Large Heat Capacity Research Articles

FEATURES OF PHASE DIAGRAMS OF A TWO-FREQUENCY PENDULUM IN JAN-TELLER POTENTIAL AND HEAT CAPACITY OF WATER

A simulation of rotational vibrations of a water molecule was carried out using a model of a two-frequency pendulum in a simple Jahn–Teller potential (JTP), which has a minimum potential at a certain angle of deviation of the pendulum from the axis (the bending angle of the intermolecular hydrogen bond of the water molecule). It has been established that at low initial speeds for a given potential a new type of oscillations is observed - transverse oscillations of the pendulum inside the circular gutter JTP, at medium speeds - two-frequency independent oscillations (IO) along two axes, and at large ones - ellipse-like oscillations (ELO) at a single frequency. The work examines phase diagrams (PD) and mixed PD (MPD) in two coordinates for these two-dimensional oscillations. A significant difference between these diagrams in the JTP and standard PD is shown. The appearance of additional ellipses, loops and waves on the PD due to the appearance of transverse vibrations in the nuclear fuel gutter was discovered. To obtain ellipses in phase diagrams from all transverse oscillations of the pendulum, it is proposed to construct a PD versus radius (PDR) for the oscillation trajectory. It is shown that ellipses on the PDR for transverse oscillations of the pendulum are clearly observed at low initial speeds, but for medium and high speeds the transverse part of speed is not independently distinguished from the total speed. The presence of stable transverse vibrations in the JTP gutter for rotational vibrations of hydrogen atoms of water molecules around the axes of intermolecular bonds can be considered as new degrees of freedom for its new collectivized transverse vibrations in this potential. Their existence may lead to an explanation for the contribution of these types of oscillations to the anomalously large heat capacity of water in the liquid phase. However, for the presence of such new degrees of freedom for transverse vibrations of water molecules, it is necessary that their vibrations always take place in the region of “small” velocities - in the JTP gutter. To do this, it is necessary to increase this range of vibrations so that the maximum value of the potential on the axis of the intermolecular bond would be large. This should ensure the existence of transverse rotational oscillations in the JTP gutter for water molecules in all liquid phase temperatures.

Melting properties of the refractory metals V and W and the binary VW alloy fully from first principles

We investigate the melting properties of the bcc refractory metals V and W, and the disordered equiatomic VW alloy from first principles. We show that thermal vibrations have a large impact on the electronic density of states (DOS) and thus considerably affect the electronic contribution to the free energy. For W, the impact of vibrations on the electronic free energy of solid and liquid is different. This difference substantially impacts the computed melting point and also triggers a large electronic heat capacity difference between solid and liquid. For V, although vibrations likewise affect the electronic free energy, the effect on the melting properties cancels out to a large degree. For the binary VW alloy we observe a similar impact as for W, but slightly weaker. The underlying physics is explained in terms of the electronic DOS of the solid and liquid phases. Based on our accurate first-principles results, we reveal critical limitations of the Sommerfeld approximation in predicting the electronic heat capacity difference between solid and liquid. Our results thus prompt us to scrutinize this approximation which is often used in phase diagram parametrizations in the CALPHAD approach, as well as for materials, such as W, that have a large electronic DOS difference between solid and liquid at the melting temperature. Published by the American Physical Society 2024

Study of the Large Local Specific Heat Capacity Impact on Turbulent Heat Transfer at Supercritical Pressure

Study of the Large Local Specific Heat Capacity Impact on Turbulent Heat Transfer at Supercritical Pressure

Snapshots of the Reaction Coordinate of a Thermophilic 2'-Deoxyribonucleoside/ribonucleoside Transferase.

Nucleosides are ubiquitous to life and are required for the synthesis of DNA, RNA, and other molecules crucial for cell survival. Despite the notoriously difficult organic synthesis of nucleosides, 2'-deoxynucleoside analogues can interfere with natural DNA replication and repair and are successfully employed as anticancer, antiviral, and antimicrobial compounds. Nucleoside 2'-deoxyribosyltransferase (dNDT) enzymes catalyze transglycosylation via a covalent 2'-deoxyribosylated enzyme intermediate with retention of configuration, having applications in the biocatalytic synthesis of 2'-deoxynucleoside analogues in a single step. Here, we characterize the structure and function of a thermophilic dNDT, the protein from Chroococcidiopsis thermalis (CtNDT). We combined enzyme kinetics with structural and biophysical studies to dissect mechanistic features in the reaction coordinate, leading to product formation. Bell-shaped pH-rate profiles demonstrate activity in a broad pH range of 5.5-9.5, with two very distinct pKa values. A pronounced viscosity effect on the turnover rate indicates a diffusional step, likely product (nucleobase1) release, to be rate-limiting. Temperature studies revealed an extremely curved profile, suggesting a large negative activation heat capacity. We trapped a 2'-fluoro-2'-deoxyarabinosyl-enzyme intermediate by mass spectrometry and determined high-resolution structures of the protein in its unliganded, substrate-bound, ribosylated, 2'-difluoro-2'-deoxyribosylated, and in complex with probable transition-state analogues. We reveal key features underlying (2'-deoxy)ribonucleoside selection, as CtNDT can also use ribonucleosides as substrates, albeit with a lower efficiency. Ribonucleosides are the building blocks of RNA and other key intracellular metabolites participating in energy and metabolism, expanding the scope of use of CtNDT in biocatalysis.

Constructal design of a PCM cylindrical heat sink with three‐branched, two‐stages dendritic tubes

AbstractAmputees who use prosthetic limbs suffer from the problem of high contact temperature between the socket of the prosthetic limb and the amputated part and lack of evaporation of sweat. These conditions lead to discomfort and failure to perform functions properly. In addition, these conditions help generate ulcers and accumulate harmful bacteria in this area. This paper presents a heatsink design to extract heat from the contact area. A cylindrical heat sink is designed for phase‐changing materials with three branched tubes in two stages. The current heat sink is used to cool the contact area between the amputated part and the socket in the lower prostheses. Three distributions of pipe branches are proposed. The distribution and pipe lengths were obtained using a constructal design method. In the constructal design, the lengths of the branched tubes were the degrees of freedom, the objective function was the minimization of the inlet temperature to the heat sink, and the constraint was the volume of the cylindrical heat sink. The metabolic heat transfer during exercise was estimated and its value was used to calculate the size of the cylindrical heatsink and the selection of the phase change material by testing three of them: water, tridecane, and dodecane. It was found that water gives the highest latent heat of melting and the lowest volume in addition to its availability. On the other hand, two cooling fluids were tested: water and air. It was found that water as a cooling fluid gave the lowest flow and the largest heat capacity. Constructal theory was used to design a cylindrical heat sink using branched tubes for the coolant in two steps: the first with three branches, and the second with nine branches. The degree of freedom for constructal theory was the length of the branches through the choice of their end locations. It was found that the branches of the highest length led to a reduction in temperature from 40°C to 15.48°C compared with the single tube, which reduced the temperature to 23.87°C. All tests recorded a pressure drop within the acceptable range of 3.1–5.43 Pa for the branches examined. The research demonstrated that using constructal theory achieved the best thermal dissipation within a restricted volume.

Hydrogel-stabilized supercooled salt hydrates for seasonal storage and controlled release of solar-thermal energy

Seasonal storage of solar-thermal energy within salt hydrate phase change materials (PCMs), which are known for their large latent heat capacity, suitable phase change temperature range and cost-effectiveness, has garnered...

Effect of N2 and CO2 on the Explosion Properties of High Equivalence Ratios of Hydrogen.

The explosion characteristics of premixed gases under different equivalence ratios (1.0-3.0) and inert gas addition (5-20%) are experimentally investigated, and sensitivity analysis of the radical reactions is carried out using the USC Mech II model to analyze the molar fraction of radicals. The results show that at high equivalence ratios, inert gas has little effect on flame stability. The addition of an inert gas reduces the tensile rate in the early stage of flame growth. At high equivalence ratios, CO2 inhibits explosive flame propagation twice as effectively as N2. Due to the large heat capacity and chemical kinetic effects, CO2 has a stronger inhibitory effect on the explosion pressure than N2, and the inhibition efficiency on the explosion strength is nearly twice that high. To further analyze the effect of different inert gas addition ratios on chemical kinetics, sensitivity analysis, and molar fraction simulations were performed. The thermal and chemical kinetic effects of CO2 cause later generation of H and OH radicals and the partial chain reaction involving CO2 causes a lower peak of H radicals than the peak of H radicals generated under an N2 atmosphere. However, CO2 is a direct reactant and the third body to produce a small chemical kinetic effect.

Micro-/nanohoneycomb-like porous silicon loaded with Ag particles leads to synergistic enhancement of photothermal and thermoelectric conversions for MEMS thermopile chip application

Infrared detection technology has extensive and important applications in both military and civilian fields. Due to the advantages including no refrigeration, wide spectral response range, no chopping, low cost, and simple output circuit, MEMS thermopile chip has become one of the research hotspots in the field of infrared detection. The working mode of the thermopile chip is based on the photothermal and thermoelectric conversions, which are achieved by the infrared absorber and thermocouples, respectively. Actually, the resulting complex multi-layer structure brings about the shortcomings of thermopile chips, such as large heat capacity, large loss of heat transfer, low stacking efficiency and long response time, which has become the bottleneck of performance improvement. This work proposes a new concept for achieving high-efficiency photothermal and thermoelectric conversions of the thermopile chip simultaneously by a monolayer of multi-functional material. Herein, a micro-/nanohoneycomb-like porous Si loaded with Ag particles was constructed by metal-assisted chemical etching. The etched Si/Ag was endowed with high-efficiency light absorption in a wide spectral range (2–20 µm) and thermoelectric conversion, with the help of synergistic effect of light trapping, phonon scattering, energy filtering, and plasmon resonance. Replacing the infrared absorption layer, thermocouple layer, and insulation layer of the thermopile chip by the as-constructed porous Si/Ag composite can significantly reduce the heat capacity and energy transfer loss of the chip. It is expected to acquire a leap in the performance of the thermopile infrared detectors, providing a new technical approach for breaking through the bottleneck of small-scale and high-performance thermopile chips.

Observation of weak ferromagnetism in the antiferromagnetic host and large electronic heat capacity in β-Mn-type structured Mn3Al alloy

Numerous interesting features of antiferromagnets open up the possibility of designing new antiferromagnetic materials that can be useful for spintronic device applications. Here we present the structural, magnetic, thermal and electrical transport properties of polycrystalline Mn3Al alloys prepared by arc melting. Rietveld refinement of the room temperature X-Ray diffraction patterns reveals that the arc-melted Mn3Al crystallizes in a β Mn phase (space group 213). Detailed analysis of the magnetic data suggests for a dominant antiferromagnetic ordering. However, an in-homogenous magnetic disorder is observed in the system having a weak ferromagnetic phase in the antiferromagnetic host. In spite of the strong spin fluctuations in this system, the signature of spin glass-like nature in these alloys are not observed as probed by the frequency-dependent AC-Susceptibility measurements. Furthermore, the heat capacity was insensitive to the applied field of 3 Tesla with a negligible magnetic contribution suggesting a large electronic contribution to the heat capacity in these alloys. This work provides a useful insight into the tunable physical properties of the Heusler alloys for exploring antiferromagnetic based spintronic applications.

Numerical analysis of mixed convection phenomena in heat transfer to supercritical pressure carbon dioxide inside a horizontal miniature tube

To clarify and evaluate the influence of buoyancy force on the heat transfer to SCO2 flowing in a horizontal miniature tube, in this study, mixed convection phenomena with strong variations in thermophysical properties were numerically studied using an in-house code. The numerical model was validated by comparing the predicted wall temperature and available experimental data obtained for SCO2 at different heat fluxes, and the results showed good agreement. The effects of the heat-to-mass flux ratio on the heat transfer characteristics and heat transfer mechanism were investigated under operating conditions having mass flux, heat flux, pressure, and inlet temperature of 600–1200 kg‧m−2‧s−1, 25–300 kW‧m−2, 8 MPa and 303 K, respectively. A transition in the heat transfer regime from enhanced to normal was found as the heat-to-mass flux ratio increased to 83.33 J·kg−1. A pseudo-trans-critical process occurred in the tube at a heat-to-mass flux ratio above 125 J‧kg−1, and the heat transfer to SCO2 could be classified into three stages based on the reduced bulk fluid temperature. Particularly, the wall temperature was inversely proportional to the mass flux within the reduced bulk fluid temperature ranging of 0.992–1.0. Analysis of the heat transfer mechanism showed that the location of the large heat capacity in the boundary layer and the buoyancy force were responsible for the variation in the heat transfer characteristics. The applicability of the existing buoyancy criterion was examined, and BuP = 6 was found to be reasonable for predicting the onset of the influence of the buoyancy force on heat transfer.

Characterization of the pH-dependent protein stability of 3α-hydroxysteroid dehydrogenase/carbonyl reductase by differential scanning fluorimetry.

The characterization of protein stability is essential for understanding the functions of proteins. Hydroxysteroid dehydrogenase is involved in the biosynthesis of steroid hormones and the detoxification of xenobiotic carbonyl compounds. However, the stability of hydroxysteroid dehydrogenases has not yet been characterized in detail. Here, we determined the changes in Gibbs free energy, enthalpy, entropy, and heat capacity of unfolding for 3α-hydroxysteroid dehydrogenase/carbonyl reductase (3α-HSD/CR) by varying the pH and urea concentration through differential scanning fluorimetry and presented pH-dependent protein stability as a function of temperature. 3α-HSD/CR shows the maximum stability of 30.79 kJ mol-1 at 26.4°C, pH 7.6 and decreases to 7.74 kJ mol-1 at 25.7°C, pH 4.5. The change of heat capacity of 30.25 ± 1.38 kJ mol-1 K-1 is obtained from the enthalpy of denaturation as a function of melting temperature at varied pH. Two proton uptakes are linked to protein unfolding from residues with differential pKa of 4.0 and 6.5 in the native and denatured states, respectively. The large positive heat capacity change indicated that hydrophobic interactions played an important role in the folding of 3α-HSD/CR. These studies reveal the mechanism of protein unfolding in HSD and provide a convenient method to extract thermodynamic parameters for characterizing protein stability using differential scanning fluorimetry.

Research on Cutting Temperature of GH4169 Turning with Micro-Textured Tools

The GH4169 superalloy has the characteristics of high strength, strong thermal stability, large specific heat capacity, small thermal conductivity, etc., but it is also a typical hard-to-cut material. When cutting this material with ordinary cutting tools, the cutting force is large, and the cutting temperature is high, which leads to severe tool wear and short service life. In order to improve the performance of tools when cutting GH4169, reduce the cutting temperature, and extend the service life of the tool, micro-textured tools were used to cut GH4169 in spray cooling. The effects of micro-texture morphology and dimensional parameters on cutting temperature were analyzed. Firstly, tools with micro-textures of five different morphologies were designed near the nose on the rake face of the cemented carbide tools. The three-dimensional cutting models of the micro-textured tools with different morphologies were established by using ABAQUS, and a simulation analysis was carried out. Compared with the non-textured tools, the micro-texture morphology with the lowest cutting temperature was selected according to the simulation results of the cutting temperature. Secondly, based on the optimized morphology, tools with micro-textures of different size parameters were designed. When cutting GH4169, the cutting temperature of the tools was simulated and analyzed, and the size parameters of the micro-textured tools with the lowest cutting temperature were selected as well. Finally, the designed micro-textured tools were processed and applied in cutting experiments. The simulation model was verified in the experiments, and the influence of size parameters of micro-textures on the cutting temperature was analyzed. This paper provides a theoretical reference and basis for cutting GH4169 and the design and application of micro-textured tools.

Turbulent processing of PAHs in protoplanetary discs

Context. Polycyclic aromatic hydrocarbons (PAHs) have been detected in numerous circumstellar discs. Despite the correlation between stellar temperature and low PAH detections rates, the diversity of PAH detections and non-detections at similar stellar properties is not well understood. Aims. We propose the continuous processing of PAHs through clustering, adsorption on dust grains, and their reverse-processes as key mechanisms to reduce the emission-capable PAH abundance in protoplanetary discs. This cycle of processing is driven by vertical turbulence in the disc mixing PAHs between the disc midplane and the photosphere. Methods. We used a theoretical Monte Carlo model for photodesorption in the photosphere and a coagulation code in the disc midplane to estimate the relevance and timescale of these processes in a Herbig Ae/Be disc environment. By combining these components in a 1D vertical model, we calculated the gas-phase depletion of PAHs that stick as clusters on dust grains. Results. Our results show that the clustering of gas-phase PAHs is very efficient, and that clusters with more than 100 monomers can grow for years before they are able to freeze out in the disc midplane. Once a PAH cluster is frozen on the dust grain surface, the large heat capacity of these clusters prevents them from evaporating off the grains in UV-rich environments such as the photosphere. Therefore, the clustering of PAHs followed by freeze-out can lead to a depletion of gas-phase PAHs in protoplanetary discs. We find that this mechanism is more efficient when the PAH species has fewer carbon atoms. In contrast, PAH monomers and very small clusters consisting of a few monomers can easily detach from the grain by absorption of a single UV photon. Evaluated over the lifetime of protoplanetary discs, we find a depletion of PAHs by a factor that ranges between 50 and 1000 compared to the standard ISM abundance of PAHs in the inner disc through turbulent processing. Conclusions. Through these processes, we favour PAHs smaller than circumovalene (C66H20) as the major gas-phase emitters of the disc photosphere as larger PAH monomers cannot photodesorb from the grain surface. These gas-phase PAHs co-exist with large PAH clusters sticking on dust grains. We find a close relation between the amount of PAHs frozen out on dust grains and the dust population, as well as the strength of the vertical turbulence.

A Review of the Configurations, Capabilities, and Cutting-Edge Options for Multistage Solar Stills in Water Desalination

The desalination of saltwater is a viable option to produce freshwater. All the desalination processes are energy-intensive and can be carried out on a large scale. Therefore, producing freshwater using renewable energy sources is the most desirable option considering the current energy crisis and the effect that fossil-fuel-based energy has on our carbon footprint. In this respect, the tray-type still, one of several solar power desalination still varieties, is popular owing to its straightforward design, economic materials of construction, and minimal maintenance requirements, especially in isolated island regions with restricted energy and natural water supplies. The traditional tray-type solar power has a few drawbacks, such as the inability to recover latent heat from condensation, reduced thermal convection, a large heat capacity, and comparatively minimal driving power through evaporation. Therefore, the improvement of heat and mass transfer capabilities in tray-type stills has been the subject of many studies. However, there is a lack of a comprehensive review in the open literature that covers the design and operational details of multistage solar stills. The purpose of this paper is to present a thorough overview of the past research on multistage solar stills, in terms of configurations, capabilities, and cutting-edge options. In comparison to a unit without a salt-blocking formation, the review indicates that a multistage distillation unit may run continuously at high radiation and generate pure water that is around 1.7 times higher than a unit without a salt-blocking formation. The most effective deign is found to be “V”-shaped solar still trays that attach to four-stage stills, since they are less expensive and more economical than the “floor” (Λ-shape) design, which requires two collectors. Additionally, it can be stated that the unit thermal efficiency, solar percentage, and collected solar energy (over the course of a year) increase by 23%, 18%, and 24%, respectively, when the solar collectors are increased by 26% (at the constant inflow velocity of the water).

Thermodynamic investigation of variable‐speed compression unit in near‐isothermal compressed air energy storage

AbstractIsothermal compression is the state‐of‐the‐art in compressed air energy storage (CAES) technology. The study of cyclic pressurization unit in isothermal CAES is carried out in this paper. The unit can continuously compress air utilizing double vessels operating alternately. In each vessel, the large heat capacity of water and spray cooling is applied to establish a conducive environment for the air achieving the effect of efficient near‐isothermal compression. The operating mode of the cyclic pressurization unit is divided into sliding‐pressure operation and constant‐pressure operation according to the pressure of its outlet. By adopting the characteristic curves of pump, the dynamic model is built for the unit in this paper. Further, the differences between the cyclic pressurization unit in isentropic process and in variable‐speed process are quantified and compared in four different cases. In isentropic process, the energy‐saving ratio and exergy efficiency of the unit are expected to reach 20.4% and 95.0%, respectively. In variable‐speed process, the energy‐saving ratio and efficiency of the unit can achieve 7.3% and 73.4%, respectively. This gap is mainly determined by the off‐design performance of the pump. Moreover, the vessel volume should be no less than 3 m3 and 5 m3 when there is spraying and when there is no spraying. Furthermore, spraying favors the improvement of the worsened compression performance caused by the change of design parameters. The energy‐saving ratio can be improved via spraying by 1.3% to 11.0% and 1.8% to 25.6% in the isentropic and variable‐speed processes, respectively. Meanwhile, the exergy efficiency can be increased by 1.5% to 9.4% in the isentropic process and 1.4% to 8.4% in the variable‐speed by spraying.

Exploring electronic, optical, and phononic properties of MgX (X = C, N, and O) monolayers using first principle calculations

The electronic, the thermal, and the optical properties of hexagonal MgX monolayers (where [Formula: see text] = [Formula: see text], [Formula: see text], and [Formula: see text]) are investigated via first principles studies. Ab-initio molecular dynamic, AIMD, simulations using NVT ensembles are performed to check the thermodynamic stability of the monolayers. We find that an MgO monolayer has semiconductor properties with a good thermodynamic stability, while the MgC and the MgN monolayers have metallic characters. The calculated phonon band structures of all the three considered monolayers show no imaginary nonphysical frequencies, thus indicating that they all have excellent dynamic stability. The MgO monolayer has a larger heat capacity then the MgC and the MgN monolayers. The metallic monolayers demonstrate optical response in the IR as a consequence of the metal properties, whereas the semiconducting MgO monolayer demonstrates an active optical response in the near-UV region. The optical response in the near-UV is beneficial for nanoelectronics and photoelectric applications. A semiconducting monolayer is a great choice for thermal management applications since its thermal properties are more attractive than those of the metallic monolayer in terms of heat capacity, which is related to the change in the internal energy of the system.

Long-lasting impact of winter North Atlantic Oscillation on Barents-Kara sea ice anomaly in recent decades

In this paper, the long-lasting impact of the winter North Atlantic Oscillation (NAO) on Arctic sea ice is investigated using reanalysis data, with focus on the Barents–Kara (BK) sea where the air-sea-ice response is closely associated with the interdecadal shift in the northern action center of the NAO. A significant negative correlation between the winter NAO and the late autumn BK sea ice has been dominant since the early 2000s, which is in sharp contrast to the extremely weak correlation before the late 20th century. When the northern center of the NAO retreats westward, a prevailing low-level southerly wind anomaly creates significant positive air temperature anomalies over the BK sea, and the induced ocean current strengthens the northward transport of warm sea water, resulting in a positive BK upper-layer ocean temperature anomaly and a negative sea ice anomaly until early spring. Entering summer, the preexisting less-than-normal sea ice causes the amount of solar shortwave radiation absorbed by the upper-layer sea water to significantly increase and thereby continues to warm up the upper layer of sea water and reduce the sea ice. The warmed sea water enables the negative sea ice anomaly to last until late autumn owing to its relatively large specific heat capacity. Thus, the NAO in the previous winter exerts a long-lasting impact on the BK sea ice.

Ultra-Compact and Efficient Microheaters on a Submicron-Thick InP Membrane

Energy-efficient electro-optic phase shifters have been widely adopted in the InP material system, but their lengths have been in millimeter scales. The strong thermo-optic effect of InP ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$dn/dT = 2.0 \times 10^{-4}\;\text {K}^{-1}$</tex-math></inline-formula> ) can potentially enable compact devices, but it has been hindered by the large heat capacity of the bulky waveguide and inefficient heat transfer to the optical mode. By moving to a sub-micron-thick InP membrane, where the optical modes are more exposed and heat capacity minimized, we report here, to the best of our knowledge, first ultra-compact ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$97\;\mu \text {m}^{2}$</tex-math></inline-formula> footprint), efficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2.26\;\text {mW}/\pi$</tex-math></inline-formula> ) and broadband (100 nm) thermo-optic microheaters in the InP material system. An epitaxially grown layer as part of the waveguide is used as the heating element, enabling maximum heat transfer efficiency. The epitaxial layer structure is designed to be compatible with the membrane photonics platform that includes monolithic amplifiers and lasers. This work could contribute to the further miniturization of monolithic photonic integrated circuits (PIC) that involves phase shifters and amplifiers, and facilitate applications such as optical computing, switching, and sensing.

Real-Time Cell Temperature Fluctuation Monitoring System Using Precision Pt Sensors Coated with Low Thermal Capacity, Low Thermal Resistance, and Self-Assembled Multilayer Films.

Real-time monitoring of cell temperature fluctuation can help researchers better understand physiological phenomena and the effects of drug treatment on cells, which is a novel and important tool for cellular informatics. The platinum (Pt) temperature sensor is widely used in temperature measurement with the advantages of strong stability, great accuracy, and high sensitivity. However, the commercially available Pt sensors have large thermal resistance and heat capacity which are difficult to be applied for cell temperature measurement because only a very small amount of heat flux is generated by live cells. In this study, we designed a system using precision Pt thin-film temperature sensors with low heat capacity and thermal resistance. The Pt thin-film sensors are covered by a silicon nitride insulation layer grafted with a self-assembled multilayer silane film for promoting cell adhesion. The temperature coefficient of resistance of the Pt temperature sensor was about 2100 ppm/°C. The four-wire lead design next to the sensor detection area ensured maximum accuracy, resulting in a system noise below 0.01 °C over a long time. HEK-293T and HeLa cells were cultured on the sensor surface, respectively. The temperature fluctuation of 293T cells was monitored in a cell culture medium, showing a temperature increase of about 0.05-0.12 °C. The temperature fluctuation of HeLa cells treated with cisplatin was also measured and recorded, indicating a temperature decrease of 0.01 °C first and then a gradual temperature increase of 0.04 °C. The Pt sensor system we developed demonstrated high sensitivity and long stability for cell temperature fluctuation monitoring, which can be widely used in cell activity and cellular informatics studies.

입자가속기용 초전도 코일 개발을 위한 절연설계법 개발

High-temperature superconductor (HTS) can be applied to manufacture superconducting coils for particle accelerators. Since HTS has a larger heat capacity than low-temperature superconductor (LTS), HTS is suitable for developing particle accelerators with fast ramp-up rate. A superconducting coil using HTS can be miniaturized with a fast ramp-up rate, thereby obtaining economic benefits such as reduction in maintenance and repair costs. High electric field intensity may be induced at a superconducting coil such as a saddle coil for medical accelerators owing to its complex structure. It is known that the dielectric performance of electrode systems can be poor in the medium vacuum range. In this study, dielectric experiments for establishing empirical formula to design a reliable HTS coil against fast ramp-up rate in various vacuum conditions were performed. As a result, empirical formula to design an electrically stable HTS coil were deduced through dielectric experiments with various conditions considering pressure, electrode size, and gap between electrodes.