scholarly journals Output of a valveless Liebau pump with biologically relevant vessel properties and compression frequencies

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Rubina Davtyan ◽  
Narine A. Sarvazyan
Keyword(s):  
Soft Tissues ◽  
Nearest Neighbor ◽  
Young Modulus ◽  
Biologically Relevant ◽  
Carbon Particles ◽  
Unidirectional Flow ◽  
Valveless Pumping ◽  
Attachment Sites ◽  
Peristaltic Pumps ◽  
Valveless Pumps

AbstractLiebau pump is a tubular, non-peristaltic, pulsatile pump capable of creating unidirectional flow in the absence of valves. It requires asymmetrical positioning of the pincher relative to the attachment sites of its elastic segment to the rest of the circuit. Biological feasibility of such valveless pumps remains a hotly debated topic. To test the feasibility of the Liebau-based pumping in vessels with biologically relevant properties we quantified the output of Liebau pumps with their  compliant segments made of a silicone rubber that mimicked the Young modulus of soft tissues. The lengths, the inner diameters, thicknesses of the tested compliant segments ranged from 1 to 5 cm, 3 to 8 mm and 0.3 to 1 mm, respectively. The compliant segment of the setup was compressed at 0.5–2.5 Hz frequencies using a 3.5-mm-wide rectangular piston. A nearest-neighbor tracking algorithm was used to track movements of 0.5-mm carbon particles within the system. The viscosity of the aqueous solution was varied by increased percentage of glycerin. Measurements yielded quantitative relationships between viscosity, frequency of compression and the net flowrate. The use of the Liebau principle of valveless pumping in conjunction with physiologically sized vessel and contraction frequencies yields flowrates comparable to peristaltic pumps of the same dimensions. We conclude that the data confirm physiological feasibility of Liebau-based pumping and warrant further testing of its mechanism using excised biological conduits or tissue engineered components. Such biomimetic pumps can serve as energy-efficient flow generators in microdevices or to study the function of embryonic heart during its normal development or in diseased states.

scholarly journals Thermodynamic and Elastic Properties of Interstitial Alloy FeC with BCC Structure at Zero Pressure

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Bui Duc Tinh ◽  
Nguyen Quang Hoc ◽  
Dinh Quang Vinh ◽  
Tran Dinh Cuong ◽  
Nguyen Duc Hien
Keyword(s):  
Nearest Neighbor ◽  
Young Modulus ◽  
Thermodynamic Quantities ◽  
Atom Concentration ◽  
Main Metal ◽  
Special Cases ◽  
Analytic Expressions ◽  
Rigidity Modulus ◽  
Bcc Structure ◽  
The Mean

The analytic expressions for the thermodynamic and elastic quantities such as the mean nearest neighbor distance, the free energy, the isothermal compressibility, the thermal expansion coefficient, the heat capacities at constant volume and at constant pressure, the Young modulus, the bulk modulus, the rigidity modulus, and the elastic constants of binary interstitial alloy with body-centered cubic (BCC) structure, and the small concentration of interstitial atoms (below 5%) are derived by the statistical moment method. The theoretical results are applied to interstitial alloy FeC in the interval of temperature from 100 to 1000 K and in the interval of interstitial atom concentration from 0 to 5%. In special cases, we obtain the thermodynamic quantities of main metal Fe with BCC structure. Our calculated results for some thermodynamic and elastic quantities of main metal Fe and alloy FeC are compared with experiments.

Effects of soft tissue artefacts on computed segmental and stifle kinematics in canine motion analysis

2019 ◽  
Vol 186 (2) ◽  
pp. 66-66 ◽  
Author(s):  
Ming Lu ◽  
Cheng-Chung Lin ◽  
Tung-Wu Lu ◽  
Shi-Nuan Wang ◽  
Ching-Ho Wu
Keyword(s):  
Soft Tissue ◽  
Motion Analysis ◽  
Soft Tissues ◽  
Functional Performance ◽  
Frontal Plane ◽  
Skin Marker ◽  
Attachment Sites ◽  
Mixed Breed ◽  
Dynamic Gait ◽  
Cluster Level

Skin marker-based motion analysis has been widely used to evaluate the functional performance of canine gait and posture. However, the interference of soft tissues between markers and the underlying bones (soft tissue artefacts, STAs) may lead to errors in kinematics measurements. Currently, no optimal marker attachment sites and cluster compositions are recommended for canine gait analysis. The current study aims to evaluate cluster-level STAs and the effects of cluster compositions on the computed stifle kinematics. Ten mixed-breed healthy dogs affixed with 19 retroreflective markers on the thigh and shank were enrolled. During isolated stifle passive extension, the marker trajectories were acquired with a motion capture system, and the skeletal poses were determined by integrating fluoroscopic and CT images of the bones. The cluster-level STAs were assessed, and clusters were paired to calculate the stifle kinematics. A selection of cluster compositions was useful for deriving accurate sagittal and frontal plane stifle kinematics with flexion angles below 50 per cent of the range of motion. The findings contribute to improved knowledge of canine STAs and their influence on motion measurements. The marker composition with the smallest error in describing joint kinematics is recommended for future applications and study in dogs during dynamic gait assessment.

Characterization of carbon aerogels by transport measurements

1993 ◽  
Vol 8 (8) ◽  
pp. 1875-1885 ◽  
Author(s):  
A.W.P. Fung ◽  
Z.H. Wang ◽  
K. Lu ◽  
M.S. Dresselhaus ◽  
R.W. Pekala
Keyword(s):  
Raman Scattering ◽  
Temperature Dependence ◽  
Nearest Neighbor ◽  
Negative Temperature ◽  
Carbon Aerogels ◽  
Free Carriers ◽  
Carbon Particles ◽  
Microcellular Foams ◽  
Temperature Coefficient Of Resistivity

Carbon aerogels are a special class of low-density microcellular foams. These materials are composed of interconnected carbon particles with diameters of approximately 10 nm. The temperature dependence of the dc electrical resistivity and magnetic susceptibility (χ) from 4 K to room temperature, magnetoresistance (MR) in a magnetic field up to 15 T, and Raman scattering were measured as a function of aerogel density. While Raman scattering measurements are not sensitive to variations in density, the χ data show that there are more free carriers in samples of higher density. Aerogel samples with different densities all show a negative temperature coefficient of resistivity and a positive MR. The less dense samples exhibit a stronger temperature dependence of resistivity and a stronger field dependence of the MR, indicating that with decreasing density and increasing porosity, charge carriers are more localized. Data analysis precludes variable-range hopping in favor of nearest-neighbor hopping and fluctuation-induced tunneling as the most likely conduction mechanisms for carbon aerogels.

Elastic Moduli and Elastic Constants of Alloy AuCuSi With FCC Structure Under Pressure

2019 ◽  
Vol 38 (2019) ◽  
pp. 264-272 ◽  
Author(s):  
Nguyen Quang Hoc ◽  
Bui Duc Tinh ◽  
Nguyen Duc Hien
Keyword(s):  
Elastic Constants ◽  
Elastic Moduli ◽  
Nearest Neighbor ◽  
Young Modulus ◽  
Numerical Results ◽  
Main Metal ◽  
Substitution Alloy ◽  
Rigidity Modulus ◽  
The Mean ◽  
Fcc Structure

AbstractThis paper studies on the dependence of the mean nearest neighbor distance, the Young modulus E, the bulk modulus K, the rigidity modulus G and the elastic constants C11, C12, C44 on temperature, pressure, the concentration of substitution atoms and the concentration of interstitial atoms for alloy AuCuSi (substitution alloy AuCu with interstitial atom Si) with FCC structure by the way of the statistical moment method (SMM). The numerical results for alloy AuCuSi are compared with the numerical results for main metal Au, substitution alloy AuCu, interstitial alloy AuSi, other calculated results and experiments.

scholarly journals STUDY ON ELASTIC DEFORMATION OF INTERSTITIAL ALLOY FeCWITH BCC STRUCTURE UNDER PRESSURE

2019 ◽  
Vol 35 (1) ◽  
Author(s):  
Hiền Nguyễn Đức ◽  
Hoc Quang Nguyen ◽  
Cuong Dinh Tran
Keyword(s):  
Elastic Deformation ◽  
Nearest Neighbor ◽  
Young Modulus ◽  
Numerical Results ◽  
Main Metal ◽  
Analytic Expressions ◽  
Rigidity Modulus ◽  
Bcc Structure ◽  
The Mean ◽  
Special Case

The analytic expressions of the free energy, the mean nearest neighbor distance between two atoms, the elastic moduli such as the Young modulus E, the bulk modulus K, the rigidity modulus G and the elastic constants C11, C12, C44 for  interstitial alloy AB with BCC structure under pressure are derived from the statistical moment method. The elastic deformations of main metal A is special case of elastic deformation for interstitial alloy AB. The theoretical results are applied to alloy FeC under pressure. The numerical results for this alloy are compared with the numerical results for main metal Fe  and experiments.

scholarly journals Isometry of Potential Attachment Sites for the Iliotrochanteric Suture in Dogs: an ex vivo Study

2020 ◽  
Vol 48 ◽  
Author(s):  
Cristiane Alves Cintra ◽  
Luís Gustavo Gosuen Gonçalves Dias ◽  
Fernanda Gosuen Gonçalves Dias ◽  
Danyelle Rayssa Cintra Ferreira ◽  
Lucas De Freitas Pereira ◽  
...  
Keyword(s):  
Soft Tissues ◽  
Surgical Techniques ◽  
Vertical Axis ◽  
Central Point ◽  
Neutral Position ◽  
Joint Movement ◽  
Caudal Portion ◽  
Attachment Sites ◽  
Suture Tension ◽  
Hip Extension

Background: Coxofemoral luxation is the most common traumatic luxation in dogs and the iliotrochanteric suture is one of the surgical treatment options. The orthopedic suture aimed at surgically restoring joint movement should be employed in an isometric manner in order to maintain adequate tension throughout the arc of motion. This study aimed to determine the isometric points for the iliotrochanteric suture in dogs during the joint extension and flexion movements. This evaluation was performed both in the intact hip joint and in the luxation model, establishing the best combination, among the determined points, for the reestablishment of normal joint movement.Materials, Methods & Results: Radiographic analyses of 12 canine cadaveric hips, both intact and in craniodorsal luxation model, were performed in a neutral position, flexion at 50°, and extension at 150°. In the trochanteric segment, two parallel lines were drawn, creating the central vertical axis and the secondary vertical axis. Three points were then determined on each axis, from proximal to distal, corresponding to 25, 50, and 75% of the height of the axis, and were labelled as T1, T2, and T3 and T4, T5, and T6, respectively. In the iliac segment, a line perpendicular to the longitudinal axis of the ilium was drawn, and 25, 50, and 75% of this height corresponded to points I1, I2, and I3, respectively. The lengths between the points were measured, with the objective of evaluating which combination of points presented less variation in the joint positions. The central location of the iliac and trochanteric segments, determined respectively by I2 and T2, provided smaller variations during the maximal movements of hip flexion and extension.Discussion: The surgical techniques of iliotrochanteric suture target to maintain the internal rotation of the femoral head inside the acetabulum and abduction of the femur until the soft tissues have healed. The described techniques for the iliotrochanteric suture present a great anatomical variety in the arrangement of the anchor points of the suture. It is known that if during motion, the attachment sites move closer to one another, the suture will become lax and, if the attachment sites move away from one another, the suture will tighten. Therefore, the implantation in isometric sites assists in reducing the variation of the distance between the points of origin and insertion of the suture during joint movement, keeping the suture tension constant and allowing the functional recovery of the joint. This study demonstrates that there are some locations for the origin and insertion of an iliotrochanteric suture that are associated with less length change than others. I2-T2 combination is the point closest to isometry for the iliotrochanteric suture during hip extension and flexion, so that, T2 is the most central point of the greater trochanter, corresponding to 50% of the height of its central vertical axis, as well as I2, which corresponds to the most central point of the ilium, representing 50% of the height of the most caudal portion of its body. The isometric point found by us details the exact location of perforation in all aspects (height and length), both in the ilium and the trochanter. In addition, it is a personalized point created for each patient from its radiographic examination and taking into consideration its anatomical variations, so that there is no damage to the suture during hip extension and flexion movements.

scholarly journals Nearest-neighbor NMR spectroscopy: categorizing spectral peaks by their adjacent nuclei

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Soumya P. Behera ◽  
Abhinav Dubey ◽  
Wan-Na Chen ◽  
Viviane S. De Paula ◽  
Meng Zhang ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Nearest Neighbor ◽  
Search Space ◽  
Amino Acid Type ◽  
Isoleucine Leucine ◽  
Biologically Relevant ◽  
Additional Information ◽  
Acid Type ◽  
Distance Restraints ◽  
Spectral Peaks

Abstract Methyl-NMR enables atomic-resolution studies of structure and dynamics of large proteins in solution. However, resonance assignment remains challenging. The problem is to combine existing structural informational with sparse distance restraints and search for the most compatible assignment among the permutations. Prior classification of peaks as either from isoleucine, leucine, or valine reduces the search space by many orders of magnitude. However, this is hindered by overlapped leucine and valine frequencies. In contrast, the nearest-neighbor nuclei, coupled to the methyl carbons, resonate in distinct frequency bands. Here, we develop a framework to imprint additional information about passively coupled resonances onto the observed peaks. This depends on simultaneously orchestrating closely spaced bands of resonances along different magnetization trajectories, using principles from control theory. For methyl-NMR, the method is implemented as a modification to the standard fingerprint spectrum (the 2D-HMQC). The amino acid type is immediately apparent in the fingerprint spectrum. There is no additional relaxation loss or an increase in experimental time. The method is validated on biologically relevant proteins. The idea of generating new spectral information using passive, adjacent resonances is applicable to other contexts in NMR spectroscopy.

scholarly journals Physical patient simulators for surgical training: a review

2020 ◽  
Vol 2020 (1) ◽  
pp. 124-128
Author(s):  
Marine Shao ◽  
Carinna Parraman ◽  
David Huson
Keyword(s):  
3D Printing ◽  
Physical Properties ◽  
Surgical Training ◽  
Soft Tissues ◽  
Young Modulus ◽  
3D Models ◽  
Human Anatomy ◽  
Patient Simulators

The purpose of this article is to review the fabrication process of physical patient simulators for surgical training and describes current research areas. Medical image acquisition and analysis are tools to reproduce human anatomy in 3D models. Data acquisition techniques include CT scans, MRI, and ultrasound. Postprocessing of this data is necessary to obtain a file for 3D printing. Two available fabrication methods are direct 3D printing of an organ model and 3D printing a mould to cast an organ replica. Direct 3D printing presents several limitations. Therefore, casting techniques with silicones and hydrogels are better suited for the fabrication of softer tissue models. Surgeons qualitatively evaluate the simulators and their ability to train students. It is also possible to make a quantitative evaluation to compare the properties of the simulators to the physical properties of organs. Different methods exist to measure the physical properties of soft tissues, mainly to find the Young modulus of the soft tissue. The tests can be in vivo, in situ or in vitro. Researchers perform tests on human tissues or animal tissues. The use of surgical simulators has shown satisfactory results in surgical training. Nonetheless, limitations remain, simulators lack realism and are not available for some pathologies. Future work in this area could be of benefit to surgical training.

Internal Pressure of the Human Meniscal Attachments During Physiological and Pathological Loading

2012 ◽  
Author(s):  
Adam C. Abraham ◽  
Kenton R. Kaufman ◽  
Tammy L. Haut Donahue
Keyword(s):  
Soft Tissues ◽  
Load Transfer ◽  
Fluid Pressure ◽  
Mechanical Environment ◽  
Attachment Sites ◽  
Compressive Loads ◽  
Lateral Posterior ◽  
Meniscal Attachments ◽  
Joint Load ◽  
Hoop Stresses

Knee menisci are semi-lunar, fibrocartilaginous structures that convert applied compressive loads to circumferential hoop stresses which are attenuated at the tibial plateau via the meniscal attachments [1]. These specialized interfaces, located at the lateral anterior (LA), lateral posterior (LP), medial anterior (MA), and medial posterior (MP) horns, are crucial to maintaining mechanical functionality of menisci, thereby preventing osteoarthritis [2]. Soft-tissues subjected to compression and shear loads are known to possess proteoglycans, which aid in resisting these applied stresses by retaining interstitial fluid [1]. Interestingly, proteoglycans are also known to be present at the meniscus to bone interface [3]. Despite the presence of these biphasic attachments and their important role in joint load transfer, there have been no quantitative investigations of the mechanical environment within these attachments under physiological and pathological loads. Recent development of a novel pressure microsensor now allows direct observation of fluid pressure, which will aid in understanding the internal mechanical environment within the attachment sites. Previous work indicates that the attachment sites are geometrically, mechanically, and histologically different [4], thus it is hypothesized that the fluid pressures would likewise differ.

scholarly journals Existence and Stability of Periodic Solution Related to Valveless Pumping

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
B. Dorociaková ◽  
M. Michalková ◽  
R. Olach ◽  
M. Sága
Keyword(s):  
Periodic Solution ◽  
Exponential Stability ◽  
Nonlinear Differential Equations ◽  
Sufficient Conditions ◽  
Point Of View ◽  
System Configuration ◽  
Qualitative Properties ◽  
Unidirectional Flow ◽  
Valveless Pumping ◽  
Existence And Stability

Valveless pumping, also known as Liebau effect, can be described as the unidirectional flow of liquid in a system without valves that is caused by the asymmetry of placing of the periodically working pump. Recently, the research in this field has been reevoked, partially due to its possible application in nanotechnologies. In this paper, a configuration of one pipe and one tank is considered from the mathematical point of view. Qualitative properties of a class of nonlinear differential equations that model the assumed system configuration are investigated. New sufficient conditions for the existence of positive T-periodic solutions are given. Correspondingly, exponential stability of periodic solution is treated. Presented results are new. They extend and complement earlier ones in the literature.

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