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1.
Zhongguo Fei Ai Za Zhi ; 27(2): 118-125, 2024 Feb 20.
Artigo em Chinês | MEDLINE | ID: mdl-38453443

RESUMO

BACKGROUND: The pathological types of lung ground glass nodules (GGNs) show great significance to the clinical treatment. This study was aimed to predict pathological types of GGNs based on computed tomography (CT) quantitative parameters. METHODS: 389 GGNs confirmed by postoperative pathology were selected, including 138 cases of precursor glandular lesions [atypical adenomatous hyperplasia (AAH) and adenocarcinoma in situ (AIS)], 109 cases of microinvasive adenocarcinoma (MIA) and 142 cases of invasive adenocarcinoma (IAC). The morphological characteristics of nodules were evaluated subjectively by radiologist, as well as artificial intelligence (AI). RESULTS: In the subjective CT signs, the maximum diameter of nodule and the frequency of spiculation, lobulation and pleural traction increased from AAH+AIS, MIA to IAC. In the AI quantitative parameters, parameters related to size and CT value, proportion of solid component, energy and entropy increased from AAH+AIS, MIA to IAC. There was no significant difference between AI quantitative parameters and the subjective CT signs for distinguishing the pathological types of GGNs. CONCLUSIONS: AI quantitative parameters were valuable in distinguishing the pathological types of GGNs.


Assuntos
Adenocarcinoma in Situ , Adenocarcinoma , Neoplasias Pulmonares , Lesões Pré-Cancerosas , Humanos , Neoplasias Pulmonares/patologia , Inteligência Artificial , Estudos Retrospectivos , Invasividade Neoplásica , Adenocarcinoma/patologia , Adenocarcinoma in Situ/patologia , Tomografia Computadorizada por Raios X/métodos , Lesões Pré-Cancerosas/patologia , Hiperplasia , Pulmão/diagnóstico por imagem , Pulmão/patologia
2.
Heliyon ; 9(4): e14892, 2023 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-37025842

RESUMO

To improve the availability of inorganic phosphorus (P) in soil, we investigated the role of three macromolecular organic acids (MOAs), including fulvic acid (FA), polyaspartic acid (PA), and tannic acid (TA), in reducing the fixation of inorganic P fertilizer in the soil. AlPO4, FePO4, and Ca8H2(PO4)6·5H2O crystals were chosen as insoluble phosphate representatives in the soil to simulate the solubilization process of inorganic P by MOAs. The microstructural and physicochemical properties of AlPO4, FePO4, and Ca8H2(PO4)6·5H2O were determined by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) before and after treatment of MOAs. In addition, the amounts of leached P and fixed inorganic P in Inceptisols and Alfisols affected by MOAs combined with superphosphate (SP) fertilizer were determined by soil leaching experiments. The presence of the three MOAs significantly increased the concentration of leached P and reduced the contents of insoluble inorganic phosphate formed with iron, aluminum, and calcium fixed in the soil, in which PA combined with SP had the most significant effect. Furthermore, the less inorganic P fixation in the combination treatment of MOAs and SP resulted in a greater wheat yield and P uptake. Therefore, MOAs could be a synergistic material for increasing P fertilizer utilization.

3.
Front Med (Lausanne) ; 10: 1174429, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38264049

RESUMO

The development of intensive care medicine is inseparable from the diversified monitoring data. Intensive care medicine has been closely integrated with data since its birth. Critical care research requires an integrative approach that embraces the complexity of critical illness and the computational technology and algorithms that can make it possible. Considering the need of standardization of application of big data in intensive care, Intensive Care Medicine Branch of China Health Information and Health Care Big Data Society, Standard Committee has convened expert group, secretary group and the external audit expert group to formulate Chinese Experts' Consensus on the Application of Intensive Care Big Data (2022). This consensus makes 29 recommendations on the following five parts: Concept of intensive care big data, Important scientific issues, Standards and principles of database, Methodology in solving big data problems, Clinical application and safety consideration of intensive care big data. The consensus group believes this consensus is the starting step of application big data in the field of intensive care. More explorations and big data based retrospective research should be carried out in order to enhance safety and reliability of big data based models of critical care field.

4.
Sci Rep ; 10(1): 20317, 2020 11 23.
Artigo em Inglês | MEDLINE | ID: mdl-33230220

RESUMO

Soil physical properties and soil organic carbon (SOC) are considered as important factors of soil quality. Arable land, grassland, and forest land coexist in the saline-alkali reclamation area of the Yellow River Delta (YRD), China. Such different land uses strongly influence the services of ecosystem to induce soil degradation and carbon loss. The objective of this study is to evaluate the variation of soil texture, aggregates stability, and soil carbon affected by land uses. For each land use unit, we collected soil samples from five replicated plots from "S" shape soil profiles to the depth of 50 cm (0-5, 5-10, 10-20, 20-30, and 30-50 cm). The results showed that the grassland had the lowest overall sand content of 39.98-59.34% in the top 50 cm soil profile. The content of soil aggregates > 0.25 mm (R0.25), mean weight diameter and geometric mean diameter were significantly higher in grassland than those of the arable and forest land. R0.25, aggregate stability in arable land in the top 30 cm were higher than that of forest land, but lower in the soil profile below 20 cm, likely due to different root distribution and agricultural practices. The carbon management index (CMI) was considered as the most effective indicator of soil quality. The overall SOC content and CMI in arable land were almost the lowest among three land use types. In combination with SOC, CMI and soil physical properties, we argued that alfalfa grassland had the advantage to promote soil quality compared with arable land and forest land. This result shed light on the variations of soil properties influenced by land uses and the importance to conduct proper land use for the long-term sustainability of the saline-alkali reclamation region.

5.
Chemosphere ; 255: 126976, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32402890

RESUMO

Bentonite was modified by introducing humic acid (HA) into interlayer space of bentonite. The structural and physicochemical properties of modified bentonite were determined by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), X-ray powder diffraction (XRD) and thermogravimetric analysis (TGA). The results showed that HA could enter the bentonite interlayer and increase the interlayer distance. Moreover, we were also investigated the high adsorption capacity and thermodynamics of modified bentonite to NH4+ cations in solutions. Under the same conditions, the NH4+ adsorption efficiency of modified bentonite (96.4%) was 69.2% higher compared with the natural bentonite (57.0%). The pseudo-second order kinetic model well fit the adsorption kinetics of NH4+ on modified bentonite, indicating that the adsorption type was chemical adsorption or chemisorptions. The isotherms fit well with Langmuir model, and the separation factor revealed that NH4+ on modified bentonite belonged to favorable adsorption. Compared with the natural bentonite, the modified bentonite exhibited a much lower leaching loss of NH4+-N and NO3--N in soil. Meanwhile, the loss of nitrogen caused by NH3 volatilization and N2O emission from soil could also be significantly attenuated by the combined application of modified bentonite and urea. The slower nitrogen release in the treatment combining modified bentonite and urea resulted in a greater yield and nitrogen uptake of wheat. Collectively, the modified bentonite could be used as nitrogen fertilizer synergist to enhance the nitrogen use efficiency.


Assuntos
Bentonita/química , Substâncias Húmicas , Nitrogênio/química , Adsorção , Fertilizantes , Concentração de Íons de Hidrogênio , Cinética , Solo/química , Espectroscopia de Infravermelho com Transformada de Fourier , Ureia/química
6.
J Sci Food Agric ; 100(12): 4425-4432, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32388863

RESUMO

BACKGROUND: The utilization rate of urea-N in fertilizer plays a very important role in agricultural production and environmental protection. Humic acid urea (HAU) and polyaspartic acid urea (PAU) are two similar synergistic nitrogen fertilizers. METHODS: Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD) and carbon-13-nuclear magnetic resonance (13 C-NMR) were used to determine the loading of urea-N into humic acid (HA) and polyaspartic acid (PA). Thermal stability and physical adsorption properties of HAU and PAU were assessed by thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) surface measurement. The soil incubation experiment was conducted to investigate the effects of HAU and PAU on nitrogen transformation and gaseous nitrogen loss compared with commercial urea. RESULTS: Nitrogen transformation from HAU and PAU was slowed down compared with urea. After 90 days of incubation, HAU and PAU reduced the cumulative ammonia (NH3 ) volatilization (by 9.70% and 6.30%, respectively) and nitrous oxide (N2 O) emission (by 40.48% and 43.00%, respectively) from soil compared with the urea-alone treatment. CONCLUSION: HAU and PAU could improve the nitrogen use efficiency. © 2020 Society of Chemical Industry.


Assuntos
Fertilizantes/análise , Substâncias Húmicas/análise , Nitrogênio/química , Peptídeos/química , Ureia/química , Adsorção , Amônia/química , Cinética , Solo/química , Volatilização
7.
Science ; 367(6478): 688-694, 2020 02 07.
Artigo em Inglês | MEDLINE | ID: mdl-32029629

RESUMO

Synapses between engram cells are believed to be substrates for memory storage, and the weakening or loss of these synapses leads to the forgetting of related memories. We found engulfment of synaptic components by microglia in the hippocampi of healthy adult mice. Depletion of microglia or inhibition of microglial phagocytosis prevented forgetting and the dissociation of engram cells. By introducing CD55 to inhibit complement pathways, specifically in engram cells, we further demonstrated that microglia regulated forgetting in a complement- and activity-dependent manner. Additionally, microglia were involved in both neurogenesis-related and neurogenesis-unrelated memory degradation. Together, our findings revealed complement-dependent synapse elimination by microglia as a mechanism underlying the forgetting of remote memories.


Assuntos
Proteínas do Sistema Complemento/fisiologia , Hipocampo/fisiologia , Transtornos da Memória/fisiopatologia , Memória de Longo Prazo/fisiologia , Microglia/fisiologia , Retenção Psicológica/fisiologia , Sinapses/fisiologia , Animais , Antígenos CD55 , Proteínas do Sistema Complemento/genética , Transtornos da Memória/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Microglia/imunologia , Fagocitose
8.
Ciênc. rural (Online) ; 49(6): e20180098, 2019. tab, graf
Artigo em Inglês | LILACS | ID: biblio-1045374

RESUMO

ABSTRACT: The influences of byproduct amendments, containing silicon, calcium, magnesium and potassium, on acidic soil quality in Jiaodong Peninsula of China had been studied and compared with that of lime through monitoring physicochemical properties and enzyme activities of acidic soil over a 120-day period. Byproduct amendments (1125, 2250, 4500 and 9000 kg ha-1) and lime 2250 kg ha-1 was applied in the acidic soil. Results showed that both byproduct amendments and lime significantly increased the pH, EC and enzyme activities of soil. The by-product amendments inhibited microbial biomass carbon and soil respiration. Nevertheless, the lime-treated soil had a much more higher level of CO2 emission than the by-product amendments-treated soil. Compared to the by-product amendments-treated soil, the lime-treated soil had the higher pH, peroxidase activity, phenol oxidase activity and invertase activity. Therefore, lime might be a better choice over by-product amendments to improve chemical and biological properties of the acidic soil in Jiaodong Peninsula of China. For soils lacking available calcium and magnesium, the mixture of 4500 kg ha-1 amendments and 2250 kg ha-1 lime was recommend to treat the soil.


RESUMO: As influências do emprego de subprodutos que contêm silício, cálcio, magnésio e potássio, sobre a qualidade do solo ácido na Península de Jiaodong da China, foram estudadas e comparadas com a da cal através do monitoramento das propriedades físico-químicas e atividades enzimáticas do solo ácido ao longo de um 120- período do dia. Os resultados mostraram que as alterações dos subprodutos e a cal aumentaram significativamente as atividades de pH, CE e enzimas do solo. As alterações dos subprodutos obviamente inibiram o carbono da biomassa microbiana e a respiração do solo, mas o solo tratado com cal apresentou um maior nível de emissão de CO2. Em comparação com as modificações do subproduto, o solo tratado tinha o maior pH, a atividade da peroxidase, a atividade da fenol oxidase e a atividade da invertease. Portanto, o cal pode ser uma escolha melhor em relação às alterações dos subprodutos para melhorar as propriedades químicas e biológicas do solo ácido na Península de Jiaodong da China.

9.
J Phys Chem B ; 122(37): 8706-8711, 2018 09 20.
Artigo em Inglês | MEDLINE | ID: mdl-30138562

RESUMO

Vesicles in surfactant systems are influenced by a shear field. The high shear flow generated by a homogenizer is expected to affect the size of vesicles. Hence, it should be possible to control the size and dispersion of vesicles by tuning the shear. In this study, the influence of shear on the vesicle phase was studied by measuring the rheology and conductivity of a solution made of the nonionic surfactant trideceth-5, a polyethylene glycol ether of tridecyl alcohol with an average number of ethylene oxide of 5, and the anionic surfactant sodium dodecylsulfate. It was found that when shear was applied by a homogenizer, the bilayers of the multilamellar vesicles were stripped off and became unilamellar vesicles, which decreased the viscoelasticity of the system. However, because of the pressure provided by the homogenizer, the newly formed unilamellar vesicles were small and the relative distance between them was large. As a result, the vesicles were no longer crowded and could easily pass each other under shear. This is why the unilamellar vesicles generated by the homogenizer had low viscoelasticity and flow birefringence. Additionally, it took a long time for the unilamellar vesicles to relax back to the original state.


Assuntos
Lipossomas Unilamelares/síntese química , Substâncias Viscoelásticas/química , Birrefringência , Álcoois Graxos/química , Tamanho da Partícula , Polietilenoglicóis/química , Pressão , Reologia , Dodecilsulfato de Sódio/química , Tensoativos/química , Viscosidade
10.
J Thorac Cardiovasc Surg ; 155(6): 2267-2274, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29534905

RESUMO

OBJECTIVE: To study the risk factors of oxygenation impairment in patients with type-A acute aortic dissection who underwent total arch replacement with a stented elephant trunk. METHODS: In this study, 169 consecutive patients were enrolled who were diagnosed with type-A acute aortic dissection and underwent a total arch replacement procedure at the Qilu Hospital of Shandong University between January 2015 and February 2017. Postoperative oxygenation impairment was defined as arterial oxygen partial pressure/inspired oxygen fraction ≤ 200 with positive end expiratory pressure ≥ 5 cm H2O that occurred within 72 hours of surgery. Perioperative clinical characteristics of all patients were collected and univariable analyses were performed. Risk factors associated with oxygenation impairment identified by univariable analyses were included in the multivariable regression analysis. RESULTS: The incidence of postoperative oxygenation impairment was 48.5%. Postoperative oxygenation impairment was associated with prolonged mechanical ventilation time, intensive care unit stay, and hospital stay. Multivariable regression analysis demonstrated that body mass index (odds ratio [OR], 1.204; 95% confidence interval [CI], 1.065-1.361; P = .003), preoperative oxygenation impairment (OR, 9.768; 95% CI, 4.159-22.941; P < .001), preoperative homocysteine (OR, 1.080; 95% CI, 1.006-1.158; P = .032), circulatory arrest time (OR, 1.123; 95% CI, 1.044-1.207; P = .002), and plasma transfusion (OR, 1.002; 95% CI, 1.001-1.003; P = .002) were significantly associated with postoperative oxygenation impairment. CONCLUSIONS: Postoperative oxygenation impairment is a common complication of surgery for type-A acute aortic dissection. Body mass index, preoperative oxygenation impairment, preoperative homocysteine, circulatory arrest time, and plasma transfusion were independent risk factors for oxygenation impairment after a total arch replacement procedure.


Assuntos
Aneurisma da Aorta Torácica/cirurgia , Dissecção Aórtica/cirurgia , Implante de Prótese Vascular/efeitos adversos , Oxigênio/sangue , Complicações Pós-Operatórias/epidemiologia , Adulto , Aorta Torácica/cirurgia , Prótese Vascular , Implante de Prótese Vascular/instrumentação , Implante de Prótese Vascular/mortalidade , Implante de Prótese Vascular/estatística & dados numéricos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Pressão Parcial , Estudos Retrospectivos , Fatores de Risco
11.
Cell Discov ; 3: 17044, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29238610

RESUMO

Reactive astrogliosis is a hallmark of many neurological disorders, yet its functions and molecular mechanisms remain elusive. Particularly, the upstream signaling that regulates pathological responses of astrocytes is largely undetermined. We used a mouse traumatic brain injury model to induce astrogliosis and revealed activation of ErbB receptors in reactive astrocytes. Moreover, cell-autonomous inhibition of ErbB receptor activity in reactive astrocytes by a genetic approach suppressed hypertrophic remodeling possibly through the regulation of actin dynamics. However, inhibiting ErbB signaling in reactive astrocytes did not affect astrocyte proliferation after brain injury, although it aggravated local inflammation. In contrast, active ErbB signaling in mature astrocytes of various brain regions in mice was sufficient to initiate reactive responses, reproducing characterized molecular and cellular features of astrogliosis observed in injured or diseased brains. Further, prevalent astrogliosis in the brain induced by astrocytic ErbB activation caused anorexia in animals. Therefore, our findings defined an unrecognized role of ErbB signaling in inducing reactive astrogliosis. Mechanistically, inhibiting ErbB signaling in reactive astrocytes prominently reduced Src and focal adhesion kinase (FAK) activity that is important for actin remodeling, although ErbB signaling activated multiple downstream signaling proteins. The discrepancies between the results from loss- and gain-of-function studies indicated that ErbB signaling regulated hypertrophy and proliferation of reactive astrocytes by different downstream signaling pathways. Our work demonstrated an essential mechanism in the pathological regulation of astrocytes and provided novel insights into potential therapeutic targets for astrogliosis-implicated diseases.

12.
Oncotarget ; 8(20): 33343-33352, 2017 May 16.
Artigo em Inglês | MEDLINE | ID: mdl-28415624

RESUMO

To date, hypoxia-inducible factor 1a (HIF-1a) and astrocyte elevated gene-1 (AEG-1) have been involved in the proliferation, migration and morphological changes of vascular smooth muscle cells. However, the potential relationship of HIF-1a-AEG-1 pathway in human aortic smooth muscle cell (HASMC) has not been reported. In the present study, in-vitro assays were utilized to explore the potential impact of HIF-1a-AEG-1 signaling on HASMC phenotype. Here, we found that HIF-1a expression was up-regulated in the media of thoracic aortic dissection tissues as compared with normal aortic tissues, and was associated with increased apoptotic SMCs and decreased AEG-1 expression. Mechanically, hypoxia promoted the expression of HIF-1a by PI3K-AKT pathway in HASMCs; HIF-1a further suppressed the expressions of AEG-1, a-SMA and SM22a, and promoted osteopontin (OPN) expression. Functionally, HIF-1a inhibited the proliferation and migration of HASMCs. However, si-HIF-1a or Akt inhibitor abrogated HIF-1a-mediated related expressions and biological effects above. In conclusion, HIF-1a induces HASMC phenotype switch, and closely related to PI3K/AKT and AEG-1 signaling, which may provide new avenues for the prevention and treatment of aortic dissection diseases.


Assuntos
Moléculas de Adesão Celular/metabolismo , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Músculo Liso Vascular/citologia , Miócitos de Músculo Liso/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Dissecção Aórtica/genética , Dissecção Aórtica/metabolismo , Dissecção Aórtica/patologia , Aorta , Apoptose/genética , Biomarcadores , Moléculas de Adesão Celular/genética , Movimento Celular , Proliferação de Células , Células Cultivadas , Expressão Gênica , Humanos , Hipóxia/genética , Hipóxia/metabolismo , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , Proteínas de Membrana , Fenótipo , Fosforilação , Proteínas de Ligação a RNA
13.
Tumour Biol ; 36(12): 9769-77, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26156800

RESUMO

Recently, astrocyte-elevated gene-1 (AEG-1) and insulin-like growth factor 1 (IGF-1) have been involved in the regulation of multiple signaling pathways in tumorigenesis. To date, the detailed mechanisms underlying IGF-1-AEG-1 pathway-induced proliferation and apoptosis in cardiac myxoma (CM) was not reported. In the present study, we used immnohistochemistry, immunoblotting, and qRT-PCR to detect the expression profile of IGF-1 and AEG-1 in 90 CM tissues, and then cultured CM cells were subjected to si-AEG-1, in vitro, and in vivo assays. Our findings showed that IGF-1 and AEG-1 were obviously upregulated in CM tissues and markedly associated with tumor size. When CM cells were treated with si-AEG-1, si-AEG-1 attenuated IGF-1-induced CM cell growth and enhanced cell apoptosis. Mechanically, we validated the expression of AEG-1, p-Erk1/2, and p-Akt increased in CM cells in response to IGF-1 treatment in a time-dependent manner. However, si-AEG-1 affected the expression of these proteins. Functionally, we found the knockdown of AEG-1-inhibited G1/S transition and tumor formation of CM cells. In conclusion, AEG-1 regulates IGF-1-induced proliferation and apoptosis via Erk1/2 and Akt signaling in CM development, which suggests IGF-1-AEG-1 signaling could be recommended to be a useful target to exert anti-tumor effects on CM.


Assuntos
Moléculas de Adesão Celular/genética , Neoplasias Cardíacas/genética , Fator de Crescimento Insulin-Like I/genética , Mixoma/genética , Adulto , Idoso , Animais , Apoptose , Moléculas de Adesão Celular/biossíntese , Linhagem Celular Tumoral , Proliferação de Células/genética , Progressão da Doença , Feminino , Regulação Neoplásica da Expressão Gênica , Neoplasias Cardíacas/patologia , Humanos , Fator de Crescimento Insulin-Like I/biossíntese , Masculino , Proteínas de Membrana , Camundongos , Pessoa de Meia-Idade , Proteína Quinase 3 Ativada por Mitógeno/genética , Mixoma/patologia , Proteínas Proto-Oncogênicas c-akt/genética , Proteínas de Ligação a RNA , Ensaios Antitumorais Modelo de Xenoenxerto
14.
Langmuir ; 30(10): 2632-8, 2014 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-24559199

RESUMO

The segregation and phase sequence of semifluorinated cat-anionic surfactant membranes at different excess surface charges was investigated by freeze-fracture transmission electron microscope (FF-TEM), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR). The thermal behavior of the membranes was evaluated by conductivity, rheology, and deuterium nuclear magnetic resonance ((2)H NMR). The experimental results show that the cat-anionic fluorinated surfactant mixtures can form faceted vesicles and punctured lamellar phase when there is excess surface charge. The cationic and anionic fluorinated surfactants are stiff in the membranes, like phospholipids in the frozen "crystalline" or "gel" phase. For the system with excess cationic surface charge, the gel-like faceted vesicles and punctured lamellae can transform into smooth-shaped vesicles at 65 °C. However, for the system with no excess charge or with excess anionic surface charge, no phase transformation occurs even at 90 °C. A model was established to demonstrate the mechanism of the formation and transition of the aggregates with different morphologies. The segregation-crystallization mechanism works well with other cosmotropic counterions from the Hofmeister series. The observations provide a better understanding of how to control the membrane morphology of the aqueous solutions of cat-anionic surfactant mixtures.

15.
Langmuir ; 27(5): 1675-82, 2011 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-21192689

RESUMO

In the cationic and anionic (catanionic) surfactant mixed system, tetradecyltrimethylammonium hydroxide (TTAOH)/decanoic acid (DA)/H(2)O, abundant phase behaviors were obtained in the presence of hydrophilic and hydrophobic salts. The microstructures of typical L(α) phases with the different compositions were characterized by the transmission electron microscope (TEM) images. Aqueous double-phase transition induced by addition of hydrophilic salts was observed when the cationic surfactant was in excess. Salt-induced reversible vesicle phases could be obtained when the anionic surfactant was excess, whereas the vesicle phase at lower salinity behaves highly viscoelastic but is much less viscoelastic with high salinity which was demonstrated by measuring their rheological properties. The L(α) phase with the positive membrane charges can be finally transferred into an L(1) phase with added salts. The ion specificity of hydrophilic and hydrophobic salts is discussed, and the order of cations is summarized, which is significant for the further study of the Hofmeister effects on catanionic surfactant mixed systems.

16.
Langmuir ; 25(18): 10540-7, 2009 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-19735130

RESUMO

The swelling of lamellar phase can be induced by the replacement of solvent in a tetradecyltrimethylammonium bromide (TTABr) and sodium laurate (SL) aqueous mixed solution that contains cream floating precipitates on the upper phase and L1-phase (micelles) at the lower phase. The cream floating precipitates contain densely packed multilamellar vesicles, which were determined by freeze-fracture transmission electron microscopy (FF-TEM) images. Phase transition, from cream floating precipitates to swelling birefringent vesicle phase, to two-phase Lalpha/L1, and finally to micelle phase, can be induced by adding glycerin as solvent in the aqueous solution. At first, densely packed multilamellar vesicles of cream floating precipitates on the upper phase swelled throughout the whole phase with increasing content of glycerin. The replacement of solvent lowers the turbidity of the dispersion and swells the interlamellar distance between the bilayers, which is explained by matching of refractive index of the solvent to the refractive index of the bilayers of the surfactant mixtures. With an increasing amount of glycerin, the swelling Lalpha phase turned to two-phase Lalpha/L1, and finally to L1 phase (micelles). This phase transition can also be explained because of the increasing critical micelle concentration of the cationic and anionic (catanionic) surfactant mixture (TTABr and SL) at high glycerin concentration. The phase transition induced by addition of sorbitol can also be studied and compared to the case of adding glycerin. These results may direct toward acquiring an understanding of the phase transition mechanism of catanionic surfactants induced by solvents.

17.
Soft Matter ; 4(4): 805-810, 2008 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-32907186

RESUMO

Reversible phase structural transition from densely packed multilamellar vesicles of cationic and anionic (catanionic) tetradecyltrimethylammonium laurate (TTAL) with an amount of salt (NaBr) to network structures was triggered by chain melting. Phase behavior of catanionic TTAL multilamellar vesicles in aqueous solutions at different concentrations of NaBr with increasing temperature was studied. This phase structural transition is a progressive process and happens at the chain melting, which was monitored by means of Fourier transform infrared (FT-IR) spectroscopy, turbidity and viscosity measurements. Transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) were used to demonstrate the phase structural conversion from vesicles to three-dimensional structures consisting of extended bilayer networks. We found that the phase transition temperature (Tm) was influenced by adding amount of salt but not by being diluted. This is the first time that the phase conversion from catanionic surfactant vesicles to bilayer networks triggered by chain melting has been observed. The phase structural transition should arise from the enhanced membrane elasticity accompanying the catanionic surfactant state fluctuations on chain melting and the solvent-associated interactions including cationic and anionic surfactant electrostatic interaction, which favors a change in membrane curvature. We hope this phase conversion observed in catanionic surfactants in aqueous solution will provide good insight into the nature of the fusion or fission processes and the fluctuation of catanionic vesicular systems.

18.
Soft Matter ; 3(11): 1407-1412, 2007 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-32900121

RESUMO

Reversible phase transition between salt-free cationic and anionic (catanionic) tetradecyltrimethylammonium laurate (TTAL) birefringent L-phase solution with uni- and multilamellar vesicles and high-salinity catanionic vesicles was studied. With increasing concentration of NaBr, the salt-free catanionic birefringent Lα-phase formed by cationic tetradecyltrimethylammonium hydroxide (TTAOH) mixing with lauric acid in equimolar ammounts in aqueous solution was transferred into a two-phase precipitate-L-phase, and finally a birefringent L-phase again at much higher salt concentration. The uni- and multilamellar vesicles of birefringent L-phases without salt and with much higher salts were determined by freeze-fracture transmission electron microscopy (FF-TEM) images. The precipitates being the top phase at the two-phase region were also determined by means of FF-TEM images, which consist of densely packed multilamellar vesicles. The phase transition from salt-free catanionic birefringent L-phase to the one with much higher salinity is reversible, which could be achieved by removing the salts through dialysis. Salt-free catanionic birefringent L-phase with uni- and multilamellar vesicles, the densely packed multilamellar vesicles of precipitates that have a lower density than water to another birefringent L-phase at high-salinity, and also the reversible process should improve our understanding of self-assembled structures of surfactants in completely different solvents such as in pure water and ionic liquid media, which may make a significant impact on surfactant sciences.

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