Encyclopedia
Scanning electron microscopy (SEM) micrograph of micrometric diatomite fragments prepared by ball milling technology.
29 Nov 2023
The graphite oxide (GO) sample has been generated by the well-known Hummers’ method, that is a chemical reaction based on the oxidation of graphite flakes by a solution of potassium permanganate (KMnO4) and sodium nitrate (NaNO3) in absolute sulfuric acid (oleum, H2SO4). Graphite oxide is a very useful chemical compound since it is the precursor of single-layer graphene; indeed, it is an unstable compound that spontaneously decomposes with time or can be very easily reduced by heating or by treatment with a mild chemical reluctant (e.g., ascorbic acid). The obtained thermally/chemically reduced graphene oxide has a number of structural defects due to the presence of residual oxygen-containing groups (epoxies) and holes in the graphene plane structure. While GO is a non-electrically conductive nanostructure because electron conjugation is interrupt for the presence of a large amount of oxygen-containing groups (hydroxyls, carboxylic groups, epoxies, etc.), the thermally/chemically reduced graphene oxide is a good electrical conductor, that is useful for different technological applications [1].
13 Nov 2023
Scanning electron microscopy (SEM) micrograph of graphite bisulfate.
06 Dec 2023
This infographic is adapted from the paper: Encyclopedia 2024, 4(2), 720-734; https://doi.org/10.3390/encyclopedia4020045
Following the WHO definition, pesticides are chemical compounds used to kill pests, including insects, rodents, fungi, and unwanted plants. They are contemporary cultural artefacts that social sciences explore in synergy with other disciplines to highlight their socio-cultural connections at both local and global levels. Specifically, the use of these products is connected with power relations, which are embedded in and reflect imbalances and inequalities in access to rights and resources, as well as specific articulation of the perception of risk arising from environmental contamination in terms of individual and collective psychophysical health. Furthermore, pesticides fit into various environmental conceptions and multiple local knowledge systems, representing the intersection of different cultural heritages, worldviews, and rationales that make the tradition–modernity dichotomy complex and dynamic. In this respect, therefore, pesticides can be understood not just as mere tools for agricultural practice but as vital windows through which to investigate multiple layers of meaning to support transitions towards sustainable pest management systems, both environmentally and socio-culturally.
Encyclopedia Editorial Office
25 Sep 2024
Under the electron microscope, a capillary reveals red blood cells transporting oxygen and white blood cells engaged in immune surveillance. The vessel's thin walls and endothelial cells facilitate nutrient exchange, highlighting its vital role in circulation and immune defense
05 Jul 2024
Gold nano-crystals are very beautiful nanostructures. How could it be explained? The beauty of a shape is directly proportional to the number of contained symmetry elements. Higher is the number of symmetry elements, more beautiful results that shape. Triangles are not beautiful in the same measure. Gold nano-crystals are shaped as 'equilateral triangles', these particular triangle has the maximum number of symmetry elements (i.e., 4 symmetry planes and 4 symmetry axes) that are possible for the triangular geometry and therefore they are the most beautiful gold nano-crystals. Type and number of contained symmetry elements remain practically unchanged if the triangle has three rounded or truncated corners.
18 Dec 2023
Magnified 400x, grains of sand from a beach in Maui, Hawaii, reveal a stunning diversity of shapes, colors, and textures. Unlike the uniform appearance seen with the naked eye, each grain is unique, reflecting the complex geological history of the island. Some grains are clear or translucent, likely composed of quartz, while others may be pink, red, or black, indicating the presence of coral fragments, volcanic basalt, or minerals like garnet. The sand grains are often irregular in shape, with smooth, rounded edges from continuous weathering by waves and wind. Some may appear more angular, particularly those formed from recently broken coral or volcanic rock. At this magnification, you can also see tiny inclusions, striations, and surface pitting on the grains, all of which contribute to the rich, detailed mosaic of colors and textures that characterize Maui's beaches. This microscopic view highlights the beauty and complexity of sand, turning each grain into a miniature geological specimen.
09 Aug 2024
This is a picture about TRANSCYTOSIS LPS MODEL.
04 Jul 2023
Giraffes, with their distinctive long necks and towering presence, are remarkable creatures that captivate both scientists and nature enthusiasts alike. These majestic herbivores are the tallest land animals on Earth, with adult males reaching heights of up to 18 feet (5.5 meters) and females slightly shorter. Their impressive necks, which can measure up to 6 feet (1.8 meters) long and contain only seven vertebrae (the same number as humans), are not only essential for reaching high branches but also serve as powerful weapons in male dominance battles known as "necking." Despite their height and long legs, giraffes move gracefully, thanks to their unique walking pattern — moving both legs on one side of the body simultaneously, a gait known as pacing. Their distinctive coat pattern, with irregular patches of brown spots on a buff-colored background, acts as effective camouflage in their natural habitats, primarily the savannas and open woodlands of sub-Saharan Africa. Giraffes are also notable for their prehensile tongues, which can extend up to 18 inches (45 centimeters) and are adept at plucking leaves from high branches. These gentle giants are herbivores, feeding primarily on leaves, buds, and shoots, and spend most of their day browsing for food. Despite their size and strength, giraffes are surprisingly vulnerable to habitat loss, poaching, and disease, making conservation efforts crucial to ensuring their continued existence in the wild.
24 Jun 2024
Altered mitostasis in amyotrophic lateral sclerosis (ALS)-affected cells can contribute to degeneration of motor neurons, reactive gliosis, muscle atrophy, and damage to other peripheral tissues. The misfolding, aggregation, and increasing accumulation of toxic proteins may contribute to their transfer to the mitochondria, which makes their dysfunction one of the early pathological signs of ALS. Mutant SOD1, C9orf72, FUS, TDP-43, and other proteins can be located on the cytoplasmic surface or within mitochondria. Characteristics of mitochondrial dyshomeostasis are changes in the number and distribution of mitochondria in cells; deep ultrastructural abnormalities of organelles; impaired mitochondrial dynamics, biogenesis, axonal transport and mitophagy; de-creased activity of mitochondrial electron transport chain (ETC) complexes and tricarboxylic acid (TCA) cycle enzymes; decreased ATP synthesis and NAD(P)H level; the decreased threshold of the mPTP opening; excessive ROS formation; etc. Abnormalities in the mitochondrial network can finally result in bioenergetic crisis and the initiation of cell death signals [1].
19 Dec 2023
The biogenic origin of diatomite clearly appears at the microscopical investigation performed by scanning electron microscopy (SEM). As visible in the SEM micrograph, the sample mostly consists of variously shaped frustule fragments but entire skeletal diatoms algae with well-preserved shapes are also present. Diatomite sizes are ranging from 5 to 15μm and pores diameters varies between 150 and 600 nm. Frequently, other mineral forms (e.g., clay) are also present in diatomaceous earth samples.
15 Jan 2024
This image highlights the importance of bioinputs in sustainable agriculture. Derived from microbial sources, these alternatives to synthetic chemicals offer eco-friendly solutions, potentially reducing the environmental impact of food production. Bioinputs positively impact human health by mitigating soil pollution and water contamination. Advanced techniques such as Next-Generation Sequencing enable standardized global approaches to identify microorganisms and associated risks. Regulatory authorities ensure the safety and efficacy of bioinputs production, fostering a balance between safety and innovation for sustainable agriculture.
03 Apr 2024
Nature uses the 'evolution mechanism' for modifying, improving and refining the own creatures. It is an adaptation process for all living species, that acts by favoring the life of those types of organisms that are more adequate to some specific external conditions. This natural selection process takes millions of years to complete, but at the end it makes possible to achieve by progressive mutations an ideal form of living machine. It is possible to exploit this powerful natural mechanism for the human technologies simply by miming the most perfect living solutions the nature has progressively built. During the story of technology, this approach has been frequently used. For example, the complex shapes that nature is capable to create can find a number of technological applications; indeed, Alfred Bernhard Nobel in the 1867 used the regular array of micro-pores present in the fossil diatom frustules to stabilize the highly reactive and therefore dangerous nitroglycerine product discovered by the Italian physician Ascanio Sobrero in the 1847, obtaining an extremely useful explosive substance named dynamite. Successively many artificial microporous substances, miming the diatomite, have been developed and used for the same purpose. Many other geometrical characteristics of the natural surfaces (e.g., super-hydrophobic and water-repellant surfaces) can be similarly copied and transferred to the human technologies and this special approach of materials science is named Biomimetics.
27 Dec 2023
Scanning electron microscopy (SEM) micrograph showing the structure of a silver aerogel sample obtained by thermal decomposition in air (combustion) of silver nanoparticles dispersed in poly(vinylpyrrolidone) (PVP) [1].
27 May 2024
Nanostructure preparation: which way to follow? Formally, two different preparative schemes are available to produce nanostructures and they are named: ‘top-down’ and ‘bottom-up’ approaches[1]. These approaches are typically considered as equivalent, however they are not since only the ‘bottom-up’ approach is really capable to give nanostructures. How could be the reason for that? A first consideration is based on the difference between the precursor and nanoscopic solid sizes: owing to the very small size of nanostructures (i.e., nanometric size, as their name suggests) the ‘bottom-up’ way is much shorter than the ‘top-down’ way. Atoms are dimensionally very close to nanostructures, only two magnitude orders separate their dimensional scales (from angstrom, 10-10, to nanometers, 10-9); indeed, nanostructures are categorized as supramolecular systems. Differently, more than six magnitude orders separate the nanostructures dimensional scale from the precursor-solid dimension (e.g., from millimeters, 10-3, to nanometers, 10-9). Consequently, the ‘bottom-up’ approach is the most immediate way to nanostructures and therefore the most convenient to use. For example, for synthesizing an ester molecule is it better to condensate an acid with an alcohol molecule (Fischer esterification reaction) or to use a partial alkaline-hydrolysis of a polyester (de-polymerization reaction)? A second consideration is based on thermodynamics: particle formation by the ‘bottom-up’ approach is a spontaneous phenomenon; indeed, nucleation and growth take place spontaneously[2] because the Gibbs’ free energy (G) of the system lowers going from atoms/molecules to clusters and then to nanoparticles. Differently, G increases in the ‘top-down’ process because the surface free energy contribution is higher for the smaller particles and a comminution process can even be forbidden below a certain size limit. Finally, the ‘bottom-up’ approach is the only really effective scheme for producing nanostructures like that shown in the above picture (gold nanocrystals embedded in PVP).
22 May 2024
In 2017, our group won a gold medal in the Invention, Innovation, and Design Exhibition (IIDEX) in Malaysia for our novel treatment system designed to treat kenaf wastewater.
28 Jun 2023
The sustainability approach to materials science imposes to exploit widely available natural sources of materials for solving technological problems. In the application of natural substances a first important aspect is represented by their identification and chemical characterization, finalized to establish the exact qualitative/quantitative composition and to quantify the contained impurities. Natural materials composition changes significantly with the place (e.g., the mine) where they have been extracted. There are several spectroscopic techniques that can be potentially used for such a purpose (XPS, XRF, EDS, ESCA, etc.), however energy dispersive X-ray spectroscopy (EDS) represents the most convenient one. For example, each deposit of diatomaceous earth is characterized by a different chemical composition, since various blends of pure diatomaceous earth, natural clays and other minerals are possible. The diatoms in each deposit contain different amounts of silica, depending on the sedimentation conditions, on the presence of other sediments (clay, sand, volcanic ashes) and on the age of the deposit (diagenesis, silica dissolution/precipitation, diatoms aging, etc.). The species of diatoms may also differ among deposits. In terms of chemical composition there are major, secondary and minor constituents in diatomite. The major component always is hydrated silica (hydrated silicon dioxide, SiO2.nH2O), whereas alumina (Al2O3), lime (CaO), and iron oxide (Fe2O3) are considered as secondary, while as minor components there are: Na2O, SO3, TiO2, MnO2 and other components. The content of the major component as well as the secondary and other minor component varies and it is different in every deposit due to its nature of formation and the environment. Besides the major, the secondary and the minor elements, present in diatomite there could be various heavy metals as impurities as well as rare elements. The economic importance of certain diatomite deposits is determined based on the ratios of these various components. The higher the amount of silica present in diatomite, the higher its quality from the economical perspective. The typical chemical composition of an oven-dried diatomaceous earth sample obtained by EDS is ca. 80% by weight of SiO2.nH2O, ca. 4% by weight of Al2O3, attributed mostly to clay minerals, and ca. 2% by weight of Fe2O3; little amounts of other inorganic compounds like TiO2, MgO, CaO, K2O, etc. are also present.
16 Jan 2024
Therapeutic approaches for colorectal cancer, with conventional treatment (i.e., surgery, radiation, hormone therapy, targeted therapy, and chemotherapy), as well as the use of flavonoids, tannins, and non-flavonoids in colorectal cancer treatment [1].
06 Sep 2023
The manufacturing of graphite-based gaskets or other types of mechanical components with a complex shape is based on the use graphite bisulfate. Graphite bisulfate is an intercalation compound, prepared by reacting graphite flakes with a mixture of concentrated nitric acid (HNO3, 68%) and absolute sulfuric acid (H2SO4). This reaction was developed by Brodie in the 1855. At high temperatures, the sulfuric acid molecules located between the graphite bisulfate sheets react with the carbon atoms in the sheets to produce a gaseous mixture of molecules (CO2, SO2 and H2O), that causes a very violent expansion of the graphite lattice with formation of low-density graphite filaments. This material, named expanded graphite, can be compacted by pressing to generate the graphite component. Expanded graphite generates by sonication in liquids (e.g., acetone) many other graphite derivates, like graphite nanoplatelets (GNP), few-layer graphene, single-layer graphene, etc.
27 Nov 2023
Scanning electron microscopy (SEM) micrograph of graphite bisulfate after the thermal expansion process.
07 Nov 2023
