Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 22
Filtrar
1.
Biol Pharm Bull ; 40(12): 2088-2095, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29199233

RESUMO

This study aimed to investigate the effect of hematoporphyrin dimethylether (HDME)-mediated photodynamic therapy for laser-induced choroidal neovascularization (CNV) in adult Brown Norway rats. HDME was administered via tail vein at 14 d after the laser photocoagulation, and the rats received irradiance with a laser light at 570 nm at 15 min after injection. CNV was evaluated by fundus photography, fundus fluorescein angiography, optical coherence tomography, and hematoxylin and eosin staining. We found that CNV was occurred at 7 d after photocoagulation and reaching peak activity at 14 d after photocoagulation. There is a significant reduction in the total area of the fluorescein leakage and the number of strong fluorescein leakage spots on 7 d after HDME-mediated photodynamic therapy (PDT). The results suggest that HDME-mediated PDT inhibits laser-induced CNV in rats, representing a promising therapy for wet age-related macular degeneration.


Assuntos
Neovascularização de Coroide/tratamento farmacológico , Hematoporfirinas/uso terapêutico , Éteres Metílicos/uso terapêutico , Fotoquimioterapia/métodos , Fármacos Fotossensibilizantes/uso terapêutico , Animais , Permeabilidade Capilar , Neovascularização de Coroide/diagnóstico por imagem , Neovascularização de Coroide/etiologia , Modelos Animais de Doenças , Angiofluoresceinografia , Fundo de Olho , Hematoporfirinas/química , Humanos , Lasers/efeitos adversos , Masculino , Éteres Metílicos/química , Fármacos Fotossensibilizantes/química , Ratos , Ratos Endogâmicos BN
2.
Immunol Invest ; 44(2): 126-36, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25083793

RESUMO

Immune dysregulation is a cardinal feature of autoimmune diseases and chronic microbial infections. In particular, regulatory T cells are downregulated in autoimmune diseases while upregulated in chronic microbial infections. FOXP3 is the master regulator of Treg development. Treg-specific demethylated region (TSDR) is a highly conserved locus on the FOXP3 gene that is fully demethylated in natural Tregs but methylated in effector T cells. In our study, we used high resolution melt-polymerase chain reaction (HRM-PCR) to determine the FOXP3 TSDR methylation status in autoimmune diseases and chronic microbial infections. We found that FOXP3 TSDR to have the highest mean melting temperature (highly methylated) in active SLE patients compared to all the other groups (p < 0.001). The psoriasis group also had a significantly high mean melting temperature (78.62 ± 0.20) when compared with the inactive SLE group (78.49 ± 0.29, p < 0.05) and control group (78.44 ± 0.25, p < 0.01). There was no significant difference in melting temperature between inactive SLE and healthy controls. Disease activity in SLE was directly associated with methylation of the FOXP3 TSDR. On the other hand, patients with chronic microbial infections had significantly lower FOXP3 TSDR mean melting temperature (demethylated) when compared with healthy controls (78.28 ± 0.21 vs 78.44 ± 0.25, p < 0.05). Our results suggest that the use of HRM-PCR to detect FOXP3 TSDR methylation status is a reliable and easy method to predict natural regulatory T cell levels in peripheral blood in different disease conditions. Determining FOXP3 TSDR methylation status can be a useful tool in diagnosis, and monitoring the severity of autoimmune diseases and chronic microbial infections.


Assuntos
Doenças Autoimunes/genética , Metilação de DNA , Fatores de Transcrição Forkhead/genética , Infecções/genética , Adulto , Doenças Autoimunes/diagnóstico , Biomarcadores , Doença Crônica , Ilhas de CpG , Feminino , Humanos , Infecções/diagnóstico , Lúpus Eritematoso Sistêmico/diagnóstico , Lúpus Eritematoso Sistêmico/genética , Pessoa de Meia-Idade , Índice de Gravidade de Doença , Linfócitos T Reguladores/metabolismo , Adulto Jovem
3.
Parasitology ; 142(3): 473-9, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25140457

RESUMO

The present study aims to evaluate the antiparasitic activity of active components from Costus speciosus against Ichthyophthirius multifiliis. Bioassay-guided fractionation was employed to identify active compounds from C. speciosus yielding 2 bioactive compounds: Gracillin and Zingibernsis newsaponin. In-vitro assays revealed that Gracillin and Zingibernsis newsaponin could be 100% effective against I. multifiliis at concentrations of 0.8 and 4.5 mg L(-1), with median effective concentration (EC50) values of 0.53 and 3.2 mg L(-1), respectively. All protomonts and encysted tomonts were killed when the concentrations of Gracillin and Zingibernsis newsaponin were 1.0 and 5.0 mg L(-1). In-vivo experiments demonstrated that fish treated with Gracillin and Zingibernsis newsaponin at concentrations of 1.0 and 5.0 mg L(-1) carried significantly fewer parasites than the control (P<0.05). Mortality of fish did not occur in the treatment group (Zingibernsis newsaponin at 5.0 mg L(-1)) during the trial, although 100% of untreated fish died. Acute toxicities (LD50) of Gracillin and Zingibernsis newsaponin for grass carp were 1.64 and 20.7 mg L(-1), respectively. These results provided evidence that the 2 compounds can be selected as lead compounds for the development of new drugs against I. multifiliis.


Assuntos
Carpas/parasitologia , Infecções por Cilióforos/veterinária , Costus/química , Doenças dos Peixes/parasitologia , Hymenostomatida/efeitos dos fármacos , Espirostanos/farmacologia , Animais , Infecções por Cilióforos/tratamento farmacológico , Infecções por Cilióforos/mortalidade , Doenças dos Peixes/tratamento farmacológico , Doenças dos Peixes/mortalidade , Carpa Dourada/parasitologia , Extratos Vegetais/farmacologia , Distribuição Aleatória , Saponinas/farmacologia
4.
J Autoimmun ; 54: 127-36, 2014 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-25091625

RESUMO

Systemic lupus erythematosus (SLE) is an autoimmune disease well known for its clinical heterogeneity, and its etiology secondary to a cross-talk involving genetic predisposition and environmental stimuli. Although genome-wide analysis has contributed greatly to our understanding of the genetic basis of SLE, there is increasing evidence for a role of epigenetics. Indeed, recent data have demonstrated that in patients with SLE, there are striking alterations of DNA methylation, histone modifications, and deregulated microRNA expression, the sum of which contribute to over-expression of select autoimmune-related genes and loss of tolerance. To address this issue at the level of clinical phenotype, we performed DNA methylation, mRNA and microRNA expression screening using high-throughput sequencing of purified CD4+ T cells from patients with SLE, compared to age and sex matched controls. In particular, we studied 42 patients with SLE and divided this group into three clinical phenotypes: a) the presence of skin lesions without signs of systemic pathology; b) skin lesions but also chronic renal pathology; and c) skin lesions, chronic renal pathology and polyarticular disease. Interestingly, and as expected, sequencing data revealed changes in DNA methylation in SLE compared to controls. However, and more importantly, although there were common methylation changes found in all groups of SLE compared to controls, there was specific DNA methylation changes that correlated with clinical phenotype. These included changes in the novel key target genes NLRP2, CD300LB and S1PR3, as well as changes in the critical pathways, including the adherens junction and leukocyte transendothelial migration. We also noted that a significant proportion of genes undergoing DNA methylation changes were inversely correlated with gene expression and that miRNA screening revealed the existence of subsets with changes in expression. Integrated analysis of this data highlights specific sets of miRNAs controlled by DNA methylation, and genes that are altered by methylation and targeted by miRNAs. In conclusion, our findings suggest select epigenetic mechanisms that contribute to clinical phenotypes and further shed light on a new venue for basic SLE research.


Assuntos
Linfócitos T CD4-Positivos/imunologia , Metilação de DNA/imunologia , Regulação da Expressão Gênica/imunologia , Lúpus Eritematoso Sistêmico/imunologia , MicroRNAs/imunologia , RNA Mensageiro/imunologia , Proteínas Adaptadoras de Transdução de Sinal/imunologia , Adulto , Proteínas Reguladoras de Apoptose , Linfócitos T CD4-Positivos/patologia , Feminino , Humanos , Lúpus Eritematoso Sistêmico/patologia , Masculino , Receptores Imunológicos/imunologia , Receptores de Lisoesfingolipídeo/imunologia , Receptores de Esfingosina-1-Fosfato
5.
ACS Omega ; 8(5): 4878-4888, 2023 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-36777584

RESUMO

In this study, a high-performance humidity sensor based on KCl-doped CuO/SnO2 p-n heterostructures was fabricated by a ball milling-roasting method. The morphology and nanostructure of the fabricated KCl-CuO/SnO2 composite were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and nitrogen sorption analysis. The results showed that the humidity sensor had a high sensitivity of 194 kΩ/%RH, short response and recovery times of 1.0 and 1.5 s, a low hysteresis value, and good repeatability. The energy band structure and complex impedance spectrum of the KCl-CuO/SnO2 composite indicated that the excellent humidity sensing performance originated from the ionic conductivity of KCl, the formation of heterojunctions, the change in the Schottky barrier height, and the depletion of electronic depletion layers. The KCl-CuO/SnO2 sensor has great potential in respiratory monitoring, noncontact sensing of finger moisture, and environmental monitoring.

6.
RSC Adv ; 13(9): 6264-6273, 2023 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-36825285

RESUMO

An ultra-high performance humidity sensor based on a CuO/Ti3C2T X MXene has been investigated in this work. The moisture-sensitive material was fabricated by a self-assembly method. The morphology and nanostructure of the fabricated CuO/Ti3C2T X composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectra. The humidity sensing abilities of the CuO/Ti3C2T X sensor in the relative humidity (RH) range from 0% to 97% were studied. The results showed that the humidity sensor had a high sensitivity of 451 kΩ/% RH, short response time (0.5 s) and recovery time (1 s), a low hysteresis value, and good repeatability. The CuO/Ti3C2T X sensor exhibited remarkable properties in human respiration rate monitoring, finger non-contact sensing, and environmental detection. The moisture-sensitive mechanism of CuO/Ti3C2T X was discussed. The fabricated CuO/Ti3C2T X showed great potential in the application of moisture-sensitive materials for ultra-high-performance humidity sensors.

7.
J Phys Condens Matter ; 34(36)2022 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-35760066

RESUMO

The structural development of novel carbon materials has always been a hot spot in theoretical and experimental research, due to carbon possess a wide range of applications in the fields of industry and electronic technology. In this work, ansp2+sp3hybrid carbon allotrope, named tower carbon, is proposed and studied based on density functional theory, including its structure, stability, electronic and mechanical properties. The crystal structure of tower carbon is like a Chinese classical architectural tower, so it is named tower carbon, which belongs to the cubic crystal system, and it is stable in thermodynamics, dynamics, and mechanics. The electronic band structure of tower carbon is calculated by Heyd-Scuseria-Ernzerhof hybrid functional. The results show that tower carbon is metallic material. In addition, the anisotropy factor of tower carbon and the directional dependence of Young's modulus, shear modulus, and Poisson's ratio are estimated. Compared with cF320, the tower carbon has less anisotropy.

8.
J Phys Condens Matter ; 33(38)2021 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-34229318

RESUMO

This work investigates the crystal structure, stability, mechanical properties, electronic properties, effective masses, and optical properties of Si-Ge alloys in theP-3m1 phase. The elastic constants and phonon spectra proven that the Si-Ge alloys in theP-3m1 phase have mechanical and dynamic stability. The bulk modulus, shear modulus and Young's modulus of Si-Ge alloys in theP-3m1 phase decrease with the increase of Ge composition, and the three-dimensional diagram of Young's modulus and effective mass show that the mechanical and transport properties have anisotropy. The Si12Ge12in thehP24 phase is a quasi-direct band gap semiconductor material with a band gap of 1.081 eV, while the Si30-xGexalloy (x= 6, 12, 18, 24) in thehP30 phase are all direct band gap semiconductor materials with the band gaps of 0.541 eV, 0.430 eV, 0.561 eV, and 0.387 eV, respectively. ThehP30-Si6Ge24has a very small effective electron mass. ThehP24-Si12Ge12show excellent absorptive capacity in the visible and infrared region region. Based on this work, Si-Ge alloys in theP-3m1 phase are promising materials for photovoltaic applications.

9.
Bioorg Med Chem ; 18(17): 6282-91, 2010 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-20691601

RESUMO

Photodynamic therapy (PDT) represents a promising method for treatment of cancerous tumors. The chemical and physical properties of used photosensitizer play key roles in the treatment efficacy. In this study, a novel photosensitizer, Chlorin-H [-13,15-N-(cyclohexyl)cycloimide] which displayed a characteristic long wavelength absorption peak at 698nm was synthesized. Following flash photolysis with 355nm laser, Chlorin-H is potent to react with O(2) and then produce (1)O(2). This finding indicates that Chlorin-H takes its effects through type II mechanism in PDT. Generally, Chlorin-H is localized in mitochondria and nucleus of cell. After light irradiation with 698nm laser, it can kill many types of cell, inhibit cell proliferation and colony formation, suppress cancer cell invasiveness and trigger apoptosis via the mitochondrial pathway in A549 cells in vitro. In addition, Chlorin-H-PDT can destroy A549 tumor in nude mice and a necrotic scab was formed eventually. The expression levels of many genes which regulated cell growth and apoptosis were determined by RT-PCR following Chlorin-H-PDT. The results showed that it either increased or decrease. Among which, the expression level of TNFSF13, a member of tumor necrosis factor superfamily, increased significantly. Silencing of TNFSF13 caused by RNA interference decreased the susceptibility of A549 cells to Chlorin-H-PDT. In general, Chlorin-H is an effective antitumor photosensitizer in vitro and in vivo and is worthy of further study as a new drug candidate. TNFSF13 will be an important molecular target for the discovery of new photosensitizers.


Assuntos
Fotoquimioterapia/métodos , Fármacos Fotossensibilizantes/química , Fármacos Fotossensibilizantes/farmacologia , Porfirinas/química , Porfirinas/farmacologia , Animais , Linhagem Celular Tumoral , Feminino , Humanos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Neoplasias Experimentais/tratamento farmacológico , Fármacos Fotossensibilizantes/síntese química , Porfirinas/síntese química , Reação em Cadeia da Polimerase Via Transcriptase Reversa
10.
Materials (Basel) ; 13(17)2020 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-32847088

RESUMO

In this work, the elastic anisotropy, mechanical stability, and electronic properties for P42/mnm XN (XN = BN, AlN, GaN, and InN) and Pbca XN are researched based on density functional theory. Here, the XN in the P42/mnm and Pbca phases have a mechanic stability and dynamic stability. Compared with the Pnma phase and Pm-3n phase, the P42/mnm and Pbca phases have greater values of bulk modulus and shear modulus. The ratio of the bulk modulus (B), shear modulus (G), and Poisson's ratio (v) of XN in the P42/mnm and Pbca phases are smaller than those for Pnma XN and Pm-3n XN, and larger than those for c-XN, indicating that Pnma XN and Pm-3n XN are more ductile than P42/mnm XN and Pbca XN, and that c-XN is more brittle than P42/mnm XN and Pbca XN. In addition, in the Pbca phases, XN can be considered a semiconductor material, while in the P42/mnm phase, GaN and InN have direct band-gap, and BN and AlN are indirect wide band gap materials. The novel III-V nitride polymorphs in the P42/mnm and Pbca phases may have great potential for application in visible light detectors, ultraviolet detectors, infrared detectors, and light-emitting diodes.

11.
Langmuir ; 25(22): 13238-43, 2009 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-19603767

RESUMO

The novel calcium carbonate (CaCO(3)) morphology, twin-sphere with an equatorial girdle, has been obtained under the control of poly(L-lysine) (PLys) through gas-diffusion method. The effect of the concentration of calcium cation and PLys, the reaction time, and the initial pH value are investigated, and various interesting morphologies, including twin-sphere, discus-like, hexagonal plate, and hallow structure are observed by using scanning electronic microscopy. Laser microscopic Raman spectroscopy studies indicated that all these CaCO(3) are vaterite. A possible mechanism is suggested to explain the formation of the twin-sphere based morphologies according to the results. It is proven that alkaline polypeptides can control the mineralization of CaCO(3) precisely as the reported acidic polypeptides and double hydrophilic block copolymers.


Assuntos
Carbonato de Cálcio/química , Nanoestruturas/química , Polilisina/química , Dicroísmo Circular , Concentração de Íons de Hidrogênio , Microscopia Eletrônica de Varredura , Modelos Químicos , Nanoestruturas/ultraestrutura , Análise Espectral Raman
12.
Bioresour Technol ; 291: 121819, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31369925

RESUMO

In this study, experiments on pretreating one species of microalgae (Chlorella pyrenoidosa) using one kind of ionic liquid (IL) of [BMIM]Cl were conducted. The aim of this work is to evaluate the recycling efficacy of expensive IL solvent for effective cell disruption. It was indicated that the molecular structure of IL was stable during the recycling test. Five times antisolvent precipitation of microalgae debris after lipid extraction using methanol recovered 99.8% IL with the energy consumption of 4.46 MJ per kg dry Chlorella pyrenoidosa. The chromatography was used to separate IL and hydrolysates, resulting in the IL loss below 1.97 g per kg dry Chlorella pyrenoidosa.


Assuntos
Chlorella/química , Imidazóis/química , Lipídeos/isolamento & purificação , Microalgas/química , Esgotos
14.
RSC Adv ; 8(15): 8248-8258, 2018 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-35542009

RESUMO

A novel resin system was prepared using the glycidyl amide type multifunctional epoxy resin N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane (TGDDM) and latent curing agent dicyandiamide (DICY). The curing reaction mechanism of the TGDDM/DICY system was studied by Fourier transform infrared (FTIR) spectrometry and the non-isothermal cure behaviors of the mixture were investigated with differential scanning calorimetry (DSC) measurements. The FTIR results demonstrated that there were two main reactions occurring in the curing process of the TGDDM/DICY system. The DSC thermogram of the blend exhibited two different cure regimes in the temperature range of 140-358 °C, and the system experienced two autocatalytic curing processes with α = 0.45 as the boundary; the corresponding average activation energies calculated by the Kissinger method were 69.7 and 88.7 kJ mol-1, respectively. In addition, the correlation between activation energy E a and fractional conversion α was determined by applying model-free isoconversional analysis with Flynn-Wall-Ozawa (FWO) and Starink methods. Results showed that both methods revealed similar trends and possessed approximately the same values at each fractional conversion. Activation energy varied greatly with fractional conversion and the possible causes behind the variations were analyzed in detail. The cured TGDDM/DICY exhibited outstanding mechanical and adhesive properties with tensile and shear strengths of 27.1 MPa at 25 °C and12.6 MPa at 200 °C, good dielectric properties with a low dielectric constant of 3.26 at 1000 kHz and a low water absorption of 0.41%.

15.
Materials (Basel) ; 11(5)2018 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-29695091

RESUMO

The structural, mechanical, elastic anisotropic, and electronic properties of hexagonal germanium carbonitride (h-GeCN) are systematically investigated using the first-principle calculations method with the ultrasoft pseudopotential scheme in the frame of generalized gradient approximation in the present work. The h-GeCN are mechanically and dynamically stable, as proved by the elastic constants and phonon spectra, respectively. The h-GeCN is brittle because the ratio B/G and Poisson’s ratio v of the h-GeCN are less than 1.75 and 0.26, respectively. For h-GeCN, from brittleness to ductility, the transformation pressures are 5.56 GPa and 5.63 GPa for B/G and Poisson’s ratio v, respectively. The h-GeCN exhibits the greater elastic anisotropy in Young’s modulus and the sound velocities. In addition, the calculated band structure of h-GeCN reveals that there is no band gap for h-GeCN with the HSE06 hybrid functional, so the h-GeCN is metallic.

16.
Polymers (Basel) ; 10(12)2018 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-30961240

RESUMO

High proton selectivity is the ultimate aim for the ion exchange membranes (IEMs). In this study, two kinds of sulfonated polyimides (SPI)-non-fluorinated and fluorine-containing polyimide-with about 40% sulfonation degree were synthesized by one-step high temperature polymerization. High proton selectivity IEMs were prepared and applied in vanadium flow batteries (VFB). The chemical structures, physicochemical properties and single cell performance of these membranes were characterized. The results indicate that high molecular weight of SPIs can guarantee the simultaneous achievement of good mechanical and oxidative stability for IEMs. Meanwhile, the proton selectivity of SPI membrane is five times higher than that of Nafion115 membranes due to the introduction of fluorocarbon groups. Consequently, the single cell assembled with SPI membranes exhibits excellent energy efficiency up to 84.8% at a current density of 100 mA·cm-2, which is 4.6% higher than Nafion115. In addition, the capacity retention is great after 500 charge⁻discharge cycles. All results demonstrate that fluorinated SPI ion exchange membrane has a bright prospect in new energy field.

17.
Materials (Basel) ; 10(6)2017 May 31.
Artigo em Inglês | MEDLINE | ID: mdl-28772964

RESUMO

The structural, mechanical, anisotropic, electronic and thermal properties of Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase are investigated in this work. The calculations have been performed with an ultra-soft pseudopotential by using the generalized gradient approximation and local density approximation in the framework of density functional theory. The achieved results for the lattice constants and band gaps of P42/ncm-Si and P42/ncm-Ge in this research have good accordance with other results. The calculated elastic constants and elastic moduli of the Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase are better than that of the Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/mnm phase. The Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase exhibit varying degrees of mechanical anisotropic properties in Poisson's ratio, shear modulus, Young's modulus, and universal anisotropic index. The band structures of the Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase show that they are all indirect band gap semiconductors with band gap of 1.46 eV, 1.25 eV, 1.36 eV and 1.00 eV, respectively. In addition, we also found that the minimum thermal conductivity κmin of the Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase exhibit different degrees of anisotropic properties in (001), (010), (100) and (01¯0) planes.

18.
Materials (Basel) ; 10(8)2017 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-28786960

RESUMO

The structural, mechanical, elastic anisotropic, and electronic properties of Pbca-XN (X = C, Si, Ge) are investigated in this work using the Perdew-Burke-Ernzerhof (PBE) functional, Perdew-Burke-Ernzerhof for solids (PBEsol) functional, and Ceperly and Alder, parameterized by Perdew and Zunger (CA-PZ) functional in the framework of density functional theory. The achieved results for the lattice parameters and band gap of Pbca-CN with the PBE functional in this research are in good accordance with other theoretical results. The band structures of Pbca-XN (X = C, Si, Ge) show that Pbca-SiN and Pbca-GeN are both direct band gap semiconductor materials with a band gap of 3.39 eV and 2.22 eV, respectively. Pbca-XN (X = C, Si, Ge) exhibits varying degrees of mechanical anisotropic properties with respect to the Poisson's ratio, bulk modulus, shear modulus, Young's modulus, and universal anisotropic index. The (001) plane and (010) plane of Pbca-CN/SiN/GeN both exhibit greater elastic anisotropy in the bulk modulus and Young's modulus than the (100) plane.

19.
Nanomaterials (Basel) ; 7(1)2016 Dec 28.
Artigo em Inglês | MEDLINE | ID: mdl-28336837

RESUMO

Structural, mechanical, electronic properties, and stability of boron nitride (BN) in Pnma structure were studied using first-principles calculations by Cambridge Serial Total Energy Package (CASTEP) plane-wave code, and the calculations were performed with the local density approximation and generalized gradient approximation in the form of Perdew-Burke-Ernzerhof. This BN, called Pnma-BN, contains four boron atoms and four nitrogen atoms buckled through sp³-hybridized bonds in an orthorhombic symmetry unit cell with Space group of Pnma. Pnma-BN is energetically stable, mechanically stable, and dynamically stable at ambient pressure and high pressure. The calculated Pugh ratio and Poisson's ratio revealed that Pnma-BN is brittle, and Pnma-BN is found to turn brittle to ductile (~94 GPa) in this pressure range. It shows a higher mechanical anisotropy in Poisson's ratio, shear modulus, Young's modulus, and the universal elastic anisotropy index AU. Band structure calculations indicate that Pnma-BN is an insulator with indirect band gap of 7.18 eV. The most extraordinary thing is that the band gap increases first and then decreases with the increase of pressure from 0 to 60 GPa, and from 60 to 100 GPa, the band gap increases first and then decreases again.

20.
Bioresour Technol ; 101(24): 9570-6, 2010 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-20696572

RESUMO

Mixed oxides of TiO(2)-MgO obtained by the sol-gel method were used to convert waste cooking oil into biodiesel. Titanium improved the stability of the catalyst because of the defects induced by the substitution of Ti ions for Mg ions in the magnesia lattice. The best catalyst was determined to be MT-1-923, which is comprised of an Mg/Ti molar ratio of 1 and calcined at 923 K, based on an assessment of the activity and stability of the catalyst. The main reaction parameters, including methanol/oil molar ratio, catalyst amount, and temperature, were investigated. The catalytic activity of MT-1-923 decreased slowly in the reuse process. After regeneration, the activity of MT-1-923 slightly increased compared with that of the fresh catalyst due to an increase in the specific surface area and average pore diameter. The mixed oxides catalyst, TiO(2)-MgO, showed good potential in large-scale biodiesel production from waste cooking oil.


Assuntos
Biocombustíveis/análise , Culinária , Óxido de Magnésio/química , Óleos/análise , Titânio/química , Resíduos/análise , Catálise , Ésteres/análise , Magnésio/análise , Espectrofotometria Ultravioleta , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Termogravimetria , Titânio/análise , Água/química , Difração de Raios X
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA