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1.
Sci Technol Adv Mater ; 25(1): 2313957, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38444591

RESUMO

The fillers inside a polymer matrix should typically be self-assembled in both the horizontal and vertical directions to obtain 3-dimentional (3D) percolation pathways, whereby the fields of application can be expanded and the properties of organic-inorganic composite films improved. Conventional dielectrophoresis techniques can typically only drive fillers to self-assemble in only one direction. We have devised a one-step dielectrophoresis-driven approach that effectively induces fillers self-assembly along two orthogonal axes, which results in the formation of 3D interconnected T-shaped iron microstructures (3D-T CIP) inside a polymer matrix. This approach to carbonyl iron powder (CIP) embedded in a polymer matrix results in a linear structure along the thickness direction and a network structure on the top surface of the film. The fillers in the polymer were controlled to achieve orthogonal bidirectional self-assembly using an external alternating current (AC) electric field and a non-contact technique that did not lead to electrical breakdown. The process of 3D-T CIP formation was observed in real time using in situ observation methods with optical microscopy, and the quantity and quality of self-assembly were characterized using statistical and fractal analysis. The process of fillers self-assembly along the direction perpendicular to the electric field was explained by finite element analogue simulations, and the results indicated that the insulating polyethylene terephthalate (PET) film between the electrode and the CIP/prepolymer suspension was the key to the formation of the 3D-T CIP. In contrast to the traditional two-step method of fabricating sandwich-structured film, the fabricated 3D-T CIP film with 3D electrically conductive pathways can be applied as magnetic field sensor.


A one-step electric field-induced self-assembly method was developed to efficiently control the self-assembly of fillers along two orthogonal axes to form three-dimensional interconnected T-shaped microstructure assembles of carbonyl iron powder inside a polymer matrix.

2.
Sci Technol Adv Mater ; 24(1): 2260301, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37854120

RESUMO

This study introduces an approach to overcome the limitations of conventional pressure sensors by developing a thin and lightweight composite film specifically tailored for flexible capacitive pressure sensors, with a particular emphasis on the medium and high pressure range. To accomplish this, we have engineered a composite film by combining polyvinylidene fluoride (PVDF) and graphite nanoplatelets (GNP) derived from expanded graphite (Ex-G). A uniform sized GNPs with an average lateral size of 2.55av and an average thickness of 33.74 av with narrow size distribution was obtained with a gas-induced expansion of expandable graphite (EXP-G) combined with tip sonication in solvent. By this precisely controlled GNP within the composite film, a remarkable improvement in sensor sensitivity has been achieved, surpassing 4.18 MPa-1 within the pressure range of 0.1 to 1.6 MPa. This enhancement can be attributed to the generation of electric charge from the movement of GNP in the polymer matrix. Additionally, stability testing has demonstrated the reliable operation of the composite film over 1000 cycles. Notably, the composite film exhibits exceptional continuous pressure sensing capabilities with a rapid response time of approximately 100 milliseconds. Experimental validation using a 3 × 3 sensor array has confirmed the accurate detection of specific contact points, thus highlighting the potential of the composite film in selective pressure sensing. These findings signify an advancement in the field of flexible capacitive pressure sensors that offer enhanced sensitivity, consistent operation, rapid response time, and the unique ability to selectively sense pressure.

3.
Microb Drug Resist ; 29(10): 448-455, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37379479

RESUMO

Recent studies have revealed that colistin dependence frequently develops in colistin-susceptible Acinetobacter baumannii isolates. Despite resistance in parental strains, colistin-dependent mutants showed increased susceptibility to several antibiotics, which suggests the possibility of developing strategies to eliminate multidrug-resistant (MDR) A. baumannii. We investigated in vitro and in vivo efficacy of combinations of colistin and other antibiotics using MDR A. baumannii strains H08-391, H06-855, and H09-94, which are colistin-susceptible but develops colistin dependence upon exposure to colistin. An in vitro time-killing assay, a checkerboard assay, and an antibiotic treatment assay using Galleria mellonella larvae were performed. Although a single treatment of colistin at a high concentration did not prevent colistin dependence, combinations of colistin with other antibiotics at subinhibitory concentrations, especially amikacin, eradicated the strains by inhibiting the development of colistin dependence, in the in vitro time-killing assay. Only 40% of G. mellonella larvae infected by A. baumannii survived with colistin treatment alone; however, all or most of them survived following treatment with the combination of colistin and other antibiotics (amikacin, ceftriaxone, and tetracycline). Our results suggest the possibility of the combination of colistin and amikacin or other antibiotics as one of therapeutic options against A. baumannii infections by eliminating colistin-dependent mutants.

4.
J Microbiol ; 61(3): 359-367, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36951963

RESUMO

Bacterial cells are covered with various glycopolymers such as peptidoglycan (PG), lipopolysaccharides (LPS), teichoic acids, and capsules. Among these glycopolymers, PG assembly is the target of some of our most effective antibiotics, consistent with its essentiality and uniqueness to bacterial cells. Biosynthesis of other surface glycopolymers have also been acknowledged as potential targets for developing therapies to control bacterial infections, because of their importance for bacterial survival in the host environment. Moreover, biosynthesis of most surface glycopolymers are closely related to PG assembly because the same lipid carrier is shared for glycopolymer syntheses. In this review, I provide an overview of PG assembly and antibiotics that target this pathway. Then, I discuss the implications of a common lipid carrier being used for assembly of PG and other surface glycopolymers in antibiotic development.


Assuntos
Antibacterianos , Peptidoglicano , Antibacterianos/farmacologia , Antibacterianos/metabolismo , Peptidoglicano/metabolismo , Ácidos Teicoicos/metabolismo , Lipopolissacarídeos/metabolismo , Parede Celular/metabolismo
5.
Microbiol Spectr ; 10(6): e0265522, 2022 12 21.
Artigo em Inglês | MEDLINE | ID: mdl-36416541

RESUMO

Many mechanisms have been proposed to be involved in the formation of bacterial persister cells. In this study, we investigated the impact of dam encoding DNA methylation on persister cell formation in Acinetobacter. We constructed plasmids overexpressing dam encoding DNA-(adenine N6)-methyltransferase and four genes as possibly involved in persistence and introduced them into three A. baumannii strains. For persister cell formation assays, bacteria were exposed to ciprofloxacin, imipenem, cefotaxime, and rifampin, and the transcription levels of the genes were measured by qRT-PCR. In addition, growth curves of strains were determined. We found that all five genes were upregulated following antibiotic exposure. Dam overexpression increased persister cell formation rates and activated the four persister cell-involved genes. Among the four persister cell-involved genes, only RecC overexpression increase persister cell formation rates. While recC-overexpressing strains showed higher growth rates, dam-overexpressing strains showed decreased growth rates. In this study, we revealed that a DNA methyltransferase may regulate persister cell formation in A. baumannii, while RecC seems to mediate epigenetic regulation of persister cell formation. However, Dam and RecC may act at different persister cell formation states. IMPORTANCE Bacterial persister cells are not killed by high concentration of antibiotics, despite its antibiotic susceptibility. It has been known that they may cause antibiotic treatment failure and contribute to the evolution of antibiotic resistance. Although many mechanisms have been suggested and verified for persister cell formation, many remains to be uncovered. In this study, we report that DNA methyltransferase leads to an increase in persister cell formation, through transcriptional activation of several regulatory genes. Our results suggest that DNA methyltransferases could be target proteins to prevent formation of persister cells.


Assuntos
Acinetobacter baumannii , Acinetobacter baumannii/genética , Metiltransferases/genética , Epigênese Genética , Testes de Sensibilidade Microbiana , Antibacterianos/farmacologia , Metilases de Modificação do DNA/genética
6.
Nucleic Acids Res ; 50(19): 11315-11330, 2022 10 28.
Artigo em Inglês | MEDLINE | ID: mdl-36283692

RESUMO

The pathogenic Listeria monocytogenes bacterium produces the flagellum as a locomotive organelle at or below 30°C outside the host, but it halts flagellar expression at 37°C inside the human host to evade the flagellum-induced immune response. Listeria monocytogenes GmaR is a thermosensor protein that coordinates flagellar expression by binding the master transcriptional repressor of flagellar genes (MogR) in a temperature-responsive manner. To understand the regulatory mechanism whereby GmaR exerts the antirepression activity on flagellar expression, we performed structural and mutational analyses of the GmaR-MogR system. At or below 30°C, GmaR exists as a functional monomer and forms a circularly enclosed multidomain structure via an interdomain interaction. GmaR in this conformation recognizes MogR using the C-terminal antirepressor domain in a unique dual binding mode and mediates the antirepressor function through direct competition and spatial restraint mechanisms. Surprisingly, at 37°C, GmaR rapidly forms autologous aggregates that are deficient in MogR neutralization capabilities.


Assuntos
Listeria monocytogenes , Humanos , Listeria monocytogenes/genética , Proteínas de Bactérias/metabolismo , Flagelos/genética , Flagelos/metabolismo , Regulação Bacteriana da Expressão Gênica
7.
J Hazard Mater ; 438: 129412, 2022 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-35780731

RESUMO

A suitable and non-invasive methanol sensor workable in ambient temperature conditions with a high response has gained wide interest to prevent detrimental consequences for industrial workers from its low-level intoxication. In this work, we present a tunable and highly responsive ppb-level methanol gas sensor device working at room temperature via a bottom-up synthetic approach using exfoliated graphene sheet (EGs) and ZnO quantum dots (QDs) on an aluminum anodic oxide (AAO) template. It is verified that EGs-supported AAO with a vertical electrode configuration enabled high and fast-responsive methanol sensing. Moreover, the hydroxyl and carboxyl groups of the high surface area EGs and ZnO QDs with a 3.37 eV bandgap efficiently absorbing UV light led to 56 times high response due to the enhanced polarization on the sensor surface compared to non-UV-radiated EGs/AAO at 800 ppb of methanol. The optimal resonance frequency of methanol is determined to be 100 kHz, which could detect methanol with high response of 2.65% at 100 ppm. The limit of detection (LOD) concentration is obtained at 2 ppb level. This study demonstrates the potential of UV-assisted ZnO, EGs, and AAO-based capacitance sensor material for rapidly detecting hazardous gaseous light organic molecules at ambient conditions, and the overall approach can be easily expanded to a novel non-invasive monitoring strategy for light and hazardous volatile organic exposures.


Assuntos
Grafite , Nanoestruturas , Óxido de Zinco , Óxido de Alumínio/química , Gases , Grafite/química , Humanos , Metanol , Nanoestruturas/química , Temperatura , Óxido de Zinco/química
8.
Materials (Basel) ; 15(12)2022 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-35744268

RESUMO

Thermoelectric generators are solid-state energy-converting devices that are promising alternative energy sources. However, during the fabrication of these devices, many waste scraps that are not eco-friendly and with high material cost are produced. In this work, a simple powder processing technology is applied to prepare n-type Bi2Te3 pellets by cold pressing (high pressure at room temperature) and annealing the treatment with a canning package to recycle waste scraps. High-pressure cold pressing causes the plastic deformation of densely packed pellets. Then, the thermoelectric properties of pellets are improved through high-temperature annealing (500 ∘C) without phase separation. This enhancement occurs because tellurium cannot escape from the canning package. In addition, high-temperature annealing induces rapid grain growth and rearrangement, resulting in a porous structure. Electrical conductivity is increased by abnormal grain growth, whereas thermal conductivity is decreased by the porous structure with phonon scattering. Owing to the low thermal conductivity and satisfactory electrical conductivity, the highest ZT value (i.e., 1.0) is obtained by the samples annealed at 500 ∘C. Hence, the proposed method is suitable for a cost-effective and environmentally friendly way.

9.
Nanomaterials (Basel) ; 12(12)2022 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-35745351

RESUMO

Dopamine is a neurotransmitter that helps cells to transmit pulsed chemicals. Therefore, dopamine detection is crucial from the viewpoint of human health. Dopamine determination is typically achieved via chromatography, fluorescence, electrochemiluminescence, colorimetry, and enzyme-linked methods. However, most of these methods employ specific biological enzymes or involve complex detection processes. Therefore, non-enzymatic electrochemical sensors are attracting attention owing to their high sensitivity, speed, and simplicity. In this study, a simple one-step fabrication of a Bi2Te3-nanosheet/reduced-graphene-oxide (BT/rGO) nanocomposite was achieved using a hydrothermal method to modify electrodes for electrochemical dopamine detection. The combination of the BT nanosheets with the rGO surface was investigated by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. Electrochemical impedance spectroscopy, cyclic voltammetry, and differential pulse voltammetry were performed to analyze the electrochemical-dopamine-detection characteristics of the BT/rGO nanocomposite. The BT/rGO-modified electrode exhibited higher catalytic activity for electrocatalytic oxidation of 100 µM dopamine (94.91 µA, 0.24 V) than that of the BT-modified (4.55 µA, 0.26 V), rGO-modified (13.24 µA, 0.23 V), and bare glassy carbon electrode (2.86 µA, 0.35 V); this was attributed to the synergistic effect of the electron transfer promoted by the highly conductive rGO and the large specific surface area/high charge-carrier mobility of the two-dimensional BT nanosheets. The BT/rGO-modified electrode showed a detection limit of 0.06 µM for dopamine in a linear range of 10-1000 µM. Additionally, it exhibited satisfactory reproducibility, stability, selectivity, and acceptable recovery in real samples.

10.
Front Microbiol ; 13: 891926, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35592005

RESUMO

The Tol-Pal system is a transenvelope complex widely conserved among Gram-negative bacteria. It is recruited to the septal ring during cytokinesis, and its inactivation causes pleiotropic phenotypes mainly associated with the division process. From our genetic screen to identify factors required for delaying lysis upon treatment of beta lactams, we discovered that the tol-pal mutant shares similar defects with mutants of the major class A PBP system (PBP1b-LpoB) in terms of lysis prevention. Further phenotypic analyses revealed that the Tol-Pal system plays an important role in maintaining cell integrity not only during septation, but also during cell elongation. Simultaneous inactivation of the Tol-Pal system and the PBP1b-LpoB system leads to lysis during cell elongation as well as during division. Moreover, production of the Lpo activator-bypass PBP1b, but not wild-type PBP1b, partially suppressed the Tol-Pal defect in maintaining cell integrity upon treatment of mecillinam specific for the Rod system, suggesting that the Tol-Pal system is likely to be involved in the activation of aPBP by Lpo factors. Overall, our results indicate that the Tol-Pal system plays an important role in maintaining cell wall integrity during elongation in addition to its multifaceted roles during cytokinesis.

11.
Biochem Biophys Res Commun ; 612: 162-168, 2022 07 05.
Artigo em Inglês | MEDLINE | ID: mdl-35526497

RESUMO

Helicobacter pylori is a pathogenic bacterium that causes gastric ulcers and cancer. Among the diverse virulence genes of H. pylori, the IceA gene was identified to be expressed upon adherence to host cells. The IceA gene has two alleles, iceA1 and iceA2, which encode completely different proteins. IceA1 protein was shown to exert endonuclease activity, whereas IceA2 has never been analyzed at the molecular level. Based on a sequence analysis, IceA2 proteins differ in length depending on the strain and are classified into five groups (A-E). To structurally characterize IceA2, we determined the crystal structure of group-D IceA2 (IceA2sD) and performed a modeling-based comparative analysis of IceA2 groups. IceA2sD consists of three ß-sheet repeats and serially arranges them like the ß-propeller structure of the WD40 domain. However, each ß-sheet of IceA2 is stabilized using a unique structural motif that is not observed in WD40. Moreover, IceA2sD lacks an additionally appended ß-strand and does not form the Velcro-like closure of WD40. Therefore, IceA2sD adopts a curved rod-like structure rather than an enclosed circular structure in WD40. IceA2 proteins contain 1-4 ß-sheet modules depending on the groups and are modeled to be highly diverse in size and shape.


Assuntos
Infecções por Helicobacter , Helicobacter pylori , Antígenos de Bactérias , Proteínas da Membrana Bacteriana Externa/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Genótipo , Infecções por Helicobacter/microbiologia , Helicobacter pylori/metabolismo , Humanos , Virulência/genética
12.
J Microbiol ; 60(5): 461-468, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35437623

RESUMO

CrrAB two-component regulatory system is associated with colistin resistance in Klebsiella pneumoniae. Recently, some K. pneumoniae isolates lacking crrAB genes have been identified. In this study, we investigated the distribution and structural variation of the crrBAC-kexD cluster. To evaluate the structural variation of the crrBAC-kexD cluster, we explored 59 clinical K. pneumoniae isolates from Korea, and 508 whole genomes of K. pneumoniae and other strains of Klebsiella sp. Significant structural variations in crrBAC-kexD and its surrounding regions were identified among K. pneumoniae genomes. Within the genus Klebsiella, the cluster was identified only in K. pneumoniae, K. variicola, and K. quasipneumoniae, which form the K. pneumoniae complex. Among the 304 available K. pneumoniae genomes, an intact crrBAC-kexD cluster was identified in 178 isolates (58.6%), while the cluster was absent in 90 isolates (29.6%). Partial deletions within the cluster were identified in 22 genomes (7.2%). The most diverse structural patterns of the crrBAC-kexD cluster were observed in ST11 strains. Some clades lacked the crrBAC-kexD cluster. The crrBAC-kexD cluster was identified in the genomes of other bacterial species, including Citrobacter freundii and Enterobacter ludwigii. The crrBAC-kexD cluster is proposed to have been acquired by the ancestor of the K. pneumoniae complex from other bacterial species and the cluster may have been lost and re-acquired repeatedly in K. pneumoniae strains according to the phylogenetic analysis. The dynamic evolution of the crrBAC-kexD cluster suggests that it may have other roles, in addition to colistin resistance, in bacterial physiology.


Assuntos
Colistina , Infecções por Klebsiella , Antibacterianos/farmacologia , Proteínas de Bactérias/genética , Colistina/farmacologia , Humanos , Klebsiella/genética , Infecções por Klebsiella/microbiologia , Klebsiella pneumoniae/genética , Testes de Sensibilidade Microbiana , Família Multigênica , Filogenia
13.
Front Microbiol ; 13: 878049, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35418955

RESUMO

Cell wall assembly of Gram-negative bacteria requires DD-endopeptidase activity that cleaves peptidoglycan (PG) crosslinks in addition to PG synthetic activity, and the activity of DD-endopeptidases needs to be tightly regulated to maintain cell wall integrity during PG expansion. Among the major DD-endopeptidases functioning for PG assembly in Escherichia coli, MepS and MepM have been shown to be negatively controlled by the periplasmic protease Prc. In this study, we performed a genetic selection using the synthetic lethality between the mepS and mepM mutations in rich medium to uncover regulatory mechanisms controlling the activity of DD-endopeptidases other than MepS and MepM. This selection revealed mutations in prc and nlpI as suppressors. Gene deletion analyses revealed that MepH is required for suppression of the MepS- MepM- growth defect by the prc or nlpI mutation. We also discovered that MepH is directly degraded by Prc and that this degradation is further promoted by NlpI. Thus, our study showed that all three DD-endopeptidases which play major roles in PG assembly of E. coli under normal physiological conditions are controlled by a common periplasmic protease.

14.
Front Chem ; 10: 813008, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35198538

RESUMO

Reinforced concrete is among the most multifaceted materials used in the construction field. Maintaining the resistance of reinforced concrete to weathering, abrasion, and chemical attack, particularly in aggressive natural conditions such as seawater environments, is challenging. The main factor in the degradation of reinforced-concrete durability is chloride penetration, which accelerates iron alloy corrosion and facilitates structural degradation. In this study, calcium-iron-based layered double hydroxides (CaFe-LDHs) were fabricated at room temperature, followed by structural modulation, and their effectiveness in mitigating iron alloy corrosion due to chloride ions (in 3.5 wt% of NaCl) was investigated. The synthesized CaFe-LDHs with phase transfer notably improved the Cl- removal capacity (Qmax) to 881.83 mg/g, which is more than three times that reported based on previous studies. The novelty of this research lies in the sophisticated structural and phase transformations of the as-synthesized CaFe-LDHs, determination of crucial factors for chloride ion removal, and suggestion of calcium-iron-based layered double oxide (CaFe-LDO)-based chloride ion removal mechanisms considering chemical and ion-exchange reactions. Moreover, when the phase-transformed LDHs, C-700 LDOs, were applied to inhibit iron alloy corrosion, a noticeable inhibition efficiency of 98.87% was obtained, which was an 11-fold improvement compared to the case of iron alloys without LDOs. We believe this work can provide new insights into the design of CaFe-LDOs for the enhancement of the lifespan of reinforced concrete structures.

15.
J Microbiol ; 59(12): 1067-1074, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34865196

RESUMO

Transposon insertion site sequencing (TIS) is a technique that determines the insertion profile of a transposon mutant library by massive parallel sequencing of transposon-genomic DNA junctions. Because the transposon insertion profile reflects the abundance of each mutant in the library, it provides information to assess the fitness contribution of each genetic locus of a bacterial genome in a specific growth condition or strain background. Although introduced only about a dozen years ago, TIS has become an important tool in bacterial genetics that provides clues to study biological functions and regulatory mechanisms. Here, I describe a protocol for generating high density transposon insertion mutant libraries and preparing Illumina sequencing samples for mapping the transposon junctions of the transposon mutant libraries using Pseudomonas aeruginosa as an example.


Assuntos
Elementos de DNA Transponíveis , DNA Bacteriano/genética , Sequenciamento de Nucleotídeos em Larga Escala , Pseudomonas aeruginosa/genética , Análise de Sequência de DNA/métodos , Sequência de Bases , Biblioteca Gênica , Aptidão Genética , Genoma Bacteriano , Mutagênese Insercional , Mutação , Pseudomonas aeruginosa/crescimento & desenvolvimento
16.
Nanoscale ; 13(18): 8442-8451, 2021 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-33908426

RESUMO

Metal conductive patterning has been studied as an alternative to the most commonly used indium tin oxide electrodes. Printed electrodes are fabricated by several complicated processes including etching, photolithography, and laser- and template-based techniques. However, these patterning methods have increasingly encountered critical issues of long manufacturing times and high equipment costs that necessitate vacuum and high-temperature conditions. In this study, we present a template-free solution-based patterning method for the fabrication of transparent electronics by inducing segregation-based networks of silver nanowires (SGAgNWs); this is a potential method to fabricate cost effective and scalable optoelectronics. Micro-dimensional fine-patterned segregated networks with conductive cells are created by the self-assembly of one-dimensional nanomaterials under optimal ink conditions wherein different types of solvents and aspect ratios of silver nanowires (AgNWs) are formulated. Photoelectric properties can be controlled by adjusting the size of the cell, which is an empty domain surrounded by the AgNW assembly with microscale cell-to-cell distance dimensions ranging between 4 to 345 µm. The as-obtained AgNW metal grid-formulated on a polyethylene terephthalate film-was identified as a high-performance transparent electrode (TE) device with excellent optoelectronic properties of 87.08% transmittance and 50 Ω â–¡-1 resistance. In addition, the electrical conductivity of the TE film is enhanced with a very low haze of less than 4% because of the intense pulsed light treatment that diminished the sheet resistance to 21.36 Ω â–¡-1, which is attributed to the creation of welded silver networks. The SGAgNW concept for TE technology demonstrates a very promising potential for use in next-generation flexible electronic devices.

17.
RSC Adv ; 11(18): 10951-10961, 2021 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-35423558

RESUMO

The three anionic species; chloride (Cl-), sulfate (SO4 2-), and carbonate (CO3 2-), are typical chemical factors that environmentally accelerate failure of concrete structures with steel rebar through long-term exposure. Efficient removal of these deleterious anions at the early stage of penetration is crucial to enhance the lifespan and durability of concrete structures. Here, we synthesize CaFe-layered double hydroxide (CaFe-LDHs) by a simple one-step co-precipitation technique and structural modulation by calcination process. It is applied for the removal of Cl-, SO4 2-, and CO3 2- anions as well as corrosion inhibition on steel rebar in aqueous solutions. The synthesized CaFe-LDHs with phase transfer show notable improvement of removal capacity (Q max) toward Cl- and SO4 2- over 3.4 times and over 5.69 times, respectably, then those of previous literatures. Furthermore, the steel rebar exposed to an aqueous solution containing the three anionic sources shows a fast corrosion rate (1876.56 × 10-3 mm per year), which can be remarkably inhibited showing 98.83% of corrosion inhibition efficiency when it is surrounded by those CaFe-LDHs. The novel adsorption mechanisms of these CaFe-LDHs-induced crystals and corresponding corrosion protection properties are elucidated drawing on synergy of memory effects and chemical reactions.

18.
J Microbiol ; 57(12): 1041-1047, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31758393

RESUMO

Suppression analysis is used for the identification of new genes and genetic interactions when there is a notable phenotype available for genetic selection or screening. A random genomic DNA library constructed on a multi-copy plasmid is a useful tool for suppression analysis when one expects that an overdose of a few genes will suppress the phenotype. These libraries have been successfully used to determine the function of a gene by revealing genes whose functions are related to the gene of interest. They have also been used to identify the targets of chemical or biological agents by increasing the number of unaffected target gene products in a cell. In this article, I will discuss important considerations for constructing multicopy genomic DNA libraries. The protocol provided in this paper should be a useful guide for constructing genomic DNA libraries in many bacterial species for which multi-copy plasmids are available.


Assuntos
Bactérias/genética , Biblioteca Gênica , Genômica , DNA Bacteriano , Dosagem de Genes , Genes Bacterianos , Fenótipo , Plasmídeos , Seleção Genética
19.
ACS Appl Mater Interfaces ; 11(50): 47015-47024, 2019 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-31725260

RESUMO

We present a thermochemical hydrogen (TCH) gas sensor fabricated with Pt-decorated exfoliated graphene sheets and a tellurium nanowire-based thermoelectric (TNTE) layer operating at room temperature in wet air. The sensor device was able to detect 50 ppm to 3% of hydrogen gas within several seconds (response/recovery times of 6/5.1 s at 4000 ppm of hydrogen gas) at room temperature due to the relatively high surface area of homogeneously dispersed Pt nanocrystals (∼8 nm) decorated on graphene sheets and the excellent Seebeck coefficient (428 µV/K) of the TNTE layer. Furthermore, it was observed that the effect of the relative humidity on sensing properties was greatly minimized by incorporating Pt-decorated graphene sheets. These results indicate that our device has great potential as a low power consumption gas sensor for IoTs.

20.
ACS Appl Mater Interfaces ; 11(29): 26222-26227, 2019 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-31117434

RESUMO

Rare-earth-based core-shell spring nanomagnets have been intensively studied in the permanent magnet industry. However, the inherent agglomeration characteristics of zero-dimensional (0-D) magnetic nanoparticles are an issue in practical fabrication of magnetic nanocomposites due to deterioration in exchange-coupling interactions, resulting in inferior magnetic performance. Here, with an aim to overcome the structural limitations, we report a new type of SmCo/FeCo core-shell nanomagnet with a well-dispersed one-dimensional (1-D) structure prepared by a combination of electrospinning and electroless plating processes. An FeCo layer with a tailored thickness on nanoscale SmCo was produced to achieve a sufficient exchange-coupling effect. The influence of electroless plating time on the microstructure of fibers was discussed, and comparisons were made as a function of the magnet shape. A 1-D SmCo/FeCo spring nanomagnet having a core diameter ranging from 150 to 200 nm and a shell thickness of 15-20 nm showed a potent exchange-coupling effect compared with its 0-D counterpart. This effectively reduced self-aggregation and further showed a remarkable enhancement in (BH)max (above 45.7%). We think that this novel structure marks a new era in the exchange-spring magnet industry and may overcome the limitations of traditional core-shell nanomagnets.

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