Possible Approaches in Modelling Rearrangement in a Microstructured Material

2007 ◽  
Vol 340-341 ◽  
pp. 137-142 ◽  
Author(s):  
Salvatore Federico ◽  
Alfio Grillo ◽  
Walter Herzog ◽  
Gaetano Giaquinta ◽  
Shōji Imatani
Keyword(s):  
Biological Tissues ◽  
Unit Vector ◽  
Structural Elements ◽  
Continuum Approach ◽  
Collagen Fibres ◽  
Primary Interest ◽  
Surrounding Matrix ◽  
External Forces ◽  
Microstructured Material

Biological materials can be regarded as composites with spheroidal and fibre-like inclusions, representing cells and collagen fibres, respectively. The orientation and arrangement of the inclusions in a biological tissue is crucial to the determination of the mechanical properties of the material. Furthermore, the reorientation and rearrangement of the inclusions due to the deformation and external forces is of primary interest when dealing with growth and remodelling. We propose to look at the presence of inclusions as a source of internal hyperstaticity: when the material undergoes deformation, a generic inclusion is drifted by the deformation, but at the same time it “feels” the stress field and tends to carry a portion of stress proportional to its stiffness relative to that of the surrounding matrix. With this assumption, we can extend the classical “drift” evolution law for the unit vector field, in order to take the hyperstaticity into account. This method might be used in the description of remodelling in disordered media, such as biological tissues, and may be extended to investigate the reorientation of preferred directions of micro-structural elements in media described with a continuum approach.

Simultaneous Determination of Imatinib and N-Desmethyl Imatinib in Rat Plasma and Tissues Using LC-MS/MS

2019 ◽  
Vol 15 (2) ◽  
pp. 121-129
Author(s):  
Zhi Rao ◽  
Bo-xia Li ◽  
Yong-Wen Jin ◽  
Wen-Kou ◽  
Yan-rong Ma ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Oral Administration ◽  
Parent Drug ◽  
Gradient Elution ◽  
Biological Tissues ◽  
Rat Plasma ◽  
Running Water ◽  
Liver And Kidney ◽  
The Brain

Background: Imatinib (IM) is a chemotherapy medication metabolized by CYP3A4 to Ndesmethyl imatinib (NDI), which shows similar pharmacologic activity to the parent drug. Although methods for determination of IM and/or NDI have been developed extensively, only few observations have been addressed to simultaneously determine IM and NDI in biological tissues such as liver, kidney, heart, brain and bone marrow. Methods: A validated LC-MS/MS method was developed for the quantitative determination of imatinib (IM) and N-desmethyl imatinib (NDI) from rat plasma, bone marrow, brain, heart, liver and kidney. The plasma samples were prepared by protein precipitation, and then the separation of the analytes was achieved using an Agilent Zorbax Eclipse Plus C18 column (4.6 × 100 mm, 3.5 µm) with gradient elution running water (A) and methanol (B). Mass spectrometric detection was achieved by a triplequadrupole mass spectrometer equipped with an electrospray source interface in positive ionization mode. Results: This method was used to investigate the pharmacokinetics and the tissue distributions in rats following oral administration of 25 mg/kg of IM. The pharmacokinetic profiles suggested that IM and NDI are disappeared faster in rats than human, and the tissue distribution results showed that IM and NDI had good tissue penetration and distribution, except for the brain. This is the first report about the large penetrations of IM and NDI in rat bone marrow. Conclusion: The method demonstrated good sensitivity, accuracy, precision and recovery in assays of IM and NDI in rats. The described assay was successfully applied for the evaluation of pharmacokinetics and distribution in the brain, heart, liver, kidney and bone marrow of IM and NDI after a single oral administration of IM to rats.

scholarly journals An Improved Methodology for Determination of Fluorine in Biological Samples Using High-Resolution Molecular Absorption Spectrometry via Gallium Fluorine Formation in a Graphite Furnace

2021 ◽  
Vol 11 (12) ◽  
pp. 5493
Author(s):  
Andrzej Gawor ◽  
Andrii Tupys ◽  
Anna Ruszczyńska ◽  
Ewa Bulska
Keyword(s):  
High Resolution ◽  
Limit Of Detection ◽  
Graphite Furnace ◽  
Absorption Spectrometry ◽  
Biological Tissues ◽  
Biologically Active ◽  
Molecular Absorption ◽  
Biological Origin ◽  
Molecular Absorption Spectrometry

Nowadays growing attention is paid to the control of fluorine content in samples of biological origin as it is present in the form of various biologically active organic compounds. Due to the chemically-rich matrix of biological tissues, the determination of fluorine becomes a very difficult task. Furthermore, a required complex sample preparation procedure makes the determination of the low contents of F by ion chromatography UV-Vis or ion-selective electrodes not possible. High-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) seems to be the best option for this purpose due to its high robustness to matrix interferences, especially in the presence of carefully selected modifiers. In this work the possibility of quantitative F determination in water and animal tissues was examined by measuring the molecular absorption of gallium monofluoride (GaF) at 211.248 nm with the use of a commercially available HR-CS GF MAS system. Experimental conditions for the sensitive and precise determination of fluorine were optimized, including the time/temperature program as well as addition of gallium and modifier mixture in combined mode. Under these conditions the fluoride present in the sample was stabilized up to 600 °C, and the optimum vaporization temperature for GaF was 1540 °C. Palladium and zirconium deposited onto the graphite surface served as solid modifiers; sodium acetate and ruthenium modifiers were added directly to the sample. The limit of detection and the characteristic mass of the method were 0.43 μg/L and 8.7 pg, respectively. The proposed procedure was validated by the use of certified reference materials (CRMs) of lake water and animal tissue; the acceptable recovery was obtained, proving that it can be applied for samples with a similar matrix.

scholarly journals Structural design principles for specific ultra-high affinity interactions between colicins/pyocins and immunity proteins

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Avital Shushan ◽  
Mickey Kosloff
Keyword(s):  
Protein Interactions ◽  
Structural Elements ◽  
Protein Protein Interactions ◽  
Immunity Protein ◽  
Rational Engineering ◽  
High Affinity ◽  
Comparative Structure ◽  
Polar Interactions ◽  
Exquisite Specificity

AbstractThe interactions of the antibiotic proteins colicins/pyocins with immunity proteins is a seminal model system for studying protein–protein interactions and specificity. Yet, a precise and quantitative determination of which structural elements and residues determine their binding affinity and specificity is still lacking. Here, we used comparative structure-based energy calculations to map residues that substantially contribute to interactions across native and engineered complexes of colicins/pyocins and immunity proteins. We show that the immunity protein α1–α2 motif is a unique structurally-dissimilar element that restricts interaction specificity towards all colicins/pyocins, in both engineered and native complexes. This motif combines with a diverse and extensive array of electrostatic/polar interactions that enable the exquisite specificity that characterizes these interactions while achieving ultra-high affinity. Surprisingly, the divergence of these contributing colicin residues is reciprocal to residue conservation in immunity proteins. The structurally-dissimilar immunity protein α1–α2 motif is recognized by divergent colicins similarly, while the conserved immunity protein α3 helix interacts with diverse colicin residues. Electrostatics thus plays a key role in setting interaction specificity across all colicins and immunity proteins. Our analysis and resulting residue-level maps illuminate the molecular basis for these protein–protein interactions, with implications for drug development and rational engineering of these interfaces.

scholarly journals Investigation of a Stochastic Inverse Method to Estimate an External Force: Applications to a Wave-Structure Interaction

2012 ◽  
Vol 2012 ◽  
pp. 1-25 ◽  
Author(s):  
S. L. Han ◽  
Takeshi Kinoshita
Keyword(s):  
External Force ◽  
Inverse Method ◽  
Inverse Function ◽  
Wave Structure ◽  
Dynamic Responses ◽  
Structure Interaction ◽  
External Forces ◽  
Interaction Problem ◽  
Wave Structure Interaction

The determination of an external force is a very important task for the purpose of control, monitoring, and analysis of damages on structural system. This paper studies a stochastic inverse method that can be used for determining external forces acting on a nonlinear vibrating system. For the purpose of estimation, a stochastic inverse function is formulated to link an unknown external force to an observable quantity. The external force is then estimated from measurements of dynamic responses through the formulated stochastic inverse model. The applicability of the proposed method was verified with numerical examples and laboratory tests concerning the wave-structure interaction problem. The results showed that the proposed method is reliable to estimate the external force acting on a nonlinear system.

scholarly journals Non-invasive determination of external forces in vortex-pair-cylinder interactions

2012 ◽  
Vol 24 (6) ◽  
pp. 061903 ◽  
Author(s):  
D. Hartmann ◽  
W. Schröder ◽  
B. N. Shashikanth
Keyword(s):  
Vortex Pair ◽  
Non Invasive ◽  
External Forces

Study of the residual imperfections using methods of probability theory

2021 ◽  
Vol 87 (9) ◽  
pp. 44-49
Author(s):  
D. A. Kuzmin
Keyword(s):  
Probability Theory ◽  
Generalized Equation ◽  
Structural Elements ◽  
Non Destructive Testing ◽  
Operational Control ◽  
Destructive Testing ◽  
Control Procedures ◽  
Non Destructive ◽  
A Current

Discontinuities in the products that occur during manufacture, mounting or upon operation can be missed during non-destructive testing which do not provide their complete detectability at a current level of the technology. Therefore, it is necessary to take into account that certain structural elements may have discontinuities of significant dimensions. We present the results of using the methods of probability theory in studying the residual imperfections that remains in the structure after non-destructive control and repair of the previously identified defects. We used the results of operational control of units carried out by ultrasonic and radiographic methods. We present a method for determining a multifactorial coefficient that takes into account the detectability of defects, the number of control procedures and the errors in the instrumentation and methodological support, as well as a generalized equation for the probability distribution of detecting discontinuities. The developed approach provides assessing of the level of damage to the studied objects, their classification proceeding from the quantitative data and determination of the values of postulated discontinuities for deterministic calculations. The results obtained can be used to improve the methods of monitoring NPP facilities.

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