Browsing by Subject "PRESSURES"

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  • Lantto, Juulia; Erkinaro, Tiina; Haapsamo, Mervi; Huhta, Heikki; Voipio, Hanna-Marja; Hohimer, A. Roger; Davis, Lowell E.; Acharya, Ganesh; Räsänen, Juha (2019)
    The foramen ovale (FO) accounts for the majority of fetal left ventricular (LV) output. Increased right ventricular afterload can cause a redistribution of combined cardiac output between the ventricles. To understand the capability of the FO to increase its volume blood flow and thus LV output, we mechanically occluded the main pulmonary artery in seven chronically instrumented near-term sheep fetuses. We hypothesized that FO volume blood flow and LV output would increase during main pulmonary artery occlusion. Fetal cardiac function and haemodynamics were assessed by pulsed and tissue Doppler at baseline, 15 and 60 min after occlusion of the main pulmonary artery and 15 min after occlusion was released. Fetal ascending aorta and central venous pressures and blood gas values were monitored. Main pulmonary artery occlusion initially increased fetal heart rate (P <0.05) from [mean (SD)] 158 (7) to 188 (23) beats min(-1) and LV cardiac output (P <0.0001) from 629 (198) to 776 (283) ml min(-1). Combined cardiac output fell (P <0.0001) from 1524 (341) to 720 (273) ml min(-1). During main pulmonary artery occlusion, FO volume blood flow increased (P <0.001) from 507 (181) to 776 (283) ml min(-1). This increase was related to fetal tachycardia, because LV stroke volume did not change. Fetal ascending aortic blood pressure remained stable. Central venous pressure was higher (P <0.05) during the occlusion than after it was released. During the occlusion, fetal pH decreased and PCO2 increased. Left ventricular systolic dysfunction developed while LV diastolic function was preserved. Right ventricular systolic and diastolic function deteriorated after the occlusion. In conclusion, the FO has a limited capacity to increase its volume blood flow at near-term gestation.
  • Dingilian, Kayane K.; Halonen, Roope; Tikkanen, Valtteri; Reischl, Bernhard; Vehkamaki, Hanna; Wyslouzil, Barbara E. (2020)
    We studied the homogeneous nucleation of carbon dioxide in the carrier gas argon for concentrations of CO(2)ranging from 2 to 39 mole percent using three experimental methods. Position-resolved pressure trace measurements (PTM) determined that the onset of nucleation occurred at temperatures between 75 and 92 K with corresponding CO(2)partial pressures of 39 to 793 Pa. Small angle X-ray scattering (SAXS) measurements provided particle size distributions and aerosol number densities. Number densities of approximately 10(12)cm(-3), and characteristic times ranging from 6 to 13 mu s, resulted in measured nucleation rates on the order of 5 x 10(17)cm(-3)s(-1), values that are consistent with other nucleation rate measurements in supersonic nozzles. Finally, we used Fourier transform infrared (FTIR) spectroscopy to identify that the condensed CO(2)particles were crystalline cubic solids with either sharp or rounded corners. Molecular dynamics simulations, however, suggest that CO(2)forms liquid-like critical clusters before transitioning to the solid phase. Furthermore, the critical clusters are not in thermal equilibrium with the carrier gas. Comparisons with nucleation theories were therefore made assuming liquid-like critical clusters and incorporating non-isothermal correction factors.
  • Baird, Zachariah Steven; Dahlberg, Artur; Uusi-Kyyny, Petri; Osmanbegovic, Nahla; Witos, Joanna; Helminen, Jussi; Cederkrantz, Daniel; Hyväri, Paulus; Alopaeus, Ville; Kilpeläinen, Ilkka; Wiedmer, Susanne K.; Sixta, Herbert (2019)
    7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (mTBD) has useful catalytic properties and can form an ionic liquid when mixed with an acid. Despite its potential usefulness, no data on its thermodynamic and transport properties are currently available in the literature. Here we present the first reliable public data on the liquid vapor pressure (temperature from 318.23K to 451.2K and pressure from 11.1Pa to 10000Pa), liquid compressed density (293.15K to 473.15K and 0.092MPa to 15.788MPa), liquid isobaric heat capacity (312.48K to 391.50K), melting properties, liquid thermal conductivity (299.0K to 372.9K), liquid refractive index (293.15K to 343.15K), liquid viscosity (290.79K to 363.00K), liquid-vapor enthalpy of vaporization (318.23K to 451.2K), liquid thermal expansion coefficient (293.15K to 473.15K), and liquid isothermal compressibility of mTBD (293.15K to 473.15). The properties of mTBD were compared with those of other relevant compounds, including 1,5-diazabicyclo(4.3.0)non-5-ene (DBN), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and 1,1,3,3-tetramethylguanidine (TMG). We used the PC-SAFT equation of state to model the thermodynamic properties of mTBD, DBN, DBU, and TMG. The PC-SAFT parameters were optimized using experimental data.
  • Venermo, M.; Settembre, N.; Albäck, A.; Vikatmaa, P.; Aho, P. -S.; Lepantalo, M.; Inoue, Y.; Terasaki, H. (2016)
    Background: Ankle brachial index (ABI), toe pressures (TP), and transcutaneous oxygen pressure (TcPO2) are traditionally used in the assessment of critical limb ischemia (CLI). Indocyanine green (ICG) fluorescence imaging can be used to evaluate local circulation in the foot and to evaluate the severity of ischemia. This prospective study analyzed the suitability of a fluorescence imaging system (photodynamic eye [PDE]) in CLI. Material and methods: Forty-one patients with CLI were included. Of the patients, 66% had diabetes and there was an ischemic tissue lesion in 70% of the limbs. ABI, toe pressures, TcPO2 and ICG-fluorescence imaging (ICG-FI) were measured in each leg. To study the repeatability of the ICG-FI, each patient underwent the study twice. After the procedure, foot circulation was measured using a time-intensity curve, where T1/2 (the time needed to achieve half of the maximum fluorescence intensity) and PDE10 (increase of the intensity during the first 10 s) were determined. A time-intensity curve was plotted using the same areas as for the TcPO2 probes (n=123). Results: The mean ABI was 0.43, TP 21 mmHg, TcPO2 23 mmHg, T1/2 38 5, and PDE10 19 AU. Time-intensity curves were repeatable. In a Bland-Altman scatter plot, the 95% limits of agreement of PDE10 was 9.9 AU and the corresponding value of T1/2 was 14 s. Correlation between ABI and TP was significant (R=.73, p Conclusions: According to this pilot study, ICG-Fl with PDE can be used in the assessment of blood supply in the ischemic foot. (C) 2016 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.
  • Huang, Wenfeng; Li, Zhijun; Leppäranta, Matti; Han, Hongwei; Wang, Ni (2018)
    Ice strain dominates the ice thrust and dynamics on reservoir dams and retaining structures. An exclusively designed laser range finder was deployed to measure the surface ice displacements along six directions at a reservoir in northeastern China. The incompletely confined boundary (ice-boundary bonding), ice cracks development, water level fluctuations, parallel crack dynamics, and ice creep allow the surface ice to move rather than keep still in response to thermal deformation/pressure, and thus cause the ice strain to deviate from thermal strain. Consequently, a residual strain was introduced and calculated from the recorded displacements. Observations showed that the residual strains were anisotropic and showed diurnal patterns following the air/ice temperature. A scale-dependence of crack development was observed to cause potential scale-effects to residual strains. The real ice strain consists of thermal strain and residual strain. The proportion of the latter increased as time went by. A modified constitutive law accommodating the residual strains was developed to evaluate the impacts of the residual strains and to estimate the surface ice stresses. Modeling results underlined the role of the residual strain in determining both the principal stress and the stress perpendicular to and parallel with the dam face. The residual strain is probably the reason why the observed ice stress is always much lower than the single thermal stress. (C) 2018 American Society of Civil Engineers.
  • Leino, Katri; Lampilahti, Janne; Poutanen, Pyry; Väänänen, Riikka; Manninen, Antti; Mazon, Stephany Buenrostro; Dada, Lubna; Franck, Anna; Wimmer, Daniela; Aalto, Pasi P.; Ahonen, Lauri R.; Enroth, Joonas; Kangasluoma, Juha; Keronen, Petri; Korhonen, Frans; Laakso, Heikki; Matilainen, Teemu; Siivola, Erkki; Manninen, Hanna E.; Lehtipalo, Katrianne; Kerminen, Veli-Matti; Petäjä, Tuukka; Kulmala, Markku (2019)
    This work presents airborne observations of sub-3 nm particles in the lower troposphere and investigates new particle formation (NPF) within an evolving boundary layer (BL). We studied particle concentrations together with supporting gas and meteorological data inside the planetary BL over a boreal forest site in Hyytiala, southern Finland. The analysed data were collected during three flight measurement campaigns: May-June 2015, August 2015 and April-May 2017, including 27 morning and 26 afternoon vertical profiles. As a platform for the instrumentation, we used a Cessna 172 aircraft. The analysed flight data were collected horizontally within a 30 km distance from SMEAR II in Hyytiala and vertically from 100 m above ground level up to 2700 m. The number concentration of 1.5-3 nm particles was observed to be, on average, the highest near the forest canopy top and to decrease with increasing altitude during the mornings of NPF event days. This indicates that the precursor vapours emitted by the forest play a key role in NPF in Hyytiala. During daytime, newly formed particles were observed to grow in size and the particle population became more homogenous within the well-mixed BL in the afternoon. During undefined days with respect to NPF, we also detected an increase in concentration of 1.5-3 nm particles in the morning but not their growth in size, which indicates an interrupted NPF process during these undefined days. Vertical mixing was typically stronger during the NPF event days than during the undefined or non-event days. The results shed light on the connection between boundary layer dynamics and NPF.