Cold Environmental Conditions Research Articles

Periglacial landforms and landscape development in southern England

The south-central and south-east England Geological Conservation Review region is unique in Britain in lying completely outside the margins of Quaternary ice sheets. In view of this, the area has been described as a ‘relict periglacial landscape’. This implies that the region has evolved its current form substantially under the influence of seasonal and/or perennial frost. In fact, modern research has demonstrated that permafrost, either continuous or discontinuous, likely existed across probably the whole of the region at different times during the Quaternary. This has important implications for ground permeability and the strength of sediments and soils and this has, without doubt, influenced landscape development. Whilst the whole region appears to have experienced cold environmental conditions, the landforms, structures and sediments of some sites are particularly associated with periglacial processes. Allington Quarry, Spot Lane Quarry, Oaken Wood, Chiddingly Wood (known locally as Chiddinglye Wood), High Rocks and Rusthall Common have exhibited typical cambering structures with open or closed gulls. The latter three sites also display a fine range of surface weathering features. Hubbard's Hill is characterised by solifluction and active-layer detachment slides and associated subsurface shear structures, whilst the sarsen trains at Fyfield Down and Valley of Stones are also attributed to solifluction processes. Birling Gap and Pegwell Bay exhibit spectacular sediment brecciation and involutions. Pegwell Bay is also known for its thick layer of periglacial loess, a sediment that is also a feature of North Cliff, Broadstairs. Unfortunately, the dating of these landscape features has, so far, proved possible only at Hubbard's Hill and Pegwell Bay. Nevertheless, the sites reviewed here provide exceptional, and in some cases internationally important, indications of landscape development in cold, often permafrost, environments which justifies their status as GCR sites.

Toward better targeting of mitigation measures for reducing phosphorus losses from land to water: Andrew Sharpley's legacy in Norway and Sweden.

Nordic agriculture faces big challenges to reduce phosphorus (P) loss from land to water for improving surface water quality. While understanding the processes controlling P loss and seeking for P mitigation measures, Norwegian and Swedish researchers have substantially benefited from and been inspired by Dr. Andrew Sharpley's career-long, high-standard P research. Here, we demonstrate how Sharpley and his research have helped the Nordic researchers to understand the role of cover crops in cold environmental conditions, best manure P management practices, and ditch processes. His work on critical source area (CSA) identification and site assessment tool development have also greatly inspired our thinking on the targeting of mitigation measures and the contextualizing tools for Nordic climate, landscape, and soils. While reflecting on Sharpley's legacy, we identify several needs for Norwegian and Swedish P research and management. These include (1) tackling the challenges caused by local/regional unevenness in livestock density and related manure management and farm P surpluses, (2) identifying CSAs of P loss with high erosion risk and high P surplus, (3) obtaining more high-resolution mapping of soils with low P sorption capacity both in the topsoil and subsoil, (4) improving cross-scale understanding of processes and mitigation measures and proper follow-up of applied mitigation measures, and (5) increasing collaborations of researchers with farmers and farmers' advisory groups and watershed groups by developing high-quality educational courses and extension materials. The needs should be addressed in the context of the challenges and opportunities created by climate change.

Responses of microbial community dynamics, co-occurrences, functional shifts, and natural fermentation profiles of Elymus nutans silage to altitudinal gradients.

On the Qinghai-Tibet Plateau (QTP), feed shortages are common due to cold environmental conditions and the short growing season of crops. Therefore, effective preservation, such as the ensiling of local forage, is becoming increasingly important to balance the seasonal imbalance between the forage supply and the nutritional needs of domestic animals in this area. However, the structure of the microbial community of the forage, which is influenced by climatic conditions such as altitude differences, has a major impact on the fermentation quality and microbial succession of the ensiled forage. Therefore, we investigated microbial community dynamics, co-occurrence, functional shifts, and natural fermentation profiles of Elymus nutans silage as a function of altitudinal gradients. Results show that silage from Chenduo at higher elevations has better fermentation quality and higher abundance of Lacticaseibacillus and Levilactobacillus than ensiled forage from other regions. This work may contribute to guiding for silage production in QTP.

Deciphering the microbial signature of death: advances in post-mortem microbial analysis

Cadaver decomposition is a natural phenomenon intimately affected by numerous organisms such as insects, fungi, animals, and bacteria where they use the decaying body as their nutrition source. These organisms can be utilized in forensic science to estimate the post-mortem interval (PMI). The post-mortem interval refers to the time that has passed since the death of a person until the body was found. Forensic entomology is one of the popular approaches where successive colonization of insects on cadaver is studied to estimate PMI. However, sometime this method does not provide consistent results due to lack of insect activities during cold environment conditions or when crime scene is indoor. Therefore, a new approach is needed to aid forensic scientists to estimate PMI. Recently, researchers have noted that microbial communities have shown a predictable and clockwise successional pattern on decomposing cadavers and suggested this could be utilized to estimate PMI when this approach is etched with other established methods. The purpose of this review is to summarize some of the studies that have been conducted on the utility of microbial communities in estimating PMI and discuss the role of microbial communities in cadaver decomposition.

Hotter-is-not-better: A study on the thermal response of a winter active and nocturnal beetle

While there are numerous examples of thermogenesis processes in poikilothermic insects that maintain a stable temperature for a certain time and in certain parts of the body, there is a lack of information on ectothermic insect species capable of remaining active under “cold” conditions that would be challenging for other species. Such a thermal strategy would imply the existence of a metabolism that can operate at different temperatures without the need to increase body temperature when experiencing cold environmental conditions. This “hotter-is-not-better“ thermal strategy is considered ancestral and conjectured to be linked to the origin and evolution of endothermy. In this study, we examined the thermal performance of a large-bodied dung beetle species (Chelotrupes momus) capable of being active during the winter nights in the Iberian Mediterranean region. Field and laboratory results were obtained using thermocamera records, thermocouples, data loggers and spectrometers that measured ultraviolet, visible and near-infrared wavelengths. The thermal data clearly indicated that this species can remain active at a body temperature of approximately 6 °C without the need to warm its body above ambient temperature. Comparing the spectrophotometric data of the species under study with that from other previously examined dung beetle species indicated that the exoskeleton of this particular species likely enhances the absorption of infrared radiation, thereby implying a dual role of the exoskeleton in both heat acquisition and heat dissipation. Taken together, these results suggest that this species has morphological and metabolic adaptations that enable life processes at temperatures that are typically unsuitable for most insect species in the region.

Study on the Comfort Properties of Knitted Fabrics Produced from Conventional and Sustainable Cotton and Polyester Fibres

Recently, the production of organic fibres and the recycling of textile waste have become essential global issues due to the decrease in non-renewable resources and the increase in disposal costs. The aim of this work was to identify changes in the properties of single jersey knitwear produced from conventional and sustainable fibres after 20 washes. The samples were knitted from different conventional and sustainable yarns. The selected conventional fibres were 100% cotton, 50% cotton-50% polyester and 100% polyester, while the sustainable fibres were 100% better cotton, 100% recycled polyester, and 50% organic cotton-50% recycled polyester. Measurements were taken before and after 20 washes according to the relevant standards. It was found that fabric produced from 100% recycled polyester is suitable for active sportswear due to its high air permeability, and resistance to heat and water vapor. In addition, the fabric with 50% organic cotton-50% recycled polyester fibres was more suitable for cold environmental conditions due to its lowest water vapor resistance, good air permeability and high thermal resistance.

Whole genome analysis of Pseudomonas mandelii SW-3 and the insights into low-temperature adaptation.

Pseudomonas mandelii SW-3, isolated from the Napahai plateau wetland, can survive in cold environments. The mechanisms underlying the survival of bacteria in low temperatures and high altitudes are not yet fully understood. In this study, the whole genome of SW-3 was sequenced to identify the genomic features that may contribute to survival in cold environments. The results showed that the genome size of strain SW-3 was 6,538,059bp with a GC content of 59%. A total of 67 tRNAs, a 34,110bp prophage sequence, and a large number of metabolic genes were found. Based on 16S rRNA gene phylogeny and average nucleotide identity analysis among P. mandelii, SW-3 was identified as a strain belonging to P. mandelii. In addition, we clarified the mechanisms by which SW-3 survived in a cold environment, providing a basis for further investigation of host-phage interaction. P. mandelii SW-3 showed stress resistance mechanisms, including glycogen and trehalose metabolic pathways, and antisense transcriptional silencing. Furthermore, cold shock proteins and glucose 6-phosphate dehydrogenase may play pivotal roles in facilitating adaptation to cold environmental conditions. The genome-wide analysis provided us with a deeper understanding of the cold-adapted bacterium.

Presenting the best correlation relationship for predicting the dynamic viscosity of CuO nanoparticles in ethylene glycol -water base fluid using response surface methodology

The types of correlation relationships by different models for predicting of the dynamic viscosity of CuO nanoparticles (NPs) in the ethylene glycol (EG) (80 %)-Water (20 %) base fluid (BF) by using response surface methodology (RSM) statistical method under temperature conditions of T = 15 to 50 °C, solid volume fractions of SVF = 0.05 to 1 % and shear rate SR = 26.6 to 933.1 s−1 were investigated. Models of Quadratic, Cubic, 2FI and Quartic were investigated. These different models were analyzed based on the measurement criteria such as Correlation deviation, coefficient of determination, standard deviation, reliability and P-values; there are important parameters that were used to compare the models. Among these four models, the Quartic model has been chosen as superior model and used to optimize nanofluid (NF) viscosity. The optimization was done in cold environmental conditions and SVF, T, SR variables and viscosity were selected as minimum values and applied to the system. In the conditions of T = 25.303 °C, SVF = 0.05 % and SR = 26.660 sec-1, most optimal NF viscosity value was 8.565 mPa.sec.

Selection and validation of reliable reference genes for quantitative real-time PCR in Barnyard millet (Echinochloa spp.) under varied abiotic stress conditions

Quantitative real-time polymerase chain reaction (RT-qPCR) using a stable reference gene is widely used for gene expression research. Barnyard millet (Echinochloa spp.) is an ancient crop in Asia and Africa that is widely cultivated for food and fodder. It thrives well under drought, salinity, cold, and heat environmental conditions, besides adapting to any soil type. To date, there are no gene expression studies performed to identify the potential candidate gene responsible for stress response in barnyard millet, due to lack of reference gene. Here, 10 candidate reference genes, Actin (ACT), α-tubulin (α-TUB), β-tubulin (β-TUB), RNA pol II (RP II), elongation factor-1 alpha (EF-1α), adenine phosphoribosyltransferase (APRT), TATA-binding protein-like factor (TLF), ubiquitin-conjugating enzyme 2 (UBC2), ubiquitin-conjugating enzyme E2L5 (UBC5) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), were selected from mRNA sequences of E. crus-galli and E. colona var frumentacea. Five statistical algorithms (geNorm, NormFinder, BestKeeper, ΔCt, and RefFinder) were applied to determine the expression stabilities of these genes in barnyard millet grown under four different abiotic stress (drought, salinity, cold and heat) exposed at different time points. The UBC5 and ɑ-TUB in drought, GAPDH in salinity, GAPDH and APRT in cold, and EF-1α and RP II in heat were the most stable reference genes, whereas ß-TUB was the least stable irrespective of stress conditions applied. Further Vn/Vn + 1 analysis revealed two reference genes were sufficient to normalize gene expression across all sample sets. The suitability of identified reference genes was validated with Cu-ZnSOD (SOD1) in the plants exposed to different abiotic stress conditions. The results revealed that the relative quantification of the SOD1 gene varied according to reference genes and the number of reference genes used, thus highlighting the importance of the choice of a reference gene in such experiments. This study provides a foundational framework for standardizing RT-qPCR analyses, enabling accurate gene expression profiling in barnyard millet.

Comparative Evaluation and Multi-Objective Optimization of Cold Plate Designed for the Lithium-Ion Battery Pack of an Electrical Pickup by Using Taguchi–Grey Relational Analysis

It is aimed to minimize carbon emissions and the spread of electric vehicles is supported for a more sustainable future. To increase the safety and life of these vehicles, cooling systems are added and developed to their energy storage systems. The aim of this study is to design and optimize the cooling plate for the lithium-ion battery pack used in a lightweight commercial electrical vehicle. Multi-objective optimization using Taguchi–grey relational analysis was performed by considering maximum temperature, the standard deviation of temperature, and pressure drop for the design of the cold plate. Channel number, channel height, and mass flow rate values were determined as parameters to be examined, and three different levels were selected for each parameter. Analysis was performed using water and 25% and 50% ethylene glycol–water solutions, which can work under sub-zero environmental conditions, employed as cooling fluid. It is shown that increasing the ethylene glycol ratio in the coolant allows it to work in colder environmental conditions, it is relatively worsening thermal performances in the cold plate applications. A new empirical correlation is proposed to predict the Nusselt number for the three coolants under all geometric and operating conditions considered in this study. Statistical analysis shows that the number of channels is the most effective parameter for the relatively low and homogenous temperature distribution on the cold plate surface. A sensitivity analysis was performed for Reynolds number ranges from 2500 to 15,000 using the optimum configurations of the three coolant fluids. It is shown that the same cooling effects could be obtained by using 1.56 times and 2.66 times more mass flow rates for 25% and 50% ethylene glycol–water solutions, respectively, compared to the water. However, rising mass flow rates result in a significant increase in the required pumping power.

Combined Effects of Ambient PM2.5 and Cold Exposure on the Development of Metabolic Disorder

The coexistence of temperature changes and air pollution poses a severe global environmental issue, exacerbating health burdens. The aim of this study was to clarify the combined effects of ambient PM2.5 and cold exposure on the development of metabolic disorders. Male C57BL/6 mice were randomly divided into four groups: TN-FA, TN-PM, TC-FA and TC-PM. The mice were then exposed to concentrated PM2.5 or filtered air (FA) under normal (22 °C) or cold (4 °C) environment conditions for 4 weeks. Metabolic-disorder-related indicators, blood pressure, serous lipids, fasting blood glucose and insulin, energy metabolism, mitochondria and protein expression in tissues were detected for comprehensively assessing metabolic disorder. The results showed that, compared to being exposed to PM2.5 only, when mice were exposed to both PM2.5 and the cold (non-optimal), they exhibited more significant metabolic disorders regarding glucose tolerance (p < 0.05), insulin resistance (p < 0.05), lipid metabolism, adipocytes (p < 0.01) and mitochondrial function. This study suggested that a cold environment might substantially exacerbate PM2.5-induced metabolic disorder. The interaction between temperature changes and air pollution implied that implementing the necessary environment-related policies is a critical and complex challenge.

Estimating climate-driven phenology shifts and survey availability using fishery-dependent data

Environmental changes are predicted to impact fish ecology; specifically, the phenology of spawning and larval settlement, resulting adult and larval movement, and ultimately seasonal habitat utilization. Hence, warm or cold environmental conditions may cause early or late seasonal movement among habitats. However, resource surveys are typically designed to occur at approximately the same time each year, and this mismatch in timing between survey sampling and fish movement can cause a different proportion of population biomass to be available to the survey in different years. In this study, we demonstrate an application to minimize such impacts using yellowfin sole (Limanda aspera) in the eastern Bering Sea as a case study. We employedfishery-dependent catch-and-effort (also called catch per unit effort (CPUE)) datacollected by observers on commercial vessels, which covered the months of March-October (whereas survey data were limited to June-August). We built a seasonal spatio-temporal model so that seasonal distribution could be used to better explain summer survey availability and movement timing as impacted by interannual temperature changes. Our results highlight (i) spawning movement phenology occurs earlier during warm years than cold years, (ii) spatial distribution is more constrained and biomass is lower during cold years than warm years, (iii) fish were more available to the summer survey during warm years than cold years, and (iv) phenology differed by sex with males staying longer on the spawning grounds than females. Finally, we computed an overlap index between the survey area and fishery CPUE data to be used as a catchability covariate within the yellowfin sole stock assessment. This index confirmed the changes in relative availability of this species by year as presently used in the assessment.

Investigation of the effects of various parameters and the evaluation of the optimal rheological of MWCNTs based hybrid nanolubricant and providing an optimal model

The rheological behavior of MWCNT-Al2O3 (10%−90%) / SAE40 oil hybrid nanofluid (HNF) is done with using RSM statistical method in this study. The investigation is carried out under conditions of temperature within the range T = 25–50 °C, solid volume fraction between SVF= 0.0625 until 1% and shear rate in the range of SR= 666.5–9331 s−1. In this study, three different models of 2FI, Quadratic and Cubic are evaluated using correlation indices and quality determination charts. Cubic model is chosen as the optimal model among these models and for optimization, the viscosity of HNF is used. The values of R2, C.V, C.D, P-value and Std. Dev correlation indices for the selected model are 0.9996, 1.04, −3.785 <C.D %< 4.333, 2.55e-264 and 2.12, respectively. The effects of SVF, temperature and SR parameters on viscosity are investigated. It is found that SR has the least effect and temperature has the most effect on the viscosity of HNF. Lubrication is performed for cold environment conditions. The parameters of SVF, SR, temperature and viscosity are considered at the minimum value. After performing the optimization process by DOE, the most optimal mode for the HNF viscosity is in T = 35.210°C, SVF= 0.063%, SR= 666.511 s−1 and the viscosity is 191.450 mPa.sec.

Using the RSM to evaluate the rheological behavior of SiO2 (60%) - MWCNT (40%)/SAE40 oil hybrid nanofluid and investigating the effect of different parameters on the viscosity

The present study predicts dynamic viscosity of SiO2 (60%) - MWCNT (40%) hybrid nanofluid (HNF) in SAE40 oil as base fluid (BF) by comparing various models of RSM. This study was conducted under laboratory conditions with solid volume fractions of SVF= 0–1%, temperature of T = 25–50 °C and shear rates of SR= 666.5–9331 s−1. Different models were used for this study, including 2FI, Quadratic, Cubic and Quartic models. These models were evaluated based on a series of quality indicators and charts. The indicators that were investigated in this study include standard deviation, coefficient of determination, P-value, correlation deviation (C.D) and coefficient of variation. After checking the quality indicators and charts for different models, the Quartic model was selected as the optimal model. In this study, the correlation functions of various models were used to determine the viscosity of HNFs. Then, according to the evaluation of the models, the Quartic model has been selected as the optimal model. The correlation function presented for the Quartic model has an acceptable accuracy in predicting the viscosity values of HNFs compared to the experimental data. Also, due to the dependence of viscosity on SR, the behavior of HNF is non-Newtonian. The values of standard deviation, coefficient of determination, P-value, correlation deviation, and coefficient of variation for the selected model were 6.67, 0.9960, 1.548584974e-218, − 4. 760 <C.D< 8.551 and 3.48, respectively. Next, the viscosity of HNF was optimized for the selected model in cold environmental conditions. The best state of viscosity of HNF in the cold environment in the conditions of SVF= 0, T = 31.958 °C and SR= 666.500 s−1 was 216.978 mPa.sec. Next, the different parameters effect on the viscosity of HNF was investigated and it has been determined that the temperature and SR parameters have the greatest and least effect on the viscosity of HNF, respectively. The findings can help to better understanding of rheological behavior of HNF and SAE40 engine oil in cold environmental conditions. By using the correlation function provided in the selected model, the viscosity of HNF can be calculated at any temperature, SVF and SR. This saves time and money and helps a lot to the industries that use this HNF and SAE40 engine oil.

Transcriptome and functional analysis revealed the intervention of brassinosteroid in regulation of cold induced early flowering in tobacco.

Cold environmental conditions may often lead to the early flowering of plants, and the mechanism by cold-induced flowering remains poorly understood. Microscopy analysis in this study demonstrated that cold conditioning led to early flower bud differentiation in two tobacco strains and an Agilent Tobacco Gene Expression microarray was adapted for transcriptomic analysis on the stem tips of cold treated tobacco to gain insight into the molecular process underlying flowering in tobacco. The transcriptomic analysis showed that cold treatment of two flue-cured tobacco varieties (Xingyan 1 and YunYan 85) yielded 4176 and 5773 genes that were differentially expressed, respectively, with 2623 being commonly detected. Functional distribution revealed that the differentially expressed genes (DEGs) were mainly enriched in protein metabolism, RNA, stress, transport, and secondary metabolism. Genes involved in secondary metabolism, cell wall, and redox were nearly all up-regulated in response to the cold conditioning. Further analysis demonstrated that the central genes related to brassinosteroid biosynthetic pathway, circadian system, and flowering pathway were significantly enhanced in the cold treated tobacco. Phytochemical measurement and qRT-PCR revealed an increased accumulation of brassinolide and a decreased expression of the flowering locus c gene. Furthermore, we found that overexpression of NtBRI1 could induce early flowering in tobacco under normal condition. And low-temperature-induced early flowering in NtBRI1 overexpression plants were similar to that of normal condition. Consistently, low-temperature-induced early flowering is partially suppressed in NtBRI1 mutant. Together, the results suggest that cold could induce early flowering of tobacco by activating brassinosteroid signaling.

Climate fluctuations during the Ordovician-Silurian transition period in South China: Implications for paleoenvironmental evolution and organic matter enrichment

The Ordovician-Silurian (OS) transition witnessed dramatic tectonic, climatic, marine, and biological coevolution, during which organic-rich black shale was widely deposited and is considered an important source rock. However, the potential links between the differential enrichment pattern of organic matter and climate fluctuations and paleoenvironmental evolution during this period are still unclear. In this paper, the Late Ordovician-early Silurian black shale in a JieLong (JL) section in South China was identified by graptolitic fossils, total organic carbon (TOC) content, X-ray diffraction (XRD), scanning electron microscopy (SEM) and geochemical analysis. The results show that the provenances of sedimentary rocks are all granodiorite-like. According to the variations in the TOC content and geochemical indicators, four layers are delineated. Under warm and humid climatic conditions, sea level rise and unstable seasonal upwelling led to Unit 1 organic matter enrichment controlled by high primary productivity, anoxic conditions and effective smectite production. Unit 2 organic matter burial was controlled by cold, arid and oxic environmental conditions, but primary productivity was still relatively high. After the end of the glacial period, warm and humid climatic conditions and rapid transgression were the main factors affecting the burial of organic matter in Unit 3. Under hot and humid climate conditions, higher terrigenous detrital inputs and unfavourable preservation environments, the dilution of organic matter in Unit 4 was accelerated. The corrected chemical index of alteration (CIAcorr) values show that the study area experienced a climate change of alternating cold and warm conditions in response to the climate fluctuation during the glacial-interglacial period. The CIAcorr value is negatively correlated with the TOC content, while the generation of available clay minerals (smectite) in warm and humid climates is usually consistent with the enhanced burial flux of organic matter, supporting the important role of climate fluctuations in the accumulation of organic matter. Finally, a comparison of the data from the present study with geochemical data from different profiles in South China reveals the role of climatic fluctuations during the OS transition in controlling paleoenvironmental evolution and organic matter enrichment, while such a heterogeneous factor is usually associated with global or regional geological events. Our study highlights this differential enrichment mechanism as a combined response of multiple factors and provides important implications for glacial-interglacial organic matter enrichment mechanisms.

Flexible Stretchable, Dry-Resistant MXene Nanocomposite Conductive Hydrogel for Human Motion Monitoring.

Conductive hydrogels with high electrical conductivity, ductility, and anti-dryness have promising applications in flexible wearable electronics. However, its potential applications in such a developing field are severely hampered by its extremely poor adaptability to cold or hot environmental conditions. In this research, an "organic solvent/water" composite conductive hydrogel is developed by introducing a binary organic solvent of EG/H2O into the system using a simple one-pot free radical polymerization method to create Ti3C2TX MXene nanosheet-reinforced polyvinyl alcohol/polyacrylamide covalently networked nanocomposite hydrogels (PAEM) with excellent flexibility and mechanical properties. The optimized PAEM contains 0.3 wt% MXene has excellent mechanical performance (tensile elongation of ~1033%) and an improved modulus of elasticity (0.14 MPa), a stable temperature tolerance from -50 to 40 °C, and a high gauge factor of 10.95 with a long storage period and response time of 110 ms. Additionally, it is worth noting that the elongation at break at -40 °C was maintained at around 50% of room temperature. This research will contribute to the development of flexible sensors for human-computer interaction, electronic skin, and human health monitoring.

Environmental variation in the early and middle Holocene Tequendama and Aguazuque archaeological sites, Colombia

This study focuses on identifying possible environmental variations and plant availability during the occupation in two archaeological sites: Tequendama and Aguazuque, located in Sabana de Bogotá, Colombia. Those sites represent periods of occupation during the early to middle Holocene that contributes valuable information about hunter-gatherers who occupied this area. Data obtained and recovered archaeological material during excavations shed light on relatively continuous occupations until the late Holocene. The presence of lithic artefacts, human and fauna bone remains offered relevant information to comprehend social dynamics among these human groups; likewise, phytolith and stable isotope analysis on sediments and fauna were carried out to identify environmental variations, and the presence of plant remains in these archaeological contexts. Carbon isotope analysis in sediments indicated the prevalence of plants C3 from the early Holocene. In turn, isotopic relationships in carbon obtained from mammals’ dental enamel found in both sites suggest that those animals consumed such types of plants. Also, isotopic values in oxygen from dental enamel show humid and possibly cold environmental conditions in both locations. Also, phytolith analyses provide evidence on the types of plants available in determined contexts and reconstruct environments, use, and availability. Those three types of analysis were applied to archaeological contexts to determine the presence of plants type C3 or C4 available in the sites, which permitted to evidence of environmental changes, humid conditions, and, in a few cases, drought across occupation, as well as the differences in terms of the presence or absence of certain types of plants during chronological periods, suggesting a possible association of horticultural processes and domestication during middle Holocene in Aguazuque archaeological site.

A comparative study of RSM regression models to achieve the most optimal rheological behavior of MWCNT/SiO2(50−50)-SAE40 hybrid nanofluid and provide optimal lubrication conditions during the start of movement

In this statistical study, the performance of MWCNT-SiO2(50−50)/SAE40 hybrid nanofluid (HNF) was investigated and compared with different regression models. The purpose of this study is to determine and present the best function of the modeler in predicting the objective function in accordance with the quality indicators of RSM for the cold environmental conditions of lubrication (or the equivalent of starting). The study was carried out in laboratory conditions with temperature range T = 25–55 °C, solid volume fraction SVF= 0.0625–1% and shear rate γ̇=SR= 666.5–9331 s−1. By comparing the performance of the model maker based on statistical quality indicators, it was found that the Quartic model is the most suitable model for analyzing the rheological behavior of the present HNF. To select the most optimal model, the statistical criteria of coefficient of determination, coefficient of variation (C.V), probability value and correlation deviation (C.D) were used. The values of each statistical index for the quartic model are respectively 0.9995, 1.11, 2.9956003e-246 and − 3.38%<C.D< +12.67%. According to the selected model, the optimal value of lubrication viscosity in the vehicle start-up mode is suggested as μcold= 232.815 mPa.sec in laboratory conditions T = 32.908 °C, φcold= 0.063% and γ̇cold= 666.501 s−1.

Mathematical simulation of the rheological behavior of MWCNT (20%)-ZnO (80%)/single-grade SAE50 hybrid nanofluid to introduce the most optimal correlation function and determining the optimal lubrication conditions in hot and cold environments

In the article report, the viscosity of MWCNT (20%)-ZnO(80%)/SAE50 hybrid nanofluid (HNF) is investigated by statistical approach (RSM) and comparatively. The study is carried out in laboratory conditions with temperature T = 25–50 °C, volume fraction φ = 1–0.0625% and shear rate γ ̇= 666.5–7998 s−1. The intention in this research is to identify and introduce the best function of the modeler by the standard criteria of quality measurement and also to determine the optimal mode of lubrication in cold and hot environmental conditions on a laboratory scale. Studying the thermophysical properties of HNF with a new formulation and determining the target response values in cold and hot environmental conditions (through equating with real conditions) is one of the innovations of this research. Statistical analysis has shown that the Quartic model has a stronger level of significance and predictive power compared to other models. Based on the regression analysis, the coefficient of determination (R2), correlation deviation (C.D), probability value (P-value) and reliability (C.V) for the Quartic model are respectively equal to 0.9996, − 1.89% to + 1.82%, 2.576563 e-250% and 0.96151%. Based on RSM optimization, suitable viscosities for lubrication in a cold environment (when starting the vehicle engine) and a hot environment (in motion mode) are suggested as 284.777 and 226.910, respectively.