Rapid Phase Change Research Articles

Geological and Engineering Integration Fracturing Design and Optimization Study of Liushagang Formation in Weixinan Sag

The Weixinan Sag in the Beibuwan Basin is rich in shale oil resources. However, the reservoirs exhibit rapid phase changes, strong compartmentalization, thin individual layers, and high-frequency vertical variations in the thin interbedded sandstone and mudstone. These factors can restrict the height of hydraulic fracture propagation. Additionally, the low-porosity and low-permeability shale oil reservoirs face challenges such as low production rates and rapid decline. To address these issues, the Plannar3D full 3D fracturing model was used to simulate hydraulic fracture propagation and to study the main controlling factors for fracture propagation in the second member of the Liushagang Formation. Based on the concept of geological–engineering integration, a sweet spot evaluation was conducted to identify reservoirs with relatively better brittleness, reservoir properties, and oil content as the fracturing targets for horizontal wells. The UFM model was then applied to optimize fracturing parameters. This study indicates that the matrix-type oil shale has a high clay mineral content, resulting in a low Young’s modulus and poor brittleness. This makes hydraulic fracture propagation difficult and leads to less effective reservoir stimulation. In contrast, hydraulic fractures propagate more easily in high-brittleness interlayer-type oil shale. Therefore, it is recommended to prioritize the extraction of shale oil from interlayer-type oil shale reservoirs. The difference in interlayer stress is identified as the primary controlling factor for cross-layer fracture propagation in the study area. Based on the concept of geological–engineering integration, a sweet spot evaluation standard was established for the second member of the Liushagang Formation, considering both reservoir quality and engineering quality. Four sweet spot zones of interlayer-type oil shale reservoirs were identified according to this evaluation standard. To achieve uniform fracture initiation, a differentiated segment and cluster design was implemented for certain high-angle sections of well WZ11-6-5d. Interlayer-type oil shale was selected as the fracturing target, and the UFM was used for hydraulic fracture propagation simulation. Fracturing parameters were optimized with a focus on hydraulic fracture characteristics and the estimated ultimate recovery (EUR). The optimization results were as follows: a single-stage length of 50 m, cluster spacing of 15 m, pump injection rate of 10 m3/min, fluid intensity of 25 m3/m, and proppant intensity of 3.5 t/m. The application of these optimized fracturing parameters in field operations resulted in successful fracturing and the achievement of industrial oil flow.

Acoustic flow resonances in installed rectangular jets

Zonal Large Eddy Simulations (LES) of complex installed rectangular jet flows are performed for subsonic jet conditions of the Central Institute for Aviation Motors (CIAM) experiment, where a strong tone was reported. For far-field noise modelling, the zonal LES solutions are coupled with the permeable formulation of the Ffowcs Williams and Hawkings (FW-H) method. The obtained noise spectra predictions are compared with the acoustic measurements in the CIAM facility. To reduce statistical noise of the relatively short LES time series, contributions due to several dominant low frequency tones and the remaining broadband signal are computed separately, using a tailored Fourier transform technique for each signal type. For cross-validation, noise spectra measurements of an equivalent isolated round jet in the CIAM facility are compared with the empirical sJet model calibrated on the NASA Small Hot Jet Acoustic Rig (SHJAR) jet noise database. While the two datasets agree reasonably well for mid to high frequencies, larger discrepancies are observed for low frequencies, which are attributed to acoustic reflections in the non-anechoic CIAM facility. The differences in noise levels between the CIAM dataset and the sJet model representing the NASA jet noise data are used to determine the experimental uncertainty of the CIAM noise measurements for each frequency and observer angle. For the installed rectangular jet, it is shown that far-field noise spectra predictions of the zonal LES-FW-H method for both the fundamental tone, its sixth harmonic corresponding to the jet Strouhal number of around 1, and the broadband component are broadly within the experimental error bar for most observer angles. Some discrepancies between predictions of the zonal LES method and the CIAM measurements for the main low frequency tone for the 30o and 90o, where the experimental uncertainty at low frequencies is largest are also noted. After validating the acoustic solutions, spectral and conditional averaging analysis methods are applied to elucidate mechanisms of the acoustic-flow resonance in the installed rectangular jet flow. The numerical dispersion relation is obtained to analyse phase velocities of the upstream and downstream travelling pressure waves in the stream-wise direction. The conditional analysis of pressure fluctuations inside the jet reveals the emergence of internal reflection points corresponding to a rapid change of the acoustic wave phase as well as the saddle points interpreted as localised zones of vorticity shed from the side-wall edges. To independently investigate the effect of trailing edges and corner points of the jet embodiment geometry on closing the acoustic-flow resonance cycle, several modifications of the baseline rectangular nozzle are considered, such as introducing chevron-like lobes and cuts on the trailing edges of the side walls as well as smoothing the sharp corner points of the wall edges. Following the series of additional zonal LES runs with the modified installed nozzle geometries, an optimized tone-less modification of the original installed nozzle was obtained, in broad agreement with the conditional analysis results. The obtained tone-less modification of the installed rectangular jet is further analyzed to provide insights into its similarity and differences from the aeroacoustics of the reference isolated round jet in the same CIAM facility.

Investigation of CO2 Rapid Phase Change Absorbent System Based on Amino Acid Salts and Ether Solvents

Investigation of CO₂ Rapid Phase Change Absorbent System Based on Amino Acid Salts and Ether Solvents

Lamotrigine: A Safe and Effective Mood Stabilizer for Bipolar Disorder in Reproductive-Age Adults.

Lamotrigine belongs to the group of antiepileptic drugs and mood stabilizers, and its action is based on the selective blocking of voltage-deficient sodium channels. The effect of this mechanism is the stabilization of the presynaptic part of the neuronal membrane and subsequent inhibition of the secretion of the neurotransmitters glutamate and aspartate into the postsynaptic part of the neuron. Lamotrigine has been approved by the Food and Drug Administration for the maintenance treatment of adults with bipolar disorder since 1994. In the field of psychiatry, this medicine is also used off-label in the treatment of acute bipolar depression. Studies show promising effects of the use of lamotrigine in bipolar disorder type II with rapid phase change. Bipolar disorder is a common psychiatric problem that most often affects young adults. Lamotrigine is most effective in bipolar disorder in preventing depressive episodes, which dominate the clinical picture of this disease. The latest research focuses on extending its action, to include manic episodes. Lamotrigine, through an unexplained mechanism, can affect the immune system, causing Stevens-Johnson syndrome, hemophagocytic lymphohistiocytosis, and drug reaction with eosinophilia and systemic symptoms syndrome. These are rare, life-threatening adverse effects that require urgent intervention in the form of drug discontinuation and immunosuppressive treatment. Strict contraindications to the use of lamotrigine include sensitivity reactions accompanied by systemic symptoms. Phenotype testing enables screening of patients predisposed to serious hypersensitivity reactions. The aim of the article is to review the indications, contraindications, and adverse effects of lamotrigine in the treatment of bipolar disorder and depression.

Research advances on the mechanisms of reservoir formation and hydrocarbon accumulation and the oil and gas development methods of deep and ultra-deep marine carbonates

Based on the new data of drilling, seismic, logging, test and experiments, the key scientific problems in reservoir formation, hydrocarbon accumulation and efficient oil and gas development methods of deep and ultra-deep marine carbonate strata in the central and western superimposed basin in China have been continuously studied. (1) The fault-controlled carbonate reservoir and the ancient dolomite reservoir are two important types of reservoirs in the deep and ultra-deep marine carbonates. According to the formation origin, the large-scale fault-controlled reservoir can be further divided into three types: fracture-cavity reservoir formed by tectonic rupture, fault and fluid-controlled reservoir, and shoal and mound reservoir modified by fault and fluid. The Sinian microbial dolomites are developed in the aragonite-dolomite sea. The predominant mound-shoal facies, early dolomitization and dissolution, acidic fluid environment, anhydrite capping and overpressure are the key factors for the formation and preservation of high-quality dolomite reservoirs. (2) The organic-rich shale of the marine carbonate strata in the superimposed basins of central and western China are mainly developed in the sedimentary environments of deep-water shelf of passive continental margin and carbonate ramp. The tectonic-thermal system is the important factor controlling the hydrocarbon phase in deep and ultra-deep reservoirs, and the reformed dynamic field controls oil and gas accumulation and distribution in deep and ultra-deep marine carbonates. (3) During the development of high-sulfur gas fields such as Puguang, sulfur precipitation blocks the wellbore. The application of sulfur solvent combined with coiled tubing has a significant effect on removing sulfur blockage. The integrated technology of dual-medium modeling and numerical simulation based on sedimentary simulation can accurately characterize the spatial distribution and changes of the water invasion front. Afterward, water control strategies for the entire life cycle of gas wells are proposed, including flow rate management, water drainage and plugging. (4) In the development of ultra-deep fault-controlled fractured-cavity reservoirs, well production declines rapidly due to the permeability reduction, which is a consequence of reservoir stress-sensitivity. The rapid phase change in condensate gas reservoir and pressure decline significantly affect the recovery of condensate oil. Innovative development methods such as gravity drive through water and natural gas injection, and natural gas drive through top injection and bottom production for ultra-deep fault-controlled condensate gas reservoirs are proposed. By adopting the hierarchical geological modeling and the fluid-solid-thermal coupled numerical simulation, the accuracy of producing performance prediction in oil and gas reservoirs has been effectively improved.

Effect of ethanol/n-hexane blending ratio on behaviors of shock waves in flash-boiling jets

The rapid phase change of flash boiling jets would induce shock waves, but there is a lack of investigations on how the component blending ratios influence the characteristics of such shock waves. In this study, ethanol/n-hexane blends with different blending ratios were used to investigate this sort of shock waves using high-speed microscopic Schlieren photography. The tests were carried out in a constant volume vessel under varying ambient pressures (Pamb) and liquid temperatures (Tliquid). The shock size was carefully examined in terms of length and width. For all the test blends, both increasing Tliquid and decreasing Pamb could enlarge the shock length and width, but with different increments. Furthermore, with the increase in ethanol blending ratio, monotonic decrease in shock length and non-monotonic change in shock width were found, which can be attributed to the change in hydrogen bond concentration, which alters the axial distribution of evaporation intensity. The evaporation for the liquids with high ethanol blending ratios (>20 %) was weakened in contrast to that of pure n-hexane due to the existence of hydrogen bonds, causing the smaller shock size. At the low ethanol blending ratios (10 % & 20 %), the hydrogen bonds within ethanol were diluted and destroyed by n-hexane, enhancing the escape of ethanol from the blends. Thus, in contrast to the evaporation of pure n-hexane, the evaporation for the liquids with low ethanol was stronger, and the excessive energy due to the sudden pressure drop was released more rapidly at the nozzle exit. The former caused the increase in shock width, and the latter led to the shorter shock length. Finally, a good correlation was proposed between shock size and ΔG·Pamb-0.5(ΔG denoting the Gibbs energy difference during phase change).

Computational Evaluation of Pulsating Heat Pipe for Fluid Flow Behavior and its Thermal Performance

Computational fluid analysis of a single circuit heat pipe was undertaken to ascertain the thermal efficiency of water at various fill ratios, specifically 40%, 50%, and 60% under varying heating conditions. The analysis employed the ANSYS Fluent computational fluid dynamics software, utilizing a k-epsilon to the heat pipe as the solver. The analysis was carried out on a copper tube with an internal diameter measuring 3/16 inches. During the analysis, the thermal inflow at the adiabatic region was adjusted to zero, while the condenser region’s temperature remained constant at 25°C. Meanwhile, the heat input at the evaporator region was systematically adjusted to 105°C, 110°C, 115°C, and 120°C. Key Performance characteristics of heat pipe i.e. thermal resistance, and water volume fraction were evaluated during analysis. The temperature variations noted in both regions affirmed that the pulsating pipe’s performance was influenced by the phase transition between liquid and vapor. Furthermore, the concentration of volume within the evaporator section was monitored, confirming the presence of a dual-phase phenomenon within the heat pipe. Through the analysis, it was noted that the thermal resistance of the water is minimized at a 50% fill ratio for each level of heat input. Notably, the promising results were obtained at an input temperature of 120°C with a value of 1.025°C /W which was 7.3% and 9.8% lower than thermal resistance at 40% and 60% fill ratios, respectively. The reduced thermal resistance in this scenario is attributed to the flow dynamics within the capillary, propelled by rapid phase change mechanisms. This shows the importance of Pulsating Heat Pipes (PHPs) in thermal control, as well as the intricacies of their operating mechanisms. Experimental and theoretical investigations have investigated numerous elements influencing PHP performance, with numerical modeling providing insight into thermal resistance and water volume fraction dynamics under varying heating temperatures and fill ratios.

Numerical Simulation of Rapid Heat Storage in Plate-Fin Phase Change Heat Exchanger

Rapid phase change heat storage has significant application value in high-power density thermal management systems. This paper presents a comparative numerical simulation study of the rapid heat storage and release dynamics of two types of finned plate heat exchangers with different fin shapes. The study reveals that, under the same fin thickness and volume fraction, the contact surface area of triangular fins is 1.6 times that of rectangular fins, but the heat storage rate of triangular fin heat exchangers is 2 times that of rectangular fin heat exchangers. Due to the small characteristic scale and high material viscosity of the heat exchanger, the natural convection velocity of the liquid phase during the heat storage process is low, and its influence on enhancing the heat storage rate is weak.

A deep learning computational fluid dynamics solver for simulating liquid hydrogen jets

Modeling and simulating the sudden depressurization of liquids inside nozzles is a significant challenge because of the plethora of the associated complex phenomena. This pressure drop together with the rapid phase change of the liquid is important characteristics of flash boiling. Computational fluid dynamics (CFD) multiscale simulations of flashing jets usually deploy additional models for modeling heat and mass transfer with long computational times. Intermediate steps such as volumetric meshing in mesh-based methods can also significantly increase the computational cost. This paper aims at providing academia and industry with a modeling tool to simulate and investigate the complex multi-facet phenomenon of flash-boiling atomization deploying a machine-learning method that could save thousand Central Processing Unit hours offering instantaneous CFD predictions. The presented machine-learning CFD method completely replaces the traditional CFD simulations workflow and requires little simulation expertise from the end-user. Notably, this is a novel model that couples for the first time the thermodynamic non-equilibrium with convolutional neural networks to simulate flashing liquid hydrogen jets thousand times faster than the standalone CFD solver. The accuracy of the novel approach is evaluated, demonstrating adequate accuracy compared to different unseen simulations and experiments. This work offers the groundwork for further accelerating CFD predictions in multiphase flow problems and could significantly improve testing flash-boiling scenarios in various industrial settings.

Multidecadal Phase Changes in the Thermodynamic State of the System: Ocean–Atmosphere–Continent

The present-day climate (the recent 100–150 years) obviously constitutes the structure of a global intra-system rhythmic process with an individual rhythm of about 60 years. In turn, each of the rhythms is presented by the two climate phases of about 25–35 years characterized by qualitative differences: one phase is relatively continental, while the other is humid. Globality and quasi-synchronism of environmental changes are accompanied by planetary structures: the Global Atmospheric Oscillation (GAO) in the atmosphere and the Multidecadal Oscillation of the Heat content in the Ocean (MOHO) discovered relatively recently. Unexpected and rapid qualitative phase changes in the climate, which first focused attention in the mid-1970s of the last century, were titled “climate shifts”. The revealed features of the present-day climate are of exceptional scientific and practical interest and deserve the development of methods for predicting the timing of the forthcoming climate shift. Arising unexpectedly and accompanied by rapid significant changes, these shifts identified the problem of understanding the nature and establishing the processes and mechanisms causing them. First of all, of interest are phase changes in the thermodynamic state of the climate system components: the ocean, atmosphere, and continents. As a result of the World Ocean (WO) thermohydrodynamics numerical modelling, it is shown that MOHO is localized in the layer of the main thermocline, where the most important elements of the WO circulation are located. The performed study based on observational data allows us to conclude that, during the phase of the WO thermal discharge (1975–1999), the two key systems of currents, the Kuroshio and the Gulf Stream, were under similar thermodynamic conditions.

Controlling double optomechanically induced transparency and slow/fast light in an electro-optomechanical system via an optical parametric amplifier

We investigate tunable double optomechanically induced transparency and slow/fast phenomena in a hybrid electro-optomechanical system. The hybrid system consists of an optical cavity with an optical parametric amplifier (OPA) and two charged mechanical resonators. The double optomechanical induce transparency can be exhibited by manipulating the coupling parameters of the electro-optomechanical system. Specifically, the number of transparent points and the width of transparent windows increase with an increase in the coupling constant. Furthermore, the phenomenon of double transparency is strongly influenced by the parametric gain of OPA and by the Coulomb interaction between the two mechanical oscillators. It is found that the larger parametric gain and Coulomb coupling induce an increasing width of transparency windows. Moreover, we study the slow/fast light effect associated with the rapid phase change of the transmission of probe field. Our approach provides a great flexibility for controlling double induced transparency, and has potential applications in optical information storage and optical communication.

A theoretical model on unfrozen water content in soils and verification

Phase transition of pore water is a fundamental reason for frost heave in cold regions. Therefore, studying the variation in unfrozen water content is of great significance for understanding the freezing process of pore water and revealing the freezing mechanism in soils. In this study, a prediction model for unfrozen water content was established based on a probabilistic ice-forming model. To determine the heterogeneous nucleation rate, which is the key variation in the probabilistic model, the relationship between the water film thickness and temperature variation in the soil was characterized based on the improved premelting theory. In this process, the equivalent particle size and density of impurities on the surface of the particles were determined by introducing the particle size distribution curve and average accumulation mode of the particles. Based on the heterogeneous nucleation mechanism of ice crystals and the variation in the water film, a relationship between the heterogeneous nucleation rate and temperature was established. Subsequently, a method for calculating the equivalent contact angle related to pore water in soils was presented. The results showed that the heterogeneous nucleation rate and equivalent contact angle are positively and negatively correlated with the equivalent particle size at the same temperature, respectively, and the angle decreases with increasing solution concentration. Furthermore, the experimental data of 10 different soils showed that the variation in water content obtained by our model was in good agreement with the experimental values, particularly during the stage of rapid water phase change. The study developed an effective correlation among heterogeneous nucleation rate and equivalent contact angle of pore water and physical properties of soil, by combining crystallization theory and premelting theory, which provided a new way to explain water freezing and predict unfrozen water content in soils.

3D-printing of selectively porous, freestanding structures via humidity-induced rapid phase change

3D-printing of selectively porous, freestanding structures via humidity-induced rapid phase change

Evaluation of the rapid phase change absorbents based on potassium glycinate for CO2 capture

Phase-change process is deemed as an energy-saving approach for CO2 capture, however, the low phase change rate of the current absorbents leads to low separation efficiency, difficult operation and solvent loss. Herein, a novel rapid phase change absorbent composed of ether solvent (SA) and potassium glycinate (GlyK) aqueous solution was developed, and the phase-change behavior, phase separation mechanism, and the energy consumption were investigated. Results showed that the GlyK-30SA absorbent exhibited the highest CO2 capacity of 0.64 molCO2/molGlyK, the liquid-liquid phase separation within 2 min and more than 91% CO2 enrichment in the lower phase. The mechanism of the split phase and regeneration was explored by 13C NMR. More significantly, the absorbent also showed excellent cycling stability and a 30% reduction in energy consumption compared to the 3 M MEA system. It provided a new possibility for the development of stable and energy-saving amino acid salts phase change absorbents.

New 3D phase-unwrapping method based on voxel clustering and local polynomial modeling: application to quantitative susceptibility mapping.

To develop an accurate and robust 3-dimensional (3D) phase-unwrapping method that works effectively in the presence of severe noise, disconnected regions, rapid phase changes, and open-ended lines for quantitative susceptibility mapping (QSM). We developed a 3D phase-unwrapping method based on voxel clustering and local polynomial modeling named CLOSE3D, which firstly explores the 26-neighborhood to calculate local variation of the phasor and the phase, and then according to the local variation of the phasor, clusters the phase data into easy-to-unwrap blocks and difficult-to-unwrap residual voxels. Next, CLOSE3D sequentially performs intrablock, interblock, and residual-voxel unwrapping by using the region-growing local polynomial modeling method. CLOSED3D was evaluated in simulation and using in vivo brain QSM data, and was compared with classical region-growing and region-expanding labeling for unwrapping estimates methods. The simulation experiments showed that CLOSE3D achieved accurate phase-unwrapping results with a mean error ratio <0.39%, even in the presence of serious noise, disconnected regions, and rapid phase changes. The error ratios of region-growing (P=0.000 and P=0.000) and region-expanding labeling for unwrapping estimates (P=0.007, P=0.014) methods were both significantly higher than that of CLOSE3D, when the noise level was ≥60%. The results of the in vivo brain QSM experiments showed that CLOSE3D unwrapped the phase data and accurately reconstructed quantitative susceptibility data, even with serious noise, rapid-varying phase, or an open-ended cutline. CLOSE3D achieves phase unwrapping with high accuracy and robustness, which will help phase-related 3D magnetic resonance imaging (MRI) applications such as QSM and susceptibility weighted imaging.

Feedforward Control Strategies for Rapid Phase Adjustment of Superconducting Cavities

Rapidly adjusting (or scanning) the phase of a superconducting radio-frequency (SRF) cavity (on a millisecond or sub-millisecond time-scale) under closed-loop control is crucial in various applications of many SRF facilities. However, the transient dynamic response of the feedback (FB) control loop is usually unsatisfactory (e.g., the cavity field amplitude is seriously disturbed) during the phase adjustment process because of the restricted closed-loop bandwidth and limited power budgets. Herein, we proposed a feedforward (FF) control strategy derived from a cavity differential equation to accelerate the control loop’s regulation process, thereby improving the system’s dynamic behavior. We demonstrated the validity of the FF-based strategy in the Chinese ADS Front-end (CAFe) proton facility demo SRF linac. The preliminary results showed that the combined FF+FB control strategy significantly improved the dynamic performance compared to the FB individual control. This study provides the basis for the FF scheme validation and may serve as a reference for applications requiring rapid SRF cavity phase change.

Analysis of Ionospheric Scintillations Measurement on NavIC Signals

Ionospheric scintillation is a rapid change in amplitude and phase of an electromagnetic signal in the ionospheric environment. Amplitude scintillations indicated by S4 index and phase scintillations by. Low latitude regions are prone to ionosphere scintillation. Since India is a low latitude region, ionospheric scintillations must be analysed. Indian NavIC or IRNSS planned and implemented by the Indian Space Research Organization (ISRO). In this paper S4 index is investigated for NavIC L5 (1.17645 GHz) and S1 (2.492028 GHz) signals (1B,1C,1D,1E,1F,1G). For the analysis Guntur station (Lat:16.44N, Lon:80.62E) and Hyderabad station (Lat:17°24’28.10″N, Lon: 78°31′4.22″E) IGS receiver data is considered. The S4 index is calculated using carrier to noise ratio of IRNSS L5 and S band signals. From the results it is observed that S4 index is more for L5 band signals compared to S band signals, as ionospheric scintillations are frequency dependent. Guntur station S4 average value is low for all (L5 and S) band satellite signals compared to Hyderabad station satellite signals. Over Indian region, it shows latitude-dependent scintillations.

Numerical modelling of in-situ alloying of Al and Cu using the laser powder bed fusion process: A study on the effect of energy density and remelting on deposited track homogeneity

In-situ alloying using laser powder bed fusion (LPBF) allows for formation of new alloys and complicated components with spatially controlled characteristics. A major issue in in-situ alloying is the macro-segregation of alloying elements, that results in chemical inhomogeneity. The precise control of composition is one of the most important steps in any effective in-situ alloying process. In this study, a mesoscale computational fluid dynamics (CFD) model for simulating single-tracks is developed to advance the in-depth understanding of in-situ alloying of dissimilar metals. Surface tension and recoil pressure driven flows at the free surface, rapid phase change, laser reflections, and other physical phenomena affecting the LPBF process have all been examined. Species conservation is used to trace the mixing of different metals. Simulations are performed by melting a layer of Al powder on a Cu substrate, and the impact of recoil pressure and Marangoni convection driven flows on Al-Cu mixing was addressed. The homogeneity of the simulated track is quantified by defining a mixing index. The effect of different laser energy densities and remelting on the homogeneity of the deposited track is investigated. Numerically, it was observed that the high thermal conductivity of both metals results in a sharp and short melt pool, and rapid solidification of such a melt pool generates a heterogeneous concentration dispersion. At high energy density, a low mixing index value is observed, indicating improved homogeneity in the deposited track. Furthermore, remelted tracks have a low mixing index value, indicating that remelting is an effective strategy for improving homogeneity. This study provides fundamental insights on the mixing of dissimilar metals and aims to support future research activities on the design and development of new alloys using LPBF process.

Assessment of photoreceptor function with ultrafast retinal densitometry.

The optical density of visual pigment can be measured by imaging the dark-adapted eye while bleaching with visible light. This measurement can be made for individual photoreceptor cells using adaptive optics; however, activation of the phototransduction cascade imparts rapid changes in phase that modulate the signal via optical interference. This limits utility because data must be averaged over many experimental runs. Here we used a "flood" illuminated adaptive optics system at 4000 fps, bright light to achieve rapid bleaching, and broad illumination bandwidth to mitigate interference effects. Data were super-resolved using the natural motion of the eye to overcome the reduced pixel resolution of the ultrafast camera. This approach was applied to classify the trichromatic cone photoreceptor mosaic at a single fixation locus within the foveal region of 3 healthy subjects. Subjects were dark adapted for 6 minutes to replenish cone photopigment. This was followed either directly by imaging at 555 ± 50 nm, or by first pre-adapting the retina to 700 nm light to preferentially deplete "L" cone pigment. A total of 3,252 cones were classified as either "S", "M", or "L" type based on clustering of the intensity data observed under these two conditions. Mean classification probability ranged from 99.3 to 99.8%, with individual cell probabilities exceeding 95% in 97.0 to 99.2% of cones. Accuracy of cone classification peaked when using the first 10-30 ms of data, with significant reductions in accuracy noted with the inclusion of data from later times. Our results show that rapid bleaching and data acquisition significantly improve the robustness of cell-resolved densitometry.

A Rapid Thermal Absorption Rate and High Latent Heat Enthalpy Phase Change Fiber Derived from Bio-Based Low Melting Point Copolyesters.

A series of poly(butylene adipate-co-hexamethylene adipate) (PBHA) copolymers with different content of 1,4-cyclohexanedimethanol (CHDM) was synthesized via one-step melt polymerization. The PBHA copolymer with 5 mol% CHDM (PBHA-C5) exhibited a low melting point (Tm) and high enthalpy of fusion (∆Hm) of 35.7 °C and 43.9 J g−1, respectively, making it a potential candidate for an ambient temperature adjustment textile phase change material (PCM). Polybutylene terephthalate (PBT) was selected as the matrix and blended at different weight ratios of PBHA-C5, and the blended samples showed comparable Tm and ∆Hm after three cycles of cooling and reheating, indicating good maintenance of their phase changing ability. Samples were then processed via melt spinning with a take-up speed of 200 m min−1 at draw ratios (DR) of 1.0 to 3.0 at 50 °C. The fiber’s mechanical strength could be enhanced to 2.35 g den−1 by increasing the DR and lowering the PBHA-C5 content. Infrared thermography showed that a significant difference of more than 5 °C between PBT and other samples was achieved within 1 min of heating, indicating the ability of PBHA-C5 to adjust the temperature. After heating for 30 min, the temperatures of neat PBT, blended samples with 27, 30, and 33 wt% PBHA-C5, and neat PBHA-C5 were 53.8, 50.2, 48.3, 47.2, and 46.5 °C, respectively, and reached an equilibrium state, confirming the temperature adjustment ability of PBHA-C5 and suggesting that it can be utilized in thermoregulating applications.