颗粒材料破碎行为数值分析方法研究综述

颗粒材料在自然界和工程领域普遍存在,外载荷作用下颗粒可能发生破碎现象.颗粒材料的破碎行为会引起其物理力学性质的变化,给工程和建筑建设带来极大影响.研究宏、细观尺度下颗粒材料的破碎行为不仅可以揭示颗粒破碎的力学机理,还对工程领域的安全和正常进行提供保障.因此,分析颗粒破碎过程既具有实际工程意义,又有理论研究价值.文章综述了颗粒破碎行为研究的数值分析方法,在基于离散元法理论的数值方法中,介绍了黏结-破碎法和碎片替代法;在基于离散元-有限元耦合算法的方法中,介绍了比例边界有限元法、组合有限元-离散元法和内聚力模型;此外还详细介绍了近场动力学方法.文章主要梳理并讨论了以上数值方法的提出、实现过程、发展、关键问题、优势以及这些方法的不足之处.此外,针对每一种数值方法回顾了国内外的研究成果以及在工程中的主要应用,对每种方法重点关注的问题进行了介绍.最后对目前关于颗粒破碎的数值研究进行总结,并对今后的发展方向进行简单的展望.

Functional prediction of tomato PLATZ family members and functional verification of Sl PLATZ17

PLATZ is a novel zinc finger DNA-binding protein that plays an important role in regulating plant growth and development and resisting abiotic stress.However,there has been very little research on the function of this family gene in tomatoes,which limits its application in germplasm resource improvement.Therefore,the PLATZ gene family was identified and analyzed in tomato,and its roles were predicted and verified to provide a basis for in-depth research on SlPLATZ gene function.In this study,the PLATZ family members of tomato were identified in the whole genome,and 19 SlPLATZ genes were obtained.Functional prediction was conducted based on gene and promoter structure analysis and RNA-seq-based expression pattern analysis.SlPLATZ genes that responded significantly under different abiotic stresses or were significantly differentially expressed among multiple tissues were screened as functional gene resources.SlPLATZ17 was selected for functional verification by experiment-based analysis.The results showed that the downregulation of SlPLATZ17 gene expression reduced the drought and salt tolerance of tomato plants.Tomato plants overexpressing SlPLATZ17 had larger flower sizes and long,thin petals,adjacent petals were not connected at the base,and the stamen circumference was smaller.This study contributes to understanding the functions of the SlPLATZ family in tomato and provides a reference for functional gene screening.

Human circBOULE RNAs as potential biomarkers for sperm quality and male infertility

Reliable molecular biomarkers to predict fertility remain scarce.The current study investigated the potential of testis-specific circBOULE RNAs as biomarkers for male infertility and sperm quality.Using reverse transcription-PCR and real-time reverse transcription-PCR assays,we identified seven circular RNAs from the human BOULE gene in human sperm.We observed that the expression level of circEx3-6 was significantly reduced in asthenozoospermia,while the expression levels of both circEx2-6 and circEx2-7 were decreased in terato-zoospermia,compared with the controls.Furthermore,we demonstrated that the expression level of circEx2-6 was negatively correlated with the sperm DNA fragmentation index,and the expression level of circEx2-7 was correlated with both fertilization and cleavage rates in those treated with the assisted reproductive technologies.Further functional analyses in a transgenic fly model supported the roles of circBOULE RNAs in sperm development and human male fertility.Collectively,our findings support that sperm circBOULE RNAs may serve as diagnostic biomarkers for assessing sperm motility and DNA quality.Therefore,clinical application and significance of sperm circBOULE RNAs in the assisted reproductive technologies warrant further investigation.

Discrete Element Modelling of Damage Evolution of Concrete Considering Meso-Structure of ITZ

The mechanical properties of interfacial transition zones(ITZs)have traditionally been simplified by reducing the stiffness of cement in previous simulation methods.A novel approach based on the discrete element method(DEM)has been developed for modeling concrete.This new approach efficiently simulates the meso-structure of ITZs,accurately capturing their heterogeneous properties.Validation against established uniaxial compression experiments confirms the precision of thismodel.The proposedmodel canmodel the process of damage evolution containing cracks initiation,propagation and penetration.Under increasing loads,cracks within ITZs progressively accumulate,culminating in macroscopic fractures that traverse themortarmatrix,forming the complex,serpentine path of cracks.This study reveals four distinct displacement patterns:tensile compliant,tensile opposite,mixed tensile-shear,and shear opposite patterns,each indicative of different stages in concrete’s damage evolution.The widening angle of these patterns delineates the progression of cracks,with the tensile compliant pattern signaling the initial crack appearance and the shear opposite pattern indicating the concrete model’s ultimate failure.

Estimating heat capacities of liquid organic compounds based on elements and chemical bonds contribution

Molecular property depends on the property, the number of the elements, and the interaction between elements(such as chemical bonds). Based on the above-mentioned idea, two methods to estimate the isobaric heat capacity of liquids organic compounds were developed. Ten elements groups and 32 chemical bond groups were defined by considering the structure of organic compounds. The group contribution values and correlation parameters were regressed by the ridge regression method with the experiment data of 1137 compounds. The heat capacity can be calculated by summating the contributions of the elements and chemical bond groups. The two methods were compared with existing group contribution methods, such as Chickos, Zabransky-Ruzicka, and Zdenka Kolska. The results show that those new estimation methods' overall average relative deviations were 5.81% and 5.71%, which were lower than the other three methods. Those methods were more straightforward in compound splitting.Those new methods can be used to estimate the liquid heat capacity of silicon-containing compounds,which the other three methods cannot estimate. The new methods are more accessible, broader, and more accurate. Therefore, this research has important scientific significance and vast application prospects.

最大泡压法测定溶液表面张力实验条件的优化

最大气泡压力法测定溶液表面张力是物理化学实验中的一个传统实验,由于各种因素的影响,导致学生实验结果存在较大偏差。本研究通过浓度、温度等作为变量进行实验条件探索而得到的结果与文献值较为吻合。

Understanding the mechanisms of resistance to tomato leaf mold:A review

Tomato leaf mold is a common disease in tomato production and severely impacts the growth,fruit quality and yield of tomato plants.Research on tomato leaf mold has a long history and has focused mainly on the differentiation of pathogen races,the structure and function of pathogen Avr gene products,the cloning of Cf resistance genes and the analysis of disease resistance mechanisms.Interactions between Cf and Avr are in accordance with the"gene-for-gene"hypothesis and typical Cf/Avr interactions are part of effector-triggered immunity(ETI).However,an increasing number of studies have proven that pathogen-associated molecular pattern(PAMP)-triggered immunity(PTI)is involved in the disease resistance response system mediated by Cf genes.In addition,different Cf genes have both similar and different roles in the disease resistance response,indicating that the disease resistance mechanism of Cf genes is complex.In this paper,progress in tomato leaf mold research was reviewed,and the regulatory mechanism underlying the Cf-mediated disease resistance response was thoroughly explored.We hope this summary will lay a foundation for research on tomato leaf mold disease resistance mechanisms and is applicable to breeding for disease resistance.

Germination inhibitors detected in Sapium sebiferum seeds

This study identifies endogenous inhibitors of germination associated with seed dormancy in Sapium sebiferum,Chinese tallow.Seed extracts were separated into five distinct fractions(petroleum ether,ether,ethyl acetate,methanol,and aqueous)and tested for their effect on germination of cabbage seeds.There were no significant differences in germination percentages and germination index(GI)between the solvents and the control.The five fractions differentially reduced germination percentage and GI values of cabbage seeds.According to the GI results,the greatest inhibition was with the ether fraction followed by methanol,ethyl acetate,petroleum ether,and aqueous fractions.Gas chromatography–mass spectrometry identified the constituents of the four organic fractions.Compared with the mass spectrum of the National Institute of Standards and Technology library,a compound was confirmed,provided it was more than 85%similar.Analysis of ether extracts identified four compounds:butylated hydroxytoluene(BHT;19.7%),1,2-benzenediol(4.1%),phydroxycinnamic acid,ethyl ester(2.8%),and n-hexadecanoic acid(1.4%).Fourteen,20,and 9 compounds were identified in methanol,ethyl acetate,and petroleum ether extracts,respectively.The IC50 of BHT(the concentration at which BHT inhibits radicle growth by 50%)was 54.8 mg/L,indicating that the presence of BHT might be the primary cause of dormancy in S.sebiferum seeds.

Deep Learning Predicts Stress–Strain Relations of Granular Materials Based on Triaxial Testing Data

This study presents an AI-based constitutive modelling framework wherein the prediction model directly learns from triaxial testing data by combining discrete element modelling(DEM)and deep learning.A constitutive learning strategy is proposed based on the generally accepted frame-indifference assumption in constructing material constitutive models.The low-dimensional principal stress-strain sequence pairs,measured from discrete element modelling of triaxial testing,are used to train recurrent neural networks,and then the predicted principal stress sequence is augmented to other high-dimensional or general stress tensor via coordinate transformation.Through detailed hyperparameter investigations,it is found that long short-term memory(LSTM)and gated recurrent unit(GRU)networks have similar prediction performance in constitutive modelling problems,and both satisfactorily predict the stress responses of granular materials subjected to a given unseen strain path.Furthermore,the unique merits and ongoing challenges of data-driven constitutive models for granular materials are discussed.

Quantifying the effects of stripe rust disease on wheat canopy spectrum based on eliminating non-physiological stresses

The wheat canopy reflectance spectrum is affected by many internal and external factors such as diseases and growth stage. Separating the effects of disease stress on the crop from the observed mixed signals is crucial for increasing the precision of remote sensing monitoring of wheat stripe rust. The canopy spectrum of winter wheat infected by stripe rust was processed with the difference-in-differences(DID) algorithm used in econometrics. The monitoring accuracies of wheat stripe rust before and after processing with the DID algorithm were compared in the presence of various external factors, disease severity, and several simulated satellite sensors. The correlation between the normalized difference vegetation index processed by the DID algorithm(NDVI-DID) and the disease severity level(SL) increased in comparison with the NDVI before processing. The increase in precision in the natural disease area in the field in the presence of large differences in growth stage, growth, planting, and management of the crop was greater than that in the controlled experiment. For low disease levels(SL < 20%), the R2 of the regression of NDVI-DIDon SL was 38.8% higher than that of the NDVI and the root mean square error(RMSE) was reduced by 11.1%. The increase in precision was greater than that for the severe level(SL > 40%).According to the measured hyperspectral data, the spectral reflectance of three satellite sensor levels was simulated. The wide-band NDVI was calculated. Compared with the wide-band NDVI and vegetation indexes(VI) before DID processing, there were increases in the correlation between SL and the various types of VIS-DID, as well as in the correlation between SL and NDVI-DID. It is feasible to apply the DID algorithm to multispectral satellite data and diverse types of VISfor monitoring wheat stripe rust. Our results improve the quantification of independent effects of stripe rust infection on canopy reflectance spectrum,increase the precision of remote sensing monitoring of wheat stripe rust, and provide a reference for remote sensing monitoring of other crop diseases.

Amending Research on the Expression of the Contact Force of the Spindle Barrel Finishing Based on EDEM Simulation

The spindle barrel finishing is commonly used to improve the surface integrity of the important parts of the high-end equipment while it is difficult to provide enough test artifacts for the traditional trial and error experiment to obtain the desirable processing technology.The EDEM simulation of the spindle barrel finishing can provide effective help for the process design,however,the difference between the simulation and experiment is closely related to the selection of the contact model during simulation.In this paper,simulations and experiments are conducted based on the identical apparatus and conditions to facilitate the comparison and validation between each other.Based on the Hertz contact theory,the effect of the material properties of contact objects and the relative position of the workpiece on the contact force is qualified.The expression of the correlation coefficient of the contact model is deduced.Then the formula for calculating the contact force between the barrel finishing abrasive and the workpiece that includes influence coefficient of the material properties and the relative positions is established.Finally,the contact force calculation formula is verified by changing the rotating speed.The result shows that the material correction coefficient ranges from 1.41 to 2.38,which is inversely related to the equivalent modulus E.The position correction coefficient ranges from 2.0 to 2.3.The relative error value between the calculation result and the experimental test result is from 0.58%to 14.07%.This research lay a theoretical foundation for the correction theory of the core elements of the spindle barrel finishing process.

Virus-induced gene silencing of SlPYL4 decreases the drought tolerance of tomato

The abscisic acid(ABA)receptor PYR/PYL/RCAR,located upstream of the ABA signaling pathway,recognizes ABA signals and initiates the primary process of signal transduction.In our previous study,we found that the PYL4 gene in tomato plants was significantly upregulated after exogenous treatment with the hormone ABA.The present study used virus-induced gene silencing(VIGS)to further elucidate the role of the PYL4 gene in response to drought in tomato(Solanum lycopersicum)plants.Under the drought treatment,the SlPYL4-silenced plants wilted faster than the control plants did.Physiological indicators showed that the total reactive oxygen species(ROS)content and superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)activities of the SlPYL4-silenced plants were lower than those of the control plants after 3 and 6 h of drought stress treatment.After 3 h of drought treatment,hydrogen peroxide(H_(2)O_(2)) and superoxide anion(O_(2)^(−).)accumulatedmuch more in the leaves of the SlPYL4-silenced plants than in the leaves of the control plants.These results indicated that PYL4 plays a positive role in drought tolerance in tomato plants.Our results also suggest that SlPYL4 is located upstream of the ABA pathway to regulate the expression of PP2C,SnRK,and AREB/ABF genes.

Discrete Element Modelling of Dynamic Behaviour of Rockfills forResisting High Speed Projectile Penetration

This paper presents a convex polyhedral based discrete element method for modelling the dynamic behaviour ofrockfills for resisting high speed projectile penetration. The contact between two convex polyhedra is defined by theMinkowski overlap and determined by the GJK and EPA algorithm. The contact force is calculated by a Minkowskioverlap based normal model. The rotational motion of polyhedral particles is solved by employing a quaternionbased orientation representation scheme. The energy-conserving nature of the polyhedral DEM method ensures arobust and effective modelling of convex particle systems. The method is applied to simulate the dynamic behaviourof a rockfill system under impact of a high speed projectile. The rockfill sample is generated by a three-dimensionalVoronoi meso method with a specific particle size distribution. The penetrating process of the projectile strikingthe rockfill target is simulated. Some physical quantities associated with the projectile such as the residual velocity,penetration resistance, and deflection angle are monitored which can reflect the influence of the characteristics ofthe rockfill target on its anti-penetration performance. It can be concluded that the developed polyhedral DEMmethod is a very promising numerical approach in analysing the dynamic behaviour of rockfill systems subject tohigh speed projectile impact.

Combination of a crude oil-degrading bacterial consortium under the guidance of strain tolerance and a pilot-scale degradation test

Under the guidance of strain tolerance, a new combination method for crude oil-degrading bacterial consortium was studied. Firstly, more than 50 efficient crude oil-degrading and biosurfactant producing bacteria were isolated from petroleum-contaminated soil and water in Tianjin Binhai New Area Oil field, China. Twenty-four of them were selected for further study. These strains were identified as belonging Pseudornonas aeruginosa, Bacillus subtilis, Brevibacillus brevis, Achrornobacter sp., Acinetobacter venetianus, Lysinibacillus rnacroides, Klebsiella oxytoca, Stenotrophornonas rhizophila, Rhodococcus sp. and Bacillus thuringiensis. A shake-flask degradation test revealed that 12 of these strains could degrade over 50% of 1% crude oil concentration in 7 d. Of these, 8 strains were able to produce biosurfactants. Furthermore, environmental tolerance experiments indicated that the majority of the strains had the ability to adapt to extreme environments including high temperatures, alkaline en- vironments and high salinity environments. A mixed bacterial agent comprising the strains WB2, W2, W3 and HA was developed based on the environmental tolerance tests and subjected to the pilot-scale degradation test indicating that this bacterial agent could degrade 85.2% of 0.8% crude oil concentration in 60 d. Our results suggest that the application of this mixed agent could remediate crude oil polluted soils in saline and alkaline environments.

Nurses’experiences of caring for preterm infants in pain:A metaethnography

Objective:Preterm infants are subjected to numerous painful procedures during their neonatal intensive care unit(NICU)hospitalization.Despite advancements in pain alleviation,nurses remain challenged to provide timely and effective pain management for preterm infants.Greater understanding of the lived experience of nurses caring for preterm infants in pain could provide novel insights to improve pain management for this vulnerable population.The aim of this meta-ethnography was to synthesize and interpret qualitative findings of nurses’experiences of taking care of preterm infants in pain.Methods:An extensive literature search in PubMed,CINAHL,PsycINFO,Scopus,BIOSIS and ProQuest Dissertation and Theses Database was conducted,including studies within the past 10 years.Two nursing researchers conducted data extraction and analysis independently.Inclusion criteria were applied to search for qualitative studies of nurse participants who worked in the NICU taking care of preterm infants.Studies published in a language other than English,articles that did not include qualitative data and qualitative data that could not be extracted from the findings or did not discuss nurses’experiences were excluded.Critical Appraisal Skills Programme was used for literature quality evaluation.Results:Eight studies remained after further screening according to inclusion and exclusion criteria.These eight studies were conducted from 2013 to 2018 and totally enrolled 205 nurses from Iran,Canada,the United States,Finland,Sweden,Switzerland,and Australia.Five themes emerged on the nurses’perspectives of taking care of preterm infants in pain:1)They sense the neonatal pain;2)Adverse consequences of unrelieved pain;3)Barriers of managing pain;4)Concerns of available approaches for pain relief;5)Failure to work with parents.Conclusions:This meta-ethnography identified nurses’understanding of pain in preterm infants that can be assessed,and they acknowledged that unrelieved pain could cause developmental deficits in infants.The barriers are lack of training and support on pain assessment and intervention in preterm infants.Optimizing workload and environment,developing age-specified pain assessment and intervention,receiving emotional support and training,and building up a rapport with parents are urgent needs for nurses to provide better care to infants having pain.

Synthesis of ternary magnetic nanoparticles for enhanced catalytic conversion of biomass-derived methyl levulinate into γ-valerolactone

Conversion of levulinic acid and its esters into versatile y-valerolactone(GVL)is a pivotal and challenging step in biorefineries,limited by high catalyst cost,the use of hydrogen atmosphere,or tedious catalyst preparation and recycling process.Here we have successfully synthesized a ternary magnetic nanoparticle catalyst(Al_(2)O_(3)-ZrO_(2)/Fe_(3)O_(4)(5)),over which biomass-derived methyl levulinate(ML)can be quantitively converted to GVL with an extremely high selectivity of>99%and yield of-98%in the absence of molecular hydrogen.Al_(2)O_(3)-ZrO_(2)/Fe_(3)O_(4)(5)incorporates simultaneously inexpensive alumina and zirconia onto magnetite support by a facile coprecipitation method,giving rise to a core-shell structure,welldistributed acid-base sites,and strong magnetism,as evidenced by the X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM),transmission electron microscopy(TEM),high-angle annular dark-field scanning-TEM(HAADF-STEM),SEM-energy dispersive Xray spectroscopy(SEM-EDX),temperature-programmed desorption of ammonia(NH3-TPD),temperature-programmed desorption of carbon dioxide(CO_(2)-TPD),pyridine-adsorption infrared spectra(Py-IR),and vibrating sample magnetometry(VSM).Such characteristics enable it to be highly active and easily recycled by a magnet for at least five cycles with a slight loss of its catalytic activity,avoiding a time-consuming and energy-intensive reactivation process.It is found that there was a synergistic effect among the metal oxides,and the high efficiency and selectivity originating from such synergism are evidenced by kinetic studies.Furthermore,a reaction mechanism regarding the hydrogenation of ML to GVL is proposed by these findings,coupled with gas chromatography-mass spectrometry(GC-MS)analysis.Accordingly,this readily synthesized and recovered magnetic nanocatalyst for conversion of biomassderived ML into GVL can provide an eco-friendly and safe way for biomass valorization.

Comparison of Coarse Graining DEM Models Based on Exact Scaling Laws

The simulation of a large number of particles requires unacceptable computational time that is the most criticalproblem existing in the industrial application of the DEM. Coarse graining is a promising approach to facilitatethe application of DEM to industrial problems. While the current coarse graining framework is often developedin an ad-hoc manner, leading to different formulations and different solution accuracy and efficiency. Therefore,in this paper, existing coarse graining techniques have been carefully analysed by the exact scaling law which canprovide the theory basis for the upscaling method. A proper scaling rule for the size of particles and samples as wellas interaction laws have been proposed. The scaling rule is applied to a series simulations of biaxial compressiontests with different scale factors to investigate the precision of the coarse graining system. The error between theoriginal system and the coarse system shows a growing tendency as the scale factor increases. It can be concludedthat the precision of the coarse graining system is accepted when applying scaling rules based on the exact scalinglaws.

A newly recorded genus Caniatta Solovyev&Witt(Lepidoptera:Limacodidae)from China

The genus Caniatta Solovyev&Witt,2009,belonging to the family Limacodidae,is reported for the first time from Yunnan Province in China,with the redescription of the newly recorded species Caniatta levis Solovyev&Witt,2009.Illustrations of the adults and genitalia along with its distribution are provided.

RNA binding protein BOULE forms aggregates in mammalian testis

Amyloids have traditionally been considered pathologic protein aggregates which contribute to neurodegeneration.New evidence however increasingly suggests that non-pathological amyloids are formed in animals during normal development.Amyloid-like aggregate formation was originally thought to be a conserved feature of animal gametogenesis.This hypothesis was based on findings which suggest that regulated amyloid formations govern yeast meiosis by way of meiosis-specific RNA binding proteins.Additional support came from studies which demonstrate that DAZL,a mammalian gametogenesis-specific RNA binding protein,also forms SDS-resistant aggregates in vivo.Here,we report evidence of aggregated BOULE formations,another DAZ family protein,during sperm development.Data suggest that in mouse testis,BOULE forms SDS-resistant amyloid-like aggregates.BOULE aggregate formation correlates with dynamic developmental expression during spermatogenesis but disappeared in Boule knockout testis.We also mapped essential small region in vitro BOULE aggregations,immediately downstream DAZ repeats,and found that aggregations positively correlated with temperature.We also performed enhanced UV cross-linking immunoprecipitation on BOULE aggregates from mouse testes and found that aggregates bind with a large number of spermatogenesis-related mRNAs.These findings provide insight into the amyloidogenic properties of gametogenesis-specific RNA binding proteins as a conserved feature in mammalian reproduction.Further investigation is warranted to understand the functional significance of BOULE amyloid-like formation during mouse spermatogenesis.

Prediction of candidate small non-coding RNAs inAgrobacterium by computational analysis

Small non-coding RNAs with important regulatory roles are not confined to eukaryotes. Recent work has uncovered a growing number of bacterial small RNAs （sRNAs）, some of which have been shown to regulate critical cellular processes. Computational approaches, in combination with molecular experiments, have played an important role in the identification of these sRNAs. At present, there is no information on the presence of small non-coding RNAs and their genes in the Agrobacterium tumefaciens genome. To identify potential sRNAs in this important bacterium, deep sequencing of the short RNA populations isolated from Agrobacterium tumefaciens C58 was carried out. From a data set of more than 10,000 short sequences, 16 candidate sRNAs have been tentatively identified based on computational analysis. All of these candidates can form stem-loop structures by RNA folding predictions and the majority of the secondary structures are rich in GC base-pairs：：Some are followed by a short stretch of U residues, indicative of a rho-independent transcription terminator, whereas some of the short RNAs are found in the stem region of the hairpin, indicative of eukaryotic-like sRNAs. Experimental strategies will need to be used to verify these candidates. The study of an expanded list of candidate sRNAs in Agrobacterium will allow a more complete understanding of the range of roles played by regulatory RNAs in prokaryotes.