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










Base de dados
Intervalo de ano de publicação
1.
Int J Biol Macromol ; 154: 878-887, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32173428

RESUMO

A series of agar/κ-carrageenan mixed hydrogels with different mass ratios were prepared, and their physicochemical properties, gelling behavior and drug release performance were determined and analyzed. The results showed that the gel strength, the gelling temperature and the gel melting temperature decreased with the increase of κ-carrageenan, while the apparent viscosities increased. Optical rotation and differential scanning calorimetry (DSC) indicated that there did exist intermolecular interactions between agar and κ-carrageenan, and the detailed gelling mechanism of the mixed hydrogels was proposed, which was different from that of the previous research. Besides, agar/κ-carrageenan mixed hydrogels were used as carriers for the delivery of metformin hydrochloride (MET). The results showed that the drug loading efficiency and the sustained release capacity of agar hydrogels could be enhanced by the addition of κ-carrageenan, and the release profile was mainly dominated by the electrostatic interaction between the MET and the polysaccharides. These results indicated that κ-carrageenan had the potential to improve the physicochemical properties and drug release performance of agar hydrogel.

2.
J Diabetes Investig ; 2019 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-31667982

RESUMO

AIMS/INTRODUCTION: The relationship between ferritin and the risk of gestational diabetes mellitus (GDM) has not been established. Thus, we carried out a meta-analysis based on the current literature. MATERIALS AND METHODS: We searched relevant databases on Embase, PubMed, Cochrane Library and Web of Science before 10 May 2019 to determine the relationship between ferritin and the risk of GDM. The relative risks and 95% confidence intervals of GDM risk were summarized using a random effects model. Studies using categories of ferritin as exposure were combined by dose-response analysis. We carried out both linear and non-linear trends. We also carried out subgroup analysis, whether or not the studies adjusted for potential confounders, and meta-regression analysis to explore the source of heterogeneity. Sensitivity analysis was carried out to explore the robustness of the meta-analysis results. RESULTS: A total of 10 studies involving 4,690 participants were identified. The summary relative risk comparing persons with the highest concentration categories of ferritin with the lowest concentration categories of ferritin was 1.87 (95% confidence interval 1.50-2.34; I2  = 20.1%). Linear dose-response showed that an increase in ferritin of 10 µg/L increased the risk of GDM by 8% (1.08, 95% confidence interval 1.05-1.13, I2  = 55.1%; n = 4). A non-linear dose-response relationship also showed a consistently increasing risk of GDM with increased ferritin. No evidence of publication bias was detected. CONCLUSIONS: The findings from this meta-analysis suggest that increased ferritin levels are associated with an increased risk of GDM; however, we require further prospective cohort studies to confirm the results, especially the dose-response relationship between ferritin and GDM.

3.
Nanoscale ; 11(31): 14698-14706, 2019 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-31343043

RESUMO

Two-dimensional (2D) materials provide a plethora of novel condensed matter physics and are the new playground in materials science, offering potentially vast applications. One of the critical hurdles for many 2D systems is the synthesis of these low-dimensional systems as well as the prediction and identification of new candidates. Herein, a self-assembly of a monolayer tellurene by bonding CdTe wafers is demonstrated for the first time. The conventional applications of wafer-bonding range from the production of microelectromechanical systems to the synthesis of lattice-mismatched multi-junction photovoltaics. Due to the heterogeneous materials that are typically employed, the bond-interface usually contains a thin amorphous layer or arrays of dislocations. Such an interface is thus itself inactive and in many cases has detrimental effects on the device. The new material phase stabilized in this work consists of an undulating monolayer of tellurium atoms covalently bonded to {111} Cd-terminated CdTe wafer surfaces. First-principles calculations and experimentally observed changes in the localized plasmon excitation energy indicate the clear rearrangement of the underlying band-structure suggesting a metallic character, bands showing linear dispersion, and a significant asymmetric spin-band splitting. The I-V characteristics show the presence of a highly conductive pathway that lowers the resistivity by three orders of magnitude, as compared to bulk CdTe, which can be attributed to the tellurium monolayer. The findings indicate that suitably chosen crystallographic wafer surfaces can act as structural templates allowing the production of exotic phases. The presently stabilized monolayer is an addition to the family of tellurene variants, providing new insights into the fundamental properties of this and other emerging 2D materials, while attracting attention to the unusual side of the wafer-bonding technology exemplified in this study.

4.
Nanoscale Res Lett ; 14(1): 149, 2019 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-31049737

RESUMO

In this work, flip-chip AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) with various meshed contact structures are systematically investigated via three-dimensional finite-difference time-domain (3D FDTD) method. It is observed that both transverse electric (TE)- and transverse magnetic (TM)-polarized light extraction efficiencies (LEEs) are sensitive to the spacing and inclined angle for the meshed structure. We also find that the LEE will not be increased when a large filling factor is adopted for the meshed structures, which is because of the competition among the p-GaN layer absorption, the Al metal plasmon resonant absorption, and the scattering effect by meshed structures. The very strong scattering effect occurring in the hybrid p-GaN nanorod/p-AlGaN truncated nanocone contacts can enormously enhance the LEE for both TE- and TM-polarized light, e.g., when the inclined angle is 30°, the LEE for the TE- and TM-polarized light can be increased by ~ 5 times and ~ 24 times at the emission wavelength of 280 nm, respectively.

5.
BMC Med ; 16(1): 205, 2018 11 12.
Artigo em Inglês | MEDLINE | ID: mdl-30415641

RESUMO

BACKGROUND: In 2005, the FDA cautioned that exposure to paroxetine, a selective serotonin reuptake inhibitor (SSRI), during the first trimester of pregnancy may increase the risk of cardiac malformations. Since then, the association between maternal use of SSRIs during pregnancy and congenital malformations in infants has been the subject of much discussion and controversy. The aim of this study is to systematically review the associations between SSRIs use during early pregnancy and the risk of congenital malformations, with particular attention to the potential confounding by indication. METHODS: The study protocol was registered with PROSPERO (CRD42018088358). Cohort studies on congenital malformations in infants born to mothers with first-trimester exposure to SSRIs were identified via PubMed, Embase, Web of Science, and the Cochrane Library databases through 17 January 2018. Random-effects models were used to calculate summary relative risks (RRs). RESULTS: Twenty-nine cohort studies including 9,085,954 births were identified. Overall, use of SSRIs was associated with an increased risk of overall major congenital anomalies (MCAs, RR 1.11, 95% CI 1.03 to 1.19) and congenital heart defects (CHD, RR 1.24, 95% CI 1.11 to 1.37). No significantly increased risk was observed when restricted to women with a psychiatric diagnosis (MCAs, RR 1.04, 95% CI 0.95 to 1.13; CHD, RR 1.06, 95% CI 0.90 to 1.26). Similar significant associations were observed using maternal citalopram exposure (MCAs, RR 1.20, 95% CI 1.09 to 1.31; CHD, RR 1.24, 95% CI 1.02 to 1.51), fluoxetine (MCAs, RR 1.17, 95% CI 1.07 to 1.28; CHD, 1.30, 95% CI 1.12 to 1.53), and paroxetine (MCAs, RR 1.18, 95% CI 1.05 to 1.32; CHD, RR 1.17, 95% CI 0.97 to 1.41) and analyses restricted to using women with a psychiatric diagnosis were not statistically significant. Sertraline was associated with septal defects (RR 2.69, 95% CI 1.76 to 4.10), atrial septal defects (RR 2.07, 95% CI 1.26 to 3.39), and respiratory system defects (RR 2.65, 95% CI 1.32 to 5.32). CONCLUSIONS: The evidence suggests a generally small risk of congenital malformations and argues against a substantial teratogenic effect of SSRIs. Caution is advisable in making decisions about whether to continue or stop treatment with SSRIs during pregnancy.


Assuntos
Anormalidades Induzidas por Medicamentos/etiologia , Inibidores de Captação de Serotonina/efeitos adversos , Anormalidades Induzidas por Medicamentos/epidemiologia , Estudos de Coortes , Feminino , Humanos , Lactente , Gravidez , Primeiro Trimestre da Gravidez , Risco
6.
ACS Appl Mater Interfaces ; 10(49): 42387-42396, 2018 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-30422623

RESUMO

Lattice modification by incorporating heteroatoms could effectively and precisely tune their intrinsic properties to get improved sinterability and electrochemical performance. Here, by introducing Cu2+ into the interstitial position of a ABO3-type perovskite, a 2 times higher protonic conductivity (1.9 × 10-2 S cm-1 at 700 °C) and low-temperature (1200 °C) sinterability were achieved for the BaCe0.68Zr0.1Y0.1Yb0.1Cu0.02O3-δ (BCZYYC2) electrolyte, compared to the precursor electrolyte. Meanwhile, the modified BCZYYC2 also exhibits excellent chemical stability in high-temperature and high-humidity conditions, as well as good compatibility with the components of cell. When used as the electrolyte in reversible fuel cell (FC)/electrolysis cell (EC) operational modes, the reversible solid oxide cell with the BCZYYC2 electrolyte illustrates prominent FC (0.85 W cm-2 at 700 °C) and EC (-1.96 A cm-2 at 700 °C and 1.3 V) performances with high film-electrolyte conductivity (8.7 × 10-3 S cm-1 at 700 °C). Additionally, an obvious increase in current density is observed during the short-term stability test, which has shown great promise for their practical application.

7.
J Plant Physiol ; 229: 100-110, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30055519

RESUMO

Improvement of salt tolerance is one of the major targets in rice breeding. Here, we report that the zinc-finger protein (ZFP) OsZFP213 functions in enhancing salt tolerance in rice. OsZFP213 is localized in the nucleus and has transactivation activity. Transgenic rice overexpressing OsZFP213 showed enhanced salt tolerance compared with wild type and OsZFP213 RNAi plants. Furthermore, OsZFP213 overexpression plants showed higher transcription levels of antioxidant system genes and higher catalytic activity of scavenging enzymes of reactive oxygen, such as superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and glutathione reductase (GR), and a lower level of ROS accumulation than that in wild type and OsZFP213 RNAi plants under salt treatment. Yeast two-hybrid, pull-down, and BiFC analysis showed that OsMAPK3 is a direct partner of OsZFP213, and this interaction enhanced the transactivation activity of OsZFP213. Taken together, these results suggest that OsZFP213 cooperates with OsMAPK3 in the regulation of rice salt stress tolerance by enhancing the ability of scavenging reactive oxygen.


Assuntos
Oryza/efeitos dos fármacos , Oryza/metabolismo , Proteínas de Plantas/metabolismo , Ascorbato Peroxidases/metabolismo , Catalase/metabolismo , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Glutationa Redutase/metabolismo , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Tolerância ao Sal , Cloreto de Sódio/farmacologia , Superóxido Dismutase/metabolismo
8.
J Colloid Interface Sci ; 498: 239-247, 2017 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-28342307

RESUMO

Pd-Au/TiC electrodes with various three-dimensional structures are obtained by the pulsed potential electro-deposition in PdCl2/HAuCl4 electrolytes. The morphologies of Pd-Au/TiC composite catalysts are significantly dependent on the component of deposited solutions. The surface appearance of Pd-Au catalysts changes from rime-shaped structure, to feather-like construction, then to pineapple root-like structure and finally to flower-like configuration with the increase of PdCl2 content in electrolytes. These particular three-dimensional structures may be very suitable for H2O2 electro-reduction, which assures a high utilization of Pd-Au catalysts and provides a large specific surface area. The electro-catalytic activities of H2O2 reduction on the Pd-Au/TiC electrodes improve as increasing the Pd content in Pd-Au alloy catalysts. The pineapple root-like Pd5Au1/TiC electrode reveals remarkably excellent electrochemical property and desirable stability for catalyzing H2O2 reduction in acid media. The direct peroxide-peroxide fuel cells with a 10 cm3 min-1 flow rate display the open circuit voltage (OCV) of 0.85V and the peak power density of 56.5mWcm-2 at 155mAcm-2 with desirable cell stability, which is much higher than those previously reported.

9.
Polymers (Basel) ; 9(11)2017 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-30965894

RESUMO

Maleic anhydride (MAH) was used as the grafting monomer, which was prepared by melt grafting reaction in the twin screw extruder with dicumyl peroxide (DCP) as the initiator, polylactic acid grafted with maleic anhydride (MAH-g-PLA) was successfully prepared as the interface compatibilizer. The PLA/Wood fiber/MAH-g-PLA composites were prepared by melt blending and injection molding with different proportions of compatibilizer added, within which PLA was for the matrix phase and wood fiber was for the reinforcing phase. The crystallinity, microstructure, thermal stability and dynamic thermomechanical property of the composites were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), thermo gravimetric analyzer (TGA) and dynamic mechanical thermal analysis (DMA). Furthermore, the mechanical and water absorption properties of the composites were also characterized. Results showed that the tensile strength and flexural strength of the composites attained the highest at 30% MAH-g-PLA added, where the crystallinity of the composites also showed the highest value. DMA results showed that the addition of MAH-g-PLA interfacial compatibilizer increased the loss modulus of the composites and improved the toughness. Scanning electron microscopy (SEM) showed that when the MAH-g-PLA was used, wood fiber is well dispersed in the PLA matrix phase, and that the interfacial compatibility between the matrix and the enhanced phase was improved. Therefore, the addition of MAH-g-PLA could improve the interfacial compatibility of PLA/Wood fiber composites and improve the mechanical properties of the composites.

10.
Sci Rep ; 6: 27009, 2016 06 03.
Artigo em Inglês | MEDLINE | ID: mdl-27255415

RESUMO

Extended defects are of considerable importance in determining the electronic properties of semiconductors, especially in photovoltaics (PVs), due to their effects on electron-hole recombination. We employ model systems to study the effects of dislocations in CdTe by constructing grain boundaries using wafer bonding. Atomic-resolution scanning transmission electron microscopy (STEM) of a [1-10]/(110) 4.8° tilt grain boundary reveals that the interface is composed of three distinct types of Lomer dislocations. Geometrical phase analysis is used to map strain fields, while STEM and density functional theory (DFT) modeling determine the atomic structure at the interface. The electronic structure of the dislocation cores calculated using DFT shows significant mid-gap states and different charge-channeling tendencies. Cl-doping is shown to reduce the midgap states, while maintaining the charge separation effects. This report offers novel avenues for exploring grain boundary effects in CdTe-based solar cells by fabricating controlled bicrystal interfaces and systematic atomic-scale analysis.

11.
PLoS One ; 10(4): e0123766, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25923911

RESUMO

To effectively monitor the atmospheric quality of small-scale areas, it is necessary to optimize the locations of the monitoring sites. This study combined geographic parameters extraction by GIS with fuzzy matter-element analysis. Geographic coordinates were extracted by GIS and transformed into rectangular coordinates. These coordinates were input into the Gaussian plume model to calculate the pollutant concentration at each site. Fuzzy matter-element analysis, which is used to solve incompatible problems, was used to select the locations of sites. The matter element matrices were established according to the concentration parameters. The comprehensive correlation functions KA (xj) and KB (xj), which reflect the degree of correlation among monitoring indices, were solved for each site, and a scatter diagram of the sites was drawn to determine the final positions of the sites based on the functions. The sites could be classified and ultimately selected by the scatter diagram. An actual case was tested, and the results showed that 5 positions can be used for monitoring, and the locations conformed to the technical standard. In the results of this paper, the hierarchical clustering method was used to improve the methods. The sites were classified into 5 types, and 7 locations were selected. Five of the 7 locations were completely identical to the sites determined by fuzzy matter-element analysis. The selections according to these two methods are similar, and these methods can be used in combination. In contrast to traditional methods, this study monitors the isolated point pollutant source within a small range, which can reduce the cost of monitoring.


Assuntos
Monitoramento Ambiental , Lógica Fuzzy , Sistemas de Informação Geográfica , Poluentes Atmosféricos/análise , Análise por Conglomerados , Material Particulado/análise
12.
ACS Nano ; 8(4): 3715-23, 2014 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-24641706

RESUMO

The stacking of two-dimensional layered materials, such as semiconducting transition metal dichalcogenides (TMDs), insulating hexagonal boron nitride (hBN), and semimetallic graphene, has been theorized to produce tunable electronic and optoelectronic properties. Here we demonstrate the direct growth of MoS2, WSe2, and hBN on epitaxial graphene to form large-area van der Waals heterostructures. We reveal that the properties of the underlying graphene dictate properties of the heterostructures, where strain, wrinkling, and defects on the surface of graphene act as nucleation centers for lateral growth of the overlayer. Additionally, we show that the direct synthesis of TMDs on epitaxial graphene exhibits atomically sharp interfaces. Finally, we demonstrate that direct growth of MoS2 on epitaxial graphene can lead to a 10(3) improvement in photoresponse compared to MoS2 alone.

13.
Dalton Trans ; 39(41): 9952-5, 2010 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-20877818

RESUMO

Single phase Pb(Ti(0.8)Fe(0.2))O(3-δ) thin films with a thickness of 210 nm and 120 nm were fabricated on Pt/Ti/SiO(2)/Si substrate by a chemical solution deposition technique. The thin film with a thickness of 210 nm showed a homogeneous microstructure, low porosity, low oxygen vacancies, and preferred orientation. It had negligible leakage current and well saturated ferroelectric hysteresis loop compared with the Pb(Ti(0.8)Fe(0.2))O(3-δ) bulk sample. Polarization fatigue characteristic indicated that this film has a potential application as a switcher in some electrical devices. The saturation magnetization in the Fe-doped PbTiO(3) film is weaker than that for bulk sample, and its ferromagnetism is correlated to the F-center exchange (FCE) mechanism. The present results revealed the multiferroic nature of the Pb(Ti(0.8)Fe(0.2))O(3-δ) thin film.

14.
J Phys Chem C Nanomater Interfaces ; 114(17): 7727-7732, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-20440379

RESUMO

Dissociation process of glutathione-gold(I) polymers in aqueous solution resulted in the formation of a class of ~2 nm gold nanoparticles. Different from the same sized but NaBH(4) reduced gold nanoparticles, these nanoparticles exhibit strong luminescence but no surface plasmon absorption. Luminescence lifetimes of the nanoparticles were found strongly dependent on excitation wavelengths, and singlet and triplet excited states involving the emission were found degenerate in energy. X-ray photoelectron spectroscopic studies showed that nearly 40~50% gold atoms in the luminescent nanoparticles were in gold(I) state, which are responsible for the unique optical properties of the luminescent gold nanoparticles. These luminescent nanoparticles can be considered an intermediate state between luminescent gold(I) complexes and reduced nonluminescent gold nanoparticles.

15.
Dalton Trans ; 39(21): 5183-6, 2010 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-20440436

RESUMO

Al-doped PbTiO3 solid solutions were synthesized by a solid state method. Since Al does not have bonding d-orbit or d-electrons, and the substitutions of Al(3+) for Ti(4+) in PbTiO3 is aliovalent, the effect of Al on the structure and spontaneous polarization is quite different from that of Hf, Zr, etc. substitutions in PbTiO3. Usually, the spontaneous polarization is weakened with decreased tetragonality in PbZrxTi1-xO3 and PbHfxTi1-xO3 systems; PbTi1-xAlxO3 (0 ≤ x ≤ 0.10) solid solutions exhibit improved spontaneous polarization with decreased tetragonality (c/a). Lattice dynamics and the crystal structure of PbTi1-xAlxO3 with enhanced spontaneous polarization were investigated by FT-IR, Raman scattering technique, and X-Ray Rietveld method. The Al-doping reinforced the covalence of Pb-O(II), which indicated that the Pb-O hybridization was strengthened. The three transverse optical (TO) modes of A1-symmetry in Raman and the "stretching" and "bending" vibration modes in FTIR further verified the increase of spontaneous polarization (PS) in the A- and B-sites.

16.
17.
Artigo em Inglês | MEDLINE | ID: mdl-12219212

RESUMO

The carbohydrate-binding peptide fragment of scarlet runner bean (Phaseolus coccineus var. rubronanus) lectin has been prepared by trypsin digestion. The carbohydrate-binding peptide was isolated from digested solution by affinity chromatography on thyroglobulin-Sepharose column, Bio-Gel P-4 gel filtration column and reverse phase HPLC on C-8 column. The fraction of peak I from HPLC which bound specifically with Man(8)GlcNAc(2) was demonstrated by using dot blot technique with [(3)H]- Man(8)GlcNAc(2).

18.
Artigo em Inglês | MEDLINE | ID: mdl-12232596

RESUMO

Two oligosaccharide chains from scarlet runner bean (Phaseolus coccineus var. rubronanus) lectin (PCL) were obtained by hydrazinolysis, Bio-Gel P-2 column chromatography, NaBH(4) reduction and then separated on a Bio-Gel P-2 column. The oligosaccharides were methanolysed, acetylysed and then transformed into derivatives of trimethylsilane. Gas chromatographic studies of these two derivatives showed that their compositions were: Man(8)XylGlcNAc(2) (oligosaccharide I) and Man(6)XylGlcNAc(2)Fuc (oligosaccharide II). The size of these two oligosaccharides after digestion by alpha-mannosidase, beta-xylosidase and alpha-fucosidase separately, were determined on a standardized Bio-Gel P-4 column. Thus the sequences of these two oligosaccharides were celucidated as: (Manalpha)(7)ManBetaXylBeta(GlcNAc)(2) and (Manalpha)(5)ManbetaXylbeta(GlcNAc)(2)Fucalpha.

19.
Artigo em Inglês | MEDLINE | ID: mdl-12237695

RESUMO

Four protein components have been isolated from the CHAPS extract of boar spermatozoa by chromatography on PSL-Sepharose affinity column and cellulose CM-52 ion exchange column sequentially. Both boar sperm protein SP1and SP2 exhibited binding activity with the zona pellucida glycoprotein ZP3 by immobilized zona pellucida glycoprotein binding assay (IZPGBA), and SP2 also showed hemagglutinating activity. The protein SP1 obviously inhibited sperm-oocyte binding when it was preincubated with oocytes. The inhibitory activity of SP1 was related to its concentration. By using Western blot technique and biotinylated ZP3, a Zp3-binding spermatozoa protein with molecular weight of 68 kD was identified, which may be a protein involved in sperm-oocyte binding.

20.
Artigo em Inglês | MEDLINE | ID: mdl-12237725

RESUMO

Several neoglycoproteins (Man-BSA, Gal-BSA, Glc-BSA, Lac-BSA, GlcNAc-BSA, Fuc-BSA and Rha-BSA) have been prepared by using homo-bifunctional reagents (divinyl sulfone, DVS and 1,4-butanediol diglycidyl ether, Epoxy) as coupling agents and purilied with the respective immobilized lectins (except Fuc-BSA and Rha-BSA). These purified neoglycoproteins showed binding specificity to the corresponding lectins by hemagglutinating inhibition test and double diffusion experiment.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA