Subject:
All Disciplines Arts & Humanities Biology & Life Sciences Business & Economics Chemistry & Materials Science Computer Science & Mathematics Engineering Environmental & Earth Sciences Medicine & Pharmacology Physical Sciences Public Health & Healthcare Social Sciences
Sort:
Hottest Latest Alphabetical (A-Z) Alphabetical (Z-A)
Type:
All Topic Review Biography
Topic Review
Organic Binders in Archaeological Wall Paintings
Binding media are complex materials, employed to allow pigment grains to adhere to each other and to the surface of the support, through the formation of a coherent and homogeneous film. The function of the binder consists, therefore, in keeping the pigment particles firmly together and at the same time adhering them in the form of a coherent thin film to the surface of the support. The binder must obviously be in the fluid state, in order to form with the pigments a stable, homogeneous, stretchy, and viscous dough.   For the realization of wall paintings and, in later times, for their preservation, different materials with functions of binders, adhesives, paints, protective and consolidating were and are still necessary. There is a very large class of products which can have both constitutive functions but also a function of conservation and restoration. 
  • 1.7K
  • 21 Oct 2021
Topic Review
Shade Covers in Water Reservoirs
Shade objects are small plastic spheres, squares or even hexagons floating on top of a water reserve for environmental reasons. The creator of shade balls in California originally used them to prevent chemical treatments in the reservoir from reacting with sunlight creating bromate, which is a carcinogen regulated by many institutions worldwide (chlorine plus sunlight turns bromine into bromate that is a potentially cancer-causing agent; because shady objects stop bromate from forming below, less chlorine is required to treat the water than without them). More recently, other environmental issues have been associated to the use of shade objects: slowing down water evaporation, preventing algae blooms, avoiding birds landing on bodies of water and promote water heating.
  • 906
  • 21 Oct 2021
Topic Review
PEC Reactors for Water/Wastewater Treatment
Now and in the coming years, how we use and treat water, greywater and wastewater will become more important. A suitably designed photoelectrocatalytic (PEC) reactor is one potential solution. The photoexcitation of suitable semiconducting materials in aqueous environments can lead to the production of reactive oxygen species (ROS). ROS can inactivate microorganisms and degrade a range of chemical compounds. In the case of heterogeneous photocatalysis, semiconducting materials may suffer from fast recombination of electron–hole pairs and require post-treatment to separate the photocatalyst when a suspension system is used. To reduce recombination and improve the rate of degradation, an externally applied electrical bias can be used where the semiconducting material is immobilised onto an electrically conducive support and connected to a counter electrode. These electrochemically assisted photocatalytic systems have been termed “photoelectrocatalytic” (PEC). The term is stated in the IUPAC Recommendations 2011 as “electrochemically assisted photocatalysis. The role of the photocatalyst is played by a photoelectrode, often a semiconductor”. A short description of photocatalysis is included as it can be beneficial for those unfamiliar with the topic, before moving onto PEC. This entry is adapted from https://doi.org/10.3390/w13091198
  • 2.1K
  • 20 Oct 2021
Topic Review
Graphene Quantum Dots–Nanocellulose Composite
Graphene quantum dots (GQDs) are zero-dimensional carbon-based materials, while nanocellulose is a nanomaterial that can be derived from naturally occurring cellulose polymers or renewable biomass resources. The unique geometrical, biocompatible, and biodegradable properties of both these remarkable nanomaterials have caught the attention of the scientific community in terms of fundamental research to advanced technology. Studies have shown that the hybridisation of these novel materials not only improves existing applications but provides additional advantages as well as further improves desirable features, all of which are unattainable if GQDs and nanocellulose are used individually. Therefore, this advantageous composite material warrants remarkable applications. Potential applications for GQDs-nanocellulose composites include sensing or for analytical purposes, injectable 3D printing materials, supercapacitors, and light-emitting diodes. 
  • 717
  • 20 Oct 2021
Topic Review
Mechanical Milling
Mechanical milling (MM) has attracted great attention as a powerful tool for the synthesis of a variety of sophisticated materials, including equilibrium, nonequilibrium (e.g., amorphous, quasicrystals, nanodiamonds, carbon nanotubes, nanocrystalline powders), and nanocomposite materials. The MM is a unique process in that it involves a solid-state interaction between the reactant materials’ fresh powder surfaces at room temperature. As a result, it has been used to fabricate alloys and compounds that are difficult or impossible to acquire using standard melting and casting processes.
  • 2.3K
  • 20 Oct 2021
Topic Review
Silver Nanoparticle
Silver nanoparticles (AgNPs) are among the most commonly used engineered nanomaterials with medicinal, industrial, and agricultural applications. Considering the vast usage of AgNPs, there is a possibility of their release into the environment, and their potential toxicological effects on plants and animals. Apart from using the particulate form of silver, AgNPs may be transformed to silver oxide or silver sulfide via oxidation or sulfidation, respectively, and these ones impact the soil and living organisms in a variety of ways. Therefore, it is critical to address the behavior of nanoparticles in the environment and possible methods for their removal. This review focuses on three objectives to discuss this issue including: the possible pathways for the release of AgNPs into the environment; the toxicological effects of AgNPs on plants and microorganisms; and the recommended phytoremediation approaches.
  • 1.3K
  • 19 Oct 2021
Topic Review
Thermally Modified Wood Exposed to Different Weathering Conditions
Thermally modified wood (TMW) is a material derived from a treatment that combines temperature and moisture, avoiding harmful substances while providing better energy efficiency and drying quality. Such types of processes can considerably improve the performance of timber in several aspects. The treatment is usually achieved at temperatures between 120 °C and 260 °C, depending on the industrial process and desired end-product characteristics.
  • 631
  • 19 Oct 2021
Topic Review
Ti:Sa Crystals
In this paper, Ti:Sa amplifiers with crystals of the different geometries are discussed. Benefits of using this active medium for a thin disk (TD) and slab amplifiers are evaluated numerically and tested experimentally. Thermal management for amplifiers with multi-kW average power and multi-J pulse energy has been demonstrated. The presented numerical simulations revealed the existing limitations for heat extraction in TD geometry in the sub-joule energy regime for higher repetition rate operation. Geometry conversion from TD to thin-slab (TS) and cross-thin-slab (XTS) configurations significantly increases the cooling efficiency with an acceptable crystal temperature for pump average power values up to few kW with room temperature cooling, and up to tens of kW with cryogenic cooling. The abilities to attain 0.3 J output energy and a greater than 50% extraction efficiency were demonstrated with a repetition rate exceeding 10 kHz with room temperature cooling and one order more of a repetition rate with cryogenic conditions with pulsed pumping. Direct diode pumping simulated for CW regimes demonstrated 1.4 kW output power with 34% extraction efficiency using room temperature cooling and more than 10 kW and ~40% efficiency with cryogenic cooling.
  • 497
  • 19 Oct 2021
Topic Review
Oxidative Quality of Dairy Powders
Lipid oxidation (LO) is a primary cause of quality deterioration in fat-containing dairy powders and is often used as an estimation of a products shelf-life and consumer acceptability. The LO process produces numerous volatile organic compounds (VOC) including aldehydes, ketones and alcohols, which are known to contribute to the development of off-flavours in dairy powders. The main factors influencing the oxidative state of dairy powders and the various analytical techniques used to detect VOC as indicators of LO in dairy powders are outlined.
  • 751
  • 19 Oct 2021
Topic Review
Chemical Enzymology of Monoamine Oxidase
Monoamine oxidase (E.C. 1.4.3.4) enzymes MAO A and MAO B are FAD-containing proteins located on the outer face of the mitochondrial inner membrane, retained there by hydrophobic interactions and a transmembrane helix. The redox co-factor (FAD) is covalently attached to a cysteine and buried deep inside the protein behind an aromatic cage that aligns substrates towards the flavin. MAO metabolizes neurotransmitters such as dopamine and serotonin in the nervous system so is a target for drugs to modify amine levels. MAO also metabolizes a wide range of biogenic amines in all tissues. Current accumulated evidence, particularly from theoretical modelling, supports hydride transfer as the chemical mechanism. The long active site cavity accommodates a wide chemical variety of small molecules designed as inhibitors, including coumarins, chromones, triazoles, and more. Inactivators that bind covalently to MAO include hydrazines, cyclopropylamines and propargylamines. This entry is an extract adapted from a review outlining the remaining uncertainties in the understanding of this key drug target.
  • 1.2K
  • 19 Oct 2021
  • Page
  • of
  • 467
Featured Entry Collections
>>

Featured Books

>>
Encyclopedia of Social Sciences
Encyclopedia of COVID-19
Encyclopedia of Fungi
Encyclopedia of Digital Society, Industry 5.0 and Smart City
ScholarVision Creations
Feedback