Theanine, polyphenols, and caffeine not only affect the flavor of tea, but also play an important role in human health benefits. However, the specific regulatory mechanism of Se NMs on fat-reducing ...components is still unclear. In this study, the synthesis of fat-reducing components in Fuding Dabai (FDDB) tea was investigated. The results indicated that the 100-bud weight, theanine, EGCG, total catechin, and caffeine contents of tea buds were optimally promoted by 10 mg·L
Se NMs in the range of 24.3%, 36.2%, 53.9%, 67.1%, and 30.9%, respectively. Mechanically, Se NMs promoted photosynthesis in tea plants, increased the soluble sugar content in tea leaves (30.3%), and provided energy for the metabolic processes, including the TCA cycle, pyruvate metabolism, amino acid metabolism, and the glutamine/glutamic acid cycle, ultimately increasing the content of amino acids and antioxidant substances (catechins) in tea buds; the relative expressions of key genes for catechin synthesis,
,
,
,
,
,
,
, and
, were significantly upregulated by 45.1-619.1%. The expressions of theanine synthesis genes
,
, and
were upregulated by 138.8-693.7%. Moreover, Se NMs promoted more sucrose transfer to the roots, with the upregulations of
,
,
, and
by 125.8-560.5%. Correspondingly, Se NMs enriched the beneficial rhizosphere microbiota (
,
,
,
, and
), enhancing the absorption and utilization of ammonium nitrogen by tea plants, contributing to the accumulation of theanine. This study provides compelling evidence supporting the application of Se NMs in promoting the lipid-reducing components of tea by enhancing its nitrogen metabolism.
Strategies to reduce the risk of drought damage are urgently needed as intensified climate change threatens agricultural production. One potential strategy was using nanomaterials (NMs) to enhance ...plant resistance by regulating various physiological and biochemical processes. In the present study, 10 mg kg
manganese ferrite (MnFe
O
) NMs had the optimal enhancement to elevate the levels of biomass, photosynthesis, nutrient elements, and polysaccharide in rice by 10.9-525.0%, respectively, under drought stress. The MnFe
O
NMs were internalized by rice plants, which provided the possibility for rice to better cope with drought. Furthermore, as compared with drought control and equivalent ion control, the introduction of MnFe
O
NMs into the roots significantly upregulated the drought-sensing gene
(29.4%) and the receptor gene
(59.9%). This activation stimulated downstream abscisic acid, proline, malondialdehyde, and wax biosynthesis by 23.3%, 38.9%, 7.2%, and 26.2%, respectively. In addition, 10 mg·kg
MnFe
O
NMs significantly upregulated the relative expressions of
,
,
,
, and
, and increased IAA content significantly, resulting in an enlarged root angle and a deeper and denser root to help the plant withstand drought stresses. The nutritional quality of rice grains was also improved. Our study provides crucial insight for developing nano-enabled strategies to improve crop productivity and resilience to climate change.
Maximizing the potential of plant–microbe systems offers great opportunities to confront sustainability issues in agroecosystems. However, the dialog between root exudates and rhizobacteria remains ...largely unknown. As a novel nanofertilizer, nanomaterials (NMs) have significant potential to improve agricultural productivity due to their unique properties. Here, soil amendment with 0.1 mg·kg−1 selenium (Se) NMs (30–50 nm) significantly promoted rice seedling growth. Differences in root exudates and rhizobacteria were evident. At an earlier time point (3rd week), Se NMs increased the relative content of malic and citric acid by 15.4- and 8.1-fold, respectively. Meanwhile, the relative abundances of Streptomyces and Sphingomonas were increased by 164.6 % and 38.3 %, respectively. As the exposure time increased, succinic acid (40.5-fold) at the 4th week and salicylic acid (4.7-fold) and indole-3-acetic (7.0-fold) at the 5th week were enhanced, while Pseudomonas and Bacillus increased at the 4th (112.3 % and 50.2 %) and 5th weeks (190.8 % and 53.1 %), respectively. Further analysis indicated that (1) Se NMs directly enhanced the synthesis and secretion of malic and citric acids by upregulating their biosynthesis and transporter genes and then recruited Bacillus and Pseudomonas; (2) Se NMs upregulated the chemotaxis and flagellar genes of Sphingomonas for more interaction with rice plants, thereby promoting rice growth and stimulating root exudate secretion. This crosstalk of root exudates and rhizobacteria enhanced nutrient uptake, resulting in promoted rice growth. Our study offers insights into the crosstalk between root exudates and rhizobacteria by NMs and provides new insights into rhizosphere regulation in nano-enabled agriculture.
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•Se NMs enhanced synthesis and secretion of organicorganic acids and recruited Bacillus and Pseudomonas in rhizosphere.•Se NMs upregulated chemotaxis and flagellar genes of Sphingomonas for more interact with roots.•The crosstalk of root exudates and rhizobacteria altered by Se NMs increased nutrient uptake and promoted rice growth.
•Accelerated pavement testing (APT) on pre-cracked inverted asphalt pavement (IAP).•Simulating semirigid subbase crack with cohesive element as structural component.•Measuring the tire-pavement ...contact characteristics of loaded truck tires by HVS.•Estimating CTB crack stiffness at different cracking stages.•Validating the IAP FE model with falling weight deflectometer test results in APT.
Typical inverted asphalt pavement (IAP) finite element (FE) models consider the semirigid subbase as an intact slab. Quarter IAP FE models with cracks in the subbase are developed to include the effect of cracks on pavement responses. To facilitate the model validation, heavy vehicle simulator (HVS) accelerated pavement testing (APT) and falling weight deflectometer (FWD) tests are conducted on four instrumented IAP test sections with transverse cracks sawed into the top of the subbase. The crack is simulated with cohesive elements, and the loading part geometry and dimension are determined by measuring the tire-pavement contact characteristics of the HVS dual-wheel carriage. The minimum mesh size of 0.01 m is specified in the convergence analysis. Dimension validity analysis results illustrate that the quarter model cannot represent the overlapping effect of the dual-wheel loads along the depth direction. FWD tests simulation and P-value results of paired T-tests between the simulated and measured pavement responses indicate that the FE model developed in the study can replicate the actual pavement response well. The model is valid for the pavement testing simulation of IAP with cracks in the subbase.
Bisphenol A (BPA), a suspected endocrine disruptor, can modify normal plant growth and development. Photosynthesis provides material and energy for the growth and development of plants, in which ...chlorophyll (Chl) plays a significant role. Many studies have shown that the growth and metabolism of plants vary at different growth stages. Thus the sensitivity of plant's responses to environmental pollution is correspondingly different. We studied the effects of BPA on the Chl contents of soybean (Glycine Max L.) at different growth stages (seedling, flowering and podding, seed-filling and maturation) by measuring the contents of essential intermediates (5-aminolevulinic acid, porphobilinogen, protoporphyrin IX, magnesium protoporphyrin and protochlorophyll) and the activities of key enzymes (5-aminolaevulinic acid dehydratase, porphobilinogen deaminase, uroporphyrinogen III synthase, magnesium chelatase) in chlorophyll synthesis. Low-dose (1.5 mg/L) BPA exposure increased the activities of key enzymes in addition to the contents of intermediates in Chl synthesis at different growth stages, resulting in increases in Chl contents and net photosynthetic rate. In contrast, medium and high-dose (17.2, 50.0 mg/L) BPA exposure produced inhibitory effects on the indices. Following the withdrawal of BPA exposure, the indices recovered to a degree that was related to the plant growth stage. The effect level (high to low) of BPA on these indices at different growth stages was: seedling stage > maturation stage > flowering and podding stage > seed-filling stage. The reverse effect was observed following the withdrawal of BPA exposure. The responses of key enzymes in plant Chl synthesis to BPA illustrate how BPA affects Chl contents. The effects of BPA show clear differences at different plant growth stages.
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•BPA affected Chl contents by regulating key enzymes in the Chl synthesis process.•Low/high-dose BPA promoted/inhibited key enzymes in a dose-dependent manner.•Effects of BPA on key enzymes in Chl synthesis varied at different growth stages.
BPA affected Chl contents by regulating the key enzymes in Chl synthesis and the effects showed differences at different plant growth stages.
This study investigated the effects of moderate daily temperature variations on reflective cracking in asphalt concrete (AC) overlays on Portland cement concrete (PCC) pavements using ...three-dimensional (3D) finite element (FE) modeling. The FE model consists of an AC overlay on top of PCC slabs, followed by aggregate base and subgrade. The year-round temperature variations were divided into discrete groups using a clustering technique and each group was applied separately in the FE model. The maximum stress and strain values associated with each temperature variation group were determined using the FE model and used as the driving force corresponding to the thermally induced damage in the AC overlay. The results show that the maximum stress and strain values in the overlay depend on the hourly temperature variation as well as the seasonal temperature profile. The daily temperature variation controls the deformation of the underlying PCC slabs, whereas the seasonal temperature profile determines the viscoelastic properties of the AC overlay. The estimated maximum tensile stress and strain values suggest that the AC overlay is primarily subjected to damage from repetitive thermal loading instead of one-time fracture events for moderate temperature variations. In addition, when the AC overlay is fully bonded to the PCC slabs, the thermal strains are much greater than the traffic induced strains, indicating a high possibility of thermal reflective cracking being the dominant damage mechanism for these cases.
In this study, a three-dimensional (3D) finite element model (FEM) consisting of an asphalt concrete (AC) overlay on top of jointed plain Portland cement concrete (PCC) slabs was developed to ...investigate the mechanism of the crack initiation of traffic-induced reflective cracking. Strain values at the bottom of AC overlay were the primary response obtained from the simulation results to represent the damage induced in the AC layer. Different bonding situations between the two layers, traffic load locations, material properties and thicknesses of the AC layer were taken into consideration. The analysis results show that the dominating strain for damage is dependent on the bonding condition between the AC and PCC layers. When the AC layer is completely bonded with the PCC layer, the damage will initiate firstly at the top of the joint corner between the PCC slabs to deteriorate the bonding, then the AC bottom will be susceptible to bending strain. It was observed that the most critical load location for modeling the case of fully bonded overlays is related to the AC thickness while in the case of partially bonded overlays, the most critical load location is always located on the top of one side of the PCC joint.
Bisphenol A (BPA) is an emerging environmental endocrine disruptor that has toxic effects on plants growth. Photosynthesis supplies the substances and energy required for plant growth, and regulated ...by stomatal and non-stomatal factors. Therefore, in this study, to reveal how BPA affects photosynthesis in soybean seedlings (Glycine max L.) from the perspective of stomatal and non-stomatal factors, the stomatal factors (stomatal conductance and behaviours) and non-stomatal factors (Hill reaction, apparent quantum efficiency, Rubisco activity, carboxylation efficiency, the maximum Rubisco carboxylation velocity, ribulose-1,5-bisphospate regeneration capacities mediated by maximum electron transport rates, and triose phosphate utilization rate) were investigated using a portable photosynthesis system. Moreover, the pollution of BPA in the environment was simulated. The results indicate that low-dose BPA enhanced net photosynthetic rate (Pn) primarily by promoting stomatal factors, resulting in increased relative growth rates and accelerated soybean seedling growth. High-dose BPA decreases the Pn by simultaneously inhibiting stomatal and non-stomatal factors, and this inhibition decreases the relative growth rates further reducing soybean seedling growth. Following the withdrawal of BPA, all of the indices were restored to varying degrees. In conclusion, low-dose BPA increased the Pn by promoting stomatal factors while high-dose BPA decreased the Pn by simultaneously inhibiting stomatal and non-stomatal factors. These findings provide a model (or, hypothesis) for the effects of BPA on plant photosynthesis.
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•BPA affected photosynthesis by changing stomatal and non-stomatal factors.•Low/high-dose BPA improved/inhibited stomatal and non-stomatal factors.•Observation of stomata showed the mechanism of BPA on plant photosynthesis directly.•A model is proposed for one pathway of BPA's effect on plant photosynthesis.
Fatigue cracking is the most common distress in asphalt pavements. Currently, no performance-related laboratory tests exist for fatigue cracking to use in routine asphalt mix design to approve job ...mix formula (JMF) or quality control and quality assurance (QC/QA) in California. The existing four-point bending (4PB) test was developed to evaluate the fatigue performance of asphalt materials, but it is not necessarily appropriate for use in routine JMF, and it takes too long to complete for QC/QA. The first objective of this doctoral dissertation is to evaluate potential surrogate fatigue performance-related testing methods and identify a test that is simple and easy to perform and also provides a guidance for asphalt mix design on routine projects and for QC/QA on all projects.Potential performance-related tests evaluated in this study included monotonic loading fracture tests: semicircular bend (SCB) test, indirect tensile asphalt cracking test (IDEAL-CT), and repeated loading fatigue testing on fine aggregate matrix (FAM) mixes with linear amplitude sweep (LAS) testing configuration. These tests were conducted on a variety of asphalt materials, and they were assessed based on simplicity, repeatability (variability), and their relationship to flexural stiffness and fatigue life from 4PB tests.Fracture parameters obtained from SCB tests and IDEAL-CT and fatigue parameters from FAM mix fatigue tests were assessed as potential fatigue cracking indicators. Linear regression analysis was performed to correlate these indicators with the initial flexural stiffness and fatigue life from 4PB tests. The regression analysis results demonstrated that the SCB tests and IDEAL-CT provided the similar fracture information. In addition, fracture parameters from SCB tests and IDEAL-CT were found to be well correlated with the initial flexural stiffness from 4PB tests. Meanwhile, the initial flexural stiffness from 4PB tests showed a moderate nonlinear correlation with the fatigue life from 4PB tests.Among all fracture parameters, material strength obtained from IDEAL-CT was found to have low variability, strong correlation with flexural stiffness and a moderate correlation with fatigue life from 4PB tests, therefore, strength was proposed as a surrogate indicator for flexural stiffness and an indication of fatigue performance. The relationship identified in this study between flexural stiffness and flexural fatigue life, and the one between flexural stiffness and material strength from IDEAL-CT were used to develop a preliminary specification for fatigue performance. The strength from IDEAL-CT should meet both upper and lower specification limits to ensure required fatigue performance met for asphalt mixtures. However, since there was no strong relationship found directly between strength from IDEAL-CT and fatigue life from 4PB tests, fracture tests did not provide sufficient information to predict fatigue life performance.The repeated loading FAM mix fatigue test showed promising comparison results with both initial flexural stiffness and fatigue life from 4PB tests. The comparison between master curves of FAM shear stiffness and the ones of full graded hot mix asphalt (HMA) flexural stiffness indicated that FAM mixes were more sensitive to temperature and loading frequency than HMA as expected because of higher binder contents in FAM mixes. Linear correlations with R2 values of 0.63 and 0.59 were found between FAM shear stiffness and HMA flexural stiffness at intermediate frequencies (100 Hz and 10 Hz) at a reference temperature of 20 °C. In addition to the comparison between flexural stiffness of HMA and shear stiffness of FAM mixes, the dynamic compressive stiffness of HMA obtained from the asphalt mixture performance tester (AMPT) was also included to explore the effect of different loading configurations on the relationship between HMA stiffness and FAM mix stiffness. The shear stiffness of FAM and dynamic compressive stiffness of HMA were found to be moderately correlated at frequencies of 1 Hz, 10 Hz, 100 Hz and 1000 Hz. Furthermore, these three different types of stiffness: flexural stiffness of HMA, dynamic compressive modulus of HMA and shear stiffness of FAM mixes also indicated that the addition of rejuvenator to asphalt materials containing up to 50% RAP effectively reduced the stiffnesses almost to the same level of the virgin control mix. Given these findings, an attempt was made to upscale the shear stiffness of FAM mixes to the flexural stiffness and dynamic moduli of HMA with two methods. The comparison between predicted and measured moduli showed that the shear stiffness of FAM mixes provided reasonable estimates of both flexural stiffness and dynamic modulus of HMA at intermediate frequencies (1 to 10 Hz) with the error percentage less than 10%. On the other hand, overprediction was noted from both methods at higher frequencies.The comparison of fatigue performance between HMA and FAM mix was further investigated based on damage curves. The viscoelastic continuum damage (VECD) model, which depicts the reduction of material integrity under repeated loading as a function of damage accumulated in asphalt materials, was used to formulate damage curves based on the FAM LAS testing results and HMA 4PB fatigue testing results. Comparison results demonstrated that similar damage characteristics were observed between HMA and FAM mixes. The FAM mixes also showed lower material integrity at failure compared to the values of HMA mixtures, which indicated that FAM mixes were more damage tolerant than HMA. In addition to the VECD model, the FAM mix fatigue testing results also showed a good fitting result on the damage model implemented in the California Mechanistic Empirical pavement design software (CalME). Similar ranking result among the CalME damage curves of different material types was found between FAM mix and HMA.Based on this study, it seems promising that FAM mix fatigue testing can be developed to supplement/replace 4PB fatigue testing on HMA due to its relatively more economical, faster and simpler procedure than conventional 4PB tests. More importantly, linear regression analyses on the selected fatigue parameters from FAM mix LAS fatigue test results and HMA 4PB fatigue results indicated that there was a strong correlation between the shear strain value at failure of FAM mixes and the strain value corresponding to one million cycles of fatigue life of HMA. The shear strain value at the failure of FAM mixes also showed a low variability with a coefficient of variation (COV) of 11.2%, therefore, the FAM mix LAS fatigue testing with the fatigue parameter of shear strain value at failure was recommended as a promising surrogate test for 4PB tests on HMA.Fatigue performance was then studied in the context of pavement structure, which is the second objective of this dissertation: develop numerical models using finite element method (FEM) with the software ABAQUSTM to estimate the pavement responses under traffic loading and daily thermal variation. Specifically, composite pavements containing of an asphalt concrete (AC) overlay on top of portland cement concrete (PCC) slabs was taken into consideration to investigate both traffic loading-induced and thermal loading-induced fatigue cracking or reflective cracking performance in this study. As this study only focused on the damage and crack initiation stage of reflective cracking, terms of fatigue cracking and reflective cracking were used in an interchangeable manner.FEM was firstly applied to investigate the impacts from the pavement bonding condition between AC overlays and PCC slabs, tire loading location, pavement material properties and joint properties between PCC slabs on the pavement response under traffic loading. The tensile strain value at the bottom of the AC overlay was considered as the primary fatigue damage parameter. A preliminary simulation study showed that the critical strain type that causes damage in the AC layer was dependent on the bonding condition between the AC overlay and the PCC layer. When the AC overlay is fully bonded with the PCC slabs, debonding between the AC and PCC layers will firstly take place due to the separating tension, and the damage is expected to initiate at the bottom of the AC layer above the joint corner between two PCC slabs. When the debonding area forms and starts to expand between the AC and PCC layers, damage in the AC overlay will then be primarily caused by the bending tensile strain at the bottom of the AC overlay.A full factorial with 2,700 simulation cases was then carried out with varying AC thickness, AC stiffness, bonding condition, stiffness of base layers (k-value), load transfer efficiency (LTE) between PCC slabs, and traffic loading value. Due to the different damage mechanisms of fully-bonded pavement and partially-bonded pavement, two separate regression models were established based on the simulation results to predict the maximum principal tensile strain. The comparison between the predicted strain value from these two models and the value obtained from FEM simulations demonstrated the accuracy of the regression models.In addition to traffic induced reflective cracking, the daily temperature variation induced reflective cracking was also investigated. In contrast to extreme cold temperatures which cause one time fracture cracking, moderate temperatures can induce repeated tensile strain and stress in the AC overlay all year around due to daily temperature variation, which is a more common situation in California. To address potential thermal reflective cracking under moderate temperatures, composite pavement structures under only thermal loading were simulated with FEM, and the critical thermal stress and strain values were calculated. Among the selected six climate regions, the yearly temperature parameters (average yearly maximum, average yearly minimum and average seasonal change) and daily
