Metal artifacts from titanium and steel screws in CT, 1.5T and 3T MR images of the tibial Pilon: A quantitative assessment in 3D

Radiographs are commonly used to assess articular reduction of the distal tibia (pilon) fractures postoperatively, but may reveal malreductions inaccurately. While Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) are potential 3D alternatives they generate metal-related artifacts. This study aims to quantify the artifact size from orthopaedic screws using CT, 1.5T and 3T MRI data. Three screws were inserted into one intact human cadaver ankle specimen proximal to and along the distal articular surface, then CT, 1.5T and 3T MRI scanned. Four types of screws were investigated: titanium alloy (TA), stainless steel (SS) (Ø = 3.5 mm), cannulated TA (CTA) and cannulated SS (CSS)(Ø = 4.0 mm, Ø empty core = 2.6 mm). 3D artifact models were reconstructed using adaptive thresholding. The artifact size was measured by calculating the perpendicular distance from the central screw axis to the boundary of the artifact in four anatomical directions with respect to the distal tibia. The artifact sizes (in the order of TA, SS, CTA and CSS) from CT were 2.0 mm, 2.6 mm, 1.6 mm and 2.0 mm; from 1.5T MRI they were 3.7 mm, 10.9 mm, 2.9 mm, and 9 mm; and 3T MRI they were 4.4 mm, 15.3 mm, 3.8 mm, and 11.6 mm respectively. Therefore, CT can be used as long as the screws are at a safe distance of about 2 mm from the articular surface. MRI can be used if the screws are at least 3 mm away from the articular surface except SS and CSS. Artifacts from steel screws were too large thus obstructed the pilon from being visualised in MRI. Significant differences (P < 0.05) were found in the size of artifacts between all imaging modalities, screw types and material types, except 1.5T versus 3T MRI for the SS screws (P = 0.063). CTA screws near the joint surface can improve postoperative assessment in CT and MRI. MRI presents a favourable non-ionising alternative when using titanium hardware. Since these factors may influence the quality of postoperative assessment, potential improvements in operative techniques should be considered.

Numerical studies on CFRP strengthened steel columns under transverse impact

Strengthening of metallic structures using carbon fibre reinforced polymer (CFRP) has become a smart strengthening option over the conventional strengthening method. Transverse impact loading due to accidental vehicular collision can lead to the failure of existing steel hollow tubular columns. However, knowledge is very limited on the behaviour of CFRP strengthened steel members under dynamic impact loading condition. This paper deals with the numerical simulation of CFRP strengthened square hollow section (SHS) steel columns under transverse impact loading to predict the behaviour and failure modes. The transverse impact loading is simulated using finite element (FE) analysis based on numerical approach. The accuracy of the FE modelling is ensured by comparing the predicted results with available experimental tests. The effects of impact velocity, impact mass, support condition, axial loading and CFRP thickness are examined through detail parametric study. The impact simulation results indicate that the strengthening technique shows an improved impact resistance capacity by reducing lateral displacement of the strengthened column about 58% compared to the bare steel column. Axial loading plays an important role on the failure behaviour of tubular column.

Protection by methylproamine of irradiated human keratinocytes correlates with reduction of DNA damage

Purpose: The therapeutic ratio for ionising radiation treatment of tumour is a trade-off between normal tissue side-effects and tumour control. Application of a radioprotector to normal tissue can reduce side-effects. Here we study the effects of a new radioprotector on the cellular response to radiation. Methylproamine is a DNA-binding radioprotector which, on the basis of published pulse radiolysis studies, acts by repair of transient radiation-induced oxidative species on DNA. To substantiate this hypothesis, we studied protection by methylproamine at both clonogenic survival and radiation-induced DNA damage, assessed by γH2AX (histone 2AX phosphorylation at serine 139) focus formation endpoints. Materials and methods: The human keratinocyte cell line FEP1811 was used to study clonogenic survival and yield of γH2AX foci following irradiation (137Cs γ-rays) of cells exposed to various concentrations of methylproamine. Uptake of methylproamine into cell nuclei was measured in parallel. Results: The extent of radioprotection at the clonogenic survival endpoint increased with methylproamine concentration up to a maximum dose modification factor (DMF) of 2.0 at 10 μM. At least 0.1 fmole/nucleus of methylproamine is required to achieve a substantial level of radioprotection (DMF of 1.3) with maximum protection (DMF of 2.0) achieved at 0.23 fmole/nucleus. The γH2AX focus yield per cell nucleus 45 min after irradiation decreased with drug concentration with a DMF of 2.5 at 10 μM. Conclusions: These results are consistent with the hypothesis that radioprotection by methylproamine is mediated by attenuation of the extent of initial DNA damage.

A new study on binder performance and formulation modification of anti-corrosive primer based on ethyl silicate resin

Zinc-rich ethyl silicate coatings are quite successful in protecting steel against corrosion under severe exposing conditions. In spite of providing excellent cathodic protection to steel structure after film curing, two-component zinc-rich ethyl silicate coatings have some limitations, one of which is inadequate shelf life as a result of in-can binder gelation. In this work, the preparation steps of ethyl silicate such as pre-hydrolysis, dehydration and organometallic reactions were surveyed and herein an approach towards understanding the cause and effect relationship of the use of ingredients is presented. The effects of water and catalytic acid dosages on gel time under accelerated conditions and the effect of alcoholic solvent order on the rate of the hydrolysis and dehydration reactions were studied via Karl-Fischer test determining the water content of hydrolysate. A thriving optimization in shelf life without any loss in physical–mechanical characteristics of the final film (e.g. hardness, adhesion, solvent and salt spray resistance) was obtained.

Unusually cold and dry winters increase mortality in Australia

Seasonal patterns in mortality have been recognised for decades, with a marked excess of deaths in winter, yet our understanding of the causes of this phenomenon is not yet complete. Research has shown that low and high temperatures are associated with increased mortality independently of season; however, the impact of unseasonal weather on mortality has been less studied. In this study, we aimed to determine if unseasonal patterns in weather were associated with unseasonal patterns in mortality. We obtained daily temperature, humidity and mortality data from 1988 to 2009 for five major Australian cities with a range of climates. We split the seasonal patterns in temperature, humidity and mortality into their stationary and non-stationary parts. A stationary seasonal pattern is consistent from year-to-year, and a non-stationary pattern varies from year-to-year. We used Poisson regression to investigate associations between unseasonal weather and an unusual number of deaths. We found that deaths rates in Australia were 20–30% higher in winter than summer. The seasonal pattern of mortality was non-stationary, with much larger peaks in some winters. Winters that were colder or drier than a typical winter had significantly increased death risks in most cities. Conversely summers that were warmer or more humid than average showed no increase in death risks. Better understanding the occurrence and cause of seasonal variations in mortality will help with disease prevention and save lives.

Cold water immersion enhances recovery of submaximal muscle function after resistance exercise

We investigated the effect of cold water immersion (CWI) on the recovery of muscle function and physiological responses following high-intensity resistance exercise. Using a randomized, cross-over design, 10 physically active men performed high-intensity resistance exercise, followed by one of two recovery interventions: 10 min of cold water immersion at 10°C, or 10 min active recovery (low-intensity cycling). After the recovery interventions, maximal muscle function was assessed after 2 h and 4 h by measuring jump height and isometric squat strength. Submaximal muscle function was assessed after 6 h by measuring the average load lifted during six sets of 10 squats at 80% 1RM. Intramuscular temperature (1 cm) was also recorded, and venous blood samples were analyzed for markers of metabolism, vasoconstriction and muscle damage. CWI did not enhance recovery of maximal muscle function. However, during the final three sets of the submaximal muscle function test, the participants lifted a greater load (p<0.05; 38%; Cohen’s d 1.3) following CWI compared with active recovery. During CWI, muscle temperature decreased 6°C below post-exercise values, and remained below pre-exercise values for another 35 min. Venous blood O2 saturation decreased below pre-exercise values for 1.5 h after CWI. Serum endothelin-1 concentration did not change after CWI, whereas it decreased after active recovery. Plasma myoglobin concentration was lower, whereas plasma interleukin-6 concentration was higher after CWI compared with active recovery. These results suggest that cold water immersion after resistance exercise allow athletes to complete more work during subsequent training sessions, which could enhance long-term training adaptations.

Finite element analysis of CFRP strengthened steel hollow sections under tension

This paper presents a nonlinear finite element (FE) model for the analysis of very high strength (VHS) steel hollow sections wrapped by high modulus carbon fibre rein forced polymer (CFRP) sheets. The bond strength of CFRP wrapped VHS circular steel hollow section under tension is investigated using the FE model. The three dimensional FE model by Nonlinear static analysis has been carried out by Strand 7 finite element software. The model is validated by the experimental data obtained from Fawzia et al [1]. A detail parametric study has been performed to examine the effect of number of CFRP layers, different diameters of VHS steel tube and different bond lengths of CFRP sheet. The analytical model developed by Fawzia et al. [1] has been used to determine the load carrying capacity of different diameters of CFRP strengthened VHS steel tube by using the capacity from each layer of CFRP sheet. The results from FE model have found in reasonable agreement with the analytical model developed by Fawzia et al [1]. This validation was necessary because the analytical model by Fawzia et al [1] was developed by using only one diameter of VHS steel tube and fixed (five) number of CFRP layers. It can be concluded that the developed analytical model is valid for CFRP strengthened VHS steel tubes with diameter range of 38mm to 100mm and CFRP layer range of 3 to 5 layers. Based on the results it can also be concluded that the effective bond length is consistent for different diameters of steel tubes and different layers of CFRP. Three layers of CFRP is considered most effective wrapping scheme due to the cost effectiveness. Finally the distribution of longitudinal and hoop stress has been determined by the finite element model for different diameters of CFRP strengthened VHS steel tube.

Finite element modeling of carbon fibre reinforced polymer (CFRP) strengthened steel tubes under axial impact

Steel hollow sections used in structures such as bridges, buildings and space structures involve different strengthening techniques according to their structural purpose and shape of the structural member. One such technique is external bonding of CFRP sheets to steel tubes. The performance of CFRP strengthening for steel structures has been proven under static loading while limited studies have been conducted on their behaviour under impact loading. In this study, a comprehensive numerical investigation is carried out to evaluate the response of CFRP strengthened steel tubes under dynamic axial impact loading. Impact force, axial deformation impact velocities are studied. The results of the numerical investigations are validated by experimental results. Based on the developed finite element (FE) model several output parameters are discussed. The results show that CFRP wrapping is an effective strengthening technique to increase the axial dynamic load bearing capacity by increasing the stiffness of the steel tube.

Dynamic simulation of CFRP strengthened steel column under impact loading

Carbon fibre reinforced polymer (CFRP) strengthening of metallic structures under static loading has shown great potential in the recent years. However, steel structures are often experienced natural (e.g. earthquake, wind) as well as man-made (e.g. vehicular impact, blast) dynamic loading. Therefore, there is a growing interest among the researchers to investigate the capability of CFRP strengthened members under such dynamic conditions. This study focuses on the finite element (FE) numerical modelling and simulation of CFRP strengthened steel column under transverse impact loading to predict the behaviour and failure modes. Impact simulation process and the CFRP strengthened steel column are validated with the existing experimental results in literature. The validated FE model of CFRP strengthened steel column is then further used to investigate the effects of transverse impact loading on its structural performance. The results are presented in terms of transvers e impact force, lateral and axial displacement, and deformed shape to evaluate the effectiveness of CFRP strengthening technique. Comparisons between the bare steel and CFRP strengthened steel columns clearly indicate the performance enhancement of strengthened column under transverse impact loading.

Durability study of CFRP strengthened steel circular hollow section members under marine environment

Galvanic corrosion is a common phenomenon in Carbon Fibre Reinforced Polymer (CFRP) strengthened steel structures in wet environments and submerged conditions, which reduces durability by weakening the bond between the CFRP and steel substrate. CFRP materials have already been proven to have superior resistance to corrosion and chemical attacks but the adhesive and steel are generally affected by long-term exposure to moisture, especially in conjunction with salts resulting from deicing of ocean spray. This paper presents the results of a research program to improve the durability of CFRP strengthened steel circular hollow section (CHS) members by treating the steel surface with an epoxy based adhesion promoter and inserting Glass Fibre Reinforced Polymer (GFRP) as a galvanic corrosion barrier against simulated sea water. It also presents the effects of accelerated corrosion on the bond of CFRP strengthened hollow steel members. The program consisted of four CFRP strengthened steel beams and one unstrengthened steel beam. Two strengthened beams were used as control while the other two beams were exposed to a highly corrosive environment to induce accelerated corrosion. The corrosion rate was considered 10% which represents a moderate level of loss in the cross-sectional area of the steel tube throughout its intended service life. The beams were then loaded to failure under four-point bending. The research findings indicate that the accelerated corrosion adversely affected the ultimate strength of the conditioned beams and the embedded glass fibre enhanced the bond durability.