Search Results (1,283)

In order to find the anti-freezing durability differences between concrete in the frequent natural freeze–thaw conditions in the northwest of Sichuan Province, China, and concrete in the rapid freeze–thaw conditions of the standard rapid method, the typical temperature and humidity of the northwest of Sichuan Province were simulated. The results showed that the average number of freeze–thaw cycles in the northwest of this province can reach up to 150 per year. The relative dynamic modulus of C30 ordinary concrete, which is 100% pre-saturated, still remained above 90% after 450 cycles in simulated environments. However, during the rapid freeze–thaw test, even the C30 air-entrained concrete failed after 425 cycles. Compared to the saturation degree of concrete itself, the continuous replenishment of external moisture during freeze–thaw cycles is a key factor affecting the frost resistance of concrete. Rapid freeze–thaw reduces the number of the most probable pore sizes in ordinary concrete, and the pore size distribution curve tends to flatten. The reduction rate of the surface porosity of air-entrained concrete before and after rapid freeze–thaw is only about one third of that of ordinary concrete. Full article

Understanding the mechanisms responsible for the origin, evolution, and failure of pingos with explosive gas emissions and the formation of craters in the Arctic permafrost requires comprehensive studies in the context of fluid dynamic processes. Properly choosing modeling methods for the joint interpretation of geophysical results and analytical data on core samples from suitable sites are prerequisites for predicting pending pingo failure hazards. We suggest an optimal theoretically grounded workflow for such studies, in a site where pingo collapse induced gas blowout and crater formation in the Yamal Peninsula. The site was chosen with reference to the classification of periglacial landforms and their relation to the local deformation pattern, according to deciphered satellite images and reconnaissance geophysical surveys. The deciphered satellite images and combined geophysical data from the site reveal a pattern of periglacial landforms matching the structural framework with uplifted stable permafrost blocks (polygons) bounded by eroded fractured zones (lineaments). Greater percentages of landforms associated with permafrost degradation fall within the lineaments. Resistivity anomalies beneath pingo-like mounds presumably trace deeply rooted fluid conduits. This distribution can be explained in terms of fluid dynamics. N–E and W–E faults, and especially their junctions with N–W structures, are potentially the most widely open conduits for gas and water which migrate into shallow sediments in the modern stress field of N–S (or rather NEN) extension and cause a warming effect on permafrost. The results obtained with a new workflow and joint interpretation of remote sensing, geophysical, and analytical data from the site of explosive gas emission in the Yamal Peninsula confirm the advantages of the suggested approach and its applicability for future integrated fluid dynamics research. Full article

Climatic conditions are the main factor influencing the suitability of agricultural land for crop production. Therefore, the evaluation of climate change impact on crop suitability using the best possible methods and data is needed for successful agricultural climate change adaptation. This study presents the application of a multi-criteria evaluation approach to assess climate suitability for maize production in Poland, for a baseline period (BL, 1981–2010) and two future periods 2041–2070 (2050s) and 2071–2100 (2080s) under two RCP (Representative Concentration Pathways) scenarios: RCP4.5 and RCP8.5. The analyses incorporated expert knowledge using the Analytical Hierarchy Process (AHP) into the evaluation of criteria weights. The results showed that maturity and frost stress were the most limiting factors in assessing the climatic suitability of maize cultivation in Poland, with 30% and 11% of Poland classified as marginally suitable or not suitable for maize cultivation, respectively. In the future climate, the area limited by maturity and frost stress factors is projected to decrease, while the area of water stress and heat stress is projected to increase. For 2050 climate projections, water stress limitation areas occupy 7% and 8% of Poland for RCP4.5 and RCP8.5, respectively, while for 2080 projections, the same areas occupy 12% and 32% of the country, respectively. By 2080, heat stress will become a limiting factor for maize cultivation; according to our analysis, 3% of the Polish area under RCP8.5 will be marginally suitable for maize cultivation because of heat stress. The overall analyses showed that most of Poland in the BL climate is in the high suitability class (62%) and 38% is moderately suitable for maize cultivation. This situation will improves until 2050, but will worsen in the 2080s under the RCP8.5 scenario. Under RCP8.5, by the end of the century (2080s), the highly suitable area will decrease to 47% and the moderately suitable area will increase to 53%. Full article

Despite the provision of a mumps vaccination program in Canada for over three decades, mumps has not reached elimination. Instead, a re-emergence has been observed in vaccinated populations, particularly in young adults. These outbreaks have been almost exclusively due to genotype G infections, a trend that has been seen in other countries with high mumps vaccination rates. To characterize mumps outbreaks in Canada, genomes from samples from Manitoba (n = 209), Newfoundland (n = 25), and Nova Scotia (n = 48) were sequenced and analysed by Bayesian inference. Whole genome sequencing was shown to be highly discriminatory for outbreak investigations compared to traditional Sanger sequencing. The results showed that mumps virus genotype G most likely circulated endemically in Canada and between Canada and the US. Overall, this Canadian outbreak data from different provinces and ancestral strains demonstrates the benefits of molecular genomic data to better characterize mumps outbreaks, but also suggests genomics could further our understanding of the reasons for potential immune escape of mumps genotype G and evolution in highly vaccinated populations. With a possible endemic circulation of mumps genotype G and the remaining risk of new imported cases, increased surveillance and alternative vaccination strategies may be required for Canada to reach the current target for mumps or a future elimination status. Full article

Freeze–thaw damage significantly contributes to the degradation of concrete structures. A critical precondition for concrete to experience frost damage is reaching its critical saturation level. This study conducted freeze–thaw experiments on concrete specimens under both open and sealed moisture conditions to elucidate the mechanisms of freeze–thaw damage and the pivotal role of moisture. The research assessed concrete’s water absorption, ultrasonic pulse velocity, and compressive strength under restricted water conditions to study damage accumulation patterns. The findings indicate that implementing water limitation measures during freeze–thaw cycles can regulate concrete’s water absorption rate, reduce the loss of ultrasonic pulse velocity, and minimize strength degradation, with an observed strength increase of up to 36.22%. Consequently, these measures protect concrete materials from severe frost damage. Furthermore, a predictive model for concrete freeze–thaw deterioration was established based on regression analysis and relative dynamic modulus theory, confirming the critical role of water limitation in extending the service life of concrete structures in cold regions. Full article

Interleukin (IL)-9 is present in atopic dermatitis (AD) lesions and is considered to be mainly produced by skin-homing T cells expressing the cutaneous lymphocyte-associated antigen (CLA). However, its induction by AD-associated triggers remains unexplored. Circulating skin-tropic CLA⁺ and extracutaneous/systemic CLA⁻ memory T cells cocultured with autologous lesional epidermal cells from AD patients were activated with house dust mite (HDM) and staphylococcal enterotoxin B (SEB). Levels of AD-related mediators in response to both stimuli were measured in supernatants, and the cytokine response was associated with different clinical characteristics. Both HDM and SEB triggered heterogeneous IL-9 production by CLA⁺ and CLA⁻ T cells in a clinically homogenous group of AD patients, which enabled patient stratification into IL-9 producers and non-producers, with the former group exhibiting heightened HDM-specific and total IgE levels. Upon allergen exposure, IL-9 production depended on the contribution of epidermal cells and class II-mediated presentation; it was the greatest cytokine produced and correlated with HDM-specific IgE levels, whereas SEB mildly induced its release. This study demonstrates that both skin-tropic and extracutaneous memory T cells produce IL-9 and suggests that the degree of allergen sensitization reflects the varied IL-9 responses in vitro, which may allow for patient stratification in a clinically homogenous population. Full article

Air-source heat pumps (ASHPs), as an active device, are widely used in building heating and cooling processes. However, in severe cold regions, they face reduced heating efficiency and frosting problems in winter. This paper proposes a new heating solution by coupling an ASHP with passive heating systems. It combines an ASHP with passive sunrooms and heat storage systems for heating. Through software simulations and mathematical modeling, the new scheme is compared and analyzed against traditional ASHP solutions to explore the performance of this scheme in rural houses in severe cold regions of China during winter. According to simulation and calculation analysis, on the coldest day of winter, the coupling scheme can provide approximately 99.41 kWh of heat to the indoors, which exceeds the 86.67 kWh required to maintain an indoor temperature of 20 °C. The system’s power consumption is 36.96 kWh, which is 66.88% lower than that of traditional heat pump heating. The study shows that the coupling system of an ASHP and passive heating has a good heating effect in severe cold regions. For the situation of insufficient solar energy at night, the design of phase-change materials and heat storage media can meet heating needs throughout the day. Full article

High temperature superconductors (HTSs) are enablers of extensive electrification for aircraft propulsion. Indeed, if used in electrical machines, HTS materials can drastically improve their performance in terms of the power-to-weight ratio. Among the different topologies of superconducting electrical machines, a flux modulation machine based on HTS bulks is of interest for its compactness and light weight. Such a machine is proposed in the FROST (Flux-barrier Rotating Superconducting Topology) project led by Airbus to develop new technologies as part of their decarbonization goals driven by international policies. The rotor of the machine will house large ring-segment-shaped HTS bulks in order to increase the output power. However, the properties of those bulks are scarcely known and have barely been investigated in the literature. In this context, the present work aims to fill out partially this scarcity within the framework of FROST. Thus, a thorough characterisation of the performances and homogeneity of 11 large REBaCuO bulks was carried out. Ten of the bulks are to be utilized in the machine prototype, originally keeping the eleventh bulk as a spare. A first set of characterisation was conducted on the eleven bulks. For this set, the trapped field mapping and the critical current were estimated. Then, a series of in-depth characterisations on the eleventh bulk followed. It included critical current measurement, X-ray diffraction, and scanning electron microscopy on different millimetre-size samples cut out from the bulk at various locations. The X-ray diffraction and scanning electron microscopy showed weakly oxygenated regions inside the bulk explaining the local drop or loss in superconducting properties. The objective was to determine the causes of the inhomogeneities found in the trapped field measured on all the bulks, sacrificing one of them, here the spare one. To help obtain a clearer picture, a numerical model was then elaborated to reproduce the field map of the eleventh bulk using the experimental data obtained from the characterisation of its various small samples. It is concluded that further characterisations, including the statistics on various bulks, are still needed to understand the underlying reasons for inhomogeneity in the trapped field. Nonetheless, all the bulks presented enough current density to be usable in the construction of the proposed machine. Full article

An undesirable sensory attribute (“floral taint”) has recently been detected in red wines from some winegrowing jurisdictions in North America (e.g., Ontario, British Columbia, Washington), caused by the introduction of frost-killed leaves and petioles [materials-other-than-grapes (MOG)] during mechanical harvest and winemaking. It was hypothesized that terpenes, norisoprenoids, and higher alcohols would be the main responsible compounds. The objectives were to investigate the causative volatile compounds for floral taint and explore threshold concentrations for this problem. Commercial wines displaying varying intensities of floral taint were subjected to GC-MS and sensory analysis. Several odor-active compounds were higher in floral-tainted wines, including terpenes (geraniol, citronellol, cis- and trans-rose oxide), norisoprenoids (β-damascenone, β-ionone), five ethyl esters, and three alcohols. Thereafter, fermentations of Cabernet Franc (CF) and Cabernet Sauvignon (CS) (2016, 2017) were conducted. MOG treatments were (w/w): 0, 0.5%, 1%, 2%, and 5% petioles, and 0, 0.25%, 0.5%, 1%, and 2% leaf blades. Terpenes (linalool, geraniol, nerol, nerolidol, citronellol, citral, cis- and trans-rose oxides, eugenol, myrcene), norisoprenoids (α- and β-ionone), and others (e.g., hexanol, octanol, methyl and ethyl salicylate) increased linearly/quadratically with increasing MOG levels in both cultivars. Principal components analysis separated MOG treatments from the controls, with 5% petioles and 2% leaves as extremes. Increasing MOG levels in CF wines increased floral aroma intensity, primarily associated with terpenes, higher alcohols, and salicylates. Increased leaf levels in CF were associated with higher vegetal and earthy attributes. Increased petioles in CS were not correlated with floral aromas, but increased leaves increased floral, vegetal, and herbaceous attributes. Overall, petioles contributed more to floral taint than leaves through increased terpenes and salicylates (floral notes), while leaves predominantly contributed norisoprenoids and C₆ alcohols (green notes). Full article

To investigate the mechanical properties of cement concrete incorporating waste rubber powder, the response surface methodology was employed. The Box–Behnken central composite design was applied to analyze the three primary factors influencing the road performance of cement concrete containing waste rubber powder: the water–cement ratio, sand ratio, and waste rubber powder content. The study determined the impact of these factors on the flexural strength of waste rubber powder cement concrete at both 7 and 28 days. Additionally, the effects of the water–cement ratio, sand ratio, and waste rubber powder content on the performance of cement concrete were analyzed. To investigate the impact of waste rubber powder on cement concrete, various mechanical property tests were conducted, including compressive, flexural, dynamic elastic modulus, and impact performance tests. Furthermore, the study explored the influence of waste rubber powder on the noise reduction capacity of cement concrete using both the rubber ball impact method and ultrasonic method. Lastly, the durability of cement concrete with added rubber powder was assessed through shrinkage tests, frost resistance tests, and chloride ion penetration tests. Full article

Accurate frost observations are crucial for developing and validating frost prediction models. In 2022, the multi-sensor-based automatic frost observation system (MFOS), including an RGB camera, a thermal infrared camera, a leaf wetness sensor (LWS), LED lighting, and three glass plates, was developed to replace the naked-eye observation of frost. The MFOS, herein installed and operated in an apple orchard, provides temporally high-resolution frost observations that show the onset, end, duration, persistence, and discontinuity of frost more clearly than conventional naked-eye observations. This study introduces recent additions to the MFOS and presents the results of its application to frost weather analysis and forecast evaluation in an orchard in South Korea. The NCAM’s Weather Research and Forecasting (WRF) model was employed as a weather forecast model. The main findings of this study are as follows: (1) The newly added image-based object detection capabilities of the MFOS helped with the extraction and quantitative comparison of surface temperature data for apples, leaves, and the LWS. (2) The resolution matching of the RGB and thermal infrared images was made successful by resizing the images, matching them according to horizontal movement, and conducting apple-centered averaging. (3) When applied to evaluate the frost-point predictions of the numerical weather model at one-hour intervals, the results showed that the MFOS could be used as a much more objective tool to verify the accuracy and characteristics of frost predictions compared to the naked-eye view. (4) Higher-resolution and realistic land-cover and vegetation representation are necessary to improve frost forecasts using numerical grid models based on land–atmosphere physics. Full article

The internal pore structural characteristics and microbubble distribution features of concrete have a significant impact on its frost resistance, but their size is relatively small compared to aggregates, making them difficult to visually represent in the mesoscopic numerical model of concrete. Therefore, based on the ice-crystal phase transition mechanism of pore water and the theory of fine-scale inclusions, this paper establishes an estimation model for effective thermal conductivity and permeability coefficients that can reflect the distribution characteristics of the internal pore size and the content of microbubbles in porous media and explores the evolution mechanism of effective thermal conductivity and permeability coefficients during the freezing process. The segmented Gaussian integration method is adopted for the calculation of integrals involving pore size distribution curves. In addition, based on the concept that the fracture phase represents continuous damage, a switching model for the permeability coefficient is proposed to address the fundamental impact of frost cracking on permeability. Finally, the proposed estimation models for thermal conductivity and permeability are applied to the cement mortar and the interface transition zone (ITZ), and a thermal–hydraulic–mechanical coupling finite element model of concrete specimens at the mesoscale based on the fracture phase-field method is established. After that, the frost-cracking mechanism in ordinary concrete samples during the freezing process is explored, as well as the mechanism of microbubbles in relieving pore pressure and the adverse effect of accelerated cooling on frost cracking. The results show that the cracks first occurred near the aggregate on the concrete sample surface and then extended inward along the interface transition zone, which is consistent with the frost-cracking scenario of concrete structures in cold regions. Full article

The freeze–thaw effect has a significant impact on the strength deterioration of tunnel-lining concrete in cold regions. Therefore, the strength deterioration characteristics of concrete in a tunnel were studied, and silicone coating materials were used to improve its frost resistance and durability under freeze–thaw cycles. Freeze–thaw cycle tests were conducted on concrete specimens with different coatings. The freeze–thaw damage phenomenon, dynamic elastic modulus, and mass loss of the specimens were used to evaluate the freeze–thaw durability of concrete strengthened with coatings. The results demonstrated that silicone coatings effectively prevented moisture and corrosive substances from infiltrating the concrete, thereby enhancing its durability; the silicone–polyether hybrid had the most significant frost resistance at 500 g/m² and silane type III at 300 g/m², with freezing resistance times of 175 and 300, respectively. During the freeze–thaw process, the strength reduction rate of specimens was much greater than the mass loss rate of concrete. Taking into account the water environment surrounding the lining concrete and the site temperature, an equivalent indoor freeze–thaw cycle conversion model was established. The results can provide an experimental basis for selecting better frost-resistant materials for tunnel concrete in cold regions. Full article

In order to reduce the risk of early freezing damage to cement-based materials in winter construction, lime powder was used to improve the properties of the Portland cement–sulphoaluminate cement (PC–CSA) composite system at low temperatures. In this study, the effects of lime powder dosage on the properties of a PC–CSA blended system with two proportions (PC:CSA = 9:1 and 7:3) at −10 °C were investigated, and the mechanisms of improvement were revealed. The results showed that the compressive strength of the PC–CSA composite system was effectively improved, and the setting time was shortened by the addition of lime powder. Lime powder could effectively act as an early heating source in the PC–CSA composite system, as the maximum temperature of samples exposed to sub-zero temperatures was increased and the time before dropping to 0 °C was prolonged by the addition of lime powder. The extra CH generated by the hydration of lime powder provided an added hydration path for C₄A₃$\overline{\mathrm{S}}$, which accelerated the formation of AFt at each stage. Frozen water as well as the early frost damage were effectively decreased by lime powder because of the faster consumption of free water at an early stage. The modification of the hydration products also contributed to the denseness of the microstructure. Full article

As an important gelling material, cementitious materials are widely used in civil engineering construction. Currently, research on these materials is conducted using experimental and numerical image processing methods, which enable the observation and analysis of structural changes and mechanical properties. These methods are instrumental in designing cementitious materials with specific performance criteria, despite their resource-intensive nature. The material genome approach represents a novel trend in material research and development. The establishment of a material gene database facilitates the rapid and precise determination of relationships between characteristic genes and performance, enabling the bidirectional design of cementitious materials’ composition and properties. This paper reviews the characteristic genes of cementitious materials from nano-, micro-, and macro-scale perspectives. It summarizes the characteristic genes, analyzes expression parameters at various scales, and concludes regarding their relationship to mechanical properties. On the nanoscale, calcium hydrated silicate (C-S-H) is identified as the most important characteristic gene, with the calcium–silicon ratio being the key parameter describing its structure. On the microscale, the pore structure and bubble system are key characteristics, with parameters such as porosity, pore size distribution, pore shape, air content, and the bubble spacing coefficient directly affecting properties like frost resistance, permeability, and compressive strength. On the macroscale, the aggregate emerges as the most important component of cementitious materials. Its shape, angularity, surface texture (grain), crushing index, and water absorption are the main characteristics influencing properties such as chloride ion penetration resistance, viscosity, fluidity, and strength. By analyzing and mapping the relationship between these genes and properties across different scales, this paper offers new insights and establishes a reference framework for the targeted design of cementitious material properties. Full article