Encyclopedia
Mesoporus silica nanoparticles-coated polyphenols and their localization.
06 Sep 2023
After having the yellow color, researchers add the salicylic acid which gives the purple color and researchers heat to 40°C and researchers add EDTA which gives the yellow color which means the presence of iron oxide.
25 May 2023
Diatomite: a 'water-like' substance
Water is only a tinny molecule but it results the most important chemical substance in the physical world. Such statement follows to the consideration that living matter excels in the physical world and it is made substantially of water (up to 75%), thus the transitive property suggests that water should excel in the physical world. Biomimetics is a new approach in material science, that consists in finding technological solutions by emulating the nature. Therefore, water-like solids should be substances with great technological potentialities. Hydroxyls (O-H) represent the only water fragment characterized by chemical/physical behaviors quite close to water. Owing to such huge similarity with water, hydroxyl-containing substances are important matter forms. Diatomite (hydrated silica, amorphous solid known as: opaline, SiO2.xH2O) is an inorganic chemical compound extremely rich of hydroxyl groups (i.e., silanols, Si-OH) and therefore this water-like substance should have a number of great technological potentialities.
01 Apr 2024
Escherichia coli (E. coli), Pseudomonas aeruginosa, and Staphylococcus aureus are three bacteria of significant importance in microbiology and healthcare. E. coli, a gram-negative bacterium, resides in the human intestine and serves as a model organism for genetic research. However, certain pathogenic strains can cause gastrointestinal and urinary tract infections. Pseudomonas aeruginosa, another gram-negative bacterium, is highly adaptable and often found in various environments. It poses a challenge due to its antibiotic resistance and causes opportunistic infections, particularly in immunocompromised individuals. Staphylococcus aureus, a gram-positive bacterium, inhabits the skin and mucous membranes and can lead to a range of infections, from skin issues to severe conditions like bloodstream infections. Understanding these bacteria is crucial for managing and preventing associated diseases, including antibiotic-resistant strains.
04 Sep 2023
Recently, the development of techniques to prepare and characterize carbon nano-materials has attract a great attention. In particular, low-density and porous exfoliated graphite is a widely investigated industrial product. Exfoliated graphite is generated as a result of an 'intermolecular explosion' during expandable graphite momentary heating, which causes the vaporization of water and some acid compounds, thus generating a dispersion pressure [1]. Exfoliated graphite according to XRD corresponds to graphite but it is represented by a number of chaotically located worm-like particles. Exfoliated graphite combines initial graphite properties with high specific area, porosity, low thermal conductivity, adsorption ability to various gasses and organic compounds, ability to be pressed without binder into materials with controlled density, gas permeability, etc. Exfoliated graphite is characterized by a X-ray density of 2.26 g/cm3 and a bulk density (determined as mass/volume ratio) of 1-10 g/l. Such difference in densities is caused by the high material porosity that varies from 95 to 98% with an estimated open pores of 98-99%. The exfoliated graphite porosity is represented by micro-, meso- and macropores, which determine its application areas. The production of graphite foils represents the most common use. These graphite foils are obtained simply by pressing the exfoliated graphite worm-like particles without binder; the obtained graphite-based product show perfect cohesion. Mesopores provides high sorption ability for heavy oils, while micropores makes exfoliated graphite a very promising material for hydrogen sorption. Indeed, exfoliated graphite adsorbs 0.11-0.25 wt. % under 1 bar of hydrogen at 77K.
12 Jan 2024
Artistic rendering of Cassava Mosaic Virus - graphic design on fabric in Guinea-Bissau.
William M. Brown Jr., Bugwood.org
01 Mar 2024
(A) The initiation of cell death through various pathways is contingent upon the location of the photosensitizer (PS) and the degree of organelle damage. Photodynamic therapy (PDT)-induced damage to mitochondria results in the loss of membrane permeability and the release of pro-apoptotic factors. Conversely, damage to the endoplasmic reticulum (ER) leads to the release of stored cellular calcium deposits. Furthermore, lysosomal damage results in the release of proteolytic enzymes upon illumination and can also trigger autophagy. In instances where apoptosis is impaired, necrosis and autophagy may emerge as the primary mechanisms of cell death following PDT. It is noteworthy that multiple PSs may localize in different organelles, potentially leading to the concurrent activation of multiple cell death pathways (adapted from Mroz, P et al. [1]).
(B) Photodynamic therapy has the capacity to induce vascular damage, disrupting the tumor's blood supply and causing its demise through various mechanisms.
(C) Photodynamic therapy can also activate innate and adaptive immunity, eliciting a systemic antitumor immune response and ultimately eradicating tumor cells.
06 Sep 2023
Artemisia herba alba, also known as "Desert Wormwood" or "White Sagebrush," is a medicinal plant native to North Africa, including Morocco. This remarkable herb has gained attention for its potential beneficial effects on various health conditions, including liver injury, diabetes, heart disease, and arthritis. With a long history of traditional use and ongoing scientific research, Moroccan Artemisia herba alba holds promise as a natural remedy for promoting overall well-being and managing these health concerns.
04 Sep 2023
Raccoons (Procyon lotor) are highly adaptable, nocturnal mammals native to North America, recognized by their distinctive black facial mask and ringed tail. These intelligent omnivores have a varied diet, including fruits, insects, and human garbage, and are known for their dexterous front paws. Raccoons thrive in diverse habitats, from forests to urban environments, demonstrating remarkable problem-solving abilities. They communicate through vocalizations and body language and exhibit both solitary and social behaviors. With stable populations, raccoons are classified as Least Concern by the IUCN, highlighting their successful adaptation to a range of ecological niches.
20 Jun 2024
The Temple of Bliss was built in 1923, covering an area of 53,500 square meters and a construction area of 3,000 square meters. It is divided into four parts: the main courtyard, the east cross-courtyard, the west cross-courtyard, and the tower courtyard. The gate of the hill is of the style of the archway. Into the gate, the east has the bell tower, the west has the drum tower, and the middle of the temple is the biggest hall - the Temple of Heaven.
13 Feb 2023
Possible mechanisms of action to induce prostate cancer eradication by targeting several pathways involving oxidative stress, cell death and cell cycle arrest.
[1]
07 Sep 2023
Transmission electron microscopy (TEM) micrograph of graphite oxide.
10 Nov 2023
Scanning electron microscopy (SEM) micrograph of graphite nanoplatelets (GNP) prepared by exfoliation of expanded graphite using ultrasound in liquid medium (acetone).
17 Jun 2024
Elemental iron nanoparticles can be chemically synthesized by using the spontaneous disproportion reaction of iron(II) in strongly-alkaline conditions, using ethylene glycol as reaction medium. Ethylene glycol not only protect iron particles from oxidation by air, but it also participates to the reduction process and therefore this chemical process is classified as a ‘polyol process’ [1]. The achieved high monodispersed nano-sized iron nanoparticles can be separated from the reaction medium by magnetic separation and then embedded into a protective polymeric matrix like for example amorphous polystyrene (the process is named ‘ex-situ synthesis’ of iron-polystyrene nanocomposites). In order to avoid the nanoparticle aggregation process, sonication is applied to the iron nanoparticles suspension in the polymer/organic solvent solution. These nanocomposite films are quite transparent in the visible spectral region and show super-paramagnetic properties, therefore they are adequate for magneto-optical applications.
13 Nov 2023
A DJI drone flying over a pistachio orchard in Castilla y León, Spain.
20 Feb 2023
Metal/polymer nanocomposites have a very long history and illustrious scientists have contributed this field [1]. The first technique for preparing a metal/polymer nanocomposite was developed by J. Erdmann in 1833. An aqueous gold salt was reduced in presence of gum-arabic and a nanocomposite material was obtained in form of a purple solid simply by co-precipitation with ethanol. Around 1900, many reports describe the preparation of metal-polymer nanocomposites with remarkable optical properties generated by uniaxially oriented inorganic particles. Dichroic plants and animal fibrils (e.g., linen, cotton, spruce, chitin) were impregnated with solutions of AgNO3, CH3COOAg, or gold chloride and then the contained metal ions were reduced by light. Dichroic films were also obtained using gold chloride-treated gelatin which was subsequently drawn, dried and finally exposed to light. Similar results were obtained when the gelatin was mixed with colloidal gold and then dried/drawn. In 1904, Kirchner and Zsigmondy (Nobel prize in Chemistry, 1925) reported about nanocomposites of colloidal gold and gelatin which reversibly changed the color from blue to red upon swelling with water. In the same period, the colors of nanocomposites based on gold particles was subject of a detailed theoretical analysis by Maxwell Garnett who explained the optical absorption shifts upon variation of particle size and volume fraction. During the following three decades, dichroic fibers were prepared with many other elements. Optical spectra of dichroic nanocomposites, made of stretched poly(vinyl alcohol) films, containing gold, silver or mercury, were presented in 1946. It was assumed already in the early reports that dichroism was originated by the linear arrangement of small particles or by polycrystalline rod-like particles located in the uniaxially oriented spaces present in the fibers. An electron micrograph depicted in 1951 showed as tellurium needles with typical dimensions of ca. 5x50nm were present inside a dichroic film made of stretched poly(vinyl alcohol). In the 1910, Kolbe was the first to prove that dichroic nanocomposite samples based on gold contained the metal in its zero-valence state. Such hypothesis was confirmed a few years later by X-ray diffraction, in particular it was shown that zero-valent silver and gold were present in the respective nanocomposites made with oriented ramie fibers. The Scherrer’s equation was developed just in this period and it was used to determine the average particle diameter of silver and gold crystallites in fibers of ramie, hemp, bamboo, silk, wool, viscose, and cellulose acetate which resulted between 5 and 14nm.
08 Mar 2024
This infographic is adapted from the paper: Diversity 2023, 15(11), 1139; https://doi.org/10.3390/d15111139
Birds are important features of the urban landscape, offering valuable ecosystem services, such as physiological and psychological stress reduction, aesthetic pleasure, and education. Knowing the populations of bird species in cities is important for their successful conservation. The normalized difference vegetation index (NDVI) is a remotely sensed metric used as a green cover proxy. We estimated the abundance of 15 bird species in the urban green spaces of Kavala, Greece, and calculated the NDVI at 19 survey stations with three different spatial scales: 50 m, 200 m, and 500 m circular buffers. NDVI was shown to significantly affect the abundance of 13 species. The 50 m buffer best predicted the abundance of 4 species, the 200 m buffer predicted 7 species, and the 500 m buffer predicted 4 species. Abundance decreased with NDVI for 9 species (urban dwellers) and increased for 6 species (urban utilizers). These findings suggest that NDVI is a reliable predictor of the abundance of bird species in urban areas. More importantly, bird abundance and NDVI associations can be better described if determined at various spatial scales. These findings could be used for the prediction and monitoring of urban bird species populations and incorporated into urban conservation management plans.
Encyclopedia Editorial Office
25 Sep 2024
Graphene is the most famous two-dimensional (2D) nanomaterial [1]. It has a flexible structure and consequently is used in a supported or embedded form. Non-polar polymeric films represent a very convenient substrate type. Owing to the very high affinity between graphene and polyethylene (e.g., low-density polyethylene, LDPE), due to the possibility to form CH-π interactions between them, that are stronger than the π-π bonds present in graphite crystal, graphite nanoplatelets (i.e., small graphite crystals) can spontaneously spread on the surface of a LDPE foil under the effect of a shear stress (friction), forming a thin graphene layer. Such thin coating layer transforms the dielectric surface of this polymer to an electrical conductor. In addition, the coated film is semitransparent, indeed it partially reflect and transmit light. Polydimethylsiloxane (PDMA) is a further very good example of polymeric substrate for these micromechanically fabricated graphene layer (i.e., coatings generated by spreading of graphite nanoplatelets against a non-polar polymer surface).
13 Nov 2023
The scheme of synthesis СoFe2O4/Au nanoparticles. Magnetic CoFe2O4/Au HNPs with an average particle size of 20 nm, decorated with 2 nm gold clusters, were prepared using methionine as a reducer and an anchor between CoFe2O4 and gold. The methionine was used to grow the Au clusters to a solid gold shell (up to 10 gold deposition cycles).
10 Jul 2023
