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This paper aims to reveal the mechanical evolution and potential mechanism of Ultra-high Performance Concrete (UHPC) exposed to a complex temperature-variation environment typical of Liquefied Natural Gas storage tank. Herein, the effect of steel fiber geometries (straight and hooked-end) on flexural failure of UHPCs in the range of −170 °C ∼ 200 °C was studied, and dynamic fracture evolution during the loading process was tracked using acoustic emission (AE) test. Results indicated that the flexural strength of concrete specimen enhanced at −170 °C but diminished at 200 °C in the first cycle. For multiple cycles, its improved strength subsisted until the third cycle, after which gradually decreased. Moreover, the hooked-end fiber generally had superior strengthening and toughening effects than straight fiber, except for cryogenic temperature and third cycles tests. At cryogenic temperature, the freezing of pore moisture inside specimen enhanced the matrix strength and the interfacial bonding between the matrix and fibers. At elevated temperature, the thawing, diffusion and evaporation of moisture in concrete could induce matrix dehydration and weaken the bonding effect between interfaces. In varying exposure environments, the moisture migration would also undergo secondary hydration reactions with unreacted cement particles. Finally, using AE parameters to effectively record damage progression in UHPCs exposed to extreme temperatures was also highlighted. [ABSTRACT FROM AUTHOR]

• Combined therapy with DHA and cisplatin exerts synergistic anti-NSCLC activity through activating ROS-mediated ER stress, JNK and p38 MAPK signaling pathways both in vitro and vivo. • PTGS1 is identified as a potential novel target of DHA. Knockdown of PTGS1 enhanced DHA-induced cell death in NSCLC cells through stimulating ROS-mediated ER stress, JNK and p38 MAPK signaling pathways. Dihydroartemisinin (DHA) exerts an anti-tumor effect in multiple cancers, however, the molecular mechanism of DHA and whether DHA facilitates the anti-tumor efficacy of cisplatin in non-small cell lung cancer (NSCLC) are unclear. Here, we found that DHA potentiated the anti-tumor effects of cisplatin in NSCLC cells by stimulating reactive oxygen species (ROS)-mediated endoplasmic reticulum (ER) stress, C-Jun-amino-terminal kinase (JNK) and p38 MAPK signaling pathways both in vitro and in vivo. Of note, we demonstrated for the first time that DHA inhibits prostaglandin G/H synthase 1 (PTGS1) expression, resulting in enhanced ROS production. Importantly, silencing PTGS1 sensitized DHA-induced cell death by increasing ROS production and activating ER-stress, JNK and p38 MAPK signaling pathways. In summary, our findings provided new experimental basis and therapeutic prospect for the combined therapy with DHA and cisplatin in some NSCLC patients. [Display omitted] [ABSTRACT FROM AUTHOR]

Herein, a hierarchical cementitious calcium silicate hydrate (C-S-H) superstructure with high Young's modulus, super-low porosity, and low mass density is reported. It has a very high Young's modulus at 47.5 GPa, three times higher than our reference synthetic C-S-H. Its specific surface area is merely 0.4509 m2/g, two orders of magnitude smaller than our reference synthetic C-S-H and the most common construction materials. In addition, the skeletal density of this composite is 1.96 g/cm3, much lower than C-S-H and hardened cement paste. In a density-Young's modulus diagram, this composite is located at the intersection of metals, ceramics, and polymers, approaching the carbon fiber region, implying lightweight and stiff characteristics. The cryogenic stability is also evaluated. It shows a satisfying applicability potential for cryogenic engineering with stable pore structure and nanoscopic mechanical properties. We confirm that the assembly of hierarchical C-S-H superstructure requires both hydrophilic amide and anionic carboxylic groups. [ABSTRACT FROM AUTHOR]

Colorectal cancer (CRC) is the third most common cancer and leading cause of cancer related deaths worldwide. Despite recent advancements in surgical and molecular targeted therapies that improved the therapeutic efficacy in CRC, the 5 years survival rate of CRC patients still remains frustratingly poor. Accumulated evidences indicate that microRNAs (miRNAs) play a crucial role in the progression and metastasis of CRC. Dysregulated miRNAs are closely associated with cancerous phenotypes (e.g. enhanced proliferative and invasive ability, evasion of apoptosis, cell cycle aberration, and promotion of angiogenesis) by regulating their target genes. In this review, we provide an updated overview of tumor suppressive and oncogenic miRNAs, circulatory miRNAs, and the possible causes of dysregulated miRNAs in CRC. In addition, we discuss the important functions of miRNAs in drug resistance of CRC. [ABSTRACT FROM AUTHOR]

The premelted films between cement and ice observed at freezing temperatures play a role in the freeze-thaw damage of cement-based materials, as they play a role in cryo-suction. However, their properties are poorly understood. In this work, we unveil the dynamics and local structure of the premelted film using molecular simulations. Combining those results with a thermodynamic analytical derivation, we obtain a characteristic time of the cryo-suction process, which depends on temperature, the transport properties and thickness of the premelted film, and the pore geometry. Our calculations show that, down to about 230 K, cryo-suction occurs relatively fast at the pore scale and the hypothesis of local thermodynamic equilibrium used in most poromechanical models of freezing of cement-based materials is reasonable. A fragile-to-strong transition of water in the premelted films is witnessed at about 230 K. Below this temperature, the significant deceleration of water dynamics makes the cryo-suction significantly slower. [ABSTRACT FROM AUTHOR]

This paper investigates the scaling of the nanoscopic elastic and tensile failure properties of calcium-silicate-hydrate (C-S-H). We report a Zhurkov-like scaling behavior for disordered C-S-H of various compositions at cryogenic temperatures, using molecular dynamics simulations. To this end, we first propose a revised molecular construction route to generate C-S-H atomic configurations with varying compositions. Then, we investigate how the tensile behavior evolves with temperature, system size, and strain rate. Our simulation results show that tensile strength, Young's modulus, fracture energy, and fracture-process zone (FPZ) length, all follow a Zhurkov-like scaling law providing a general temperature-size-time equivalence. Such scaling laws make it possible to extrapolate molecular simulation results to larger length and/or time scales. Detailed analysis shows that the typical FPZ length of C-S-H is about 150 Å, and the maximum reduction of activation energy barriers for tensile failure is 0.497 and 0.446 eV for Ca/Si of 1.7 and 1.1, respectively. [ABSTRACT FROM AUTHOR]

Herein, we report a cryogenic attack study on C-A-S-H with bulk Ca/(Al + Si) = 0.84–1.75, Al/(Al + Si) = 0.1, 0.2. The C-A-S-H nanostructure variations are quantitively analyzed using thermogravimetric analysis, single-pulse 29Si, and 27Al MAS NMR. Observing the conversion of tetrahedral aluminates to octahedral ones in the absence of depolymerization, we confirm the presence of bridging octahedral aluminates in C-A-S-H chains. The consistency between the slight polymerization and the decrease of pentahedral aluminate fraction in low-Al C-A-S-H reveals the existence of interlayer pentahedral aluminate. The depolymerization in high-Al C-A-S-H is accompanied by conversion of pentahedral aluminate to octahedral aluminate, which confirms the presence of bridging pentahedral and interlayer octahedral aluminates. We further identify the complexes for each structural unit. Then, a DNA-code rule is proposed to describe C-A-S-H atomistic structure considering both bridging and interlayer aluminates. Finally, we propose a general structural-chemical formula for C-A-S-H. [ABSTRACT FROM AUTHOR]

Herein, the intrinsic nanomechanical transition of calcium-(alumino)silicate-hydrate (C-(A)-S-H) upon ultra-low temperature attack and the potential role of aluminum incorporation as a bottom-up enhancement strategy are investigated. C-(A)-S-H is experimentally synthesized using an efficient hydrothermal reaction, and statistical AFM-based indentation, nitrogen sorption, SEM, and AFM observations are carried out. Note that the C-A-S-H is clarified in more ordered topographic features than Al-free C-S-H. The nanomechanical measurements reveal that the ultra-low temperature attack provoked the nano-brittleness of C-(A)-S-H. Nevertheless, the nanomechanical degradation is seen for Al-free C-S-H only. This brittle transition is attributed to the rise of the high-density phase fraction, though the elastic moduli of its decomposed phases decrease. In comparison, the brittle transition of C-A-S-H is ascribed to the increasing elastic moduli of its decomposed phases. It is further proved that such transitions are irrelevant to the packing nature of gel grains but involved with the variation of their intrinsic nanomechanical natures since the gel pore systems remain stable under the ultra-low temperature attack. These results advance fundamental knowledge toward developing cryogenic stable cement-based materials from a bottom-up insight. [ABSTRACT FROM AUTHOR]

Low-carbon calcium (alumino)silicate hydrate (C-(A)-S-H) based composites (e.g., blended cement-based materials and alkali-activated materials) have broad application potential in ultra-low-temperature engineering areas. This study devotes to reveal the structural stability of C-(A)-S-H under ultra-low temperature attack (−170 °C) and evaluating the role of aluminum as a bottom-up enhancement strategy for C–S–H. The atomic structure, interlayer structure, internal basic building block structure, pore network, and micro-morphology were experimentally studied using 29Si MAS NMR, XRD, helium pycnometry, nitrogen adsorption, and SEM. These results indicate that an ultra-low temperature attack can deteriorate C-(A)-S-H structure, even though without the presence of bulk water, whereas the incorporation of aluminum positively stabilizes C-(A)-S-H structure. The silicate chains of Al-free C–S–H are ruptured with more defective vacant sites, which consequently initiates a decline in its d 002 interlayer space and the volume collapse of basic building blocks, further resulting in the formation of microcracks. In contrast, aluminosilicate chains of C-A-S-H are more stable and even polymerized with longer chain length, stabilizing the micro/mesostructure. An upscaling degradation route from the atomic scale to mesoscale was proposed, providing a multiscale view to understand the degradation of concrete composites upon ultra-low temperature attack. We also confirm that incorporating aluminum in the silicate chains is an effective bottom-up strategy to enhance the cryogenic stability of C-(A)-S-H. [ABSTRACT FROM AUTHOR]

Most vertebrates exhibit sexual dimorphisms in size, colour, behaviour, physiology and many others. The Chinese soft-shelled turtle (Pelodiscus sinensis) male individuals reach a larger size than females which produce significant economic implications in aquaculture. However, the mechanisms of sex determination and plastic patterns of sex differentiation in P. sinensis remain unclear. Here, comparative transcriptome analysis on male and female embryonic gonads prior to gonad formation and stages mediated gonadal differentiation of P. sinensis were performed to characterize the potential sex-related genes and their molecular pathways in P. sinensis. A total of 6369 differentially expressed genes (DEGs) were identified from day 9 and day 16 and assigned to 626 GO pathways and 161 KEGG signalling pathways, including ovarian steroidogenesis pathway, steroid hormone biosynthesis pathways, and the GnRH signalling pathway (P < 0.05). Moreover, protein interaction network analyses revealed that Akr1c3 , Sult2b1 , Sts , Cyp3a , Cyp1b1 , Sox30 and Lhx9 might be key candidate genes for sex differentiation in P. sinensis. These data provide a genomic rationale for the sex differentiation of P. sinensis and enrich the candidate gene pool for sex differentiation. [Display omitted] • A large number of DEGs were identified in the gonad of male and female P. sinensis embryos. • RNA-seq analysis showed that some enriched pathways were involved in the process of sex differentiation in P. sinensis. • We have identified some new candidate genes that are closely related to sex differentiation in P. sinensis. [ABSTRACT FROM AUTHOR]

Abstract: A cDNA encoding heat shock protein 70 of Trichinella spiralis (Ts-Hsp70) was identified by immunoscreening the adult T. spiralis cDNA library with rabbit antisera against T. spiralis adult extracts. The open reading frame of Ts-Hsp70 cDNA encoded a 623-amino acid peptide with a predicted molecular weight of 68.7kDa, which shares a high degree of sequence conservation with HSP70s from other parasites. Recombinant Ts-Hsp70 was expressed in Escherichia coli and purified with nickel column chromatography. Western blot analysis showed that recombinant Ts-Hsp70 could be recognized not only by trichinellosis patient sera, but also by T. spiralis-infected sera from rabbits, swine, and mice. Mice vaccinated with recombinant Ts-Hsp70 formulated with Freund''s adjuvant exhibited strong humoral immune responses indicated by high titer of IgG antibody and significant muscle larval reduction (37%) after being challenged with T. spiralis larvae. The present results indicate that Ts-Hsp70 is a possible candidate vaccine against T. spiralis infection. [Copyright &y& Elsevier]

The Asian yellow pond turtle (Mauremys mutica) displays temperature-dependent sex determination (TSD), in which incubation temperature during embryonic development determines the sexual fate of the individual. However, the mechanism of the sex determination/differentiation of Mauremys mutica remains a mystery. Here, we first analyzed the temperature-specific gonadal transcriptomes of Mauremys mutica prior to gonad formation and gonads during the thermosensitive period. We uncovered a list of candidates that respond to temperature stimuli enriched in several categories, such as heat shock protein family members dnajb6a , dnaja4 , hspa8 and hsp90aa1 , temperature sensor genes mmp17 and mmp28 , and putative novel temperature-responsive genes tmco6 , gria3 and eif3f. Notably, striking differences were identified in the expression profiles of genes underlying sexual development, such as tex15 , insr , igf1r , cirbp , esr1 , dmrt2 and Serpinh1. Moreover, we analyzed the similarity and divergence of the timecourse of gene expression among Mauremys mutica and two other reported TSD turtles (Trachemys scripta and Chrysemys picta). The shared genes revealed the common gonad-specific regulatory mechanisms existing in these three TSD turtles that initiate their sexual development. Therefore, our findings could provide basic data to elucidate the mechanisms of sex determination/differentiation of M. mutica , even contributing to further understanding of these mechanisms in other TSD turtles. [Display omitted] • A list of candidates genes that respond to temperature stimuli were identified in Mauremys mutica. • Striking differences were identified in the expression profiles of genes underlying sexual development of Mauremys mutica. • Eight shared genes associate with common gonad-specific regulatory mechanisms were identified in the three TSD turtles. [ABSTRACT FROM AUTHOR]

The crucial roles of miRNAs in regulating animal growth, development, and disease resistance have been extensively reported, but their roles in relation to the reproductive capacity of aquatic animals (numbers of eggs laid and hatchlings), especially reptiles, remain unclear. In this study, high-throughput sequencing technology was used to screen miRNAs related to reproductive capacity based on the construction of a cDNA library of ovaries from higher-fecundity (HF) and lower-fecundity (LF) M. mutica. The results showed that 15,767,494 (93.98%) and 14,137,621 (94.17%) high-quality reads were obtained from the HF and LF groups, respectively. We screened 131 miRNAs that were differentially expressed between the HF and LF groups, of which 78 were upregulated and 53 were downregulated compared with the M. mutica reference genome. GO and KEGG pathway enrichment analyses of the target genes of differentially expressed miRNAs revealed significant differences in the enrichment frequencies of genes associated with ATP binding and proteolysis between the HF and LF groups, while the tricarboxylic acid cycle, glucagon signaling pathway and vitamin B6 metabolic pathway were shown to potentially help determine reproductive capacity. Ten miRNAs were verified by qRT-PCR to confirm the reliability and accuracy of the sequencing results, and a miRNA-mRNA target gene interaction network was constructed. These results will further our understanding of the regulatory mechanism of miRNAs in regards to turtle reproductive capacity. [Display omitted] • 131 differentially expressed miRNAs were detected between higher fecundity group and lower fecundity group. • There were 10 differentially expressed miRNAs validated by using qRT-PCR. • A miRNA-mRNA target gene interaction network was constructed. [ABSTRACT FROM AUTHOR]

• The cryogenic attacks led to an increase in the adsorption energy of the first adsorbed layer on C-S-H. • The mesopore structure C-S-H with a higher Ca/Si ratio is better preserved under the impacts of the harshly cryogenic attack. • The ultramicropores and small supermicropores are more sensitive to the cryogenic attack than other larger micropores. • The harshly cryogenic attack has resulted in higher complexity and irregularity of mesopores and macropores of C-S-H. This study carried out a comprehensive nitrogen adsorption evaluation on the cryogenic attack impacts on the micropores and mesopores of calcium-silicate-hydrate (C-S-H). Pore volume and pore size distribution were analyzed by using Barrett-Joyner-Halenda (BJH), non-local density function theory (NLDFT), Dubinin-Radushkevich (DR), and Horvath-Kawazoe (H-K) methods. Surface fractal dimensions were analyzed by Frenkel-Halsey-Hill (FHH) model. The tortuosity factors were estimated using the corrugated pore structure model (CPSM) simulation. Results show that the cryogenic attack may chemically transform C-S-H surface, leading to a higher attraction to the adsorbates. The mesopores of C-S-H with a high Ca/Si ratio were better preserved. Furthermore, the ultramicropores and small supermicropores are more sensitive to the cryogenic attack than those larger micropores. In addition, it is found that the cryogenic attack has a significant influence in increasing the complexity and irregularity of the C-S-H mesopore structure. The CPSM simulation results provide additional evidence for the microcrack formation. [ABSTRACT FROM AUTHOR]

Lung adenocarcinoma (LUAD) is the leading cause of cancer death worldwide, with high incidence and low survival rates. Nicotinic acetylcholine receptors play an important role in the progression of LUAD. In this study, a screening of 17 nicotinic acetylcholine receptor allosteric agents revealed that spinosad effectively suppressed the proliferation of LUAD cells. The experiments demonstrated that spinosad induced cell cycle arrest in the G1 phase and stimulated apoptosis, thereby impeding the growth of LUAD and enhancing the responsiveness to gefitinib in vitro and vivo. Mechanistic insights obtained through transcriptome sequencing, Co-IP, and protein immunoblots indicated that spinosad disrupted the interaction between CHRNA5 and EGFR, thereby inhibiting the formation of downstream complexes and activation of the EGFR signaling pathway. The supplementation of exogenous acetylcholine showed to mitigate the inhibition of LUAD cell proliferation induced by spinosad. This study elucidates the therapeutic effects and mechanisms of spinosad in LUAD, and offers a theoretical and experimental foundation for novel LUAD treatments. [ABSTRACT FROM AUTHOR]

• Analysis the parameters adjustment range of the traditional method. • A dual parameters method was proposed to expand the range. • The best parameters selection is obtained by particle swarm optimization. • Our method has better balance between accuracy and diversity. With the unprecedented development in the internet technology, the information overload issues have become more and more complex, resulting in users being unable to obtain the target information accurately and effectively in selecting the required information from a large pool of surfed data. In view of this a recommendation system can be used to predict the user's selection probability for different potential objects as an important tool, which can help to solve the information overload issues. So far, many personalized recommendation algorithms based on bipartite graphS have been proposed, most of which are based on the similarity degree among users or items, such as collaborative filtering (CF), mass diffusion (MD) and heat conduction (HC). Among many recommendation algorithms, the performances of algorithms are varied. MD algorithm has high recommendation accuracy but poor diversity, while HC algorithm has good diversity but low accuracy. In order to solve the dilemma in accuracy and diversity, some hybrid recommendation algorithm have been proposed. This paper has mainly focused on the hybrid recommendation algorithm HHM, and pointed out its shortcomings. Based on the reconsideration of the effect of item popularity in the recommendation process, an improved hybrid recommendation algorithm using dual parameter called IHM was proposed. The particle swarm optimization (PSO) algorithm was applied to the parameter optimal of the hybrid recommendation algorithm to obtain the parameters of the algorithm. Experiments on 3 real datasets indicated that the IHM algorithm is better than HHM algorithms in terms of the recommendation accuracy, diversity and novelty. Meanwhile, the IHM algorithm can also improve the recommendation for items with lower popularity and solve the cold start problem. [ABSTRACT FROM AUTHOR]

• The phyllosphere microflora community changed rapidly during freeze–thaw period. • The bacterial communities mainly responded to changes of environmental factors, whereas the fungal communities were affected by both environmental factors and litter quality factors. • The bacterial communities were similar between woody litter and herbaceous litter, whereas the fungal communities differed obviously. Litter decomposition plays an important role in the nutrient cycle of terrestrial ecosystems. The alpine wetland has a high litter accumulation rate and a slow degradation rate, which is extremely sensitive to changeable freeze–thaw patterns against the background of global climate change. Freeze-thaw process is a common natural phenomenon in middle-high latitudes and high altitudes. Hydrothermal changes caused by freezing and thawing process affect the survival and physiological characteristics of microorganisms, and then affect the decomposition process of litters. The alpine wetland could be an ideal example for wetland in high altitude to study the mechanism of microbial community structure and function during litter composition during freeze–thaw process. Moreover, seldom has research in the whole process in the fields. The bacterial and fungal communities were analyzed in three different Carex litter decomposition stages—fresh, four-, and six-month—during the freeze–thaw period using 16/18S rDNA pyrosequencing. Phyllosphere microflora had identified rapid changes in the structure and function. Bacteria were mainly influenced by environmental factors (air temperature, soil moisture), and were significantly related to the degradation of litter lignin and the change of C/N ratio. Fungi were affected by both litter quality and environmental factors, and were significantly related to the degradation of cellulose and the change of C/N ratio. Moreover, phyllosphere organisms, including bacteria (Cryobacterium and Paracoccus members) and fungi (Mrakia , Mrakiella , and Naganishia), were replaced by communities with specific metabolic capabilities to adapt to each particular decomposition stage. Ilumatobacter and the fungal genera, Mycosphaerella and Athelia were characteristic of four-month-old litter samples, whereas Brevundimonas , Paracoccus and Nigrospora were characteristic of six-month-old litter samples. Our results suggest that the bacterial community structures of Carex and forest litter during initial decomposition stages may be similar but that their fungal community structures may differ substantially. [ABSTRACT FROM AUTHOR]

• Flexural strength and compressive strength of UHPC before and after cryogenic attack were studied. • Cryogenic damage variable of UHPC were investigated. • Fracture characteristics and micromorphology of UHPC were analyzed. As one of the most common extreme environments, cryogenic temperature will directly threaten the structural safety of normal service concrete, and engender the premature deterioration of the structure performance. In this paper, steel fiber, polypropylene fiber, and polyvinyl alcohol fiber were selected to prepared ultra-high-performance concrete (UHPC), and the effects of different fibers on flexural strength and compressive strength of UHPC subjected to cryogenic attack were investigated. The results indicated that the addition of steel fiber and PVA fiber improved the flexural strength and compressive strength of UHPC. After the cryogenic attack, the flexural strength of UHPC increased by 70.06% with the increase of length-to-diameter ratio of steel fiber, and the peak deflection increased from 0.501 mm ~ 0.919 mm to 0.609 mm ~ 1.302 mm. Conversely, the flexural strength of UHPC with PVA fiber and PP fiber decreased by 33.76% and 33.18%, respectively. The peak deflection of UHPC with PVA fiber decreased from 0.106 mm to 0.064 mm. When the length-to-diameter ratio of steel fiber was 65, UHPC reached the highest compressive strength of 173.06 MPa. The compressive strength of UHPC decreased after the cryogenic attack. PVA fiber and PP fiber absorbed a lot of water, which affected the cement hydration in UHPC, thus reducing the strength of UHPC. [ABSTRACT FROM AUTHOR]

The stability of C-S-H nanostructures with varying bulk CaO/SiO 2 (C/S) ratios under cryogenic attack (−170 °C) was experimentally studied by means of XRD, TG, SEM-EDS, 29Si MAS NMR, and FTIR. An efficient hydrothermal method was adopted to synthesize C-S-H by accelerating the thermodynamic equilibrium. The results show that the C-S-H atomic structure with a lower bulk C/S ratio is more stable under cryogenic attack. Ca2+ is more likely to leach out from C-S-H with a high C/S ratio. An increase in the bound water fraction was also observed in C/S1.5. At the atomic level, the number of interlayer Ca2+ per tetrahedral site in C/S1.5 significantly decreased from 0.201 to 0.083. The number of vacant bridging sites in C/S2.0 declined from 0.208 to 0.178, probably indicating a slight polymerization. Based on the deconvolution results of 29Si MAS NMR spectra, three reaction equations were proposed to characterize these observed variations. [ABSTRACT FROM AUTHOR]

• The elastic modulus of C-S-H decreased after cryogenic attack. • The volumetric stability of C-S-H grains under cryogenic attack was highly related to C/S ratio. • The cryogenic attack resulted in the collapse of the intraglobular pores of C-S-H basic building blocks. The cryogenic attack (−170 °C) degradation mechanisms to cement-based materials have not reached an overwhelming consensus. This work aimed to reveal the degradation role of cryogenic attack to the physical properties of calcium-silicate-hydrate (C-S-H) with varying CaO/SiO 2 (C/S) ratios. The topographic features, nanomechanical property, and volumetric stability of C-S-H grains and the basic building blocks were progressively investigated by atomic force microscopy (AFM), AFM-based indentation, nitrogen adsorption, and short-term helium inflow. The results revealed that the cryogenic attack could lead to degradation to C-S-H itself even without the presence of water. Firstly, the elastic moduli of individual C-S-H phases such as Low-Density (LD) C-S-H and High-Density C-S-H decreased, this nanoscale mechanical degradation was consistent with the macroscopic mechanical degradation of cement-based materials. Secondly, microcracks formed in C-S-H phases under the cryogenic attack. These destructive microcracks were likely to form inside or between C-S-H grains, which was dependent on C/S ratios. Thirdly, the cryogenic attack resulted in collapse of the intraglobular pores, leading to volume shrinkage of C-S-H basic building blocks, which initiates the formation of local defects and microcracks. [ABSTRACT FROM AUTHOR]

Alpine wetlands can function as carbon sinks because of their high soil organic content and low decomposition rates. However, the effects of alpine wetland succession on soil structure and soil organic carbon (SOC) stability have rarely been reported. The objective of this study was to investigate the effects of vegetation succession on soil aggregate distribution, bulk soil carbon, aggregate-associated C, and intra-aggregate C fraction in the Bayinbuluk alpine wetland. Research sites were selected in adjacent swamp (S), swampy meadow (SM), and meadow (M) locations. Five soil aggregate fractions (>5000, 2000–5000, 250–2000, 53–250 and <53 μm) were separated using a modified Yoder method. The light fraction organic carbon (LFOC), coarse/fine intra-aggregate particulate organic matter carbon (iPOM-C), and mineral-associated organic matter carbon (mSOM-C) were isolated from soil aggregates. In the wetland succession sequence, the mean weight diameter of soil aggregates increased (from 4.16 to 4.63 mm) from S to SM, and then decreased (from 4.63 to 3.23 mm) from SM to M. The bulk soil carbon content initially increased (from 93 to 129 mg kg−1) from S to SM, and then decreased (from 129 to 54 mg kg−1) from SM to M. The same trends were found for the aggregate-associated C in different size aggregates. The coarse iPOM-C content (88–133 mg kg−1) was higher than the fine iPOM-C content (77–118 mg kg−1) in different size aggregates in S samples. In SM and M samples, however, the coarse iPOM-C contents (98–124 mg kg−1 (SM); 60–82 mg kg−1 (M)) were lower than the fine iPOM-C contents (129–151 mg kg−1 (SM); 71–103 mg kg−1 (M)). The ratio of coarse iPOM-C to fine iPOM-C content (ROC/F) exceeded 1 in S but was lower than 1 in SM and M. These results indicate that soil aggregation stability and SOC content increased and then decreased across the wetland succession sequence, and that ROC/F can be used as an indicator of changes in SOC content caused by wetland succession. • Mean weighted diameter presented a "Ʌ"-shaped tendency along wetland succession. • Swampy meadow had the highest bulk soil carbon and aggregate-associated carbon. • Swampy meadow can be preserved as a large amount of activated carbon. • Coarse/fine iPOM-C is an indicator of SOC change along wetland succession. [ABSTRACT FROM AUTHOR]

Ultra-high Performance Concrete (UHPC) exposed to cryogenic temperatures typically fails in a brittle fashion, with a failure mode that is undesirable and catastrophic. In this study, the Thermal-dependent Brittleness (TDB) concept and its utilization for the evaluation of UHPCs exposed to different cryogenic temperatures were undertaken. Herein, flexural load-deflection curves of UHPC specimens and the absorbed energy evolution mechanism were analyzed. Moreover, the deformation and failure of UHPC specimens were also monitored utilizing changes in the Acoustic Emission (AE) signal. Results showed that whereas one-cycle flexural strength of UHPC specimen generally increased as test temperature reduced from 20 °C to −170 °C, a mixed effect on the toughness index was observed. The highest and lowest flexural toughness indexes were recorded for tests conducted at −110 °C and −170 °C, respectively. Moreover, the brittleness of UHPCs tested within −170 °C was accurately estimated by the newly proposed TDB all index. Finally, AE signals indicated that while tensile cracks exceeded shear cracks in specimens tested between 20 °C and −80 °C, there is a preponderance of shear cracks in specimens tested at −110 °C and −140 °C. [ABSTRACT FROM AUTHOR]

This paper reports the flexural performance of ultra-high performance concrete (UHPC) exposure to six temperature conditions, including ambient temperature (A), after exposure to 200 °C (EA), in-situ −170 °C (DC), in-situ −170 °C after exposure to 200 °C (IDC), after exposure to −170 °C (AC), after exposure to 200 °C and −170 °C (AEC). The cracking characteristics of UHPC under the coupling effect of cryogenic and external load is identified with acoustic emission (AE) technology. The results show that DC condition is the most efficient in enhancing flexural strength and toughness due to frozen water and improved bond strength. A nonlinear relationship between first-peak deflection and first-peak flexural strength is observed because of the changed flexural modulus at different temperature conditions. The increasing shear cracks in linear-elastic stage is attributed to the fracture process of frozen water, which can account for the significant increase of first-peak strength at DC and IDC conditions. Cryogenic-induced ductility degradation is observed in the flexural behaviour of UHPCs at DC and IDC conditions, which is attributed to higher energy release rate. Furthermore, pre-exposure to 200 °C reduced the positive influence of cryogenic temperature on flexural performance and the negative effect of cryogenic temperature on ductility because of the initiated cracks around steel fibers. • Cracking behaviour of UHPC at cryogenic temperature is studied by acoustic emission. • Cryogenic-induced ductility degradation is due to more energy released in less time. • Pre-exposure to 200 °C reduces adverse effect of cryogenic temperature on ductility. [ABSTRACT FROM AUTHOR]

• Study performance of UHPC after alternating elevated and cryogenic attack (AECA) • Flexural Cracking behaviour of UHPC after AECAs is identified by acoustic emission. • AECA has dual effect of enhancement and deterioration on flexural property of UHPC. • Empirical equations are proposed to estimate flexural toughness and load of UHPC. This paper investigates the flexural performance of ultra-high-performance concrete (UHPC) subjected to a simulated lunar ground temperature environment between 200 °C and −170 °C termed as alternating elevated and cryogenic attack (AECA). Additionally, the cracking behavior during the failure process was characterized by acoustic emission (AE) technique. Compared with unexposed UHPC specimens, those exposed to AECA up to five cycles still exhibit superior flexural performance. The AE results imply that tensile cracks are mainly generated by the failure of cement matrix, and shear cracks are mainly attributed to the steel fiber–matrix debonding and steel fiber pull-out behaviour. AECA exhibits the dual effect of enhancement and deterioration on the flexural performance of UHPCs, and there is even a competitive relationship between the two effects. Due to the dual effect, cement matrix strength and bond strength between cement and steel fiber show different responses to AECA. Finally, four prediction equations that matched excellently with the experimental results are proposed to estimate the residual flexural load and compute the flexural toughness directly according to Newton-Leibniz law instead of integrating the area under the load–deflection curve. [ABSTRACT FROM AUTHOR]

Understanding the cryogenic behaviour of geopolymer composite (GPC) is essential to implement them in real structural elements at cryogenic temperatures. The paper presents a comprehensive investigation on the compressive strength, flexural behaviours, and energy absorption capability of both plain GPC and fiber-reinforced geopolymer composite (FRGPC) containing different fiber types and contents subjected to in-situ −170 °C. The results demonstrate that the compressive strength of plain GPC and FRGPC increases by 104.9 %–213.6 %, and the flexural strength increases by 73.4 %–212.5 %, exhibiting a significant cryogenic strengthening effect. Moreover, compared to flexural strength, compressive strength of GPCs displays a higher sensitivity to the cryogenic strengthening effect. The failure mode of FRGPCs changed from ductile failure to ductile-brittle failure at −170 °C, which is due to the decreased ductility induced by the cryogenic embrittlement effect. Additionally, cryogenic exposure has a greater impact on reducing the ductility of FRGPCs containing PP fibers than those with steel fibers. However, the negative effects of cryogenic embrittlement effect on ductility can be mitigated by incorporating steel fibers and increasing fiber content. The further analysis reveals that strengthening and embrittlement effect are associated with the increased cumulative energy and the sudden release of local energy, respectively. These findings contribute to the understanding of GPC performance at cryogenic temperature, which can guide the development of more resilient and durable GPC for cryogenic applications. • The strength and brittleness of geopolymer matrix and fibers increased at cryogenic. • Compressive strength exhibited higher sensitivity to cryogenic strengthening effect. • Failure mode changed from ductile failure to ductile-brittle failure at −170 °C. • Higher energy absorption capability was observed for GPC at cryogenic. [ABSTRACT FROM AUTHOR]

The in-depth investigation on mechanical and microstructural properties of cementitious materials subjected to cryogenic freeze-thaw cycles (CFTCs) is essential to efficiently improve their resistance to CFTCs. This study examines the effects of CFTCs ranging from 20 °C to −170 °C up to 9 cycles on geopolymer mortars (GPMs), including the role of polypropylene (PP) fiber on their responses to CFTCs. The compressive strength of GPMs initially improved with the CFTCs up to 3 cycles, followed by a decreasing trend with the CFTCs up to 9 cycles. The GPMs with PP fiber exhibited a monotonic and more significant decrease in the compressive strength after exposure to CFTCs. The permeability of GPMs increased with the increasing number of CFTCs due to the increasing cumulative pore volume and deteriorating microstructure, which are also found to be responsible for the decrease in compressive strength. Notably, pores with a diameter of 2500 nm are identified as a critical value in affecting GPMs' compressive strength. Higher proportions of pores with diameter smaller than 2500 nm enhance compressive strength, while pores exceeding the values have the opposite effect. Additionally, the compressive strength tends to decrease with the increase of microcrack attributes including total microcrack area, total microcrack length, and average microcrack width. GPMs with PP fiber exhibited weaker resistance to CFTCs due to the presence of more free water and the negative thermal expansion attribute of PP fiber. This exacerbates the adverse effects of frost-heave stress and thermal-stress on GPMs. [ABSTRACT FROM AUTHOR]