Simple adaptation of the Bridgman high pressure technique for use with liquid media

We present a simple novel technique to adapt a standard Bridgman cell for the use of a liquid pressure transmitting medium. The technique has been implemented in a compact cell, able to fit in a commercial Quantum Design PPMS system, and would also be easily adaptable to extreme conditions of very low temperatures or high magnetic fields. Several media have been tested and a mix of fluorinert FC84:FC87 has been shown to produce a considerable improvement over the pressure conditions in the standard steatite solid medium, while allowing a relatively easy setup procedure. For optimized hydrostatic conditions, the success rate is about 80% and the maximum pressure achieved so far is 7.1 GPa. Results are shown for the heavy fermion system YbAl(3) and for NaV(6)O(15), an insulator showing charge order.     

Development and performance of a magnetic ionic liquid for use in vacuum-compatible non-contact seals

For the electron-beam machining of optical media, a very low rotational speed is required to enable the precise fabrication of grooves of various depths and widths. In addition, a lubricant with a very low vapour pressure, such as an ionic liquid, and a vacuum chamber are needed to avoid contamination of workpieces. Accordingly, the development of a vacuum-compatible hydrostatic bearing using an ionic liquid is required to satisfy these rotational conditions and nanometre-order machining accuracy. To use a hydrostatic bearing in a vacuum environment, a non-contact vacuum seal is needed to avoid leakage of the ionic liquid used as the lubricant. Furthermore, making a non-contact seal using an ionic liquid requires the development of a new type of magnetic ionic liquid. Therefore, this paper describes the development of such a magnetic ionic liquid, which consists of magnetite (Fe₃O₄) particles, a newly synthesized dispersant, and a pyridinium-based ionic liquid. The outgassed products from this magnetic ionic liquid were measured when it was applied to a non-contact seal in a vacuum of about 10⁻⁶ Pa. In addition, its mechanical properties, such as viscosity and burst pressure as a non-contact seal, were measured. From these investigations, it was found that the developed magnetic ionic liquid would meet the requirements for non-contact seals to be used in vacuum-compatible hydrostatic bearings.     

High-pressure-low-temperature x-ray power diffractometer

A high-pressure technique for x-ray diffraction studies at low temperatures is described. The system consists of a Bridgman anvil type high-pressure device with either tungsten carbide or boron carbide anvils, a liquid He cryostat, and x-ray diffractometer operating in Debye-Scherrer geometry. The newly developed boron carbide anvil cell is capable of containing a liquid pressure transmitting medium. The precision of the lattice parameter determination is discussed and the effect of nonisostatic stress components on the diffraction pattern is examined.     

Wave propagation in a generalized thermoelastic solid cylinder of arbitrary cross-section immersed in a fluid

The wave propagation in a generalized thermoelastic solid cylinder of arbitrary cross-section immersed in a fluid is discussed in this paper. The solid medium is assumed to be linear, isotropic, temperature rate-dependent thermoelastic and the fluid medium is assumed to be inviscid. By imposing the continuity conditions on the interface between solid and fluid mediums, the frequency equation corresponding to the problem is obtained using the Fourier expansion collocation method. To compare the model with the existing literature, the results of a generalized thermoelastic solid cylinder without fluid are obtained and they show very good agreement. Also graphs and tables for various values of the material parameters are furnished.     

Measuring cell surface elasticity on enteroaggregative Escherichia coli wild type and dispersin mutant by AFM

Enteroaggregative Escherichia coli (EAEC) is pathogenic and produces severe diarrhea in humans. A mutant of EAEC that does not produce dispersin, a cell surface protein, is not pathogenic. It has been proposed that dispersin imparts a positive charge to the bacterial cell surface allowing the bacteria to colonize on the negatively charged intestinal mucosa. However, physical properties of the bacterial cell surface, such as rigidity, may be influenced by the presence of dispersin and may contribute to pathogenicity. Using the system developed in our laboratory for mounting and imaging bacterial cells by atomic force microscopy (AFM), in liquid, on gelatin coated mica surfaces, studies were initiated to measure cell surface elasticity. This was carried out in both wild type EAEC, that produces dispersin, and the mutant that does not produce dispersin. This was accomplished using AFM force-distance (FD) spectroscopy on the wild type and mutant grown in liquid or on solid medium. Images in liquid and in air of both the wild-type and mutant grown in liquid and on solid media are presented. This work represents an initial step in efforts to understand the pathogenic role of the dispersin protein in the wild-type bacteria.     

A Fiber Feedthrough for a Semiconductor Laser Located in a High Hydrostatic Pressure Cell

A fiber feedthrough for a semiconductor laser located in a high (20–22 kbar) hydrostatic pressure cell is a convenient tool for making electrooptical measurements of materials at high hydrostatic pressures. A prototype of a semiconductor laser tuned by high hydrostatic pressure has been developed. A simple method for supplying electric power to samples inside the pressure cell is described.     

Pressure cell for investigations of solid-liquid interfaces by neutron reflectivity

We describe an apparatus for measuring scattering length density and structure of molecular layers at planar solid-liquid interfaces under high hydrostatic pressure conditions. The device is designed for in situ characterizations utilizing neutron reflectometry in the pressure range 0.1-100 MPa at temperatures between 5 and 60?°C. The pressure cell is constructed such that stratified molecular layers on crystalline substrates of silicon, quartz, or sapphire with a surface area of 28 cm(2) can be investigated against noncorrosive liquid phases. The large substrate surface area enables reflectivity to be measured down to 10(-5) (without background correction) and thus facilitates determination of the scattering length density profile across the interface as a function of applied load. Our current interest is on the stability of oligolamellar lipid coatings on silicon surfaces against aqueous phases as a function of applied hydrostatic pressure and temperature but the device can also be employed to probe the structure of any other solid-liquid interface.     

An investigation of density determination methods for porous materials,small samples and particulates

Three new density measurement techniques have been devised and evaluated for the measurement of non-standard objects, namely porous material samples, small solid samples, powders and particulates. Hydrostatic weighing has traditionally been used to determine the density of solid artefacts. This method is not, however, suitable for porous objects since they will adsorb water making weighing in water unstable and possibly detrimental to the material samples. A method, weighing the artefacts in inert gas, has been developed for this application. The density determination of small solid artefacts cannot be achieved by conventional hydrostatic weighing techniques due to limits on the accuracy with which the weight-in-water can be determined. A density gradient column method for such measurements, delivering very low uncertainties, has been developed and evaluated. A liquid pyknometry method has also been investigated as an alternative to traditional helium and mercury pyknometry. The technique offers improved accuracy and a precise determination of thermal coefficient of the sample under test.     

Cell design for pressure to 25 kbar

A cell design is presented for experiments with hydrostatic pressures up to 25 kbar. The pressure-transmitting medium around the sample is candle wax, which is sealed in the cavity with molybdenum disulfide impregnated nylon and aluminum disks. This approach showed no detectable leakage to 25 kbar. Internal cavity pressure is computed from measurements of the applied load on the top piston, the transmitted load to the lower piston, and the frictional forces transmitted by the seals into the pressure vessel and the cell body. Internal pressure thus measured and phase-transition pressure data from RbCl and KBr are all within 9% of each other for the pressure range 3-25 kbar.     

高压容器壁外式超声波液位检测仪的研制

介绍了一种用于高压、密封容器内部液位测量的超声波液位仪的工作原理和系统组成，并讨论了多层媒质的声衰减影响，提出了减小测量盲区和校正温度、压力、介质成分影响的措施。该装置的测量探头只需吸附在容器底部的壁外，安装维护十分方便，尤其适合于高压容器的液位测量。     

High-resolution thermal expansion measurements under helium-gas pressure

We report on the realization of a capacitive dilatometer, designed for high-resolution measurements of length changes of a material for temperatures 1.4 K ≤ T ≤ 300 K and hydrostatic pressure P ≤ 250 MPa. Helium ((4)He) is used as a pressure-transmitting medium, ensuring hydrostatic-pressure conditions. Special emphasis has been given to guarantee, to a good approximation, constant-pressure conditions during temperature sweeps. The performance of the dilatometer is demonstrated by measurements of the coefficient of thermal expansion at pressures P ? 0.1 MPa (ambient pressure) and 104 MPa on a single crystal of azurite, Cu(3)(CO(3))(2)(OH)(2), a quasi-one-dimensional spin S = 1/2 Heisenberg antiferromagnet. The results indicate a strong effect of pressure on the magnetic interactions in this system.     

Accessory allowing an optical cell of 6-10,000 microm path for liquids and gases to be filled in vacuum and used under pressure

An accessory for introducing liquid or gaseous samples without any contamination into an evacuated cell for optical spectrometry is described. The procedure for its use is similar to that of sample injection into a gas-liquid chromatograph, no glove box or glove bag being needed. Main benefits are the wide choice of size of the samples, their recoverability, safety, and a range of optical paths allowing to measure the absorbance of strongly absorbing liquids and gases, very dilute liquid solutions, and liquefied gases under moderate pressure. Short path spectra of gaseous water pressure standards consent quantification of water partial pressure measured in common gas cells.     

High-pressure behavior of toroidal CVT fluid for automobile

Practical toroidal-type continuously variable transmission (t-CVT) is subjected to extremely severe operating conditions, viz., maximum contact pressure is very high at 4 GPa, rolling speed exceeds over 30 m/s and lubricant temperature goes up over 140 °C. Traction measurements were recently made at wide range of contact pressures, oil temperatures and rolling speeds by USCAR Group. The objective of this research is to investigate high-pressure rheology of the traction characteristics at extremely severe EHL contact conditions. The effects of contact pressure and temperature on maximum traction coefficient were evaluated using the phase diagram and the liquid/solid transition lubrication diagram.     

Application of polystyrene disk substrates in cellular cultivation methods: generalized specimen preparation protocol for scanning electron microscopy

Sample preparation for scanning electron microscopy (SEM) may vary by cellular type, composition and method of cultivation. It has been proposed here that a generalized method of sample preparation may be applied for the visualization of bacteria, fungi, and human cellular tissue without modification of protocol between cell types. The following protocol was developed to incorporate polystyrene disk substrates in the simplification of sample preparation for SEM and reduce the possibility of processing artefacts. The proposed method of preparation may be applied to samples grown in either liquid or solid cultural medium regardless of cell type. With the proposed protocol, centrifugation, isolation and critical point drying are not required, therefore increasing specimen integrity. The incorporation of polystyrene disks showed positive cellular adhesion and applications in SEM for bacterial, fungal and human neuronal tissue. In addition, the simplicity of the proposed protocol is highly adaptable and may be further incorporated to visually analyse the effects of antifungals, antibiotics and disease pathogenesis through pathogen–host interactions. The proposed method of specimen preparation was incorporated in either liquid or solid state growth mediums during the cultivation of the selected cellular samples and revealed great promise in the preservation and visualization under the scanning electron microscope.     

Design of a high-temperature and high-pressure liquid flow cell for x-ray absorption fine structure measurements under catalytic reaction conditions

The design and performance of a new high-pressure and high-temperature cell for measurement of x-ray absorption fine structure (XAFS) spectra of solid catalysts working in a flowing liquid are presented. The cell has flat, high-purity sintered cubic boron nitride (c-BN) windows which can tolerate high temperature (900 K) and high pressure (10 MPa). The c-BN is a new material which has the highest tensile strength, second only to diamond, and is also chemically and thermally stable. The use of the cell is demonstrated for measurements of PtPdAl(2)O(3) and Ni(2)PSiO(2) hydrodesulfurization catalysts at reaction conditions. A technique called delta chi (Deltachi), involving determining the difference between XAFS spectra of the sample at reaction conditions and the bare sample, is introduced.     

Simultaneous estimation of liquid level and density based on the maximum likelihood method

This paper considers the operation algorithm of a hydrostatic level sensor in a liquid of unknown density which is based on the determination of the moment when the level crosses the pressure sensor and provides increased accuracy of density and level measurements compared to available methods. The algorithm was synthesized on the basis of the maximum likelihood method. The algorithm was analyzed and experimental data are given.     

Electrical resistance tomography coupled with differential pressure measurement to determine phase hold-ups in gas–liquid–solid outer loop bubble column

Radial variation of the gas hold-ups and mean hold-ups are investigated in a 90 mm outer loop bubble column using electrical resistance tomography (ERT) with two axial locations (Plane 1 and Plane 2). In all the experiments, air is used as the gas phase, tap water as liquid phase, and polypropylene particles as solid phase where the superficial gas velocity is varied from 0.02 to 0.25 m/s. The effect of operating conditions, solid concentration on mean hold-ups and radial gas hold-ups distribution is discussed. Gas hold-ups and solid hold-ups results using ERT are in very good agreement with conventional estimation and correlations obtained using pressure transmitter methods. Meanwhile, the results show that the gas hold-ups in the centre region increase constantly with an increase in the superficial gas velocity, namely there is a maximum hold-up at the centre of cross-section. But, solid hold-ups distribution is very homogeneous for high gas velocity. According to the visible image, the gas–liquid flow behaviours are obtained for gas–liquid–solid outer loop bubble column. Furthermore, the results also indicate that ERT is a very powerful tool for diagnosing the ‘inside’ flow behaviour of gas–liquid–solid three phase bubble column.     

New hydrostatic pressure cell to 90 kilobars for precise electrical and magnetic measurements at low temperatures

A new type of hydrostatic pressure cell is discussed. It is suitable for precise electrical and magnetic measurements on several samples simultaneously over a wide range of temperature and pressure. Pressures as high as 90 kilobars have thus far been reached in a four-point electrical resistivity measurement. These studies indicate minimal pressure changes upon cooling from 300 to 1 K, good pressure homogeneity, and absence of significant shear stresses.     

大型螺旋桨静压支承静平衡仪设计研究

介绍了一种采用球面静压支承的船用螺旋桨静平衡仪,分析了平衡仪的工作原理及静压支承压力分布、承载能力和油膜刚度等性能特点,给出了采用电子称重和角位移确定螺旋桨不平衡质量及方位的检测方法,提高了检测精度。     

Flexible contact stamp for electrical conductivity measurements of a soft matter

In this communication, a simple homemade four probe conductivity setup has been presented to measure the electrical conductivity of molecularly grafted and passivated solid surfaces. Setup was also extended for the temperature dependent conductivity measurements by designing a small furnace using nichrome heating element. The importance of prepared setup lies in its easy designing ability, portability and reliability to measure the conductivity of soft matters. Setup was designed for four probe conductivity measurements which can be used for two probes conductivity measurements also, depending upon the requirements under investigation. Setup was tested using its four probes for electrochemically grafted indium tin oxide surfaces with thiol containing organic molecules and trichloroethylene passivated Si surface. It was found very sensitive even for observing small changes in current–voltage values whereas recorded curves were quite reproducible.