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Electron microscopic observation of photoreceptor cells in directly inserted anesthetized <i>Drosophila</i> into a high-pressure freezing unit
摘要： The high-pressure freezing (HPF) technique is known to cryofix water-containing materials with little ice-crystal formation in deep depths compared with other freezing techniques. In this study, HPF for anesthetized living Drosophila was performed by placing them directly on the carrier of the HPF unit and exposing them to light. Frozen Drosophila were freeze substituted, and their compound eyes were examined by transmission electron microscopy. The ultrastructures of ommatidia composed of photoreceptor cells were well preserved. The location of the cytoplasmic organelles inside the photoreceptor cells was observed. In some photoreceptor cells in ommatidia of the light-exposed Drosphila, the cytoplasmic small granules were localized nearer the base of rhabdomeres, compared with those of the nonlight-exposed Drosophila. Thus, HPF with the direct insertion of living Drosophila under light exposure into the HPF machine enabled us to examine changes to functional structures of photoreceptor cells that occur within seconds.
关键词： photoreceptor cell,high-pressure freezing,Drosophila
更新于2025-09-23 15:23:52
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InSight Auxiliary Payload Sensor Suite (APSS)
摘要： NASA’s InSight mission to Mars will measure seismic signals to determine the planet’s interior structure. These highly sensitive seismometers are susceptible to corruption of their measurements by environmental changes. Magnetic fields, atmosphere pressure changes, and local winds can all induce apparent changes in the seismic records that are not due to propagating ground motions. Thus, InSight carries a set of sensors called the Auxiliary Payload Sensor Suite (APSS) which includes a magnetometer, an atmospheric pressure sensor, and a pair of wind and air temperature sensors. In the case of the magnetometer, knowledge of the amplitude of the fluctuating magnetic field at the InSight lander will allow the separation of seismic signals from potentially interfering magnetic signals of either natural or spacecraft origin. To acquire such data, a triaxial fluxgate magnetometer was installed on the deck of the lander to obtain magnetic records at the same cadence as the seismometer. Similarly, a highly sensitive pressure sensor is carried by InSight to enable the removal of local ground-surface tilts due to advecting pressure perturbations. Finally, the local winds (speed and direction) and air temperature are estimated using a hot-film wind sensor with heritage from REMS on the Curiosity rover. When winds are too high, seismic signals can be ignored or discounted. Herein we describe the APSS sensor suite, the test programs for its components, and the possible additional science investigations it enables.
关键词： Wind,Magnetometer,Spacecraft,Pressure,Temperature,Instruments
更新于2025-09-23 15:23:52
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A novel dynamical approach in continuous cuffless blood pressure estimation based on ECG and PPG signals
摘要： Continuous cu?ess blood pressure (BP) monitoring has attracted much interest in ?nding the ideal treatment of diseases and the prevention of premature death. This paper presents a novel dynamical method, based on pulse transit time (PTT) and photoplethysmogram intensity ratio (PIR), for the continuous cu?ess BP estimation. By taking the advantages of both the modeling and the prediction approaches, the proposed framework e?ectively estimates diastolic BP (DBP), mean BP (BP), and systolic BP (SBP). Adding past states of the cardiopulmonary system as well as present states of the cardiac system to our model caused two main improvements. First, high accuracy of the method in the beat to beat BP estimation. Second, notwithstanding noticeable BP changes, the performance of the model is preserved over time. The experimental setup includes comparative studies on a large, standard dataset. Moreover, the proposed method outperformed the most recent and cited algorithms with improved accuracy.
关键词： Cu?ess blood pressure estimation,Taken’s theorem,Multivariate adaptive regression spline,Pulse transit time,Photoplethysmogram intensity ratio
更新于2025-09-23 15:23:52
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Cuff-less continuous measurement of blood pressure using wrist and fingertip photo-plethysmograms: Evaluation and feature analysis
摘要： Continuous monitoring of blood pressure improves prevention and control of cardiovascular diseases. Currently, cuff-based oscillometric sphygmomanometers are commonly used to monitor the systolic and diastolic blood pressure. However, this technique is discontinuous in nature and inconvenient for repeated measurements. Here we have proposed indirect measurement of blood pressure from photo-plethysmograms (PPG) simultaneously recorded from wrist and fingertip. The signals were recorded from 111 participants and different morphological features were obtained from PPG and its second derivative, acceleration plethysmograms (APG). Moreover, different measures of pulse transit time (PTT) and pulse wave velocity (PWV) were obtained from the recorded PPGs. Multi-layer Neural Networks were used to estimate the non-linear relationship between these features and systolic and diastolic blood pressures (SBP and DBP). Mean absolute errors of 6.77 and 4.82 mmHg were achieved in comparison with measurements from a validated commercial oscillometric sphygmomanometer. Feature analysis provided insight about the importance of features for estimating BP, and demonstrated that these features are not the same for SBP and DBP. Using the highest-ranked 15 and 13 features obtained from moving-backward algorithm the mean absolute errors were reduced to 5.31 and 4.62 mmHg for SBP and DBP. However, the optimum optimal feature sets provided by a genetic algorithm for estimating SBP/DBP led to the lowest mean absolute errors of 4.94/4.03. These results compared to previous studies and the available standards suggest that the method is a promising substitute for oscillometric sphygmomanometers which can be used conveniently for continuous monitoring of blood pressure.
关键词： Genetic algorithms,Non-obstructive blood pressure measurement,Multi-layer neural networks,Photo-plethysmography
更新于2025-09-23 15:23:52
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Multi-arm polymers prepared by atom transfer radical polymerization (ATRP) and their electrospun films as oxygen sensors and pressure sensitive paints
摘要： New oxygen and pressure sensitive paints (PSPs) with four-arm polymeric structures were prepared by using a kind of controlled living polymerizations - atom transfer radical polymerization (ATRP). The polymers composing of poly(isobutyl methacrylate)-co-poly(trifluoroethyl methacrylate)s (PolyIBMA-co-PolyTFEM)s act as the matrices for the platinum porphyrin-based phosphorescence probes, which were copolymerized in the matrices. The polymers were characterized by using 1H-NMR, 19F-NMR, and GPC to demonstrate their successful preparation. The influence of polymer structures on sensing activity including the sensitivity and response time to oxygen and/or pressure was investigated. Results showed that copolymers with suitable compositions (herein P3) can have highest sensitivity. Polymer structure's influence on response time to oxygen was also investigated. For increasing the polymer's surface area for further improving sensing sensitivity, electrospinning method was used for preparing films with micro-spherical or fibrous structures. The morphologies of electrospinning coated films were observed by SEM. Results showed that electrospinning coated films can respond much better to oxygen and pressure than their corresponding sprayed plates. This is the first time to apply the controlled living polymerization approach to prepare PSPs with multi-arm structures, which will broaden the PSP functional materials' design strategy.
关键词： oxygen sensing,pressure sensitive paints,electrospinning,multi-arm polymers,atom transfer radical polymerization
更新于2025-09-23 15:23:52
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Elastic, electronic and thermoelectric properties of Sr3MN (M?= Sb, Bi) under pressure
摘要： We have performed first-principles calculations to study the structural, elastic, electronic and thermoelectric properties of Sr3MN (M = Sb, Bi) under pressure. The optimized lattice parameters are in good agreement with the available experimental and theoretical measurements. Brittle to ductile transition occurs at 15 GPa and the hardness of both compounds decreases with the increase of pressure. The band gap slightly reduces with pressure and both compounds exhibit semiconducting nature for TB-mBJ potential. The density of states increases slightly at the Fermi level. The inclusion of the spin-orbit coupling effect reduces the band gap of Sr3BiN. The calculated Seebeck coefficient for Sr3SbN and Sr3BiN at 15 GPa and 600 K are 257 and 142 μV/K, respectively. The calculated lattice thermal conductivity of both compounds decreases with the increase of pressure, as phonon scattering increased. The predicted thermoelectric figure of merit (ZT) for Sr3SbN and Sr3BiN at 15 GPa and 600 K are 0.71 and 0.63, respectively. The obtained thermoelectric properties at high pressure making them suitable for thermoelectric device applications.
关键词： Lattice thermal conductivity,Pressure effect,Thermoelectric properties,Electronic properties,Elastic properties
更新于2025-09-23 15:23:52
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European Microscopy Congress 2016: Proceedings || Graphite-to-diamond (13C) direct transition in a diamond anvil high-pressure cell
摘要： As the hardest material in nature, diamond is of great importance and interest for scientific studies. However, formation of a diamond is complicated process and requires extreme conditions. Bundy and Kasper (1967) for the first time synthesized a new form of carbon—hexagonal diamond – under conditions of static pressure exceeding about 13 GPa and temperature greater than about 1000°C [1]. At room temperature the crystal structure of graphite is stable up to pressure 15 GPa and loses some of the graphite features at higher pressure, forming metastable graphitic or amorphous phases [2]. Transition of polycrystalline graphite to diamond occurs after hydrostatic pressure treatment near 70 GPa [3]. The development of solid-state phase transitions, including those at the stage of nucleation and development of a new phase practically always is connected with the relaxation of elastic stress [4], and in case of graphite-diamond transformation the latter can play main role. The goal of the present work is the formation of diamond from graphite in direct phase transition in a diamond anvil high-pressure cell, where the relaxation of elastic stress can be realized by means of plastic deformation of the sample. The experiment was performed at room temperature without a catalyst.13С was subjected to the shear deformation under pressure of 25 GPa. The structure studies of the obtained material were made by transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). In order to prevent the confusion of the diamond obtained in the experiment with one of the diamond anvils we used graphite composed of 13C carbon isotope atoms as a precursor. The diamond anvils consisted of conventional 12C diamond. Before TEM examination of each sample a Raman spectroscopy was used to verify that it contains only 13 C (diamond) and no 12C. TEM and EELS were carried out using JEOL JEM-2010 high-resolution transmission electron microscope. TEM analysis has shown that the samples obtained in the series of our experiments contain several phases of carbon simultaneously. After the high pressure treatment in shear diamond anvil cell (SDAC) there were observed some fragments of the sample, which contained both hexagonal and rhombohedral graphite (significant amounts of the last one), and also diamond and lonsdaleite. Fig. 1 shows the fragment, where the rhombohedral graphite presents. Fig. 2a shows the diamond structure fragment with {111}-planes composing 70o. Interplanar distances are 0.206 nm. Fig. 2b shows the EELS-spectrum which can be unambiguously attributed to a diamond. Thus, it was shown that 13С-graphite directly transforms into 13С-diamond (at least particularly) without a catalyst at room temperature after treatment in SDAC under pressure of 25 GPa.
关键词： EELS,high pressure,shear diamond anvil cell,HRTEM
更新于2025-09-23 15:23:52
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Ab Initio Design of Graphene Block Enables Ultrasensitivity, Multimeter-Like Range Switchable Pressure Sensor
摘要： In pursuit of the next-generation pressure sensors, the fabrication of graphene-based devices is considered to be one of the most promising approaches to address the unsatisfied sensitivity within a wide pressure range. Here, an ab initio design based on the graphene block is proposed to realize a high-performance and multimeter-like range switchable pressure sensor. The sensor contains three designed graphene-based foams with different initial resistances, which enable continuous resistance-change behavior induced by the pressure. Specifically, the reduced graphene oxide (rGO) foam–based sensor demonstrates a three times resistance change within the pressure range of 0–300 Pa, the rGO/polyurethane (rGO/PU) foam–based sensor presents a six times resistance change within the pressure range of 0.09–30 kPa, and the selenium-functionalized rGO/PU (SFrGO/PU) foam–based sensor displays a resistance change of more than 1000-fold within the pressure range of 1–72 kPa. Such different initial resistances and responses endow the device with controllable estimating pressure ranges, offering a switchable multimeter-like function for various applications. This ab initio design, which is applicable to various 2D materials and operation modes, can provide a facile and feasible approach toward the next-generation pressure sensors and other application fields related to 2D materials.
关键词： ultrahigh sensitivity,pressure sensor,graphene block,ab initio design,multimeter-like
更新于2025-09-23 15:23:52
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Development of a high temperature diamond anvil cell for x ray absorption experiments under extreme conditions
摘要： X-ray absorption spectroscopy (XAS) is presently a powerful and established tool to investigate solid and liquid matter at high pressure and high temperature (HP-HT). HP-HT XAS experiments rely on high pressure technology whose continuous development has extended the achievable range up to 100 GPa and more. In high pressure devices, high temperature conditions are typically obtained by using internal and external resistive heaters or by laser heating. We have recently developed a novel design for an internally heated diamond anvil cell (DAC) allowing XAS measurements under controlled high temperature conditions (tested up to about 1300 K). The sample in the new device can be rapidly heated or cooled (seconds or less) so the cell is suitable for studying melting/crystallization dynamics when coupled with a time-resolved XAS setup (second and sub-second ranges). Here we describe the internally heated DAC device which has been realized and tested in experiments on pure selenium at the energy dispersive ODE beamline of Synchrotron SOLEIL. We also present results obtained in XAS experiments of elemental Se using a large volume Paris-Edinburgh press, as an example of the relevance of structural studies of matter under extreme conditions.
关键词： high pressure,high temperature,DAC,Selenium,XAS
更新于2025-09-23 15:23:52
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Fiber Path Optimization in a Variable-Stifness Cylinder to Maximize Its Buckling Load Under External Hydrostatic Pressure
摘要： The optimum paths and orientations for curvilinear and straight fibers in composite cylindrical shells of variable and constant stiffness under external hydrostatic pressure are obtained and compared. The optimization was performed for several length-to-diameter ratios of the shells. Results showed that the buckling pressure of the variable-stiffness shell was by about 30% higher than that of the constant-stiffness one. This increase in the buckling pressure was obtained by locating fibers in the hoop direction in the middle of the cylinder and orienting the fibers toward the longitudinal direction on cylinder edges.
关键词： variable stiffness,cylindrical shell,external hydrostatic pressure,buckling,curvilinear fiber
更新于2025-09-23 15:23:52