Effect of thermal-cooling cycle treatment on thermal expansion behavior of particulate reinforced aluminum matrix composites

Two micron SiC particles with angular and spherical shape and the sub-micron Al2O3 particles with spherical shape were introduced to reinforce 6061 aluminium by squeeze casting technology. Microstructures and effect of thermal-cooling cycle treatment （TCCT） on the thermal expansion behaviors of three composites were investigated. The results show that the composites are free of porosity and SiC/Al2O3 particles are distributed uniformly. Inflections at about 300℃ are observed in coefficient of thermal expansion （CTE） versus temperature curves of two SiCp/Al composites, and this characteristic is not affected by TCCT. The TCCT has significant effect on thermal expansion behavior of SiCp/Al composites and CTE of them after 3 cycles is lower than that of 1 or 5 cycles. However, no inflection is observed in Al2O3p/Al composite, while TCCT has effect on CTE of Al2O3p/Al composite. These results should be due to different relaxation behavior of internal stress in three composites.

Effect of Thermal-cold Cycling Treatment on Mechanical Properties and Microstructure of 6061 Aluminum Alloy

The influence of thermal-cold cycling treatment on mechanical properties and microstructure of 6061 aluminum alloy was investigated by means of tensile test, optical microscopy(OM), X-ray diffraction(XRD) and transmission electron microscopy(TEM). The cryogenic treatment mechanism of the alloys was discussed. The results show that thermal-cold cycling treatment is beneficial since it produces a large number of dislocations and accelerates the ageing process of the alloy and yields the finer dispersed β" precipitates in the matrix. This variation of microstructural changes leads to more favorable mechanical properties than the other investigated states, while grain boundary precipitation is coarse and distributed discontinuously along grain boundaries, with a lower precipitation free zone(PEZ) on the both sides of precipitated phase. As a result, the tensile strength, elongation and conductivity of 6061 aluminum alloy after thermal-cold cycling treatment are 373.37 MPa, 17.2% and 28.2 MS/m, respectively. Compared with conventional T6 temper, the mechanical properties are improved significantly.

Influence of Ageing Heat Treatment on the High Cycle Fatigue of an 8090 Al-Li Alloy

Fatigue lives for the smooth and notched specimens of 8090 Al-Li alloy jn the different ageing conditions have been studied. For the smooth samples of 8090 alloy the artificial ageing results in an increase in fatigue life in comparison with natural ageing. On the contrary, the notched specimens of 8090 alloy in the naturally aged condition show higher fatigue life than in the peak-aged. The exposure to either the peak-aged or naturally aged leads to superior fatigue properties of Al-Li alloy to the traditional high strength aluminum alloys of 7075 and 2024, especially in the latter aged condition. In all ageing conditions, i,e. naturally, under-, peak- and over-aged, the peak-aged 8090 alloy displays the highest fatigue life and the over-aged material has a minimum value at the same stress amplitude. The difference in fatigue life is mainly attributable to the size and distribution of strengthening precipitates as well as the wide of precipitate free zones (PFZ's) along grain boundaries.

The choice of a neoadjuvant chemotherapy cycle for breast cancer has significance in clinical practice: results from a population-based, real world study

Objective:Neoadjuvant chemotherapy(NAC)is currently used in both early stage and locally advanced breast cancers.The survival benefits of standard vs.non-standard NAC cycles are still unclear.This study aimed to investigate the relationship between NAC cycles and survival based on real world data.Methods:We identified patients diagnosed with invasive primary breast cancers who underwent NAC followed by surgery.Patients who received at least 4 NAC cycles were defined as having received standard cycles,while patients who received less than 4 NAC cycles were defined as having received non-standard cycles.Kaplan-Meier curves and Cox proportional hazard models were used to estimate the disease-free survival(DFS)and overall survival(OS).Results:Of the 1,024 included patients,700 patients received standard NAC cycles and 324 patients received non-standard NAC cycles.The DFS estimates were 87.1%and 81.0%(P=0.007)and the OS estimates were 90.0%and 82.6%(P=0.001)in the standard and non-standard groups,respectively.Using multivariate analyses,patients treated with standard NAC cycles showed significant survival benefits in both DFS[hazard ratio(HR):0.62,95%confidence interval(CI):0.44–0.88]and OS(HR:0.54,95%CI:0.37–0.79).Using stratified analyses,standard NAC cycles were associated with improved DFS(HR:0.59,95%CI:0.36–0.96)and OS(HR:0.49,95%CI:0.28–0.86)in the HER2 positive group.Similar DFS(HR:0.50,95%CI:0.25–0.98)and OS(HR:0.45,95%CI:0.22–0.91)benefits were shown for the triple negative group.Conclusions:Standard NAC cycles were associated with a significant survival benefit,especially in patients with HER2 positive or triple negative breast cancer.

Effects of the number of neoadjuvant therapy cycles on clinical outcomes, safety, and survival in patients with metastatic colorectal cancer undergoing metastasectomy

The controversial outcomes in patients with metastatic colorectal cancer(mCRC)highlight the need for developing effective systemic neoadjuvant treatment strategies to improve clinical results.The optimal treatment cycles in patients with mCRC for metastasectomy remain undefined.This retrospective study compared the efficacy,safety,and survival of cycles of neoadjuvant chemotherapy/targeted therapy for such patients.Sixty-four patients with mCRC who received neoadjuvant chemotherapy/targeted therapy following metastasectomy were enrolled between January 2018 and April 2022.Twenty-eight patients received 6 cycles of chemotherapy/targeted therapy,whereas 36 patients received≥7 cycles(median,13;range,7–20).Clinical outcomes,including response,progression-free survival(PFS),overall survival(OS),and adverse events,were compared between these two groups.Of the 64 patients,47(73.4%)were included in the response group,and 17(26.6%)were included in the nonresponse group.The analysis revealed chemotherapy/targeted therapy cycle and pretreatment serum carcinoembryonic antigen(CEA)level as independent predictors of the response as well as overall survival and chemotherapy/targeted therapy cycle as an independent predictor of progression(all p<0.05).Furthermore,our results revealed shorter operation time,lower estimated operative blood loss,higher response rate,lower progression rate,and higher survival rate in≥7 cycles of chemotherapy/targeted therapy group(all p<0.05),but no statistical differences in adverse events were observed between the two groups(all p>0.05).The median OS and PFS were 48 months(95%CI,40.855–55.145)and 28 months(95%CI,18.952–37.48)in the≥7-cycle group and 24 months(95%CI,22.038–25.962)and 13 months(95%CI,11.674–14.326)in the 6-cycle group,respectively(both p<0.001).The oncological outcomes in the≥7-cycle group were significantly better than those in the 6-cycle group,without significant increases in adverse events.However,prospective randomized trials are mandatory to confirm the potential advantages of cycle numbers of neoadjuvant chemotherapy/targeted therapy.

Effect of Thermal Cycling Treatment on Microyield Behavior of Al_2O_3p/Al Composite

An aluminum alloy (6061) matrix composite reinforced with 35% (vol.) Al 2O 3 particles was fabricated by squeeze casting method. The Al 2O 3 particles were spherical. The microyield behavior of the composite and the effect of different thermal cycling treatment on the microyield behaviors of the composite were studied. Based on TEM and HREM observation of microstructure, the mechanism of microyield behavior in the Al 2O 3p/6061 composite was analyzed. The results indicate that the microyield behavior of the Al 2O 3p/6061 composite can be described by Brown Lukens theory, which was used satisfactorily for aluminum alloys and other light alloys, and is affected greatly by the different thermal cycling treatment. The more the cycles of thermal cycling treatment, the higher to microyield strength at small strains. Thermal cycling treatment affects mainly the thermal mismatch stress and the density of movable dislocations in the matrix.

Nanoscopic tribological characteristics of a cryogenically cycled Zr-based metallic glass

Optimized macroscopic tribological behavior can be anticipated in metallic glasses(MGs)by cryogenic cycling treatment(CCT),which is attributed to enhanced plasticity.However,the intrinsic friction mechanisms of MGs induced by cryogenic rejuvenation are still poorly understood.In the present study,nanoscopic wear tests were conducted on the Zr-based MGs surface with different CCT cycles using atomic force microscopy(AFM).After CCT treatment with 100 cycles,the MG displays the highest adhesion and ploughing frictions,but significantly improved anti-wear properties.Adhesion tests and molecular dynamics simulations disclose that the increased adhesion is attributed to the dominance of liquid-like regions in the CCT-treated MGs,and the impact of reduced hardness and weak elastic recovery results in the deteriorated ploughing friction.The enhanced plasticity effectively dissipates the strain from the AFM tip through multiple shear bands and weakens the adhesion during deformation,giving rise to excellent wear resistance.This study elucidates the promoting effect of CCT on the outstanding antiwear performance of MGs,and is helpful for the development of novel alloys.

Effect of Spinning Process on Properties of Polyglycollide Acid Embedding Materials

Acupoint catgut embedding therapy(ACET),filling the gaps of traditional Chinese medicine acupuncture treatment,has been widely used for the treatment of many diseases with significant effects.The aim of this paper is to obtain polyglycollide acid(PGA)fibers with higher performance at a lower cost,and ensure that PGA can meet the clinical requirements as well.PGA fibers with different diameters were spun as embedding materials.The mechanical performance,thermodynamic and biodegradable properties of PGA fibers were studied under different spinning process parameters,including spinning speed,drawing temperature and stretching ratio.The experimental results showed that the optimum spinning parameters were the spinning speed at 150 m/min,the drawing temperature of 45 ℃,and the stretching ratio of 4.0.The initial modulus of PGA fibers was 3.876 N/tex.The crystallization degree was 68% and the degradation performance was in consistent with treatment cycle of patients.

Low intensity ultrasound stimulates biological activity of aerobic activated sludge

This work aims to explore a procedure to improve biological wastewater treatment efficiency using low inten-sity ultrasound.The aerobic activated sludge from a munici-pal wastewater treatment plant was used as the experimental material.Oxygen uptake rate(OUR)of the activated sludge(AS)was determined to indicate the changes of AS activity stimulated by ultrasound at 35 kHz for 0-40 min with ultrasonic intensities of 0-1.2 W/cm^(2).The highest OUR was observed at the ultrasonic intensity of 0.3 W/cm^(2) and an irradiation period of 10 min;more than 15%increase was achieved immediately after sonication.More significantly,the AS activity stimulated by ultrasound could last 24 h after sonication,and the AS activity achieved its peak value within 8 h after sonication,or nearly 100%higher than the initial level after sonication.Therefore,to improve the wastewater treatment efficiency of bioreactors,ultrasound with an intensity of 0.3 W/cm^(2) could be employed to irradiate a part of the AS in the bioreactor for 10 min every 8 h.

Effect of cryogenic cycling on mechanical properties of ZrTiCuNiBe bulk metallic glass

The effect of deep cryogenic cycle treatment(DCT)on Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5)(Vit-1)bulk metallic glass(BMG)prepared from high-purity raw materials was investigated.After DCT,no obvious rejuvenation of the samples was detected.With an increasing number of cryogenic cycles,the hardness of the samples first decreased and then increased,the room-temperature compression plasticity first increased and then generally remained unchanged,and the impact toughness underwent almost no obvious change.The absence of rejuvenation was attributed to the high fragility index(47-50)and high glass forming ability(GFA)of the material.As lower purity of the raw materials is expected in practical applications,DCT of Vit-1 BMG prepared from low-purity raw materials was also performed.After DCT,the samples prepared with the lower-purity raw materials were clearly rejuvenated,and the room-temperature mechanical properties improved significantly.Both the compression plasticity and impact toughness reached peak values after 5 cryogenic cycles.The initial impurities(including Y and O)had a complex and comprehensive effect on the deformation mechanism of the BMG during DCT.Our findings indicate that the structural heterogeneity,fragility index,and GFA of the BMG alter the effect of DCT.

Inspirations from the scientific discovery of the anammox bacteria: A classic example of how scientific principles can guide discovery and development

Anaerobic ammonium oxidation(anammox) is a relatively new pathway within the N cycle discovered in the late 1990 s. This eminent discovery not only modified the classical theory of biological metabolism and matter cycling, but also profoundly influenced our understanding of the energy sources for life. A new member of chemolithoautotrophic microorganisms capable of carbon fixation was found in the vast deep dark ocean. If the discovery of the chemosynthetic ecosystems in the deep-sea hydrothermal vent environments once challenged the old dogma "all living things depend on the sun for growth," the discovery of anammox bacteria that are widespread in anoxic environments fortifies the victory over this dogma. Anammox bacteria catalyze the oxidization of NH_4^+ by using NO_2^- as the terminal electron acceptor to produce N_2. Similar to the denitrifying microorganisms, anammox bacteria play a biogeochemical role of inorganic N removal from the environment. However, unlike heterotrophic denitrifying bacteria, anammox bacteria are chemolithoautotrophs that can generate transmembrane proton motive force, synthesize ATP molecules and further carry out CO_2 fixation through metabolic energy harvested from the anammox process. Although anammox bacteria and the subsequently found ammonia-oxidizing archaea(AOA), another very important group of N cycling microorganisms are both chemolithoautotrophs, AOA use ammonia rather than ammonium as the electron donor and O_2 as the terminal electron acceptor in their energy metabolism. Therefore, the ecological process of AOA mainly takes place in oxic seawater and sediments, while anammox bacteria are widely distributed in anoxic water and sediments, and even in some typical extreme marine environments such as the deep-sea hydrothermal vents and methane seeps. Studies have shown that the anammox process may be responsible for 30%–70% N_2 production in the ocean. In environmental engineering related to nitrogenous wastewater treatment, anammox provides a new technology with low energy consumption, low cost, and high efficiency that can achieve energy saving and emission reduction. However, the discovery of anammox bacteria is actually a hard-won achievement. Early in the 1960 s, the possibility of the anammox biogeochemical process was predicted to exist according to some marine geochemical data. Then in the 1970 s, the existence of anammox bacteria was further predicted via chemical reaction thermodynamic calculations. However, these microorganisms were not found in subsequent decades. What hindered the discovery of anammox bacteria, an important N cycling microbial group widespread in hypoxic and anoxic environments? What are the factors that finally led to their discovery? What are the inspirations that the analyses of these questions can bring to scientific research? This review article will analyze and elucidate the above questions by presenting the fundamental physiological and ecological characteristics of the marine anammox bacteria and the principles of scientific research.