Onset Of Expansion Research Articles

Study on the decay laws and deterioration mechanism of mechanical properties of cement-stabilized gravel under water-heat-salt coupled conditions

A new type of asphalt pavement disease, known as arch expansion, has appeared in the saline soil regions of Northwest China. The emergence, as well as the evolution of the disease, is strongly related to the distribution of sulfate. However, the decay of Cement-stabilized gravel (CSG) mechanical properties is closely related to the onset and development of arch expansion. The relationship between CSG mechanical strength and salinity in the arch expansion area is analyzed based on field investigations to systematically study the mechanical property degradation law and mechanism of CSG. The mechanical strength and deterioration patterns of CSG with different coupling conditions were investigated. The mineral composition and micromorphology of the erosion products were analyzed. The results show that the mechanical properties of CSG in the area of the arch deteriorate more than those in the regular section. The mechanical strength of the specimens initially containing salt and partially immersed in salt solution decayed most severely. In terms of the deterioration mechanism of mechanical strength of CSG, the water-heat-salt erosion process is also divided into two parts, including the formation stage of gypsum and ettringite, the stage of C-S-H decomposition and thaumasite formation, respectively. The degradation mechanism of CSG is a combination of physical and chemical erosion.

Variation of the Altitude of Auroral Emission During a Substorm Cycle: Stereoscopic Optical Observations During the LAMP Rocket Experiment

AbstractWe estimated the altitude of aurora by combining data from all‐sky cameras at multiple places which were obtained during the LAMP sounding rocket experiment in Alaska on 5 March 2022. During the launch window of the rocket, three high‐speed all‐sky cameras were operative at three stations immediately below the trajectory of the rocket: Poker Flat, Venetie and Fort Yukon. The all‐sky cameras captured all‐sky images with a temporal resolution of 100 Hz (80 Hz for the Fort Yukon case). The method of altitude determination is based on analyses of time‐series of the optical intensity obtained from the all‐sky cameras in Venetie and Poker Flat covering the downrange area of the rocket trajectory. The estimated altitude of pulsating aurora during the rocket experiment was found to be consistent with that derived from the in‐situ observation of precipitating electrons with a model of optical emission, which confirms the feasibility of deriving the emission altitude through correlation analyses using time‐series. The estimated altitude of aurora decreased after the expansion onset of the substorm and stayed slightly below 100 km during the interval of pulsating aurora in the recovery phase. In particular, prompt and brief lowering of the auroral emission, well down to around 90 km, was detected during a transition of auroral form from discrete to diffuse which occurred ∼10 min after the onset. This result implies an existence of a process causing harder electron precipitation operative soon after the start of the expansion phase of auroral substorm.

Probing the shape of the quark-gluon plasma droplet via event-by-event quark-gluon plasma tomography

This study investigates quark-gluon plasma in heavy-ion collisions through two avenues: high-p⊥ frameworks and hydrodynamic modeling. Using the TRENTo model, we find that the p=0 value aligns well with high-p⊥ data, in agreement with Bayesian analysis of the low-p⊥ regime. While adjusting p values may improve a fit to a particular high-p⊥ observable, it does not permit an earlier onset of transverse expansion. Published by the American Physical Society 2024

Influence of initial stresses and stress paths on the deformation and failure mechanism of sandy slate

Rocks exhibit various mechanical properties under different stress conditions, with changes during unloading having significant implications for geological engineering safety. This study carried out triaxial loading and unloading mechanical tests on sandy slate to investigate its mechanical properties, deformation characteristics, and failure mechanisms at different initial stress levels and stress paths. The results showed that during the unloading process, the deformation modulus (E) of the sandy slate decreased, and the Poisson's ratio (μ) gradually increased. This indicates that significant volume expansion of the rock is the dominant factor in its deformation and failure. The exponential function can be used to describe the evolution of E and μ with confining pressure during unloading. The damage stress of the rock under unloading conditions was lower than that under loading conditions, suggesting that unloading led to an earlier onset of volumetric expansion in the sandy slate. Under conditions where the initial axial stress level approached the damage stress, the mechanical properties were most significantly affected by unloading. Compared to loading conditions, when the initial axial stress level was at 70% of the peak strength, the cohesion (c) decreased by 15.77 to 29.37%, while the internal friction angle (φ) increased by 1.88 to 5.14%. The rock's failure process can be divided into four stages based on the development of microcracks. Unloading during the stages of microcrack initiation and propagation can lead to tensile cracks of varying degrees, resulting in different mechanical properties and failure characteristics under loading and unloading conditions.

The last deglaciation in the central Pyrenees: The 47 ka Pllan d’Están paleolake record (Ésera valley)

Last deglaciation was a complex period in southern European mountains with several glacier advances associated to rapid climate changes which differ in terms of timing and intensity. The 46.7 ka BP lacustrine sequence of Pllan d’Están paleolake (1840 m a.s.l.) located in the Central Southern Pyrenees (northern Spain) provides new information about that deglaciation period for the first time in the Ésera valley. We present a multiproxy analysis including sedimentological, geochemical and biological (pollen and diatoms) indicators that, together with a chronological frame constrained by 14C and OSL dates, enabled the longest reconstruction of the glacier evolution, climate and environmental change made in the Pyrenees to date. This lacustrine sedimentary sequence (4.9 m) is composed of banded to finely laminated silts with few intercalations of massive sections where carbonatic, siliciclastic and organic facies appear from the bottom to the top, characterizing environmental changes from a subglacial/proglacial lake to the current peatbog. A cold and glacier dominated period from 46.7 to 15.9 ka BP was interrupted by a warmer period spanning from 38.2 to 34.8 ka BP. The vegetation succession determined by the palynological analyses is similar to other Pyrenean valleys but dates the onset of mesophytes expansion at 13.8 ka BP during the Allerød, pointing to a difference with other European sequences where temperate forest development took place earlier, associated to the Bølling period. The colder conditions of the Younger Dryas (13–11.7 ka BP) have been detected from cold tolerant diatom taxa that preceded a peatbog development during the Holocene (11.7 ka BP – present-day). These results, together with previously studied Pyrenean sequences, allow characterizing past environmental changes during last deglaciation phases in southern Europe.

Long-term behavior of mortars experiencing delayed ettringite formation

Ettringite formation is an expansive reaction that causes cracking in the hydrated cementitious materials. This research has investigated the mechanisms of ettringite formation by examining the chemical and physical structure of the reactants and products involved in the process of late age (over 15 years) ettringite formation, and subsequent expansion and cracking. For this, seven different types of commercially available cement with their unique composition, and an elevated heat curing temperature of up to 100 °C were applied. The physical expansion of mortar bars due to delayed ettringite formation was monitored by the length change comparator. Environmental scanning electron microscopy (ESEM) was used to qualify and quantify changes in the microstructure and chemical composition of the cementitious matrix. Results revealed that the high-temperature heat curing accelerated the onset of expansion but limited the over-magnitude of the expansion. Results also revealed that the expansion may take years to initiate, likely due to a critical pore size threshold necessary to induce stresses. If expansion is delayed, the expansion magnitude is greater than those that expanded immediately.

Evolving copy number gains promote tumor expansion and bolster mutational diversification

The timing and fitness effect of somatic copy number alterations (SCNA) in cancer evolution remains poorly understood. Here we present a framework to determine the timing of a clonal SCNA that encompasses multiple gains. This involves calculating the proportion of time from its last gain to the onset of population expansion (lead time) as well as the proportion of time prior to its first gain (initiation time). Our method capitalizes on the observation that a genomic segment, while in a specific copy number (CN) state, accumulates point mutations proportionally to its CN. Analyzing 184 whole genome sequenced samples from 75 patients across five tumor types, we commonly observe late gains following early initiating events, occurring just before the clonal expansion relevant to the sampling. These include gains acquired after genome doubling in more than 60% of cases. Notably, mathematical modeling suggests that late clonal gains may contain final-expansion drivers. Lastly, SCNAs bolster mutational diversification between subpopulations, exacerbating the circle of proliferation and increasing heterogeneity.

Abstract IA023: Spatial reconstruction and temporal inference of DNA methylation alterations in primary human colorectal cancer

Abstract Phenotypic plasticity is thought to assist immune evasion, metastasis, and therapeutic resistance in tumor evolution. Epigenetic mechanisms such as DNA methylation provide for a more easily acquired and flexible, yet semi-stable adaptation by the tumor cell than hardwired genetic changes. Cancer-associated gain of DNA methylation at promoter CpG islands or distal regulatory elements is associated with transcriptional silencing, whereas loss of DNA methylation is observed at late-replicating, lamina-attached regions of the genome, tracking with cumulative cell divisions. One of the most well-documented genomic features predisposing to DNA hypermethylation is Polycomb Repressive Complex (PRC) occupancy in precursor cells, consistent with an epigenetic block to cellular differentiation as an early or predisposing event in carcinogenesis. A central question is whether this epigenetic switch from reversible PRC repression to more stable DNA hypermethylation occurs before onset of clonal expansion, or whether it represents an ongoing process during tumor evolution. Clonal expansion is a pivotal characteristic of cancer, and is thought to be initiated by a genetic alteration in a key gatekeeper driver gene. However, not all normal cells appear to be susceptible to malignant transformation following such an event. Multiple lines of evidence suggest that epigenetic heterogeneity among normal cells may affect their cancer-initiating potential. We have developed a tumor processing pipeline to deeply and comprehensively map DNA methylation patterns in primary human colorectal cancer (CRC) and adjacent tissues, while preserving spatial information, enabling inference of the temporal order of molecular alterations. We employ a suite of technologies to map the spatial heterogeneity of DNA methylation patterns in primary human CRC. These include a deep single-cell whole-genome bisulfite sequencing technique that improves genomic coverage several-fold over existing published protocols, providing DNA methylation measurements at the majority of CpGs in the genome in individual tumor cells. We have also calibrated and validated an epigenetic clock that allows us to accurately measure the relative replicative history of individual cells. We infer phylogenetic relationships among subclones, and relate these to their spatial distribution in the primary tumor. We find that some tumors have high proportions of PRC-associated clonal hypermethylation, indicating that these hypermethylation events were already present prior to clonal expansion, possibly contributing to susceptibility to malignant transformation in the cell-of-origin, whereas other tumors appear to have active PRC-associated CpG island hypermethylation ongoing during tumor expansion, generating subclonal heterogeneity, which may influence post-therapeutic recurrence potential. Citation Format: Peter W. Laird, Nathan J. Spix, Hsiao-yun Milliron, Manpreet Kalkat, Emily Eugster, David Sokol, Emily Jung, Paula Nolte, Kelly K. Krzyzanowski, Toshinori Hinoue, Hui Shen. Spatial reconstruction and temporal inference of DNA methylation alterations in primary human colorectal cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Translating Cancer Evolution and Data Science: The Next Frontier; 2023 Dec 3-6; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_2):Abstract nr IA023.

Nonlinear increase in seawater 87Sr ∕ 86Sr in the Oligocene to early Miocene and implications for climate-sensitive weathering

Abstract. The 87Sr / 86Sr of marine carbonates provides a key constraint on the balance of continental weathering and hydrothermal Sr fluxes to the ocean, and the mid-Oligocene to mid-Miocene period features the most rapid rates of increase in the 87Sr / 86Sr of the Cenozoic. Because previous records of the 87Sr / 86Sr increase with time were based on biostratigraphically defined age models in diverse locations, it was difficult to unambiguously distinguish million-year-scale variations in the rate of 87Sr / 86Sr change from variations in sedimentation rate. In this study, we produce the first 87Sr / 86Sr results from an Oligocene to early Miocene site with a precise age-model-derived orbital tuning of high-resolution benthic δ18O at Equatorial Pacific Ocean Drilling Program (ODP) Site 1218. Our new dataset resolves transient decreases in 87Sr / 86Sr, as well as periods of relative stasis. These changes can be directly compared with the high-resolution benthic δ18O at the same site. We find that slowing of the rate of 87Sr / 86Sr increase coincides with the onset of Antarctic ice expansion at the beginning of the mid-Oligocene glacial interval, and a rapid steeping in the 87Sr / 86Sr increase coincides with the benthic δ18O evidence for rapid ice retreat. This pattern may reflect either northward shifts in the Intertropical Convergence Zone precipitation to areas of nonradiogenic bedrock and/or lowered weathering fluxes from highly radiogenic glacial flours on Antarctica. We additionally generate the first 87Sr / 86Sr data from ODP Site 1168 on the Tasman Rise and Integrated Ocean Drilling Program (IODP) Site 1406 of the Newfoundland Margin during the Oligocene to early Miocene to improve the precision of age correlation of these Northern Hemisphere and Southern Hemisphere midlatitude sites and to better estimate the duration of early Miocene hiatus and condensed sedimentation.

A mechanism of the auroral substorm expansion onset: electric discharge in the double layer

Magnetospheric substorms often occur when a significant amount of energy from the solar wind is deposited and stored in the magnetotail during the growth phase and release explosively in the expansion phase, which accelerates charged particles causing the rapid auroral intensification. A physical mechanism is needed to release the energy explosively. The formation of double layers is a likely mechanism for the energy release and the acceleration of particles and triggers the onset of the expansion phase. We suggest that the localized parallel electric field that forms the double layer results from the displacement current complying with Ampere’s law for the dynamic case. The double layers are embedded in low density cavities surrounded by enhanced magnetic stresses. Positive feedback in the electric field generation may cause rapid release of the accumulated energy. The Poynting flux carried by Alfven waves continuously supplies the energy to maintain strong electric fields during the rapid development of auroral substorms.

Thermal Insulation Products Based on Modified Polyurethane Foam with Fire-Resistant Coating

As part of the study, thermal insulation products based on rigid polyurethane foam (PPU) with a reduced flammability group were obtained. The effect of modification of polyurethane foam with oxidized thermally expansive graphite (OTG) on physical, mechanical and fire hazard properties was studied. A two-component factory-ready system with a G4 flammability group was used as the initial composition for modification. OTG brand: KR 350-80 was used as a modifier, characterized by a degree of expansion of at least 370 ml/g, a temperature of the onset of expansion of 170°C. Products made from polyurethane foam were modified by the method of dispersing OTG in a reactive composition, as well as by applying a fire-retardant coating during injection molding of masses. Samples were made and tests were carried out to determine the flammability group in accordance with GOST 30244. It was established that an increase in the concentration of OTG in the fire retardant coating and the structure of the material reduces the flammability of products, while modification by the dispersion method makes it possible to obtain a material with a flammability group (G3), but has an effect on the technological properties of the initial composition, leads to an increase in the viscosity of the reactive composition and an increase in the density of the products, while the modification of the fire retardant coating with honey does not affect the technological and physical-mechanical properties of the final product, and makes it possible to obtain a flammability group G1–G2 depending on the concentration of OTG.

The Late Intermediate Period in the south-central Andes (AD 1000–1450): Key problems in chronology

The Late Intermediate Period (LIP, cal AD 1000–1450) in the central Andes is defined as a hiatus after the collapse of Tiwanaku and Wari, expansive state polities of the Middle Horizon (cal AD 600–1000), and before the domination of the Inca empire in the Late Horizon (cal AD 1450–1532). The LIP is often characterized as a unit, but major developments took place within this long period, including diasporic migrations and the new colonization of some regions, demographic change, intensified conflict, large-scale adverse climate episodes, and changes associated with the onset of Inca expansion. Here we make a preliminary attempt to clarify the chronology of these developments. A database of published and new radiocarbon dates is compiled for the south-central highlands and coastal valleys in order to model overall and subregional demographic trends using an updated “dates-as-data” cumulative kernel density estimate (CKDE) approach, and to examine specific LIP phenomena in two subregions. Our results indicate major demographic change including 1) substantial population growth beginning in the 13th century, 2) a marked 14th-century population surge in most, but not all, subregions included here, 3) evidence of population decline in several subregions during the same intervals when neighboring populations are expanding. Population growth was associated with intensified violence and increased physiological stress in the upper Nasca drainage. In the altiplano of Peru and Bolivia, population growth accompanied the rise of defensive hillforts and monumental cemeteries. Our date models also indicate a more complicated terminal LIP in the altiplano, with the height of classically “LIP” societies overlapping with early evidence for imperial Inca presence. This paper highlights the ways that more refined chronology can make advances in our understanding of a turbulent post-collapse era in the Andes.

Numerical modeling of flashing in TFC expanders for the efficient exploitation of low-grade heat

This paper presents a novel semi-empirical thermodynamic model for the simulation of two-phase expansion in twin-screw expanders. The model utilizes a limited number of unknown parameters, the values of which are calculated through a calibration-optimization process that exploits numerical experiments available in the literature. Two-phase expansion simulations are performed for a wide variety of operating conditions, revealing that the vapor quality at the suction port of the expander is the main factor affecting its efficiency. Increased vapor qualities at the onset of expansion lead to an increase in the expander’s efficiency because a better matching between the WF’s volume ratio and the expander’s built-in volume ratio can be achieved. The thermodynamic model is applied to assess the performance of a TFC engine operating under varying heat duties and temperatures of the heat source, indicating that a detailed analysis is necessary to conclude whether the TFC or the ORC is the optimal solution for a given application.

Anomalously strong effects of plume contraction and material redeposition in nanosecond pulsed laser vaporization

Long-term dynamics of vapor plumes induced by irradiation of a copper target in argon background gas by nanosecond laser pulses is studied numerically based on a one-dimensional hybrid computational model. The model includes a thermal model of the irradiated target and a kinetic model of the gaseous plume flow. The latter is implemented in the form of the direct simulation Monte Carlo method. The simulations, performed at moderate laser fluences in the range from 1.5 to 4 Jcm−2 and background gas pressures between 0.01 and 1 bar, show that the long-term plume dynamics can be divided into three major stages: initial inertial expansion, plume contraction, and subsequent diffusive expansion. The simulations unexpectedly predict extremely strong effects of plume contraction, when the plume size can exhibit a two-fold reduction, and delayed material redeposition back to the irradiated surface, when ∼90% of vaporized material returns to the irradiated surface. Both plume contraction and delayed redeposition originate from the strong backward flow induced by the internal (secondary) shock wave that propagates from the mixing layer towards the irradiated surface. The major part of vaporized material condenses at the surface with a long time delay with respect to the laser pulse after the plume stopping and before the onset of diffusive expansion. As a result, only a marginal part of vapor, which can be as small as ∼5%, is retained in the plume by the beginning of the diffusive expansion. The obtained simulation results suggest that the plume contraction and delayed material redeposition are common phenomena for nanosecond laser vaporization and may affect the efficiency and quality of laser surface modification in the ablation regime as well.

Mid‐Latitude Double H‐Spikes: Their Properties and Signatures in Different Geomagnetic Indices

AbstractProper assessment of geomagnetic disturbances is a key aspect of space weather as technology is often impacted by space weather activity without previous warnings or proper forecasts. Double H‐spikes are a form of longitudinal asymmetry observed at midlatitudes. They are geomagnetic disturbances occurring simultaneously on the dayside and nightside as a negative/positive H‐spike, which go unnoticed through common geomagnetic indices. This work presents the results of a systematic search for double H‐spikes occurred over a 23‐year period and analyzes characteristics of the double H‐spikes such as the occurrence dependence on the solar cycle, season, intensity and phase of the geomagnetic storm. Our outcomes indicate that double H‐spikes are a global phenomenon closely related with the substorm phenomenon and the ground magnetic disturbances observed at mid‐latitude are remote effects of field‐aligned currents (FACs). FACs would be the part of the substorm current wedge developed from the expansion onset of intense substorms whose effects have wide longitudinal extend as they are observed on the dayside and the nightside. Also mid‐latitude global SYM and ASY indices are affected by FACs during those periods. Time derivatives of the SuperMAG SMR12 and SMR00 sector indices allow us to conclude that double H‐spikes, as short‐time high‐intensity magnetic disturbances, pose a potential risk to damage ground‐technological systems at midlatitudes.

Singlet Oxygen Flux, Associated Lipid Photooxidation, and Membrane Expansion Dynamics Visualized on Giant Unilamellar Vesicles.

The physical properties of lipid membranes depend on their lipid composition. Photosensitized singlet oxygen (1O2) provides a handle to spatiotemporally control the generation of lipid hydroperoxides via the ene reaction, enabling fundamental studies on membrane dynamics in response to chemical composition changes. Critical to relating the physical properties of the lipid membrane to hydroperoxide formation is the availability of a sensitive reporter to quantify the arrival of 1O2. Here, we show that a fluorogenic α-tocopherol analogue, H4BPMHC, undergoes a >360-fold emission intensity enhancement in liposomes following a reaction with 1O2. Rapid quenching of 1O2 by the probe (kq = 4.9 × 108 M-1 s-1) ensures zero-order kinetics of probe consumption. The remarkable intensity enhancement of H4BPMHC upon 1O2 trapping, its linear temporal behavior, and its protective role in outcompeting membrane damage provide a sensitive and reliable method to quantify the 1O2 flux on lipid membranes. Armed with this probe, fluorescence microscopy studies were devised to enable (i) monitoring the flux of photosensitized 1O2 into giant unilamellar vesicles (GUVs), (ii) establishing the onset of the ene reaction with the double bonds of monounsaturated lipids, and (iii) visualizing the ensuing collective membrane expansion dynamics associated with molecular changes in the lipid structure upon hydroperoxide formation. A correlation was observed between the time for antioxidant H4BPMHC consumption by 1O2 and the onset of membrane fluctuations and surface expansion. Together, our imaging studies with H4BPMHC in GUVs provide a methodology to explore the intimate relationship between photosensitizer activity, chemical insult, membrane morphology, and its collective dynamics.

Dairy Products in Space Nutrition and Potential Processing of Dairy Products with 3D/4D Printers as a Space Food

Dairy products, which have been used for many years in the nutrition of individuals, have many benefits for human health. Due to recent developments such as climate changes, raw material deficiency and increased population, humankind has been forced to seek alternative resources from the space in the latest decades. Yet, in the space, feeding has for so long been world-centered and effectuated short term. Due to swift rise of 3-dimensional and 4-dimensional printer technologies at the end of 20th century, onset of 21st century, quick expansion, and wide use of such technologies, their use in space missions and space-food production has come to the surface. Within the context of this study, data related to utilizing dairy products as a space food and data on using 3-dimensional (3D) and 4-dimensional (4D) printers to generate these products in space mission were collected and evaluated in the review.

Multiple anthropogenic pressures challenge the effectiveness of protected areas in western Tanzania

AbstractDespite being key conservation instruments, the ecological effectiveness of protected areas (PAs) is contested. To assess the ecological effectiveness of PAs in the Katavi‐Rukwa Ecosystem (KRE) in western Tanzania, we investigated temporal changes in land‐use and population densities of six large mammal target species (elephant, buffalo, giraffe, zebra, topi, and hartebeest) across areas with different conservation category, ranging from unprotected to strictly protected. During six survey periods between 1991 and 2018, we analyzed data from remote sensing and aerial wildlife surveys to derive (i) spatiotemporal patterns of cropland cover in relation to protection category; (ii) population densities of the six‐target species; and (iii) distribution of these species across protection category, land‐use and environmental variables. During the surveyed period, cropland increased from 3.4 % to 9.6 % on unprotected land and from ≤0.05 % to <1 % on protected land. Wildlife densities of most, but not all target species declined across the entire landscape, yet the onset of the observed wildlife declines occurred several years before the onset of cropland expansion. Logistic regression models indicated that target species preferred the national park over less strictly PAs and areas distant to cropland. As our data do not support a direct link between land‐use change and wildlife densities, additional factors may explain the apparent ecosystem‐wide decline in wildlife. To bolster wildlife conservation in the KRE, we recommended proactive strategies to reduce direct threats to wildlife and cropland expansion toward wildlife dispersal areas and migratory corridors.

Seasonal patterns of increases in stem girth, vessel development, and hydraulic function in deciduous tree species.

The onset of spring growth and vessel formation were examined within three deciduous woody plant species, Acer rubrum, Populus balsamifera ssp. trichocarpa and Quercus rubra. We were broadly interested in the lag between the onset of girth expansion and the formation of mature and hydraulically conductive vessels within the new xylem. Dendrometers were installed on 20 trees (6-7 per species), and expansion of both bole and distal stems was monitored throughout the growing season in a common garden. For each species, four to six distal stems were harvested every other week for anatomical examination of vessel formation. Additionally, for Populus and Quercus, hydraulic conductivity measurements and active xylem staining were completed on all stem samples. For all three species, the timing of girth expansion was similar. Expansion of distal branches occurred 12-37 d earlier than that of the bole. Vessel formation initiated several weeks prior to leaf-out, but no new earlywood vessels were mature at the time of bud break for Acer and Populus and only a few were present in Quercus. Initial stem girth expansion occurred 2 to >6 weeks before the maturation of the first current-year vessels, and there was an additional delay of up to 4 weeks before mature vessels became hydraulically functional. Hydraulic conductivity was strongly correlated with the number and diameter of stained vessels. Bud break and leaf expansion relied predominantly on water supplied by vessels formed during prior seasons. Early-season activity is likely affected by the function of older xylem vessels and the environmental factors that influence their structure and function. Understanding the functional lifespan of vessels and the varying contributions of new and older vessels to conductivity are critical to understanding of the phenology and vascular function of long-lived woody plants in response to changing climates.

Mechanism understanding of alkali-silica reaction in alkali-activated materials system

To provide a better understanding of the mechanism of alkali-silica reaction (ASR) in alkali-activated materials (AAMs) system, in this work, the ASR behavior of alkali-activated slag (AAS)/fly ash (AAFA) mortars were investigated, and compared with ordinary Portland cement (OPC) mortars. It is found that although the AAS mortar bars experience the shrinkage first, the onset of ASR-induced expansion of AAS mortar bars is earlier than OPC mortar bars. In AAMs system, the reactive silica from aggregates is evidently dissolved and participated in the early-age alkali-activation, and thereby leads to the reduction of reactive silica for ASR. The Ca/Si ratio of amorphous ASR products in AAS mortars was lower, while Al/Si and Na/K ratios were higher than that of OPC mortars. Based on the obtained experimental evidences, a conceptual model was proposed to interpret and compare the ASR behavior in OPC, AAS and AAFA systems.