Recent advancements in thermal conductivity of magnesium alloys

As highly integrated circuits continue to advance,accompanied by a growing demand for energy efficiency and weight reduction,materials are confronted with mounting challenges pertaining to thermal conductivity and lightweight properties.By virtue of numerous intrinsic mechanisms,as a result,the thermal conductivity and mechanical properties of the Mg alloys are often inversely related,which becomes a bottleneck limiting the application of Mg alloys.Based on several effective modification methods to improve the thermal conductivity of Mg alloys,this paper describes the law of how they affect the mechanical properties,and clearly indicates that peak aging treatment is one of the best ways to simultaneously enhance an alloy's thermal conductivity and mechanical properties.As the most frequently used Mg alloy,cast alloys exhibit substantial potential for achieving high thermal conductivity.Moreover,recent reports indicate that hot deformation can significantly improve the mechanical properties while maintaining,and potentially slightly enhancing,the alloy's thermal conductivity.This presents a meaningful way to develop Mg alloys for applications in the field of small-volume heat dissipation components that require high strength.This comprehensive review begins by outlining standard testing and prediction methods,followed by the theoretical models used to predict thermal conductivity,and then explores the primary influencing factors affecting thermal conductivity.The review summarizes the current development status of Mg alloys,focusing on the quest for alloys that offer both high thermal conductivity and high strength.It concludes by providing insights into forthcoming prospects and challenges within this field.

The Bright Single Pulse Emission from PSR B1133+16

We have conducted a comprehensive investigation into the bright single pulse emission from PSR B1133+16using the Giant Metrewave Radio Telescope.High time resolution data(61μs)were obtained at a center frequency of 322 MHz with a bandwidth of 32 MHz over a continuous observation period of 7.45 hr.A total of 1082 bright pulses were sporadically detected with peak flux densities ranging from 10 to 23 times stronger than the average pulse profile.However,no giant pulse-like emission with a relative pulse energy larger than 10 and extremely short duration was detected,indicating that these bright pulses cannot be categorized as giant pulse emission.The majority of these bright pulses are concentrated in pulse phases at both the leading and trailing windows of the average pulse profile,with an occurrence ratio of approximately 2.74.The pulse energy distribution for all individual pulses can be described by a combination of two Gaussian components and a cutoff power-law with an index of α=-3.2.An updated nulling fraction of 15.35%±0.45% was determined from the energy distribution.The emission of individual pulses follows a log-normal distribution in peak flux density ratio.It is imperative that regular phase drifting in bright pulse sequence is identified in both the leading and trailing components for the first time.Possible physical mechanisms are discussed in detail to provide insights into these observations.

KLF4 Inhibits the Activation of Human Hepatic Stellate Cell In Vitro

Objective Hepatic stellate cells(HSCs)play a crucial role in liver fibrosis.Early-stage liver fibrosis is reversible and intimately associated with the state of HSCs.Kruppel-like factor 4(KLF4)plays a pivotal role in a wide array of physiological and pathological processes.This study aimed to investigate the effect of KLF4 on the proliferation,apoptosis and phenotype of quiescent HSCs Methods We designed a KLF4 lentiviral vector and a KLF4 siRNA lentiviral vector,to upregulate and silence KLF4 expression in human HSC LX-2 cells via transfection.Cell proliferation was assessed using the CCK-8 assay.Flow cytometry was used to detect the cell cycle distribution and apoptosis rate.Western blotting was used to determine the levels of some quiescence and activation markers of HSCs Results Overexpression of KLF4 significantly increased the levels of E-cadherin and ZO-1,which are quiescent HSC markers,while significantly decreased the levels of N-cadherin and a-SMA,known activated HSC markers.In contrast,cell proliferation and apoptosis rates were elevated in LX-2 cells in which KLF4 expression was silenced Conclusion KLF4 inhibits the proliferation and activation of human LX-2 HSCs.It might be a key regulatory protein in the maintenance of HSC quiescence and may serve as a target for the inhibition of hepatic fibrosis.

Rare uterine serosal pregnancy after in vitro fertilization in a woman with bilateral salpingectomy

Objective:To improve the understanding of ectopic pregnancy after bilateral salpingectomy through case analysis and literature review.Method:A case of uterine serosal pregnancy after in vitro fertilization and embryo transfer(IVF-ET)in a woman with bilateral salpingectomy was reported in detail and summarized,and relevant literatures searched in Pubmed were analyzed.Results:The patient had a sudden abdominal pain 18 days after transplantation.Ultrasound showed no pregnancy sac in the intrauterine cavity and bilateral adnexal areas,but there was a large amount of fluid in the Pouch of Douglas,which was an indication for surgical exploration.During the operation,the pregnancy tissue was found on the uterine serosal and cleared in time.And the patient recovered well after surgery.Review of the literatures showed that most of ectopic pregnancies after bilateral salpingectomy were treated surgically and had a good prognosis.Conclusion:Ectopic pregnancy after bilateral salpingectomy is extremely rare and should be early judged by the patients’signs.Surgical treatment timely can achieve good outcome.

Microstructures and mechanical properties of titanium-reinforced magnesium matrix composites: Review and perspective

Currently, many gratifying signs of progress have been made in magnesium(Mg) matrix composites(MMCs) by virtue of their high mechanical properties both at room and elevated temperatures. Although the commonly used reinforcements in MMCs are ceramic particles,they often provide improved yield and ultimate stresses by a significant loss in ductility. Therefore, hard metallic phases were introduced as alternative candidates for the manufacturing of MMCs, especially titanium(Ti). It has a high melting point, high Young’s modulus, high plasticity, low level of mutual solubility with Mg matrix, and closer thermal expansion coefficient to that of Mg metal than that of ceramic particles. It is highly preferable to provide both high ultimate stress and ductility in Mg matrix. However, many critical challenges for the fabrication of Ti-reinforced MMCs remain, such as Ti’s homogeneity, low recovery rate, and the optimization of interfacial bonding strength between Mg and Ti, etc. Meanwhile, different fabrication methods have various effects on the microstructures, mechanical properties, and the interfacial strength of Ti-reinforced MMCs. Hence, this review placed emphasis on the microstructural characteristics and mechanical properties of Ti-reinforced MMCs fabricated by different techniques. The influencing factors that govern the strengthening mechanisms were systematically compared and discussed. Future research trends, key issues, and prospects were also proposed to develop Ti-reinforced MMCs.

Microstructure,mechanical properties and wear resistance of Ti particles reinforced AZ31 magnesium matrix composites

The compromise between strength and plasticity has greatly limited the potential application of particles reinforced magnesium matrix composites(MMCs).In this work,the Ti particles reinforced AZ31 magnesium(Mg)matrix composites achieved simultaneous improvement in strength,elongation and wear resistance.The Ti particles reinforced AZ31 composites were fabricated by ultrasonic-assisted stir casting with hot extrusion.The results showed that a strong interfacial bonding was obtained at Ti/Mg interface because of the formation of semicoherent orientation relationship of Ti Al/Mg,Ti Al/Al_(2)Ti and Al_(2)Ti/Mg interfaces.The as-extruded 6 wt.%Ti/AZ31 composite presented the best compressive mechanical properties and wear resistance with ultimate tensile strength,elongation and wear rate of 327 MPa,20.4%and 9.026×10^(-3)mm^(3)/m,obviously higher than those of AZ31 alloys.The enhanced mechanical properties were attributed to the grain refinement and strong interfacial bonding.The improved wear resistance was closely related to the increased hardness of composites and the formation of protective oxidation films.

执法管理化:法律的组织运作逻辑--基于对违法建筑拆除的个案考察

虽然公共行政中一直存在法律主义和管理主义的争论,但行政组织如何理解和应用法律却一直未得到足够的关注。行政组织的运作主要是按照管理主义的逻辑,强调通过有效调配组织资源,以实现特定目标;法律的运作主要是遵循法律主义的逻辑,注重的是基于合法/非法作为符码的规范性评价,二者在理论和实践中存在一定的紧张关系。当遇到公共事务中的治理“难点”问题时,需要执法者与管理者共同应对。此时,法律的理念被行政组织所吸收、利用和转变的过程就形成了执法的管理化,具体表现为法律目标、内容、理念、符号和组织方式的管理化。导致执法管理化的原因在于行政对法律的吸纳,包括对法律不确定内容的意义建构、组织分包制对法律的统摄以及管理修辞对法律目的的重构。执法管理化虽然可以提高执法效率和行政组织的正当性水平,但也会导致法律的解构和执法权威的削弱。尽管如此,执法管理化充分体现了我国行政管理和行政执法相融合的方式之一,对于深化行政执法体制改革,协调法律的管理者角色和监管者角色之间的内在紧张,推进行政法学体系转型,提高公共行政管理的法治化水平具有重要启示意义。

Metabolic enzyme inhibitory abilities, in vivo hypoglycemic ability of palmleaf raspberry fruits extracts and identification of hypoglycemic compounds

The unripe palmleaf raspberry,namely Fupenzi(FPZ),is an important medicinal and edible food.This study aims to evaluate the potential of FPZ extracts prepared with different approaches in attenuating hyperglycemia,gout,Alzheimer’s disease,and pigmentation,to obtain the enriching fraction and to identify the major active compounds.Results indicated that FPZ extracts showed weak activity against acetylcholinesterase,considerable ability against tyrosinase and xanthine oxidase,but excellent inhibition onα-glucosidase.Ultrasound-assisted 40%ethanol extract(40EUS)gave the highest phenolics content,and the bestα-glucosidase inhibition(IC_(50)=0.08μg/mL),which is 877-fold higher than that of positive control acarbose.The 40%ethanol eluting fraction of 40EUS showed the strongestα-glucosidase inhibition with the IC_(50) value of 37.79 ng/mL,it could also effectively attenuate the fasting blood glucose level and oral glucose tolerance of C57BL/6 mice.Twenty-six compounds were identified from 40%ethanol fraction by using HPLC-QTOF-MS/MS,hydrolysable tannins(including 11 ellagitannins and 4 gallotannins)were the major compounds,phenolic acids came to the second.Above results could provide important technical supporting for the further application and research of FPZ in health foods and drugs against diabetes.

Rational design, synthesis and prospect of biodegradable magnesium alloy vascular stents

Biodegradable magnesium(Mg) alloys are expected to be promising materials for cardiovascular stents(CVS), which can avoid the longterm clinical problems of current CVS, such as in-stent restenosis, late stent thrombosis, etc. Mg alloy stents exhibit superior biocompatibility and tunable biodegradability, compared with conventional permanent metallic stents. However, the poor formability and non-uniform corrosion of Mg alloy stents hinder their clinical application of CVS. This review focuses on the development of Mg alloys for CVS in recent years.According to the results of bibliometric analysis, we analyzed different biodegradable Mg alloy systems. Moreover, the structural design strategies for Mg alloy stents that can reduce the stress concentration, as well as the surface modification methods to control the corrosion behavior and biological performance of Mg alloy stents are also highlighted. At last, this review systematically discussed the potential directions and challenges of biodegradable magnesium stents(BMgS) in cardiovascular fields.

Experimental and theoretical studies on two-dimensional vanadium carbide hybrid nanomaterials derived from V_(4)AlC_(3) as excellent catalyst for MgH_(2)

Hydrogen is considered one of the most ideal future energy carriers.The safe storage and convenient transportation of hydrogen are key factors for the utilization of hydrogen energy.In the current investigation,two-dimensional vanadium carbide(VC) was prepared by an etching method using V_(4)AlC_(3) as a precursor and then employed to enhance the hydrogen storage properties of MgH_(2).The studied results indicate that VC-doped MgH_(2) can absorb hydrogen at room temperature and release hydrogen at 170℃. Moreover,it absorbs 5.0 wt.%of H_(2) within 9.8 min at 100℃ and desorbs 5.0 wt.% of H_(2) within 3.2 min at 300℃.The dehydrogenation apparent activation energy of VC-doped MgH_(2) is 89.3 ± 2.8 kJ/mol,which is far lower than that of additive-free MgH_(2)(138.5 ± 2.4 kJ/mol),respectively.Ab-initio simulations showed that VC can stretch Mg-H bonds and make the Mg-H bonds easier to break,which is responsible for the decrease of dehydrogenation temperature and conducive to accelerating the diffusion rate of hydrogen atoms,thus,the hydrogen storage properties of MgH_(2) are remarkable improved through addition of VC.

On Promoting Listening Comprehension of English Majors through Original English Movies

In recent years,with the reform of College English Teaching in China,listening has occupied a great proportion of both the examination content and classroom teaching.When everyone is seeking a high-efficiency,fast teaching method,the use of English original film teaching methods arises spontaneously.Its authentic speaking style,real language environment and rich cultural connotation not only improve the listening comprehension ability of English majors,but also enable students to intuitively understand the culture of Western countries.In this study,by referring to a large number of books and documents,this paper puts forward corresponding strategies for various problems arising from the use of English original film teaching in colleges and universities.English original film teaching can not only create a better learning environment,and stimulate students’interest in learning,but also enable students to actively participate in class discussions.

脊柱内镜下经椎板间入路腰椎间盘切除术的并发症及防治策略分析

目的分析脊柱内镜下经椎板间入路腰椎间盘切除术(PEID)治疗腰椎间盘突出症的手术并发症,并探讨其防治策略。方法回顾性分析深圳市第六人民医院2016年3月-2017年6月收治的腰椎间盘突出症患者360例。其中,男216例,女144例;年龄24~68岁,平均(43.57±7.63)岁。均在全麻及C型臂X线机监视下行PEID。观察术中和术后并发症及其处理方法。结果手术时间30~90 min,平均(52.30±16.80)min。术后随访24个月。最后一次随访时,VAS评分(2.62±0.81)分较术前(7.43±1.95)分明显降低(t=4.69,P=0.017),改良MacNab评分结果显示优良率为94.17%。出现并发症19例,发生率为5.28%,其中神经根纤维束部分损伤1例,髓核部分残留3例,脑脊液渗漏1例,2例术后椎间隙感染,11例患者术后出现感觉异常,经对症处理后,恢复正常。随访24个月后,有6例患者复发,其中4例接受椎间盘镜(MED)治疗,2例接受了微创经椎间孔入路椎间融合术(MIS-TLIF)治疗。结论PEID的并发症并不少见,应严格掌握手术适应证,提高手术操作技能,并做好相应的应对措施。

Thermodynamics and kinetics of hydriding and dehydriding reactions in Mg-based hydrogen storage materials

Mg-based materials are one of the most promising hydrogen storage candidates due to their high hydrogen storage capacity,environmental benignity,and high Clarke number characteristics.However,the limited thermodynamics and kinetic properties pose major challenges for their engineering applications.Herein,we review the recent progress in improving their thermodynamics and kinetics,with an emphasis on the models and the influence of various parameters in the calculated models.Subsequently,the impact of alloying,composite,and nanocrystallization on both thermodynamics and dynamics are discussed in detail.In particular,the correlation between various modification strategies and the hydrogen capacity,dehydrogenation enthalpy and temperature,hydriding/dehydriding rates are summarized.In addition,the mechanism of hydrogen storage processes of Mg-based materials is discussed from the aspect of classical kinetic theories and microscope hydrogen transferring behavior.This review concludes with an outlook on the remaining challenge issues and prospects.

Human umbilical cord mesenchymal stem cells to treat spinal cord injury in the early chronic phase: study protocol for a prospective, multicenter, randomized, placebo-controlled, single-blinded clinical trial

Human umbilical cord mesenchymal stem cells(hUC-MSCs)support revascularization,inhibition of inflammation,regulation of apoptosis,and promotion of the release of beneficial factors.Thus,they are regarded as a promising candidate for the treatment of intractable spinal cord injury(SCI).Clinical studies on patients with early chronic SCI(from 2 months to 1 year post-injury),which is clinically common,are rare;therefore,we will conduct a prospective,multicenter,randomized,placebo-controlled,single-blinded clinical trial at the Third Affiliated Hospital of Sun Yat-sen University,West China Hospital of Sichuan University,and Shanghai East Hospital,Tongji University School of Medicine,China.The trial plans to recruit 66 early chronic SCI patients.Eligible patients will undergo randomization at a 2:1 ratio to two arms:the observation group and the control group.Subjects in the observation group will receive four intrathecal transplantations of stem cells,with a dosage of 1×106/kg,at one calendar month intervals.Subjects in the control group will receive intrathecal administrations of 10 mL sterile normal saline in place of the stem cell transplantations.Clinical safety will be assessed by the analysis of adverse events and laboratory tests.The American Spinal Injury Association(ASIA)total score will be the primary efficacy endpoint,and the secondary efficacy outcomes will be the following:ASIA impairment scale,International Association of Neural Restoration-Spinal Cord Injury Functional Rating Scale,muscle tension,electromyogram,cortical motor and cortical sensory evoked potentials,residual urine volume,magnetic resonance imaging–diffusion tensor imaging,T cell subtypes in serum,neurotrophic factors and inflammatory factors in both serum and cerebrospinal fluid.All evaluations will be performed at 1,3,6,and 12 months following the final intrathecal administration.During the entire study procedure,all adverse events will be reported as soon as they are noted.This trial is designed to evaluate the clinical safety and efficacy of subarachnoid transplantation of hUC-MSCs to treat early chronic SCI.Moreover,it will establish whether cytotherapy can ameliorate local hostile microenvironments,promote tracking fiber regeneration,and strengthen spinal conduction ability,thus improving overall motor,sensory,and micturition/defecation function in patients with early chronic SCI.This study was approved by the Stem Cell Research Ethics Committee of the Third Affiliated Hospital of Sun Yat-sen University,China(approval No.[2018]-02)on March 30,2018,and was registered with ClinicalTrials.gov(registration No.NCT03521323)on April 12,2018.The revised trial protocol(protocol version 4.0)was approved by the Stem Cell Research Ethics Committee of the Third Affiliated Hospital of Sun Yat-sen University,China(approval No.[2019]-10)on February 25,2019,and released on ClinicalTrials.gov on April 29,2019.

Tailoring MgH_(2) for hydrogen storage through nanoengineering and catalysis

Hydrogen energy has been recognized as “Ultimate Power Source” in the 21st century, which could be the best solution to the looming energy crisis and climate degeneration in the near future. Due to its high safety, low price, abundant resources and decent hydrogen storage density, magnesium based solid-state hydrogen storage materials are becoming the leading candidate for onboard hydrogen storage. However,the high operation temperature and slow reaction rate of MgH_(2), as a result of the large formation enthalpy and high reaction activation energy,respectively, are the first and most difficult problems we need to face and overcome to realize its industrialization. Herein, a state-of-the-art review on tailoring the stable thermodynamics and sluggish kinetics of hydrogen storage in MgH_(2), particularly through nanoengnieering and catalysis is presented, aiming to provide references and solutions for its promotion and application. Promising methods to overcome the challenges faced by MgH_(2)/Mg, such as bidirectional catalysts and nanoconfinement with in-situ catalysis are compared and the required improvements are discussed to stimulate further discussions and ideas in the rational design of MgH_(2)/Mg systems with ability for hydrogen release/uptake at lower temperatures and cycle stability in the near future.

High heat loading performance of actively cooled W/Cu FGM-based components

A functionally graded material-based actively water-cooled tungsten-copper mockup with a dimension of 30 mm×30 mm×25 mm was designed and fabricated by infiltration-brazing method.The thicknesses of the pure W layer and W/Cu graded layer were 2 and 3 mm,respectively.High heat flux tests were performed on the mockup using an e-beam device.There is no damage occurring on the joint after heat loading at 5 MW/m2.The temperature on the pure W surface is less than 500°C after irradiation for 100 s at 5 MW/m2,while the temperature on the brazing seam/copper surface is around 200°C.

Facile synthesis of a Ni_(3)S_(2)@C composite using cation exchange resin as an efficient catalyst to improve the kinetic properties of MgH_(2)

Carbon materials have excellent catalytic effects on the hydrogen storage performance of MgH2. Here, carbon-supported Ni3S2(denoted as Ni3S2@C) was synthesized by a facile chemical route using ion exchange resin and nickel acetate tetrahydrate as raw materials and then introduced to improve the hydrogen storage properties of MgH2. The results indicated the addition of 10 wt.% Ni3S2@C prepared by macroporous ion exchange resin can effectively improve the hydrogenation/dehydrogenation kinetic properties of MgH2. At 100 ℃,the dehydrogenated MgH2-Ni3S2@C-4 composite could absorb 5.68 wt.% H2. Additionally, the rehydrogenated MgH2-Ni3S2@C-4 sample could release 6.35 wt.% H2at 275 ℃. The dehydrogenation/hydrogenation enthalpy changes of MgH2-Ni3S2@C-4 were calculated to be 78.5 k J mol-1/-74.7 k J mol-1, i.e., 11.0 k J mol-1/7.3 k J mol-1lower than those of MgH2. The improvement in the kinetic properties of MgH2was ascribed to the multi-phase catalytic action of C, Mg2Ni, and Mg S, which were formed by the reaction between Ni3S2contained in the Ni3S2@C catalyst and Mg during the first hydrogen absorption–desorption process.

Cortical bone trajectory screws in the treatment of lumbar degenerative disc disease in patients with osteoporosis

Lumbar degenerative disc disease(DDD)in the elderly population remains a global health problem,especially in patients with osteoporosis.Osteoporosis in the elderly can cause failure of internal fixation.Cortical bone trajectory(CBT)is an effective,safe and minimally invasive technique for the treatment of lumbar DDD in patients with osteoporosis.In this review,we analyzed the anatomy,biomechanics,and advantages of the CBT technique in lumbar DDD and revision surgery.Additionally,the clinical trials and case reports,indications,advancements and limitations of this technique were further discussed and reviewed.Finally,we concluded that the CBT technique can be a practical,effective and safe alternative to traditional pedicle screw fixation,especially in DDD patients with osteoporosis.

Mechanical and corrosion properties of Ti-35Nb-7Zr-xHA composites fabricated by spark plasma sintering

To improve the bioactivity of Ti?Nb?Zr alloy,Ti?35Nb?7Zr?xHA(hydroxyapatite,x=5,10,15and20,mass fraction,%)composites were fabricated by spark plasma sintering.The effects of the HA content on microstructure,mechanical and corrosionproperties of the composites were investigated utilizing X-ray diffraction(XRD),scanning electron microscope(SEM),mechanicaltests and electrochemical tests.Results show that all sintered composites are mainly composed ofβ-Ti matrix,α-Ti andmetal?ceramic phases(CaO,CaTiO3,CaZrO3,TixPy,etc).Besides,some residual hydroxyapatites emerge in the composites(15%and20%HA).The compressive strengths of the composites are over1400MPa and the elastic moduli of composites((5%?15%)HA)present appropriate values(46?52GPa)close to that of human bones.The composite with15%HA exhibits low corrosion currentdensity and passive current density in Hank's solution by electrochemical test,indicating good corrosion properties.Therefore,Ti?35Nb?7Zr?15HA composite might be an alternative material for orthopedic implant applications.

Development of Selenium-rich Passion Fruit Industry in Guangxi

According to the understanding of current situation of Guangxi selenium-containing passion fruit products and the advantages and disadvantages of related product markets,the corresponding improvement plans were proposed for the supply and demand of products and the adjustment of industrial development,so as to provide theoretical data support for optimizing the industrial structure and increasing the market share of selenium-rich passion fruit in Guangxi.