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Copper matrix composites with dual-scale particles were fabricated through casting with reaction. Ultrasonic vibration has been successfully introduced into the melt at about 1523 K while the microstructural development and mechanism of copper matrix composites with high-performance through a novel method of casting with ultrasonic vibration treatment are investigated. When ultrasonic vibration is applied, the distribution of micro-scale particles is greatly improved. Primary Cr phase convents to non-dendrite and large aggregates of ZrB2 particles are disrupted into small clusters because of acoustic cavitation and acoustic streaming. The ultimate tensile strength and elongation of Cu-1wt%Cr-0.3 wt%Zr-1wt%ZrB2 composite in as-cast state were 321 MPa and 14.37 %, recording a 28.4 % and 14 % increment respectively compared with the sample without treatment. After solution treatment, deformation and aging subsequently, the uniform distribution of reinforcements also decreases the average transverse grain thickness and increases the dislocation density which improve the comprehensive properties.

Abstract Bone resection is highly valued in total knee arthroplasty (TKA), but how to determine the amount of distal femur resection is still controversial. The purpose of this study was to explore how to use lateral condyle as a reference for distal femoral osteotomy in TKA. Magnetic resonance imaging (MRI) and Radiographic images from 118 nonarthritic subjects and 123 osteoarthritis (OA) subjects were used to assess the cartilage wear pattern of the distal femur in varus knees. Measurements were performed on three-dimensional reconstruction after virtual bone cutting. The difference between the resection amount of distal (0°) and posterior (90°) was calculated when the medial condyle was used as a reference in OA patients. The osteotomy amount on lateral was calculated in nonarthritic subjects when the medial condylar osteotomy was consistent with the thickness of the implants. In 43% of OA patients, there was > 1 mm difference between the 0° and 90° in medial condyle cartilage, and no difference was observed in lateral. When using medial condyle as a reference for osteotomy, there was a difference of 1.3 ± 0.56 mm between the resection amount of 0° and 90°, and the difference was 0.24 ± 0.27 mm when using lateral condyle. Statistical analysis showed that there was a linear correlation between the resection amount of lateral condyle and mechanical lateral distal femoral angle (mLDFA) in nonarthritic subjects (r = 0.845, p

The strength and plasticity trade-off in metal materials can be effectively addressed by Eutectic High-Entropy Alloys (EHEAs) through the realization of heterogeneous biphase layered structures at both micrometer and nanometer scales. In this work, a series of (CoCrFeNi)88NbxW(12-x) EHEAs were prepared, and the effects of the synergistic of Nb and W elements on the microstructure and mechanical properties of CoCrFeNi High-Entropy Alloys (HEAs) were investigated. With the increase of Nb content and the decrease of W content, the microstructure of the alloy underwent three changes, from Face Center Cubic (FCC) + μ biphase to FCC + μ + Laves triple phase, and finally to FCC + Laves biphase. The strength of the alloy increases, but the compression rate decreases. Among these alloys, (CoCrFeNi)88Nb10W2 alloy exhibits exceptional mechanical properties. The synergistic effect of precipitation strengthening and grain boundary strengthening makes the yield strength, fracture strength, and plastic strain of the alloy are 1568 MPa, 2516 MPa, and 32 % respectively. In addition, in the CoCrFeNi HEAs, the weighted average atomic radius ratio (rm‾/rQ) is used to further precise the phase selection law of Laves phase and μ phase. When rm‾/rQ < 1.112, HEAs forms the μ phase, when 1.112 ≤ rm‾/rQ ≤ 1.14, HEAs forms the Laves + μ biphase, when rm‾/rQ > 1.14, HEAs forms the Laves phase. The results can provide a basis for synergistic strengthening and phase selection of CoCrFeNi HEAs.

The thermoelectric (TE) performance of p-type ZrCoSb-based half-Heusler (HH) alloys has been improved tremendously in recent years; however, it remains challenging to find suitable n-type ZrCoSb-based HH alloys due to their high lattice thermal conductivity (κL). In this work, n-type Zr1−xTaxCo1−xNixSb HH alloys were firstly designed by multisite alloying. The evolution of the Raman peak proved that alloy scattering, phonon softening, anharmonicity, entropy-driven disorder, and precipitates had a combined effect on decreasing κL by 46.7% compared to that of pristine ZrCoSb. Subsequently, Hf0.75Zr0.25NiSn0.99Sb0.01 was introduced into Zr0.88Ta0.12Co0.88Ni0.12Sb to further suppress κL. Remarkably, the grain size of the biphasic HH alloys was refined by at least one order of magnitude. A biphasic high-entropy HH alloy with y = 0.2 exhibited the minimum κL of ∼2.44 W/(m·K) at 923 K, reducing by 67.7% compared to that of ZrCoSb. Consequently, (Zr0.88Ta0.12Co0.88Ni0.12Sb)0.9(Hf0.75Zr0.25NiSn0.99Sb0.01)0.1 exhibited the highest TE figure of merit (∼0.38) at 923 K. The cooperation between the entropy and biphasic microstructure resulted in multiscale defects, refined grains, and biphasic interfaces, which maximized the scattering of the multiwavelength phonons in HH alloys. This work provides a new strategy for further reducing the grain size and κL of medium- and high-entropy HH alloys.

Cu2Te-based materials are a type of superionic conductor belonging to the class of phonon-liquid electron-crystal materials and have achieved high ZT values by doping and nanostructuring. However, it is easy to form copper vacancies in Cu2Te which leads to an excessive carrier concentration and then results in a low Seebeck coefficient. Hence, controlling copper ion migration and optimizing carrier concentration is essential to improve the thermoelectric performance of Cu2Te. This paper reports high-performance Cu2TeAg2Te composite with high application value in the low-middle temperature region, which is achieved by fine tuning the carrier concentration using Fe addition and non-stoichiometric Te, as well as controlling the thermal conductivity of composite. A high ZT of ∼1.2 is obtained in AgCu0.97Fe0.03Te0.96 at a low temperature of 573 K. Meanwhile, the phase transition mechanism of Cu2TeAg2Te and its effect on the thermoelectric transport performance are revealed that go beyond nanostructuring and single-doping, which provides a strong theoretical basis for research and performance improvement of thermoelectric materials in this system.

The high lattice thermal conductivity of half-Heuslers (HHs) restricts the further enhancement of their thermoelectric figure-of-merit (ZT). In this study, multiscale scattering centers, such as point defects, dislocations, and nanoprecipitates, are synchronously introduced in a n-type ZrNiSn-based HH matrix through Nb doping and Hf substitution. The lattice thermal conductivity is substantially decreased from 4.55 (for the pristine ZrNiSn) to 1.8 W·m−1·K−1 at 1 123 K via phonon scattering over a broad wavelength range through the adjustment of multiscale defects. This value is close to the theoretically estimated lowest thermal conductivity. The power factor (PF) is enhanced from 3.25 (for the pristine ZrNiSn) to 5.01 mW·m−1·K−2 for Zr0.66Hf0.30Nb0.04NiSn at 1 123 K owing to the donor doping and band regulation via Nb doping and Hf substitution. This can be ascribed to the synergistic interaction between the lowering of the lattice thermal conductivity and retention of the high PF. Consequently, a ZT value of as high as 1.06 is achieved for Zr0.66Hf0.30Nb0.04NiSn at 1 123 K. This work demonstrates that these actions are effective in jointly manipulating the transport of electrons and phonons, thereby improving the thermoelectric performance through defect engineering.

Bioinspired by Nepenthes, lubricant infused surfaces (LIS) have attracted widespread attention in the field of anticorrosion. However, the lubricant coating has some disadvantages such as complex construction processing and easy loss of oil phase in air or dynamic water phase. In this study, oleogel is infused into a lotus leaf inspired super-hydrophobic matrix to form an oleogel infused surface (OIS) for enhancing corrosion resistance of active Mg-Li alloy. For reserving oleogel, firstly, a facile one-step electrodeposition method is used to construct super-hydrophobic surface (SHS) composed by samarium/myristic acid complex micro-nano flower structure onto Mg-Li alloy. The coating exhibits excellent superhydrophobic property at a static contact angle of 160° by applying 30 V electrolysis for 30 min. The protection efficiency of single SHS highly relates with the metal itself. For short period immersion in water phase, SHS can afford protection to Mg-Li alloy. However, the long-term immersion will see the rapid failure of SHS, and the high activity of Mg-Li alloy is one main reason. We assume that SHS cannot be a good choice for protecting Mg-Li alloy. Then, a Nepenthes inspired liquid coating is formed by infusing oleogel into the micro-nano structure by a spin-coating method. The liquid coating performs prominent corrosion resistance with Rct reaching as high as 1.51 × 1010 Ω cm². After the mechanical damage from the external environment, the liquid coating can realize self-repair through thermal assistance, and the liquid coating can still restore Rct up to 1.24 × 1010 Ω cm2 after healing. The corrosion resistance of the liquid coating remains strong by showing Rct as high as 1.14 × 109 Ω cm², even after immersion in representative corrosive 3.5 wt% NaCl solution for 30 d.

In this work, the hybrid micron B4C particles (m-B4Cp) and nano SiC particles (n-SiCp) reinforced 6061Al matrix composites were prepared by powder metallurgy. The synergistic effects of hybrid m-B4Cp and n-SiCp were investigated. The results showed that m-B4Cp were well dispersed in the matrix, while n-SiCp were uniformly distributed inside the grains as well as at the grain boundaries. The coupled addition of n-SiCp and m-B4Cp significantly refined the grain size of matrix from 3.60 μm to 0.91 μm. The synchrotron X-ray computed tomography (SR-CT) revealed that the volume of pores increased with increase of particle content. Compared with the composites reinforced with only one type of particle, the 6061Al composites reinforced with micro and nano dual-size particles possessed higher tensile strength, while maintaining reasonable plasticity. The strengthening contributions to the yield strength improvement of 6010Al matrix composites reinforced with micro and nano dual-size particles are resulted from thermal expansion mismatch strengthening, fine grain strengthening and Orowan strengthening caused by n-SiCp.

Abstract Object Varus-valgus lower alignment is a risk factor for patellofemoral osteoarthritis, but malalignment alone affect not only the tibiofemoral joint but also the patellofemoral joint. The aim of the present study was to analyse the contact area of patellofemoral joint in varus alignment and valgus alignment of healthy subjects using magnetic resonance imaging. Methods Twenty-six healthy subjects with valgus lower limb alignment (Group I, n = 26) and twenty-six volunteers with varus lower limb alignment (Group II, n = 26) was performed. An MRI scan was used to capture and measure the patellofemoral joint articular cartilage contact area at different degrees of knee flexion (20°, 40°,60°) in passive movement. All subjects were categorized on the basis of the global limb alignment and mechanical alignment of the femur and tibia. Varus alignment is hip–knee–ankle angle ≥ 3°; and valgus alignment is hip–knee–ankle angle ≥ − 3°. To obtain medial facet contact area and lateral facet contact area for each slice, the length of each respective line of contact was multiplied by the 5 mm slice thickness. Results The overall joint contact area increased from 168.0 ± 20.5 mm2 at 20° knee flexion to 334.4 ± 30.5 mm2 at 60° knee flexion in group (I) The overall joint contact area increased from 178.0 ± 18.9 mm2 at 20° knee flexion to 328.9 ± 27.2 mm2 at 60° knee flexion in group (II) There was a significant difference in lateral facet contact area between group I and group II at 40° of knee flexion. There was significantly different in medial facet contact area between group I and group II at 20° and 40° of knee flexion. Conclusions Throughout the knee movement, the contact area on the lateral facet of the patellofemoral joint was greater in the valgus group. In the early phase of knee flexion, the contact area of the medial patellofemoral joint was larger in the varus group. Lower alignment is an important factor in patellofemoral joint degeneration.

Abstract Background To investigate the differences in postoperative patellofemoral pressures and patellar tracking during at least three years of follow-up in patients using three prostheses of different designs in total knee arthroplasty (TKA) without patellar resurfacing. Methods: Radiographic investigations The study included 401 patients who had a total of 480 knee prostheses implanted without patellar resurfacing. The prostheses used were Genesis II (external rotation design of femoral prosthesis), Triathlon (design with deep trochlear grooves), and Gemini MK II (deepening of trochlear groove and lateral condylar protrusion that closely follows the anatomical shape). The patients' patellar tracking was assessed by measuring patellar tilt and displacement during postoperative follow-up. Furthermore, postoperative knee function and pain were evaluated through range of motion, Knee Society scores (KSS), and Forgotten Joint Score (FJS) to compare the different groups. Finite element analysis Constructing a finite element model of the knee joint of a normal volunteer after total knee arthroplasty using different prostheses for nonpatellar replacement. The three models' von Mises stress distribution heat map, peak contact pressure, and patellar transverse displacement were compared at 30°, 60°, and 90°, respectively. Results: Radiographic investigations A total of 456 knees of 384 patients were investigated at a 3-year follow-up after TKA without patellar resurfacing. There were no significant differences in patellar tracking between the three groups. Patients with all three prostheses demonstrated favorable clinical outcomes at 3 years postoperatively, with no statistically significant differences in knee scores (91.9 vs 92.3 vs 91.8) or range of motion (127.9° vs 128.5° vs 127.7°) between the groups. However, there was a significant difference between Genesis II and Gemini MK II in the Forgotten Joint Score (59.7 vs 62.4). Patients with persistent postoperative anterior knee pain were present in all three groups (16 vs 12 vs 10), but the incidence was not significantly different. Finite element analysis The von Mises stress distribution heat map showed that during flexion, the patellofemoral stresses were mainly concentrated on the lateral side of the prosthesis side, and the contact site gradually shifted downward with increasing flexion angle. At the same time, the peak contact stress of the patellofemoral joint increased with the gradual increase in the flexion angle. Genesis II, with a wider and shallower trochlear groove, showed greater patellofemoral stresses and lateral patellar displacement after TKA without patellar resurfacing. The Gemini MK II with a deeper trochlear groove and slightly protruding lateral condyle is more in line with anatomical design, with smaller patellofemoral joint pressure and better patellar tracking. Conclusions In TKA without patellar resurfacing, a prosthesis with a deeper trochlear groove, a slightly higher lateral femoral condyle, and a more anatomically designed knee that better matches the patellar morphology should be a better choice.

Particle engulfment plays a vital role in the application of particulate reinforced metal matrix composites fabricated by ingot metallurgy. During solidification, particles are nevertheless pushed by an advancing front. As a model system, TiB2p/Al composites were used to investigate the particle engulfment facilitated by acoustic cavitation. The implosion of bubbles drives the particles plunging towards the solid/liquid interface, which increases the engulfment probability. The secondary dendrite arms are refined from 271.2 μm to 98.0 μm as a result of the forced movements of TiB2 particles. Owing to the particle engulfment and dendrite refinement, the composite with ultrasound vibration treatment shows a more rapid work-hardening rate and higher strength.

Abstract Purpose To investigate the differences of patellofemoral joint pressure and contact area between the process of stair ascent and stair descent. Methods The finite element models of 9 volunteers without disorders of knee (9 males) to estimate patellar cartilage pressure during the stair ascent and the stair descent. Simulations took into account cartilage morphology from magnetic resonance imaging, joint posture from weight-bearing magnetic resonance imaging, and ligament model. The three-dimension models of the patella, femur and tibia were developed with the medical image processing software, Mimics 11.1. The ligament was established by truss element of the non-linear FE solver. The equivalent gravity direction (-z direction) load was applied to the whole end of femur (femoral head) according to the body weight of the volunteers, and the force of patella was observed. A paired-samples t-test or Wilcoxon rank sum test to make comparisons between stair ascent and stair descent. Statistical analyses were performed using SPSS 22.0 using a P value of 0.05 to indicate significance. Results During the stair descent (knee flexion at 30°), the contact pressure of the patella was 2.59 ± 0.06Mpa. The contact pressure of femoral trochlea cartilage was 2.57 ± 0.06Mpa. During the stair ascent (knee flexion at 60°), the contact pressure with patellar cartilage was 2.82 ± 0.08Mpa. The contact pressure of the femoral trochlea cartilage was 3.03 ± 0.11Mpa. The contact area between patellar cartilage and femoral trochlea cartilage was 249.27 ± 1.35mm2 during the stair descent, which was less than 434.32 ± 1.70mm2 during the stair ascent. The area of high pressure was located in the lateral area of patella during stair descent and the area of high pressure was scattered during stair ascent. Conclusion There are small change in the cartilage contact pressure between stair ascent and stair descent, indicating that the joint adjusts the contact pressure by increasing the contact area.

Abstract Purpose Patellar height is a risk factor for patellar instability, correlated with the tibia length/femur length (T/F) ratio. This study aimed to explore the changes in the T/F ratio in patients with patella instability and the potential correlation with the morphology of the patellofemoral joint and extensor moment arm. Method A retrospective analysis was performed to assess the ratio of lower limb length morphological characteristics of the patellofemoral by full weight-bearing long-leg standing radiographs, magnetic resonance imaging, and computed tomography in 75 patients with patellar instability and 75 participants from a randomly selected control group from January 2020 to September 2021. A total of eight parts were measured, including mechanical tibia length/femur length (mT/F) ratio, anatomical tibia length/femur length (aT/F) ratio, hip–knee–ankle angle, femoral neck-shaft angle, femoral valgus cut angle, patellar height, Dejour classification, sulcus angle, trochlear angle, medial trochlear inclination, lateral trochlear inclination, patella tilt angle and patellar tendon moment arm to evaluate the difference of morphology between patient group and control groups. Results The mT/F (0.840 ± 0.031 vs. 0.812 ± 0.026, p

The design of high-performance overhead aluminum wires is challenging, due to the intrinsic trade-off of strength-ductility and strength-electrical conductivity (EC). The in-situ halide salt reactions were used to introduce dual-size TiB2 particles into 6201 alloy to obtain out-bound mechanical properties with slight sacrifice of EC. With this strategy, the ultimate tensile strength, elongation after fracture and EC of the 4 wt%TiB2/6201Al composite are 360.9 MPa, 8.27% and 53.5% IACS, respectively, and these properties of the reference 6201 alloy are 325.0 MPa, 7.8% and 56.06% IACS. In the as-cast state, the majority of sub-micron TiB2 particles are segregated at the grain boundaries (termed as GBPs), forming a network pattern. The network is stretched along the rolling direction (RD) during deformation, and the orientation of GBPs is also rearranged from chaotic to a position with c axis nearly normal to the RD. In addition, semi-coherent particle/matrix interface is formed, which play a crucial role in strengthening the matrix. To optimize the EC, neutralization by adding Al–3B master alloy was performed, thus successfully eliminating the detrimental Al3Ti phase and precipitating excessive solute Ti atoms. The results show that not only the EC, but also the strength and ductility maximize at a composition around B:Ti = 2.0.

Effect of micropore defects on the tensile stress–strain response and damage behavior in a B4Cp/6061Al composite was investigated via establishing an actual three-dimensional (3D) finite element model based on a representative volume element (RVE). The incorporated 3D microstructure was achieved by synchrotron radiation X-ray computed microtomography (SR-μCT). RVE-I consists of B4C particles, matrix, and micropore defects, while the micropore defects are artificially filled by matrix in the RVE-II. The simulation results demonstrate that compared with the RVE-II, the presence of micropore defects in the RVE-I leads to a lower tensile property which is close to the experimental result. Matrix damage associated with the micropore defects that are composed of voids from cracking particles and voids near particle/matrix interfaces is revealed by analyzing the distribution of strain and stress. Furthermore, different damage processes observed in two RVEs, indicating that the micropore defects play a significant role in determining the crack propagation path. This work offers a reference for studying the mechanical behavior of particle-reinforced aluminum matrix composites from a novel perspective.

Introduction: Trochlear dysplasia is a commonly encountered lower extremity deformity in humans. However, the molecular mechanism of cartilage degeneration in trochlear dysplasia is unclear thus far. Objectives: The PI3K/AKT signaling pathway is known to be important for regulating the pathophysiology of cartilage degeneration. The aim of this study was to investigate the relationship of the PI3K/AKT signaling pathway with trochlear dysplasia cartilage degeneration. Methods: In total, 120 female Sprague-Dawley rats (4 weeks of age) were randomly separated into control and experimental groups. Distal femurs were isolated from the experimental group at 4, 8, and 12 weeks after surgery; they were isolated from the control group at the same time points. Micro-computed tomography and histological examination were performed to investigate trochlear anatomy and changes in trochlear cartilage. Subsequently, expression patterns of PI3K/AKT, TGFβ1, and ADAMTS-4 in cartilage were investigated by immunohistochemistry and quantitative polymerase chain reaction. Results: In the experimental group, the trochlear dysplasia model was successfully established at 8 weeks after surgery. Moreover, cartilage degeneration was observed beginning at 8 weeks after surgery, with higher protein and mRNA expression levels of PI3K/AKT, TGFβ1, and ADAMTS-4, relative to the control group. Conclusion: Patellar instability might lead to trochlear dysplasia in growing rats. Moreover, trochlear dysplasia may cause patellofemoral osteoarthritis; cartilage degeneration in trochlear dysplasia might be associated with activation of the PI3K/AKT signaling pathway. These results provide insights regarding the high incidence of osteoarthritis in patients with trochlear dysplasia. However, more research is needed to clarify the underlying mechanisms.

Abstract Background Poor osseointegration is the key reason for implant failure after arthroplasty,whether under osteoporotic or normal bone conditions. To date, osseointegration remains a major challenge. Recent studies have shown that deferoxamine (DFO) can accelerate osteogenesis by activating the hypoxia signaling pathway. The purpose of this study was to test the following hypothesis: after knee replacement, intra-articular injection of DFO will promote osteogenesis and osseointegration with a 3D printed titanium prosthesis in the bones of osteoporotic rats. Materials and methods Ninety female Sprague–Dawley rats were used for the experiment. Ten rats were used to confirm the successful establishment of the osteoporosis model: five rats in the sham operation group and five rats in the ovariectomy group. After ovariectomy and knee arthroplasty were performed, the remaining 80 rats were randomly divided into DFO and control groups (n = 40 per group). The two groups were treated by intraarticular injection of DFO and saline respectively. After 2 weeks, polymerase chain reaction (PCR) and immunohistochemistry were used to evaluate the levels of HIF-1a, VEGF, and CD31. HIF-1a and VEGF have been shown to promote angiogenesis and bone regeneration, and CD31 is an important marker of angiogenesis. After 12 weeks, the specimens were examined by micro-computed tomography (micro-CT), biomechanics, and histopathology to evaluate osteogenesis and osseointegration. Results The results of PCR showed that the mRNA levels of VEGF and CD31 in the DFO group were significantly higher than those in the control group. The immunohistochemistry results indicated that positive cell expression of HIF-1a, VEGF, and CD31 in the DFO group was also higher. Compared with the control group, the micro-CT parameters of BMD, BV/TV, TB. N, and TB. Th were significantly higher. The maximal pull-out force and the bone-to-implant contact value were also higher. Conclusions The local administration of DFO, which is used to activate the HIF-1a signaling pathway, can promote osteogenesis and osseointegration with a prosthesis in osteoporotic bone.

ObjectivesMedial patellofemoral ligament (MPFL) reconstruction is an important surgical therapy for recurrent patellar dislocation. However, few studies have focused on exercise therapy after MPFL reconstruction. Therefore, the first purpose was to compare the active and traditional postoperative exercise therapies on the recovery of knee joint function and reduction of muscle atrophy after MPFL reconstruction, and the second purpose was to compare the active and traditional postoperative exercise therapies on the patellar stability after MPFL reconstruction.MethodsThe cases of 31 patients with recurrent patellar dislocation treated with patella double semi-tunnel anatomical MPFL reconstruction from February 2016 and February 2019 were retrospectively reviewed. The clinical outcomes, including the patellar tilt angle (PTA), lateral patellofemoral angle (LPFA), thigh circumference reduction, Kujala score, and Lysholm score, were compared between two groups (i.e., active exercise and traditional exercise groups) preoperatively, 3 months postoperatively, 6 months postoperatively, 12 months postoperatively, and 24 months postoperatively.ResultsThe Kujala score was significantly higher in the active exercise group than traditional exercise group 3 months postoperatively (80.06 vs. 74.80, P 0.05) or LPFA postoperatively (P > 0.05).ConclusionsOur results suggested that active exercise therapy might benefit the early recovery of knee joint function and reduction of muscle atrophy in patients with recurrent patellar dislocation after MPFL reconstruction.

CuNiSi alloys are widely used for lead frames and connectors due to the combination of high strength and high electrical conductivity. In this work, the microstructures, properties and precipitation behaviors of cryo-rolled CuNiSi alloys with different Cr additions were investigated. The results show that the microstructures of cryo-rolled CuNiSi alloys are mainly composed of nano-sized deformation twins. During aging, discontinuous precipitation gradually takes the place of continuous precipitation with the onset of recrystallization. The addition of chromium reacts to form Cr3Si particles and facilitates the formation of lamellar structures in the cryo-rolled states of CuNiSi alloys. Moreover, both the recrystallization and the discontinuous precipitation of cryo-rolled CuNiSi alloys are hindered by the addition of Cr elements. As a result, the mechanical strength of cryo-rolled CuNiSi alloys after aging can be maintained. The best combination of properties obtained in the CuNiSi-0.15Cr alloy is 761 MPa, 6.1% and 48.4% IACS in ultimate strength, elongation and electrical conductivity, respectively.

Abstract Background Patellar instability (PI) often increases the possibility of lateral patellar dislocation and early osteoarthritis. The molecular mechanism of early articular cartilage degeneration during patellofemoral osteoarthritis (PFOA) still requires further investigation. However, it is known that the NF-κB signaling pathway plays an important role in articular cartilage degeneration. The aim of this study was to investigate the relationship between the NF-κB signaling pathway and patellofemoral joint cartilage degeneration. Methods We established a rat model of PI-induced PFOA. Female 4-week-old Sprague-Dawley rats (n = 120) were randomly divided into two groups: the PI (n = 60) and control group (n = 60). The distal femurs of the PI and control group were isolated and compared 4, 8, and 12 weeks after surgery. The morphological structure of the trochlear cartilage and subchondral bone were evaluated by micro-computed tomography and histology. The expression of NF-κB, matrix metalloproteinase (MMP)-13, collagen X, and TNF-ɑ were evaluated by immunohistochemistry and quantitative polymerase chain reaction. Results In the PI group, subchondral bone loss and cartilage degeneration were found 4 weeks after surgery. Compared with the control group, the protein and mRNA expression of NF-κB and TNF-ɑ were significantly increased 4, 8, and 12 weeks after surgery in the PI group. In addition, the markers of cartilage degeneration MMP-13 and collagen X were more highly expressed in the PI group compared with the control group at different time points after surgery. Conclusions This study has demonstrated that early patellofemoral joint cartilage degeneration can be caused by PI in growing rats, accompanied by significant subchondral bone loss and cartilage degeneration. In addition, the degeneration of articular cartilage may be associated with the activation of the NF-κB signaling pathway and can deteriorate with time as a result of PI.

Increased femoral anteversion (FA) has been recently demonstrated as one risk factor for recurrent patellar dislocation (RPD). However, it has been still unclear whether the increase of FA can result in patellar dislocation, and subsequent morphological and trabecular microarchitectural changes in the trochlea has not been investigated. Forty knees from 20 rabbits at 3 months of age were included. The right knees underwent surgery with internal rotation of distal femur to increase FA, with the left knees acting as internal controls. The surgical knees were called operated group, and non-operated knees were control group. Micro-CT scans for distal femur were acquired after 4 months of surgery. In the operated group, a boss located proximal to the entrance of the groove was formed. The central trochlear height was significantly greater, sulcus angle was significantly greater, both lateral and medial trochlear slope were significantly lower, and boss height was significantly greater in comparison to the control group. Regarding the microarchitectural changes, the trabecular thickness were increased by 67.5% at the groove, 33.0% and 29.5%, at the medial and lateral femoral condyle, and trabecular number were decreased by 37.8% and 26.5% at the groove and medial femoral condyle. This study provided a novel animal model of trochlea dysplasia by femoral rotational osteotomy and increased FA. These changes were associated with the load redistribution in the patellofemoral joint after the increase of FA. Keywords: Patellar dislocation, Trochlea dysplasia, Femoral anteversion, Boss, Femoral osteotomy

The microstructure and tensile properties of the as-cast and as-rolled Mg–4.5Sn–5Zn alloys by adding various Sc content were investigated. Improvement of the tensile properties in as-cast Sc-containing alloys is attributed to the grain refinement and modification of secondary phase morphology. Three types of precipitates, namely spherical Mg2Sn, rod-like MgZn and Sc-rich phases were dispersed in the matrix of the Sc added Mg–4.5Sn–5Zn alloys after hot rolling deformation. In addition, weakening and deflecting of the basal texture in as-rolled alloys were found and were attributed to Sc addition. Further increasing the Sc addition rate to 0.4 wt.%, however, resulted in the clustering of the Sc-rich phases and was found to reduce the tensile properties of the alloy, especially the elongation. The as-rolled Mg–4.5Sn–5Zn–0.3Sc alloy exhibits an optimum combination of tensile properties. The ultimate tensile strength, yield strength and elongation are 293.0 MPa, 164.2Mpa and 21.5%, respectively, and the elongation is about 68% higher than that of Sc-free alloy. Keywords: Magnesium alloys, Scandium, Microstructure, Mechanical properties

Objective: The purpose of this study was to evaluate the diagnostic value of the patellar tendon wavy (PTW) sign for an anterior cruciate ligament (ACL) tear on MRI. Methods: One hundred MRI scans were prospectively analyzed, with 50 patients with an ACL tear underwent an ACL reconstruction (group 1) and 50 patients with knee complaints other than ACL tear (group 2). The PTW sign was confirmed on the sagittal MRI. In addition, the patellar tendon length, tibial-femoral angle and tibial anterior translation (TAT) were compared between the groups. Results: The PTW sign was present in 41/50 (82%) MRI scans in group 1 and 10/50 (20%) in group 2, with significant difference between two groups (p = 0.000). Significant differences were also found, in medial TAT (6.29 ± 3.25 mm versus 3.12 ± 2.85 mm) and in lateral TAT (7.62 ± 3.85 mm versus 1.58 ± 3.93 mm) between two groups (both p = 0.000). Comparison of MRI with and without PTW sign, ACL injury was found to be of significant difference with 41/51 (80.4%) versus 9/49 (18.4%) (p = 0.000), and both medial and lateral TAT were with significant differences, 5.39 ± 3.90 mm versus 3.99 ± 2.71 mm (p = 0.039) and 7.67 ± 3.77 mm versus 1.40 ± 3.81 mm (p = 0.000), respectively. The sensitivity and specificity of PTW sign were 82% and 80%. The positive and negative predictive value were 80.4% and 81.6%. The diagnosis accuracy was 81%. Conclusion: The PTW sign is a useful secondary MRI sign to establish the diagnosis of an ACL tear. It may be associated with the TAT secondary to an ACL tear. Level of evidence: Level III, diagnostic study. Keywords: Anterior cruciate ligament, MRI diagnosis, Secondary sign, Patellar tendon wavy sign, Tibial anterior translation

In this paper, the microstructures and corrosion behaviors of as-cast Mg−5Sn−xGa alloys with varying Ga content (x = 0, 0.5, 1, 2, 3 wt %) were investigated. The results indicated that Ga could not only adequately refine the grain structure of the alloys, but could also improve the corrosion resistance. The microstructures of all alloys exhibited typical dendritic morphology. No Ga-rich secondary phases were detected when 0.5 wt % Ga was added, while only the morphology of Mg2Sn phase was changed. However, when the addition rate of Ga exceeded 0.5 wt %, an Mg5Ga2 intermetallic compound started to form from the interdendritic region. The volume fraction of Mg5Ga2 monotonically increased with the increasing Ga addition level. Although Mg5Ga2 phase was cathode phase, its pitting sensitivity was weaker than Mg2Sn. In addition, the standard potential of Ga (−0.55 V) was lower than that of Sn (−0.14 V), which relieved the driving force of the secondary phases for the micro-galvanic corrosion. An optimized composition of 3 wt % Ga was concluded based on the immersion tests and polarization measurements, which recorded the best corrosion resistance.

Synchrotron radiation computed micro-tomography (SR-μCT) is a non-destructive characterization method in materials science, which provides the quantitative reconstruction of a three-dimension (3D) volume image with spatial resolution of sub-micrometer level. The recent progress in brilliance and flux of synchrotron radiation source has enabled the fast investigation of the inner microstructure of metal matrix composites without complex sample preparation. The 3D reconstruction can quantitatively describe the phase distribution as well as voids/cracks formation and propagation in structural metals, which provides a powerful tool to investigate the deformation and fracture processes. Here, we present an overview of recent work using SR-μCT, on the applications in structural metals.