The thermal equation of state (TEOS) for solids is a mathematic model among pressure, temperature and density, and is essential for geophysical, geochemical, and other high pressure–temperature (high P–T) researches. However, in the last few decades, there has been a growing concern about the accuracy of the pressure scales of the calibrants, and efforts have been made to improve it by either introducing a reference standard or building new thermal pressure models. The existing thermal equation of state,
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We analyze the effect of pressure on the Diels–Alder (D–A) dimerization reactions using Evans–Polanyi (E–P) theory, a thermodynamic analysis of the way in which a perturbation, in this case a hydrostatic pressure, modifies a reaction rate.
more » « less- Award ID(s):
- 2020525
- NSF-PAR ID:
- 10535351
- Publisher / Repository:
- RSC
- Date Published:
- Journal Name:
- RSC Mechanochemistry
- ISSN:
- 2976-8683
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract P (V ,T ) =P (V ,T 0) +P th(V ,T ), consists of an isothermal compression and an isochoric heating, while the thermal pressure is the pressure change in the isochoric heating. In this paper, we demonstrate that, for solids in a soft pressure medium in a diamond anvil cell, the thermal pressure can neither be determined from a single heating process, nor from the thermal pressure of its calibrant. To avoid the thermal pressure, we propose to replace the thermal pressure with a well-known thermal expansion model, and integrate it with the isothermal compression model to yields a Birch–Murnaghan-expansion TEOS model, called VPT TEOS. The predicted pressure of MgO and Au at ambient pressure from Birch–Murnaghan-expansion VPT TEOS model matches the experimental pressure of zero (0) GPa very well, while the pressure prediction from the approximated Anderson PVT TEOS exhibit a big deviation and a wrong trend. -
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Abstract This paper describes the design, development, and prototype testing of a device that can relieve contact pressure to potentially prevent pressure ulcers in bedridden patients by utilizing pneumatically actuated Fiber-Reinforced Elastomeric Enclosures (FREEs) [1,2].
Bedsores, or pressure ulcers, develop in bedridden patients due to constant contact pressure between a patient’s skin and an external (bed) surface. It is estimated that over 2.5 million patients [8] suffer from pressure ulcer developments annually in the United States. High pressure areas of the body include the sacrum and heel, with 36% of pressure ulcers occurring at the sacrum and 30% occurring at the heel. All other body areas each account for only 6% of pressure ulcer occurrence [6]. They are a major concern for low-mobility, patients who are bedridden for an extended periods and are associated with a 5x increase in patient mortality [3]. In addition, pressure ulcers place a significant cost burden on patients. Development of Stage 4 pressure ulcers and associated comorbidities can cost on average $127,000 to the patient [4]. This high cost is mainly due to attending caregiver’s time.
The most common solution for preventing the development of pressure ulcers in bed ridden hospital patients is for the attending nurses to reposition the patients every 2 hours so that the affected areas are relieved of any contact pressure. Repositioning patients is time consuming and strenuous for health care providers. General purpose “dynamic” pressure relief mattresses have shown to be somewhat effective in reducing the development of pressure ulcers. However, they do not effectively target high pressure areas and still necessitate frequent repositioning.
FREEs can be designed to generate a variety of shapes and motions once actuated (pressurized) and serve as building blocks for soft robotic applications. When FREEs, arranged in parallel, are embedded in a material with compatible elastic properties they propagate their deformed shape throughout the surface. These compliant sheets of FREEs are capable of sustaining loads while relieving pressure on high pressure areas of the body. The prototype for the device presented in this paper was designed for relieving pressure on a patient’s heel area. Preliminary test results demonstrate that the prototype device is effective at lifting a patient’s ankle, for patients weighing up to 250lbs, thus relieving contact pressure. The research also demonstrates the viability of developing modular pressure-relieving pads embedded with more advanced FREEs than described in this paper that can be tailored to relieve contact pressure on other affected areas such as the sacrum.
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Abstract Surface waves grow through a mechanism in which atmospheric pressure is offset in phase from the wavy surface. A pattern of low atmospheric pressure over upward wave orbital motions (leeward side) and high pressure over downward wave orbital motions (windward side) travels with the water wave, leading to a pumping of kinetic energy from the atmospheric boundary layer into the waves. This pressure pattern persists above the air–water interface, modifying the turbulent kinetic energy in the atmospheric wave-affected boundary layer. Here, we present field measurements of wave-coherent atmospheric pressure and velocity to elucidate the transfer of energy from the atmospheric turbulence budget into waves through wave-coherent atmospheric pressure work. Measurements show that the phase between wave-coherent pressure and velocity is shifted slightly above 90° when wind speed exceeds the wave phase speed, allowing for a downward energy flux via pressure work. Although previous studies have reported wave-coherent pressure, to the authors’ knowledge, these are the first reported field measurements of wave-coherent pressure work. Measured pressure work cospectra are consistent with an existing model for atmospheric pressure work. The implications for these measurements and their importance to the turbulent kinetic energy budget are discussed.
Significance Statement Surface waves grow through a pattern of atmospheric pressure that travels with the water wave, acting as a pump against the water surface. The pressure pumping, sometimes called pressure work, or the piston pressure, results in a transfer of kinetic energy from the air to the water that makes waves grow larger. To conserve energy, it is thought that the pressure work on the surface must extract energy from the mean wind profile or wind turbulence that sets the shape of the wind speed with height. In this paper, we present direct measurements of pressure work in the atmosphere above surface waves. We show that the energy extracted by atmospheric pressure work fits existing models for how waves grow and a simple model for how waves reduce energy in the turbulent kinetic energy budget. To our knowledge, these are the first reported field measurements of wave-coherent pressure work.
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ABSTRACT In this study, we explore the statistics of pressure fluctuations in kinetic collisionless turbulence. A 2.5D kinetic particle-in-cell simulation of decaying turbulence is used to investigate pressure balance via the evolution of thermal and magnetic pressure in a plasma with β of order unity. We also discuss the behaviour of thermal, magnetic, and total pressure structure functions and their corresponding wavenumber spectra. The total pressure spectrum exhibits a slope of −7/3 extending for about a decade in the ion-inertial range. In contrast, shallower −5/3 spectra are characteristic of the magnetic pressure and thermal pressure. The steeper total pressure spectrum is a consequence of cancellation caused by density-magnetic field magnitude anti-correlation. Further, we evaluate higher order total pressure structure functions in an effort to discuss intermittency and compare the power exponents with higher order structure functions of velocity and magnetic fluctuations. Finally, applications to astrophysical systems are also discussed.
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Abstract Background Millions of catheters for invasive arterial pressure monitoring are placed annually in intensive care units, emergency rooms, and operating rooms to guide medical treatment decision-making. Accurate assessment of arterial blood pressure requires an IV pole-attached pressure transducer placed at the same height as a reference point on the patient’s body, typically, the heart. Every time a patient moves, or the bed is adjusted, a nurse or physician must adjust the height of the pressure transducer. There are no alarms to indicate a discrepancy between the patient and transducer height, leading to inaccurate blood pressure measurements.
Methods We present a low-power wireless wearable tracking device that uses inaudible acoustic signals emitted from a speaker array to automatically compute height changes and correct the mean arterial blood pressure. Performance of this device was tested in 26 patients with arterial lines in place.
Results Our system calculates the mean arterial pressure with a bias of 0.19, inter-class correlation coefficients of 0.959 and a median difference of 1.6 mmHg when compared to clinical invasive arterial measurements.
Conclusions Given the increased workload demands on nurses and physicians, our proof-of concept technology may improve accuracy of pressure measurements and reduce the task burden for medical staff by automating a task that previously required manual manipulation and close patient surveillance.
