Differences In Pressure Values Research Articles

Nonlinear Medical Ultrasound Tomography: 3D Modeling of Sound Wave Propagation in Human Tissues

The article aimed to show the fundamental possibility of constructing a computational digital twin of the acoustic tomograph within the framework of a unified physics–mathematical model based on the Navier–Stokes equations. The authors suggested that the size of the modeling area is quite small, sound waves are waves of “small” disturbance, and given that a person consists of more than 60% water, human organs can be modeled using a liquid model, taking into account their density. During numerical experiments, we obtained the pressure registered in the receivers that are located on the side walls of the tomograph. The differences in pressure values are shown depending on the configuration of inclusions in the mannequin imitating internal organs. The results show that the developed technology can be used to probe the human body in medical acoustic tomographs and determine the acoustic parameters of the human body to detect neoplasms.

Conditions of formation and sources of fluids of the birthplace of barren residential quartz of hydrothermal-metamorphogenic-metasomatic and hydrothermal-metamorphogenic genesis (Middle and South Urals)

The paper considers the conditions of quartz formation of hydrothermal-metamorphogenic-metasomatic and hydrothermal-metamorphogenic genesis of deposits and manifestations of the Middle and Southern Urals based on the study of fluid inclusions by methods of thermobarogeochemistry, ion and gas chromatography. It is established that the studied quartz objects are formed in a wide temperature range, against the background of insignificant differences in pressure values. It is shown that the temperatures of mineral formation in deposits of hydrothermal-metamorphogenic-metasomatic genesis vary from 440-230 ° C at a pressure of 1.2-1.4 kbar. The formation of these veins occurred with the participation of K-Mg-Fe-chloride fluid with a salinity of 1.2-8.7 wt. % NaCl-eq., depleted Mg and Fe due to the deposition of magnesia-ferruginous carbonates. A typomorphic feature of hydrothermal-metamorphogenic-metasomatic quartz is the high values of boron associated with the placement of quartz veins among pegmatoids and the presence of boron-containing mineral inclusions on quartz-vein objects. Veins of hydrothermal-metamorphogenic genesis were formed when the crack system was filled with quartz with the participation of a substantially K-Na chloride fluid (0.2-15.5 wt. % NaCl-eq.), at homogenization temperatures of 435-335 ° C and a pressure of 1.3-2.3 kbar. In the composition of fluid inclusions of hydrothermal-metamorphogenic-metasomatic quartz, the sum of "harmful" components (H2O, CO2, CH4, Cl, B, Na, K, Mg and Li) is less than in hydrothermal-metamorphogenic quartz. The studied quartz deposits and veins were formed in the range of temperatures and pressures not higher than the green shale stage during several successive stages: the formation of quartz veins – in a more high-temperature hydrothermal stage, while subsequent changes in quartz veins occurred under the influence of metamorphism processes, with a decrease in temperature. Subsequent changes are associated with the appearance of fracturing, cataclysm and recrystallization of quartz bodies with a decrease in grain size.

Abstract 9538: Comparison of Central Aortic Pressures Obtained Using an Invasive Pressure Catheter and the Noninvasive Sphygmocor Device

Introduction: The SphygmoCor (ATCOR, Naperville, IL) device utilizes a generalized transfer function based on patient’s age and gender to derive the aortic pressure pulse from the brachial-cuff based pressure measurements. This study compared aortic pressures obtained using SphygmoCor with aortic pressures obtained during cardiac catheterization. Hypothesis: Mean differences in aortic pressures obtained using SphygmoCor and pressure catheters will be less than 5 mmHg. Methods: After IRB approval, 136 patients were enrolled. During standard-of-care catheterization procedure, aortic pressure measurements were obtained using fluid-filled catheters. In a subset of patients (n = 13) the aortic pressure values were also obtained using solid-state high-fidelity Millar catheters. Immediately after the catheterization procedure, while the patients were still in the catheterization laboratory (on the procedure table), central aortic pressures were estimated with the SphygmoCor device. The measured and estimated aortic pressures were compared using linear regression and Bland-Altman analysis. A linear fit was performed to derive an additional transfer function to convert SphygmoCor pressure values to catheter-based aortic pressures, and the resulting differences in pressure values were compared. A bootstrap analysis was performed to test the generalizability of this transfer function. Results: Mean differences in systolic, diastolic and pulse aortic pressures obtained using the two techniques ranged from 6.5 to 18.0 mmHg (p < 0.001). In the subset with high-fidelity catheters, the differences ranged from 8.0 to 18.9 mmHg. With the linear-fit transfer function, the differences in systolic, diastolic and pulse aortic pressures were low (< 1 mmHg) corresponding to a reduction in bias noted with Bland-Altman analysis. The bootstrap analysis of the transfer function (100 iterations) achieved a coefficient of variation for the root mean square error < 8.4% for systolic, diastolic and pulse aortic pressures. Conclusions: The magnitude of the differences between the SphygmoCor-estimated and catheter-based systolic, diastolic and pulse aortic pressures reduced considerably after using the linear-fit transfer function derived in this study.

Distribution of Pressures on Modified Stepped Spillway by Using Toothed-Steps

In the present study a new steeped spillway shape at which “toothed steps” have been adopted instead of traditional steps to enhance the amount and distribution of water pressure along the chute of the stepped spillway. Experiments were conducted under a skimming flow regime, on five physical models of spillway one of which consisted of traditional steps used as a base model. For all investigated models, the chute angle was 45° with fourteen steeps each of 3cm height. Generally, the results show that the new shape models enhance the pressure distribution and reducing the potential for negative pressures along the chute, as well as, reducing the values of positive pressures that usually impact the tread. Specifically, close to the crest, the differences in pressure values being clearly large between the toothed steps modelsand the traditional steps. The new configurations of steps reduce the positive pressures between 116.66% to 1.28 % and the negative pressures were generally close to zero.

Plantar Pressure Variations Induced by Experimental Malocclusion-A Pilot Case Series Study.

Background: All body systems involved in ensuring a healthy posture (musculoskeletal system, oculomotor, oto-vestibular and occluso-cranial-mandibular) are essential in maintaining postural balance. Research Question: Does experimental malocclusion in subjects in static position determine variations in plantar pressure? Methods: Overall, 31 subjects were included in the study. The plantar pressure was evaluated in five different points: lateral and medial heel, midfoot, 1st and 5th metatarsal area. Using a specially designed splint, an artificial malocclusion was induced on the right hemimandibular arch. The pressure was measured at 0 (T0), 15 (T1) and 30 min (T2) after splint application. Results: The right external plantar sensors recorded statistically significant differences in pressure values after 15 min of splint wear (5th metatarsal area, p = 0.05; midfoot, p = 0.04). Important pressure values were also recorded by the left internal plantar sensors (1st metatarsal, p = 0.01; medial heel, p = 0.006), after 30 min of splint wear. Conclusions: Asymmetrical experimental malocclusion produces early changes in plantar pressure, a proof of compensatory mechanisms induced by secondary postural imbalance.

Intraocular Pressure Changes After Intravitreal Bevacizumab Injection Alone or Combination of Bevacizumab and Triamcinolone Acetonide

Aim: To evaluate intraocular pressure changes after intravitreal injection of Bevacizumab alone or in combination with Triamcinolone Acetonide. Method: Our study included 63 eyes from the ophthalmology department at Tishreen University Hospital who had vascular retinal diseases. The patients were divided into two groups according to the indication of injection. The first group was injected with bevacizumab (B) at a concentration of 2.5mg / 0.1 ml and the second group was injected with the combination treatment of Triamcinolone Acetonide at a concentration of 2mg / 0.05ml with bevacizumab (B+TA) at a concentration of 1.25mg/ 0.05ml. Intraocular pressure was monitored on the Goldman applanation tonometry and values were recorded as follows: before injection, the second injection day, a week after injection, a month after injection and after three months. Results: The mean values of the intraocular pressure mean increased from the second day of injection in the study groups (B) and (B+TA) and the mean of the IOP values before injection (13.34-13.31 mmHg) respectively, and the IOP values showed the maximum in both groups after a week of the injection (17.81-17.31 mmHg) then began to decrease after a month and three months later to (17.34-17.06mmHg) and (17.6-16.75mmHg) mercury respectively, but they remained higher than they were before the injection, and the number of injections had no effect on intraocular pressure. Conclusion: intravitreal injections with both bevacizumab alone or in combination with triamcinolone acetonide resulted in a rise in intraocular pressure, and differences in pressure values were statistically significant within the same group during the studied time periods but were not statistically significant between the two groups, and the number of injections had no effect on intraocular pressure.

Quantitative measurement of intra-compartmental pressure of the leg in acute traumatic injury: As a routine trend.

Experience and literature regarding complications of lower extremity compartment syndrome led us to hypothesize that delayed diagnosis and limb loss are potentially preventable events. Clinical examination does play a role, but quantification of compartment pressure reading serves as confirmation and determines the need for surgical intervention and provides the only objective data in case of conflict. We performed a prospective study of all cases of closed tibial fractures presenting to our trauma centre over a 3-year period (January 2009-June 2012). Variables reviewed included intra-compartmental pressure readings, location of the fracture and development of subsequent compartment syndrome requiring fasciotomy. Patients were divided into (1) Group A - proximal tibial fracture, (2) Group B - diaphyseal fracture and (3) Group C - Pilon fracture. Values of the injured and uninjured leg were taken and the data analyzed using SPSS version 22. 168 (41 females and 127 males) cases were analyzed. Mean pressure readings of the fractured limb were higher in Group A compared to the other groups. The mean difference in pressure values between the injured and uninjured limb recorded were of 15.1mm Hg (Group A), 13.8mm Hg (Group B) and 13.3mm Hg (Group C). Patients who eventually underwent fasciotomy were 5 (10.8%) in Group A, 8 (10.3%) in Group B and 3 (6.8%) in Group C, and had initial baseline pressure difference of >18.5mm Hg. These data underscore the importance of routine recording of initial intra-compartmental pressure and relation of difference in compartmental pressure between injured and uninjured limb to eventual development of compartment syndrome requiring fasciotomy.

Quantitative measurement of intra-compartmental pressure of the leg in acute traumatic injury: As a routine trend

Background: Experience and literature regarding complications of Lower Extremity Compartment Syndrome led us to hypothesize that delayed diagnosis and limb loss are potentially preventable events. Clinical examination do play role, but quantification of compartment pressure reading serves as confirmation and determines the need of surgical intervention and provides the only objective data in case of conflict. Methods: We performed a prospective study of all cases of closed tibial fractures over a 3 year period (Jan 09 to June 2012) presenting to our trauma center. Variables reviewed included intra-compartmental pressure readings and location of the fracture, development of subsequent compartment syndrome requiring fasciotomy. Patients were divided in to 1) Group A-proximal tibial fracture. 2) Group B- diaphyseal fracture. 3) Group C- pilon fracture. Values of the injured and uninjured leg were taken and the data analysed using spss version 22. Results: 168 (41 female, 127 male) cases were analysed. Mean pressure readings of the fractured limb were higher in group A compared to the other groups. The mean difference in pressure values between the injured and uninjured limb recorded were of 15.1 mm Hg (group A), 13.8 mmHg (group B), 13.3 mm Hg (group C). Patients who eventually underwent fasciotomy were 5(10.8%) in Group A, 8(10.3%), in Group B and 3(6.8%) in Group C had initial baseline pressure difference of ≥ 18.5 mm Hg. Conclusion: These data underscore the importance of routine recording of initial intra-compartmental pressure and relation of difference in compartmental pressure between injured and uninjured limb to eventual development of compartment syndrome requiring fasciotomy.

Effect of oil viscosity on the flow structure and pressure gradient in horizontal oil–water flow

The flow patterns and pressure gradient of immiscible liquids are still subject of immense research interest. This is partly because fluids with different properties exhibit different flow behaviours in different pipe's configurations under different operating conditions. In this study, a combination of oil–water properties (σ=20.1mN/m) not previously reported was used in a 25.4mm acrylic pipe. Experimental data of flow patterns, pressure gradient and phase inversion in horizontal oil–water flow are presented and analyzed together with comprehensive comments. The effect of oil viscosity on flow structure was assessed by comparing the present work data with those of Angeli and Hewitt (2000) and Raj et al. (2005). The comparison revealed several important findings. For example, the water velocity required to initiate the transition to non-stratified flow at low oil velocities increased as the oil viscosity increased while it decreased at higher oil velocities. The formation of bubbly and annular flows and the extent of dual continuous region were found to increase as the oil–water viscosity ratio increased. Dispersed oil in water appeared earlier when oil viscosity decreased.The effect of oil viscosity on pressure gradient was also investigated by comparing the results with Angeli and Hewitt (1998) and Chakrabarti et al. (2005). One of the main findings is the large difference between the pressure gradient results which is attributed to the difference in oil viscosity. The differences between the results become bigger at higher oil velocities. The largest difference in pressure values was observed in flow region where oil is the continuous phase. On the contrary, for dispersed oil in water (Do/w), the pressure gradient values observed at the same conditions are approximately the same. A simple correlation was developed to predict the pressure gradient in this regime. The correlation was validated using new experimental data.Finally, the effect of oil viscosity on pressure gradient prediction was investigated using the two flow model for stratified flow and the homogenous model for oil dispersed in water. Both models showed better prediction for the low oil viscosities.

Influence of wind direction on natural ventilation of apartment buildings

Abstract The paper presents wind tunnel investigations of the influence of wind direction on the natural ventilation of buildings. Tests were carried out on models of an apartment building complex, made to 1:100 scale, consisting of six adjacent buildings, and on a natural-scale isolated roof ventilation shaft outlet. Walls and roof pressure distribution were obtained and difference in pressure values between windows and the ventilation shaft outlets on the roof have been calculated. It was found that some wind directions decrease chimney draught. Aerodynamic interference of neighbouring buildings also decreases chimney draught. The influence of the location of an adjacent building on the ventilation of the building under consideration was tested.

Manometric characteristics of the extrahepatic biliary tract in dogs.

Pressure measurements of the whole extrahepatic biliary tract were performed in dogs using constant perfusion techniques. Studies were done during general anesthesia and in conscious trained dogs. Gallbladder intraluminal fasting pressure was significantly lower than common bile duct pressure. No motor activity was demonstrated in the common bile duct. At the cysticocholedochal junction a static high-pressure zone was observed, probably due to mechanical factors. At the level of the choledochoduodenal junction, a high-pressure zone with a sphincter behavior was demonstrated, with a resting pressure of 38 cm H2O above intraduodenal pressure and with rhythmic contractions with a mean amplitude of 88 cm H2O above duodenal pressure. Duodenal motility was completely different from sphincter dynamics. No differences in pressure values were seen during general anesthesia or in conscious state.