Despite recent advances in implants and surgical techniques, catastrophic and clinical failures in the treatment of intertrochanteric fractures continue to occur, with dire consequences in an overall ...frail population subset. The aim of the current study is to evaluate the effect of the factors under the surgeons’ control, namely fracture reduction and implant selection, on the biomechanical behavior of fracture fixation constructs.
An experimental protocol was conducted with the use of instrumented sawbones, in order to validate the finite element models. The implants used were the Gamma3®and DHS systems. Subsequently, a series of scenaria were considered, including various reduction and implant angle combinations. Data were retrieved concerning the peak cancellous bone stresses around the hip screw and the volume of cancellous bone in the femoral head stressed at critical levels, as well as implant stresses and stresses on the cortical bone of the distal fragment.
All stable fracture models displayed significantly decreased cancellous bone stresses and implant stresses compared to their unstable counterparts, regardless of implant used. The effect of increasing implant angle led to a decrease in implant stresses in all models studied, but had a beneficial effect on the stresses in the cancellous bone of the proximal fragment only in the subgroups of stable fractures with both implants and unstable fractures treated with a cephalomedullary nail (CMN). In unstable fractures anatomically reduced, the use of CMN led to significantly lower peak stresses in the cancellous bone and a smaller volume of bone stressed at critical levels. Increasing the reduction angle by 5 ° led to a significant decrease in both peak stresses and volume of bone stressed at critical levels, more prominent in the sliding hip screw (SHS) models. Decreasing the reduction angle into varus by 5 or 10 ° led to a significant increase in bone and implant stresses regardless of implant used.
In stable two-part (AO31.A2) fractures the use of the SHS appears to be biomechanically equivalent to CMN. In unstable, anatomically reduced fractures, the use of CMN leads to significantly reduced cancellous bone stresses and decreased rotation of the proximal fragment during loading.
A reduction in varus should be avoided at all costs. In unstable fractures treated with SHS a reduction in slight valgus appears to be biomechanically beneficial. The highest implant angle that allows for proper screw position and trajectory in the femoral head should be used for stable fractures with both implants and unstable fractures treated with Gamma3®.
In recent years, the acceptance of fatty acid methyl esters (biodiesel) as a substitute to petroleum diesel has rapidly grown in Greece. The raw materials for biodiesel production in this country ...mainly include traditional seed oils (cotton seed oil, sunflower oil, soybean oil and rapeseed oil) and used frying oils. In the search for new low-cost alternative feedstocks for biodiesel production, this study emphasizes the evaluation of pumpkin seed oil. The experimental results showed that the oil content of pumpkin seeds was remarkably high (45%). The fatty acid profile of the oil showed that is composed primarily of linoleic, oleic, palmitic and stearic acids. The oil was chemically converted via an alkaline transesterification reaction with methanol to methyl esters, with a yield nearly 97.5
wt%. All of the measured properties of the produced biodiesel met the current quality requirements according to EN 14214. Although this study showed that pumpkin oil could be a promising feedstock for biodiesel production within the EU, it is rather difficult for this production to be achieved on a large scale.
The present study examines the absorption capacity of five different types of materials for oil spills clean up. The absorbents were a commercial cellulosic material from processed wood, a commercial ...synthetic organic fiber from polypropylene and three commercial types of local expanded perlite from the island of Milos. The absorption capacities of the above materials were evaluated in a wet as well as a dry environment with different types of petroleum products. The results showed that commercial types of perlite, in some cases, have absorption capacities comparable to natural and synthetic organic materials used for clean-up applications. The enhancement of the hydrophobic properties of perlite can result in better performance in a water bath. The nature of the spilled oil proved to play an important role in the selection of the proper absorbing material. Overall, the results suggested that partial substitution of commercial synthetic sorbents by mineral materials widely produced in Greece for oil spill clean-up operations is possible, given their friendliness to the environment and their local abundancy.
Vegetable oils are produced from numerous oil seed crops. While all vegetable oils have high-energy content, most require some processing to assure safe use in internal combustion engines. Some of ...these oils already have been evaluated as substitutes for diesel fuels. With the exception of rape seed oil which is the principal raw material for biodiesel fatty acid methyl esters, sunflower oil, corn oil and olive oil, which are abundant in Southern Europe, along with some wastes, such as used frying oils, appear to be attractive candidates for biodiesel production. In this paper, fuel consumption and exhaust emissions measurements from a single cylinder, stationary diesel engine are described. The engine was fueled with pure marine diesel fuel and blends containing two types of biodiesel, at proportions up to 50%. The two types of biodiesel appeared to have equal performance, and irrespective of the raw material used for their production, their addition to the marine diesel fuel improved the particulate matter, unburned hydrocarbons, nitrogen oxide and carbon monoxide emissions.
► The 95% coverage interval of the measurement of Gross Heat of Combustion of fuel is estimated. ► Two approaches are used, GUM approach and the adaptive Monte Carlo method (MCM). ► The results of ...the two approaches differ considerably. ► The GUM approach underestimates the calculated uncertainties and coverage intervals by up to 7–12%.
The Guide to Uncertainty of Measurement (GUM) approach and the adaptive Monte Carlo method (MCM) provide two alternative approaches for the propagation stage of the uncertainty estimation. These two approaches are implemented and compared concerning the 95% coverage interval estimation of the measurement of Gross Heat of Combustion (GHC) of an automotive diesel fuel by bomb calorimetry. The GUM approach, which assumes either a Gaussian or a
t-distribution for the output quantity (GHC) gives half width intervals of 0.28
MJ
kg
−1 (Gaussian distribution) or 0.29
MJ
kg
−1 (
t-distribution). On the other hand, MCM, which provides a reliable probability density function of GHC through numerical approximation, gives a half width interval of 0.32
MJ
kg
−1. Thus, the GUM approach underestimates the calculated uncertainties and coverage intervals by up to 7–12%. The main reasons of these differences are the approximations and the assumptions introduced by GUM approach, i.e. assumption for the GHC probability distribution and overestimation of effective degrees of freedom by the Welch-Satterwaite formula. Moreover, the estimation and the use of sensitivity coefficients and uncertainty budget within GUM and MCM approaches are examined.
In this study, fatty acid ethyl esters (FAEE) were produced from four different vegetable oils (sunflower, cotton seed, olive oil, and used frying oil) using calcium ethoxide as a heterogeneous solid ...base catalyst. The ester preparation involved a two-step transesterification reaction, followed by purification. The effects of the mass ratio of catalyst to oil, the molar ratio of ethanol to oil, and the reaction temperature were studied on conversion of sunflower oil to optimize the reaction conditions in both stages. The rest of the vegetable oils were converted to ethyl esters under optimum reaction parameters. The optimal conditions for first stage transterification were an ethanol/oil molar ratio of 12:1, catalyst amount (3.5%), and 80°C temperature, whereas the maximum yield of ethyl esters reached 80.5%. In the second stage, the yield of ethyl esters showed signs of improvement of 16% in relation with the one-stage transesterification, which was obtained under the following optimal conditions: catalyst concentration 0.75% and ethanol/oil molar ratio 6:1. Property analysis of prepared ethyl ester samples was done, in order to examine their quality parameters. The results obtained showed that the density, viscosity, and calorific value of the produced ethyl esters had values close to those of a no. 2 diesel. On the contrary, the cold filter plugging points were higher than the conventional diesel fuel.
This paper presents the impact of oxygen and nitrogen compounds on the lubrication properties of low sulfur diesel fuels. It discusses the most recent results, concerning the influence of adding low ...amounts of 4 specific types of biodiesel, 5 aliphatic amines, 2 tertiarty amides, 10 mono-carboxylic acid esters, 3 acetoacetates and 7 esters of di-carboxylic acids on the tribological behaviour of the steel-on-steel systems, lubricated with low sulfur automotive diesel fuel. Experiments were carried out on the HFRR (high frequency reciprocating rig). The obtained wear results showed that all the various classes of additives improved fuel lubricity.
Tobacco seed is a byproduct of tobacco leaves production in Greece. This oil seed was evaluated in the present study, as a renewable and potential source of energy. Successive tobacco seed oil ...extraction indicated that almost 38% of the seed was oil. The major constituents observed by GC analysis were linoleic acid (18:2), oleic acid (18:1) and palmitic acid (16:0). The physical, chemical and fuel related properties of tobacco seed oil were investigated in this work. These properties were comparable to those of other vegetable oils and to current European specifications for automotive diesel fuel. This study suggests that this non edible oil may be an appropriate substitute for diesel fuel. The environmental advantages of tobacco seed oil as a fuel can be exploited for specific niche markets such as inner city vehicles or tractors. On the other hand, tobacco seed oil as a fuel represents one possible hope for the future of EU tobacco agriculture.
To reduce their fuel related logistic burden, North Atlantic Treaty Organization (NATO) Armed Forces are advancing the use of a single fuel for both aircraft and ground equipment. To this end, F-34 ...(the commercial equivalent is Jet A-1) is replacing distillate diesel fuel in many applications. However, tests conducted with this kerosene type on high frequency reciprocating rig showed that this type of fuel causes unacceptable wear. This excessive wear is caused by the poor lubricity of aviation fuel. In order to make this type of fuel compatible with direct injection compression engines, seven di-carboxylic acid esters have tested to improve the lubricity of kerosene. Tribological results showed that all esters tested in this series of experiments seem to be suitable for increasing the kerosene lubricity to a satisfactory level.
The electrochemical behavior of polycrystalline copper in 0.1M LiClO4 methanol solutions has been studied by means of cyclic voltammetry (CV), phase-selective AC voltammetry, electrochemical ...impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM). An investigation of the processes occurring during both positive and negative potential sweep directions is presented. The dependence of differential capacitance on potential, recorded by AC phase-selective tensammetric experiments, reveals surface reconstruction steps related to the formation/reduction of Cu(I)/Cu(II) methoxide surface films. Analysis of EIS data shows that methoxy anion adsorption/desorption takes place in an irreversible way, partially controlled by the diffusion of CH3O−, while the transition from Cu(I) to Cu(II) surface film occurs in parallel to the dissolution of Cu(II) ions through the Cu(II) methoxide film also under mixed kinetic/diffusion control. The stability of surface films formed on the electrode surface has been studied via the SECM tip-substrate voltammetry technique. The obtained results suggest that the monovalent copper methoxide surface layer is stable, while the corresponding divalent copper film exhibits only partially inhibiting properties towards copper dissolution, since a considerable amount of dissolved copper ions was detected in the electrode vicinity.
•Cu electrode in contact with methanol appears to exist in two surface oxidation states in the form of methoxide films.•Cu(I) surface film formation is an irreversible process controlled by the diffusion of methoxy anions to the substrate.•The transition to a Cu(II) methoxide film occurs in parallel to the dissolution of Cu(II) ions through the methoxide film.•Detection of soluble Cu(II) species by SECM measurements unveil the permeable nature of the Cu(II) methoxide surface film.
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