Melting Temperature Measurements Research Articles

Experimental Assessment of a Novel Eutectic Binary Molten Salt-based Hexagonal Boron Nitride Nanocomposite as a Promising PCM with Enhanced Specific Heat Capacity

In this study, novel nanocomposites containing the pre-defined mass ratio of binary molten salt (NaNO3-KNO3: 60-40 wt. %) dispersed with hexagonal boron nitride (hBN) nanoparticles with nominal size of 70 nm, were prepared through one-phase preparation method. Four different types of samples including pure binary molten salt and binary molten salt-based hBN nanocomposites with loading concentrations of 0.5, 1 and 1.5 wt. % were prepared. The proposed amount of sodium nitrate and potassium nitrate was added to certain amount of DI water, comprising with 0.5, 1 and 1.5 wt. % concentration of hBN nanoparticles. Scanning electronic microscopy (SEM) was conducted to evaluate the uniformity of the synthesized binary molten salt-based hBN nanocomposites. The SEM images revealed uniform dispersion of hexagonal boron nitride nanoparticles and fractal-like structures were observed clearly. Specific heat capacity (cp) and melting temperature measurements were performed using a differential scanning calorimetry (DSC). The experimental achieved data for melting temperature proved that hexagonal boron nitride nanoparticles do not affect the melting temperature of the synthesized nanocomposites. The experimentally achieved data for the average cp values of the binary molten salt in solid and liquid phases were 1.14 and 1.13 J/g K, respectively. While, the average cp values for the binary molten salt-based hBN nanocomposite with the highest loading concentration of nanoparticles (1.5 wt. %) in solid and liquid phases were 2 and 3.17 J/g K, respectively. The measured average cp value in the liquid phase for binary molten salt-based hBN nanocomposite with the highest loading concentration (1.5 wt. %) of nanoparticles revealed enhancement of ~180% in comparison with pure binary molten salt. Thermal stability measurements expressed enhancement of thermal stability in binary molten salt induced with hBN nanoparticles. Binary molten salt-based hBN nanocomposite with loading concentration of 1.5 wt. % represented ~16% enhancement in thermal stability over the binary molten salt.

Thermal characterization of the In–Sn–Zn eutectic alloy

Thermal properties, including melting temperature, latent heat of melting, specific heat capacity and thermal conductivity, of a low-melting In–Sn–Zn eutectic alloy were investigated in this work. The In–Sn–Zn eutectic alloy with nominal composition 52.7In-44.9Sn-2.4Zn (at.%) was prepared by the melting of pure metals under an argon atmosphere. The conducted assessment consisted of both theoretical and experimental approaches. Differential scanning calorimetry (DSC) was used for the measurement of melting temperature and latent heat, and the obtained results were compared with the results of thermodynamic calculations. The measured melting temperature and the latent heat of melting for the In–Sn–Zn eutectic alloy are 106.5±0.1 °C and 28.3±0.1 Jg-1, respectively. Thermal diffusivity and thermal conductivity of the In–Sn–Zn eutectic alloy were studied by the xenon-flash method. The determined thermal conductivity of the investigated eutectic alloy at 25 °C is 42.2±3.4 Wm-1K-1. Apart from providing insight into the possibility for application of the investigated alloy as the metallic phase-change material, the obtained values of thermal properties can also be utilized as input parameters for various simulation processes such as casting and soldering.

Melting temperature measurement and mesoscopic evaluation of single, double and triple DNA mismatches.

Unlike the canonical base pairs AT and GC, the molecular properties of mismatches such as hydrogen bonding and stacking interactions are strongly dependent on the identity of the neighbouring base pairs. As a result, due to the sheer number of possible combinations of mismatches and flanking base pairs, only a fraction of these have been studied in varying experiments or theoretical models. Here, we report on the melting temperature measurement and mesoscopic analysis of contiguous DNA mismatches in nearest-neighbours and next-nearest neighbour contexts. A total of 4032 different mismatch combinations, including single, double and triple mismatches were covered. These were compared with 64 sequences containing all combinations of canonical base pairs in the same location under the same conditions. For a substantial number of single mismatch configurations, 15%, the measured melting temperatures were higher than the least stable AT base pair. The mesoscopic calculation, using the Peyrard–Bishop model, was performed on the set of 4096 sequences, and resulted in estimates of on-site and nearest-neighbour interactions that can be correlated to hydrogen bonding and base stacking. Our results confirm many of the known properties of mismatches, including the peculiar sheared stacking of tandem GA mismatches. More intriguingly, it also reveals that a number of mismatches present strong hydrogen bonding when flanked on both sites by other mismatches. To highlight the applicability of our results, we discuss a number of practical situations such as enzyme binding affinities, thymine DNA glycosylase repair activity, and trinucleotide repeat expansions.

Monocyclic phenolic compounds stabilize human insulin and suppress its amorphous aggregation: In vitro and in vivo study

Insulin is a small protein with 51 residues that mediates glucose uptake, and an interesting model for studying protein misfolding and aggregation. The aggregated forms of insulin undergo loss of activity and can provoke unwanted immune responses.Use of small molecules is considered to be an affordable method to counteract this aggregation process and stabilize insulin. In this study, aggregated forms of human recombinant insulin have been produced following exposure to high temperature. Aggregation process was followed over time by checking absorbance with spectrophotometry in presence and absence of various concentrations of small phenolic compounds including eugenol and epinephrine. Effects of these compounds on the structure and function of incubated insulin were evaluated by spectrofluorimetry, melting temperature (Tm) measurement and insulin tolerance test on Wistar rats. Formation of heat-induced insulin aggregation can be effectively inhibited by 1 mM eugenol and epinephrine and both compounds were found to preserve insulin activity to a considerable extent. In conclusion, simple aromatic compounds could be tailored to act as potent anti-aggregation compounds for insulin.

Reexamination of the equilibrium melting temperature of natural rubber crystals

The equilibrium melting temperature ($$T_{\mathrm{m}}^0$$) of natural rubber crystals was reexamined by the Hoffman–Weeks plot and the Gibbs–Thomson plot using the lamellar thickness obtained from the same sample as the one used for the measurement of melting temperature. The sample was prepared from deproteinized latex. As a result, the $$T_{\mathrm{m}}^0$$ of NR was estimated to be 61 °C. At the same time, the fold-surface free energy was estimated to be 0.046 Jm−2. These values should be more reliable than the previously assumed values. The equilibrium melting temperature ($$T_{\mathrm{m}}^0$$) of natural rubber crystals was reexamined by the Hoffman–Weeks plot and the Gibbs–Thomson plot using the lamellar thickness obtained from the same sample as the one used for the measurement of melting temperature. The sample was prepared from deproteinized latex. As a result, the $$T_{\mathrm{m}}^0$$ of NR was estimated to be 61 °C. At the same time, the fold-surface free energy was estimated to be 0.046 Jm−2. These values should be more reliable than the previously assumed values.

Probing Thermal Stability of Proteins with Temperature Scanning Viscometer.

Thermal stability is essential for the understanding of protein stability and is a critical quality attribute of therapeutic biologics, including enzymes, fusion proteins, monoclonal antibodies, etc. The commonly used analytical methods, such as differential scanning calorimetry (DSC), differential scanning fluorimetry (DSF), and circular dichroism (CD), have their limitations in measuring protein thermal stability. Through this work, we described a novel method to probe the thermal stability of proteins in various formulations using a temperature scanning viscometer. The viscosity of the material was plotted against the temperature, and the peak in the first derivative of the viscosity versus temperature was shown to be related to the protein melting temperature. The measured melting temperature of bovine serum albumin (BSA) at a concentration of 1 mg/mL in phosphate buffer was 63 °C, which was close to the value of 64 °C obtained by DSC. The unfolding of BSA was confirmed using orthogonal techniques of second derivative ultraviolet-visible (UV-vis) spectroscopy and dynamic light scattering (DLS). This method was also able to reveal the microenvironment changes of proteins, including formulation effects. Other multiple domains proteins including lysozyme and IgG were also tested using this method and showed comparable melting temperatures with DSC. This work showed the feasibility of using a temperature scanning viscometer to measure the thermal stability of proteins in diverse formulation matrices with wider protein concentration ranges.

Spectroscopic, Gel Electrophoretic, and Surface Plasmon Resonance Characterization of G‐Triplex DNA Formation

G‐triplex DNA is a recently discovered class of non‐canonical DNA structures related to G‐quadruplex DNA (G4). Originally identified as a folding intermediate in the formation of certain G4, G‐triplex DNA structures can be formed by oligonucleotides corresponding to truncated G4 sequences. Here we present a study of the sequence and environmental effects on G‐triplex formation using spectroscopic, gel electrophoretic, and surface plasmon resonance methods.We examined 16 different variants of the G≥2T1–4G≥2T1–4G≥2 sequence as well as truncated versions of the TBA and human telomeric G4 DNA in both forward and reverse permutations. CD spectroscopy, UV thermal‐difference spectroscopy, CD and UV derived melting temperature measurements, SPR, agarose gel electrophoresis, and native PAGE gels were employed to characterize the topology and thermal stability of these structures in Li+, Na+, K+, Mg2+ and Ca2+ containing buffers. All of these sequences can adopt G‐triplex structures. However, we note that the number of nucleotides in the loop and sequence direction affect G‐triplex topology. Sequences with longer G‐tracks tend to form parallel G‐triplex, as do sequences with fewer loop residues. Permutation of the direction of the truncated G4 DNA sequence also affect G‐triplex folding topology. Environmental effects on topology were noted, with divalent metal ions (Mg2+ and Ca2+) favoring parallel topologies. Using thermal‐difference spectroscopy, we have identified two families of spectra that correlate to G‐triplexes with a parallel topology. Analysis by native PAGE indicates that some sequences may form multiple G‐triplex topologies under certain environmental conditions. Temperature melts show that sequences with longer G‐runs (GGGG > GGG > GG) and shorter T‐loops (TT >TTT > TTTT) form G‐triplex structures that are more thermally stable. Direction of sequence also effects the stability. Environmental conditions such as the presence of different cations have an effect on stability (Ca2+ > K+ > Mg2+ ≥ Na+). Analysis by agarose gel electrophoresis has suggested that some sequences of G‐triplex forming DNA fold into monomeric intramolecular structures, while sequences with long G‐runs form highly oligomeric species. SPR has also been performed in order to probe G‐triplex formation. Immobilized G‐triplex‐forming sequences were probed with short, complementary C‐rich oligonucleotides and the kinetics of hybridization under different buffer conditions provides further insight into the stability and kinetics of G‐triplex formation.The biological relevance of G‐triplex DNA is still not entirely understood. Understanding how sequence effects and environmental conditions affect G‐triplex structure and stability is essential for better studying G‐quadruplex DNA and the biological relevance of G‐triplex DNA.Support or Funding InformationCRPIT HIHR Grant RP160852 and Texas State UniversityThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Phase-Change Materials/HDPE Composite Filament: A First Step Toward Use With 3D Printing for Thermal Management Applications

Phase-change materials (PCMs) are a useful alternative to more traditional methods of thermal management of various applications. PCMs are materials that absorb large amounts of latent heat and undergo solid-to-liquid phase change at near-constant temperature. The goal of the research is to experimentally investigate the thermal properties of a novel shape-stabilized PCM/HDPE composite extruded filament. The extruded filament can then be used in a 3D printer for custom PCM/HDPE shapes. The PCM used in the study is PureTemp PCM 42, which is an organic-based material that melts around 42 °C. Four PCM/HDPE mixtures were investigated (all percentages by mass): 20/80, 30/70, 40/60, and 50/50. Preliminary findings include differential scanning calorimeter (DSC) measurements of melting temperature and latent heat as well as scanning electron microscope (SEM) pictures of filament composition.

Solubility of p-xylene in methane and ethane and implications for freeze-out at LNG conditions

Even at trace concentrations the presence of heavy hydrocarbons such as BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) in liquefied natural gas (LNG) production streams poses a significant risk of blockage and eventually plant shutdown. However, although p-xylene has the highest melting temperature of all the BTEX compounds, no data are available for its solubility in liquid methane or ethane. In this work, sapphire equilibrium cells housed in either an air bath or a cryogenic thermostat fitted with periscopes were used to measure melting (liquidus) temperatures for synthetically prepared methane + p-xylene and ethane + p-xylene mixtures at temperatures from 200 K and pressures up to 22.5 MPa. Peltier-driven copper posts, which could be sub-cooled relative to the bulk liquid mixture, controlled the location of the solid formed within each cell. For the methane + p-xylene system both VLE and SLVE data sets were measured and used separately to tune the binary interaction parameter (BIP) within the Peng Robinson equation of state. The VLE-tuned BIP systematically under-predicted the measured melting temperatures for this binary by up to 5.2 K, while the SLVE-tuned BIP could represent the melting temperature data with an r.m.s. deviation of 0.4 K. For ethane + p-xylene, a BIP estimated using a group contribution method systematically over-predicted the measured melting temperatures by as much as 14.6 K. Tuning the ethane + p-xylene BIP to the measured SLE data more than halved the model’s r.m.s. deviation to 3.1 K. The use of BIPs tuned to VLE data rather than SLVE data has significant implications for freeze-out risk assessments in LNG production. For example, at operating conditions typical of an LNG plant’s main cryogenic heat exchanger, the solubility of p-xylene in liquid methane predicted using a BIP tuned to VLE data is 20 times larger than the solubility predicted using a BIP tuned to SLVE data.

Sample pattern and temperature distribution in nanocalorimetry measurements

Uniform temperature distribution over the probed area of nanocalorimeters is critical for accurate measurements and is often assumed, but the temperature distribution is, in many cases, non-uniform, depends on the sample dimensions and coverage, and can affect the measurement results. Here, using an aluminum thin film as a model material, the effects of sample coverage on measured melting temperature and enthalpy of fusion were studied. Results suggest that undersized samples increase the reported peak and onset values for melting temperature, and that oversized samples cause significant errors in the quantification of the enthalpy of fusion. A finite element model of the dynamics of the temperature distribution was created to clarify the underlying mechanisms. This work provides a simple guideline for the ideal sample pattern for chip-based thermal measurements: covering the entire probed area of the heater: not undersized or oversized.

Synthesis, characterization and molecular docking of new C,N‐palladacycles containing pyridinium‐derived ligands: DNA and BSA interaction studies and evaluation as anti‐tumor agents

Four new monomeric Pd (II) complexes with formulas [Pd(C,N)‐(2′‐NH2C6H4)C6H4 (N3)(L)] (A), (B) and [Pd(C,N)‐C6H4CH2NH(C4H9)(N3)(L)] (C), (D), [L = isonicotinamide for (A) and (C), L = 4‐N,N‐dimethylaminopyridine for (B) and (D)] have been synthesized using four initial dimers [Pd2{(C,N)‐(2′‐NH2C6H4)C6H4}2(μ‐OAc)2] (1), [Pd2{(C,N)‐ (2′‐NH2C6H4)C6H4}2(μ‐N3)2] (3) for A and C, and [Pd2{(C,N)‐C6H4CH2NH(C4H9)}2(μ‐OAc)2] (2) and [Pd2{(C,N)‐C6H4CH2NH(C4H9)}2(μ‐N3)2] (4) for B and D. Then synthesized complexes have been characterized by Fourier transform‐infrared, NMR spectroscopy and thermal gravimetric‐differential thermal analysis. Furthermore, UV–Vis spectroscopy, fluorescence spectroscopy, circular dichroism (CD) and helix melting temperature measurements have been employed to study the binding interaction of them with calf thymus‐deoxyribonucleic acid (DNA). The results reveal that all synthesized complexes can interact with DNA via groove‐binding mode. Bovine serum albumin (BSA)‐binding studies have been carried out using UV–Vis spectroscopy, emission titration and CD. However, competitive binding studies using warfarin, ibuprofen and digoxin on site markers demonstrated that the complexes bind to different sites on BSA. The results also indicated that the binding site was mainly located within site‐III for complex A, and site‐I for complexes B, C and D of BSA. In addition, molecular docking studies have been executed to determine the binding site of the DNA and BSA with complexes. Eventually, in vitro cytotoxicity of synthesized palladium complexes and cisplatin were carried out against human promyelocytic leukemia cancer (Hela) and breast cancer (MCF‐7) cell lines. Pursuant to the IC50 values, the cytotoxicity of complexes against MCF‐7 was more than Hela.

Sequence-Dependent Three Interaction Site Model for Single- and Double-Stranded DNA.

We develop a robust coarse-grained model for single- and double-stranded DNA by representing each nucleotide by three interaction sites (TIS) located at the centers of mass of sugar, phosphate, and base. The resulting TIS model includes base-stacking, hydrogen bond, and electrostatic interactions as well as bond-stretching and bond angle potentials that account for the polymeric nature of DNA. The choices of force constants for stretching and the bending potentials were guided by a Boltzmann inversion procedure using a large representative set of DNA structures extracted from the Protein Data Bank. Some of the parameters in the stacking interactions were calculated using a learning procedure, which ensured that the experimentally measured melting temperatures of dimers are faithfully reproduced. Without any further adjustments, the calculations based on the TIS model reproduce the experimentally measured salt and sequence-dependence of the size of single-stranded DNA (ssDNA), as well as the persistence lengths of poly(dA) and poly(dT) chains. Interestingly, upon application of mechanical force, the extension of poly(dA) exhibits a plateau, which we trace to the formation of stacked helical domains. In contrast, the force-extension curve (FEC) of poly(dT) is entropic in origin and could be described by a standard polymer model. We also show that the persistence length of double-stranded DNA, formed from two complementary ssDNAs, is consistent with the prediction based on the worm-like chain. The persistence length, which decreases with increasing salt concentration, is in accord with the Odijk-Skolnick-Fixman theory intended for stiff polyelectrolyte chains near the rod limit. Our model predicts the melting temperatures of DNA hairpins with excellent accuracy, and we are able to recover the experimentally known sequence-specific trends. The range of applications, which did not require adjusting any parameter after the initial construction based solely on PDB structures and melting profiles of dimers, attests to the transferability and robustness of the TIS model for ssDNA and dsDNA.

Identifying and avoiding off-target effects of RNase H-dependent antisense oligonucleotides in mice.

Antisense oligonucleotides that are dependent on RNase H for cleavage and subsequent degradation of complementary RNA are being developed as therapeutics. Besides the intended RNA target, such oligonucleotides may also cause degradation of unintended RNA off-targets by binding to partially complementary target sites. Here, we characterized the global effects on the mouse liver transcriptome of four oligonucleotides designed as gapmers, two targeting Apob and two targeting Pcsk9, all in different regions on their respective intended targets. This study design allowed separation of intended- and off-target effects on the transcriptome for each gapmer. Next, we used sequence analysis to identify possible partially complementary binding sites among the potential off-targets, and validated these by measurements of melting temperature and RNase H-cleavage rates. Generally, our observations were as expected in that fewer mismatches or bulges in the gapmer/transcript duplexes resulted in a higher chance of those duplexes being effective substrates for RNase H. Follow-up experiments in mice and cells show, that off-target effects can be mitigated by ensuring that gapmers have minimal sequence complementarity to any RNA besides the intended target, and that they do not have exaggerated binding affinity to the intended target.

Efficient Synthesis of Light-Triggered Circular Antisense Oligonucleotides Targeting Cellular Protein Expression.

Light-activated ("caged") antisense oligonucleotides are powerful molecules for regulating gene expression at submicron spatial resolution through the focal modulation of endogenous cellular processes. Cyclized caged oligos are particularly promising structures because of their inherent stability and similarity to naturally occurring circular DNA and RNA molecules. Here, we introduce an efficient route for cyclizing an antisense oligodeoxynucleotide incorporating a photocleavable linker. Oligo cyclization was achieved for several sequences in nearly quantitative yields through intramolecular copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). Caging stability and light activation were characterized by FRET efficiency, denaturing gel assay, and melting temperature measurements. Finally, a cyclized caged oligo was designed to target gfap, and it gave a tenfold reduction in glial fibrillary acidic protein upon photoactivation in astrocytes.

Determination of the liquidus temperature of tin using the heat pulse-based melting and comparison with traditional methods

In this work, the liquidus temperature of tin was determined by melting the sample using the pressure-controlled loop heat pipe. Square wave-type pressure steps generated periodic 0.7 °C temperature steps in the isothermal region in the vicinity of the tin sample, and the tin was melted with controllable heat pulses from the generated temperature changes. The melting temperatures at specific melted fractions were measured, and they were extrapolated to the melted fraction of unity to determine the liquidus temperature of tin. To investigate the influence of the impurity distribution on the melting behavior, a molten tin sample was solidified by an outward slow freezing or by quenching to segregate the impurities inside the sample with concentrations increasing outwards or to spread the impurities uniformly, respectively. The measured melting temperatures followed the local solidus temperature variations well in the case of the segregated sample and stayed near the solidus temperature in the quenched sample due to the microscopic melting behavior. The extrapolated melting temperatures of the segregated and quenched samples were 0.95 mK and 0.49 mK higher than the outside-nucleated freezing temperature of tin (with uncertainties of 0.15 mK and 0.16 mK, at approximately 95% level of confidence), respectively. The extrapolated melting temperature of the segregated sample was supposed to be a closer approximation to the liquidus temperature of tin, whereas the quenched sample yielded the possibility of a misleading extrapolation to the solidus temperature. Therefore, the determination of the liquidus temperature could result in different extrapolated melting temperatures depending on the way the impurities were distributed within the sample, which has implications for the contemporary methodology for realizing temperature fixed points of the International Temperature Scale of 1990 (ITS-90).

Synthesis, crystal structure and DNA interaction of a new water-soluble derivative of pyrazino[2,3-f][1,10] phenanthroline; theoretical calculations, experimental and molecular docking studies

The new water-soluble derivative of pyrazino[2,3-f][1,10] phenanthroline has been synthesized and characterized by conductivity measurement, elemental analysis, FT-IR, 1H NMR, 13C NMR spectroscopic studies, as well as single crystal x-ray crystallography. Theoretical calculations have been performed using the density functional theory (DFT) in order to confirm the structure and understand the electronic structure of the synthesized compound. The DNA binding properties of the compound were investigated by absorption spectroscopy, melting temperature and viscosity measurements. The intrinsic binding constant, Kb, was determined as 7.84 × 103 M−1 at 298 K. Thermodynamic parameters showed that the binding interaction is enthalpy-favored. All of the experimental results indicated that the binding mode of interaction between this compound and CT-DNA is groove binding. Furthermore, molecular modeling studies was done to confirm the binding mode.

Multi-spectroscopic and molecular modeling studies to reveal the interaction between propyl acridone and calf thymus DNA in the presence of histone H1: binary and ternary approaches

DNA is the primary target of many anticancer drugs involved in important intercellular processes, especially in transcriptional regulation, and histone is known to inhibit gene expression. Small molecules can bind to histone-DNA and impair the cell division, growth, inhibition, and apoptosis in cancer cells. In this research, the interaction of a histone H1-calf thymus DNA (ct DNA) complex and propyl acridone (PA) was investigated in Tris-HCl buffer, pH 6.8, using multi-spectroscopic, viscosity, and molecular modeling techniques. The Stern Volmer plot of the (H1-ct DNA) PA complex demonstrated two sets of binding sites with various binding affinities at three different temperatures. Thermodynamic parameters (ΔH° < 0 and ΔS° < 0) indicated that hydrogen bonds and van der Waals forces played the main roles in the binding of the drug to H1-ct DNA. The interaction between PA and ct DNA as well as (H1-ct-DNA) in the presence of acridine orange and ethidium bromide showed two different interaction behaviors in ternary systems. According to results from UV absorption spectroscopy and melting temperature (Tm) measurements, the binding mode of PA with ct DNA and the (H1-ct DNA) complex was indicative of an intercalative binding for the binary system and of both intercalative with groove binding with molecular fraction for the ternary system. Furthermore, the PA-induced detectable changes in the circular dichroism spectrum of ct DNA as well as changes in its viscosity. All of the experimental results proved that the intercalative binding between PA and ct DNA as well as the (H1-ct DNA) complex as binary and ternary systems must be predominant. The results obtained from experimental data were in good agreement with molecular modeling with regard to the determination of the binding site of PA to ct DNA in the absence and presence of histone H1.

Novel Na2SO4-NaCl-ceramic composites as high temperature phase change materials for solar thermal power plants (Part I)

The eutectic Na2SO4-NaCl salt was investigated as a novel high temperature phase change material for solar thermal energy storage due to its low cost and melting point (626.0°C) interested. The measured melting point and heat of fusion of the eutectic salt are 625.3°C and 263.3J/g, which are in agreement with their theoretical values. The eutectic salt shows good thermal stability after 100 melting-freezing thermal cycles in the range of 550–680°C in air. Three types of the eutectic Na2SO4-NaCl-ceramic composites have been designed and evaluated to address the salt’ corrosion issues with containment materials. Results show that eutectic Na2SO4-NaCl/both α-alumina and mullite composites with a mass ratio of salt to ceramics of 1:1 (wt%) have good thermal stability without cracking as well as with weight losses of 0.50% and 0.74% and the decrease of latent heat by 1% and 2% respectively after 20 thermal cycles, where no phase separation and chemical reaction occur. Their measured melting temperature and latent heat are consistent with their theoretical values. Addition of α-alumina and mullite to the eutectic Na2SO4-NaCl salt can reduce the eutectic Na2SO4-NaCl salt’ supercooling. In contrast, the sample of the Na2SO4-NaCl/diatomite composite cracked after the cycles.

Validation of an In-Mold Multivariate Sensor for Measurement of Melt Temperature, Pressure, Velocity, and Viscosity

Abstract A multivariate sensor (MVS) is described for measurement of melt temperature, melt pressure, melt velocity, and melt viscosity. Melt pressure and temperature are respectively obtained through the incorporation of a piezo-ceramic element and infrared thermopile. Melt velocity is derived from the initial response of the melt temperature as the polymer melt flows across the sensor lens. The apparent melt viscosity is then derived based on the melt velocity and the time derivative of the increasing melt pressure. The response of the MVS is analyzed using an instrumented mold including piezoelectric pressure sensors, an infrared pyrometer, and thermocouples. A 12-run, blocked half-fractional design of experiments (DOE) was run to characterize the effect of melt temperature, mold temperature, packing pressure, and ram velocity. The results show that the MVS provides excellent measurement of melt temperature and pressure. The accuracy of the melt velocity estimations depended on the ram velocity set-point, yielding a coefficient of determination of 0.91 for the lower ram velocities, and reaching saturation for melt velocities about 450 mm/s. The apparent melt viscosity estimated by the MVS are close to those predicted by the Cross-WLF model, exhibiting appropriate shear thinning but behavior but inconsistent temperature dependence.

Polymer resonators sensors for detection of sphingolipid gel/fluid phase transition and melting temperature measurement

This work describes a low-cost biophotonic sensor shaped by way of cheap processes as hybrid silicon/silica/polymer resonators able to detect biological molecule gel/fluid phase transition as lipids at very low concentration (sphingomyelin). The photonic structure is composed of specific amplified deep UV photoresist-polymer waveguides coupled by a sub-wavelength gap with racetrack microresonators allowing a low temperature-dependent operation ranging from 16 to 42°C. The temperature dependent wavelength shift and the thermo-optic coefficient characterizing the quantified resonances and opto-geometric properties of the device have been evaluated, highlighting an enough low thermal features of the whole system for such application. With an appropriate vesicle lipid deposition process specific in biology associated to an apt experimental bio-thermo-photonic protocol (made of serial optical resonance spectra acquisitions with statistical treatments), the dynamic evolution of the sphingomyelin lipid phase transition was assessed: then, the ability to detect their own gel/fluid transition phase and melting temperature has been demonstrated with a mass product factor 107 lower than that of more conventional methods The equilibrium of the regime of the resonators was highlighted as being broken by the dynamic of the sphingomyelin and its own phase transition prior relevant detection.