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1.
Mater Sci Eng C Mater Biol Appl ; 106: 110221, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31753358

RESUMO

The inflammatory response is the first and inevitable event after implant surgery in vivo, in which the macrophages M1 polarization is mediated. Numerous publications indicate that the physical properties of implant surface nanostructure can influence macrophages M1 polarization status, whereas the regulation mechanisms have not been elucidated yet. Unlike the conventional biochemical factors that can directly bind to the cellular surface receptors or be transported into cytoplasm, the physical information of implant surface nanostructure can only be sensed by direct contact with cells. Therefore, we infer that the implant surface nanostructure may have unique regulation mechanisms. In this study, we compared the influences of the titanium implant surface coated with titania nanotubes on the surface (∼100 nm diameter, NT-100) and the standard IFN-γ/LPS stimulation on the macrophages M1 polarization. Both the NT-100 surface and IFN-γ/LPS stimulation could induce macrophages M1 polarization, indicated by significant upregulation of M1-specific molecules including CD86, iNOS, CCR7 and IL-1ß, without affecting the M2-specific molecules including CD206, Arg1 and IL-10. However, we found that the IFN-γ/LPS induced macrophages M1 polarization was mediated by RBP-J-IRF8 pathway, whereas the NT-100 surface was more related to FAK-MAPKs pathway, particularly the JNK and ERK1/2 signaling. Our study demonstrated that the implant surface nanostructure has great potential to trigger the host inflammatory response through distinct pathways from conventional biochemical factors, which may remind us to re-consider the unique regulation mechanisms of nano surface on cell functions. Our finding offers a theoretical basis for titanium implant modification to benefit tissue integration.

2.
Water Environ Res ; 2019 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-31650659

RESUMO

A p-type TiO2 with Ti vacancies (D-TiO2 ) was synthesized by a facile solvothermal treatment, and Ag/TiO2 with different Ag loading amount was prepared through a photo-reduction deposition method. The samples were characterized through scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The adsorption and photocatalytic characteristics of tetrabromobisphenol A (TBBPA) on D-TiO2 and Ag/TiO2 were investigated. The adsorption of TBBPA on Ag/TiO2 was significantly enhanced and was five times greater than that of pure TiO2 . The increase in pH significantly inhibited the adsorption of TBBPA. The 2%-Ag/TiO2 nearly completely degraded TBBPA in 10 min under UV-Vis light (λ > 360 nm), and the apparent reaction rate constant (kapp ) reached 0.63 min-1 . The significantly enhanced UV-Vis light catalytic properties of the Ag/TiO2 in comparison with that of TiO2 were attributed to the increased adsorption capacity and electron transfer ability of the Ag/TiO2 . Free radical trap experiments results showed that holes and superoxide radicals play a major role in the catalytic degradation of TBBPA by Ag/TiO2 . Moreover, the Ag/TiO2 catalyst exhibits high stability during TBBPA degradation even after three cycles. PRACTITIONER POINTS: Ti-defected TiO2 and Ag/TiO2 were synthesized using a solvothermal and photo-reduction deposition, respectively. Ag/TiO2 exhibited outstanding adsorption and photocatalytic activity for TBBPA removal under UV-Vis light. Holes and superoxide radicals play a major role in the photocatalytic degradation of TBBPA.

3.
R Soc Open Sci ; 6(7): 190351, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31417737

RESUMO

In this study, natural manganese oxides (MnO x ), an environmental material with high redox potential, were used as a promising low-cost oxidant to degrade the widely used dyestuff methylene blue (MB) in aqueous solution. Although the surface area of MnO x was only 7.17 m2 g-1, it performed well in the degradation of MB with a removal percentage of 85.6% at pH 4. It was found that MB was chemically degraded in a low-pH reaction system and the degradation efficiency correlated negatively with the pH value (4-8) and initial concentration of MB (10-50 mg l-1), but positively with the dosage of MnO x (1-5 g l-1). The degradation of MB fitted well with the second-order kinetics. Mathematical models were also built for the correlation of the kinetic constants with the pH value, the initial concentration of MB and the dosage of MnO x . Furthermore, several transformation products of MB were identified with HPLC-MS, which was linked with the bond energy theory to reveal that the degradation was initiated with demethylation.

4.
Environ Pollut ; 251: 746-755, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31121539

RESUMO

Gabapentin (GPT) has become an emerging contaminant in aquatic environments due to its wide application in medical treatment all over the world. In this study, embryos of zebrafish were exposed to gabapentin at realistically environmental concentrations, 0.1 µg/L and 10 µg/L, so as to evaluate the ecotoxicity of this emergent contaminant. The transcriptomics profiling of deep sequencing was employed to illustrate the mechanisms. The zebrafish (Danio rerio) embryo were exposed to GPT from 12 hpf to 96 hpf resulting in 136 and 750 genes differentially expressed, respectively. The results of gene ontology (GO) analysis and the Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis illustrated that a large amount of differentially expressed genes (DEGs) were involved in the antioxidant system, the immune system and the nervous system. RT-qPCR was applied to validate the results of RNA-seq, which provided direct evidence that the selected genes involved in those systems mentioned above were all down-regulated. Acetylcholinesterase (AChE), lysozyme (LZM) and the content of C-reactive protein (CRP) were decreased at the end of exposure, which is consistent with the transcriptomics results. The overall results of this study demonstrate that GPT simultaneously affects various vital functionalities of zebrafish at early developmental stage, even at environmentally relevant concentrations.


Assuntos
Embrião não Mamífero/embriologia , Gabapentina/toxicidade , Sistema Imunitário/embriologia , Sistema Nervoso/embriologia , Poluentes Químicos da Água/toxicidade , Peixe-Zebra/embriologia , Acetilcolinesterase/biossíntese , Animais , Proteína C-Reativa/biossíntese , Regulação para Baixo , Perfilação da Expressão Gênica , Sequenciamento de Nucleotídeos em Larga Escala , Muramidase/biossíntese
5.
Chemosphere ; 226: 103-109, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30921638

RESUMO

Sulfamethazine (SMZ), a kind of sulfonamide antibiotics, can exist for a long periods of time and has been widely detected in the environment, which could pose a potential health threat to human beings. In this study, sludge-derived carbon (SC) catalyst was modified and applied to degrade SMZ during catalytic oxidation process. Degradation products and possible transformation pathways were investigated based on data of GC-MS. The toxicity evolution of SMZ degradation after catalytic oxidation process was tested with zebrafish and microbial degradation respirometer. As a consequence, SC modified with nitric acid (SCHNO3) exhibited highly catalytic efficiency reached 92.2% SMZ conversion and 75.2% total organic carbon (TOC) removal rate after 480 min. Ten kinds of possible products were identified by GC-MS during degradation process of SMZ, indicating two possible pathways. No pronounced malformation was observed in the toxicity experiments with zebrafish until 120 h post fertilization (hpf). However, further analysis showed that zebrafish incubated with SMZ solution had higher mortality, lower hatching rate, slower spontaneous movement and shorter body length, compared with the group used normal nutrient solution, while the water after treatment had lower toxicity effects on zebrafish. The toxicity experiments with microbial degradation respirometer showed that SMZ solution had lower value of oxygen uptake, which indicated that SMZ solution had higher values of toxicity and inhibition of pharmaceutical compounds. This study provides a catalyst with low cost and high catalytic efficiency for degradation process of SMZ and gives a deeper insight into the ecotoxicity of treated water.


Assuntos
Sulfametazina/química , Purificação da Água/métodos , Animais , Antibacterianos/química , Anti-Infecciosos/química , Catálise , Ecotoxicologia , Cromatografia Gasosa-Espectrometria de Massas , Humanos , Oxirredução , Esgotos/química , Sulfametazina/toxicidade , Peixe-Zebra/metabolismo
6.
Sci Total Environ ; 654: 942-947, 2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30453264

RESUMO

In this study, heterogeneous Fenton-like degradation of ofloxacin (OFX) was investigated by sludge derived carbon (SC). The effects of SC catalyst, temperature and pH on the efficiency of ofloxacin degradation were investigated. SC treated with sulfuric acid (SC-H2SO4) performed high catalytic activity, indicating that sulfate group produced low pH of the surface and was beneficial for heterogeneous Fenton-like degradation. The removal of ofloxacin and TOC was 91.5% and 62.3%, respectively, after 180 min adsorption and 540 min oxidation, at pH 6 and a dosage of 138 mg L-1 H2O2. It was found that OFX conversion increased with the decrease of pH and OFX was degraded under the wide range of pH (3-6) by SC-H2SO4. These promising results clearly demonstrate the potential of the heterogeneous Fenton-like process for the effective degradation of ofloxacin by SC-H2SO4. Based on intermediated products identified by gas chromatography-mass spectrometry, a possible OFX oxidation pathway in Fenton-like reaction was proposed.


Assuntos
Antibacterianos/análise , Carbono/química , Ofloxacino/análise , Fotólise , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Adsorção , Peróxido de Hidrogênio/química , Oxirredução , Esgotos/química
7.
Environ Technol ; : 1-8, 2018 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-30139300

RESUMO

Sulfamethoxazole (SMX) is a commonly used antibiotic for both human and animals. The frequent detection of SMX in natural water bodies and sediment has become an issue of great environmental concern due to its potential risk to induce antibiotic resistance in pathogenic bacteria. In the present work, the catalytic wet peroxide oxidation (CWPO) was investigated to remove SMX with sludge-derived carbon (SC) as a cheap alternative catalyst. Different acids were used to modify SC. It was found that SC modified with sulphuric acid (SC-H2SO4) demonstrated the best catalytic activity. The removal efficiency of SMX and TOC was 97.7% and 65.7%, respectively, after 260 min, at pH 5 with a dosage of 220 mg/L H2O2. The effects of temperature, initial pH and H2O2 dosage were also investigated. The study demonstrated that the increase of temperature could significantly improve the degradation of SMX from 10.0% at 20°C to 94.7% at 60°C.

8.
Nucleic Acids Res ; 46(14): 7418-7424, 2018 08 21.
Artigo em Inglês | MEDLINE | ID: mdl-29982790

RESUMO

DNA supercoiling is an important regulator of gene activity. The transmission of transcription-generated supercoiling wave along a DNA helix provides a way for a gene being transcribed to communicate with and regulate its neighboring genes. Currently, the dynamic behavior of supercoiling transmission remains unclear owing to the lack of a suitable tool for detecting the dynamics of supercoiling transmission. In this work, we established a torsion sensor that quantitatively monitors supercoiling transmission in real time in DNA. Using this sensor, we studied the transmission of transcriptionally generated negative supercoiling in linear and multi-way DNA duplexes. We found that transcription-generated dynamic supercoiling not only transmits along linear DNA duplex but also equally diverges at and proceeds through multi-way DNA junctions. We also show that such a process is regulated by DNA-protein interactions and non-canonical DNA structures in the path of supercoiling transmission. These results imply a transcription-coupled mechanism of dynamic supercoiling-mediated intra- and inter-chromosomal signal transduction pathway and their regulation in DNA.


Assuntos
DNA Super-Helicoidal/química , DNA/química , Quadruplex G , Transcrição Genética , Sequência de Bases , Técnicas Biossensoriais , DNA/genética , DNA/metabolismo , DNA Super-Helicoidal/genética , DNA Super-Helicoidal/metabolismo , Cinética , Modelos Genéticos , Regiões Promotoras Genéticas/genética , Ligação Proteica , Espectrometria de Fluorescência/métodos
9.
Environ Sci Pollut Res Int ; 25(25): 25496-25503, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29956258

RESUMO

Sludge-derived carbons (SCs) were modified by different acids and used as electrocatalyst for electrochemical oxidation degradation of acetophenone. The results showed that SC treated with phosphoric acid (H3PO4-SC) exhibited the highest catalytic activity. The degradation efficiency of acetophenone reached 87.0%, and TOC removal was 72.3% under the conditions of 100 mg L-1 acetophenone, 90 mA cm-2, and 180 min reaction time. The element content and chemical state of H3PO4-SC were measured by XRF, XRD, TGA, FTIR, and Mössbauer spectra, and the results indicated that ferric iron and phosphate on the surface of H3PO4-SC might play the main role in acetophenone degradation. The carbonyl-13C-labeled acetophenone was first used to investigate the degradation of acetophenone in electrochemical oxidation by NMR.


Assuntos
Acetofenonas/química , Carbono/química , Ácidos Fosfóricos , Esgotos/química , Purificação da Água/métodos , Catálise , Ferro , Oxirredução , Fosfatos , Poluição da Água
10.
ACS Chem Biol ; 12(10): 2609-2618, 2017 10 20.
Artigo em Inglês | MEDLINE | ID: mdl-28846373

RESUMO

Transcription induces formation of intramolecular G-quadruplex structures at the upstream region of a DNA duplex by an upward transmission of negative supercoiling through the DNA. Currently the regulation of such G-quadruplex formation remains unclear. Using plasmid as a model, we demonstrate that while it is the dynamic negative supercoiling generated by a moving RNA polymerase that triggers a formation of a G-quadruplex, the constitutional superhelicity determines the potential and range of the formation of a G-quadruplex by constraining the propagation of the negative supercoiling. G-quadruplex formation is maximal in negatively supercoiled and nearly abolished in relaxed plasmids while being moderate in nicked and linear ones. The formation of a G-quadruplex strongly correlates with the presence of an R-loop. Preventing R-loop formation virtually abolished G-quadruplex formation even in the negatively supercoiled plasmid. Enzymatic action and protein binding that manipulate supercoiling or its propagation all impact the formation of G-quadruplexes. Because chromosomes and plasmids in cells in their natural form are maintained in a supercoiled state, our findings reveal a physical basis that justifies the formation and regulation of G-quadruplexes in vivo. The structural features involved in G-quadruplex formation may all serve as potential targets in clinical and therapeutic applications.


Assuntos
DNA/química , Quadruplex G , Transcrição Genética , DNA/genética , RNA Polimerases Dirigidas por DNA , Escherichia coli , Desnaturação de Ácido Nucleico , Plasmídeos , Proteínas Virais
11.
Chem Sci ; 7(7): 4573-4581, 2016 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-30155104

RESUMO

G-quadruplexes are implicated in many essential cellular processes and sequences with potential to form a G-quadruplex are widely present in DNA and RNA. However, it is difficult to know whether a sequence of interest naturally forms a G-quadruplex in living cells. Here we report the detection of a G-quadruplex in defined RNA sequences in living cells in a natural intracellular environment. A G-quadruplex forming sequence in a RNA transcript is tagged at proximity with an aptamer. The two structures are recognized respectively by two probe proteins each of which is fused with a split half of enhanced green fluorescent protein (eGFP). Simultaneous binding of the two proteins to RNA brings the two halves of eGFP into proximity, permitting them to reconstitute into a functional eGFP that emits fluorescence to signal the formation of a G-quadruplex in RNA. We show that a G-quadruplex can form in RNA and can be detected with sequence and structure specificity under both in vitro and in vivo conditions. The results, therefore, provide direct evidence for the formation of RNA G-quadruplexes in live cells and the method provides a useful tool to validate G-quadruplex formation in a specific sequence under a natural cellular condition.

12.
J Proteomics ; 136: 68-76, 2016 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-26710723

RESUMO

UNLABELLED: In a proof of concept study, metal-coded affinity tags based on click chemistry (MeCAT-Click) were used to analyze the proteome of Escherichia coli (E. coli) in response to heat stress. This allows high labeling efficiency, high detection sensitivity, and multiplex capabilities, which are pivotal for its application to protein quantification. Two approaches are presented for relative quantification of differentially lanthanide-labeled proteins. The first approach uses isotope-labeling, where ESI-MS was utilized to quantify the differentially labeled proteins from different states of E. coli. With this approach, 14 proteins were found with changed abundance, among them five proteins upregulated. In the second approach, differentially labeled samples were separated by two dimensional gel electrophoresis (2-DE) and scanned by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Comparison of the signal intensities of the different lanthanides was used to quantify different sample states. Based on this information, ESI-MS was used to identify the proteins with different abundance. The sensitivity of LA-ICP-MS allowed us to find one upregulated protein that was nearly invisible by silver staining ("Probable replication endonuclease from retron EC67"). The advantage of this approach is to locate low abundant proteins with differential expression using LA-ICP-MS, which may be overlooked otherwise. BIOLOGICAL SIGNIFICANCE: This paper demonstrates the successful application of a novel metal labeling strategy to quantify the proteins from complex biological samples. In comparison with former metal labeling strategies, it reduces the steric hindrance and improves the labeling efficiency during the labeling process, which ensure its successful application. This methodology is compatible with both molecular and elemental mass spectrometry. ESI-MS/MS in combination with software-based search allows the identification and relative quantification of labeled proteins. In addition, LA-ICP-MS helps to locate the labeled proteins in 2-DE gels with superior detection capability, thus, target proteins with low abundance can be precisely followed. Its excellent sensitivity allows one to track the proteins of interest that are barely visible by silver staining.


Assuntos
Química Click/métodos , Proteínas de Escherichia coli , Escherichia coli , Resposta ao Choque Térmico , Elementos da Série dos Lantanídeos/química , Proteoma , Escherichia coli/química , Escherichia coli/metabolismo , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/metabolismo , Proteoma/química , Proteoma/metabolismo
13.
Proc Natl Acad Sci U S A ; 112(47): 14581-6, 2015 Nov 24.
Artigo em Inglês | MEDLINE | ID: mdl-26553979

RESUMO

G-quadruplex structures formed by guanine-rich nucleic acids are implicated in essential physiological and pathological processes and nanodevices. G-quadruplexes are normally composed of four Gn (n ≥ 3) tracts assembled into a core of multiple stacked G-quartet layers. By dimethyl sulfate footprinting, circular dichroism spectroscopy, thermal melting, and photo-cross-linking, here we describe a unique type of intramolecular G-quadruplex that forms with one G2 and three G3 tracts and bears a guanine vacancy (G-vacancy) in one of the G-quartet layers. The G-vacancy can be filled up by a guanine base from GTP or GMP to complete an intact G-quartet by Hoogsteen hydrogen bonding, resulting in significant G-quadruplex stabilization that can effectively alter DNA replication in vitro at physiological concentration of GTP and Mg(2+). A bioinformatic survey shows motifs of such G-quadruplexes are evolutionally selected in genes with unique distribution pattern in both eukaryotic and prokaryotic organisms, implying such G-vacancy-bearing G-quadruplexes are present and play a role in gene regulation. Because guanine derivatives are natural metabolites in cells, the formation of such G-quadruplexes and guanine fill-in (G-fill-in) may grant an environment-responsive regulation in cellular processes. Our findings thus not only expand the sequence definition of G-quadruplex formation, but more importantly, reveal a structural and functional property not seen in the standard canonical G-quadruplexes.


Assuntos
Quadruplex G , Guanina/análogos & derivados , Guanina/química , Dicroísmo Circular , DNA/química , Replicação do DNA
14.
Talanta ; 134: 468-475, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25618695

RESUMO

In this work, we present a two-step labeling approach for the efficient tagging with lanthanide-containing complexes. For this purpose, derivatization of the cysteine residues with an alkyne group acting as linker was done before the DOTA complex was introduced using in situ click chemistry. The characterization of this new methodology is presented including the optimization of the labeling process, demonstration of the quantitative capabilities using both electrospray ionization mass spectrometry (ESI-MS) and inductively coupled plasma mass spectrometry (ICP-MS) detection, and study of the fragmentation behavior of the labeled peptides by collision-induced dissociation (CID) for identification purposes. The results show that, in terms of labeling efficiency, this new methodology improves previously developed DOTA-based label strategies, such as MeCAT-maleimide (metal-coded affinity tag, MeCAT-Mal) and MeCAT-iodoacetamide (MeCAT-IA) reagents. The goal of reducing the steric hindrance caused by the voluminous DOTA complex was fulfilled allowing both, quantification and identification of labeled biopolymers.


Assuntos
Azidas/química , Biopolímeros/química , Compostos Heterocíclicos com 1 Anel/química , Elementos da Série dos Lantanídeos/química , Coloração e Rotulagem/métodos , Alquinos/química , Química Click , Peptídeos/química , Soroalbumina Bovina/química , Tripsina/química
15.
Nucleic Acids Res ; 42(16): 10832-44, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25140009

RESUMO

Human mitochondrial DNA contains a distinctive guanine-rich motif denoted conserved sequence block II (CSB II) that stops RNA transcription, producing prematurely terminated transcripts to prime mitochondrial DNA replication. Recently, we reported a general phenomenon that DNA:RNA hybrid G-quadruplexes (HQs) readily form during transcription when the non-template DNA strand is guanine-rich and such HQs in turn regulate transcription. In this work, we show that transcription of mitochondrial DNA leads to the formation of a stable HQ or alternatively an unstable intramolecular DNA G-quadruplex (DQ) at the CSB II. The HQ is the dominant species and contributes to the majority of the premature transcription termination. Manipulating the stability of the DQ has little effect on the termination even in the absence of HQ; however, abolishing the formation of HQs by preventing the participation of either DNA or RNA abolishes the vast majority of the termination. These results demonstrate that the type of G-quadruplexes (HQ or DQ) is a crucial determinant in directing the transcription termination at the CSB II and suggest a potential functionality of the co-transcriptionally formed HQ in DNA replication initiation. They also suggest that the competition/conversion between an HQ and a DQ may regulate the function of a G-quadruplex-forming sequence.


Assuntos
DNA Mitocondrial/química , Quadruplex G , Regiões Terminadoras Genéticas , Terminação da Transcrição Genética , Sequência de Bases , Sequência Conservada , Replicação do DNA , DNA Mitocondrial/biossíntese , Humanos , Mutação , Oligonucleotídeos/química , Plasmídeos/genética , RNA/química , RNA Mitocondrial
16.
Int J Nanomedicine ; 7: 2631-40, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22679373

RESUMO

Quantum dots (QDs) have many potential clinical and biological applications because of their advantages over traditional fluorescent dyes. However, the genotoxicity potential of QDs still remains unclear. In this paper, a plasmid-based system was designed to explore the genotoxic mechanism of QDs by detecting changes in DNA configuration and biological activities. The direct chemicobiological interactions between DNA and mercaptoacetic acid-coated CdSecore QDs (MAA-QDs) were investigated. After incubation with different concentrations of MAA-QDs (0.043, 0.13, 0.4, 1.2, and 3.6 µmol/L) in the dark, the DNA conversion of the covalently closed circular (CCC) DNA to the open circular (OC) DNA was significantly enhanced (from 13.9% ± 2.2% to 59.9% ± 12.8%) while the residual transformation activity of plasmid DNA was greatly decreased (from 80.7% ± 12.8% to 13.6% ± 0.8%), which indicated that the damages to the DNA structure and biological activities induced by MAA-QDs were concentration-dependent. The electrospray ionization mass spectrometry data suggested that the observed genotoxicity might be correlated with the cadmium-mercaptoacetic acid complex (Cd-MAA) that is formed in the solution of MAA-QDs. Circular dichroism spectroscopy and transformation assay results indicated that the Cd-MAA complex might interact with DNA through the groove-binding mode and prefer binding to DNA fragments with high adenine and thymine content. Furthermore, the plasmid transformation assay could be used as an effective method to evaluate the genotoxicities of nanoparticles.


Assuntos
Compostos de Cádmio/toxicidade , Cádmio/toxicidade , DNA Circular/efeitos dos fármacos , Mutagênicos/toxicidade , Pontos Quânticos , Compostos de Selênio/toxicidade , Tioglicolatos/toxicidade , Animais , Composição de Bases , Bovinos , Dicroísmo Circular , DNA Circular/química , Escherichia coli/genética , Testes de Mutagenicidade , Conformação de Ácido Nucleico/efeitos dos fármacos , Espectrometria de Fluorescência , Espectrometria de Massas por Ionização por Electrospray , Transformação Bacteriana/efeitos dos fármacos
17.
Environ Sci Technol ; 45(10): 4415-21, 2011 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-21488606

RESUMO

A cake collapse model was developed by taking the combined effects of fractal dimension, relaxation ratio, coordination number, and aggregate diameter into consideration. The cake porosity including intraaggregate and interaggregate porosities was modeled successively by three typical coordination numbers (n = 6, 8, and 12). Accordingly, an inversion method made it possible to deduce the coordination number using the measured cake porosities, and the reverse-calculated value with minimum error and the corresponding relaxation ratios were applied as the parameters for the model. As a result, the profiles of intraaggregate and interaggregate porosities and cake porosity were respectively predicted in contrast to the integrated variation of the relaxation ratio and the fractal dimension. Furthermore, a comparison between the model predictions of the cake pressure drop gradients with and without aggregate compression was conducted to validate the presence of cake collapse. The results show that the predictions based on the proposed collapse model are in agreement with the experiments, and the coordination number is one of the key factors that must be incorporated into the cake collapse models.


Assuntos
Cerâmica/química , Filtração/métodos , Fractais , Filtração/instrumentação , Floculação , Modelos Químicos , Modelos Teóricos , Tamanho da Partícula , Permeabilidade , Porosidade , Pressão
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