Metallic nanoparticles currently show multiple applications in the industrial, clinical and environmental fields due to their particular physicochemical characteristics. Conventional approaches for ...the synthesis of silver nanoparticles (AgNPs) are based on physicochemical processes which, although they show advantages such as high productivity and good monodispersity of the nanoparticles obtained, have disadvantages such as the high energy cost of the process and the use of harmful radiation or toxic chemical reagents that can generate highly polluting residues. Given the current concern about the environment and the potential cytotoxic effects of AgNPs, once they are released into the environment, a new green chemistry approach to obtain these nanoparticles called biosynthesis has emerged. This new alternative process counteracts some limitations of conventional synthesis methods, using the metabolic capabilities of living beings to manufacture nanomaterials, which have proven to be more biocompatible than their counterparts obtained by traditional methods. Among the organisms used, fungi are outstanding and are therefore being explored as potential nanofactories in an area of research known as mycosynthesis. For all the above, this paper aims to illustrate the advances in state of the art in the mycosynthesis of AgNPs, outlining the two possible mechanisms involved in the process, as well as the AgNPs stabilizing substances produced by fungi, the variables that can affect mycosynthesis at the in vitro level, the applications of AgNPs obtained by mycosynthesis, the patents generated to date in this field, and the limitations encountered by researchers in the area.
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•Oligo phenylenevinylenes (OPVs) were employed as heterogeneous photocatalysts for the first time in the degradation of an aqueous dye.•Degradation of IC-dye proceeds via generation ...of superoxide radicals, singlet oxygen, and direct oxidation via the OPV.•The HOMO levels of OPV systems indicate OH· radical formation via direct water oxidation is not favorable.•OPV degradation products were identified, employing ESI-IT experiments.•The use of oxalic acid as a sacrificial electron donor for OPVs provided superior discoloration efficiency compared to TiO2.
Four oligo-phenylenevinylenes (OPVs) were synthesized by the Mizoroki-Heck cross-coupling reaction to provide a deeper understanding of the mechanism and fate of phenylenevinylene systems when applied to the heterogeneous photocatalytic degradation of indigo carmine (IC) dye in aqueous media. OPVs displayed visible light absorption near 500 nm and appreciable emission properties. The stability, mechanism, and photodegradation activity of the OPV systems over aqueous indigo carmine were investigated using radical scavengers, a singlet oxygen (1O2) trap, and ESI-IT-MS. It was confirmed that superoxide radical (O2·−), 1O2, and direct oxidation are responsible for dye degradation. Hydroxide radical formation, under neutral pH conditions, does not occur, and it was corroborated by the HOMO and LUMO levels of the photocatalysts. Additionally, the use of oxalic acid as an electron sacrificial donor was demonstrated as an effective approach to enhance the OPVs photocatalytic activity. However, a significant decrease in activity during the first three irradiation cycles was observed, indicating that the enhancement in photo- and chemical stability is required for further dye-contaminated water treatment applications.
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•We propose data enhancements for a small dataset.•A novel method to increase the quantity and variability of training images from a publicly available colonoscopy dataset.•The ...results indicating that our method is promising to improve automatic polyp detection.
Over the last years, the most relevant results in the context of polyp detection were achieved through deep learning techniques. However, the most common obstacles in this field are the small datasets with a reduced number of samples and the lack of data variability. This paper describes a method to reduce this limitation and improve polyp detection results using publicly available colonoscopic datasets.
To address this issue, we increased the number and variety of images from the original dataset. Our method consists on adding polyps to the dataset images. The developed algorithm performs a rigorous selection of the best region within the image to receive the polyp. This procedure preserves the realistic features of the images while creating more diverse samples for training purposes. Our method allows copying existing polyps to new non-polypoid target regions. We also develop a strategy to generate new and more varied polyps through generative adversarial neural networks. Hence, the developed approach enriches the training data, creating automatically new samples with their appropriate labels.
We applied the proposed data enhancement over a colonic polyp dataset. Thus, we can assess the effectiveness of our approach through a Faster R-CNN detection model. Performance results show improvements over the polyp detections while reducing the false-negative rate. The experimental results also show better recall metrics in comparison with both the original training set and other studies in the literature.
We demonstrate that our proposed method has the potential to increase the data variability and number of samples in a reduced polyp dataset, improving the polyp detection rate and recall values. These results open new possibilities for advancing the study and implementation of new methods to improve computer-assisted medical image analysis.
The elastodynamic half-space Green’s function has been the subject of research for more than a century since the Lamb’s classical solution. Here, we revisit the problem and present a new closed ...analytical solution, in frequency domain, based upon the Principle of Equipartition (EQP) of Energy. This principle asserts that the imaginary parts of the Green’s tensor components equal the average cross-correlations of the fields generated by the uniform incidence of
P
and
S
body waves and by Rayleigh surface waves with amplitudes weighted by partition factors. The real part of the Green’s function is the Hilbert transform of the imaginary part. We validate our results by comparing synthetic seismograms of well-known solutions for surface and buried forces and discuss the implications of this new solution. Constructing synthetic diffuse fields is a first step for identifying them in nature.
Graphical Abstract
To achieve a suitable packaging configuration, it is important first to determine the physicochemical characteristics related to the packaged product. In this study, the physicochemical ...characterization of fresh purple passion fruits of three different ripening stages was carried out to determine key variables for the packaging, such as O2 consumption and CO2–ethylene production rates. Subsequently, intermediate‐ripe fruits were packaged for 21 days at 6 °C under three packaging conditions: Xtend® perforated bags, low‐density polyethylene (LDPE) bags, and LDPE bags with a novel ethylene scavenger active additive (ESAA). It was observed that an equilibrium modified atmosphere was formed in the packages. For the Xtend® bags, the highest values of O2 (yo2 = 0.184 to 0.192) and lowest of CO2 (yco2 = 0.033 to 0.041) were reached, whereas for the LDPE bags with ESAA these values were moderate. In the case of ethylene, the LDPE bags showed the highest levels in the headspace (26 to 31 ppm), whereas the lowest levels were obtained in the LDPE bags with additive (2 to 4 ppm). These levels resulted in a delay in the ripening of the fruits during storage, which was verified through a sensory acceptability test that was carried out on the juice extracted from the fruits. In this sensory test, panelists identified similar characteristics between the fruits packaged with ESAA and the Xtend® bags, regarding the control fruits. The LDPE bags with the ethylene scavenger performed satisfactorily and can considerably delay the ripening, which may result in longer shelf life and conservation of fresh purple passion fruits.
Practical Application
This work presents a novel packaging proposal that reduces oxygen and ethylene levels in contact with purple passion fruits. Our proposed active packaging can be used to increase the fruit shelf life by improving its conservation conditions throughout the chain of storage, transport, and distribution in the market. With this, it will be possible to reduce the fruit's losses due to senescence and to reduce the substrate consumption by using a more effective packaging system.
Natural fibers are highly attractive materials for engineering applications. However, a comprehensive characterization of the fibers is key to further increase their application spectrum. Fique fiber ...is widely available in several geographical areas, but the existing literature on its physicochemical characteristics is scarce and the results are significantly widespread. In this work, we performed a thorough characterization of the Fique fiber, including chemical composition, thermal degradation, crystallinity, topographical and mechanical properties along with surface chemistry and interactions, macromolecules distribution and the non-previously reported extractives quantification. The fact that the extractives were quantified reduces the possibility of reporting non-structural sugars as part of the macromolecule’s distribution. The results indicate the fique fiber is mainly composed of macromolecules such as cellulose (42.1 wt%), hemicellulose (13 wt%) and lignin (18.2 wt%). The extractive content was 15.3 wt%. The thermal degradation signals a maximum degradation temperature of 360 °C. Surface chemical characterization indicates the fiber to be mainly of acid characteristic and with a variety of functional groups (carboxylic, phenolic, hydroxyl, and hemiacetal) determined by ATR-FTIR and weakly hydrophilic attribute. Mechanical characterization shows Young’s modulus of 24.31 GPa. These characteristics reveal that fique as an intermediate fiber, not as hard as sisal but not as soft as jute, with thermal, crystallinity bulk, and surface chemical composition attractive for an ample array of applications.
Using biopolymers functionalized with antibacterial agents to manufacture active packaging is a clean alternative to mitigate food losses due to postharvest plant diseases. In this study, two ...mycosynthetized AgNPs impregnation methodologies on cotton (cationization and in situ biochemical reduction) were used to obtain the antibacterial fibers (A-AgNPs-C and A-AgNPs-IBR), which, in addition to being characterized by SEM-EDX, XRD, were evaluated as antibacterial materials. The cotton fibers showed growth inhibition of Pectobacterium carotovorum at 48 h. The reuse tests of these cotton fibers showed that the two types of fibers could have up to three successive uses without losing their effectiveness, regardless of the impregnation method used. Is important to highlight that the retention tests indicated that the AgNPs remain attached to the A-AgNPs-C and A-AgNPs-IBR fibers after several successive washes. Finally, the mycosynthesized AgNPs were also impregnated on fique fibers (Fique-AgNPs) by cationization to obtain little antibacterial sacks. Nanostructured materials that in in vivo tests on potatoes showed only 7.8 % of affectation, while the tubers stored in the traditional sacks had an affectation of 25 %. This immobilization of AgNPs in natural fibers will allow the development of a nanobiotechnological application in the storage and transport of potatoes, after performing some additional cytotoxicity tests to guarantee its safety.
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•Comparison of two methods of immobilization of AgNPs mycosynthesized on cellulosic fibers.•Antimicrobial activity of the cellulose/AgNP fibers by quantitative methods against the plant pathogen P. carotovorum.•Reuse and retention tests of antibacterial cellulose/AgNPs fibers.•Antibacterial evaluation of a fique sack pilot manufactured after immobilizing the mycosynthesized AgNp's
In this study, hybrid nanoparticles composed of poly(methylmethacrylate-co-laurylmethacrylate) (PMMA-co-LMA) and poly(3-(trimethoxysilyl)propyl methacrylate) (PMS) obtained via seeded emulsion ...polymerisation were synthesised. A series of copolymers of LMA and MMA was obtained via emulsion polymerisation in the presence of β-cyclodextrin as a phase transport catalyst. The resulting spherical particles of approximately 50 nm were used as seeds for MPS polymerisation, resulting in spherical core-shell particles. These materials were evaluated as vehicles for limonene. Initially, it was observed that the extent of particle swelling by limonene was enhanced at the highest fractions of LMA. The same trend was obtained when the loading capacity and encapsulation efficiency were determined. Although when the core contained PLMA only, the particles exhibited the highest encapsulation capacity, these nanoparticles presented the poorest control on the release of limonene. The cytotoxicity evaluation of the core-shell nanoparticles revealed that they are slightly cytotoxic with cell viabilities higher than 70% at all the concentrations. Our results indicated that core-shell nanoparticles containing a core composed of P(MMA-co-LMA) and a siloxane shell were promising vehicles for nonpolar and volatile compounds, such as limonene, and they showed potential for applications in various fields, such as pest control, food and pharmaceutical industries.
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•Latex particles were prepared by emulsion polymerisation of laurylmethacrylate and methyl methacrylate.•Seed emulsion polymerisation used to obtain core-shell nanoparticles composed of a hydrophobic core and a polysiloxane shell.•The swelling of core-shell nanoparticles by limonene was monitored by dynamic light scattering.•The core-shell nanoparticles provided limonene a control release along 48 h.
The copolymerization with flexible and rigid spacers of 4,4’-((1E, 1′E)-(2,5-dimethoxy-1,4-phenylene)bis (ethene-2,1-diyl))dibenzoic acid, as a promising phenylene vinylene-based (PV) organic ...photocatalyst, was examined as a strategy to validate the effect of such chemical modifications in the modulation of the photocatalytic properties of this organic
-conjugated moiety. The polymers prepared here were fully characterized and evaluated as photocatalysts in the degradation of indigo carmine dye under two different irradiation scenarios (UVA and visible), consistently displaying a superior efficiency in contrast to their monomeric oligo (phenylene vinylene) (OPV) counterparts. Scavenging experiments confirmed that photocatalysis proceeds via the generation of superoxide radicals (O
), singlet oxygen (
), and direct oxidation. The obtained results proved that the insertion of an aromatic rigid spacer not only prompts an enhancement in the photocatalytic activity of the phenylene vinylene-based polymers but also increases the stability of the OPV moiety by minimizing the reaction of the vinyl fragments with reactive oxygen species. This was demonstrated with the reuse experiments, where 96% of the photocatalytic activity was preserved throughout the first five reuse cycles.
