Natural aging mechanism of buried polyethylene pipelines during long-term service

Currently,accelerated aging tests are widely used to study the aging process of polyethylene pipelines.However,this approach can only simulate one or several main influencing factors in the natural environment,which are often quite different from the actual environment of the buried pipelines.In this study,five types of PE80 buried pipelines in service for 9e18 years were taken as the research object,while new PE80 pipelines were taken as the reference group.The aging process and mechanism of polyethylene buried pipelines were studied through mechanical and chemical property tests and microstructural analysis.The results showed that the pipeline exhibited cross-linking as the main aging mechanism after being in service for 0e18 years.The aging degree and law of the inner and outer surface of the pipeline were compared,and the observed mechanism of both surfaces was explained.After 18 years in service,the elongation at the break of the pipe decreased by 16.2%,and the toughness of the matrix in the main collapse area of the tensile sample was the fundamental reason responsible for changes in the mechanical properties.Finally,after 18 years in service,the oxidation induction time of the pipeline was 25.7 min,which was 28.5% higher than the national standard value.There were no potential safety hazards during continuous long-term service.The results of this paper provide reference data and theoretical guidance for the aging process study of buried polyethylene pipelines.

Formation and characterization of metallic iron grains in coal-based reduction of oolitic iron ore

To reveal the formation and characteristics of metallic iron grains in coal-based reduction, oolitic iron ore was isothermally re- duced in various reduction times at various reduction temperatures. The microstructure and size of the metallic iron phase were investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and a Bgrimm process mineralogy analyzer. In the results, the re- duced Fe separates from the ore and forms metallic iron protuberances, and then the subsequent reduced Fe diffuses to the protuberances and grows into metallic iron grains. Most of the metallic iron grains exist in the quasi-spherical shape and inlaid in the slag matrix. The cumula- tive frequency of metallic iron grain size is markedly influenced by both reduction time and temperature. With increasing reduction temperature and time, the grain size of metallic iron obviously increases. According to the classical grain growth equation, the growth kinetic parameters, i.e., time exponent, growth activation energy, and pre-exponential constant, are estimated to be 1.3759 ± 0.0374, 103.18 kJ·mol^-1, and 922.05, respec- tively. Using these calculated parameters, a growth model is established to describe the growth behavior of metallic iron grains.

Migration behaviors and kinetics of phosphorus during coal-based reduction of high-phosphorus oolitic iron ore

To understand the migration mechanisms of phosphorus(P)during coal-based reduction,a high-phosphorus oolitic iron ore was reduced by coal under various experimental conditions.The migration characteristics and kinetics of P were investigated by a field-emission electron probe microanalyzer(FE-EPMA)and using the basic principle of solid phase mass transfer,respectively.Experimental results showed that the P transferred from the slag to the metallic phase during reduction,and the migration process could be divided into three stages:phosphorus diffusing from the slag to the metallic interface,the formation of Fe P compounds at the slag metal interface and P diffusing from the slag metal interface to the metallic interior.The reduction time and temperature significantly influenced the phosphorus content of the metallic and slag phases.The P content of the metallic phase increased with increasing reduction time and temperature,while that of the slag phase gradually decreased.The P diffusion constant and activation energy were determined and a migration kinetics model of P in coal-based reduction was proposed.P diffusion in the metallic phase was the controlling step of the P migration.

Fatigue Life Prediction of Rolling Bearings Based on Modified SWT Mean Stress Correction

The existing engineering empirical life analysis models are not capable of considering the constitutive behavior of materials under contact loads;as a consequence,these methods may not be accurate to predict fatigue lives of roll-ing bearings.In addition,the contact stress of bearing in operation is cyclically pulsating,it also means that the bear-ing undergo non-symmetrical fatigue loadings.Since the mean stress has great effects on fatigue life,in this work,a novel fatigue life prediction model based on the modified SWT mean stress correction is proposed as a basis of which to estimate the fatigue life of rolling bearings,in which,takes sensitivity of materials and mean stress into account.A compensation factor is introduced to overcome the inaccurate predictions resulted from the Smith,Watson,and Topper(SWT)model that considers the mean stress effect and sensitivity while assuming the sensitivity coefficient of all materials to be 0.5.Moreover,the validation of the model is finalized by several practical experimental data and the comparison to the conventional SWT model.The results show the better performance of the proposed model,especially in the accuracy than the existing SWT model.This research will shed light on a new direction for predicting the fatigue life of rolling bearings.

CLINICAL AND GENETIC ANALYSIS OF THREE FAMILIES WITH FAMILIAR AMYLOID POLYNEUROPATHY

Objective To study the clinical and genetic features of familiar amyloid polyneuropathy (FAP). Methods Three families of suspected FAP in China mainland and Macao were investigated on aspects of clinical manifestations, histological features, and gene analysis. Results All the 3 families had the clinical features of sensory and motor polyneuropathies, and notable vegetative nerve involvements. Affected cases of one family had ultrasound proved cardiomyopathy. Histological studies showed amyloid deposition in all the biopsy tissues of the affected cases of the 3 families, and anti-transthyretin antisera staining was positive in 3 cases of one family. Gene analysis confirmed that mutation types were amyloidogenic transthyretin (ATTR) Val30Met, Phe33Val, and Gly67Glu in the 3 families respectively. The ATTR Gly67Glu family had a shorter survival time due to the heart involvement compared with the other 2 families. Conclusion FAP is an autosomal dominant inherited disease, with its clinical manifestations related to the type of genetic mutation.

STUDY ON THE IMMOBILIZATION OF PAPAIN WITH A MACROPOROUS BEAD CARRIER OF COPOLYMER CONTAINING MONOMER UNITS OF NAMINOETHYL ACRYLAMIDE AND VINYL ALCOHOI

A kind of macroporous bead carrier of copolymer containing monomer units of N-aminoethyl acrylamide and vinylalcohol was synthesized, i.e. the MR-AA carrier. Papain was immobilized on the carrier using glutaraldehyde as the couplingagent. The enzymatic activity of the immobilized papain was compared with free papain using casein as a substrate, and theeffects of glutaraldehyde concentration, pH, temperature, time and papain amount added on the activity recovery were alsoinvestigated. The results show that the MR-AA carrier contains reactive primary amine groups, hydrophilic amido links andhydroxyl groups, as well as macroporous structures based on its matrix (MR-AV matrix), furthermore, the activity recoveryof papain in the immobilization could reach 48%/～58%. In comparison with free papain, the resulting immobilized papainexhibits a remarkable thermostability and better reusability.

CABYR binds to AKAP3 and Ropporin in the human sperm fibrous sheath

Calcium-binding tyrosine phosphorylation-regulated protein （CABYR） is a highly polymorphic calcium-binding tyrosine- and serine-/threonine-phosphorylated fibrous sheath （FS） protein involved in capacitation. A putative domain （amino acids 12-48） homologous to the regulatory subunit of type II cAMP-dependent protein kinase A （RII） dimerisation and A kinase-anchoring protein （AKAP）-binding domains of protein kinase A at the N-terminus suggests that CABYR may self-assemble and bind to AKAPs. Moreover, there is evidence that CABYR has limited interaction with AKAPs. However, further evidence and new relationships between CABYR and other FS proteins, including AKAPs, will be helpful in understanding the basic physiology of FS. In this study, a new strategy for co-immunoprecipitation of insoluble proteins, as well as the standard co-immunoprecipitation method in combination with mass spectrometry and western blot, was employed to explore the relationship between CABYR, AKAP3 and Ropperin. The results showed that AKAP3 was co.immunoprecipitated with CABYR by the anti-CABYR-A polyclonal antibody, and, conversely, CABYR was also co.immunoprecipitated with AKAP3 by the anti-AKAP3 polyclonal antibody. Another RIl-like domain containing protein, Ropporin, was also co-immunoprecipitated with CABYR, indicating that Ropporin is one of CABYR＇s binding partners. The interactions between CABYR, AKAP3 and Ropporin were confirmed by yeast two-hybrid assays. Further analysis showed that CABYR not only binds to AKAP3 by its RII domain but binds to Ropporin through other regions besides the RIl-like domain. This is the first demonstration that CABYR variants form a complex not only with the scaffolding protein AKAP3 but also with another Rll-like domain-containing protein in the human sperm FS.

Optimal design of sintered Ce_9Nd_(21)Fe_(bal)B_1 magnets with a low-melting-point (Ce,Nd)-rich phase

A systemic investigation was done on the chemistry and crystal structure of boundary phases in sintered Ce9Nd21FebalB1 （wt%） magnets. Ce2Fe14B is believed to be more soluble in the rare-earth （RE）-rich liquid phase during the sintering process. Thus, the grain size and oxygen content were controlled via low-temperature sintering, resulting in high coercivity and maximum energy products. In addition, Ce formed massive agglomerations at the triple-point junctions, as confirmed by elemental mapping results. Transmission electron micros- copy （TEM） images indicated the presence of （Ce,Nd）Ox phases at grain boundaries. By controlling the composition and optimizing the preparation process, we successfully obtained Ce9Nd21FebalBx sintered magnets; the prepared magnets exhibited a residual induction, coerciv- ity, and energy product of 1.353 T, 759 kA/m, and 342 kJ/m3, respectively.

Study on element detection and its correction in iron ore concentrate based on a prompt gamma-neutron activation analysis system

A prompt gamma-neutron activation analysis(PGNAA) system was developed to detect the iron content of iron ore concentrate. Because of the self-absorption effect of gamma-rays and neutrons, and the interference of chlorine in the neutron field, the linear relationship between the iron analytical coefficient and total iron content was poor, increasing the error in the quantitative analysis. To solve this problem, gamma-ray self-absorption compensation and a neutron field correction algorithm were proposed, and the experimental results have been corrected using this algorithm. The results show that the linear relationship between the iron analytical coefficient and total iron content was considerably improved after the correction. The linear correlation coefficients reached 0.99 or more.

Cerebrospinal Fluid Biomarkers in Dementia Patients with Cerebral Amyloid Angiopathy

Objective To study the changes of biomarkers in cerebrospinal fluid(CSF) in cerebral amyloid angiopathy(CAA) dementia and Alzheimer's disease.Methods Levels of amyloid protein β(Aβ42,Aβ40) and phosphorylated Tau-protein(P-tau) in CSF and ratio of Aβ42/Aβ40 were tested in 5 cases with CAA dementia and 20 cases with Alzheimer's disease collected at Peking Union Medical College Hospital from December 2001 to March 2011.Results The levels of Aβ42,Aβ40,and P-tau in CSF and ratio of Aβ42/Aβ40 were(660.4±265.2) ng/L,(7111.0±1033.4) ng/L,(71.8±51.5) ng/L,and 0.077±0.033,respectively in CAA dementia and(663.6±365.6) ng/L,(5115.0±2931.1) ng/L,(47.7±38.8) ng/L,and 0.192±0.140,respectively in Alzheimer's disease patients.There were no statistically significant differences between CAA dementia and Alzheimer's disease in terms of these CSF biomarkers(all P>0.05).Conclusion Measurements of CSF biomarkers may not be helpful in differential diagnosis of CAA and Alzheimer's disease.

Optimization of PGNAA device and algorithm for testing basicity index of sinter mixture

Sinter is the main raw material in the blast furnace iron-making process,and basicity(CaO/SiO2)is an important quality index of sinter.Prompt gamma neutron activation analysis is a multi-elemental online detection technology that has been successfully applied in cement,coal,etc.Compared with cement as a raw material,sinter exhibits poor moderation ability and a large neutron absorption cross section.Therefore,cement detection devices are not suitable for sinter mixture detection.In this study,a prompt gamma neutron activation analysis equipment used for testing cement was re-optimized to render it suitable for measuring a sinter mixture.Using Monte Carlo simulation,the comprehensive detection efficiency of the detection device improved by 71.52%.Because of the gamma-ray self-shielding effect of the sinter mixture,the detection errors of CaO and SiO2 are significant.By applying the gamma-ray self-shielding correction algorithm,the detection accuracies improved,and their linear correlation coefficients R2 exceeded 0.99.Furthermore,by applying an improved analyzer to a sintering plant,the first-grade product rate of the factory increased by 4.64%.

HETEROAROMATIC POLYMERS—HIGH TEMPERATURE POLYPYRROLONES DERIVED FROM 2,6-BIS(3',4'-DIAMINOPHENYL)-4-BIPHENYLPYRIDINE AND VARIOUS AROMATIC DIANHYDRIDES

A new type of aromatic tetraarnine containing biphenyl moiety in the side chain was synthesized via a modified Chichibabin＇s reaction. 3-Nitro-4-acetamidoacetophenone was reacted with 4-phenyl benzaldehyde in the presence of ammonium acetate to obtain 2,6-bis（3＇,4＇-diaminophenyl）-4-biphenyl pyridine （DPPA）. A series of polypyrrolones （PPys） were prepared using tetraamine and various aromatic dianhydrides via a two-step cyclization procedure. All the PPys show excellent high temperature stabilities with the initial decomposition temperatures of 530-549℃ and residual weight ratio of 49%-80% at 750℃ in nitrogen. The polymers exhibit no apparent glass transition temperatures （Tgs） except PPy-1 （Tg= 327℃）, which is derived from tetraamine DPPA and 2,2-bis[4-（3＇,4＇-dicarboxyphenoxy）-phenyl]propane dianhydride （BPADA）. In addition, the polymers have acceptable mechanical properties with the tensile strength of 65-94 MPa. The PPy films show excellent hydrolysis-resistance in alkaline aqueous medium and could maintain most of the properties even after boiling in 10% aqueous sodium hydroxide solution for a week.

Interface evolution of Cu-Ni-Si/Al-Mg-Si clad composite wires after annealing

Interface micros tructures of Cu-Ni-Si/Al-MgSi clad composite wires during isothermal annealing from 623 to 773 K were investigated.The composite wires were fabricated by a drawing process.The evolution of intermetallic compounds(IMCs)was analyzed.A continuous IMCs layer forms only after annealing for 1 min,which may be due to more IMCs nucleation points generated by deep drawing process.IMCs consist of Al_(4)Cu_(9),AlCu and Al_(2)Cu identified by energy-dispersive spectroscopy(EDS)and transmission electron microscopy(TEM).The growth activation energies of total IMCs,Al_(2)Cu,AlCu and Al_(4)Cu_(9),are 98.8,69.4,101.3 and 137.1 kJ·mol^(-1),respectively.The higher growth activation energy of Al_(4)Cu_(9)results in the higher growth rate under high temperature.However,the average interdiffusion coefficient for each IMC calculated by Wagner method shows that interdiffusion in Al_(2)Cu and AlCu is more active than that in Al_(4)Cu_(9).The higher growth rate of Al_(4)Cu_(9)may be caused by the long concentration range.

Microstructure and magnetic properties of anisotropic hot-deformed magnet of different magnetic particle sizes

In this paper, the magnetic Nd-Fe-B particles of different sizes were conducted under vacuum by the hot pressing, then cooled quickly to room temperature. Finally hot deformation was performed to get the anisotropy Nd-Fe- B magnet at a deformation rate of 70 % in the protection of argon atmosphere. NIM-2000 was used for the measurement of hysteresis loop of the samples. Meanwhile, scanning electron microscopy （SEM） was used to observe the surface morphology of the magnetic particles with different sizes and hot-deformed magnets, energy spectrum analyzer to analyze the composition of magnetic particles. The effect of magnetic particle sizes on the microstructure and magnetic properties of the hot-deformed anisotropic magnet was investigated. Anisotropic hot-deformed magnets produced from the maximum particle size of 200-350 μm have the highest magnetic properties of Br = 1.465 T, Hcj = 1,157 kA.m-1, （Bn）max = 425 kJ.m-3.

Relation between microstructure and magnetic properties of shock wave-compressed Nd-Fe-B magnets

The relationship between the microstructure and magnetic properties of Nd-Fe-B sintered magnet compressed by shock wave with 6.26 GPa≤p≤7.16 GPa was investigated.It reveals that Nd-Fe-B magnets show a demagnetization behavior after compressed by shock wave.The intergranular fracture is the main occurring phe-nomenon in the shock wave-compressed magnets.The coercivity of the shock wave-compressed Nd-Fe-B magnets could be recovered after repeating the annealing process.It suggests that only the morphology change just like the intergranular fracture occurs,and there is no structural change in the grain boundary phase in the shock wave-compressed magnet.Matrix phase grain interconnection,microcracks and pores,and alterant orientation relationship between matrix phase and grain boundaries phase are con-sidered as induced factors of demagnetization.

α_(2) phase precipitation behavior and tensile properties at room temperature and 650℃ in an(α+β) titanium alloy

The microstructure,room temperature and 650℃ tensile properties of an(α+β) titanium alloy were investigated after aging over a temperature range of 600-750℃ following solution treatment.The results exhibit that both aging temperature and aging time influence the precipitation behavior of α_(2) phase,and the size ofα_(2) phase affects the tensile properties.The growth speed ofα_(2) phase gets quicker with the aging temperature increasing under the same aging time.For a given aging temperature,the size of α_(2) phase gets larger when prolonging the aging time.There are significant improvements in yield and ultimate tensile strength at room temperature and 650 ℃ after aging at 600℃ for 2 h,but these values decrease with the size of α_(2) phase increasing.It is found that α_(2) phase,less than 7 nm,does not impair the roomtemperature ductility.However,when the size of α_(2) phase grows up from 7 to 15 nm,ductility decreases drastically.During 650 ℃ tensile process,with the particle size increasing from 3 to 15 nm,the interaction between moving dislocations and coherent particles changes from cutting mechanism to bypass mechanism.

Transcription factor YY1 is essential for iNKT cell development

Invariant natural killer T(iNKT)cells develop from CD4+CD8+double-positive(DP)thymocytes and express an invariant Vα14–Jα18 T-cell receptor(TCR)α-chain.Generation of these cells requires the prolonged survival of DP thymocytes to allow for Vα14–Jα18 gene rearrangements and strong TCR signaling to induce the expression of the iNKT lineage-specific transcription factor PLZF.Here,we report that the transcription factor Yin Yang 1(YY1)is essential for iNKT cell formation.Thymocytes lacking YY1 displayed a block in iNKT cell development at the earliest progenitor stage.YY1-deficient thymocytes underwent normal Vα14–Jα18 gene rearrangements,but exhibited impaired cell survival.Deletion of the apoptotic protein BIM failed to rescue the defect in iNKT cell generation.Chromatin immunoprecipitation and deep-sequencing experiments demonstrated that YY1 directly binds and activates the promoter of the Plzf gene.Thus,YY1 plays essential roles in iNKT cell development by coordinately regulating cell survival and PLZF expression.

Chinese expert consensus statement for diagnosis and treatment of dementia with Lewy bodies 2020

Dementia with Lewy bodies(DLB)is the second most common type of neurodegenerative dementia,and prone to misdiagnosis and missed diagnosis in the clinic.Based on the evidence about DLB.