Journal of Computational Methods in Sciences and Engineering

This study presents, use of a technique based on functional imaging and Computational Fluid Dynamics (CFD) modeling in generating useful data that can be used to determine and diagnose Obstructive Sleep Apnea (OSA) condition. A three-dimensional nasal cavity model was reconstructed based on computed tomographic images of a healthy Malaysian adult nose. Navier-Stokes and continuity equations for steady airflow were solved numerically to examine inspiratory and expiratory nasal flow.The study showed that, the pressure drop from the choanae to the OSA region was found to be larger than the pressure drop through the nasal passages. Stresses as high as 42.4 Pa were observed in this constricted OSA passageway, which is otherwise not a common occurrence in the normal subjects.

Over the past three decades the occurrence of high environmental concentrations of arsenic has been recognized as a major public health concern. Arsenic is a carcinogen and causative agent for number of diseases. The toxic and carcinogenic effects of arsenic are the result of inactivation of specific enzymes of metabolism, induction of oxidative stress, inhibition of DNA repair mechanisms and deregulation of cell proliferation. Despite its toxicity, arsenic has a long history of usage as chemotherapeutic agent. Today, drugs containing arsenic (and the related metalloid antimony) are used for treating acute promyelocytic leukemia and diseases caused by protozoan parasites. In response to its toxicity, many microorganisms have developed arsenic resistance mechanism. In bacteria, arsenic resistance genes are organized in ars operons. The best characterized, the ars operon from Escherichia coli plasmid R773, has five genes, arsRDABC. ArsC is a reductase that reduces inorganic As(V) to As(III). ArsR is a 117-residue homodimeric As(III)-responsive transcriptional repressor with high affinity for the ars promoter. ArsA is an ATPase, which is the catalytic subunit of the ArsAB efflux pump, and ArsD is an As(III) chaperone to the ArsAB pump. ArsD is a homodimer of two 120-residue subunits with three vicinal cysteine pairs, Cys12-Cys13, Cys112-Cys113 and Cys119-Cys120. A fully-active truncated version of ArsD protein with 109 residues (ArsD109) has been crystallized, and the structure has been solved using X-ray crystallography. Biochemical studies suggested that wild-type ArsD binds three As(III) per monomer, while the derivative with a truncation at residue 109 binds only a single As(III). To understand the secondary structure and folding of the C-terminus of ArsD, which includes two cysteine pairs Cys112-Cys113 and Cys119-Cys120, Molecular Dynamics (MD) simulations were employed using AMBER software in presence or absence of arsenite [As(III)] ligand.

Arsenic is a hazardous substance and exposure to inorganic arsenic leads to various vascular and carcinogenic diseases. Reduction of pentavalent arsenical to trivalency plays a critical role in its detoxification. We have earlier shown that human Cdc25B or Cdc25C protein tyrosine phosphatase catalyzes the reduction of inorganic arsenate to arsenite. Human glutaredoxin-1 functions as a hydrogen donor for Cdc25 catalyzed arsenate reduction. In this paper, molecular docking studies were performed to understand the interactions between Cdc25 and the two dicysteinic glutaredoxins, glutaredoxin-1 and glutaredoxin-2, and the monothiol glutaredoxin-3.

The problems that often arises in orthodontic treatment of adult patients is the presence of periodontal disease and loss of bone support. As a consequence of this, the center of resistance of the tooth is altered. Excessive orthodontic force with advanced periodontal bone loss may traumatize the periodontium. Force dosage during orthodontic treatment is one of the most difficult problems at this stag.the purpose of the study is to simulate the effect of orthodontically induced stress in the periodontal ligament of maxillary molar at different levels of bone loss. The study is carried out to estimate the reduction in magnitude of force at different levels of bone loss (2.5 mm, 5 mm and 6.5 mm) necessary to achieve evenly distribution of stress in the periodontal ligament of the tooth as obtained without bone loss and to determine the change in counterbalancing M/F ratio to induce uniform stress distribution in the PDL. A 3-dimensional finite element model of a tooth comprises of maxillary first molar with periodontal ligament and alveolar bone with different levels of bone height was constructed. Bone loss that ranged from 2.5 thrugh 6.5 mm was simulated in a model. Necessary reduction in the magnitude of force and the increase in moment to force (M/F) ratio was determined to obtain evenly distributed stress in the periodontal ligament of a tooth. The results showed that lesser force magnitude is required in simulated 2.5 mm bone loss (80%), 5 mm bone loss (60%), 6.5 mm bone loss (35%) as compared to the initial load applied to the tooth without bone loss. The counter tipping moment to force ratio should be increased from no bone loss (9.65) through 6.5 mm bone loss(12.8) to maintain the same range of stress in the PDL as was obtained without bone loss. The counter rotation moment to force ratio should decrease from no bone loss (5.65) through 6.5 mm bone loss (4.0) to maintain the same range of stress in the PDL as was obtained without bone loss. Combination of decreased force magnitude and increased counter tipping moment to force ratio will bring about uniform stress in the periodontal ligament of a tooth with varying degree of bone loss.

Due to increasing popularity of lingual orthodontics in recent years, various lingual systems have been developed. In orthodontics Finite Element Method (FEM) has been used to study various types of tooth movement. Although FEM was extensively used for evaluating the biomechanical effects of labial orthodontic forces, research on lingual system is still limited. The purpose of this study is to evaluate the efficacy of two different lingual bracket systems using FEM. FEM of maxilla which included six upper anterior teeth, periodontal ligament has been created. Six upper anterior teeth were digitally arranged in final position using a new computerized method. CAD models of six upper anterior brackets of 7^th generation and Lingual matrix have also been created and attached onto the digital model at appropriate heights. Various orthodontic movements were simulated and force applied distal to the canine bracket. Deformation, stress on teeth, bone and periodontal ligament were studied and compared between the two different lingual systems. Deformation was less with lingual matrix brackets than 7^th generation brackets when subjected to intrusive, retractive and combined forces. More stresses were generated on the teeth, bone and PDL in lingual matrix brackets than 7^th generation brackets when subjected to forces. It was found that tooth movements are more efficient and precise in lingual matrix brackets than prefabricated 7^th generation brackets.

The main aim of this work was evaluation of the displacements, strains and stresses in components of knee endoprosthesis by means of Finite Element Method. The semi-constrained knee endoprosthesis instrumented into femur and tibia bones was chosen for the analysis. The first step was preparation of full knee endoprosthesis geometrical model which was developed on a basis of a real model. Using reverse engineering methods containing 3D scanning and post-processing, model was obtained and then modified due to analysis assumptions. To carry out an analysis it was necessary to develop a femur and tibia bone models, which were obtained from MRI scans. Next a grid for finite-element method calculations was generated for the geometrical model. Mesh was next optimized to obtain high quality elements along with simplification of calculations. Subsequently it was necessary to specify and set the edge conditions to reflect appropriately the phenomena taking place in the real system. The system was loaded with axial force from femur proximal joint surface to tibia distal joint surface in range of 500-2000 N. Calculations were realized for endoprosthesis components made of chromium alloy for femoral joint surface part, UHMWPE for plastic sliding bearing and five different titanium alloys for endoprosthesis femoral part stem and tibial implant part - Table 1. On a basis of obtained results, the highest values of reduced stress in endoprosthesis elements were observed in the stems of both femoral and tibial part. Stress in bone didn't exceed its compression strength for all of chosen materials. The biomechanical analysis may form the basis for improving the geometry of analyzed endoprostheses and optimizing a selection of the mechanical properties of the material used to manufacture them.

The post-genomic era produces an overwhelming amount of experimental data, but majority of such data lacks the characterization of its functions. Structure based approaches are useful to understand and characterize the functional aspects of proteins. Given the burgeoning requirement of understanding the functional aspects of various enzymes, we report a systematic structure based study of methyltransferases bound with S-adenosyl-L-methionine (SAM). Through this work, we identified the conserved amino acids of methyltransferase, which are interacting with SAM.

The aim of this paper was to evaluate the effect of grid size on the fatigue life calculations of a dental implant by conducting a non-linear contact FEM analysis. A Nobel - Biocare (Replace - Select) implant was chosen and modelled in CATIA after retrieving accurate dimensions from SEM. The mandibular bone was modelled using MIMICS software. Static and dynamic simulation was then conducted on the final assembly using ANSYS which is a commercially available FEA software package. It was observed that variation in grid size leads to significant variation in the life of the dental implant. Hence for an accurate estimation of fatigue life of the dental implant the mean of the range of values must be considered.

The purpose of the study was to use the finite element method to investigate the stress related changes in periodontal ligament of the posterior segment under orthodontic force application. The three dimensional finite element models of the maxillary first molar, maxillary first premolar, bracket,arch wire and molar tube are constructed. The models of the tooth were made from CT scans of the natural tooth. Dimensions of the tooth were taken from the Wheeler's text book. Mechanical parameters of PDL, root, alveolar bone and stainless steel wire were included. Two different directions of forces, mesial and distal were used in five different amounts, 250 g, 300 g, 350 g, 400 g, 450 g. Uneven distributions of the compressive and tensile stresses were seen in the PDL. This was due to the tendency of the teeth to rotate and tip instead of undergoing bodily movement.

This study was conducted using 3-dimensional Finite Element Analysis to evaluate the stress related changes in the periodontal ligament. The objectives of the study were to determine the optimum orthodontic force for both sliding and loop mechanics and to determine efficacy of two loop designs namely T - loop and Tear Drop loop. The efficacy of Permachrome and Beta III titanium archwire in loop mechanics were also evaluated.

Four modular Total Knee Arthroplasty(TKA) prosthesis designs (Cruciate Retaining, Anterior Slide, Tibial Post and Double Cam) based on Indian anthropometric data is considered for linear static Finite Element Analysis (FEA) in the study. von Mises stresses are studied for all the components of four different designs at 0°, 15°, 30°, 60° and 90° flexion angles. Stress distribution in the Polyethylene (PE) insert is of critical importance in deciding the longevity of the prosthesis. Peak von Mises stresses in PE insert are found to be 11.02 MPa, 32.13 MPa, 59.25 MPa and 23.78 MPa for Cruciate Retaining, Anterior Slide, Tibial Post and Double Cam design respectively. Results indicate yielding of PE insert in three designs(Anterior Slide, Tibial Post and Double Cam) and the reasons being less congruity and edge loading.

Diffusion of mobile technology presents numerous opportunities to bend healthcare cost curve. Chronic wounds are a global, ongoing health challenge that afflicts a large number of people. Effective diagnosis and treatment of the wounds relies largely on a precise identification and measurement of the wounded tissue; however, in current clinical process, wound evaluation is based on subjective visual inspection and manual measurements which are often inaccurate. Given the cost and inconvenience of regular visits to wound clinics and for providing real time aid/care to remote and rural areas smart phone app named, Wound Vision which tracks/identifies the wound size, healing/management process based on images captured/processed within a smart phone is designed. Therefore this automated mobile-based system for fast and accurate segmentation and identification of wounds is desirable, both from the standpoint of improving health outcomes in chronic wound care, and in making clinical practice efficient and cost-effective for people in remote areas and cities. Satisfactory results of this real time mobile system suggest a promising tool to assist in the field of clinical wound evaluation. The simplicity of the algorithm/framework used suggests that it is a valuable tool in clinical wound evaluation. Future work will incorporate additional features (wound Tissue analysis-necrotic, fibrin & granulation tissue) for assessing the wound healing process in order to completely replace clinical praxis. A working model of the application has been made and further optimizations are in progress.