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Temperature is the most significant abiotic factor that affects the growth and behaviour of insects. However, the mechanism by which the olfactory system senses thermal stimulus and combines temperature and chemical signals to trigger certain behavioural outputs is unclear. This study aimed to clarify the mechanism by which environmental temperature affects olfactory perception in Apis cerana cerana (Hymenoptera: Apidae). We used quantitative reverse-transcriptase polymerase chain reaction and western blotting to analyse the expression of AcerOr1 and AcerOr2. We also used electroantennography (EAG) assays to detect bee antennal responses to odorants at different temperatures. The results revealed that the mRNA expression of AcerOr1 and AcerOr2 was significantly influenced by temperature. These genes exhibited both increases and decreases in expression over time, with the most significant differential observed at 25 °C. Protein expression was similarly affected at 2 hours after different temperature treatments. Electroantennography responses from the antennae revealed that six odorant volatiles – N-(4-ethylphenyl)-2-((4-ethyl-5-(3-pyridinyl)-4H-1,2,4-triazol-3-yl)thio)acetamide (VUAA1), linolenic acid, eugenol, hexyl acetate, 1-nonanol, and lauroleic acid – had the most dramatic effect at 25 °C. The results indicate that environmental factors affecting the expression of AcerOr1 and AcerOr2 modulate olfactory recognition behaviour in A. cerana cerana, suggesting that changes in environmental temperature can affect bees’ olfactory preferences.
Drawing upon research on the visual complexity effect and Dual Coding Theory, this research examined the influence of character properties and the role of individual learner differences in Chinese character acquisition. The participants included 248 Chinese-speaking children in grades 1 through 3 in Taiwan. The study extended the scope of previous research by concurrently examining two types of cognitive processing: activation of verbal codes with nonverbal codes (activation of word form) and activation of nonverbal codes with verbal codes (activation of meaning). Results revealed the asymmetry in the two types of cognitive processing. Regarding the influence of character properties, while characters with less visual complexity and with radical presence are generally more acquirable, the interaction between these two properties was only present in the activation of meaning but not the activation of word form. Individual differences contributing to character acquisition did not mirror each other in the two directions of cognitive processing either. The contribution of radical awareness and visual skills remained the same across grade levels in the activation of meaning but varied with grades and the properties of the characters in the activation of word form. The methodological and theoretical contributions of the study were discussed.
Parkinson disease (PD) is a neurological disorder that affects more than 10 million people worldwide, impacting both quality of life and marital relationships. Divorce rates are higher in Western compared to Eastern countries. However, it is unclear if there are differences in marital status after PD onset between the two regions.
Methods:
We searched MEDLINE and Embase from inception to March 31, 2024. Original studies discussing marital status in participants with PD were included. An unmarried status includes single, widowed, divorced or separated. Outcomes included the prevalence of being unmarried, measured as proportions, and the risk ratio (RR) of being unmarried in participants with PD relative to controls.
Results:
Out of 567 studies screened initially, 55 studies involving 3,723,966 participants were included. The prevalence of being unmarried was evaluated in 55 studies (25.16%; 95% CI: 21.52–29.18). The prevalence of being unmarried was significantly higher in countries in the West compared to the East (28.83%; 95% CI: 25.09–32.89 vs 17.47%; 95% CI: 12.10–24.57, p < 0.01). Compared to controls, the risk of being unmarried in PD participants after the onset of PD was significantly higher in the East (RR: 1.21, 95% CI: 0.91–1.60) compared to the West (RR: 0.87, 95% CI: 0.65–1.15).
Conclusions:
Our meta-analysis showed significantly higher rates of being unmarried in Western compared to Eastern countries. After PD onset, participants in the East were at significantly higher risk of being unmarried compared to participants in the West, suggesting that differences in cultural practices, societal norms and healthcare systems may affect marital status outcomes in PD participants.
To speed up the construction of grassroots medical and health teams in China, free training of rural order-oriented medical students was launched in June 2010. Based on the theory of policy tools, a quantitative analysis of policy texts at the national level was conducted to explore the use of policy tools and to put forward corresponding suggestions for adjustments.
Methods
From January to February 2023, the research team searched the Peking University Treasure Database and the official websites of the State Council, the National Health Commission, the Ministry of Education, and other ministries for national policy documents related to free training of order-oriented medical students published from June 2010 to May 2023. A policy tool and policy target analysis framework were used to quantitatively analyze the policy documents.
Results
A total of 16 policy documents were included and 213 policy provisions were extracted. From the perspective of policy tools, the proportion of policy provisions using imperative policy tools was the highest (63.4%), followed by advisory policy tools (18.8%). and reward-based policy tools (13.6%). Functional expansion tools (2.8%) and authoritative restructuring tools (1.4%) accounted for a relatively low proportion. The institutional education stage is the main policy target, with provisions accounting for 75 percent (162 articles), followed by the continuing education stage (17.6%; 38 articles), and the postgraduate education stage (7.4%; 16 articles).
Conclusions
The distribution of policy tools for the free training policy of rural order-oriented medical students in China needs to be balanced, and the internal combination of the same policy tools needs to be optimized. The policy targets were mainly concentrated in the education stage of universities.
With the aging population, chronic diseases have become a serious threat to public health in China. Adhering to the doctor’s advice is an effective strategy for controlling chronic diseases, and the preferences of patients with chronic disease has an important impact on compliance with medication. However, there is insufficient research exploring this aspect.
Methods
In this study patients with chronic disease were selected by stratified random sampling to participate in a survey carried out in three cities of a province in eastern China. The discrete choice experiment used a questionnaire of D-efficiency experimental design to measure the medication choices of patients with chronic disease. The main attributes included drug price, onset of action, adverse reactions, traditional Chinese or Western medicine, domestic drug, and reimbursed by medical insurance. The data were analyzed using a mixed logit model.
Results
A total of 1,062 valid questionnaires were received. The 1,045 questionnaires that passed the consistency test covered three prefecture-level cities, nine counties, and 216 villages. All drug attributes were statistically significant for selection preferences. The preference of patients in rural areas with chronic disease was “quick onset of action” (β=2.491), “Western medicine” (β=0. 826), “medical insurance” (β=0.556), “domestic drugs” (β=0.286), and “very few adverse reactions” (β=0.170). “Drug price” also had an impact on medication preferences among patients in rural areas with chronic disease (β=−0.013).
Conclusions
Onset of action is the attribute of medications that is of most concern for patients in rural areas with chronic disease. Subgroup analysis showed that these patients were predominantly female, had a primary school education or lower, were younger than 69 years, were unemployed, and had an annual income between CNY10,000 (USD1,396.78) and CNY50,000 (USD6,983.92). They were willing to pay more for drugs with a quick onset of action, Western medicines, and drugs with reimbursed by medical insurance.
The maser instability associated with the loss-cone distribution has been widely invoked to explain the radio bursts observed in the astrophysical plasma environment, such as aurora and corona. In the laboratory plasma of a tokamak, events reminiscent of these radio bursts have also been frequently observed as an electron cyclotron emission (ECE) burst in the microwave range ($\mathrm{\sim }2{f_{\textrm{ce}}}$ near the last closed flux surface) during transient magnetohydrodynamic events. These bursts have a short duration of ~10 μs and display a radiation spectrum corresponding to a radiation temperature ${T_{e,\textrm{rad}}}$ of over $30\ \textrm{keV}$ while the edge thermal electron temperature ${T_e}$ is only in the range of $1\ \textrm{keV}$. Suprathermal electrons can be generated through magnetic reconnection, and a loss-cone distribution can be generated through open stochastic field lines in the magnetic mirror of the near-edge region of a tokamak plasma. Radiation modelling shows that a sharp distribution gradient $\partial f/\partial {v_ \bot } > 0$ at the loss-cone boundary can cause a negative absorption of ECE radiation through the maser instability. The negative absorption then amplifies the radiation so that the microwave intensity is significantly stronger than the thermal value. The significant ${T_{e,\textrm{rad}}}$ from the simulations suggests the potential role of the loss-cone maser instability in generating the ECE burst in a tokamak.
Isolated multi-MeV $\gamma$-rays with attosecond duration, high collimation and beam angular momentum (BAM) may find many interesting applications in nuclear physics, astrophysics, etc. Here, we propose a scheme to generate such $\gamma$-rays via nonlinear Thomson scattering of a rotating relativistic electron sheet driven by a few-cycle twisted laser pulse interacting with a micro-droplet target. Our model clarifies the laser intensity threshold and carrier-envelope phase effect on the generation of the isolated electron sheet. Three-dimensional numerical simulations demonstrate the $\gamma$-ray emission with 320 attoseconds duration and peak brilliance of $9.3\times 10^{24}$ photons s${}^{-1}$ mrad${}^{-2}$ mm${}^{-2}$ per 0.1$\%$ bandwidth at 4.3 MeV. The $\gamma$-ray beam carries a large BAM of $2.8 \times 10^{16}\mathrm{\hslash}$, which arises from the efficient BAM transfer from the rotating electron sheet, subsequently leading to a unique angular distribution. This work should promote the experimental investigation of nonlinear Thomson scattering of rotating electron sheets in large laser facilities.
Compacted bentonite, used as an engineering barrier for permanent containment of high-level radioactive waste, is susceptible to mineral evolution resulting in compromise of the expected barrier performance due to alkaline–thermal chemical interaction in the near-field. To elucidate the mineral-evolution mechanisms within bentonite and the transformation of the nuclide adsorption properties during that period, experimental evolution of bentonite was conducted in a NaOH solution with a pH of 14 at temperatures ranging from 60 to 120°C. The results showed that temperature significantly affects the stability of minerals in bentonite under alkali conditions. The dissolution rate of fine-grained cristobalite in bentonite exceeds that of smectite, with the phase-transition products of smectite being temperature-dependent. As the temperature rises, smectite experiences a three-stage transformation: initially, at 60°C, the lattice structure thins due to the collapse of the octahedral sheets; at 80°C, the lattice disintegrates and reorganizes into a loose framework akin to albite; and by 100°C, it further reorganizes into a denser framework resembling analcime. The adsorption properties of bentonite exhibit a peak inflection point at 80°C, where the dissolution of the smectite lattice eliminates interlayer pores and exposes numerous polar or negatively charged sites which results in a decrease in specific surface area and an increase in cation exchange capacity and adsorption capacity of Eu3+. This research provides insights into the intricate evolution of bentonite minerals and the associated changes in radionuclide adsorption capacity, contributing to a better understanding of the stability of bentonite barriers and the effective long-term containment of nuclear waste.
Artificial sweeteners are generally used and recommended to alternate added sugar for health promotion. However, the health effects of artificial sweeteners remain unclear. In this study, we included 6371 participants from the National Health and Nutrition Examination Survey with artificial sweetener intake records. Logistic regression and Cox regression were applied to explore the associations between artificial sweeteners and risks of cardiometabolic disorders and mortality. Mendelian randomisation was performed to verify the causal associations. We observed that participants with higher consumption of artificial sweeteners were more likely to be female and older and have above medium socio-economic status. After multivariable adjustment, frequent consumers presented the OR (95 % CI) for hypertension (1·52 (1·29, 1·80)), hypercholesterolaemia (1·28 (1·10, 1·50)), diabetes (3·74 (3·06, 4·57)), obesity (1·52 (1·29, 1·80)), congestive heart failure (1·89 (1·35, 2·62)) and heart attack (1·51 (1·10, 2·04)). Mendelian randomisation confirmed the increased risks of hypertension and type 2 diabetes. Moreover, an increased risk of diabetic mortality was identified in participants who had artificial sweeteners ≥ 1 daily (HR = 2·62 (1·46, 4·69), P = 0·001). Higher consumption of artificial sweeteners is associated with increased risks of cardiometabolic disorders and diabetic mortality. These results suggest that using artificial sweeteners as sugar substitutes may not be beneficial.
This study aimed to investigate the diverse clinical manifestations and simple early biomarkers predicting mortality of COVID-19 patients admitted to the emergency department (ED). A total of 710 patients with COVID-19 were enrolled from 6,896 patients presenting to the ED between January 2022 and March 2022. During the study period, a total of 478 patients tested positive for COVID-19, among whom 222 (46.4%) presented with extrapulmonary manifestations of COVID-19; 49 (10.3%) patients displayed gastrointestinal manifestations, followed by neurological (n = 41; 8.6%) and cardiac manifestations (n = 31; 6.5%). In total, 54 (11.3%) patients died. A Cox proportional hazards model revealed that old age, acute kidney injury at presentation, increased total leukocyte counts, low platelet counts, decreased albumin levels, and increased LDH levels were the independent predictors of mortality. The albumin levels exhibited the highest area under the curve in receiver operating characteristic analysis, with a value of 0.860 (95% confidence interval, 0.796–0.875). The study showed the diverse clinical presentations and simple-to-measure prognostic markers in COVID-19 patients presenting to the ED. Serum albumin levels can serve as a novel and simple early biomarker to identify COVID-19 patients at high risk of death.
Increasing social concern surrounds the potential adverse health effects of precarious employment (PE). In this study, we explored the association between PE and the onset of depressive symptoms.
Methods
A total of 11,555 Korean waged workers (5700 females) contributed 62,217 observations from 2009 to 2022. PE was operationalized as a multidimensional construct, including employment insecurity, income inadequacy and lack of rights and protection. Depressive symptoms were evaluated using the Center for Epidemiological Studies-Depression Scale (11-item version). The association between PE and the onset of depressive symptoms in the subsequent year was estimated using generalized estimating equations. Effect sizes were reported as odds ratio (OR) and 95% confidence interval (CI).
Results
The overall incidence of depressive symptoms was 8.3% during the study period. In cross-sectional analysis, daily employment, disguised employment, lower monthly wages and lack of social insurance coverage were associated with concurrent depressive symptoms in both men and women. Longitudinally, fixed-term employment (OR: 1.17, 95% CI: 1.07–1.29), daily employment (OR: 1.64, 95% CI: 1.45–1.85) and disguised employment (OR: 1.36, 95% CI: 1.17–1.57) were associated with the onset of depressive symptoms among the overall sample. Among men, the lowest quartiles of wage were associated with the onset of depressive symptoms (OR: 1.34, 95% CI: 1.13–1.60), while the absence of a trade union was associated among women (OR: 1.18, 95% CI: 1.01–1.39).
Conclusions
Employment insecurity, inadequate income and lack of rights and protection may contribute to depressive symptoms. Therefore, PE serves as a significant social determinant of mental health among workers in Korea. Active policy efforts are warranted to improve the overall quality of employment in the workforce.
OBJECTIVES/GOALS: Donor hearts are transported in cold storage (CS) and undergo ischemia-reperfusion injury (IRI) when transplanted. IRI injures microvascular endothelial cells (EC), heightens the immune response, and has been associated with increased autophagy. We aim to understand the changes in autophagy during CS and IRI and its impact on EC immunogenicity. METHODS/STUDY POPULATION: To study autophagy changes during IRI, immunoblotting for autophagy markers was performed in mouse cardiac ECs (MCECs) lysates. MCECs were in a cold preservation solution in a hypoxic chamber for 6 hours(h) and warm conditions with culture medium for 24 h. MCECs, under standard conditions, served as controls. Secreted interferon-gamma (IFN-γ) levels were quantified via ELISA to study autophagy and EC immunogenicity. MCEC-sensitized CD8+ T-cells were isolated from C57BL/6 spleens and co-cultured with MCECs pre-treated for 16 h with rapamycin or starvation, autophagy inducers, or chloroquine, an autophagy inhibitor under normal or IRI conditions. MCECs without any treatment served as controls. RESULTS/ANTICIPATED RESULTS: To determine autophagy levels in IRI, immunoblotting of MCEC lysates revealed a significant increase (P<0.01) in the established autophagy marker, LC3, at early time points post-reperfusion compared to NT conditions, indicating more autophagosome formation during CS and IRI. To assess the role of autophagy in EC immunogenicity, the co-culture experiment revealed that autophagy induction in MCECs under NT and HCS conditions with rapamycin had a 74.9-fold and 51.5-fold reduction of IFN-γ (pg/mL), resepectively, compared to the non-treated controls. In contrast, autophagy inhibition in MCECs with chloroquine resulted in 1.82-fold increase of IFN-γ compared to untreated controls. This suggests a protective role of autophagy in ECs during IRI. DISCUSSION/SIGNIFICANCE: We observed that autophagy may be protective during IRI by mitigating EC immunogenicity. Thus, pharmacologically modulating microvascular EC autophagy in donor hearts prior to transplantation may mitigate insults incurred during CS and IRI.
Growing evidence points to the pivotal role of vitamin D in the pathophysiology and treatment of major depressive disorder (MDD). However, there is a paucity of longitudinal research investigating the effects of vitamin D supplementation on the brain of MDD patients.
Methods
We conducted a double-blind randomized controlled trial in 46 MDD patients, who were randomly allocated into either VD (antidepressant medication + vitamin D supplementation) or NVD (antidepressant medication + placebos) groups. Data from diffusion tensor imaging, resting-state functional MRI, serum vitamin D concentration, and clinical symptoms were obtained at baseline and after an average of 7 months of intervention.
Results
Both VD and NVD groups showed significant improvement in depression and anxiety symptoms but with no significant differences between the two groups. However, a greater increase in serum vitamin D concentration was found to be associated with greater improvement in depression and anxiety symptoms in VD group. More importantly, neuroimaging data demonstrated disrupted white matter integrity of right inferior fronto-occipital fasciculus along with decreased functional connectivity between right frontoparietal and medial visual networks after intervention in NVD group, but no changes in VD group.
Conclusions
These findings suggest that vitamin D supplementation as adjunctive therapy to antidepressants may not only contribute to improvement in clinical symptoms but also help preserve brain structural and functional connectivity in MDD patients.
Although some studies have examined the association between eating behaviour and elevated blood pressure (EBP) in adolescents, current data on the association between sugar-sweetened beverages (SSB) and EBP in adolescents in Yunnan Province, China, are lacking.
Setting:
Cluster sampling was used to survey freshmen at a college in Kunming, Yunnan Province, from November to December. Data on SSB consumption were collected using an FFQ measuring height, weight and blood pressure. A logistic regression model was used to analyse the association between SSB consumption and EBP, encompassing prehypertension and hypertension with sex-specific analyses.
Participants:
The analysis included 4781 college students.
Results:
Elevated systolic blood pressure (SBP) and diastolic blood pressure (DBP) were detected in 35·10 % (1678/4781) and 39·34 % (1881/4781) of patients, respectively. After adjusting for confounding variables, tea beverage consumption was associated with elevated SBP (OR = 1·24, 95 % CI: 1·03, 1·49, P = 0·024), and carbonated beverage (OR = 1·23, 95 % CI: 1·04, 1·45, P = 0·019) and milk beverage (OR = 0·81, 95 % CI: 0·69, 0·95, P = 0·010) consumption was associated with elevated DBP in college students. Moreover, fruit beverage (OR = 1·32, 95 % CI: 1·00, 1·75, P = 0·048) and milk beverage consumption (OR = 0·69, 95 % CI: 0·52, 0·93, P = 0·014) was associated with elevated DBP in males.
Conclusion:
Our findings indicated that fruit and milk beverage consumption was associated with elevated DBP in males, and no association was observed with EBP in females.
Based on 30 high-resolution U-Th dating controls, we reconstruct stalagmite δ18O records from 45 to 15 thousand years ago (ka B.P., before AD 1950) from the Shizhu Cave, which is located in southwestern China under the influence of both the Indian Summer Monsoon (ISM) and the East Asian Summer Monsoon (EASM). By integrating with the other stalagmite δ18O records in Asia during the middle to late last glacial, our results reveal two main moisture trajectories: one from the Indian Ocean, through the Shizhu Cave towards central China, and the other from the Pacific Ocean to central and northern China. The systematic decrease of the average values of stalagmite δ18O records from oceans to inland China reveals a spatial pattern of water vapour fractionation and moisture trajectory during the middle to late last glacial. In contrast, the variation amplitude, which is defined as the departures apart from the background δ18O records during Heinrich stadials 1 to 4 (HS1–HS4), show an increasing trend from the coastal oceans to mid-latitude inland China, presenting a ‘coastal-inland’ pattern, which can be interpreted by the enhanced East Asian Winter Monsoon (EAWM) and the weakened EASM. More specifically, the enriched stalagmite δ18O records in the EASM region during HS1 to HS4 are caused by the decreased summer rainfall amount or/and the increased proportion of summer moisture resources from the Pacific Ocean. These new observations deepen our understanding of the complicated stalagmite δ18O records in the EASM region.
Adsorption desulfurization is a potential new method for deep desulfurization of fuel oil. The development of adsorbents with high adsorption capacity and selectivity is the core of deep adsorption desulfurization. The adsorption behavior of thiophene in MCM-41 mesoporous materials modified by various metal ions was studied in order to understand the adsorption desulfurization process of molecular sieves. The Fe-, Co-, and Zn-modified MCM-41 materials were prepared using a one-step in situ hydrothermal synthesis method. The modified MCM-41 molecular sieves maintained the mesoporous structure, and the metal ions had specific dispersion on the surface of the molecular sieves. Adsorption of thiophene on the surfaces of molecular sieves had both physical and chemical characteristics. The adsorption desulfurization performance of the modified molecular sieve was superior to that of the pure silica molecular sieve. In the simulated gasoline with sulfur content of 220 μg/g, when the amount of adsorbent used was 100 mg, the adsorptive desulfurization performance tended to be in equilibrium, and the optimum adsorption temperature was 30°C. Fe-MCM-41 and MCM-41 molecular sieves reached adsorption equilibrium after ~60 min, but the desulfurization rate of Co-MCM-41 and Zn-MCM-41 still increased slightly. The kinetic simulation results indicated that the pseudo-second-order kinetics adsorption model described well the adsorption process of thiophene on molecular sieves. The molecular sieve Fe-MCM-41 had the best desulfurization performance with an equilibrium adsorption capacity of 14.02 mg/g and the desulfurization rate was ~90%.
LongYan kaolin has a large Fe content which affects the coloring. Bioleaching treatments to remove Fe impurities were conducted here using indigenous dissimilatory Fe(III)-reducing bacteria. The factors that affect bioleaching efficiency include bioleaching time, carbon source, pH, temperature, pulp density, and inoculum density and these were examined. Environmental scanning electron microscopy and X-ray diffraction were used to examine any textural or mineralogical changes at the surface of the kaolin that may have occurred during the bioleaching. Iron impurities in the kaolin were reduced from 0.88% to 0.48% with an increase in the natural whiteness index from 60.8% to 81.5% after 7 days of bioleaching treatment. A granulometric analysis of dispersed kaolin demonstrated that the bioleaching resulted in a decrease in particle size. The results demonstrated that the bioleaching was very effective at improving the quality of the kaolin, where insoluble Fe(III), either adsorbed to the kaolin surfaces or admixed as amorphous forms, was leached out by micro-organisms as water-soluble Fe(II).
Hydrophobicity, swellability, and dispersion are important properties for organo-montmorillonites (OMnt) and have yet to be fully characterized for all OMnt configurations. The purpose of the present work was to examine the preparation of OMnt from the reaction of Ca2+-montmorillonite (Ca2+-Mnt) with a high concentration of surfactant and to reveal the relevant properties of hydrophobicity and dispersion of the resultant OMnt. A series of OMnt samples were prepared using a small amount of water and cetyltrimethylammonium bromide (CTAB) with a concentration more than the CTAB critical micelle concentration (CMC). The relationship between OMnt microstructure and the hydrophobicity and swellability properties was investigated in detail. The resulting OMnt samples were characterized using powder X-ray diffraction patterns (XRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric and differential thermogravimetry (TG-DTG), water contact angle tests, swelling indices, and transmission electron microscopy (TEM). The addition of CTAB and water in the OMnt preparation affected the OMnt microstructure and properties. An increase in CTAB concentration led to a more ordered arrangement of cetyltrimethylammonium (CTA+) cations in the interlayer space of the OMnt and a large amount of CTA+ cations on the outer surfaces of the OMnt. The swelling indices and the water contact angles of OMnt samples depended on the distribution of the CTAB surfactant on OMnt and the orientation of the surfactant hydrophilic groups on the inner and on the outer surfaces of OMnt. A maximum swelling index of 39 mL/g in xylene was achieved with an average water contact angle of 62.0° ± 2.0° when the amount of CTAB added was 2 times the cation exchange capacity (CEC) of Mnt and the lowest water to dry Mnt mass ratio was 3 during the preparation of OMnt samples. The platelets of OMnt aggregated together in xylene by electrostatic attraction and by hydrophobic interactions.
Organo-montmorillonite (OMnt) has wide applications in paints, clay-polymer nanocomposites, biomaterials, etc. In most cases, the dispersibility and swellability of OMnt dictate the performance of OMnt in the target products. Previous studies have revealed that the properties can be improved when multiple organic species are co-introduced into the interlayer space of montmorillonite (Mnt). In the present study, single surfactant erucylamide (EA), dual-surfactants cetyltrimethyl ammonium bromide (CTAB) and octadecyltrimethyl ammonium chloride (OTAC), and ternary-surfactants EA, CTAB, and OTAC were co-introduced into Mnt by solution intercalation. The resulting OMnts were characterized by powder X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetry-differential thermogravimetry (TG-DTG), water contact-angle tests, scanning electronic microscopy (SEM), laser particle-size analysis, and swelling indices. Mnt co-modified by ternary CTAB, OTAC, and EA led to a large d001 value (4.20 nm), surface hydrophobicity with a contact angle of 95.6°, swellability (50 mL/g) with small average particle sizes (2.1−2.8 μm) in xylene, and >99% of the OMnt particles were kept as <5 μm in deionized water. The formation of EA-modified-Mnt was proposed according to hydrophobic affinity, hydrogen bonding, and van der Waals forces. The nanoplatelets of the CTA+, OTA+, and EA co-modified OMnts in xylene were assembled into a house-of-cards structure by face-to-edge and edge-to-edge associations. The electrostatic attractions, electrostatic and steric repulsions, and hydrophobic interactions were responsible for the good dispersibility of OMnt in xylene. The ternary surfactant co-modified OMnt with high dispersion and swellability will make OMnt better suited for real-world applications.
Supercritical carbon dioxide (scCO2) processing has been proven as a method for preparing polymer/montmorillonite (MMT) nanocomposites with improved platelet dispersion. The influence of scCO2 processing on the shape and size of the MMT tactoid/platelet, which is of great importance to the final platelet dispersion in the polymer matrix, is scarcely reported in the literature. In the present study, the pristine MMT was first surface modified with 3-glycidoxypropyltrimethoxysilane (the grafted MMT is labeled as GMMT), and then intercalated using three kinds of intercalating agents, myristyltrimethyl-ammonium bromide (MTAB), tetradecyltrihexylphosphonium chloride (TDTHP), and ethoxyltriphenyl-phosphonium chloride (ETPC), in water or scCO2, to study the effect of intercalating agent type and intercalation method on the morphology and thermal properties of GMMT, as a part of a program devoted to the synthesis of polymer/MMT nanocomposites. The structure of intercalated GMMT was characterized by thermogravimetric analysis, X-ray powder diffraction, and scanning electron microscopy (SEM). The optimum intercalation conditions in scCO2 were established by trying a range of reaction times and pressures. The structures of intercalated GMMT obtained under optimum scCO2 conditions and water were compared. The basal spacing of GMMT intercalated in scCO2 was almost the same as that in water, and both were obviously larger than that of GMMT. The GMMT exhibited a compact spherical morphology (examined using SEM), and the surface structures (including surface morphology, surface roughness, and surface compactness) of samples intercalated in water became ‘less compact’ and the degree of the ‘compactness’ of samples intercalated in scCO2 decreased further. Whether in water or scCO2, samples intercalated with TDTHP exhibited a larger basal spacing and the extent of disorder increased compared to that for samples intercalated with MTAB. The pristine MMT was also intercalated for comparison and silane grafting was proven to contribute to the increased basal spacing and ‘less compact’ surface structure.