Light Transmission Measurements Research Articles

Correlation between transcutaneous bilirubin levels and total serum bilirubin levels in postnatal period in a tertiary care center

Background: Neonatal jaundice is generally a benign condition seen during the postnatal period. The non-invasive methods including transcutaneous bilirubinometry have been developed for assessment of neonatal jaundice, transcutaneous bilirubin TcB) meters noninvasively estimate the bilirubin levels by measuring light transmission through the skin of neonates this value is then to be plotted against a chart in order to look for hyperbilirubinemia. Aim was to determine the efficacy of measuring the transcutaneous bilirubin as a screening tool for clinically significant hyperbilirubinemia. Methods: Study was a cross sectional study conducted under pediatric department of SMBT IMS and RC at tertiary care center after taking the approval from the ethical committee. Total of 110 neonates that appear to be clinically suffering from neonatal jaundice were considered for study after consent from respective parent/ guardian. Neonatal TCB levels and serum bilirubin levels were done. If bilirubin levels lie in phototherapy range, then baby was shifted to NICU and phototherapy treatment was given, and once levels came within normal range after the phototherapy treatment, again serum bilirubin levels were measured in order to compare pre-and post-treatment levels. Results: Present study showed male preponderance. 64 were male and 46 were female. Majority 61% were full term normal delivery and 39% were LSCS. Mean TCB level was 8.5±2.8. Statistical significance was seen for TCB and sever hyperbilirubinemia. Conclusions: Present study concluded that hyperbilirubinemia is commonly seen among males. Newborn delivered had hyperbilirubinemia. Statistical significance was seen between TCB level and severity of the disease. Thus, neonatal TCB levels can be used as a screening test for detecting hyperbilirubinemia in neonates. As TCB is a noninvasive and cost effective it can be used widely as predictor of the disease.

Platelet Functional Testing Via High-Throughput Microtiter Plate-Based Assays.

Platelets play a critical role in hemostasis and thrombosis; therefore, in vitro assays that measure platelet reactivity are fundamental tools to gain insight into these physiologic processes, to diagnose platelet disorders, and to develop antithrombotic therapies. However, conventional platelet assays such as aggregometry, the clinical gold standard for assessing platelet function, are low throughput and require specialized equipment. Since platelets have a finite life span ex vivo, processes to miniaturize and multiplex assays allow a much broader overview of platelet function in significantly less time than conventional assays. Several groups have developed simplified, high-throughput approaches to quantify platelet activation with standard laboratory equipment to lower the barrier of entry to study platelet biology. This article describes a panel of optimized and validated high-throughput microplate assays to comprehensively assess platelet functionality, independently or in combination, to increase throughput and reduce costs. Specifically, following stimulation of platelets, a plate reader can be used to measure light transmission aggregation via absorbance; dense-granule secretion based on ATP-dependent luminescence generation; and cytosolic calcium levels with a cell-permeant, fluorescent Ca2+ -sensitive dye. Additionally, platelets are an easily accessible component of the blood that share signaling pathways with other cells, making them ideal for high-throughput drug screens. The highly adaptable and complementary assays presented in this article can be used to decipher the molecular mechanism underlying platelet activation or to identify novel inhibitors. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Microtiter plate-based light transmission aggregometry Basic Protocol 2: Measuring dense-granule secretion in high-throughput microplate assays Basic Protocol 3: Microtiter plate-based calcium mobilization Support Protocol: Platelet isolation and enumeration.

Influence of Goethite Nanorods on Structural Changes and Transitions in Nematic Liquid Crystal E7

A composite ferronematic system based on the nematic liquid crystal E7, doped with lath-like goethite magnetic nanoparticles of volume concentrations 10−3, 5 × 10−4, and 10−5, was investigated. Both surface acoustic waves (SAWs) and the magneto-optical effect were used to study the influence of magnetic nanoparticles on ferronematic liquid crystals’ structural changes, focused above all on structural transitions. The responses of SAW attenuation and light transmission to external magnetic fields were investigated experimentally under linearly increasing/decreasing or jumped (time influence) magnetic fields, respectively. An investigation of temperature on structural changes was performed, as well. The experimental results validated the decrease in the threshold field of the ferronematic composites in comparison with the pure E7, as well as an increase in the transition temperature with the increasing volume fraction of nanoparticles. The effect of the nanoparticles’ concentration on both total structural changes and residual attenuations at the vanishing magnetic field was also registered. The light transmission measurements confirmed the effect of the concentration of goethite nanoparticles on the resultant magneto-optical behavior, concerning both its stability and switching time.

DEVELOPMENT OF RADIATION RESISTANT SCINTILLATORS BASED ON RARE-EARTH ALUMINATES

LuYAG:Ce and YAG:Ce,Ca crystals were obtained by the Czochralski method using tungsten crucibles in reducing surroundings. Crystals (LuxY1-x)3Al5O12:1%Ce and crystals of YAG:Ce,Ca with different concentrations of Ce and Ca were grown. Studies and analyses of their characteristics were carried out. The analysis of their characteristics is based on experimental data that we obtained by measurements of light output, decay time, spectra of luminescence, excitation, and light transmittance.

The Effect of Surface Characteristics of Clays on the Properties of Starch Nanocomposites.

In this research, different clays such as laponite and montmorillonite (NaMMT) are used as fillers in the preparation of thermoplastic starch/clay nanocomposites. Thin films are produced by casting and evaporation in a wide composition range, using glycerol as the plasticizer at two different concentrations. The surface energy of clay fillers is measured by inverse gas chromatography (IGC); X-ray diffraction (XRD) and light transmission measurements (UV-VIS) are carried out to characterize the structure of nanocomposites; and mechanical properties and water vapor permeability are also studied. While all the starch/montmorillonite nanocomposites possess intercalated structures, significant exfoliation can be noted in the starch/laponite nanocomposites, mainly at low clay contents. Due to the larger surface energy of montmorillonite, stronger polymer/clay interactions and better mechanical properties can be assumed in starch/NaMMT composites. The smaller surface energy of laponite, however, can facilitate the delamination of laponite layers. Thus, the specific surface area of laponite can be further increased by exfoliation. Based on the results, the better exfoliation and the much larger specific surface area of laponite lead to higher reinforcement in starch/laponite nanocomposites.

Glycerol methacrylate-based copolymers: Reactivity ratios, physicochemical characterization and cytotoxicity

Understanding the chemical composition of biocompatible copolymers is crucial for diverse biomedical applications such as the conjugation of polymers to drugs, peptides or proteins. Here, we report the Reversible Addition-Fragmentation Chain Transfer (RAFT) copolymerizations and reactivity ratios (r) of the less explored biocompatible copolymer systems based on glycerol mono-methacrylate (GMMA) monomer. Hence, we investigated the copolymerization of GMMA with the comonomers N-hydroxy succinimide methacrylate (NHSMA), N-isopropylacrylamide (NIPAM) and butyl acrylate (BuA). The estimated r values and sequence length distributions suggest that a chain radical of GMMA monomer prefers cross propagation in the system GMMA/NHSMA (rGMMA = 0.32 rNHSMA = 1.01). In the case of GMMA/NIPAM (rGMMA = 2.55 rNIPAM = 0.11) and GMMA/BuA (rGMMA = 3.31 rBuA = 0.66) systems, as shown by the relatively high rGMMA values in both copolymerizations, the formation of gradient copolymers might be favored. To understand the role of the comonomer composition in the thermal and solution properties of the final materials, the glass transition temperature (Tg) values of the copolymers, as determined by differential scanning calorimetry (DSC), were compared to build Tgvs. composition plots generated with the Fox, Brostow and Kwei equations. DSC investigations also revealed an interesting effect of molecular interactions between the polymer chains possibly formed via hydrogen bonding conveyed by the GMMA groups in the copolymers. Furthermore, light transmittance measurements of the poly(GMMA-stat-NIPAM) copolymer system in aqueous solutions revealed that the cloud point temperature (Tcp) of the solutions increases with the content of GMMA groups in the copolymer; however, this behavior was limited by the NIPAM composition (>0.74 mol fraction). Interestingly, a copolymer material with a GMMA/NIPAM composition (FGMMA/FNIPAM) of 26/74 exhibited a TCP = 38 °C, which is close to the human body temperature. Finally, cytotoxicity assays indicated the excellent biocompatibility of the obtained copolymers, which suggests that these copolymer systems might be suitable alternatives for bioconjugated systems in biomedical applications.

Thermal dewetting as a method of surface modification of the gold thin films for surface plasmon resonance based sensor applications

Here, we report a quick and simple approach with low, optimized production costs to obtain surface plasmon resonance (SPR) based sensors fabricated through a time- and resource-effective method based on thermal dewetting of thin Au films. From the applicative point of view, the method of detection presented here should be easier to implement, since light transmission measurements seems to be much less challenging than light refractive index changes measurements conducted by many authors. Metallic films with nanometric thickness were deposited by magnetron sputtering method on a Corning 1737 glass substrates. Plasmonic nanostructures were formatted as a result of thermal annealing of the films. The detection repeatability, selectivity, and sensibility of manufactured devices were investigated. For this purpose, many verification tests were performed. The quality of the plasmonic nanostructures used for the detection was examined by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and ultraviolet-visible spectroscopy (UV–VIS). X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) spectra showed the absence of any signs of structure degradation after several cycles of detection in the liquid environment. The surface plasmon resonance position of the achieved sensors was linearly changeable in correlation with the ethanol concentration, which translates into their high robustness. Such a simply prepared sensing device showed key features desired in the detection in the liquids area, which opens up the possibility of large-scale commercial production.

Physicochemically constructed zinc oxide and UV-curable polymer hybrid films for liquid crystal system

UV-nanoimprint lithography was performed with zinc oxide (ZnO) solution and a UV-curable polymer. The UV-curing time was 2, 4, or 6 min, after which the surfaces of the films were analyzed. Atomic force microscopy of the physical characteristics of the surfaces revealed that the clearest pattern was attained on the 6 min UV-cured film. Moreover, X-ray photoelectron spectroscopy analysis confirmed that varying the UV exposure time changed the composition of atoms and bonds on the surfaces of the films. Light transmittance measurements of the patterned ZnO hybrid films show that they all exhibited sufficient transmittance. To investigate the liquid crystal (LC) orientation, LC cells were fabricated with the various films into antiparallel structures. Polarized light microscopy confirmed stable LC alignment while a stable transmittance curve based on pretilt angle measurements was observed in LC cells fabricated with hybrid films exposed to UV light for more than 4 min. The relationship between the height of the groove pattern in the film and the alignment of the LC molecules was analyzed by using Berreman's model.

Chronic venous disease, platelet and haemostatic abnormalities contribute to the pathogenesis of pigmented purpuric dermatoses.

To investigate the aetiology of pigmented purpuric dermatoses (PPD). 63 patients with a provisional diagnosis of PPD were assessed. Skin biopsies were performed to confirm the clinical diagnosis. Haemostasis was assessed using platelet function analyser-100 (PFA-100), light transmission aggregometry (LTA), impedance aggregometry (Multiplate) and measurement of clotting times and clotting factors. Chronic venous disease (CVD) was assessed by duplex ultrasound. When not contraindicated, patients were advised to discontinue haemostatic-modifying drugs or supplements for 4weeks after which the laboratory measurements were repeated and the clinical resolution of PPD was assessed. Subsequently, a cohort of patients identified with CVD underwent endovenous interventions and further resolution of PPD was assessed. CVD was found in 48 patients (76.2%) while haemostatic abnormalities were found in 36 (57.1%). 30 patients (47.6%) had concurrent CVD and haemostatic abnormalities. Modifiable risk factors such as the intake of platelet inhibitors or other drugs and supplements such as fish oil were identified in 53 patients (84.1%). These could be ceased in 35 patients of whom 28 (80.0%) achieved either complete or partial resolution of PPD. Treatment of the underlying CVD was performed in 18 patients resulting in complete or partial resolution in 17 (94.4%). In seven patients (11.1%), no CVD or haemostatic abnormalities were identified, and the risk factors included dietary factors such as excessive caffeine or soft drink consumption. Haemostatic abnormalities and CVD contribute to the pathogenesis of PPD. Resolution of PPD in the vast majority of patients may be achieved by cessation of modifiable risk factors and in particular platelet-modifying drugs or supplements and treatment of the underlying venous disease.

Natural Dyes Used as Organic Coatings UV Protecting for Food Packages

Nowadays, the use of biodegradable and bio-derived plastics such as poly(lactic acid) (PLA) and cellulose in food packaging applications are replacing the use of different and more conventional oil-derived polymers that are much more expensive and unsuitable for the environment. However, their high transparency to ultraviolet (UV) radiation limits their current commercialization. Therefore, this study focuses on the deposition of organic thin films on commercial PLA and cellulose in order to enhance their performance, in particular for UV shielding. Coatings with different natural and biocompatible (edible) molecules, quinine and p-Coumaric acid, dispersed in different matrices are deposited by comparing different deposition techniques such as spray coating and spin coating. Morphological characterizations are carried out with atomic force microscopy (AFM) and scanning electron microscopy (SEM), with spectroscopic characterizations performed by light transmission measurements. Our results show that it is possible to enhance the UV protection of packaging using a suitable deposition with these biocompatible materials.

Measurement of Thin Carbon Films Absorption in the Visible Spectrum

The article is devoted to studying radiation absorption in the visible spectrum by thin carbon films. Two types of carbon films, diamond-like and graphite-like, with different structures, are investigated. The films are produced using laser vaporization of the initial material with a further coating of glass substrates. Measurements of light transmission through several samples of films with different thicknesses at three (or more) different areas are obtained for the wavelength range of 400-800 nm using the USB4000 compact fiber-optic spectrometer. The obtained results for the films with different thicknesses demonstrate scant differentiation of values (limiting to the same type of films). The imaginary parts of the films' complex refractive indices (absorption indices) are calculated. The comparison reveals the significant differences (by a factor of two or three) of the absolute values and trends of the absorption indices of diamondlike and graphite-like films. Both types of films are characterized by the expected increase in absorption when transitioning from the long-wavelength spectral region to the short-wavelength one. However, the rate of increase in absorption during such a transition is higher for the diamond-like films. These differences are related to the structure of the films.

Under-Ice Light Field in the Western Arctic Ocean During Late Summer

The Arctic is no longer a region dominated by thick multi-year ice (MYI), but by thinner, more dynamic, first-year-ice (FYI). This shift towards a seasonal ice cover has consequences for the under-ice light field, as sea-ice and its snow cover are a major factor influencing radiative transfer and thus, biological activity within- and under the ice. This work describes in situ measurements of light transmission through different types of sea-ice (MYI and FYI) performed during two expeditions to the Chukchi sea in August 2018 and 2019, as well as a simple characterisation of the biological state of the ice microbial system. Our analysis shows that, in late summer, two different states of FYI exist in this region: 1) FYI in an enhanced state of decay, and 2) robust FYI, more likely to survive the melt season. The two FYI types have different average ice thicknesses: 0.74 ± 0.07 m (N = 9) and 0.93 ± 0.11 m (N = 9), different average values of transmittance: 0.15 ± 0.04 compared to 0.09 ± 0.02, and different ice extinction coefficients: 1.49 ± 0.28 and 1.12 ± 0.19 m−1. The measurements performed over MYI present different characteristics with a higher average ice thickness of 1.56 ± 0.12 m, lower transmittance (0.05 ± 0.01) with ice extinction coefficients of 1.24 ± 0.26 m−1 (N = 12). All ice types show consistently low salinity, chlorophyll a concentrations and nutrients, which may be linked to the timing of the measurements and the flushing of melt-water through the ice. With continued Arctic warming, the summer ice will continue to retreat, and the decayed variant of FYI, with a higher scattering of light, but a reduced thickness, leading to an overall higher light transmittance, may become a more relevant ice type. Our results suggest that in this scenario, more light would reach the ice interior and the upper-ocean.

Temperature- and Pressure-Induced Bilayer Phase Transitions of an Amide-Linked Phosphatidylcholine: A Contrasting Effect of Chain-Linkage Type

Abstract An unnatural phospholipid with two amide linkages, dipalmitoylamidodeoxyphosphatidylcholine (DPADPC), was synthesized and its bilayer phase transitions were observed by differential scanning calorimetry under atmospheric pressure and light-transmittance measurements under high pressure. The DPADPC bilayer membrane showed different phase transitions depending on the thermal history of the lipid sample under atmospheric pressure. The thermal-history dependent transitions were also observed under high pressure. The temperature–pressure phase diagram and thermodynamic quantities of the phase transitions of the DPADPC bilayer membrane were compared with those of bilayer membranes of hydrophobic chain-linkage isomers, ester-linked dipalmitoylphosphatidylcholine (DPPC) and ether-linked dihexadecylphosphatidylcholine (DHPC). The thermodynamic quantities of the main transition for these PC bilayer membranes were similar to one another, whereas the suppression of the interdigitation and great stabilization of the hydrated crystal phase were observed for the DPADPC bilayer membrane. Furthermore, the results of nuclear magnetic resonance measurements indicated that the motility of PC molecules in both gel and liquid crystal phases of the DPADPC bilayer membranes were much lower than those of the DPPC and DHPC bilayer membranes. From the above results, we concluded that the molecular interaction in the PC bilayer membranes increases in the order of ether-, ester- and amide-linkage isomers.

Nonlocal transport phenomena in Weyl metals beyond the mesoscopic scale

Axion electrodynamics governs electromagnetic properties of Weyl metals. Although transmission and reflection measurements of light have been proposed to confirm the axion electrodynamics, there are still lack of theoretical proposals for macroscopic nonlocal transport phenomena in Weyl metals. In this paper, we present nonlocal transport phenomena in time reversal symmetry-broken (TRSB) Weyl metals. Solving the axion electrodynamics numerically, we show that such nonlocal transport phenomena arise from the negative longitudinal magneto-resistivity (NLMR), combined with the anomalous Hall effect (AHE) in the axion electrodynamics. Since this nonlocal transport occurs beyond the mesoscopic scale, we conclude that these nonlocal properties have nothing to do with Fermi arcs, regarded to be clear evidence of the axion electrodynamics in the bulk.

Examining the Transmission of Visible Light through Electrospun Nanofibrous PCL Scaffolds for Corneal Tissue Engineering.

The transparency of nanofibrous scaffolds is of highest interest for potential applications like corneal wound dressings in corneal tissue engineering. In this study, we provide a detailed analysis of light transmission through electrospun polycaprolactone (PCL) scaffolds. PCL scaffolds were produced via electrospinning, with fiber diameters in the range from (35 ± 13) nm to (167 ± 35) nm. Light transmission measurements were conducted using UV–vis spectroscopy in the range of visible light and analyzed with respect to the influence of scaffold thickness, fiber diameter, and surrounding medium. Contour plots were compiled for a straightforward access to light transmission values for arbitrary scaffold thicknesses. Depending on the fiber diameter, transmission values between 15% and 75% were observed for scaffold thicknesses of 10 µm. With a decreasing fiber diameter, light transmission could be improved, as well as with matching refractive indices of fiber material and medium. For corneal tissue engineering, scaffolds should be designed as thin as possible and fabricated from polymers with a matching refractive index to that of the human cornea. Concerning fiber diameter, smaller fiber diameters should be favored for maximizing graft transparency. Finally, a novel, semi-empirical formulation of light transmission through nanofibrous scaffolds is presented.

Giant Optical Anisotropy in High Temperature Superconducting Cuprate Bi2Sr2CaCu2O8+δ

Transmitted light measurements in ultraviolet and visible light regions have revealed giant optical anisotropy at 298 K in the high-Tc superconducting cuprates Bi2Sr2CaCu2O8+δ crystals with optimal...

Effect of Liquid Crystalline Host on Structural Changes in Magnetosomes Based Ferronematics.

The effect of the liquid crystalline host on structural changes in magnetosomes based on ferronematics is studied using the surface acoustic wave (SAW) technique supported by some capacitance and light transmission measurements. The measurement of the attenuation response of SAW propagating along the interface between LC and the piezoelectric substrate is used to study processes of structural changes under magnetic field. The magnetosome nanoparticles of the same volume concentration were added to three different nematic LCs, 5CB, 6CB, and E7. Unlike to undoped LCs, the different responses of SAW attenuation under the influence of magnetic and electric fields in LCs doped with magnetosomes were observed due to characteristic structural changes. The decrease of the threshold field for doped LCs as compared with pure LCs and slight effects on structural changes were registered. The threshold magnetic fields of LCs and composites were determined from capacitance measurements, and the slight shift to lower values was registered for doped LCs. The shift of nematic-isotropic transition was registered from dependencies of SAW attenuation on temperature. The acoustic anisotropy measurement approved the previous supposition about the role of bulk viscosity in used SAW measurements. In addition, capacitance and light transmition investigations supported SAW results and pointed out conclusions about their magnetic field behavior. Obtained results are discussed and confronted with previous ones and coincide well with those observed using acoustic, optical, or dielectric techniques.

Age-related histomorphometric and ultrastructural changes in the Sertoli cells of Japanese quail (Coturnix Coturnix japonica)

Prepared sections from pre-pubertal, pubertal, adult, and aged Japanese quail testes were examined by light microscopy and transmission electron microscopy (TEM) and measurements of seminiferous tubular diameter (STD), luminal diameter (SLD), epithelial height (SEH) and cross-sectional area of the seminiferous tubules (AST) were taken using an image analyzer. Apoptotic Sertoli cells with features such as cell shrinkage and chromatin condensation were observed in pre-pubertal and aged quail. There was a significant difference between the mean Sertoli cell number (SCN), SLD, SEH, STD and AST among the four age groups (P < 0.001). The highest SCN (mean ± standard error) was recorded in the adult (30.53 ± 0.42), with the aged group displaying the lowest mean (11.80 ± 0.27) SCN. Spearman’s rho correlation coefficients demonstrated a strong relationship between the SCN and SEH in the pubertal (ρ=0.915; P < 0.001), adult (ρ=0.878; P < 0.001), and aged (ρ=0.858; P < 0.001) groups, while a significant moderate correlation was observed in the pre-pubertal (ρ=0.606; P < 0.001) group. There were significant moderate correlations between the SCN and STD in the pre-pubertal (ρ=0.445; P < 0.001), pubertal (ρ=0.653; P < 0.001), adult (ρ=0.440; P < 0.001), and aged (ρ=0.514; P < 0.001) groups. Furthermore, significant moderate correlations were estimated between the SCN and AST in the pre-pubertal (ρ=0.453; P < 0.001), pubertal (ρ=0.661; P < 0.001), adult (ρ=0.393; P = 0.001), and aged (ρ=0.498; P < 0.001) groups. This study provides baseline data on the morphology and development of the Sertoli cell, as well as testicular morphometry in avian species during the pre-pubertal, pubertal, adult, and aged stages using the Japanese quail as a model.

Transparent Polyisocyanurate-Polyurethane-Based Aerogels: Key Aspects on the Synthesis and Their Porous Structures

The effect of the catalyst concentration on the synthesis and textural properties of polyisocyanurate-polyurethane aerogels is analyzed. The use of different catalyst amounts allows obtaining low-density aerogels (0.10–0.16 g/cm3) with high porosities (85–91%). Their porous structures were analyzed by scanning electron microscopy and nitrogen adsorption–desorption isotherm. A noticeable decrease in the size of the scattering centers, particles and pores, was achieved when reducing the catalyst amount. In some samples, the small size of these features, much smaller than the wavelength of visible light, causes a bare light dispersion, leading to the first transparent polyisocyanurate-polyurethane aerogels. Light transmittance measurements at 532 nm have been made showing high values (ca. 76% for 1 mm thick samples) for the formulations with the smallest particle and pore sizes. These aerogels presenting optical transparency have many potential applications such as solar collectors, glazing systems for insulating windows, and sensors, among others.

Subgel-phase formation of membranes of ether-linked phosphatidylcholines

The formation of subgel (so-called hydrated crystal) phase of membranes of ether-linked phospholipids, dialkylphosphatidylcholines containing linear saturated alkyl chain (Cn = 14, 16 and 18), was examined under atmospheric and high pressure. The results of differential scanning calorimetry in 50 wt% aqueous ethylene glycol solution and water showed that these PC membranes undergo the subtransition from the subgel phase to the gel phase at a low temperature with or without the thermal pretreatment of lipid samples called annealing. The subtransition in water was clearly observed by light-transmittance measurements under high pressure and the transition temperature increased by applying pressure. The temperature-pressure phase diagrams and the thermodynamic quantities of the subtransition were obtained from the phase-transition data and compared with those of membranes of ester-linked phospholipids, diacylphosphatidylcholines. The phase diagrams indicated that all gel phases of the ether-linked PC membranes exist as stable phases while parts of the gel phases of the ester-linked PC membranes are metastable. The subtransition temperatures of the ether-linked PC membranes were lower than those of the ester-linked PC membranes by more than 10 °C and the corresponding thermodynamic quantities were extremely small. Further, it was revealed by high-pressure fluorometry that the difference in subgel phase between ether- and ester-linked PC membranes results from their phase structures: the nonbilayer interdigitated structure is maintained after the conversion from the gel phase to the subgel phase in the ether-linked PC membranes whereas the ester-linked PC membranes form the bilayer subgel phase with staggered structure.