Greater Strength Loss Research Articles

Evaluation of the thermal stability of metakaolin-based geopolymers according to Si/Al ratio and sodium activator

The thermal stability of geopolymer pastes with different Si/Al ratios (1.5–3.0) and sodium activators (Na2SiO3 and/or NaOH) were evaluated in this study. The inclusion of Na2SiO3 induced an active geopolymer reaction, enhancing pre-heating compressive strength, but gradually reduced from 300 °C due to vapor pressure and microstructural deterioration caused by entrapped physically bound water. Conversely, the strength of geopolymers containing only NaOH remained stable or increased up to 600 °C, owing to additional geopolymerization from unreacted raw materials and compact matrix induced by thermal shrinkage. The aluminosilicate networks of all geopolymers remained relatively stable until crystalline nepheline formed above 800 °C; larger crystalline particles were formed in geopolymers with Na2SiO3 owing to its denser geopolymer matrix, whereas smaller crystalline particles were formed in geopolymers with smaller Si/Al and only with NaOH, resulting in fewer voids and stable mechanical strength. Swelling of silica was notable in Na2SiO3-activated geopolymer, resulting in greater strength loss upon heating, indicating that Na2SiO3 hinders the thermal stability of geopolymers at extreme temperatures.

Comparative evaluation of two cetylpyridinium chloride-based mouthwashes on the mechanical properties and strength loss of elastomeric chains used in dentistry: An vitro study

ObjectivesEvaluate the strength degradation of polymeric ligature chains after their immersion in cetylpyridinium chloride-based mouthwashes. Methods240 elastomeric samples from four different manufacturers (Rocky Mountain®, Ormco®, Morelli® and Dentaurum®) in two types of configurations (with and without intermodular links) and divided in 3 groups (distilled water, Vitis CPC Protect® and PERIO·AID® 0.05%) at 5 follow-up periods (0–24 h, 7–14 -21 days) were immersed twice a day for 60 s, following the manufacturers' protocols. A universal traction machine was used to perform the measurements and a post hoc multiple comparisons were based on the Bonferroni test and extended to a 3-way ANOVA test (α = 0.05). ResultsThere was a drop in strength up to 35.9% at 24 h. After a week, the short chains (52%) degraded less than the long ones (57.3%) with significant differences (p < 0.001) and the same pattern was observed until 21 days (p < 0.001). At 24 h, the degradation of the chains exposed in distilled water was 25.8%, in VITIS CPC Protect® 28.6% and in PERIO· AID® 0.05%, 27% with significant differences (p < 0.001). At 21 days, the VITIS CPC Protect® group obtained a much greater loss of strength, being this drop statistically significant (p < 0.001). The chains from Ormco® and RMO® experienced the least loss of force when immersed in the control group or PERIO AID® 0 0.05% (48% and 51%), while Dentaurum's in VITIS CPC Protect® lost more than 75%. ConclusionsThe orthodontic elastomeric chains suffer a sharp drop in strength during the first days of treatment. When comparing the mouthwashes, there were statistically significant differences in terms of strength degradation. Clinical significanceBased on the results, some types of chains, such as the ones without intermodular links from Ormco® showed better properties throughout the study. When immersed in PERIO·AID®0.05%, all showed significantly better results over time. Thus, PERIO·AID®0.05% can be recommended as a complementary oral hygiene element in dental treatments when elastomeric chains are used.

Sustainable approach of applying previous treatment of tire wastes as raw material in cement composites: Review

Rubber as an elastomer is difficult to recycle due to the curing process that undergoes in its various applications, highlighting vulcanization. Tires, particularly, represent a significant amount in disposal of rubber, due to the automobile industry growing over the last decades. Several researchers have been studying its use on civil construction, and in concrete. The results obtained in the researches, with scrap tire rubber as received replacing the concrete constituents, indicated significant reductions in the compressive and flexural strengths, as well as in elasticity module. On the other hand, due to the high capacity of rubber to dissipate energy, rubberized concretes may be suitable for architectural application, false facades, stone baking, interior construction, in building as an earthquake shock wave absorber where resistance to impact or explosion is required and as roof top surfaces for insulation and waterproofing. Various studies highlighted the potential of rubberized concrete acting as a cushion due to its high impact resistance. The use of recycled rubber in Portland cement concrete is not technically successful as in asphalts mixtures due to the incompatibility issues caused by chemical composition and stiffness. After observing the drawbacks caused by the addition of rubber, researchers evaluated their causes, and the main reason was the poor adhesion between cement paste and rubber particle, due to the chemical difference in the polarity of the materials, that affects the cement hydration. Meanwhile, some authors are intended to perform some treatments on the rubber material to enhance the interfacial adhesion with cement hydration products and reduce or eliminate the negative effects while keeping the beneficial effects of waste rubber as an aggregate. Despite of a great loss in strength using tire particles as aggregate in concretes, it was accepted in various applications requiring medium to low compressive strength. On the other hand, rubberized concrete strength may be improved by improving the bond properties of rubber aggregates. Some studies highlighted this possibility by pre-treating the rubber.

Revealing Sex Differences During Upper and Lower Extremity Neuromuscular Fatigue in Older Adults Through a Neuroergonomics Approach.

Background: Sex differences in neuromuscular fatigue is well-documented, however the underlying mechanisms remain understudied, particularly for the aging population. Objective: This study investigated sex differences in fatigability of the upper and lower extremity of older adults using a neuroergonomics approach. Methods: Thirty community-dwelling older adults (65 years or older; 15 M, 15 F) performed intermittent submaximal fatiguing handgrip and knee extension exercises until voluntary exhaustion on separate days. Muscle activity from prime muscles of the hand/arm and knee extensors were monitored using electromyography, neural activity from the frontal, motor, and sensory areas were monitored using functional near infrared spectroscopy, and force output were obtained. Results: While older males were stronger than females across both muscle groups, they exhibited longer endurance times and greater strength loss during knee extension exercises. These lower extremity findings were associated with greater force complexity over time and concomitant increase in left motor and right sensory motor regions. While fatigability during handgrip exercises was comparable across sexes, older females exhibited concurrent increases in the activation of the ipsilateral motor regions over time. Discussion: We identified differences in the underlying central neural strategies adopted by males and females in maintaining downstream motor outputs during handgrip fatigue that were not evident with traditional ergonomics measures. Additionally, enhanced neural activation in males during knee exercises that accompanied longer time to exhaustion point to potential rehabilitation/exercise strategies to improve neuromotor outcomes in more fatigable older adults.

Neural Signatures of Handgrip Fatigue in Type 1 Diabetic Men and Women.

Type 1 diabetes (T1D) is associated with reduced muscular strength and greater muscle fatigability. Along with changes in muscular mechanisms, T1D is also linked to structural changes in the brain. How the neurophysiological mechanisms underlying muscle fatigue is altered with T1D and sex related differences of these mechanisms are still not well investigated. The aim of this study was to determine the impact of T1D on the neural correlates of handgrip fatigue and examine sex and T1D related differences in neuromuscular performance parameters, neural activation and functional connectivity patterns between the motor regions of the brain. Forty-two adults, balanced by condition (healthy vs T1D) and sex (male vs female), and performed submaximal isometric handgrip contractions until voluntary exhaustion. Initial strength, endurance time, strength loss, force variability, and complexity measures were collected. Additionally, hemodynamic responses from motor-function related cortical regions, using functional near-infrared spectroscopy (fNIRS), were obtained. Overall, females exhibited lower initial strength (p < 0.0001), and greater strength loss (p = 0.023) than males. While initial strength was significantly lower in the T1D group (p = 0.012) compared to the healthy group, endurance times and strength loss were comparable between the two groups. Force complexity, measured as approximate entropy, was found to be lower throughout the experiment for the T1D group (p = 0.0378), indicating lower online motor adaptability. Although, T1D and healthy groups fatigued similarly, only the T1D group exhibited increased neural activation in the left (p = 0.095) and right (p = 0.072) supplementary motor areas (SMA) over time. A sex × condition × fatigue interaction effect (p = 0.044) showed that while increased activation was observed in both T1D females and healthy males from the Early to Middle phase, this was not observed in healthy females or T1D males. These findings demonstrate that T1D adults had lower adaptability to fatigue which they compensated for by increasing neural effort. This study highlights the importance of examining both neural and motor performance signatures when investigating the impact of chronic conditions on neuromuscular fatigue. Additionally, the findings have implications for developing intervention strategies for training, rehabilitation, and ergonomics considerations for individuals with chronic conditions.

Development of a micro-scale method to assess the effect of corrosion on the mechanical properties of a biodegradable Fe-316L stent material

The application of biodegradable materials to stent design has the potential to transform coronary artery disease treatment. It is critical that biodegradable stents have sustained strength during degradation and vessel healing to prevent re-occlusion. Proper assessment of the impact of corrosion on the mechanical behaviour of potential biomaterials is important. Investigations within literature frequently implement simplified testing conditions to understand this behaviour and fail to consider size effects associated with strut thickness, or the increase in corrosion due to blood flow, both of which can impact material properties. A protocol was developed that utilizes micro-scale specimens, in conjunction with dynamic degradation, to assess the effect of corrosion on the mechanical properties of a novel Fe-316L material. Dynamic degradation led to increased specimen corrosion, resulting in a greater reduction in strength after 48 h of degradation in comparison to samples statically corroded. It was found that thicker micro-tensile samples (h > 200 μm) had a greater loss of strength in comparison to its thinner counterpart (h < 200 μm), due to increased corrosion of the thicker samples (203 MPa versus 260 MPa after 48 h, p = 0.0017). This investigation emphasizes the necessity of implementing physiologically relevant testing conditions, including dynamic corrosion and stent strut thickness, when evaluating potential biomaterials for biodegradable stent application.

Thermal Action on Normal and High Strength Cement Mortars

High temperature effect on cement-based composites, such as concrete or mortars, represents one of the most important damaging process that may drastically affect the mechanical and durability characteristics of structures. In this paper, the results of an experimental campaign on cement mortars submitted to high temperatures are reported and discussed. Particularly, two mixtures (i.e., Normal (MNS) and High Strength Mortar (MHS)) having different water-to-binder ratios were designed and evaluated in order to investigate the incidence of both the mortar composition and the effects of thermal treatments on their physical and mechanical properties. Mortar specimens were thermally treated in an electrical furnace, being submitted to the action of temperatures ranging from 100 to 600 °C. After that and for each mortar quality and considered temperature, including the room temperature case of 20 °C, water absorption was measured by following a capillary water absorption test. Furthermore, uniaxial compression, splitting tensile and three-points bending tests were performed under residual conditions. A comparative analysis of the progressive damage caused by temperature on physical and mechanical properties of the considered mortars types is presented. On one hand, increasing temperatures produced increasing water absorption coefficients, evidencing the effect of thermal damages which may cause an increase in the mortars accessible porosity. However, under these circumstances, the internal porosity structure of lower w/b ratio mixtures results much more thermally-damaged than those of MNS. On the other hand, strengths suffered a progressive degradation due to temperature rises. While at low to medium temperatures, strength loss resulted similar for both mortar types, at higher temperature, MNS presented a relatively greater strength loss than that of MHS. The action of temperature also caused in all cases a decrease of Young’s Modulus and an increase in the strain corresponding to peak load. However, MHS showed a much more brittle behavior in comparison with that of MNS, for all temperature cases. Finally, the obtained results demonstrated that mortar quality cannot be neglected when the action of temperature is considered, being the final material performance dependent on the physical properties which, in turn, mainly depend on the mixture proportioning.

New insights into the early reaction of NaOH-activated slag in the presence of CaSO4

This study focused on the reaction and initial setting of NaOH-activated slag with different CaSO4 contents. The macroscopic properties were firstly investigated, and then the reaction process was monitored using a micro-reactor method and a combination of exothermic rate, element concentration and semi-quantification of precipitates. The results prove that there is a proper dosage for CaSO4 as a retarder (specifically, 4 wt% in this study). Below this value, CaSO4 does not retard the reaction; above this value, there is a significant retardation, but also a great loss in compressive strength. The retardation is mainly attributed to the inhibition of high Ca2+ concentration (dissolved from CaSO4) on the slag dissolution, rather than the decreased pH or the effect of SO42−.

Implications of Bond-Slip in Inelastic Dynamic Responses of Degrading Structural Systems

The influence of bond-slip behavior, shown by pinched hysteretic curves in the inelastic response of degrading structural systems, is investigated in this paper. Inelastic response spectra are calculated and compared for deteriorating structures with and without manifestation of bond-slip. The response spectra are generated by using a smooth hysteretic model with distinct degrading parameters that are calibrated to the generic inelastic envelopes. In addition to the ductility demands, degraded residual strengths and stiffness of structural systems after an earthquake are considered as the relevant response measures. These measures can serve as design parameters for structures that should remain functional after an extreme event. Based on the response spectra analyses, it is found that nonlinear responses of degrading structural systems with bond-slip develop larger ductility demands and greater loss of strength and stiffness than the responses without bond-slip. Numerical results show that, ductility demand is increased up to 25–100% with consideration of slip in the model, as well as residual strength and stiffness decreased up to almost half.

Deterioration Process of Concrete Exposed to Internal Sulfate Attack.

Damage to concrete structures with gypsum-contaminated aggregate occurs frequently. Aggregates in much of the southern part of China are contaminated with gypsum. Therefore, in this study, the effects of using different quantities of gypsum-contaminated aggregate on the expansion and compressive strength of concrete were investigated over a period of one year. Two groups of concrete were designed with the gypsum-contaminated aggregate containing different parts of fine and coarse aggregate, respectively. The SO3 contents were 0%, 0.5%, 1%, 1.5%, 3%, 5%, and 7% by weight of aggregate. X-ray diffraction (XRD), thermogravimetry (TG), and differential scanning calorimetry (DSC) were used to analyze the change in mineral composition over time. The microstructure was also studied by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results showed that significant expansion and great loss in compressive strength did not occur in concrete if the content of SO3 lay below 1.5% and 3% in fine and coarse aggregates, respectively. The concentration of sulfate ions in concrete was not enough to form new a phase of gypsum. During the process of internal sulfate attack, the content of gypsum decreased and the content of ettringite increased. Ettringite was the main reason for the expansion damage of concrete. Additionally, the fracture mode of internal sulfate attack on concrete was the crack extension from gypsum to paste; finally, the aggregate separated from the paste.

Degradation of cast-in-situ concrete subjected to sulphate-chloride combined attack

The main aim of the present research is to determine the degradation mechanisms of cast-in-situ concrete subjected to sulphate-chloride combined attack. Concrete specimens were prepared and then put into sulfate or sulfate-chloride mixed solutions. The sample dimension, mass, compressive strength, and sulfate concentration of the specimens were continuously monitored. The microstructures and the complex mineral composition of the concrete were analysed after 12 months of exposure to the corrosive environments. The results show that cast-in-situ concrete suffers more severe damage and greater strength loss when subjected to sulfate-chloride combined attack than when subjected to sulfate only. The diffusion and accumulation of sulfates are accelerated by the coexisting chlorides, especially in the early stages. The coexistence of chlorides in sulfate environments accelerates the degradation of cast-in-situ concrete induced by sulfate attack. The different performances against sulfate-chloride combined attack between cast-in-situ and precast concrete were mainly due to the degradation behaviour at the early stage.

Вплив типу в'язального обладнання на показники втрати міцності поліетиленових та параарамідних ниток після в'язання

This article presents the results of a study of the effect of type of knitting equipment on the loss of strength of high molecular weight polyethylene (PE) and para-aramid (PA) filaments after knitting, as well as when combined in the process of knitting with a metal monofilament. Samples of knitted fabrics are made by interlacing the cooling surface on two types of flat-knitting equipment of the 8th class: the flat-type machine PVRK and the glove machine PA-8-33 (RA). In the process of knitting, the length of the thread in the loop remained the same (l = 8.9mm). In accordance with the existing methodology, the value of the breaking load and the elongation of the yarns before and after knitting on the KaoTieh KT-7010AZ breaking machine was established. To estimate the loss of thread strength after knitting, the use factor of strength, which is the ratio of the strength of the thread after and before knitting, was used. As a result of the experiment, it is found that the coefficient of PA strength of the yarn of knitwear samples without introduction into the metal monofilament structure, in comparison with PE, increases regardless of the type of knitting equipment. When introduced into the structure of a metal monofilament, regardless of the type of knitting equipment, the coefficient of PA strength of the filament compared to the PE increases. Thus, the PE filaments, when processing them into the structure of knitwear, weave loosening, to a greater extent, lose their strength, which is explained by the peculiarities of the original polymer. PE filaments are more sensitive to elongation at power loads and destruction of individual fibers due to interaction with the metal monofilament. This causes a greater loss of strength in the knitting process of the PE thread itself, which by its structure is a multifilament non-twisted thread. The characteristics of the loss of strength of high-molecular-weight polyethylene and para-aramid threads obtained in the structure of the knit fabric knit fabric, obtained in the course of the researches, give the opportunity to form the specified properties of knitwear in the final product. Keywords : tensile load, tensile elongation, strength factor, loss of strength, high strength raw material, high molecular weight polyethylene filament, para-aramid filament, metallic monofilament.

Stress corrosion cracking of simulated heat-affected zone in a CF8A weld in high temperature water

In this study, thermal simulation was performed to conduct thermal cycles on CF8A cast austenitic stainless steel substrates with different ferrite contents to simulate the microstructures that form near a weld fusion boundary. The effects of ferrite content and morphology on the mechanical properties of CF8A were investigated. The stress corrosion cracking (SCC) susceptibility of the specimens was evaluated with slow strain rate tensile (SSRT) tests in a simulated boiling water reactor (BWR) coolant environment.The results indicated that an increase in the ferrite content of the CF8A base metal led to a minor increase in hardness. Thermal simulation caused a marked increase in ferrite content, especially in the high ferrite CF8A substrate. The yield strengths of the tested samples increased obviously with increasing ferrite content, but the ductility decreased. The ultimate tensile strengths of the samples reached a plateau when the ferrite number (FN) was greater than 18. The applied thermal simulation greatly improved the impact toughness of high ferrite CF8A in comparison with the original substrate. The results indicated that the samples with high ferrite content had a shorter rupture life but greater fracture strength than those with low ferrite content strained in high temperature water. Moreover, cleavage-like fracture was found in all of the samples that suffered from SCC. The SCC cracks were observed to be more likely to propagate along the δ/γ interfaces of a CF8A. Furthermore, crack initiation and growth inside the γ of low ferrite CF8A contributed to a great loss in strength in a high temperature water environment.

Knee Muscle Torque and H:Q Ratio Changes before ACL Surgery and after Rehabilitation

Research background and hypothesis. Anterior cruciate ligament (ACL) of the knee joint is often quite a fragile structure of the knee. After the rupture of ACL neuromuscular control worsens and sensorimotor system breaks down (Risberg et al., 2007), muscle activation is poor and muscle strength decreases (Croce, Miller, 2006). Some authors have reported greater strength loss in quadriceps femoris than in hamstring femoris muscle (Busch-Joseph et al., 2001; Neeter et al., 2006), therefore we hypothesized that strength loss in knee extensors may affect hamstring/quadriceps torque (H:Q) ratio. Research aim of this study was to investigate knee extensors and fl exors isometric and dynamic torque and H:Q ratio alterations before ACL surgery and after rehabilitation.Research methods. Ten volunteers with ACL ruptured knee where tested before surgery and after rehabilitation. Isokinetic dynamometer was used for this testing. Maximal isometric torque was performed during fl exion and extension at 90°, 60º knee angles. Dynamic torque was performed at 30, 180, 300º/s angular velocities.Research results. Results of this study show that after rehabilitation isometric and dynamic torque of the involved leg decreased. Isometric fl exion and extension torque of the uninjured leg was greater than that of the injured leg, but after rehabilitation the extension torque of the injured leg was lower than that before surgery. Discussion and conclusions. Before ACL surgery and after rehabilitation quadriceps femoris muscle torque of the uninjured leg was more affected than hamstring femoris muscle torque. After rehabilitation H:Q ratio of the injured leg was not dependent on angular velocity and knee joint angle.Keywords: maximal voluntary torque, muscle balance, muscle contraction.

Effect of high temperature on strength and mass loss of admixtured concretes

Chemical admixtures are used in concretes to prove some properties at ambient temperature. The admixtured concretes may present different behaviour at high temperature than at normal conditions. In this study, five different types of chemical admixtures – Superplasticizers (SP), hardening accelerators (HA), setting retarders (SR), air entrainers (AE) and water repellents (WR) – Were incorporated with different fraction of cement mass (0.5, 1.0, 1.5 and 2.0%), to investigate their influences on the strength and mass losses of concretes under high temperature. This study concerns the behaviour of admixtured concretes at ambient temperature 20 °C (normal conditions) and those subjected to temperatures 105 °C (oven dry) and 300 °C with a rate of 2 °C/min. Compressive-strength and mass loss tests were performed on the samples 10 × 10 × 10 cm3which were cooled up slowly to ambient temperature. It was concluded that among the chemical admixtures used, the superplasticizer (SP) significantly increased the workability of SPC. The tests results indicated that at a temperature of 300° C, the concrete with an air entrainer admixture caused the greatest loss of strength and mass when compared with others admixtured concretes. The lowest losses are those obtained for concretes with superplasticizers at this temperature.

Blunted Myoglobin and Quadriceps Soreness After Electrical Stimulation During the Luteal Phase or Oral Contraception

ABSTRACTPurpose: Acute muscle damage after exercise triggers subsequent regeneration, leading to hypertrophy and increased strength after repeated exercise. It has been debated whether acute exercise-induced muscle damage is altered under various premenopausal estrogen conditions. Acute contraction-induced muscle damage was compared during exogenous (oral contraceptive, OC), endogenous (luteal phase, HI), or low (menses, LO) estrogen in healthy young women aged 21 to 30 years old. Methods: Women (OC, n = 9; HI, n = 9; LO, n = 8; total N = 26) performed 1 neuromuscular electrical stimulation (NMES) bout. Soreness, measured via visual analog scale and the Likert Scale of Muscle Soreness for Lower Limb (LSMSLL), quadriceps strength, and plasma myoglobin (Mb), interleukin (IL)-6, IL-8, and granulocyte-colony stimulating factor were measured before and after NMES. Results: NMES performance was similar across groups. Meaningful within-group increases in Mb (effect size [ES] = 1.12) and IL-8 (ES = 0.38) occurred in LO; ES for HI and OC were trivial. ES of the between-group difference in change was moderate for Mb (LO vs. HI = 1.15) and IL-8 (LO vs. HI = 0.86; LO vs. OC = 0.73). 17-β estradiol correlated moderately and negatively with Mb relative change (r = –.52, p < .05). LO had ~5% greater strength loss than OC and HI. The mean change score for the LSMSLL 2 days post-NMES was clinically greater in LO than OC or HI. Conclusions: Acute NMES-induced indicators of muscle fiber damage and qualitative muscle soreness may be attenuated during the luteal phase or active OC pill consumption compared with the menstrual phase.

Acid, Alkali and Chloride Resistance of High Volume Fly Ash Concrete

Objectives: To find variation in compressive strength and mass of high volume fly ash concrete samples subjected to different chemical solutions of sodium chloride, sodium sulphate and sulphuric acid. Methods: A total of 900 numbers of cubes were cast and cured with four levels of curing period of 28, 56, 90 and 120 days. After certain duration of curing period, specific numbers (60) of cubes were submerged each in 5 percent sodium sulphate solution (Na2SO4), 5 percent sodium chloride solution (NaCl) and 1percent of sulphuric acid solution (H2SO4) separately in chemical exposure containers for an exposure period of 30, 60, 90 and 120 days. Findings: Investigations with respect to acid, alkali and chloride resistance were carried out on high volume fly ash concrete, HFC (40 percent replacement with cement), low volume fly ash concrete, LFC (25 percent replacement with cement) and their performances against control concrete (NC) is presented in this paper. Their performance was measured with respect to the loss in compressive strength and weight of the concrete cubes over the period of exposure time. It is found that the resistance of control concrete to all the three chemical attack is better only up to 28 days of water curing. At 56 days of water curing LFC shows better resistance against the control and HFC. However, with prolonged water curing of cubes of 90 days and more, HFC has consistently shown highest resistance; whereas the control concrete faced a great loss in strength.

English

This study attempted to focus on the performance evaluation of 100% viscose rayon fabric in terms of strength, whiteness and hydrophilicity or absorbency after scouring and bleaching with two different alkalis such as NaOH and Na2CO3. This work was carried out with 100% viscose rayon knitted fabrics. A single stage scouring and bleaching process of the fabric was adopted using NaOH and Na2CO3 with varying concentrations and at the same processing conditions. The result obtained in this study indicated a great loss in strength with NaOH as compared to that with Na2CO3. Both the alkalis were found to be more or less equally efficient in terms of improved absorbency and whiteness.

External rotator sparing with posterior acetabular fracture surgery: does it change outcome?

This study analyses the results of the treatment with external rotator sparing approach in acetabular fractures to determine whether muscle sparing has a positive impact on functional outcome. 20 patients with a mean age of 45.9 years (range: 26–64) that had been treated for displaced acetabular fractures were included in this series. Short Musculoskeletal Function Assessment (SMFA) questionnaire and hip muscle strength measurement were done at the 24-month of follow-up period. The radiographic results at the final followup were excellent in 9 hips (45%), good in 6 hips (30%), fair in 4 hips (20%), and poor in one hip (5%) according to the criteria developed by Matta. The average SMFA score for all of the patients was 18.3 (range: 0–55.4). The mean dysfunctional and bother indexes were 17.2 and 20.6, respectively. The overall muscle strength deficit was 11.8%. The greatest loss of strength was in internal rotation. In patients with better postoperative reduction quality of acetabular fracture, peak torque, and maximum work of hip flexion, extension and also internal rotation maximum work deficit were significantly lower (P < 0.05). Accurate initial reduction and longer postoperative muscle strengthening exercise programs seem critical to decrease postoperative hip muscle weakness after acetabular fractures.

Mechanical annealing of cryorolled Zr

Thermal annealing is usually employed to enhance the ductility of deformed materials, but always leads to a great loss in strength. In this study, we report an abnormal mechanical annealing behavior, i.e. a significant reduction of dislocation density with increasing compression strain, in the cryorolled Zr treated with high-pressure confinement deformation. A good combination of high strength and ductility has been achieved in the mechanically annealed sample. This unusual mechanical annealing behavior results from the motion of preexisting high-density dislocations in the cryorolled Zr under high stress. The high ductility of the mechanically annealed sample is attributed to the restoration of work hardening capability and grain boundary related deformations, while the high strength is due to the formation of nano-scale subgrains and grains in the sample. The observed mechanical annealing phenomenon can be employed to tailor microstructure and enhance the mechanical properties of deformed materials, and thus is of wide interest for the development of advanced structural materials with high strength and ductility.