This article reports the preparation of recycled polypropylene (RPP)/bamboo fiber (BF) composite via direct melt blends using a twin screw extruder. The effects of the chemical treatment of BF ...surface (alkaline and acetylation) on fiber structure and composite mechanical, thermal, rheological properties have been investigated. We showed that alkali treatment increases the contact surface of BF within composites, resulting in a more homogenous dispersion of fibers in the polymer matrix. Alkali treatment improves mechanical properties such as tensile strength as well as the Charpy impact strength. Reinforced composites obtained with acetylated BF show better mechanical properties due to grafting of acetyl groups onto the cellulose fiber surface and thus improve compatibility between BF and matrix. The rheological properties of RPP/BF composites depending on the BF content and treatment methods are also analyzed. Predominant factors that influence the properties of relevant materials are identified. Maleic anhydride grafted polypropylene is used as a compatibilizer to improve the adhesion between the cellulosic phase and the RPP matrix.
•Biofilm formation is leading threat for developing antibacterial resistance in bacteria.•Spirulina platensis are non-toxic and edible source of cyanobacteria with rich nutrients.•AgNPs synthesized ...using Spirulinamethanolic extract (SME) inhibited the biofilm of P. aeruginosa.•AgNPs also inhibited the production of Rhamnolipid in P. aeruginosa.•AgNPs inhibited P. aeruginosa biofilm formation in urinary catheters.
Methanolic (SME) extract of the biologically safe and edible cyanobacteria, Spirulina platensis was used for the green fabrication of silver nanoparticles (AgNPs). Characterization using UV–vis spectra showed the absorbance at 420 nm confirming the successful synthesis of AgNPs. Further characterization using XRD, DLS, SEM and TEM analysis showed the synthesis of stable (-43.6 mV), spherical and dispersed Ag nanoparticles with an average size of 29 nm. Antibiofilm potential of AgNPs (10, 25, 50, 75 and 100 μg mL−1) was tested against Pseudomonas aeruginosa PA14 showed a maximum of 85.63 % inhibition of biofilm formation at 100 μg mL−1. Phenotypical change in the biofilm morphology was confirmed using light and confocal microscopic analysis. Inhibiting the production of rhamnolipid by P. aeruginosa was observed at the concentration of 25 μg mL−1. Further application of AgNPs to prevent biofilm formation in urinary catheters were tested against P. aeruginosa PA14. Thus, the present study will promote an idea to use AgNPs synthesized using SME for coating medical device and prevent biofilm associated infections and diseases.
3%Ce- and 3%La-promoted 10%Cu/Al2O3 catalysts were synthesized via a sequential incipient wetness impregnation approach and implemented for ethanol CO2 reforming (ECR) at 948–1023 K and ...stoichiometric feed ratio. CeO2 and La2O3 promoters reduced CuO crystallite size from 32.4 to 27.4 nm due to diluting impact and enhanced the degree of reduction of CuO → Cu0. Irrespective of reaction temperature, 3%La–10%Cu/Al2O3 exhibited the highest reactant conversions, H2 and CO yields followed by 3%Ce–10%Cu/Al2O3 and 10%Cu/Al2O3. The greatest C2H5OH and CO2 conversions of 87.6% and 55.1%, respectively were observed on 3%La–10%Cu/Al2O3 at 1023 K whereas for all catalysts, H2/CO ratios varying from 1.46 to 1.91 were preferred as feedstocks for Fischer-Tropsch synthesis. Activation energy for C2H5OH consumption was also reduced with promoter addition from 53.29 to 47.05 kJ mol−1. The thorough CuO → Cu0 reduction by H2 activation was evident and the Cu0 active phase was resistant to re-oxidation during ECR for all samples. Promoters addition reduced considerably the total carbon deposition from 40.04% to 27.55% and greatly suppressed non-active graphite formation from 26.94% to 4.20% because of their basic character and cycling redox enhancement.
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•3%La–10%Cu/Al2O3 exhibited high C2H5OH (87.6%) and CO2 (55.1%) conversions.•Promoter addition reduced C2H5OH activation energy from 53.29 to 47.05 kJ mol−1.•CeO2 and La2O3 hindered carbon deposition from 40.04% to 27.55%.
In this study, the degradation of a water-borne acrylic coating and the influence of rutile-TiO2 (R–TiO2) nanoparticles and a hindered amine light stabilizer (HALS) on its photo-stability in ...accelerated aging environment has been quantitatively studied by monitoring the chemical modifications occurring upon aging conditions. By using non-destructive analytical methods, like IR and UV-visible spectroscopy, 3D laser microscopy, SEM observations and weight loss measurements, it was possible to follow continuously the formation of photo-oxidative products and the loss of the binder functional groups on a sample undergoing accelerated aging. For the first time, numerous dark spots, randomly dispersed on the whole surface of the sample upon UV/condensation exposure are successfully observed and explained by using a novel technique 3D laser microscopy. Our findings also confirm that HALS greatly improved photo-stability to the coating thank to its free radical and hydrogen peroxide scavenging capacity. This work provides some useful information for a better understanding of the degradation behavior of water-borne acrylic coating under accelerated aging conditions.
Incorporation of nanofillers into the organic coatings might enhance their barrier performance, by decreasing the porosity and zigzagging the diffusion path for deleterious species. Thus, the ...coatings containing nanofillers are expected to have significant barrier properties for corrosion protection and reduce the trend for the coating to blister or delaminate. On the other hand, high hardness could be obtained for metallic coatings by producing the hard nanocrystalline phases within a metallic matrix. This article presents a review on recent development of nanocomposite coatings, providing an overview of nanocomposite coatings in various aspects dealing with the classification, preparative method, the nanocomposite coating properties, and characterization methods. It covers potential applications in areas such as the anticorrosion, antiwear, superhydrophobic area, self-cleaning, antifouling/antibacterial area, and electronics. Finally, conclusion and future trends will be also reported.
Microbial volatile compounds (mVCs) may cause stomatal closure to limit pathogen invasion as part of plant innate immune response. However, the mechanisms of mVC-induced stomatal closure remain ...unclear. In this study, we co-cultured
Enterobacter aerogenes
with Arabidopsis
(Arabidopsis thaliana)
seedlings without direct contact to initiate stomatal closure. Experiments using the reactive oxygen species (ROS)-sensitive fluorescent dye, H
2
DCF-DA, showed that mVCs from
E. aerogenes
enhanced ROS production in guard cells of wild-type plants. The involvement of ROS in stomatal closure was then demonstrated in an ROS production mutant (
rbohD
). In addition, we identified two stages of signal transduction during
E. aerogenes
VC-induced stomatal closure by comparing the response of wild-type Arabidopsis with a panel of mutants. In the early stage (3 h exposure),
E. aerogenes
VCs induced stomatal closure in wild-type and receptor-like kinase THESEUS1 mutant (
the1-1
) but not in
rbohD
, plant hormone-related mutants (
nced3
,
erf4
,
jar1-1
), or MAPK kinase mutants (
mkk1
and
mkk3
). However, in the late stage (24 h exposure),
E. aerogenes
VCs induced stomatal closure in wild-type and
rbohD
but not in
nced3
,
erf4
,
jar1-1
,
the1-1
,
mkk1
or
mkk3
. Taken together, our results suggest that
E. aerogenes
mVC-induced plant immune responses modulate stomatal closure in Arabidopsis by a multi-phase mechanism.
ABSTRACT
Increasing evidence suggests that in disease-suppressive soils, microbial volatile compounds (mVCs) released from bacteria may inhibit the growth of plant-pathogenic fungi. However, the ...antifungal activities and molecular responses of fungi to different mVCs remain largely undescribed. In this study, we first evaluated the responses of pathogenic fungi to treatment with mVCs from
Paenarthrobacter ureafaciens
. Then, we utilized the well-characterized fungal model organism
Saccharomyces cerevisiae
to study the potential mechanistic effects of the mVCs. Our data showed that exposure to
P. ureafaciens
mVCs leads to reduced growth of several pathogenic fungi, and in yeast cells, mVC exposure prompts the accumulation of reactive oxygen species. Further experiments with
S. cerevisiae
deletion mutants indicated that Slt2/Mpk1 and Hog1 MAPKs play major roles in the yeast response to
P. ureafaciens
mVCs. Transcriptomic analysis revealed that exposure to mVCs was associated with 1,030 differentially expressed genes (DEGs) in yeast. According to gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses, many of these DEGs are involved in mitochondrial dysfunction, cell integrity, mitophagy, cellular metabolism, and iron uptake. Genes encoding antimicrobial proteins were also significantly altered in the yeast after exposure to mVCs. These findings suggest that oxidative damage and mitochondrial dysfunction are major contributors to the fungal toxicity of mVCs. Furthermore, our data showed that cell wall, antioxidant, and antimicrobial defenses are induced in yeast exposed to mVCs. Thus, our findings expand upon previous research by delineating the transcriptional responses of the fungal model.
IMPORTANCE
Since the use of bacteria-emitted volatile compounds in phytopathogen control is of considerable interest, it is important to understand the molecular mechanisms by which fungi may adapt to microbial volatile compounds (mVCs).
Paenarthrobacter ureafaciens
is an isolated bacterium from disease-suppressive soil that belongs to the
Actinomycetota
phylum.
P. ureafaciens
mVCs showed a potent antifungal effect on phytopathogens, which may contribute to disease suppression in soil. However, our knowledge about the antifungal mechanism of mVCs is limited. This study has proven that mVCs are toxic to fungi due to oxidative stress and mitochondrial dysfunction. To deal with mVC toxicity, antioxidants and physical defenses are required. Furthermore, iron uptake and CAP proteins are required for antimicrobial defense, which is necessary for fungi to deal with the thread from mVCs. This study provides essential foundational knowledge regarding the molecular responses of fungi to inhibitory mVCs.
Since the use of bacteria-emitted volatile compounds in phytopathogen control is of considerable interest, it is important to understand the molecular mechanisms by which fungi may adapt to microbial volatile compounds (mVCs).
Paenarthrobacter ureafaciens
is an isolated bacterium from disease-suppressive soil that belongs to the
Actinomycetota
phylum.
P. ureafaciens
mVCs showed a potent antifungal effect on phytopathogens, which may contribute to disease suppression in soil. However, our knowledge about the antifungal mechanism of mVCs is limited. This study has proven that mVCs are toxic to fungi due to oxidative stress and mitochondrial dysfunction. To deal with mVC toxicity, antioxidants and physical defenses are required. Furthermore, iron uptake and CAP proteins are required for antimicrobial defense, which is necessary for fungi to deal with the thread from mVCs. This study provides essential foundational knowledge regarding the molecular responses of fungi to inhibitory mVCs.
Atomic force microscopy (AFM) has been extensively used for the nanoscale characterization of polymeric materials. The coupling of AFM with infrared spectroscope (AFM-IR) provides another advantage ...to the chemical analyses and thus helps to shed light upon the study of polymers. This paper reviews some recent progress in the application of AFM and AFM-IR in polymer science. We describe the principle of AFM-IR and the recent improvements to enhance its resolution. We also discuss the latest progress in the use of AFM-IR as a super-resolution correlated scanned-probe infrared spectroscopy for the chemical characterization of polymer materials dealing with polymer composites, polymer blends, multilayers, and biopolymers. To highlight the advantages of AFM-IR, we report several results in studying the crystallization of both miscible and immiscible blends as well as polymer aging. Finally, we demonstrate how this novel technique can be used to determine phase separation, spherulitic structure, and crystallization mechanisms at nanoscales, which has never been achieved before. The review also discusses future trends in the use of AFM-IR in polymer materials, especially in polymer thin film investigation.
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•The effect of photostabilizers on the weathering durability of acrylic polyurethane coatings has been investigated.•Durability of coating samples under accelerated weathering ...conditions is compared with those exposed at the outdoor conditions until 10 years.•The as-prepared coating exhibits durability over 72 cycles which is equivalent to 10 years in outdoor exposure conditions.•The degradation mechanism of coating in accelerated aging test and outdoor exposure conditions is compared.
The effect of photo-stabilizers on the crosslinking and weathering durability of acrylic polyurethane coatings based on the HSU 1168 acrylic polyol and the Desmodur N-75 polyisocyanate has been investigated. The aging of these coatings under accelerated weathering conditions and natural outdoor conditions upto a decade has been compared. Our findings showed that photo-stabilizers had a negligible effect on the conversion of isocyanate groups during the photocroslinking but enhanced the aging resistance. Coatings containing photo-absorbers exhibited an excellent weathering durability, upto 72 cycles upon accelerated aging and 10 years in natural outdoor exposure, while the unstabilized coatings appeared serious cracks, damages and chalking after 48 cycles of accelerated aging and after 5 years in outdoor weathering exposure. The degradation of coatings was also investigated by monitoring atomic force microscopy, weight loss and gloss loss, cracking, blistering and flacking of the coating. The degradation of coatings in the surface of natural and accelerated was compared by using Atomic force microscopy coupling with naonoscale infrared spectroscopy (AFM- IR) by following oxidized products on the coating surface.
Nowadays, air pollution is an increasingly important topic, as environmental regulations require limiting pollutant emissions. This problem requires new techniques to reduce emissions by either ...improving the current emission control systems and processes or installing new hybrid treatment systems. These are of broad diversity, and every system has its advantages and disadvantages. The tendency is, accordingly, to combine various techniques to achieve more acceptable and suitable treatment. Recent studies suggest that the combination of photocatalysis and plasma in a reactor can offer attractive pollutant treatment efficiency with a minimum of partially oxidized by-products than that of these processes taken separately. However, there is little review of the capability of this pairing to treat different brands of pollutants. Besides, available data concerning reactor design with flows treated 10 to 1000 times higher than those studied at the lab scale. This review paid particular attention to determine the reaction mechanisms in terms of engineering and design of combination reactors (plasma and catalysis). Likewise, we developed the effect of critical parameters such as pollutant load, relative humidity, and flow rate to understand the degradation kinetics of specific pollutants individually by using plasma and photocatalysis. Additionally, this review compares different designs of cold plasma reactors combination with heterogeneous catalysis with special attention on synergistic and antagonistic effects of using plasma and photocatalysis processes at the laboratory, pilot, and industrial scales. Therefore, the elements discussed in this review stick well to the first theme on pollution prevention of the special issue concerning pollution prevention and the application of clean technologies to promote a circular (bio) economy.
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•Determination of the reaction mechanisms and design of combination reactors.•Scan of the process parameters and operating conditions.•Comparison of different designs of cold plasma combination reactors with heterogeneous catalysis.•Synergistic and antagonistic effects of using plasma and photocatalysis processes.
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