Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 26
Filtrar
Mais filtros










Base de dados
Tipo de estudo
Intervalo de ano de publicação
1.
Chirality ; 32(3): 378-386, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31958185

RESUMO

A series of chiral 5-hydroxy isoxazolidines has been successfully synthesized through camphor sulfonyl hydrazine-catalyzed asymmetric aza-Michael addition reaction between N,O-protected hydroxyamines and enals. Moderate yields with moderate to good enantioselectivities (up to 96% enantiomeric excess [ee]) were achieved. It provides an alternative asymmetric approach to preparing isoxazolidine derivatives.

2.
Artigo em Inglês | MEDLINE | ID: mdl-31990753

RESUMO

: Inherited antithrombin deficiency (OMIM 107300) is a rare autosomal dominant disorder that could increase the risk of venous thromboembolism and is usually caused by mutations of SERPINC1. Herein, we present a case of a novel mutation in the SERPINC1 gene in a Chinese patient. The patient was a 54-year-old man who presented with recurrent venous thromboembolism and was without a recent history of any precipitating factors. Whole exome sequencing and Sanger sequencing identified a novel heterozygous variant on exon 2 of SERPINC1 gene (c.142G>A, p.P48S).

3.
Planta Med ; 2020 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-31975362

RESUMO

Non-alcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide. Nevertheless, no first-line therapy exists. Hepatic steatosis is the earliest stage of NAFLD, which is characterized by an accumulation of hepatic lipids. Patchouli oil (PO), which is isolated from the well-known Chinese herb named Pogostemon cablin (Blanco) Benth. (Lamiaceae), inhibits hepatic lipid accumulation effectively. However, its potential ability for the treatment of NAFLD had not been reported before. Thus, the objective of this study was to investigate the effectiveness of PO against hepatic steatosis and its underlying mechanisms. We used a high fat diet (HFD)-induced hepatic steatosis model of rats to estimate the effect of PO against NAFLD. Hematoxylin-eosin and oil red O staining were used to analyze the hepatic histopathological changes. ELISA, RT-qPCR, and Western blotting analysis were applied to evaluate the parameters for hepatic steatosis. Our results showed that PO significantly attenuated the lipid profiles and the serum enzymes, evidenced by quantitative and histopathological analyses. It also markedly down-regulated the expression of sterol regulatory element-binding protein 1 (SREPB-1c) with its downstream factors in de novo lipogenesis. And, likewise, in lipid export by very low-density lipoproteins (VLDL), related molecules were dramatically improved. Furthermore, PO observably normalized the aberrant peroxisome proliferator-activated receptor α (PPAR-α) signal in fatty acids oxidation. In conclusion, PO exerted a preventing effect against HFD-induced steatosis and might be due to decrease de novo lipogenesis, promote export of lipids, as well as owing to improve fatty acids oxidation.

4.
Am J Transl Res ; 11(5): 2908-2924, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31217863

RESUMO

Current clinical approaches to treat irradiation-induced salivary gland hypofunction are ineffective. We previously reported that adipose-derived stem cell (ADSC)-based therapy ameliorates damaged salivary gland function in mice and that the effects were enhanced when the therapy was co-administrated with platelet-rich fibrin (PRF). We examined the feasibility of ADSC transdifferentiation into salivary gland acinar-like cells (SGALCs) and analyzed the potential of PRF to promote the transdifferentiation process in vitro. Salivary gland cells (SGCs) and ADSCs were indirectly co-cultured using Transwell inserts, and increasing concentrations of PRF-conditioned medium were applied to the co-culture system. The expression of α-amylase and AQP-5 were used to evaluate ADSC transdifferentiation. Notably, on day 7, 14, and 21, expression of both α-amylase and AQP-5 were detected in the co-cultured ADSCs. Additionally, PRF increased α-amylase and AQP-5 levels in ADSCs that were co-cultured for 7 days. These data demonstrate that ADSCs have the potential to transdifferentiate into SGALCs and that PRF can promote the transdifferentiation process. Therefore, these data reveal a possible mechanism to treat irradiation-induced salivary gland hypofunction and have translational medicine implications.

5.
Org Biomol Chem ; 17(4): 885-891, 2019 01 23.
Artigo em Inglês | MEDLINE | ID: mdl-30628602

RESUMO

Organocatalytic asymmetric Michael addition between 3-substituted oxindoles and enals catalyzed by chiral camphor sulfonyl hydrazines (CaSHs) has been developed. A wide range of 3-substituted oxindoles and enals were successfully used, giving the corresponding 3,3-disubstituted oxindoles containing vicinal stereogenic carbon centers in good yields with good to excellent enantioselectivities and moderate to good diastereoselectivities (up to 89% yield, 99% ee and 99 : 1 dr).

6.
Chin J Nat Med ; 16(5): 366-374, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29860998

RESUMO

Analysis errors can occur in the desorbing process of ginkgo diterpene lactone meglumine injection (GDMI) by a conventional analysis method, due to several factors, such as easily crystallized samples, solvent volatility, time-consuming sample pre-processing, fixed method, and offline analysis. Based on risk management, near-infrared (NIR) and mid-infrared (MIR) spectroscopy techniques were introduced to solve the above problems with the advantage of timely analysis and non-destructive nature towards samples. The objective of the present study was to identify the feasibility of using NIR or MIR spectroscopy techniques to increase the analysis accuracy of samples from the desorbing process of GDMI. Quantitative models of NIR and MIR were established based on partial least square method and the performances were calculated. Compared to NIR model, MIR model showed greater accuracy and applicability for the analysis of the GDMI desorbing solutions. The relative errors of the concentrations of Ginkgolide A (GA) and Ginkgolide B (GB) were 2.40% and 2.89%, respectively, which were less than 5.00%. The research demonstrated the potential of the MIR spectroscopy technique for the rapid and non-destructive quantitative analysis of the concentrations of GA and GB.


Assuntos
Química Farmacêutica/métodos , Ginkgolídeos/análise , Meglumina/análise , Gestão de Riscos , Espectrofotometria Infravermelho/normas , Química Farmacêutica/normas , Composição de Medicamentos/normas , Medicamentos de Ervas Chinesas/análise , Medicamentos de Ervas Chinesas/química , Medicamentos de Ervas Chinesas/normas , Ginkgolídeos/química , Ginkgolídeos/normas , Injeções , Lactonas/análise , Análise dos Mínimos Quadrados , Meglumina/química , Meglumina/normas , Reprodutibilidade dos Testes
7.
Rejuvenation Res ; 20(3): 231-243, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28056664

RESUMO

This study was designed to explore how supercritical fluid CO2 extract of Ligusticum chuanxiong Hort (CX) protects mouse liver and kidney from d-galactose-induced injury. The antioxidant capacity of CX was confirmed both in vitro and in vivo. The d-galactose-induced malondialdehyde increase was attenuated by CX, as well as the increase in aspartate aminotransferase, alanine aminotransferase, blood urea nitrogen, and creatinine level. In addition, the activities of antioxidant enzymes were markedly renewed, and the gene expressions of these enzymes were upregulated in CX groups. The results of histological analysis suggested that CX could effectively attenuate the d-galactose-induced structure damage. Furthermore, results of Western blotting analysis showed that CX significantly inhibited the upregulation of nuclear factor protein expression caused by d-galactose. In conclusion, CX could attenuate the liver and kidney injury in d-galactose-treated mice, and the mechanism might be associated with attenuating oxidative stress and inflammatory response.


Assuntos
Dióxido de Carbono/química , Cromatografia com Fluido Supercrítico , Rim/lesões , Ligusticum/química , Fígado/lesões , Extratos Vegetais/farmacologia , Substâncias Protetoras/farmacologia , Envelhecimento/patologia , Alanina Transaminase/sangue , Animais , Antioxidantes/farmacologia , Aspartato Aminotransferases/sangue , Nitrogênio da Ureia Sanguínea , Peso Corporal/efeitos dos fármacos , Creatinina/sangue , Ciclo-Oxigenase 2/metabolismo , Galactose , Cromatografia Gasosa-Espectrometria de Massas , Regulação da Expressão Gênica/efeitos dos fármacos , Inflamação/patologia , Concentração Inibidora 50 , Rim/efeitos dos fármacos , Rim/enzimologia , Rim/patologia , Peroxidação de Lipídeos/efeitos dos fármacos , Fígado/efeitos dos fármacos , Fígado/enzimologia , Fígado/patologia , Masculino , Camundongos , NF-kappa B/metabolismo , Óxido Nítrico Sintase Tipo II/metabolismo , Especificidade de Órgãos , Extratos Vegetais/química
8.
Cancer Res ; 77(6): 1345-1356, 2017 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-28108513

RESUMO

Cancer cells typically experience higher oxidative stress than normal cells, such that elevating pro-oxidant levels can trigger cancer cell death. Although pre-exposure to mild oxidative agents will sensitize cancer cells to radiation, this pre-exposure may also activate the adaptive stress defense system in normal cells. Ascorbic acid is a prototype redox modulator that when infused intravenously appears to kill cancers without injury to normal tissues; however, the mechanisms involved remain elusive. In this study, we show how ascorbic acid kills cancer cells and sensitizes prostate cancer to radiation therapy while also conferring protection upon normal prostate epithelial cells against radiation-induced injury. We found that the NF-κB transcription factor RelB is a pivotal determinant in the differential radiosensitization effects of ascorbic acid in prostate cancer cells and normal prostate epithelial cells. Mechanistically, high reactive oxygen species concentrations suppress RelB in cancer cells. RelB suppression decreases expression of the sirtuin SIRT3 and the powerful antioxidant MnSOD, which in turn increases oxidative and metabolic stresses in prostate cancer cells. In contrast, ascorbic acid enhances RelB expression in normal cells, improving antioxidant and metabolic defenses against radiation injury. In addition to showing how RelB mediates the differential effects of ascorbic acid on cancer and normal tissue radiosensitivities, our work also provides a proof of concept for the existence of redox modulators that can improve the efficacy of radiotherapy while protecting against normal tissue injury in cancer settings. Cancer Res; 77(6); 1345-56. ©2017 AACR.


Assuntos
Ácido Ascórbico/farmacologia , Estresse Oxidativo/efeitos dos fármacos , Próstata/efeitos dos fármacos , Neoplasias da Próstata/tratamento farmacológico , Radiossensibilizantes/farmacologia , Fator de Transcrição RelB/metabolismo , Animais , Antioxidantes/farmacologia , Apoptose/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Células Cultivadas , Humanos , Masculino , Camundongos , Camundongos Nus , Estresse Oxidativo/efeitos da radiação , Próstata/citologia , Próstata/metabolismo , Neoplasias da Próstata/metabolismo , Neoplasias da Próstata/patologia , Tolerância a Radiação/efeitos dos fármacos , Radiação Ionizante , Espécies Reativas de Oxigênio/metabolismo , Superóxido Dismutase/metabolismo , Ensaios Antitumorais Modelo de Xenoenxerto
9.
Zhongguo Zhong Xi Yi Jie He Za Zhi ; 37(4): 419-421, 2017 04.
Artigo em Chinês | MEDLINE | ID: mdl-30650497

RESUMO

Objective To observe the effect of Modified Dachengqi Decoction on recovery of gastrointestinal function after closure of protective ileostomy of rectal cancer. Methods Seventy pa- tients with rectal cancer, scheduled to receive protective ileostomy were enrolled and randomized into treatment group (35 cases) and control group (35 cases). The treatment group was subjected to ante-grade enema with Modified Dachengqi Decoction (500 mL) once a day before ileostomy, the therapeutic course was 2 weeks ,and the control group received ileostomy alone. The oral feeding time, anal exhaust time, ileus rate and length of hospital stay were observed. Results Compared with the control group, the oral feeding time(h,22 ±6 vs.41 ±8), anal exhaust time(h,27 ±5 vs.48 ±8), ileus rate(2. 85% vs. 14. 29%) and length of hospital stay ( d,5. 5 ± 1. 0 vs.7. 6 ± 1. 2) were decreased in the treatment group (P <0. 01 , P <0. 05).Conclusion Modified Dachengqi Decoction could promote the recovery of gastroin- testinal function after surgery in patients with rectal cancer.


Assuntos
Trato Gastrointestinal , Ileostomia , Extratos Vegetais , Recuperação de Função Fisiológica , Neoplasias Retais , Trato Gastrointestinal/efeitos dos fármacos , Trato Gastrointestinal/fisiologia , Humanos , Íleus , Extratos Vegetais/uso terapêutico , Complicações Pós-Operatórias , Neoplasias Retais/cirurgia , Resultado do Tratamento
10.
Sheng Li Xue Bao ; 68(3): 255-64, 2016 Jun 25.
Artigo em Chinês | MEDLINE | ID: mdl-27350198

RESUMO

The effective connectivity of default mode network (DMN) and its change after taking methylphenidate (MPH) were investigated in this study based on resting-state functional magnetic resonance imaging. Dynamic causal modeling (DCM) was applied to compare the effective connectivity between the conditions of taking MPH and placebo for 18 healthy male volunteers. Started with the network structural basis provided by a recent literature, endogenous low frequency fluctuation signals (0.01-0.08 Hz) of each node of DMN were taken as the driving input, and thirty-two possible models were designed according to the modulation effect of MPH on different connections between nodes. Model fitting and Bayesian model selection were performed to find the winning model and corresponding parameters. Our results indicated that the effective connectivity from medial prefrontal cortex (MPFC) to posterior cingulated cortex (PCC), from left/right inferior parietal lobule (L/RIPL) to MPFC, and from RIPL to PCC were excitatory, whereas the connectivity from LIPL to PCC was inhibitory. Further t-test statistics on connectivity parameters found that MPH significantly reduced the link from RIPL to MPFC in DMN (t = 2.724, P = 0.016) and changed the weak excitatory state to inhibitory state. However, it had no significant effect on other connections. In all, our results demonstrated that MPH modulates the effective connectivity within DMN in resting state.


Assuntos
Imagem por Ressonância Magnética , Teorema de Bayes , Feminino , Giro do Cíngulo , Humanos , Masculino , Metilfenidato , Lobo Parietal , Córtex Pré-Frontal
11.
Nanoscale ; 7(26): 11393-400, 2015 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-26073879

RESUMO

The critical doping structures of rare-earth atoms in the promising ß-SiAlON phosphors have long been argued owing to the lack of direct evidence. Here, the exact locations and coordination of the Ce rare-earth atoms in the ß-SiAlON structure have been examined using an atom-resolved Cs-corrected scanning transmission electron microscope. Three different occupation sites for the Ce atoms have been directly observed: two of them are in the structural channel coordinated with six and nine N(O) atoms, respectively; the other one is the unexpected substitution site for Si(Al). The chemical valences and stabilities of the doping Ce ions at the different occupation sites have been evaluated using density functional calculations. Correlation of the different doping structures with the luminescence properties has been investigated by the aid of cathodoluminescence (CL) microanalysis, which verifies the different contribution of the interstitial trivalent Ce ions to the light emission while no luminescence is observed for the substitutional doping of quadrivalent Ce.

12.
Zhongguo Zhong Yao Za Zhi ; 40(1): 79-83, 2015 Jan.
Artigo em Chinês | MEDLINE | ID: mdl-25993792

RESUMO

In this study, hydrophilic matrix sustained release tablets of total lactones from Andrographis paniculata were prepared and the in vitro release behavior were also evaluated. The optimal prescription was achieved by studying the main factor of the type and amount of hydroxypropyl methylcellulose (HPMC) using single factor test and evaluating through cumulative release of three lactones. No burst drug release from the obtained matrix tablets was observed. Drug release sustained to 14 h. The release mechanism of three lactones from A. paniculata was accessed by zero-order, first-order, Higuchi and Peppas equation. The release behavior of total lactones from A. paniculata was better agreed with Higuchi model and the drug release from the tablets was controlled by degradation of the matrix. The preparation of hydrophilic matrix sustained release tablets of total lactones from A. paniculata with good performance of drug release was simple.


Assuntos
Andrographis/química , Preparações de Ação Retardada/química , Composição de Medicamentos/métodos , Medicamentos de Ervas Chinesas/química , Lactonas/química , Interações Hidrofóbicas e Hidrofílicas , Cinética , Comprimidos/química
13.
Artigo em Inglês | MEDLINE | ID: mdl-25864014

RESUMO

In this study, a sensitive and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated to simultaneously determinate andrographolide (AP), dehydroandrographolide (DP), and neoandrographolide (NP) in plasma of beagle dogs after oral administration of Andrographis paniculata tablet (A. paniculata). The analytes and bilobalide (internal standard) were separated on an Agilent ZORBAX XDB-C18 column (50mm×2.1mm, 3.5µm) by using gradient elution consisting of methanol and water at a flow rate of 0.50mL/min in 7min. Multiple reaction monitoring (MRM) mode was performed to quantify data under monitoring precursor-product ion transitions of m/z 348.8→286.9, 330.9→107.9, 479.1→160.8 and 325.0→163.0 for AP, DP, NP and internal standard (IS) at negative ion mode, respectively. This method was developed at linearity ranging from 0.50 to 250ng/mL for AP, 1.00 to 500ng/mL for DP and 0.20 to 100ng/mL for NP. The accuracy of each analyte ranged between 94.8% and 107.1% and the precision was within 14.6%. No significant matrix effect was observed. AP, DP and NP were stable during sample storage, preparation and analytic procedures. Furthermore, this method was successfully applied in the investigation of the pharmacokinetic profile of AP, DP and NP in beagle dogs after oral administration of A. paniculata tablet (49.5mg for AP, 7.0mg for DP, 22.0mg for NP). Biological half-life (t1/2) was 2.08±0.99, 3.13±1.19 and 1.07±0.38h for AP, DP and NP, respectively. The areas under curves (AUC0-t) of AP, DP and NP was 494.50±150.64, 26.01±8.72 and 78.78±18.29ngh/mL, respectively.


Assuntos
Cromatografia Líquida/métodos , Diterpenos/sangue , Glucosídeos/sangue , Espectrometria de Massas em Tandem/métodos , Tetra-Hidronaftalenos/sangue , Andrographis , Animais , Diterpenos/química , Diterpenos/farmacocinética , Cães , Estabilidade de Medicamentos , Glucosídeos/química , Glucosídeos/farmacocinética , Modelos Lineares , Masculino , Extratos Vegetais/administração & dosagem , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Tetra-Hidronaftalenos/química , Tetra-Hidronaftalenos/farmacocinética
14.
Microbes Environ ; 29(4): 388-92, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25381715

RESUMO

Concern regarding household biofilms has grown due to their widespread existence and potential to threaten human health by serving as pathogen reservoirs. Previous studies identified Methylobacterium as one of the dominant genera found in household biofilms. In the present study, we examined the mechanisms underlying biofilm formation by using the bacterial consortium found in household pink slime. A clone library analysis revealed that Methylobacterium was the predominant genus in household pink slime. In addition, 16 out of 21 pink-pigmented bacterial isolates were assigned to the genus Methylobacterium. Although all of the Methylobacterium isolates formed low-level biofilms, the amount of the biofilms formed by Methylobacterium sp. P-1M and P-18S was significantly increased by co-culturing with other Methylobacterium strains that belonged to a specific phylogenetic group. The single-species biofilm was easily washed from the glass surface, whereas the dual-species biofilm strongly adhered after washing. A confocal laser scanning microscopy analysis showed that the dual-species biofilms were significantly thicker and tighter than the single-species biofilms.


Assuntos
Biofilmes/crescimento & desenvolvimento , Microbiologia Ambiental , Methylobacterium/fisiologia , Interações Microbianas , Pigmentos Biológicos , Análise por Conglomerados , DNA Ribossômico/química , DNA Ribossômico/genética , Características da Família , Humanos , Methylobacterium/classificação , Methylobacterium/crescimento & desenvolvimento , Methylobacterium/isolamento & purificação , Microscopia Confocal , Dados de Sequência Molecular , Filogenia , Pigmentos Biológicos/análise , RNA Ribossômico 18S/genética , Análise de Sequência de DNA
15.
J Asian Nat Prod Res ; 14(2): 135-40, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22296154

RESUMO

Two new methyl-migrated 16,17-seco-dammarane triterpenoid saponins, named acerboside A (1) and acerboside B (2), were isolated from the seeds of Hovenia acerba. Their structures were elucidated on the basis of spectroscopic analysis and hydrolysis.


Assuntos
Medicamentos de Ervas Chinesas/isolamento & purificação , Rhamnaceae/química , Saponinas/isolamento & purificação , Triterpenos/isolamento & purificação , Medicamentos de Ervas Chinesas/química , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Saponinas/química , Sementes/química , Triterpenos/química
16.
Appl Environ Microbiol ; 78(10): 3614-21, 2012 May.
Artigo em Inglês | MEDLINE | ID: mdl-22344668

RESUMO

The toxicity of soft metals is of broad interest to microbiologists, both because such metals influence the community structures in natural environments and because several metals are used as antimicrobial agents. Their potency roughly parallels their thiophilicity, suggesting that their primary biological targets are likely to be enzymes that contain key sulfhydryl moieties. A recent study determined that copper poisons Escherichia coli in part by attacking the exposed [4Fe-4S] clusters of dehydratases. The present investigation sought to test whether other soft metals also target these enzymes. In vitro experiments revealed that low-micromolar concentrations of Ag(I) and Hg(II) directly inactivated purified fumarase A, a member of the dehydratase family. The enzyme was also poisoned by higher levels of Cd(II) and Zn(II), but it was unaffected by even millimolar concentrations of Mn(II), Co(II), Ni(II), and Pb(II). Electron paramagnetic resonance analysis and measurements of released iron confirmed that damage was associated with destruction of the [4Fe-4S] cluster, and indeed, the reconstruction of the cluster fully restored activity. Growth studies were then performed to test whether dehydratase damage might underlie toxicity in vivo. Barely toxic doses of Ag(I), Hg(II), Cd(II), and Zn(II) inactivated all tested members of the [4Fe-4S] dehydratase family. Again, activity was recovered when the clusters were rebuilt. The metals did not diminish the activities of other sampled enzymes, including NADH dehydrogenase I, an iron-sulfur protein whose clusters are shielded by polypeptide. Thus, the data indicate that dehydratases are damaged by the concentrations of metals that initiate bacteriostasis.


Assuntos
Inibidores Enzimáticos/toxicidade , Escherichia coli/efeitos dos fármacos , Metais Pesados/toxicidade , Inibidores Enzimáticos/metabolismo , Escherichia coli/crescimento & desenvolvimento , Metais Pesados/metabolismo , Compostos de Sulfidrila/metabolismo
17.
Artigo em Chinês | MEDLINE | ID: mdl-21619824

RESUMO

OBJECTIVE: To evaluate the effects of health promotion on occupational health based on the changes in knowledge, attitude and practice (KAP) before and after intervention of people with occupational disease risk in private enterprises. METHODS: 202 people with occupational disease risk in private leather enterprises of Wenzhou were surveyed, who were rechecked with the same questionnaire after three months intervention. RESULTS: The knowledge, attitude and practice scores (9.34 ± 2.57, 7.79 ± 2.58 and 7.24 ± 2.50, respectively) of post-intervention group were significantly increased more than those of pre-intervention (8.06 ± 2.71, 7.63 ± 2.67, 7.11 ± 2.60, respectively) (P < 0.01, P < 0.05). The net increases of knowledge, attitude and practice scores were significantly different with different length of service, educational level, registered residence and training experience (P < 0.05, P < 0.01). CONCLUSIONS: Health promotion could increase knowledge, attitude and practice levels; The effect of intervention on people with short length of service, low educational level, coming from country and had not attended training is significant.


Assuntos
Conhecimentos, Atitudes e Prática em Saúde , Promoção da Saúde , Exposição Ocupacional/prevenção & controle , Serviços de Saúde do Trabalhador , Setor Privado , Adolescente , Adulto , Feminino , Humanos , Masculino , Inquéritos e Questionários , Adulto Jovem
18.
Langmuir ; 26(10): 7535-9, 2010 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-20104913

RESUMO

Mesoporous thin films synthesized via an electrochemical strategy (ref 1) generally show granular domains, each of which is composed of hexagonally packed one-dimensional channels oriented uniquely perpendicular to the film surface. Grain boundaries either parallel or normal to the channel direction might affect the properties and subsequent application of the film. In this study, the structural details of oriented mesostructured silica thin films have been examined by transmission electron microscope. The pore structures are characterized using the traditional crystallographic concepts but show different structural properties from that of polycrystalline materials. The boundary structures vary much depending on the residual internal stress and the orientation relationship between the bounded grains. A variety of structural features, typically near the large-angle tilt boundaries, have been observed including coincidence site lattices, lattice distortion, lattice displacement, and dislocations. According to the present structural analysis, microstructure evolution and potential applications have been discussed with respect to the oriented mesoporous films.

20.
J Am Chem Soc ; 127(48): 16860-5, 2005 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-16316232

RESUMO

Bending strains and bonding structures of GaS multiwalled submicrotubes have been examined by transmission electron microscopy. Experimental observations reveal that the strain involved in building the GaS tubes is more complicated than the theoretical prediction and appears anisotropic and dependent on the tubular configurations. The armchair tube bears a larger lattice compression than the zigzag tube. The hexagonal GaS semiconducting compound degrades its crystal symmetry upon bending, leading to the anisotropy of the bonding structures. Curving of GaS sheets to form tubes is found to be dominated by the structures and electrostatic fields on the sheet surface, which eventually gives a well-controlled tubular structure showing preferred zigzag and close-to-zigzag configurations. Finally, interlayer packing structures of multiwalled tubes are examined.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA