Rod System Research Articles

Total sacrectomy with a combined antero-posterior surgical approach for malignant sacral tumours

PurposeTo investigate the indications, approaches, resection methods, and complications of total sacrectomy with a combined antero-posterior approach for malignant sacral tumours.MethodsFourteen cases of primary malignant sacral tumours treated with total sacrectomy between January 2012 and 2018 were retrospectively analysed. All patients presented with pre-operative lumbosacral pain or constipation. A combined antero-posterior approach was used for tumour resection, and the spinal pedicle screw rod system was used to achieve ilio-lumbar stability. The visual analogue scale (VAS) and Musculoskeletal Tumor Society (MSTS) scores were used to assess pain and lower limb function, respectively. The mean operative time and intra-operative blood loss were 6.54 hours and 2935 mL, respectively. The mean follow-up period was 62 months.ResultsNone of the patients died peri-operatively. At the last follow-up, ten patients were continuously disease-free, three were alive with disease, and one died of disease from lung metastasis. Tumour recurrence occurred in three patients. The MSTS scores ranged from 6 to 28 (20.00–93.33%, 6/30–28/30) with an average of 20 (66.67%, 20/30). Seven patients could walk independently in public, five could only walk at home using a walking aid, and two could only lie down and stand for a short time. Thirteen patients developed post-operative complications such as skin necrosis, screw loosening, connecting rod fracture, neuropathic pain, sciatic nerve injury, dysuria, and urinary incontinence.ConclusionTotal sacrectomy can effectively treat malignant sacral tumours with good resection boundaries and prognosis. However, the high incidence of post-operative complications may impact post-operative neurological function.

COMPREHENSIVE STUDY OF THE DYNAMICS OF THE RETAINING MECHANISM OF THE AUTOMATIC MILL

The results of the study of the dynamics of the mechanism for holding the mandrel of an automatic TPA mill are presented. The value of the axial force acting on the mandrel and the rod system of the mechanism of its holding is determined. Developed models of the mandrel retention mechanism have been developed, which made it possible to establish the nature of the development of dynamic processes on the output side of the automatic mill, taking into account the force parameters of the longitudinal rolling process of the sleeve and the parameters of the output side of the automatic mill. Mathematical models of the mandrel retention mechanism have been developed, taking into account the parameters of the technological process and the inertness of the rolled sleeve. The solution of the system of differential equations with variable coefficients is implemented numerically using the Runge-Kutta method for the corresponding dynamic models of the mandrel retention mechanism on the example of calculating the automatic mill TPA 350. The picture of the formation of dynamic processes in the mandrel retention mechanism during the implementation of the entire technological process of pipe production on an automatic mill has been clarified. taking into account the variable impact from the deformation zone and the change in the mass of the rolled sleeve. For various dynamic models, numerical solutions of problems were implemented, which made it possible to select the necessary technological and dynamic parameters of the mechanical system, to assign stable modes of rolling the sleeves on the automatic mill TPA 350. It is shown that the refined solution of the problem for three developed dynamic models of the mechanical system differs significantly from the previously known mathematical models. It has been established that the dynamics of the mechanism for holding the mandrel of the automatic TPA 350 mill is equivalent to the formation of the mechanism for the formation of different wall thickness of pipes. A mechanism for stabilizing the dynamics of the mandrel holding mechanism by separating the sections of the output side of the mill is proposed.

The Influence of the Negative Properties of Heaving Soil on the Stability of Frame-Rod Structural Systems

This article discusses the influence of the negative properties of heaving soil on the stability of frame-rod structural systems during the operation of buildings and structures. It is known that the loads and influences arising during the operation of buildings and structures can lead to loss of stability of both an individual element and the entire structural system as a whole. It is extremely difficult to accident-free work operation of buildings and structures, the foundation layer of which are heaving soils. Therefore, it is necessary to develop a methodology for determining the critical stability parameters of frame-rod structural systems that takes into account the heaving properties of base soils. In the process of loss of stability, elements of frame-rod structural systems under the influence of force factors due to the influence of constrained conditions can experience both passive and active bifurcation. With the manifestation of the negative properties of heaving soils, vertical deformations of the base occur, which can lead to a change in the type of bifurcation of both an individual element and the entire structural system as a whole. Based on the assumption that the element will pass from passive bifurcation to active at the moment when the work performed by internal forces is compensated by the work of the heaving forces, an expression is obtained to determine the critical deformation of the base soil. A statically indefinable single-span frame is considered, the right strut of which is loaded with force P and the left one with force αP. Using the displacement method, the critical stability parameters of the specified rod system were determined before and after the manifestation of the negative properties of the base soil. Based on the numerical analysis, it was concluded that the right pillar of the frame loses stability actively, involving the left one in the general bifurcation. After manifestation of the negative properties of the base soil, the type of bifurcation of the frame elements changes, leading to significant changes in the stability parameters. In this case, the critical deformation of the heaving linearly increases with an increase in the geometric dimensions of the frame and decreases with an increase in the load application coefficient α at 0,6<α<0,8 and 1,0<α<1,1. In the range 0,8>α> 1,0, these parameters are directly proportional.

Research Progress of Exoskeleton for Hand Rehabilitation following stroke

Based on the hand rehabilitation exoskeleton, the research results of three driving modes in recent years, namely cable, connecting rod and pneumatic system, were classified, summarized and analyzed. Through research and analysis, the results of structural dimensions, structural degrees of freedom, drive selection scheme, control strategy and sensor selection scheme which are more suitable for human hand rehabilitation exoskeleton are obtained, which can provide reference for exoskeleton researchers.

Research on the Fast Reset Time of Safety Rod and Implementation

The fast reset time of the safety rod is one of the important parameters for the drive design of space nuclear reactor. In the paper, it analyses the structure, operation process, and fast reset process of the safety rod system, and proposes a measuring method that measures the change of the angular displacement sensor in the drive mechanism during the fast reset process of the safety rod assembly to get the fast reset time of the safety rod. The ground engineering prototype of the safety rod was used to verify the measuring method, by real test environments, such as real high temperature, earthquake. The test results show that the measuring method of the fast reset time is effective on the safety rod, and provides a test basis for the research on the drive design of the safety rod system of the space nuclear reactor.

ОБЩИЙ ПОДХОД К РАСЧЕТ У СЛОЖНЫХ СТЕРЖНЕВЫХ И ПЛАСТИНЧАТЫХ СИСТЕМ НА ПРОИЗВОЛЬНОМ УПРУГОМ ОСНОВАНИИ

This paper generalizes the method of static calculation of complex rod and plate systems on an arbitrary elastic foundation under the action of an external load, when modeling the foundation with various models, ranging from the classical Winkler model to a combined model consisting of the Winkler model and the Kogan two-layer model. The relevance and timeliness of the proposed work lies in the fact that the issues of calculating complex structures on an elastic foundation have not yet been fully investigated and there is no general approach to their calculation. The author knows the works of M.I. Gorbunova-Posadova, I.A. Simvulidi, G. Ya. Popova, S.N. Klepikova, S.D. Semenyuk, in which various approaches were used to study the design of simple rod structures, isolated foundation slabs, including mesh slabs, as well as spatial monolithic foundations, as a system of cross belts on an elastic foundation. The proposed technique is based on the Ritz variational method and the mixed method of structural mechanics using Zhemochkin’s influence functions. To determine the coefficients of the canonical equations and free terms of the mixed method of structural mechanics through the Zhemochkin method, the calculation uses the ratios for the deflections of plates or beams with pinching in their center. To simplify the relations of the Zhemochkin method in hinged-connected beams, it is convenient to introduce pinching with unknown displacements at the beginning or end of each beam. The numerical implementation of the general approach was carried out using the Mathematica computer program.

Management of fractures of thoraco lumbar spine with pedicle screw fixation

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; Thoraco-lumbar fractures are serious injuries of concern, if left untreated may result in marked morbidity and disability to the patient. To study the efficacy of pedicular screw and rod fixation system (ZETA system) in achieving ‘stabilization’ in thoracic and lumbar fractures of the spine.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; This was a prospective comparative on-randomized study of 20 patients who underwent pedicle screws and rod fixation in Goverment District headquarters hospital Nagapattinam with a follow-up ranging from September 2018 to December 2018 duration of 4 months. Patient selection was according to the inclusion and exclusion criteria and was surgically treated with pedicle screw and rod system (ZETA).&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; In 75% of the patients, the fractures were reduced by using polyaxial implants and in 25% of the patients both monoaxial and polyaxial implants were used. The average regional angle during the pre-operative stage was 16.50±5.020 and 4.450±4.150 during the 1-year post-operative period. There was a significant difference between pre-op and post-operative regional angles.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; There is a very high statistical significant restoration of vertebral body height, mean regional angle, and mean anterior wedge angle with this procedure in thoracolumbar fractures. Neurological recovery was seen significantly when all cases with neurological deficits were clubbed together.&lt;/p&gt;

Determining the mechanical characteristics of composite materials reinforced with woven preforms

Reduction of the complexity of production of articles from composite materials is largely ensured by the use of reinforcing semi-finished products in which fibers pre-form a framework. Among all the variety of reinforcing systems, woven sleeves (preforms) occupy a special place. The high degree of deformability in a nonimpregnated condition makes it possible to lay this reinforcement on any surface without folds and cuts that provide preservation of strand continuity. This advantage of woven sleeves is accompanied by a change in local reinforcement angles and, consequently, the variable nature of physical and mechanical characteristics of the curved part surface. A method for calculating physical and mechanical characteristics of the composite based on preforms at any point of the part depending on the pattern of laying strands on a curved surface has been developed. The possibility of application of the rod model of the composite to describe physical and mechanical characteristics of the composite material with a woven reinforcement was analyzed. The model essence consists in that the composite is modeled by a diamond-shaped rod system. The rhombus sides serve as fibers and the diagonals as the binder. To verify the theoretical results and substantiate practical recommendations, a series of experimental studies were performed based on the formation of material specimens from two types of woven sleeves with different reinforcement angles. The experimental study program included tensile, bending, and compression tests. A fairly good convergence of theoretical and experimental data was obtained. For example, a square of the correlation coefficient was not less than 0.95 for the modulus of elasticity, not less than 0.8 for the Poisson's ratio, and not less than 0.9 for tensile and compressive strengths. This is the rationale for using the rod model to describe the considered class of composites. The use of the developed procedure will make it possible to increase the perfection of the considered class of designs and obtain rational parameters of the process of their manufacture.

A Hydraulic Analog Computer to Physically Represent the SIR Model Dynamics Focusing on COVID-19

A system of interconnected water tanks, with buoy, rods, gear racks, sprockets and valves, forming a hydraulic analog computer focused on the New Coronavirus (COVID-19) pandemic is presented. Its functioning represents the dynamics of any epidemic, and allows for a more direct and ``physical'' understanding of the phenomenon. No need to know differential equations, or elaborate mathematics, in order to grasp the dynamics of an epidemic. The New Coronavirus pandemic is used as an example.

Identification of potential regulatory domains within the MreC and MreD components of the cell elongation machinery.

The bacterial peptidoglycan (PG) cell wall maintains cell shape and prevents osmotic lysis. During growth of rod-shaped cells, PG is incorporated along the cell cylinder by the RodA-PBP2 synthase of the multi-protein Rod system (elongasome). Filaments of the actin-like MreB protein orient synthesis of the new PG material. They are connected to the RodA-PBP2 synthase in part through the RodZ component. MreC and MreD are other conserved components of the system, but their function is not well understood. Amino acid changes in RodA-PBP2 were recently identified that bypass a requirement for MreC and MreD function, suggesting the Mre proteins act as activators of the synthase. To further investigate their function, we developed a genetic strategy to identify dominant-negative alleles of mreC and mreD in Escherichia coli Residues essential for Rod system function were identified at the junction of two subdomains within MreC and in a predicted ligand-binding pocket of MreD. Additionally, we found that although the proline-rich C-terminal domain of MreC is non-essential, substitutions within this region disrupt its function. Based on these results, we propose that the C-terminus of MreC and the putative ligand-binding domain of MreD play regulatory roles in controlling Rod system activity.IMPORTANCE: Cell shape in bacteria is largely determined by the cell wall structure that surrounds them. The multi-protein machine called the Rod system (elongasome) has long been implicated in rod-shape determination in bacilli. However, the functions of many of its conserved components remain unclear. Here, we describe a new genetic system to dissect the function of these proteins and how we used it to identify potential regulatory domains within them that may modulate the function of the shape-determining machinery.

Transient Voltage Programming in Electric Power Grounding System

Liner equations with n variables can be solved if there are n equations, the matrix is formed n x n square matrix, using the inverse matrix method. In this research, the linear equation used comes from the rod and mesh grounding system method, which is solved by the finite element method to calculate the grounding impedance, from the results of other research researchers. Here the researcher wants to inform in this study how to solve the linear equation with a calculation program. And the research results are plotted in Cartesian coordinates V = V (t). The results of this calculation program can be used to estimate how much the transient voltage is in the ground rod / mesh in the place where the electrical power system substation will be built when lightning strike with an amplitude of 34 kA/switching with a current of 34 kA/step with a current of 34 kA crash it. To adjust the transient voltage by adjusting the length of the finite element, required in accordance with the applicable safety level, while the subsequent arrangement can by increasing the number of mesh or increasing the length of the mesh.

Efficacy of distal pedicle screw fixation as a caudal foundation in VEPTR growing rod constructs for early onset scoliosis.

Surgical treatment of Early Onset Scoliosis (EOS) is challenging. Stable and robust foundations are vital. We have assessed a small cohort of patients with a rib-based proximal fixation and a pedicle screw-based distal foundation for a distraction based growing rod system. This is a single center study in a tertiary spinal deformity unit with a catchment population of over 6 million. We performed a retrospective radiographic evaluation of 15 patients with EOS treated with Vertical Expandable Titanium Prosthetic Rib (VEPTR) implant between 2007 and 2017. The review of medical records and imaging data was performed to identify growth of the spine and complications with pedicle screws. There were ten male and five female patients with an average age at index surgery of 4yrs 11months. Mean length of follow-up was 6yrs 9months. Serial radiographs revealed improvements in mean Cobb angle of 12 degrees, T1-T12 height of 29mm and T1-S1 height of 48mm with no deterioration in distal LIV tilt angle. We report that none of these patients had any complications related to their pedicle screws including cut-out. We report a technique which is efficacious and provides a mechanically robust distal fixation for VEPTR lengthening in early onset scoliosis.

Visual Abnormalities Associate With Hippocampus in Mild Cognitive Impairment and Early Alzheimer's Disease.

Background and Objective: Alzheimer's disease (AD) has been shown to affect vision in human patients and animal models. This study was conducted to explore ocular abnormalities in the primary visual pathway and their relationship with hippocampal atrophy in patients with AD and mild cognitive impairment (MCI). The aim of this study was to investigate the potential value of ocular examinations as a biomarker during the AD progression.Methods: Patients with MCI (n = 23) or AD (n = 17) and age-matched cognitively normal controls (NC; n = 19) were enrolled. Pattern visual-evoked potentials (PVEP), flash electroretinogram (FERG) recordings and optical coherence tomography (OCT) were performed for all participants. Hippocampal volumes were measured by 3T magnetic resonance imaging. Cognitive function was assessed by Mini Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA) and Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog). Pearson correlation was employed to analyze the potential associations between ocular abnormalities and hippocampal volumes. Hierarchical regression models were conducted to determine associations between cognitive performances and ocular abnormalities as well as hippocampal volumes after adjusting for confounding factors including age, sex, cognitive reserve, and APOE4 status.Results: PVEP amplitude of P100 waveform was significantly decreased in AD patients compared to MCI and normal individuals. In FERG test, delayed latencies of rod response, rod cone response and 3.0 flicker time were found in cognitively impaired groups, indicating dysfunctions of both the rod and cone systems in the disease progression. OCT test revealed reduced macular retinal nerve fiber layer (m-RNFL) thickness in MCI and AD patients, which significantly correlated with brain structure of hippocampus particularly vulnerable during the progression of AD. Interestingly, P100 amplitude showed a significant association with hippocampal volumes even after adjusting confounding factors including age, sex, and cognitive reserve. Hierarchical regression analysis further demonstrated that m-RNFL thickness, as well as hippocampal volumes, significantly associated with ADAS-cog scores.Conclusion: P100 amplitude and m-RNFL thickness showed significant correlations with brain structure involved in AD-related neurodegeneration, and therefore proved to be potential indicators of brain imaging pathologies.

Study of functional outcome in low grade spondylolisthesis operated by pedicular screw instrumentation and fusion

Background: Functional outcome following instrumental spinal surgery for spondylolisthesis inphysically energetic patients is crucial. The present study was undertaken to evaluate the functionaloutcome of low-grade spondylolisthesis accompanied by low back pain with or without radiculopathy,with standard surgical procedure posterior lumbar interbody fusion with instrumentation. Method:In this study total of 40 patients were operated on for low-grade spondylolisthesis by posteriorstabilization using a pedicular screw rod system and posterior lumbar interbody fusion. All thepatients were followed up till 6 months after surgery and functional outcomes were noted. Results:Assessment of this series it was observed that, 57.5% of the patient had excellent outcome, 37.5%had a good outcome and 97.5% of the study population had satisfactory outcome (improvement inclinical results). There was a significant improvement in pain intensity, walking, lifting, standing,sleeping after surgery. The mean ODI difference between preoperative and post-operative at 6months follow up was 36.12% (16.75). In the outcome, 62.5% of the patient consisted of severedisability and 32.5% were with moderate disability (total-95%) while postoperative 87.5% were witha minimal disability and only 2.5% of the study population had worsened i.e crippled. Conclusion:The study concluded that surgery in form of decompression with instrumentation and posteriorlumbar interbody is a safe and effective method to treat spondylolisthesis.

On a heat propagation problem in a system of rods on a tree graph

On a heat propagation problem in a system of rods on a tree graph

Some issues of calculation of complex rod and plate systems on an elastic base

This paper summarizes some issues of a new universal method for static calculation of complex rod and plate systems on an arbitrary elastic base under the influence of an external load, when modeling the base with various models, ranging from the classical Winkler model to the combined Winkler-Kogan model. The relevance and timeliness of the proposed work lies in the fact that the issues of calculating complex structures on an elastic base have not yet been fully investigated and there is no general approach to their calculation. The author knows the works of M. I. Gorbunov-Posadov, I. A. Simvulidi, B. N. Zhemochkin, G. Ya. Popov, S. N. Klepikov, S. D. Semenyuk, S. V. Bosakov, in which various approaches have been used to conduct research on the calculation of simple core structures, isolated foundation structures, including mesh slabs, as well as spatial monolithic foundations, as a system of cross belts on an elastic base. The proposed method is based on a mixed method of structural mechanics using the functions of the influence of an elastic medium in the relations of B. N. Zhemochkin. To simplify these relations, when determining the coefficients of canonical equations and free terms of the mixed method in the calculation of isolated and connected plates, the relations for deflections of plates with a normal pinched in the centre of the plate are used. For pivotally connected beams, it is convenient to introduce pinching with unknown displacements at the beginning or end of each beam, for frame rods-in their nodal connections. The numerical implementation of the general approach is performed using the Mathematica computer program.

Plastic stiffness matrix of a plane rod macroelement for discrete-analytical strength computation

The paper considers a discrete-analytical solution of the plane strength problem, with the rod system being under elastic-plastic loading, and the rod performance is considered fundamentally important for the study. Simplifications are proposed in determining the plastic stiffness matrix of the rod element using the integral function of the law of the section state. A mathematical model has been developed to determine the tangential stiffness of a cross-section of the rod of a variable form at a time step, during elastic-plastic camputation. The results of a physically nonlinear calculation of the planar system with the articulation of a large number of rod macro-elements are presented.

Finite Element Analysis of an Improved Correction System for Spinal Deformity.

Surgical treatment for spinal deformity aims to correct malformation, release the nerves, and reconstruct spinal stability. To explore and develop a new improved spinal correction system (ISCS) for clinical application, we studied the stability and biomechanical characteristics of the ISCS through finite element analysis and comparison of the ISCS with the pedicle screw and rod system (PSRS). Using L1-L3 CT image data of a normal adult male lumbar spine for establishment of L1-L3 finite element model, we established posterior internal fixation models for a comparative finite element analysis of PSRS and ISCS. An axial load of 500 N and a moment of 10 N•m were applied to L1 to simulate flexion, extension, lateral bending, and axial rotation. Stress distribution characteristics, load sharing, strain bending stiffness and strain angle change of the models were measured. In flection and extension directions, the maximum stress of the L2 vertebral body and the L1/2 and L2/3 discs in PSRS was less than that of ISCS. In lateral bending and axial rotation directions, the maximum stress between PSRS and ISCS was similar. However, the stress shielding rate of L2, L1/2, and L2/3 intervertebral discs in ISCS was significantly lower than that of PSRS. We also found that both models had similar angular displacement and maximum displacement in lateral bending direction, but PSRS had a lower angular displacement and maximum displacement in flection and extension directions. Finally, we showed that PSRS had similar angular displacement and a lower maximum displacement compared with ISCS in axial rotation, whereas ISCS had lower bending stiffness than PSRS in different directions. ISCS can effectively fix spinal deformities compared to PSRS. ISCS provides a new option for orthopedic surgery treatment of scoliosis and, therefore, warrants further clinical studies in patients with other spinal deformities.

Numerical investigation of snowstorm filling

During industrial air preparation, one of the most important issues is the proper moisture content. In vehicle brake systems, compressed air is commonly used, where condensate in the system can lead to serious problems as corrosion, frosting, etc. For avoiding malfunctions, the relative humidity of the media must decrease to 20-40%, by adsorbing its moisture content. To achieve this, air dryer units filled with desiccant granular media is commonly used in railway industry. The compressed air flows through the dryer, thus the particles can bind the water vapour. If the packing density of the desiccant can increase, the efficiency of the dryer can improve. In this paper an interesting method for container filling, the snowstorm technique was investigated and optimized by applying discrete element method. Essence of the device is a rod system placed below the filler bin, which ensures even distribution of the particles. By the numerical analysis it was revealed, the particles’ lateral velocity is increased because of the snowstorm system, but with non-optimal arrangement, the particle flow can be significantly blocked. Based on our systematic analysis, optimal geometry of the particle distribution system was found, which ensures settling more particles by 9.5% into the dryer reservoir.

Development and characterization of a mechanical compression device for quantifying the elasticity of the porcine and human crystalline lens

PurposeWe present the development and characterization of an electromechanical device that quantifies the elasticity of the crystalline lens ex vivo by measuring its reaction force when it is compressed by a rod moved step by step. Our specifications required a robust system, fast to allow serial analysis, capable of measurements on an immersed lens, and highly resolved to detect small changes in elasticity.MethodsA first simple manual device was constructed to dimension the measuring system. The lenses (human and porcine) immersed in a buffer solution were placed on a precision weighing balance and compressed from top to bottom by a rod mounted on a micrometer screw. This system made it possible to define, among other things, the resolution of the balance (1 mg, 0.01 milli‐Newton). In a second device, the rod system was motorized with a resolution of 0.625 µm pitch in order to automate the measurement, and the balance data were integrated in real time into software executable on a desktop computer. A control camera (30 µm/pixel) was added to facilitate the approach of the rod in contact with the lens and to document the deformation experienced.ResultsThe built‐in calibration of the balance allows direct measurement in Newton. The device allowed determining the very homogeneous behavior of the lens (elastic reaction versus displacement) as well as the breaking point of the capsule which is much higher than the elastic deformation (at about 100 times the weight of the lens). Automation also allows the measurement of lens relaxation times during pulsed stimulation, for example by compression/decompression of 1 mm on a porcine lens.ConclusionsWith a measured effective fidelity of 5 µm and 0.01 mN, this direct compression system allows the mechanical elastrometry of the lens. The measurement of a large series of human and porcine lenses of different ages is in progress to determine its accuracy and repeatability. It will be useful for any research on lens biomechanics.