Changes In Thermal Profiles Research Articles

Thermal cycling effects on the local microstructure and mechanical properties in wire-based directed energy deposition of nickel-based superalloy

In additive manufacturing, intrinsic heat treatments take place during deposition that affect the properties of AM-structures. In this work, the influence of thermal cycling on the local microstructure and mechanical properties of nickel-based superalloy in wire-based electron beam directed energy deposition (EB-DED) was investigated. Structures were fabricated using a continuous deposition strategy (CDS) and discontinuous interpass cooling strategy (ICS) revealing changes in thermal profiles, time-temperature history, and microstructure. An altered morphology along the build-up height and interdendritic zones enriched in Nb are formed. Nb and Mo did not show a clear trend of segregation along the build-up height. Lower fractions of the Laves phase and MCs are found for both configurations. Differences between deposition strategies and locations within AM-structures are found for the γ" and δ phase. The higher Nb content in the interdendritic zone promotes the precipitation of γ" and δ phase by shortening the aging times compared to wrought materials. The longer deposition times of ICS favour the precipitation of fine γ" in the interdendritic zone throughout the deposition height. In contrast, the short deposition time of CDS leads to an increase in temperature and a heterogeneous distribution of γ" along the height, i.e. coarsening of the γ" followed by a dissolution along the built-up height. The microstructural changes correlate with the mechanical properties. Structures fabricated with ICS exhibit homogeneous mechanical properties throughout, while the graded microstructure of CDS results in graded mechanical properties and decreasing strength throughout.

The Effects of Methane Clathrates on the Thermal and Seismic Profile of Titan's Icy Lithosphere

We investigate the effects of methane clathrates on Titan’s thermal and seismic structure. The Dragonfly mission is planned to arrive at Titan in 2033 with a payload that includes a seismic package. The seismic instruments are tasked with recording seismic events and recovering the internal structure. Here, we explore whether differences in thermal and seismic profiles between a pure water ice shell and an ice shell with a clathrate lid could be detectable with seismic instrumentation. Due to their lower thermal conductivity, clathrates reduce the conductive lid thickness thus altering the thermal profile. The differences between seismic velocities of clathrates and pure water ice, coupled with changes in the thermal profile, indicate the clathrate lid will create lower seismic velocities, particularly for the upper 10 km of the surface ice shell. The differences in P and S velocity at the surface are 2.9% and 4.5%, respectively, and reach up to 8.4% (for both P and S) at a depth of 9.6 km. Due to changes in thermal profile, the seismic attenuation of the ice shell will change such that clathrates will suppress surface wave amplitudes relative to the pure water ice model. The clathrate lid will further create minor changes (≤2.0%) in the surface wave dispersion curves. Dragonfly, or other future seismic investigations, could provide evidence for or against the presence of a clathrate lid by constraining the thermal and seismic profile of Titan’s ice shell, by measuring the relative amplitudes of the surface to body waves, or by constraining the surface wave dispersion with high accuracy and precision.

Computational Analysis of Structural Defects in Silica Aerogels

AbstractTechnological advances in synthesis and preparation of aerogels have resulted in formulations that have the mechanical integrity (while retaining flexibility) to be utilized in a broad range of applications and have overcome the initial brittleness that this class of materials was once known for. Both structural and functional aerogels show a drop in performance when subjected to certain cyclic thermal or impact loading due to the wear and formation of cracks, which reduces their lifespan. Here we present the proof-of-concept of a computational toolset that connects the change in thermal profile to structural failure and degradation. In combination with an appropriate finite element (FEM) solver, we have developed a genetic algorithm that can reconstruct the size and shape of the defective region in silica aerogels given the temperatures from a sensor grid. Results show that a heatmap can be used as the foundation for reconstructing faults and defects in thermally insulating materials. Furthermore, the model developed in this study can be expanded to accommodate other material types. Experimental setup can used to benchmark and refine the computational toolset.

Disturbances of Temperature-Depth Profiles by Surface Warming and Groundwater Flow Convection in Kumamoto Plain, Japan

Subsurface temperatures depend on climate and groundwater flow. A lack of observations of subsurface temperature collected over decades limits interpretation of the combined influences of surface warming and groundwater flow on subsurface thermal regimes. Subsurface temperature-depth profile data acquired for Kumamoto Plain, Japan, between 1987 and 2012 were collected and analyzed to elucidate regional groundwater and heat flows. The observed and simulated temperature-depth profiles showed the following: subsurface water flows from northeast to southwest in the study area; the combined influence of surface warming and water flow perturbation produces different temporal changes in thermal profiles in recharge, intermediate, and discharge areas; and aquifer thermal properties contribute more than hydraulic parameters to the perturbation of temperature-depth profiles. Spatial and temporal evolution features of subsurface thermal regimes may be utilized to investigate the influence of surface warming events on subsurface water and heat flows at the basin scale.

Effects of Wind Mixing in a Stratified Water Column on Toxic Cyanobacteria and Microcystin-LR Distribution in a Subtropical Reservoir.

We analyzed the effects of stratification changes due to wind on the vertical cyanobacteria distribution and microcystin-LR concentrations in a reservoir and assessed the implications for water management. Under stratified conditions, the highest microcystin concentrations (up to 4.16µg/L) and toxic cyanobacteria biovolume occurred in the epilimnion (~ 1m). The lowest microcystin concentrations were between 0.02 and 1.28µg/L and occurred in the hypolimnion (~ 20m). A cold front passage associated with high wind velocities induced water column mixing, promoting the redistribution of microcystin-LR and cyanobacteria throughout the water column and increasing their concentrations in deeper zones. Microcystin-LR concentration was positively correlated with cyanobacteria biovolume (r = 0.747) and chlorophyll a concentration (r = 0.798). Changes in thermal profile due to wind would imply a greater challenge for drinking water treatment plants, since high cyanobacterial and microcystin concentrations could reach deep-water intakes.

Detection of embryo mortality and hatch using thermal differences among incubated chicken eggs

Accurate diagnosis of both the stage of embryonic mortality and the hatch process in incubated eggs is a fundamental component in troubleshooting and hatchery management. However, traditional methods disturb incubation, destroy egg samples, risk contamination, are time and labour-intensive and require specialist knowledge and training. Therefore, a new method to accurately detect embryonic mortality and hatching time would be of significant interest for the poultry industry if it could be done quickly, cheaply and be fully integrated into the process. In this study we have continuously measured individual eggshell temperatures and the corresponding micro-environmental air temperatures throughout the 21 days of incubation using standard low-cost temperature sensors. Moreover, we have quantified the thermal interaction between eggs and air by calculating thermal profile changes (temperature drop time, drop length and drop magnitude) that allowed us to detect four categories of egg status (infertile/early death, middle death, late death and hatch) during incubation. A decision tree induction classification model accurately (93.3%) predicted the status of 105 sampled eggs in comparison to the classical hatch residue breakout analyses. With this study we have provided a major contribution to the optimisation of incubation processes by introducing an alternative method for the currently practiced hatch residue breakout analyses.

Heat tracing to examine seasonal groundwater flow beneath a low-gradient stream in rural central Illinois, USA

The thermal profile of a streambed is affected by a number of factors including: temperatures of stream water and groundwater, hydraulic conductivity, thermal conductivity, heat capacity of the streambed, and the geometry of hyporheic flow paths. Changes in these parameters over time cause changes in thermal profiles. In this study, temperature data were collected at depths of 30, 60, 90 and 150 cm at six streambed wells 5 m apart along the thalweg of Little Kickapoo Creek, in rural central Illinois, USA. This is a third-order low-gradient baseflow-fed stream. A positive temperature gradient with inflection at 90-cm depth was observed during the summer period. A negative temperature gradient with inflection at 30 cm was observed during the winter period, which suggests greater influence of stream-water temperatures in the substrate during the summer. Thermal models of the streambed were built using VS2DHI to simulate the thermal profiles observed in the field. Comparison of the parameters along with analysis of temperature envelopes and Peclet numbers suggested greater upwelling and stability in temperatures during the winter than during the summer. Upwelling was more pronounced in the downstream reach of the pool in the riffle and pool sequence.

Relationship between in vitro drug sensitivity and clinical response of patients to treatment in chronic lymphocytic leukemia.

To improve the efficacy of therapeutic options in chronic lymphocytic leukemia (CLL) an in vitro system to determine the response of mononuclear blood cells from blood of patients was elaborated. The study combines four approaches, i.e., cell viability, apoptosis rate, differential scanning calorimetry (DSC), and immunoblotting to develop personalized therapy protocols based on the cell sensitivity to drug exposure of individual CLL patients. The complementary analyses were performed on 28 peripheral blood samples from previously untreated CLL patients before therapy. The induction and progress of apoptosis in CLL cells exposed in vitro to purine analogs combined with mafosfamide, i.e., cladribine + mafosfamide (CM) and fludarabine + mafosfamide (FM) were assessed using the above approaches. The changes in thermal profiles (decrease/loss of transition at 95±5˚C) coincided with an accumulation of apoptotic cells, a decrease in the number of viable cells, and differences in the expression of the apoptosis‑related protein PARP‑1. No significant changes were observed in the thermal profiles of nuclei isolated from CLL cells resistant to the treatment. The complementary assays revealed a strong relationship between both the in vitro sensitivity of leukemia cells to drugs and the clinical response of the patients, determined usually after the sixth course of treatment (after ~6 months of therapy). As a summary of studies followed by complementary tests, our findings demonstrate the value of in vitro exposure of CLL cell samples to drugs intended to treat CLL patients, before their administration in order to recommend the most suitable and effective therapy for individual patients.

Toward personalized therapy for chronic lymphocytic leukemia

The differences in clinical course of chronic lymphocytic leukemia could have an impact on variations in a patient’s response to therapy. Our published results revealed that thermal transition (95 ± 5°C) in differential scanning calorimetry profiles appear to be characteristic for the advanced stage of CLL. Moreover, a decrease/loss of this transition in nuclei from leukemic cells exposed to drugs ex vivo could indicate their diverse efficacy. It seems that the lack of changes in thermal profile could predict patient’s drug resistance. In this study, we demonstrate the results obtained after drug treatment of leukemic cells by calorimetry, apoptosis-related parameters involved in expression of genes using cDNA microarray and western blot. These data were compared with the patients’ clinical parameters before and after RCC therapy (rituximab + cladribine + cyclophosphamide). The complementary analysis of studied cases with opposite clinical response (CR or NR) revealed a strong relationship between clinical data, differences in thermal scans and apoptosis-related gene expression. We quantified expression of eight of apoptosis-related 89 genes, i.e., NOXA, PUMA, APAF1, ESRRBL1, CASP3, BCL2, BCL2A1 and MCL1. Particular differences in NOXA and BCL2 expression were revealed. NOXA expression in cells of patients who achieved a complete response to RCC therapy was 0.44 times higher in comparison to control ones. Interestingly, in the case of patients who did not respond to immunotherapy, NOXA expression was highly downregulated (RQ = 4.39) as compared with untreated cells. These results were confirmed by distinct cell viability, protein expression as well as by differences in calorimetry profiles.

Changes in Temperature Profile, Texture and Color of Pork Loin Chop during Pan-frying

The aim of this work was to investigate changes in thermal profile, meat texture and color of pork chop during pan-frying with or without one turnover. Pork chops (1.2 cm thick) were individually pan-fried at 175 ºC for 75 s without turnover or 150 s with one turnover. Internal temperature, meat color and texture at 11 designated positions were tracked. During frying, temperature and cooking loss significantly increased (P<0.001), accompanied by a significant increase (P<0.001) in hardness, gumminess, chewiness and L* value, together with a significant decrease (P<0.05) in springiness, cohesiveness, resilience and a* value. Positions close to the periphery generally showed significantly higher (P<0.05) final temperatures, and significantly lower (P<0.05) hardness, gumminess, chewiness, L* and a* values than those close to the center. These results could explain variation in tenderness within the same sample when evaluating eating quality of cooked meat.

Usefulness of Differential Scanning Calorimetry for Monitoring Ex Vivo the Changes In Responses of CLL Cells to Anti-Cancer Drugs: Development of Personalized Therapy

AbstractAbstract 4635 Objective:Chronic lymphocytic leukemia (CLL) is the most frequent type of leukemia among elderly people in Europe and North America. CLL is considered as a cancer involving mainly deregulated apoptosis. A strong difference between patients in the disease progression, response to anti-cancer therapy, and outcome is a major challenge in elaboration of efficacious treatment. Therefore, it is important to develop personalized therapeutic protocols based on the individual patient's sensitivity to medication. The aim of our ex vivo studies was to monitor the changes in responses of leukemic cells to anti-cancer agent(s) and correlate results obtained by DSC and other supplementary techniques with patients clinical response. Methods:Leukemic cells were obtained from peripheral blood of 14 patients prior to the onset of CC (cladribine + cyclophosphamide) therapy. Primary tumour cell samples were exposed ex vivo to CM or FM, as well as to ROSC alone for 48 hrs. We monitored the induction and progress of apoptosis in CLL cells exposed ex vivo to purine analogs combined with mafosfamide i.e. CM (cladribine + mafosfamide), FM (fludarabine + mafosfamide), and additionally to R-roscovitine (ROSC), an inhibitor of cyclin-dependent kinases, by a few techniques, i.e. cell viability test, apoptosis assay, differential scanning calorimetry (DSC), immunoblotting and determination of caspase-3/7 activity in the culture medium. The characteristic changes in chromatin complex induced upon the above treatments were detected by DSC, a simple thermal technique. This study received approval of the Medical University of Lodz Ethical Committee (RNN/196/07/KE). Informed consent was obtained from all the patients. Results:Marked differences in the individual patients' sensitivity to the agents used were registered. A decrease or even loss of transition at 95±5°C in thermal scans of nuclear fraction preparations occurred in the treated cells in which apoptosis was induced. Remarkably, the changes in thermal profiles coincided with an accumulation of apoptotic cells, a decrease of the number of viable cells, and the changes in cellular levels as well as functional status of apoptosis-related proteins (caspase-9, Mcl-1) and CLL prognostic factor – kinase Zap-70. However, no significant changes were observed in thermal profiles of nuclei originating from CLL cells resistant to the treatment. Our studies revealed that the ex vivo exposure of CLL cells to CM combination, equivalent to clinically used CC regimen, was of prognostic value. Among the DSC profiles of nuclear preparations isolated from leukemic cells treated ex vivo with CM 70% of the cases examined indicated the decrease or loss of transition at about 95 ± 5°C. Moreover, we noticed a statistically significant dependence between the patient's response to CC treatment and thermal transition reduction at 95 ± 5°C (p=0.034). Interestingly, the results of the examined group did not show any correlation between disease advance (Rai stage) or cytogenetic abnormalities versus the clinical patient's response to the used treatment. Conclusion:Our results demonstrate the advantage of DSC in the evaluation of the treatment efficacy and indicate that its application could facilitate the choice of highly effective therapy for individual patients. Disclosures:No relevant conflicts of interest to declare.

Thermal structure of a gas‐permeable lava dome and timescale separation in its response to perturbation

The thermal boundary layer at the surface of a volcanic lava dome is investigated through a continuum model of the thermodynamic advection‐diffusion processes resulting from magmatic gas flow through the dome matrix. The magmatic gas mass flux, porosity, and permeability of the rock are identified as key parameters. New, theoretical, nonlinear steady state thermal profiles are reported, which give a realistic surface temperature of 210°C for a region of lava dome surface through which a gas flux of 3.5 × 10−3 kg s−1 m−2 passes. This contrasts favorably with earlier purely diffusive thermal models, which cool too quickly. Results are presented for time‐dependent perturbations of the steady states as a response to changes in surface pressure, a sudden rockfall from the lava dome surface, and a change in the magmatic gas mass flux at depth. Together with a generalized analysis using the method of multiple scales, this identifies two characteristic timescales associated with the thermal evolution of a dome carapace: a short timescale of several minutes, over which the magmatic gas mass flux, density, and pressure change to a new quasi‐steady state and a longer timescale of several days, over which the thermal profile changes to a new equilibrium distribution. Over the longer timescale, the dynamic properties of the dome continue to evolve, but only in slavish response to the ongoing temperature evolution. In light of this timescale separation, the use of surface temperature measurements to infer changes in the magmatic gas flux for use in volcanic hazard prediction is discussed.

Temperature changes in exhaled breath condensate collection devices affect observed acetone concentrations

Chemical analysis of exhaled breath condensate (EBC) is an emerging method to non-invasively identify and measure potential biomarkers of disease. Various EBC collection methods have been proposed, each with strengths and weaknesses. Recent evidence in the literature suggests that sample collection methodologies could introduce potential artifacts in biomarker measurements. In this study, we tested the effect of thermal changes during condensate collection on measured EBC chemical concentrations. Using both actively-cooled and passively-cooled devices, we measured distinct differences in the amount of condensate that can be collected over discrete time periods. We also found that concentrations of acetone varied with the thermal profile changes in the collection devices, in apparently identical EBC samples. Together, this evidence suggests that great care should be taken to standardize EBC collection methods, and that small deviations in the thermal properties of the collection devices could contribute to confounding EBC measurement artifacts. This has implications for the design and development of future portable breath analysis systems, especially miniature hand-held devices.

Effects of microwave heating on the quality characteristics and thermal properties of RBD palm olein

In the present work, the influence of microwave power (low-, medium- and high-power settings) and heating time on lipid deterioration produced during the microwave heating of RBD palm olein (RBDPO O) was evaluated. The changes in thermal profiles by differential scanning calorimetry (DSC) were studied in comparison to the changes in chemical parameters. The DSC method was based on the cooling and melting curves of oils at a scanning rate of 5 °C/min. The chemical evaluation of the oils was based on free fatty acid content, C18:2/C16:0 ratio, peroxide, iodine, and anisidine values. The DSC results were explained on the basis of the endo- or exothermic peak temperatures. A statistical comparative study was carried out on the DSC and chemical parameters. The results indicate that there is a good correlation between the DSC and chemical methods. Based on the results obtained, the DSC appears to be a useful instrumental method in monitoring the oxidation of microwave heated oils, and it may have the potential to replace the time- and chemical-consuming standard chemical methods.

Thermal investigation of some mixed-ligand copper(II) chelates containing 1,2-diamines and β-ketoenols

Thermal studies by TG/DTA and/or TG/DTG techniques of some mixed-ligand copper(II) chelates were carried out to determine their stabilities and modes of decomposition. The chelates have the formula [Cu(β-dione)(enR)]X, where β-dione is the anion of a β-ketoenol, enR is N,N′-substituted aryl or alkyl ethylenediamine and X is NO3− or ClO4−, while the geometry of the ensuing chromophore CuN2O2 is square-planar. The degradation processes depend on the anions and the substituents of the ligands. The nitrate compounds are decomposed until the stable oxide, CuO, is formed at ∼560°C in both air and nitrogen. The perchlorate compounds, however, are strong explosives in air and vigorously loose almost all their weight in one step. In nitrogen, the thermal profile changes dramatically and instead of explosion a decomposition process takes place affording a metallic residue at ∼800°C. Mass spectrometry (MS) was also used to give possible fragmentation patterns.

A Note on the Wall Singularity of a Solid–Liquid Interface Caused by a Difference Between the Thermal Conductivities of the Solid and the Liquid Phases

In crystal-growth systems of the Bridgman–Stockbarger type, the solid–liquid interface touches a conducting wall which is the inner wall of the crucible. When the thermal conductivities of the solid and the liquid phases are different, which they usually are, the gradient of the axial thermal profile changes abruptly at the $s - 1$ interface. Since the thermal profile in the adjacent crucible cannot experience such a jump, the $s - 1$ interface must accommodate for this difference in thermal behavior at the wall. Using a fairly simple model example, we show that the $s - 1$ interface becomes singular there. The singularity is a weak logarithmic one.

The inward solidification of spheres and circular cylinders

An analytical study is presented of the inward freezing of a sphere or a circular cylinder, initially molten and at the fusion temperature, when the outside surface is suddenly cooled. The treatment assumes, among other things, constant thermal properties and that the parameter β, the ratio of the latent heat to the sensible heat of the substance, is large. Basic series solutions are first derived and these are then followed by a two-region analysis which is needed to accommodate the sharp change in thermal profile just before the centre of the sphere or the cylinder solidifies. Although the theory is strictly asymptotic in nature, results compare well with numerical solutions of the full problem for β = 10 and 20 (cylinder) and β = 10 (sphere).