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Background Popular protests have broken out worldwide, particularly in the last few years. In 2019, numerous demonstrations against an extradition bill occurred in Hong Kong until pandemic restrictions were imposed. The policing response relied heavily on methods such as batons, tear gas and rubber bullets. Given the relevance for other geographical contexts, the current study investigated the mental health impacts on protest participants and spillover to community members. Methods Surveys were disseminated on social media in August and October 2019 to collect demographics, political views, protest participation, exposure to (protest-related) potentially traumatic events (PTEs) and mental health symptoms. A latent class analysis (LCA) was conducted using demographic data and inter-class differences in PTEs and mental health symptoms were examined. Results There were 37,541 (59.8% female) and 40,703 (50.0% female) responses in August and October. Respondents, even those with low participation, reported significant levels of depression, anxiety, and symptoms of traumatic stress (STS). The LCA suggested a 5-class solution (youth, allies, supporters, sympathizers, and frontliners). Mental health symptoms and PTEs varied with class membership, with 50.8% of frontliners reporting severe STS. Limitations The non-random sampling and self-reported measures may over-estimate the prevalence of mental distress in the wider population. Conclusions Large numbers of pro-democracy supporters in Hong Kong reported high rates of depression, anxiety and STS during mass protests. Younger and more heavily involved respondents faced the highest mental health risks, however elevated rates were also observed for respondents with low participation.

Cyclic deformation behavior of friction-stir-welded dissimilar AA2024-T351 to AA7075-T65 aluminum alloy joints was evaluated via stepwise tests at different strain rates, along with transmission electron microscopy examinations to characterize the precipitates required to assess internal stresses. Electron backscatter diffraction was employed to observe the inhomogeneous microstructures of the FSWed joints. Strain localization appeared in the heat affected zone (HAZ) of AA2024 side. After cyclic deformation of 500 cycles at a total strain amplitude of 0.5 %, the strength of the dissimilar joints resumed basically to that of AA2024 base material. And the AA2024 HAZ was obviously hardened, which should be attributed to the introduced dislocations during cyclic deformation process. Cyclic hardening capacity of the joints increased with decreasing strain rate.

Synergetic double-sided probeless friction stir spot welding is a novel process proposed in this study, which is used to solve the contradiction between the improvement of metallurgical bonding and deterioration of hook defect. The effect of the coordinated movement of the tools on the joint formation was evaluated based on the coupled Eulerian-Lagrangian technique. By flexibly adjusting the welding parameters on both sides, the mechanical interlock caused by hook defect could be effectively regulated while significantly improving the metallurgical bonding, due to the enhancement of thermo-mechanical cycle along the thickness direction. According to the microstructure analysis, the interfacial evolution was ascribed to the combined effects of plastic deformation, material flow, atom diffusion, and recrystallization, as well as local abrasion. In addition, the microhardness profile exhibited a uniform distribution. Based on the above characteristics, the technology is expected to obtain higher strength joints, which will promote its applications in the manufacture fields.

Eight-millimeter-thick high-strength AA2219 aluminum alloy plates were successfully welded by variable polarity tungsten inert gas welding, and the effect of cold spraying (CS) process on the residual stress, microstructure and mechanical properties of the welded joints were investigated. The CS experiment was performed under different driving gas temperatures and pressures and with different powder types. The microstructure of the as-welded joints and as-coated joints was analyzed by optical microscopy and scanning electron microscopy, while the residual stress was measured by the blind-hole-drilling method. The results show that the CS process could significantly modify and re-distribute the residual stress of the welded joints. The maximum residual tensile stress of the welded joint has been significantly reduced by 111.9% and distributed more uniformly compared to the as-welded state. With the increase in gas temperature and/or pressure in CS, the residual tensile stress of joints was reduced, and even some compressive stress appeared. Among the powders of Cu, Al, and Ni, Cu particles have the best-improving effect. In addition, double-sided spraying treatment can reduce the residual tensile stress of both sides more effectively. Besides, the grain size of the joint surface after CS was refined.

A 3D transient computational thermal model is developed to investigate the heat transfer effects arising during friction stir welding (FSW) in dissimilar alloys with a T-joint. Specifically, a dual-heat-source-based mathematic model is derived on the basis of theories of classical as well as adhesive friction while using the actual fixture geometry adopted in the corresponding FSW experiment. A sliding mesh method is used to represent the positions of the dynamic heat source to capture the complex motion of the rotational smooth pin, and the FSW-T process of the stiffener with the corresponding thermal physical properties being obtained by JMAT software and simulated by APDL programming codes in ANSYS. The actual FSW experiment is carried out on alloy plates with a T-joint whose temperature histories were recorded at by the embedded thermocouples (Ps) placed at specified positions. The transient temperature profiles predicted are found to be in good agreement with those monitored during FSW-T. This has confirmed the validity and the reliability of the thermal model, thus indicating that it could be used to reflect the heat transfer process of FSW-T rather than resorting to an actual test.

Barley stripe mosaic virus (BSMV)-based virus induced gene silencing (VIGS) is an effective strategy for rapid determination of functional genes in wheat plants. ERECTA genes are reported to regulate stomatal pattern of plants, and manipulation of TaERECTA (a homo-logue of ERECTA in bread wheat) is a potential route for investigating stomatal development. Here, the leucine-rich repeat domains (LRRs) and transmembrane domains of TaERECTA were selected to gain BSMV:ER-LR and BSMV:ER-TM constructs, respectively, targeting TaERECTA for silencing in wheat cultivars ‘Bobwhite’ and ‘Cadenza’, to identify the function of TaERECTA on stomatal patterns. The results showed that reduced expression of TaERECTA caused an increased stomatal and epidermal cell density by average 13.5% and 3.3%, respectively, due to the significantly reduced size of leaf epidermal and stomatal cells, and this led to an increase in stomatal conductance. These suggest that modulation of TaERECTA offers further opportunities in stomatal engineering for the adaptation of photosynthesis in wheat.

The microstructural evolution across the friction-stir-welded dissimilar AA5083-H112 to AA2024-T351 aluminum alloy joints was characterized via electron backscatter diffraction (EBSD), aiming to identify the effect of inhomogeneous microstructures on the tensile properties and cyclic deformation behavior along with the influence of loading history. Results show that the top region of the stir zone (SZ) mainly consisted of AA2024 which was initially positioned on the retreating side during welding. On the AA5083 side, the lowest density of the geometrically-necessary dislocations (GNDs) assessed from the local misorientations of 0°–2° appeared in the SZ, while it occurred in the heat-affected zone (HAZ) of the AA2024 side. The fractions of recrystallized grains in the AA5083 SZ and AA2024 SZ were ~73% and ~34%, respectively. Strain localization and the resultant failure occurred in the lowest hardness zone of the AA5083 side. The extent of cyclic hardening increased as the stress amplitude increased. Both plastic strain amplitude and plastic strain energy density decreased with increasing number of cycles at higher total strain amplitudes. In the stepwise cyclic deformation tests in the form of ascending-descending loading, the prior cyclic deformation process tended to generate more stabilized structure and performance.

The objective of this study was to identify the effect of base metal (BM) locations on the corrosion behavior of friction stir welded dissimilar 2024-T351 to 7075-T651 aluminum alloys joints in an EXCO solution. Electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and high resolution TEM (HRTEM) were conducted to characterize the microstructure evolution of the BMs and stir zones (SZs). Scanning electron microscopy (SEM) was employed to observe the appearance of these corroded zones. Results reveal that the corrosion resistance of SZs is similar to that of the BM positioning in the retreating side (RS), and intergranular corrosion (IGC) is prevailing. The fine recrystallized grains in SZs exhibit more drastic IGC than that of BMs. The discontinuously distributed grain boundary precipitates and precipitate-free zones in the SZ of 2024 reduce the IGC damage of SZ.

Al-Cu alloy was friction stir welded (FSWed) with Al-Zn and Al-Mg alloys, respectively. Tensile properties, strain hardening behavior and fracture mechanisms of the FSWed dissimilar joints were evaluated. Results reveal that the strain-hardening rate of Al-Cu/Al-Zn dissimilar joint is higher than that of base metals due to the presence of finer recrystallized grains in the stir zone, while the strain-hardening rate of Al-Cu/Al-Mg dissimilar joint lies in-between those of base metals. The hardening level of Al-Cu/Al-Zn joint after tensile deformation, defined as HVf/HVw (a ratio of microhardness of fractured joints to that of as-welded joints), exhibits an ‘M’ shape across the welded joint.

A coupled Eulerian-Lagrangian (CEL) model was developed to investigate the formation mechanism of band pattern (BP) during bobbin tool friction stir welding (BTFSW) process. The Johnson-Cook constitutive model which combines the strain rate and temperature effects in the material flow stress was used. The workpiece was modeled by the Eulerian formulation, while the tool was characterized by the Lagrangian formulation. The numerical analysis results agree well with experimental observations. The band structures with various sizes were discovered in the BP zone. Both the experimental and numerical analysis results indicate the BP zone forms on the advancing side of the joint. This is because the converged material flow is produced by both shoulders while being driven by the probe. The peak temperature, along the thickness of the BP zone, increased at the beginning followed by a decrease further away from the upper surface. The peak temperature obtained near the lower surface is slightly higher than that near the upper surface.

Sheets of AA2198 alloy with various surface conditions were welded with probeless friction stir spot welding (P-FSSW). Results show that the oxide layer on the original lap-weld surface pro...

In this study, two post-spray treatments, i.e. high-temperature vacuum annealing (HTVA) and friction stir processing (FSP), were employed to modify the cold-sprayed (CS) Ni-Ti coatings, obtained from a mechanically blended powder. The phase transformation occurred at different HTVA temperatures, but with the formation of pores due to the Kirkendall effect. FSP proved to provide a new opportunity for the formation of intermetallic phases in the CSed Ni-Ti coating. A comparison of the microstructures, microhardness and tribological behaviors between the CSed and FSPed coatings, reveals that the microstructure of the modified Ni-Ti coating exhibits a mechanically alloyed layer with the in-situ synthesized Ni-Ti intermetallics, and no obvious defects are found. The microhardness of the improved layer is increased to 1003.5 ± 65.9 HV0.1, which is about 4.5 times compared to the CSed coating (222.5 ± 6.6 HV0.1). In addition, the mechanically alloyed layer by FSP contains multiplicate Ni-Ti intermetallic compounds, exhibiting better wear resistance than that of the CSed coating, thus proving the effectiveness of FSP on the microstructural modification and properties improvement for the CSed metal-metal composite coatings.

The tensile properties of friction stir welded AA2024-T3 joints at the rotation speed range of 600–900 rpm and a constant welding speed of 200 mm/min were summarized, finding that the optimized rotation speed is 600 rpm which yield a maximum tensile strength of 420 MPa. Subsequently, an aluminum coating was deposited on the optimized joint surface by cold spraying (CS). The microstructural evolution in the layer near the surface of the coated joint was investigated by a combination of transmission electron microscopy, electron back-scattered diffraction and differential scanning calorimetry. The results show that the CSed joint exhibits significantly enhanced tensile strength, microhardness and fatigue life. This improvement is attributed to refined grains with a higher number of Guinier-Preston-Bagaryatsky (GPB) zones, finer and more S phases, and lower residual stresses due to the heat flow and shot peening effects by the CS on the layer near the surface. CS is shown to be an additional technique to enhance the mechanical properties of FSWed joints whilst providing corrosion protection for them.

The aim of this study was to analyze the microstructural changes of two dissimilar Ti-6Al-4V/Ti17 and Ti-6Al-4V/BT9 joints welded via electron beam welding (EBW), and establish the relationship between microstructure and properties. The results showed that the occurrence of phase transformation was mainly dependent on the peak heating temperature during EBW, and despite the same welding parameters the microstructures of two dissimilar joints were different except in the heat-affected zone (HAZ) on the Ti-6Al-4V side. Both dissimilar joints exhibited a higher strength compared with Ti-6Al-4V base metal (BM), and the strength of Ti-6Al-4V/Ti17 joint was slightly higher than that of Ti-6Al-4V/BT9 joint due to the presence of finer martensite. Fatigue life of dissimilar joints was almost the same as that of Ti-6Al-4V BM within the experimental scatter. Fatigue failure of both dissimilar joints occurred in the HAZ, and fatigue crack basically initiated from the specimen surface.

The microstructure and texture evolution during linear friction welding (LFW) of pure titanium joints were investigated with scanning electron microscope, transmission electron microscope and electron back-scattering diffraction. The unique combination of high temperatures and strain rates during LFW causes limited continuous dynamic recrystallization in the weld center zone (WCZ), leading to a mixed microstructure of refined grains with severe elongated grains. Under the combined effect of axial pressure and shear stress, the texture across the weld line changes significantly. In parent metal, the c-axis of grains is parallel to the RD-TD plane and has an angle of 45° to TD, then in the thermomechanically affected zone the c-axis turns parallel to the welding interface and along the TD, finally in WCZ the c-axis turns to the ND and the P1 101¯0112¯0 texture forms. Compared with the ideal hcp shear textures, the present results show that material flow during LFW of titanium indeed arises from the simple-shear deformation and is governed by prismatic slip rather than twinning. The strong texture in LFWed joints is the cause of the anisotropic mechanical properties. Keywords: Linear friction welding, Titanium, Microstructure, Texture, Anisotropic mechanical properties

As one of the important Cu alloys, brass has been implanted in many fields of architecture or fabrication industry. Muntz (Cu60Zn40) brass alloy was used to manufacture the brass coatings in this study due to showing the best corrosion resistance. Two different spray methods i.e. vacuum plasma spray (VPS) and cold gas dynamic spray (CGDS), were chosen to perform the synthesis of brass coatings aiming to avoid oxidation. Upon utilization of VPS and CGDS techniques, spray process is crucial to the microstructures, phase transformation, mechanical property, and wear and corrosion properties of Muntz alloy coatings. Here results show that no oxidation was characterized in both two processes. Nevertheless, a vaporization of 19.32 wt% Zn occurred during VPS, which would lead to the significant differences in grain size, misorientation distribution, texture and phase composition of VPSed coating from those of CGDSed coating. The CGDSed coating exhibited excellent performances due to a preservation of chemical composition of original feedstock. For example, it yielded a hardness value of 211.8 ± 9.8 HV0.3, which was nearly two times higher than that of VPSed coating (119.3 ± 11.6 HV0.3). It was also shown that a significant wear rate reduction ((1.3 ± 0.018) × 10−5 v.s. (2.36 ± 0.39) × 10−4 mm3/mN) and a corrosion resistance enhancement.

For an example of brass material-Muntz alloy, the present work compared the microstructures and properties, such as, ceramic deposition efficiency, surface morphology, phase, microhardness, electrochemical behaviour and thermal property, of two kinds of brass-based composite coatings reinforced with SiC and Al2O3 by cold-spray additive-manufacturing. A potential application in repairing the Muntz component was implemented, and the restoration quality was assessed by the interfacial microstructure and tribological performance. In particular, cold spray was proved to be a suitable method of additive manufacturing the easily oxidized and vaporized material and repairing its component.

Numerical simulations have been widely used to study particles impacting behavior in cold spraying. Among the used simulation methods, the Eulerian frame becomes increasingly attractive for its absence of mesh distortion which happens in the Lagrangian frame. It has been proved that particle deformation behaviors upon impacting calculated by the Eulerian method are well comparable to the experimental observations. In this review article, the literature on modeling particle impacting by the Eulerian method was summarized. In the second part, the Eulerian method was detailedly introduced. In the third part, the particle/substrate impacting behavior, and its influencing factors, i.e., mesh resolution, particle impacting velocity, preheating (particle or/and substrate) and oxide film, were summarized. Additionally, the prediction of critical velocity and residual stresses by using the Eulerian method was also discussed in detail. Finally, the current issues, problems and prospects existing in the Eulerian simulations of particle impacting were explored.

The welded joints are often subjected to cyclic stresses and high-strain-rate deformation resulting in worrisome fatigue failure. Therefore, it is necessary to evaluate the fatigue resistance and cyclic deformation characteristics of these weldments. Ti–6Al–4V–0.3Fe–0.1C–0.05N–0.015H–0.2O (TC4) titanium alloy joints were produced via linear friction welding and a sound joint was obtained. It was observed that fine subgrains formed in the weld zone where the hardness became higher. The strain ratio had a strong effect on the cyclic deformation characteristics of the joint, with hysteresis loops being different at different strain ratios. However, the difference of fatigue life of the joint was small with varying strain ratios. The stress amplitude of linear friction welded TC4 joint showed essentially cyclic softening until failure at all strain ratios. Fatigue cracks initiated from the near-surface of base metal and propagated by the formation of fatigue striations together with secondary cracks.

Linear friction welded joints of Ti2AlNb-based alloy were subjected to different solution and aging treatments. Relationships among solution and aging conditions, microstructural evolution and mechanical properties were investigated. The results indicate that the microstructures are very sensitive to solution conditions. In weld zone, the lath O precipitates at the grain boundaries when the joint is solution treated in O+B2 phase region, while the formation of lath α2 phase occurs in α2+B2+O phase region. In thermo-mechanically affected zone (TMAZ), aggregation of O phase and rim O phase resulted from further decomposition of α2 phase can be found during solution treatment. And after aging treatment, both weld zone and TMAZ are comprised of secondary acicular O phase within B2 grains. Solution and aging treatments have significantly enhanced the microhardness of weld zone due to the precipitation hardening of O phase and refined grain strengthening. After aging treatment, the tensile strength of the joints is further improved because of precipitation of secondary O phase, whereas, elongation is reduced due to the suppression of the hard deformation modes in fine acicular microstructures.

A 30–40 μm thick oxide layer was prefabricated on the top, butt or bottom surfaces of AA2024 sheets by micro-arc oxidation, which were then friction stir welded. Sheets without oxide layer were also welded with blowing oxygen along the weldline during welding for comparison purposes. Results reveal that the tensile properties depend on the amount and distribution of the residual oxide impurities in the joints. The oxide layer on the butt surface leads to continuously distributed oxide impurities in the shoulder-affected zone near the advancing side, and a 159 MPa maximum degradation in tensile strength was noticed. Moreover, the oxygen blowing during welding has a little influence on the joint tensile strength and no oxide was detected in the joint.

AA2198–T851 sheets were welded by bobbin tool friction stir welding using a rotational speed of 800 rpm and welding speed of 42 mm min−1. The microstructure and precipitates within the joint were characterised by transmission electron microscopy. The global and local mechanical behaviour was determined using a digital image correlation system. Specific attention was given to the relationship between the local microstructure and properties across the joint, which govern the global strength and ductility of the welds. A lower global elongation of the joint is caused by the premature strain localisation in the softened zone.

In this study, pinless friction stir spot welding of 1.8 mm thick 2198-T8 aluminium–lithium alloy plates was carried out. The change of the angle between the nugget edge and the surface, and the relationship between this angle and joint mechanical property were analysed. The results show that the angle increases rapidly initially and then approaches 45°, which is due to the extrusion of nugget material and its flow along the surrounding ‘cold’ metal during welding. The tensile strength is determined by the nugget edge angle and hook defect. Tensile loads reach a higher value when the nugget edge angle approaches 45° but have a slight decrease with the hook angle changing from obtuse to acute. The maximum tensile/shear strength could be 8.57 kN at the rotation speed of 1500 rev min− 1 and the dwell time of 12 s.

As the literature reported, the microhardness of particle reinforced metal matrix composite coatings fabricated by cold spraying (CS) could be significantly increased compared to pure metallic coatings by CS. However, the correlation between the strengthening mechanism of reinforcements and the microhardness increment is still not well revealed. Therefore, in this study, two strengthening mechanisms of reinforcement particles in CSTiNp/Al5356 coatings, i.e. the strain hardening effect of reinforcement particles tamping on the metal matrix and the dispersion strengthening effect of uniformly dispersed reinforcement particles, were studied, and the proportions by two strengthening effects were qualitatively characterised as a first approximation by a proposed microhardness calculation model based on the hardness data of both the as sprayed and heat treated coatings. Results show that the dispersion strengthening effect of TiN particles plays a greater role in microhardness increment than the strain hardenin...

Linear friction welds of a Ti2AlNb-based alloy were subjected to post-weld heat treatment (PWHT) at 815 °C × 1 h (PWHT1) and at 1000 °C × 1 h + 815 °C × 2 h (PWHT2) followed by air cooling. The microstructure and mechanical properties of the joints under as weld and PWHT conditions were investigated. The results indicate that in the as weld joint, the weld zone mainly consists of B2 phase while the quantity of α2 and O phase is relatively small, and most O phase gradually turns into B2 phase when the amount of α2 phase reduces as well in thermo-mechanically affected zone (TMAZ). After PWHT1, O precipitates within recrystallized B2 grains can be found in weld zone and the decomposition of α2 phase caused by niobium diffusion is found in TMAZ. PWHT1 have significantly enhanced the mechanical properties due to the O phase precipitation hardening and refined grain strengthening. And the coarsening of the microstructure in weld zone under PWHT2 is evident, which consequently reduces the elongation. Keywords: Linear friction welding, Ti2AlNb-based alloy, Post-weld heat treatment, Microstructure, Mechanical property

The present paper studied the effect of SiC particle size on microstructure and mechanical properties of Al5056/SiCp composite coatings. A wide powder size range varying from 2 to 67 μm assured the differences in the particle velocity and kinetic energy of the used SiC powders. Simulation results show that the velocity of SiC particle decreases with the increase of the particle size, while the kinetic energy greatly increases with the increase of particle size. The experimental microstructure observations show that the SiC content in the coatings decreases with the decrease of the SiC particle size under the bow shock effect due to the inferior kinetic energy. The microhardness of all the composite coatings is higher than that of the pure Al5056 coating, and the SiC powder in the coating could play a double face effect on the cohesion strength of the coatings.

The aim of this study was to evaluate the microstructure, hardness, tensile and fatigue properties of electron beam welded dissimilar joints between Ti–6Al–4V and IMI834 (Ti–6Al–5Sn–2Zr–1Mo–0.35Si–1Nd) titanium alloys. A significant microstructural change was observed to occur after welding, with martensite in the fusion zone (FZ) and in the heat-affected zone (HAZ) of Ti–6Al–4V side, and martensite plus some retained α phase in the HAZ of IMI834 side. An asymmetrical hardness profile across the dissimilar joint was obtained in the dissimilar joint with a higher hardness value in the FZ. Fatigue life of the dissimilar joint was nearly the same as that of the BMs. The dissimilar joint exhibited cyclic stabilization at lower strain amplitudes up to 0.6%, while cyclic softening occurred after initial cyclic stabilization at higher strain amplitudes. Fatigue failure of the dissimilar joints occurred in the IMI834 BM, with crack initiation from the specimen surface or near-surface defect and crack propagation characterized by fatigue striations along with secondary cracks.

Nickel-based superalloy joints were welded by linear friction welding under different processing conditions. The influences of process parameters on microstructure and mechanical properties of joints were investigated. The results indicate that sound microstructure such as fine recrystallized grains in the weld zone could be obtained under certain conditions. Microstructural examination shows that grains in the thermomechanically affected zone present no obvious deformation. Moreover, the segregation of some impurity elements along grain boundaries and the reversion of γ″ and γ′ caused by high interface temperature during welding lead to the reduction of joint mechanical property. The microhardness and tensile strength of joints are lower than those of the parent metal. In addition, a weak layer including residues of oxides and carbides on the extremities of the joint is formed unexpectedly, which is detrimental to joint integrity. Keywords: Linear friction welding, Nickel-based superalloy, Microstructure, Mechanical property

A third-generation Al–Li alloy AA2198 has been successfully welded by bobbin tool friction stir welding. The stirred zone, displaying an hourglass shape, consists of recrystallized Al grains and precipitates remaining in solution. Joint line remnants have been found in all etched welds. Symmetrical hardness profiles have been obtained in the thickness direction, which indicates that the joints have homogenous through-thickness mechanical properties. As the rotational speed increases, the grain size of the stirred zone increases, whereas the density of strengthening particles decreases; the joint line remnants become compressed remarkably in the shoulder-dominated zone while less changes occur in the probe-dominated zone; the softest region shrinks and shifts outward, the average hardness of the stirred zone increases and the hardness profile along the cross section of the joint changes from the U-shaped to W-shaped. The tensile strength of the joint initially increases with rotational speed and then decreases with the maximal strength efficiency reaching 80%; three fracture modes have been observed and cracking initiates at the joint line remnant propagating towards the heat-affected zone, and finally to the border between the thermal-mechanically affected zone and stirred zone. Keywords: Friction stir welding, Bobbin tool, Al–Li alloy, Microstructure, Joint line remnant, Mechanical properties

Aim Spatial deficits are widely observed in normal ageing and early Alzheimer’s disease. This review systematically examined neuroimaging evidence for structural and functional differences in the hippocampus (HC) associated with non-pathological age-related changes in allocentric spatial abilities. Methods Databases were searched to identify peer-reviewed studies on allocentric spatial processing in normal ageing including MRI or fMRI data. 15 eligible studies were reviewed after applying exclusion criteria and quality assessment. Results There was a marked deficit in allocentric spatial processing and trend towards egocentric strategies in older adults when compared to young controls or across the lifespan, associated in the majority of studies with HC volumetric changes, metabolic or microstructural indicators, and underactivity. A few studies reported no significant correlations. Conclusion Findings confirm literature supporting an age-related allocentric spatial processing deficit and a shift towards egocentric strategies. A majority of studies implicated HC atrophy, microstructural/metabolic alterations or functional changes in age-related allocentric spatial impairment. More sensitive imaging techniques and ecologically valid spatial tasks are needed to detect subtle changes in the HC and brain’s navigational network.

Studies of gender cognitive differences in schizophrenia have reported mixed results. This study examined cognitive correlates including demographics, symptoms and functioning in men and women in a large sample of first-episode adult-onset psychosis patients. Detailed demographic, clinical and functioning data were collected from 360 first-episode patients upon admission into an early intervention service for psychotic disorders. They were also administered a comprehensive neurocognitive battery. Correlation analyses showed that memory and working memory were more significantly associated with onset age, negative symptoms and side effects in women. Processing speed correlated with antipsychotic dosage in men and side effects in women. Selective attention correlated with reality distortion and negative symptoms in women, and onset age and education in men. Executive function correlated with onset age and reality distortion in women. All cognitive domains significantly correlated with educational level and functioning in both genders. Negative symptoms explained significant variability in cognition in both genders, while reality distortion, side effects and affective symptoms were significant factors that differentiated between genders. Although there are similarities in cognitive deficits, considerable heterogeneity exists in associations of symptoms and cognition in men and women. Results facilitate individualised tailoring of interventions, including cognitive remediation therapy.

Using cold spraying (CS), a surface layer with a modified microstructure and enhanced mechanical properties was formed on a 3.2 mm thick friction stir welded (FSW) AA2024-T3 joint. The combined effect of “shot peening effect (SPE)” and “heat flow effect (HFE)” during CS were used to enhance joint mechanical properties. The microstructure evolution of the FSW AA2024-T3 joints in the surface layer following CS coatings and their effect on mechanical properties were systematically characterized with electron back-scattered diffraction, transmission electron microscopy, differential scanning calorimetry and mechanical tests. Based on these experiments, a grain refinement, finer and more S phases, and improved amount of Guinier-Preston-Bagaryatsky (GPB) zones produced by CS treatments are proposed. The deposition of aluminium coating on the joint, lead to hardness recovery in the stir zone and the development of two low hardness zones as the density of GPB increased. The tensile properties of FSW AA2024-T3 joints improved with the application of the aluminium coatings. Experiments and analysis of the enhanced mechanical properties mechanism indicate that SPE with a high plastic deformation and HFE with an intensive heat flow are necessary for the production of refined grains and increased numbers of GPB zones.

This study investigated the global anisotropy of the friction stir welded (FSW) AA2024-T3 sheets. Different rotation speeds were used to generate welds. Uniaxial tensile tests were performed at various loading angles with respect to the welding direction. The deformation history during tensile tests was investigated by using the digital image correlation method to obtain r -values. Plastic anisotropy of the joints was modeled with Hill48, Yld89 and Yld2000-2d yield functions. The performance of these three yield criteria was evaluated by the comparison of theoretically calculated planar distributions of the uniaxial yield stress and the r -values with experimental data. Results show that the FSW joints show strong fracture and yield anisotropies. The yield stress is invariably the lowest in the diagonal direction and the highest in the rolling direction. The tensile strength and elongation are always the lowest at loading angles of 60° or 75°, rather than the commonly used 90°. The Yld2000-2d yield function can accurately describe the in-plane anisotropy of the joints compared to the other two. Rotation speed has a distinct effect on the mechanical properties of the FSW joints, resulting in evident changes in the shapes and magnitudes of the yield surfaces.

An aluminum coating was deposited on the surface of a friction stir welded 2024-T351 aluminum alloy joint via cold spraying for corrosion protection. The results show that a relatively dense coating could be formed except some pores on the coating surface layer under certain spray conditions, and the bonding between the coating and the weld surface seems good. Immersion tests in the exfoliation solution confirm that the presence of pure Al coating significantly decreases the corrosion attack. The most important finding is that the tensile properties of friction stir welds are improved after coating deposition. Taking into account the increased microhardness near the joint surface, the shot-peening effect and the release of residual stresses during particles deposition contribute to the improvement of joint tensile strength. Therefore, the combination of these two solid-state processing techniques will generate synergistic effects on the joint performance in service.

Studies have shown that early- and adult-onset schizophrenia patients differ in pre-morbid traits, illness presentation, psychopathology, and prognosis. We aimed to compare adult-onset patients (age range 26–55 years) with an adolescent-onset cohort (15–25 years) in demographics, illness presentation and functioning at baseline. Participants were from two territory-wide early intervention services for adolescent-onset ( n =671) and adult-onset psychosis patients ( n =360) in Hong Kong. The adolescent-onset cohort had their initial psychotic episode from 2001–2003; retrospective data collection was done through systematic case note review. The adult-onset cohort was recruited for a larger interventional study from 2009–2011; information was collected via face-to-face interviews. Adult-onset psychosis was significantly associated with more females, fewer smokers, more non-local birth, more full-time employment, better functioning, poorer medication adherence, more psychiatric hospitalization and fewer with schizophrenia than adolescent-onset psychosis (mean age: 20.4). The effect sizes were small, except for medication adherence where a robust effect was found. No group difference in DUP was found. The finding that adult-onset patients had better functioning challenges the view that adolescent- and adult-onset psychoses share a similar prognostic trajectory. Implications for adapting intervention processes for adolescent- and adult-onset psychosis are discussed.

Probeless friction stir spot welding (probeless FSSW) is a useful variant of conventional friction stir spot welding (FSSW), where there is no probe at the end of the tool shoulder. In this study, AA2198-T8 aluminum-lithium alloy has been successfully welded by probeless FSSW. The variations of geometric features of probeless FSSWed joints: stir zone width, stir zone edge angle and hook angle, and their effects on the joint mechanical properties were studied quantitatively. Results show that the width of stir zone is constrained by shoulder diameter, and the ratio of the width to shoulder diameter approaches 0.9. With the increase of stir zone depth, the stir zone edge angle approaches 45° eventually during the welding process. Additionally, the hook defect can be found among all of the probeless FSSWed joints due to the upward material flow of the lower sheet. When the hook angle is around 90°, the tensile/shear strength reaches a relatively higher value. The fracture mode changes from shear fracture to plug fracture when hook angle transforms from obtuse to acute.

The overburning temperature of the ZL205A (Al–5Cu–0·4Mn) alloy is first determined by differential scanning calorimetry analysis. Then, the solid solution temperature of ZL205A was determined by metallurgical microstructure observation. Isothermal compression tests of the as quenched ZL205A were conducted in temperature from 25 to 500°C and the strain rate from 0·001 to 1 s−1. The deformation behaviour of the as quenched ZL205A was investigated. The prediction of the flow stresses were studied using artificial neural network. The average absolute relative error between the predicted flow stresses and experimental results is 4·4%, which demonstrates that the network proposed in the present paper has high precision. Therefore, it can be chosen as a thermomechanical model to treat the distortion problems of components during quenching process.

The present study examined sequence variability in two mitochondrial DNA (mtDNA) regions, namely cytochrome c oxidase subunit 1 (cox1) and NADH dehydrogenase subunit 1 (nad1), and internal transcribed spacer (ITS) of nuclear ribosomal DNA (rDNA) among Oesophagostomum asperum isolates from goats in Hunan Province, China. A portion of the cox1 (pcox1), nad1 (pnad1) genes and the ITS (ITS1+5.8S rDNA+ITS2) rDNA were amplified by polymerase chain reaction (PCR) separately from adult O. asperum individuals and the representative amplicons were subjected to sequencing from both directions. The lengths of pcox1, pnad1 and ITS rDNA were 366 bp, 681 bp and 785 bp, respectively. The A+T contents of gene sequences were 71.5–72% for pcox1, 73.7–74.2% for pnad1 and 58–58.8% for ITS rDNA. Intra-specific sequence variations within O. asperum were 0–1.6% for pcox1, 0–1.9% for pnad1 and 0–1.7% for ITS rDNA, while inter-specific sequence differences among members of the genus Oesophagostomum were significantly higher, being 11.1–12.5%, 13.3–17.7% and 8.5–18.6% for pcox1, pnad1 and ITS rDNA, respectively. Phylogenetic analyses using combined sequences of pcox1 and pnad1, with three different computational algorithms (Bayesian inference, maximum likelihood and maximum parsimony), revealed distinct groups with high statistical support. These findings demonstrated the existence of intra-specific variation in mtDNA and rDNA sequences among O. asperum isolates from goats in Hunan Province, China, and have implications for studying molecular epidemiology and population genetics of O. asperum.

Linear friction welds of Ti–6Al–4V (TC4, according to Chinese classification) to Ti–6·5Al–3·5Mo–1·5Zr–0·3Si (TC11, according to Chinese classification) were subject to post-weld heat treatment (PWHT) at 650°C×4 h (PWHT1) and at 950°C×1 h+530°C×4 h (PWHT2) under air cooling. In the as welded joint, TC4 had recrystallised sufficiently compared to TC11. After PWHT1, the α grains in the TC4 weld centre zone grew to some extent and many superfine equiaxed recrystallised α grains precipitated along β boundaries on the TC11 side. The grain growth along the weld line in the weld centre zone under PWHT2 was evident. PWHT2 reduced the joint tensile strength due to the coarsening of the microstructure. The joint microhardness decreased after PWHT.

Cold sprayed composite coatings are usually composed of extensively deformed metal particles and undeformed hard reinforcements. Generally, there is a difference in the composition between the feedstock powder and the final coating. The reason was explored based on the deposition behaviour of cold sprayed composite coatings, which are composed of different combinations of matrix and reinforcement (Al5056+SiC, AZ91D+SiC and Al5056+In718). Experimental results show that a higher reinforcement content in the coating contributes from a higher deposition efficiency of the reinforcement. The great difference in the impact velocity between the matrix and the reinforcement mainly causes the difference in the reinforcement content between the starting powder and the resultant coating. Finally, when the particle velocity of the reinforcement is comparable to that of the matrix, the superior kinetic energy of the matrix or the reinforcement could benefit the incorporation of the reinforcement.

A series of welds were made by friction stir welding (FSW) under different welding and rotation speeds. A 2D ultimate tensile strength (UTS) map was developed based on various experimental data to predict the UTS of friction stir welded AA2024 alloy joints. The accuracy of the UTS map was evaluated by comparing the estimated UTS with the corresponding experimental results from the FSW of the same material available in the open literature. Analytical models were developed to estimate the peak temperature and grain size in the nugget zone. The predicted optimal peak temperature and welding and rotation speeds for AA2024 were within the windows of 400–465 °C, 175–350 mm/min and 800–1,200 rpm, respectively, under which the joint tensile strength could be higher than 458 MPa (about 94.6 % of the base metal) and the estimated average grain sizes in the nugget zone were about 2–3.9 μm.