies over the past decade or so. However, studies of the stratosphere were hampered by a shortage of observation data before satellite technology was used in atmospheric sounding. Now, the data from the Thermosphere, Ionosphere, Mesosphere Energetics, and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry (TIMED/SABER) observations make it easier to study the stratosphere. The precision and accuracy of TIMED/SABER satellite soundings in the stratosphere are analyzed in this paper using refraction error data and temperature data obtained from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) radio occultation sounding system and TIMED/SABER temperature data between April 2006 and December 2009. The results show high detection accuracy of TIMED/SABER satellite soundings in the stratosphere. The temperature standard deviation (STDV) errors of SABER are mostly in the range from of 0–3.5 K. At 40 km the STDV error is usually less than 1 K, which means that TIMED/SABER temperature is close to the real atmospheric temperature at this height. The distributions of SABER STDV errors follow a seasonal variation: they are approximately similar in the months that belong to the same season. As the weather situation is complicated and fickle, the distribution of SABER STDV errors is most complex at the equator. The results in this paper are consistent with previous research and can provide further support for application of the SABER’s temperature data.

Effects of Process Parameters on Deformation and Temperature Uniformity of Forged Ti-6Al-4V Turbine Blade

This work is motivated by the frequent occurrence of macro- and microdefects within forged Ti-6Al-4V turbine blades due to the severely nonuniform strain and temperature distributions. To overcome the problem of nonuniformity during the blade forging operation, firstly, a 2D coupled thermo-mechanical finite element approach using the strain-compensated Arrhenius-type constitutive model is employed to simulate the real movements and processing conditions, and its reliability is verified experimentally. Secondly, two evaluation indexes, standard deviation of equivalent plastic strain and standard deviation of temperature, are proposed to evaluate the uniformity characteristics within the forged blade, and the effects of four process parameters including the forging velocity, friction factor, initial workpiece temperature and dwell time on the uniformity of strain and temperature distributions are carefully studied. Finally, the numerically optimized combination of process parameters is validated by the application in a practical process. The parametric study reveals that a reasonable combination of process parameters considering the flow resistance, flow localization and the effects of deformation and friction heating is crucial for the titanium alloy blade forging with uniformity. This work can provide a significant guidance for the design and optimization of blade forging processes.

Uniformity analysis of temperature distribution in an industrial MOCVD reactor

Three‐dimensional models, coupling fluid flow and heat transfer, have been adopted to analyze influences of the process parameters on the temperature uniformity in an industrial MOCVD reactor. Important factors, such as the inlet gas flow, the susceptor rotation, the heater power, the distance between the heat shield and the susceptor (d1), as well as the distance between the heater and the susceptor (d2), have been investigated carefully. The system heating condition is characterized by temperature uniformity denoted as the standard deviation of temperature, and by thermal efficiency expressed as a combination parameter of the dissipated energy. The results reveal that decrease of the gas flow and the rotation rate, as well as increase of the distance d1, could monotonically enhance the temperature uniformity. The results also show that decrease of the above three parameters could improve the thermal efficiency. Furthermore, increase of the distance d2 enhances the temperature uniformity, and reduces the thermal efficiency slightly. The influences of the parameters on the uniformity vary at the different locations of the susceptor as divided into Zone A, Zone B and Zone C. The conclusions help the growth engineer optimize the system design and process conditions of the reactor.

Estimating maize water stress by standard deviation of canopy temperature in thermal imagery

A new crop water stress indicator, standard deviation of canopy temperature within a thermal image (CTSD), was developed to monitor crop water status. In this study, thermal imagery was taken from maize (Zea mays L.) under various levels of deficit irrigation at different crop growing stages. The Expectation-Maximization algorithm was used to estimate the canopy temperature distribution from thermal imagery under a range of crop coverage and water stress conditions. Soil water deficit (SWD), leaf water potential (ψ), stomatal conductance, and other crop water stress indices were used to evaluate the CTSD. We found that the temperature differences between sunlit and shaded parts of the canopy would increase with larger canopy resistance in the sunlit part of the crop canopy. The CTSD well described impact of irrigation events (timing and depth) on crop water stress. All water stress measurements showed statistically significant relationship with CTSD. Although CTSD is not sensitive to small changes in water stress, the result suggests that the canopy temperature standard deviation could be used as a water stress indicator. This index has strong application potential because it only relies on the canopy temperature itself, and is easy to calculate. Moreover, it may also be applied to high resolution thermal imagery from other remote sensing platforms, such as unmanned aerial vehicles.

Partitioning scleractinian coral diversity across reef sites and regions in the Western Indian Ocean

AbstractUnderstanding how diversity is organized is essential for inference about appropriate scales for natural resource research and management. In this study, we investigated variation in scleractinian coral taxonomic richness and community diversity in the Western Indian Ocean (WIO) at different spatial scales. We sampled corals in 331 sites across nine countries. Sites were pooled into 11 distinct subregions based on previous investigations on coral community structure and between closures and reefs open to fishing for five regions with sufficient closure replication. We analyzed similarities in coral communities and compared differences in mean richness and Shannon diversity. Significant differences in alpha and beta components of diversity were tested at multiple spatial scales and between management types against a random distribution null model. Rarefaction was used to investigate significant difference in total taxonomic richness among regions. Coral communities were mainly structured along Acropora and massive Porites dominance lines. Highest dissimilarity among coral communities was found at the regional level and within‐ and between‐subregion variations accounted for most of the coral diversity. Beta components were responsible for higher proportions of taxonomic richness of which a large part was explained by the site‐region interaction. Alpha diversity contributed most to Shannon diversity and site level richness and Shannon diversity had similar relationships with latitude, peaking at about 10°S. Alpha diversity also showed significant relationship with water temperature variability, peaking at a sea surface temperature standard deviation of about 1.4 °C, corresponding to the same 10°S latitude. Relatively higher alpha and beta components contributed to high richness and Shannon diversity in three regions: southern Kenya–northern Tanzania, southern Tanzania–northern Mozambique and northwestern Madagascar–Mayotte. Consequently, the findings support the proposal for delineating these locations as a regional priority for biodiversity conservation.

Improved cardiac magnetic resonance thermometry and dosimetry for monitoring lesion formation during catheter ablation.

A new real-time MR-thermometry pipeline was developed to measure multiple temperature images per heartbeat with 1.6×1.6×3 mm3 spatial resolution. The method was evaluated on 10 healthy volunteers and during radiofrequency ablation (RFA) in sheep. Multislice, electrocardiogram-triggered, echo-planar imaging was combined with parallel imaging, under free breathing conditions. In-plane respiratory motion was corrected on magnitude images by an optical flow algorithm. Motion-related susceptibility artifacts were compensated on phase images by an algorithm based on Principal Component Analysis. Correction of phase drift and temporal filter were included in the pipeline implemented in the Gadgetron framework. Contact electrograms were recorded simultaneously with MR thermometry by an MR-compatible ablation catheter. The temporal standard deviation of temperature in the left ventricle remained below 2 °C on each volunteer. In sheep, focal heated regions near the catheter tip were observed on temperature images (maximal temperature increase of 38 °C) during RFA, with contact electrograms of acceptable quality. Thermal lesion dimensions at gross pathology were in agreement with those observed on thermal dose images. This fully automated MR thermometry pipeline (five images/heartbeat) provides direct assessment of lesion formation in the heart during catheter-based RFA, which may improve treatment of cardiac arrhythmia by ablation. Magn Reson Med 77:673-683, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Repeatability of infrared ocular thermography in assessing healthy and dry eyes.

To investigate the inter-image, inter-occasion and inter-examiner repeatability of NEC infrared thermo-tracer TH 9260 in assessing healthy and dry eyes. Ocular surface temperature (OST) was recorded using NEC infrared thermo-tracer TH 9260 on 21 healthy and 15 dry eyes. Data from the right eyes were analyzed. Marking of the ocular surface and OST acquisition was performed using a new 'diamond' demarcation method. Twelve OST indices were obtained at three different time points following a blink: 0s, 5s and 10s. Inter-image, inter-occasion and inter-examiner repeatability of the infrared ocular thermography was evaluated by calculating coefficients of repeatability (COR). Ten out of the twelve tested OST indices had good repeatability with small inter-image variability (%COR: 0.2-0.9), inter-occasion variability (%COR: 2.1-3.7) and inter-examiner variability (%COR: 1.5-3.7) for the three studied time points. Two of the OST indices (temperature standard deviation of the region of interest and radial temperature difference) had poor repeatability with much larger inter-image variability (%COR: 8.9-140.7), inter-occasion variability (%COR: 47.5-153.5) and inter-examiner variability (%COR: 54.7-142.0) for the three studied time points. Most of the metrics adopted in this assessment can be considered to be highly repeatable.

The Transient and Equilibrium Climate Response to Rapid Summertime Sea Ice Loss in CCSM4

Abstract The impact that disappearing Arctic sea ice will have on the atmospheric circulation and weather variability remains uncertain. In this study, results are presented from a sea ice perturbation experiment using the coupled Community Climate System Model, version 4 (CCSM4). By decreasing the albedo of the sea ice, the impact of an ice-free summertime Arctic on the coupled ocean–atmosphere system is isolated in an idealized but energetically self-consistent way. The multicentury equilibrium response is examined, as well as the transient response in an initial condition ensemble. The perturbation drives pronounced year-round sea ice thinning, Arctic warming, Arctic amplification, and moderate global warming. Even in the almost complete absence of summertime sea ice, the atmospheric general circulation response is very weak and the transient response is small compared to the internal variability. Surface temperature variability is reduced on all time scales over most of the middle and high latitudes with a 50% reduction in the standard deviation of temperature over the Arctic Ocean. The reduction is attributed to decreased temperature gradients and increased maritime influence once the sea ice melts. This reduced variability extends weakly into the variability of the midlatitude and free tropospheric geopotential height (less than 10% reduction in the standard deviation). Consistently, eddy geopotential height variability is found to decrease while geopotential isopleth meandering, which reflects Arctic amplified warming, increases moderately. The sign of these changes is consistent with recent observations, but the size of these changes is relatively small.

Similarity theory and nocturnal locally scaled turbulence variances in the tropical urban roughness sublayer

We assessed the potential of the “local” Monin–Obukhov similarity theory to predict the relationship between scaled turbulence standard deviations (σi; i = turbulence quantity) and atmospheric stability (ζ) in the nocturnal urban roughness sublayer using data collected in a tropical city of which data and research have been lacking as most works previously reported mainly concentrated on temperate mid-latitude regions. The site was LCZ 5B in the Local Climate Zone classification system with open midrise buildings with scattered trees. Unstable (convective) atmospheric conditions persisted through the night with infrequent and intermittent stable conditions. Nighttime turbulence statistics were lower than daytime turbulence statistics due to the weak (<1 m/s) and variable mean wind speeds. Using local scales, the Monin–Obukhov similarity theory failed to predict the trend in the standard deviation of vertical wind velocity (σw) scaled by local friction velocity (u*l) with local atmospheric stability (ζl) but the standard deviation of temperature (σT) scaled to the local friction temperature (T*l) fared better. However, we found that by using the local free convection velocity (uf, l) as the normalising scale with σW, the trend was better described with ζl using simple power law relations for both unstable and stable conditions, but this situation was limited to neutral conditions.

Safety Irradiation Parameters of Nd:YAP Laser Beam for Endodontic Treatments: An In Vitro Study.

Objective. Nd:YAP laser has several potentialities of clinical applications in endodontics. The aim of our study is to determine the safety range of irradiation parameters during endodontic application of Nd:YAP laser that can be used without damaging and overheating the periodontal tissue. Material and Methods. Twenty-seven caries-free single-rooted extracted human teeth were used. Crowns were sectioned to obtain 11 mm root canal length. Temperature increases at root surfaces were measured by a thermocouple during Nd:YAP laser irradiation of root canals at different energy densities. Canal irradiation was accomplished with a circular and retrograde movement from the apex until the cervical part of the canal during 10 seconds with an axial speed of 1 mm/s. Each irradiation was done in a canal irrigated continuously with 2.25% NaOCl solution. Results. Periodontal temperature increase depends on the value of energy density. Means and standard deviations of temperature increases at root surfaces were below 10°C (safe threshold level) when the average energy densities delivered per second were equal to or below 4981 J/cm2 and 9554 J/cm2, respectively, for irradiations using a fiber diameter of 320 μm and 200 μm. Conclusions. Within the limitations of this study and under specific irradiation conditions, Nd:YAP laser beam may be considered harmless for periodontal tissues during endodontic applications.