Effect of external pressure and muscle contraction on soft tissue oxygenation measured with near infrared spectroscopy

External cricoid pressure is increasingly used to augment the upper esophageal sphincter (UES). Our objective was to determine the effect of 1) pressures applied to cricoid, supracricoid, and subcricoid regions on the length and amplitude of the UES high-pressure zone (UESHPZ), and 2) the external cricoid pressure on lower esophageal sphincter (LES) tone. Case-control study. We studied 11 patients with supraesophageal reflux (mean age 58 ± 12 years) and 10 healthy volunteers (mean age 47 ± 19 years). We tested 20, 30, and 40 mm Hg pressures to cricoid, 1 cm proximal and 1 cm distal to the cricoid. In an additional 15 healthy volunteers (mean age 46 ± 23 years), we studied the effect of external cricoid pressure on LES tone. UES and LES pressures were determined using high-resolution manometry. There was significant increase of UESHPZ length with application of pressure at all sites. The increase of UESHPZ length was relatively symmetric, more orad, and more caudad when the pressure was applied at the cricoid, supracricoid, and subcricoid levels, respectively. The magnitude of pressure increase was greatest at the middle and orad part of the UESHPZ when the pressure was applied at the cricoid and supracricoid levels, respectively. The corresponding magnitude of increase in the caudad part of the UESHPZ was not observed with pressure at the subcricoid level. There was no change of the LES pressure with application of cricoid pressure. The effect of external pressure on the UESHPZ is site dependent. Subcricoid pressure has the least effect on UESHPZ. External cricoid pressure at 20 to 40 mm Hg has no effect on the LES pressure. 3b. Laryngoscope, 127:2466-2474, 2017.

Rechargeable lithium metal anode batteries (RLB) have the potential to meet the Department of Energy’s 500 Wh/kg goal [1]. However, higher cycling efficiency and safety of these cells is challenged by the dendritic Li plating morphology. Li surface protective coating or electrolyte that can promote growth of stable solid electrolyte interphase from the reduction products can prevent dendritic growth of Li during plating. Another way to suppress the dendritic growth and facilitate more uniform Li surface morphologies is by applying the external pressure to the cell [2]. The external cell pressure can influence the Li plating conditions and modify Li surface. The growth of Li dendrites can be suppressed due to the Li surface strain field under external cell pressure. Also the loss due to dead lithium can be minimized by maintaining a good electrochemical contact between Li deposits. A dendrite-free uniform mossy Li surface with good electrochemical contact will improve the cycling efficiency and safety of the cells. The effect of external cell pressure was studied in cells with nickel rich LiNi0.6Mn0.2Co0.2O2 cathode and Li metal anode. The cycling performance was analyzed with electrochemical diagnostics tools. The Li surface morphology was characterized with scanning electron microscopy. The effects of various external pressure on cycling efficiency and the Li surface morphology will be illustrated and discussed.

The effect of external hydrostatic pressure on the cross sectional behavior of fabricated tubular columns is studied analytically using tangent stiffness approach. The moment-curvature behavior of a short column is of prime importance in the analysis of any long beam-column. The results will be applied to study the effect of external pressure on the strength and behavior of long beam-columns. The fabricated tubular column contains imperfections such as out-of-roundness and longitudinal and transverse residual stresses. These imperfections combined with the effect of external pressure are studied in the present analysis. Tresca yield criterion is used for elements in biaxial stress state, which is induced by the interaction of axial stress and longitudinal and transverse residual stresses and magnified by external pressure. A computer program has been developed to obtain numerical results from which practical design formulas are derived for cross-sectional capacity of fabricated tubular columns subjected to axial force, bending moment and external hydrostatic pressure.

PurposeAero-engine casings commonly use composite cylindrical shell structures with excellent properties such as corrosion resistance and fatigue resistance. Still, their vibration behavior is relatively complex and may cause fatigue vibration damage, so it is essential to analyze the vibration characteristics of composite cylindrical shells. The purpose of this paper is to analyze the vibration characteristics of multilayer composite cylindrical shells subjected to external pressures and having different interlayer thickness ratios and provide some theoretical basis for the fatigue damage prediction of cylindrical shell casing to ensure the safety and stability of the engine during flight.Design/methodology/approachFirstly, the vibration differential equation with external pressure is established based on Soedel theory considering nonlinear effects, while four symmetric boundary conditions are chosen to constrain the cylindrical shell. Then the Rayleigh–Ritz method, which is more efficient and accurate in calculating large structural systems, is applied to solve the problem, and the theoretical model of three-layer cylindrical shell under external pressure is established. The accuracy of the model is verified by comparing the data with the specialized literature. Subsequently, the effects of different external pressures and different thickness-to-diameter ratios, different length-to-diameter ratios and different interlayer thickness percentages on the natural frequency of multilayer composite cylindrical shells were investigated by control variable analysis.FindingsThe conclusions obtained show that the external pressure increases the natural frequency of the cylindrical shell and that the frequency characteristics of the cylindrical shell vary for different boundary conditions. The effect of length-to-diameter ratio, thickness-to-diameter ratio and the percentage of the thickness of the intermediate layer on the natural frequency of the cylindrical shell are significantly increased under external pressure. Because the presence of external pressure increases the frequency of the cylindrical shell by about 70%, it has almost no effect on the frequency at the minimum number of circumferential waves, and the effect on the frequency at the maximum number of circumferential waves is reduced to about 50%. The frequencies in the SL-SL boundary condition are all in perfect agreement with the S-S boundary condition under the influence of different influencing factors.Originality/valueIn this paper, the effect of external pressure and the natural properties of the cylindrical shell under external pressure on the cylindrical shell’s frequency is considered, emphasizing the effect of different layer thickness ratios on the frequency. This paper aims to summarize the changing law between the natural frequency of the cylindrical shell itself and different design parameters during the flight pressure process. Reliable theoretical predictions are provided for analyzing the vibrational behavior of shells subjected to external pressures in aerospace, as well as a database for the practical production of cylindrical shells.

Rechargeable Lithium-ion batteries (LIBs) are the power source used widely in portable electronic devices and are becoming increasingly important in the automotive industry applications. LIBs need to be high-energy, safe, and cost-effective to address the demand for large driving ranges of batteries in electric vehicles (EVs) and hybrid electric vehicles (HEV). Therefore, technologies for extending the cycle life of LIBs and solving component degradation problems are required. Recently, the recharging time for batteries in EVs is longer compared to the refueling time for gasoline-powered vehicles which prevents the widespread adoption of battery-powered EVs into the transportation sector. In that perspective, achieving fast charge has been considered as one of the most important directions for the progression of EVs in the market and it can possibly lead to increased customer acceptability by reducing charging time. However, fast charging of LIBs makes them susceptible to lithium plating and induces high temperatures, and the decomposition of electrolytes results in thermal runaway and explosion. Thus, understanding capacity fades and improving cell stability for long cycle life at a high C-rate are critical for designing LIBs. It has been known that external pressure has a positive influence on Li-ion pouch cell capacity fading during aging experiments. Nonetheless, the effect of external pressure under high C-rate conditions is not well understood and has not been extensively covered in many studies. Even in some of the research conducted experiments under high C-rate conditions, the concept of normalized capacity has been introduced, leading to studies that do not account for the initial capacity drop [1,2].This work analyzed the effect of external pressure on the battery’s sustainability under high C-rate conditions. The interrelationship of mechanical pressure and the electrochemical performance was investigated using 1.05 Ah graphite/NMC622 stacked LIBs. The charging speed was set to 1,5 and 10C-rates in the constant current/constant voltage (CC-CV) mode to test fast charging conditions. The pressure and thickness changes were analyzed using the pressure measurement system and 3-dimensional digital image correlation (3D-DIC). Also, the post-mortem analysis conducted to confirm the morphology of each cell component and internal resistance under fast charging conditions were analyzed using scanning electron microscopy (SEM) analysis and electrochemical impedance spectroscopy (EIS), respectively. The results demonstrate the negative influence of the external pressure was confirmed initial cycling stage increases the internal resistance which lowers the ionic conductivity. Overall, we propose that innovative pressurizing strategies to maximize cell cyclability and pressure sensing results could provide a non-destructive diagnostic approach to support the advancement of fast-charging battery technologies. This research highlights the significance of external active pressurization in systems operating at high C-rates. Reference [1] Mussa, A.S., et al., Effects of external pressure on the performance and ageing of single-layer lithium-ion pouch cells. Journal of Power sources, 2018. 385: p. 18-26[2] Chen, F., et al., Air and PCM cooling for battery thermal management considering battery cycle life. Applied Thermal Engineering, 2020. 173: p. 115154 Figure 1

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Due to close contact between various components, the volume change of active materials during lithiation or delithiation leads to inevitable constraint-induced stresses. This is particularly prominent in all-solid-state batteries, which impose relatively high external pressure on electrode particles. To date, the effects of this additional external pressure on chemo-mechanical coupled behaviors are not fully understood. To address these issues, this study develops a chemo-mechanical coupled model of electrode particles in Li-based batteries that incorporates the effects of surface stress and external pressure. The theoretical results indicate that lithiation kinetics and stress evolution within electrode particles are size-dependent, varying from bulk to nanoscale sizes. As particle size decreases, Li ions increasingly tend to accumulate near-surface storage sites, which is aggravated by external pressure due to the growing compressive stress and a resultant reduction in stress-dependent diffusivity. Moreover, the low-porosity surrounding matrix can exacerbate this tendency by amplifying the external pressure. The work enhances our understanding of capacitor-like behaviors of some nanosized electrode materials, which may arise from the combined effects of surface stress and external pressure. It also emphasizes the importance of interactions between neighboring components in chemo-mechanical coupled performance.

Lithium-ion batteries have attracted wide attention as automotive applications with their advantages of high energy density and performance. The pouch type cell has been a preferred candidate based on their light weight, cost effectiveness, and design flexibility. However, due to the low mechanical stability, their characteristics are strongly influenced by environmental conditions. Especially, external pressure on cell surface directly affects the swelling phenomenon which is closely related to performance, life cycle and structural safety of the battery pack. In this paper, a novel framework for design optimization of battery pack is proposed to apply appropriate pressure on pouch cells. The effect of external pressure is investigated through cell cycling tests while thickness, pressure and capacity changes are measured. This investigation shows a recognizable correlation between pressure and cell degradation and also indicates the needs of certain pressure level which should be ensured by pack structures. The mechanical relation between cell and structural components is demonstrated in a free body diagram and utilized for deterministic analysis. To consider uncertainties in the external pressure formulation, the system is hierarchically decomposed and the uncertainty for each sub-component is analyzed. Then, the uncertainty propagation is conducted using Monte-Carlo Simulation to predict the distribution of external pressure in pack level. Based on the results, probabilistic design optimization is performed to minimize the weight of battery pack structure ensuring the external pressure range. The results of deterministic and probabilistic design optimization are compared. The deterministic analysis includes the safety factor based method and the arithmetic worst case based method. The probabilistic analysis is formulated for ensuring the minimum required pressure with the confidence level of 99.7%. After the pressure distribution analysis, the design of module and pack structure is modified to generate the appropriate pressure on the cell surface. The improved module and pack designs are verified by numerical simulations and tests. By adopting the probabilistic design optimization, it is expected that the life cycle reliability and the performance of battery pack can be improved. In addition, more than 17% of weight reduction can be achieved compared to conventional deterministic based design optimization. A novel framework for probabilistic design optimization of battery pack is proposed in considering the effect of external pressure on pouch cell. Various uncertainty factors in formulating external pressure are analyzed by using probabilistic method and compared with the deterministic method. This proposed design technique can be utilized for developing compatible automotive battery packs and improving reliability under uncertainty.

The effects of ventricular geometry, muscle mass, muscle elasticity and external pressures on the pressure-volume and muscle stiffness-stress relations have been quantitated on the basis of a theoretical model. Data taken from patients before and after interventions with nitroprusside and angiotensin were applied to the model in order to explain the possible causes for the marked shifts in the pressure-volume relations.

HomeCirculation ResearchVol. 41, No. 1Ventricular pressure-volume curve indices with end-diastolic pressure. Free AccessAbstractPDF/EPUBAboutView PDFSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessAbstractPDF/EPUBVentricular pressure-volume curve indices with end-diastolic pressure. I Mirsky I MirskyI Mirsky Search for more papers by this author Originally published1 Jul 1977https://doi.org/10.1161/01.RES.41.1.135Circulation Research. 1977;41:135–139 Previous Back to top Next FiguresReferencesRelatedDetailsCited By Fremes S, Weisel R, Baird R, Mickleborough L, Burns R, Teasdale S, Ivanov J, Seawright S, Madonik M, Mickle D, Scully H, Goldman B and McLaughlin P (1983) Effects of postoperative hypertension and its treatment, The Journal of Thoracic and Cardiovascular Surgery, 10.1016/S0022-5223(19)39208-6, 86:1, (47-56), Online publication date: 1-Jul-1983. Mirsky I, Pfeffer J, Pfeffer M and Braunwald E (1983) The contractile state as the major determinant in the evolution of left ventricular dysfunction in the spontaneously hypertensive rat., Circulation Research, 53:6, (767-778), Online publication date: 1-Dec-1983.Hood W, Amende I, Simon R and Lichtlen P (1980) The effects of intracoronary nitroglycerin on left ventricular systolic and diastolic function in man., Circulation, 61:6, (1098-1104), Online publication date: 1-Jun-1980.Mirsky I and Rankin J (1979) The effects of geometry, elasticity, and external pressures on the diastolic pressure-volume and stiffness-stress relations. How important is the pericardium?, Circulation Research, 44:5, (601-611), Online publication date: 1-May-1979.Grossman W and Barry W (1979) Comments on "Factors which affect the diastolic pressure-volume curve"., Circulation Research, 44:4, (589-592), Online publication date: 1-Apr-1979. Mirsky I (1978) Effects of external pressures on the pressure-volume relation of the left ventricle, Bulletin of Mathematical Biology, 10.1007/BF02460772, 40:4, (465-482), Online publication date: 1-Jul-1978. July 1, 1977Vol 41, Issue 1 Advertisement Article InformationMetrics Copyright © 1977 by American Heart Associationhttps://doi.org/10.1161/01.RES.41.1.135 Originally publishedJuly 1, 1977 PDF download Advertisement

It is shown that in a model chain of exchange clusters magneto-structural transitions are very sensitive to the variation of initial exchange integrals of the model. The cases of three-spin chains (a model of polymer chains of exchange clusters of the family of compounds of “breathing crystal” with the “head-head” motif) and two-spin chains (a model of these chains with the “head-tail” motif) are studied theoretically. A change in the exchange integrals under the effect of external pressure can substantially modify the thermal dependence of the magneto-structural and magneto-resonance properties of “breathing crystals”, which calls for the experimental studies in this aspect. The dependence of these properties on external pressure in “breathing crystals” is expected to have a more complex and diverse form than the ordinary high-temperature shift in the traditional spin-crossover compounds based on iron complexes. Some competing physical factors able to cause such a diversity are described qualitatively. Model calculations show that apart from the temperature shift, the application of external pressure to the “breathing crystals” can result in a change in the low-temperature limit of the effective magnetic moment in the exchange clusters of these compounds.

Purpose: the existing problem of detected damages to tank car boilers during operation due to loss of stability requires new approaches to both theoretical and practical assessment of possible causes of such damages. The evaluation of the combination of various factors, including the impact of shape deviation of the boiler during its manufacture, on the possibility of loss of stability during operation is of particular relevance. Method: to determine the causes of boiler deformation, stability calculations were performed on the boiler. All calculations were conducted for actual thicknesses determined by measurement and thickness gauging.A tank car model with the minimum measured thicknesses was selected for modeling. Calculations were carried out under the action of the standard external pressure value and under excessive external pressure values. Results: stability calculations of the boiler with the actually measured thicknesses under the influence of external excess pressure showed that loss of stability in the boiler: without shape deviation under the action of the standard external excess pressure of 40 kPa was not detected; with local defects from welding under the action of the standard external excess pressure of 40 kPa was not detected; without local welding defects but with a global shape deviation of the boiler under the action of external excess pressure of 40 kPa is possible with a relative ovality of about 2.7 %; without global shape deviation of the boiler, it is possible under the influence of excessive external pressure of 79 kPa and above. Practical significance: possible causes of boiler instability during operation were identified. The cause of boiler instability may be a global shape deviation of the boiler with a relative ovality of about 2.7 %; the effect of excessive external pressure of 79 kPa and above, which is possible due to a violation of the tank car unloading process; a combination of global shape deviation of the boiler and the effect of excessive external pressure due to a violation of the tank car unloading process.

In Brief The prevalence of heel ulcers across settings is high and is increasing. Prevention of ulcers requires knowledge of their etiology and the scientific basis for preventive care. The interaction between external pressure and the heel vasculature is central to the prevention of heel ulcers. This article focuses on the prevention of heel pressure ulcers. The physiology of heel tissue perfusion, the effect of external pressure on heel perfusion, as well as what is known about strategies to reduce external pressure and approaches to improve heel skin blood flow will be discussed. It is only through understanding of the physiology of heel tissue perfusion and its relation to external pressure that effective preventive measures to reduce heel skin breakdown can be adapted in clinical practice. The physiology of heel tissue perfusion, the effect of external pressure on heel perfusion, as well as what is known about strategies to reduce external pressure and approaches to improve heel skin blood flow are considered, pursuant to providing effective preventive measures to reduce heel skin breakdown in clinical practice.

Experimental results on the effect of external hydrostatic pressure up to 5 kbar on the ρ(T) dependence in the ab plane of HoBa2Cu3O7−x single crystals (x ≈ 0.35) in the temperature range from 300 K to the superconducting transition temperature Tc are presented and discussed. It was established that the application of external hydrostatic pressure P = 5 kbar significantly intensified the process of diffusion coalescence of oxygen clusters, causing the growth of their average size. This leads to an increase in the number of negative U-centers, the presence of which results to the appearance of a phase capable of generating paired carriers of electric charge and, correspondingly, characterized by a higher transition temperature Tc. Employing this hypothesis that concerns the mechanism of the diffusion coalescence of oxygen clusters, the change in the form of the temperature and time dependences of the electrical resistivity under the application of external hydrostatic pressure is discussed.

Effect of External Positive and Negative Pressure on Venous Flow in an Experimental Model