Finite element simulation of hip joint replacement under static and dynamic loading

The objective of this work is to develop methods for the structural analysis of orthopaedic implants. The central argument is that, if stress distributions are interpreted in the context of failure models of the component materials, significant advantages can be made in our ability to design these devices. The artificial hip joint is used throughout as an example. The finite element method was used as a structural analysis tool and its pplicability was discussed. Validity and accuracy were assessed and results were ompared with previous experimental and finite element studies. By comparing tress distributions with failure criteria for prosthesis and cement, the suitability of roposed design changes were assessed and guidelines for materials selection were resented. Prediction of bone stresses were also given for different prosthesis designs n the region of the artificial hip joint where bone adaption contributes to failure. hereafter the focus was on utilizing a new technique to develop a new hip prosthesis model. This study was divided into two parts according to the loading type. In this regard the stress field in the artificial hip components (prostheses, cement mantle, and bone) is analysed statically and dynamically to assess the implant longevity. In this static analysis all the simulations were conducted by assuming the peak loads during the normal gait at a particular time (static loads). The aim was to study the effects of a set of variables within which an optimal prosthesis design can be made by means of finite element analysis to qualify and quantify the stresses and the strains in natural and treated human femur for different cases of implantation. Until now, models developed to predict stresses in total hip replacements have been generally poorly validated. This could be because all the pre-clinical simulations were performed statically, that is by selecting the greatest load at a particular time of the activity cycle. The second part of the study was aimed to take into consideration, in designing total hip replacement, another factor belongs to the patient activity (stamping, jumping, walking, etc) and the effect of impact over the prosthesis head during these activity into the prosthesis performance. This study considered the prosthesis hip deformation with time, dynamic loads study. The elimination of impact cracking was considered by studying the effect of using “damper” trapped between the grooved prosthesis collar and the bone. Material selection of the total hip replacements was also investigated under the dynamic loading. The approaches of prosthesis fixation have been studied, too. This study was conducted by onstructing three-dimensional finite element model for a femur implanted with a cemented prosthesis with a representative physiological loading condition by using he LS-DYNA3D software

Microstructure-failure mode correlations in braided composites

Explication of the fracture processes of braided composites is needed for modeling their behavior. Described is a systematic exploration of the relationship between microstructure, loading mode, and micro-failure mechanisms in carbon/epoxy braided composites. The study involved compression and fracture toughness tests and optical and scanning electron fractography, including dynamic in-situ testing. Principal failure mechanisms of low sliding, buckling, and unstable crack growth are correlated to microstructural parameters and loading modes; these are used for defining those microstructural conditions which are strength limiting

Yarn carrier apparatus for braiding machines and the like

A yarn carrier apparatus particularly suited for use in braiding machinery or the like due to its capability of continuous yarn feeding and retraction of long lengths of yarn. The yarn carrier apparatus comprises a yarn supply spool which is rotatably mounted within the housing, a spring motor also mounted within the housing and operatively connected to the yarn supply spool through a mechanical transmission assembly which is adapted to multiply rotational movement between the first element of the gear assembly operatively connected to the spring motor and the final element of the gear assembly operatively connected to the yarn supply spool. The spring motor is adapted to tension the yarn during both feeding and retraction thereof, and it is further adapted to periodically rotatably slip within the housing and partially unwind so as to allow for continuous withdrawal of a long length of yarn without the spring motor becoming fully wound and preventing further yarn retraction

Yarn carrier with clutch

A yarn carrier apparatus particularly suited for use in braiding machinery or the like due to its capability of continuous yarn feeding and retraction of long lengths of yarn. The yarn carrier apparatus comprises a yarn supply spool which is rotatably mounted within the housing, a spring motor also mounted within the housing and operatively connected to the yarn supply spool through a mechanical transmission assembly which is adapted to multiply rotational movement between the first element of the gear assembly operatively connected to the spring motor and the final element of the gear assembly operatively connected to the yarn supply spool. The spring motor is adapted to tension the yarn during both feeding and retraction thereof, and it is further adapted to periodically rotatably slip within the housing and partially unwind so as to allow for continuous withdrawal of a long length of yarn without the spring motor becoming fully wound and preventing further yarn retraction

Quantitation of Phenolic Acids and Effect of Controlled Atmosphere Storage on Peach Fruit Quality.

Total and individual phenolic acids in firm-ripe fruit of ten different peach (Prunus persica Batsch.) genotypes were analyzed by spectrophotometry and high performance liquid schrmoatography (HPLC) and related to internal browning potential. A comparison of phenolic acid separation was made between five different column types. A Lichrosorb RP-18 column provided the best separation of the major phenolic acids in peach fruit mesocarp tissue. Quinic was the predominant phenolic acid, followed in concentration by gentisic, catechin, chlorogenic, and syringic acids. Quantities differed between genotypes. The genotypes with the highest internal browning potential contained the highest concentration of chlorogenic acid, gentisic acid, and total phenolics. Controlled atmosphere ((1% O\sb2, 4% O\sb2, 7% O\sb2, or 20% O\sb2) + 5% CO\sb2) (CA) storage was tested to determine its effect on several physical and chemical attributes of firm-ripe harvested fruit. The 1% O\sb2 + 5% CO\sb2 and 4% O\sb2 + 5% CO\sb2 stored fruit had lower concentrations of reducing sugars but higher sucrose than fruit stored in air. Fruit pH increased and titratable acidity decreased over the 40 day storage period. The 1% O\sb2 + 5% CO\sb2 and 4% O\sb2 + 5% CO\sb2 stored fruits were higher in citric and malic acid content than air stored fruit. Citric acid and malic acid decreased during storage. Little or no change in individual phenolic acids occurred during storage or between 1% O\sb2 + 5% CO\sb2 and air storage. Internal color darkened and became redder with storage. CA stored fruit were significantly firmer than air stored fruit. Sensory evaluation indicated CA (1% O\sb2 + 5% CO\sb2) stored fruit were more acidic, sweeter, and had better overall flavor than air stored fruit. Peach fruits held at room temperature for 2 days following storage at 0\sp\circC in air for 40 days developed external and internal browning and fruit quality deteriorated. Comparable fruit stored at 0\sp\circC under 1% O\sb2 + 5% CO\sb2 had very little internal breakdown and retained good quality after 2 days at 22\sp\circC. The 20% O\sb2 + 5% CO\sb2 and air treatments had the highest percentage of fruit decay during storage at 0\sp\circC

New Exact Solutions for the Variable Coefficient Two-Dimensional Burger Equation

Abstract In this paper, the variable coefficient two-dimensional Burger equation is studied by two distinct methods. The Exp-function method with the aid of symbolic computation is used to derive soliton solutions of this equation. The ' G G -expansion method is used also to construct travelling wave solutions for the variable coefficient two-dimensional Burger equation with the aid of symbolic computation. The travelling wave solutions are expressed by the hyperbolic, the trigonometric functions and rational functions. The study highlights the significant features of the employed methods and its capability of handling exact solutions for the variable coefficient two-dimensional Burger equation without any restrictions on the form of the variable coefficient. The obtained solutions are considered new with the comparison of other solutions obtained before

Acute Perforated Peptic Ulcer at El Obeid Hospital, Western Sudan

Background: The pattern of peptic ulcer disease and its complications has changed during the last two to three decades.Objectives: To state the frequency of acute peptic ulcer perforations and outcomes of their management at El Obeid Hospital, Western Sudan.Materials and Methods: This is an audit of patients with acute perforated peptic ulcer admitted to the emergency wards of the University Surgical Unit at El Obeid Teaching Hospital, Western Sudan during the period from January 2006 to December 2012.Results: There were 53 patients, 94.3% were males. The age ranged between 18 and 77 years. Most of the patients reported late and 45.3% during Ramadan and Shawal. All patients had emergency peritoneal lavage and simple closure with omental patch followed by anti-ulcer therapy. The postoperative mortality was 7.6%.Conclusions: Perforated peptic ulcer in this community was mainly  duodenal. Emergency peritoneal lavage and simple closure with omental patch followed by anti-ulcer therapy resulted in excellent outcomes. Old age, shock, peritonitis and septicaemia were the major risk factors formortality.Key words: Perforated duodenal and gastric ulcers

Antibacterial activity of extracts of marine algae from the Red Sea of Jeddah, Saudi Arabia

In the present study, marine algae were collected from the southern coast of Jeddah, Saudi Arabia during summer and autumn 2009. The antibacterial activities of petroleum ether, diethyl ether, ethyl acetate and  methanol extracts of marine algae belonging to the Chlorophyta, Phaeophyta and Rhodophyta were studied. Their crude extracts were tested against different types of Gram-positive bacteria (Bacillus subtilis,  Methicillin-Resistant Staphylococcus aureus (MRSA) and Staphylococcus aureu) and Gram-negative bacteria  (Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa). All marine algae extracts tested  exhibited a broad spectrum of antibacterial activity. The maximum inhibition activities were shown for  extracts of Padina pavonica and Turbinaria triquetra. The growth inhibitions of bacteria by Sargassum  portieriatum extracts were higher in samples collected during autumn than that investigated in summer. The  maximum inhibitory effect of Gracilaria multipartita was observed in the petroleum ether extract against B.  subtilis and E. coli. The ethyl acetate and petroleum ether extract of Enteromorpha prolifera and Ulva reticulata  showed strong activity against the tested bacteria. The tested microorganisms that were susceptible to the most effective extracts were further tested for the minimum inhibitory concentration (MIC).  The MIC of the tested microorganisms was between 0.5 and 1.25 µg/ml. The results of the present study confirmed the potential use of marine algae as a good source of antibacterial agent.Key words: Chlorophyta, Phaeophyta, Rhodphyta, gram-positive bacteria, gram-negative bacteria,  solvent extract, minimum inhibitory concentration (MIC)

A polynomial regression model for stabilized turbulent confined jet diffusion flames using bluff body burners

AbstractThermal structure of stabilized confined jet diffusion flames in the presence of different geometries of bluff body burners has been mathematically modeled. Two stabilizer disc burners tapered at 30° and 60° and another frusted cone of 60°/30° inclination angle were employed all having the same diameter of 80(mm) acting as flame holders. The measured radial mean temperature profiles of the developing stabilizing flames at different normalized axial distances were considered as the model example of the physical process.A polynomial mathematical model of fourth degree has been investigated to study this phenomenon to find the best correlation representing the experimental data. Least Squares regression analysis has been employed to estimate the coefficients of the polynomial and investigate its adequacy. High values for R2>0.9 obtained for most of the investigated bluff burners at the various locations of x/dj prove the adequacy of the suggested polynomial for representing the experimental results. Very small values of significance F<(α=0.05) for all investigated cases indicate that there is a real relationship between the independent variable r and the dependant variable T. The low values of p<(α=0.05) obtained reveal that all the recorded parameters for all the investigated cases are significant