Numerical study of stress-strain state of pelvis at the proximal femur rotation osteotomy

© Sachenkov O.A., Hasanov R.F., Andreev P.S., Konoplev Yu.G., 2016.The relevance of this study is dictated by the high frequency of occurrence of the disease. Among all hip diseases, Legg-Calvé-Perthes disease takes 25-30 % of diseases in childhood. There are no certain and founded recommendations for surgering in general and rotary flexion osteotomies in particular. The study is to determine the stress-strain state of the joint at different directions and magnitudes of the rotation angle. Calculations were carried out by using computer modelling of the hip joint based on localization of degenerative process and the severity of the degeneration of epiphysis in children and adolescents with Legg-Calvé-Perthes diseases. Numerical studies were performed using the finite element method in Nastran Siemens NX. The paper took into account the effect of the following muscles: mm. piriformis, rectus femoris, iliopsoas, obturatorius internus, gluteus minimus, medius et maximus. The calculations allow us to determine the forces produced in the muscles, reactive power and reactive torque acting in the joint at different rotation angles (these values are relevant for assessing the stiffness of external fixation device). The maximum shear stresses and Mises stresses have been identified in the acetabulum and the proximal part of the femur. Evaluation of strength was determined by the maximum shear stresses. So, in the acetabulum with a rotation of 25° forward and rotation of 35° back, the greatest value of maximum shear stress exceeds 1.7 MPa; at the rotation of more than 30° back, the value of similar stress exceeds 6.4 MPa; at forward rotation to 50°, the highest maximum shear stresses reach a value of 5.0 MPa. Thus, when the rotation back to the angle over 30°, maximum shear stresses in the joint region are into the lower critical value, at 35,° they are situated in the upper region of the critical values. When considering forward rotation angle over 25°, maximum shear stresses are into the lower region of the critical values, crossing through the upper region of the critical values at rotation to 50° does not occur

Determination of muscle effort at the proximal femur rotation osteotomy

© Published under licence by IOP Publishing Ltd.The paper formulates the problem of biomechanics of a new method for treatment of Legg-Calve-Perthes disease. Numerical calculations of the rotational flexion osteotomy have been carried out for a constructed mathematical model of the hip joint, taking into account the main set of muscles. The work presents the results of the calculations and their analysis. The results have been compared with the clinical data. The calculations of the reactive forces arising in the acetabulum and the proximal part of the femur allowed us to reveal that this reactive force changes both in value and direction. These data may be useful for assessing the stiffness of an external fixation device used in orthopedic intervention and for evaluating the compression in the joint

Determination of muscle effort at the proximal femur rotation osteotomy

© Published under licence by IOP Publishing Ltd.The paper formulates the problem of biomechanics of a new method for treatment of Legg-Calve-Perthes disease. Numerical calculations of the rotational flexion osteotomy have been carried out for a constructed mathematical model of the hip joint, taking into account the main set of muscles. The work presents the results of the calculations and their analysis. The results have been compared with the clinical data. The calculations of the reactive forces arising in the acetabulum and the proximal part of the femur allowed us to reveal that this reactive force changes both in value and direction. These data may be useful for assessing the stiffness of an external fixation device used in orthopedic intervention and for evaluating the compression in the joint

Effect of the C/N ratio modification on the corrosion behavior and performance of carbonitride coatings prepared by cathodic arc deposition

This study focuses on investigating carbonitride coatings, specifically CNTi-(Zr, ZrNb, and ZrSi), as promising candidates for enhancing the durability and efficiency of Ti6Al4V materials used in nuclear fusion technology. X-ray diffraction analysis identified distinct phases, including TiN, ZrN, ZrC, and TiC. The corrosion studies showed complete degradation of the TiN, ZrC, and ZrN phases in the TiZrCN coating after tests, while the TiC phase exhibited relative stability. The surface morphologies and elemental mapping analysis demonstrated the loss of homogeneity in element distribution after corrosion process. The addition of Si and Nb elements into TiZrCN significantly influenced the coatings' corrosion behavior, with breakaway corrosion observed in CNTi- (Zr and ZrSi) coatings and localized corrosion in CNTi-(ZrNb) coatings. Notably, the CNTi-(ZrSi) coating formed an oxide phase in the presence of NaCl, whereas the CNTi-(ZrNb) coating exhibited continuous resistance and a low corrosion rate. Irradiation was carried out for the generation of active isotopes, showing that no radioactive isotopes were formed in any of the investigated samples

Negative magneto-resistance of electron gas in a quantum well with parabolic potential

We have studied the electrical conductivity of the electron gas in parallel electric and magnetic fields directed along the plane of a parabolic quantum well (across the profile of the potential). We found a general expression for the electrical conductivity applicable for any magnitudes of the magnetic field and the degree of degeneration of the electron gas. A new mechanism of generation of the negative magnetoresistance has been revealed. It has been shown that in a parabolic quantum well with a non-degenerated electron gas the negative magnetoresistance results from spin splitting of the levels of the size quantization.Comment: 15 pages, 3 figure

Advantages of the Blue InGaN/GaN Light-Emitting Diodes with an AlGaN/GaN/AlGaN Quantum Well Structured Electron Blocking Layer

Cataloged from PDF version of article.InGaN/GaN light-emitting diodes (LEDs) with p-(AlGaN/GaN/AlGaN) quantum well structured electron blocking layer (QWEBL) are designed and grown by a metal− organic chemical-vapor deposition (MOCVD) system. The proposed QWEBL LED structure, in which a p-GaN QW layer is inserted in the p-AlGaN electron blocking layer, not only leads to an improved hole injection but also reduces the electron leakage, thus enhancing the radiative recombination rates across the active region. Consequently, the light output power was enhanced by 10% for the QWEBL LED at a current density of 35 A/cm2. The efficiency droop of the optimized device was reduced to 16%. This is much smaller than that of the conventional p-AlGaN electron blocking layer LED, which is 31%

Improved hole distribution in InGaN/GaN light-emitting diodes with graded thickness quantum barriers

Cataloged from PDF version of article.InGaN/GaN light-emitting diodes (LEDs) with graded-thickness quantum barriers (GTQB) are designed and grown by metal-organic chemical-vapor deposition. The proposed GTQB structure, in which the barrier thickness decreases from the n-GaN to p-GaN side, was found to lead to an improved uniformity in the hole distribution and thus, radiative recombination rates across the active region. Consequently, the efficiency droop was reduced to 28.4% at a current density of 70 A/cm2, which is much smaller than that of the conventional equal-thickness quantum barriers (ETQB) LED, which is 48.3%. Moreover, the light output power was enhanced from 770 mW for the ETQB LEDs to 870 mW for the GTQB LEDs at 70 A/cm2. © 2013 AIP Publishing LLC

Retrospective Determination of Prognostic Factors in BRAF-V600E Melanoma Brain Metastases​

View full abstracthttps://openworks.mdanderson.org/leading-edge/1030/thumbnail.jp