scholarly journals Incorporation of Molecular Reorientation into Modeling Surface Pressure-Area Isotherms of Langmuir Monolayers

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4372
Author(s):  
José Agudelo ◽  
Guilherme Volpe Bossa ◽  
Sylvio May
Keyword(s):  
Surface Pressure ◽  
Lateral Pressure ◽  
Langmuir Monolayers ◽  
High Energy ◽  
Cross Sectional Area ◽  
Inorganic Nanoparticles ◽  
Sectional Area ◽  
Molecular Reorientation ◽  
Cross Sectional ◽  
Pressure Area

Langmuir monolayers can be assembled from molecules that change from a low-energy orientation occupying a large cross-sectional area to a high-energy orientation of small cross-sectional area as the lateral pressure grows. Examples include cyclosporin A, amphotericin B, nystatin, certain alpha-helical peptides, cholesterol oxydation products, dumbbell-shaped amphiphiles, organic–inorganic nanoparticles and hybrid molecular films. The transition between the two orientations leads to a shoulder in the surface pressure-area isotherm. We propose a theoretical model that describes the shoulder and can be used to extract the energy cost per molecule for the reorientation. Our two-state model is based on a lattice–sublattice approximation that hosts the two orientations and a corresponding free energy expression which we minimize with respect to the orientational distribution. Inter-molecular interactions other than steric repulsion are ignored. We provide an analysis of the model, including an analytic solution for one specific lateral pressure near a point of inflection in the surface pressure-area isotherm, and an approximate solution for the entire range of the lateral pressures. We also use our model to estimate energy costs associated with orientational transitions from previously reported experimental surface pressure-area isotherms.

Left ventricular wave speed

2001 ◽  
Vol 91 (6) ◽  
pp. 2531-2536 ◽  
Author(s):  
Jiun-Jr Wang ◽  
Kim H. Parker ◽  
John V. Tyberg
Keyword(s):  
Wave Speed ◽  
Pulse Generator ◽  
Diastolic Pressure ◽  
Left Ventricular ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Pressure Transducers ◽  
Pressure Area ◽  
Axis Length

Left ventricular (LV) wave speed (LVWS) was studied experimentally and confirmed in theory. Combining the definition of elastance (E) with the equations for the conservation of mass and momentum shows that LVWS is proportional to the square root of E LA, where L is long-axis length and A is the cross-sectional area, and the density of the blood. (We defined E LA = γ, where γ is compressibility.) We studied nine open chest, anesthetized dogs, three of which were studied during caval constriction when LV end-diastolic pressure was ≤0 mmHg. The hearts were paced at ∼90 beats/min, and LV cross-sectional area was measured by using two pairs of ultrasonic crystals; E was calculated from the LV pressure-area loop. A pulse generator was connected to the LV apex, and LVWS was measured by using two pressure transducers: one near the apex and the other near the base. Their distance was measured roentgenographically and compared with the diameter of a reference ball. LVWS ranged from ∼1 m/s during diastole to ∼10 m/s during systole. The slope of the log c(where c is wave speed) vs. log γ was 0.546, which is in agreement with theory (0.5). When γ ≤ 0, LVWS was ∼1.5 m/s.

The Use of a Laser Micrometer System to Determine the Cross-Sectional Shape and Area of Ligaments: A Comparative Study With Two Existing Methods

1990 ◽  
Vol 112 (4) ◽  
pp. 426-431 ◽  
Author(s):  
Savio L.-Y. Woo ◽  
Michael I. Danto ◽  
Karen J. Ohland ◽  
Thay Q. Lee ◽  
Peter O. Newton
Keyword(s):  
Constant Pressure ◽  
Cruciate Ligament ◽  
Applied Pressure ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Proximal Site ◽  
Pressure Area ◽  
The Cross ◽  
Sectional Shape

Determination of the tensile stresses in ligaments and tendons during uniaxial loading depends on accurate measurement of the cross-sectional area. In this study, a laser micrometer system was employed to evaluate the cross-sectional shape and area of the medial collateral ligament (MCL) at three locations and anterior cruciate ligament (ACL). In a New Zealand White (NZW) rabbit, morphologic sections of the ligaments were made to verify the cross-sectional shape reconstructed by the laser micrometer system. The areas obtained by the laser micrometer system from ten additional NZW rabbits were compared with those obtained by two other methods commonly used to measure the cross-sectional area of ligaments and tendons: one method uses digital calipers and the other a constant pressure (0.12 MPa) area micrometer. For the MCL, the digital calipers yielded results very similar to those of the laser micrometer, but the constant pressure area micrometer yielded values 20 percent lower. The area measured at the proximal site of the MCL was 13 percent greater than the area measured at the joint line and distal line. For the ACL, the values obtained by the digital calipers and constant pressure area micrometer were 16 and 20 percent lower, respectively. Because of the irregular shape exhibited by the rabbit ACL, the digital calipers could not accurately measure the crosssectional area. The constant pressure area micrometer yielded lower values for the cross-sectional area of both the MCL and ACL, presumably due to the applied pressure which caused changes in both the cross-sectional shape and area.

Advancement of the mandible improves velopharyngeal airway patency

1995 ◽  
Vol 79 (6) ◽  
pp. 2132-2138 ◽  
Author(s):  
S. Isono ◽  
A. Tanaka ◽  
Y. Sho ◽  
A. Konno ◽  
T. Nishino
Keyword(s):  
Static Pressure ◽  
Video Recording ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Airway Patency ◽  
Pharyngeal Airway ◽  
Obstructive Sleep ◽  
Pressure Area ◽  
Nasal Pressure

The velopharynx is the most common site of obstruction in patients with obstructive sleep apnea (OSA). Advancement of the mandible effectively reverses the pharyngeal obstruction. Accordingly, we hypothesized that mandibular advancement increases cross-sectional area of several segments of the upper airway, including the velopharynx and the oropharynx. We examined the pressure-area properties of the pharyngeal airway in 13 patients with OSA. Under general anesthesia and total muscle paralysis, the pharynx was visualized with an endoscope connected to a video-recording system. During an experimentally induced apnea, we manipulated the nasal pressure from 20 cmH2O to the point of total closure at the velopharynx. The procedure was repeated after maximal forward displacement of the mandible. Measurements of the cross-sectional area at different levels of nasal pressure allowed construction of a static pressure-area relationship of the “passive pharynx,” where active neuromuscular factors are suppressed. In 12 of 13 patients with OSA, advancement of the mandible stabilized the airway by reducing the closing pressure and increasing the area at any airway pressure. Thus the maneuver shifted the static pressure-area curve of the velopharynx and the oropharynx upward in these patients. We conclude that anterior movement of the mandible widens the retropalatal airway as well as that at the base of the tongue in the passive pharynx of OSA patients.

scholarly journals Design and Numerical Simulation of In-Situ Pyrolysis of Oil Shale Through Horizontal Well Fracturing with Nitrogen Injection

2021 ◽  
Vol 39 (2) ◽  
pp. 417-423
Author(s):  
Pengfei Jiang ◽  
Danlei Zhang ◽  
Bin Li ◽  
Chao Song
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Oil Shale ◽  
Horizontal Well ◽  
High Energy ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Shale Formation

An in-situ pyrolysis technology was proposed for shallow oil shale: drilling horizontal wells to the oil shale formation, connecting the horizontal well sections through hydraulic fracturing, injecting nitrogen from the surface to bottomhole, heating up the nitrogen to a high temperature at the bottom, and directly using the high-temperature nitrogen for oil shale pyrolysis. Then, a mathematical model was established for the heat transfer within the oil shale, and a simplified physical model was created for in-situ pyrolysis of oil shale, and used to simulate the heat transfer process. The simulation results show that, with the extension of heating time, the area of effectively pyrolyzed oil shale formation took up an increasingly large proportion of the total cross-sectional area of the formation; however, the increase of the pyrolysis area ratio was rather slow, and the temperature was unevenly distributed in the formation after a long duration of heating. Therefore, the 300d in-situ heating was split into two stages: 250d of heating in the heating well and 50d of heating in the production well. The two-stage heating maximized the heating area of oil shale, and heated 57% of the cross-sectional area up to 400℃, ensuring the effectiveness of pyrolysis. Moreover, this heating scheme ensured an even distribution of temperature in oil shale formation, a high energy utilization, and a desirable heating effect.

Lateral Position Decreases Collapsibility of the Passive Pharynx in Patients with Obstructive Sleep Apnea

2002 ◽  
Vol 97 (4) ◽  
pp. 780-785 ◽  
Author(s):  
Shiroh Isono ◽  
Atsuko Tanaka ◽  
Takashi Nishino
Keyword(s):  
Obstructive Sleep Apnea ◽  
Sleep Apnea ◽  
Static Pressure ◽  
Lateral Position ◽  
Cross Sectional Area ◽  
The Body ◽  
Sectional Area ◽  
Cross Sectional ◽  
Obstructive Sleep ◽  
Pressure Area

Background Reduction of nocturnal obstructive events during lateral position in patients with obstructive sleep apnea was previously reported. However, little information is available regarding mechanisms of the improvement and the precise pharyngeal site influenced by the lateral position. The authors tested the hypothesis that structural properties of the passive pharynx change by changing the body position from supine to lateral. Method Total muscle paralysis was induced with general anesthesia in eight patients with obstructive sleep apnea, eliminating neuromuscular factors contributing to pharyngeal patency. The cross-sectional area of the pharynx was measured endoscopically at different static airway pressures. Comparison of static pressure-area plot between the positions allowed assessment of the influence of the position change on the mechanical properties of the pharynx. Results The static pressure-area curves of the lateral position were above those of the supine position, with increasing maximum cross-sectional area and decreasing the closing pressure at both retropalatal and retroglossal airways. Conclusions Lateral position structurally improves maintenance of the passive pharyngeal airway in patients with obstructive sleep apnea.

Pelvic Canal Narrowing Caused by Triple Pelvic Osteotomy in the Dog

1994 ◽  
Vol 07 (03) ◽  
pp. 110-113 ◽  
Author(s):  
D. L. Holmberg ◽  
M. B. Hurtig ◽  
H. R. Sukhiani
Keyword(s):  
Postoperative Complications ◽  
Pelvic Osteotomy ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Canal Width ◽  
Operative Complications ◽  
Post Operative Complications

SummaryDuring a triple pelvic osteotomy, rotation of the free acetabular segment causes the pubic remnant on the acetabulum to rotate into the pelvic canal. The resulting narrowing may cause complications by impingement on the organs within the pelvic canal. Triple pelvic osteotomies were performed on ten cadaver pelves with pubic remnants equal to 0, 25, and 50% of the hemi-pubic length and angles of acetabular rotation of 20, 30, and 40 degrees. All combinations of pubic remnant lengths and angles of acetabular rotation caused a significant reduction in pelvic canal-width and cross-sectional area, when compared to the inact pelvis. Zero, 25, and 50% pubic remnants result in 15, 35, and 50% reductions in pelvic canal width respectively. Overrotation of the acetabulum should be avoided and the pubic remnant on the acetabular segment should be minimized to reduce postoperative complications due to pelvic canal narrowing.When performing triple pelvic osteotomies, the length of the pubic remnant on the acetabular segment and the angle of acetabular rotation both significantly narrow the pelvic canal. To reduce post-operative complications, due to narrowing of the pelvic canal, overrotation of the acetabulum should be avoided and the length of the pubic remnant should be minimized.

DETERMINATION OF THE FUNCTION OF THE ROD’S CROSS-SECTIONAL AREA USING VIBRATION EIGENFREQUENCIES

2020 ◽  
Vol 0 (4) ◽  
pp. 19-24
Author(s):  
I.M. UTYASHEV ◽  
◽  
A.A. AITBAEVA ◽  
A.A. YULMUKHAMETOV ◽  
◽  
...  
Keyword(s):  
Cross Sectional Area ◽  
Variable Cross ◽  
Sectional Area ◽  
Longitudinal Vibrations ◽  
Cross Sectional ◽  
Method Error ◽  
Various Boundary Conditions ◽  
Elastic Fixation ◽  
Crosssectional Area

The paper presents solutions to the direct and inverse problems on longitudinal vibrations of a rod with a variable cross-sectional area. The law of variation of the cross-sectional area is modeled as an exponential function of a polynomial of degree n . The method for reconstructing this function is based on representing the fundamental system of solutions of the direct problem in the form of a Maclaurin series in the variables x and λ. Examples of solutions for various section functions and various boundary conditions are given. It is shown that to recover n unknown coefficients of a polynomial, n eigenvalues are required, and the solution is dual. An unambiguous solution was obtained only for the case of elastic fixation at one of the rod’s ends. The numerical estimation of the method error was made using input data noise. It is shown that the error in finding the variable crosssectional area is less than 1% with the error in the eigenvalues of longitudinal vibrations not exceeding 0.0001.

Changes in the parameters of nasal breathing and parameters of the upper respiratory tract during orthognathic operations in patients with II and III skeletal class of jaw anomalies

2020 ◽  
pp. 22-27
Author(s):  
S.Sh. Gammadaeva ◽  
M.I. Misirkhanova ◽  
A.Yu. Drobyshev
Keyword(s):  
Respiratory Tract ◽  
Nasal Cavity ◽  
Nasal Septum ◽  
Cross Sectional Area ◽  
Upper Respiratory Tract ◽  
Sectional Area ◽  
Nasal Breathing ◽  
Cross Sectional ◽  
Skeletal Class ◽  
Upper Respiratory

The study analyzed the functional parameters of nasal breathing, linear parameters of the nasal aperture, nasal cavity and nasopharynx, volumetric parameters of the upper airways in patients with II and III skeletal class of jaw anomalies before and after orthognathic surgery. The respiratory function of the nose was assessed using a rhinomanometric complex. According to rhinoresistometry data, nasal resistance and hydraulic diameter were assessed. According to the data of acoustic rhinometry, the minimum cross-sectional area along the internal valve, the minimum cross-sectional area on the head of the inferior turbinate and nasal septum and related parameters were estimated. According to the CBCT data, the state of the nasal septum, the inferior turbinates, the nasal aperture, the state of the nasal cavity, and the linear values of the upper respiratory tract (nasopharynx) were analyzed. The patients were divided into 4 groups according to the classification of the patency of the nasal passages by

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