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Topic Review
Usul Fiqh in Ja'fari School
Ja'fari principles (Persian: علم اصول در مکتب جعفری‎) refers to regulations, history and eminent persons and scholars during the development of Shia's Principles of Islamic jurisprudence.
  • 3.8K
  • 28 Oct 2022
Topic Review
Sonic Hedgehog
Sonic hedgehog is a protein encoded for by the SHH gene. The protein is named after the character Sonic the Hedgehog. This signaling molecule is key in regulating embryonic morphogenesis in all different types of animals. SHH controls organogenesis and the organization of the central nervous system, limbs, digits and many other parts of the body. Sonic hedgehog is a morphogen that patterns the developing embryo using a concentration gradient characterized by the French Flag model. This model has a non-uniform distribution of SHH molecules which governs different cell fates according to concentration. Mutations in this gene can cause holoprosencephaly, a failure of splitting in the cerebral hemispheres, as demonstrated in an experiment using SHH knock-out mice in which the forebrain midline failed to develop and instead only a single fused telencephalic vesicle resulted. Sonic hedgehog still plays a role in differentiation, proliferation, and maintenance of adult tissues. Abnormal activation of SHH signaling in adult tissues has been implicated in various types of cancers including breast, skin, brain, liver, gallbladder and many more.
  • 3.8K
  • 21 Nov 2022
Topic Review
Aerial Photography
Aerial photography (or airborne imagery) is the taking of photographs from an aircraft or other flying object. Platforms for aerial photography include fixed-wing aircraft, helicopters, unmanned aerial vehicles (UAVs or "drones"), balloons, blimps and dirigibles, rockets, pigeons, kites, parachutes, stand-alone telescoping and vehicle-mounted poles. Mounted cameras may be triggered remotely or automatically; hand-held photographs may be taken by a photographer. Aerial photography should not be confused with air-to-air photography, where one or more aircraft are used as chase planes that "chase" and photograph other aircraft in flight.
  • 3.7K
  • 30 Nov 2022
Topic Review
Chemical Composition of Kombucha
Kombucha is a fermented sweetened tea with a mixed fermenting culture of yeast and acetic acid bacteria. The proponents of kombucha consumption tout the varied health benefits it can provide. The final kombucha flavor and composition is a function of both the initial tea used and the fermentation process.
  • 3.7K
  • 29 Aug 2022
Topic Review
Urban Horticulture for Food Security
Sufficient production, consistent food supply, and environmental protection in urban +settings are major global concerns for future sustainable cities. Currently, sustainable food supply is under intense pressure due to exponential population growth, expanding urban dwellings, climate change, and limited natural resources. The recent novel coronavirus 2019 (COVID-19) pandemic crisis has impacted sustainable fresh food supply and has disrupted the food supply chain and prices significantly. Under these circumstances, urban horticulture and crop cultivation have emerged as potential ways to expand to new locations through urban green infrastructure. Therefore, the objective of this study is to review the salient features of contemporary urban horticulture, in addition to illustrating traditional and innovative developments occurring in urban environments. Current urban cropping systems, such as home gardening, community gardens, edible landscape, and indoor planting systems, can be enhanced with new techniques, such as vertical gardening, hydroponics, aeroponics, aquaponics, and rooftop gardening. These modern techniques are eco-friendly, energy-saving, and promise food security through steady supplies of fresh fruits and vegetables to urban neighborhoods. There is a need, in this modern era, to integrate information technology tools in urban horticulture, which could help in maintaining consistent food supply during (and after) a pandemic, as well as make agriculture more sustainable.
  • 3.7K
  • 04 Dec 2020
Topic Review
Laser-Induced Breakdown Spectroscopy
Laser-Induced Breakdown Spectroscopy (LIBS) has been firstly introduced and proposed for analytical applications almost immediately after the invention of the laser in 1960. Since then, it has been proposed and today is widely used as an alternative analytical method for numerous applications. The operating principle of LIBS is quite simple and is based on the interaction of a powerful enough laser beam, focused usually on or in a sample, inducing a dielectric breakdown of the material, thus resulting in plasma formation consisting of excited and non-excited atoms and molecules, fragments of molecular species, electrons and ions, and emitting characteristic radiations, whose spectroscopic analysis can in principle provide the elemental composition fingerprint of the material. The required instrumentation consisting basically of a laser source, and a spectrometer/monochromator equipped with the appropriate light detector (nowadays being almost exclusively some CCD or ICCD type detector) is relatively simple and economically affordable, while significant progresses have been achieved to small size and/or portable equipment, facilitating largely the in situ operation.
  • 3.7K
  • 31 Aug 2021
Topic Review
Metabolic Equivalent
The Metabolic Equivalent of Task (MET), or simply metabolic equivalent, is a physiological measure expressing the energy cost of physical activities and is defined as the ratio of metabolic rate (and therefore the rate of energy consumption) during a specific physical activity to a reference metabolic rate, set by convention to 3.5 ml O2·kg−1·min−1 or approximately: [math]\displaystyle{ \text{1 MET}\ = 1 \dfrac{\text{kcal}}{\text{kg}*\text{h}}\ = 4.184 \dfrac{\text{kJ}}{\text{kg}*\text{h}} = 1.1622222... \dfrac{\text{W}}{\text{kg}} }[/math] Still another definition of 1 MET is 58.2 W/m2 (18.4 Btu/h·ft2), which is equal to the rate of energy produced per unit surface area of an average person seated at rest. The surface area of an average person is 1.8 m2 (19 ft2). Metabolic rate is usually expressed in terms of unit area of the total body surface (ANSI/ASHRAE Standard 55). Originally, 1 MET was considered as the Resting Metabolic Rate (RMR) obtained during quiet sitting. MET values of activities range from 0.9 (sleeping) to 23 (running at 22.5 km/h or a 4:17 mile pace). Although the RMR of any person may deviate from the reference value, MET can be thought of as an index of the intensity of activities: for example, an activity with a MET value of 2, such as walking at a slow pace (e.g., 3 km/h) would require twice the energy that an average person consumes at rest (e.g., sitting quietly). MET is used as a means of expressing the intensity and energy expenditure of activities in a way comparable among persons of different weight. Actual energy expenditure (e.g., in calories or joules) during an activity depends on the person's body mass; therefore, the energy cost of the same activity will be different for persons of different weight. However, since the RMR is also dependent on body mass in a similar way, it is assumed that the ratio of this energy cost to the RMR of each person will remain more or less stable for the specific activity and thus independent of each person's weight. The 1 MET reference value of 1 kcal·kg−1·h−1, is used by convention and refers to a typical metabolism at rest of an "average" individual. It is not an approximation of Basal Metabolic Rate (BMR), which is the minimum metabolic rate obtained under specified conditions. This is illustrated by sleeping having a MET of 0.9, while an individual's normal sleeping metabolism may be greater than the BMR.
  • 3.7K
  • 14 Oct 2022
Topic Review
Aryl-hydrocarbon Receptor
The aryl-hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates numerous cellular responses. Originally investigated in toxicology because of its ability to bind environmental contaminants, AhR has attracted enormous attention in the field of immunology in the last 20 years. In addition, the discovery of endogenous and plant-derived ligands points to AhR also having a crucial role in normal cell physiology. Thus, AhR is emerging as a promiscuous receptor that can mediate either toxic or physiologic effects upon sensing multiple exogenous and endogenous molecules. Within this scenario, several factors appear to contribute to the outcome of gene transcriptional regulation by AhR, including the nature of the ligand as such and its further metabolism by AhR-induced enzymes, the local tissue microenvironment, and the presence of coregulators or specific transcription factors in the cell.
  • 3.7K
  • 07 Dec 2021
Topic Review Peer Reviewed
Asexual Epichloë Fungi—Obligate Mutualists
Asexual Epichloë are obligate fungal mutualists that form symbiosis with many temperate grass species, providing several advantages to the host. These advantages include protection against vertebrate and invertebrate herbivores (i.e., grazing livestock and invertebrate pests, respectively), improved resistance to phytopathogens, increased adaptation to drought stress, nutrient deficiency, and heavy metal-containing soils. Selected Epichloë strains are utilised in agriculture mainly for their pest resistance traits, which are moderated via the production of Epichloë-derived secondary metabolites. For pastoral agriculture, the use of these endophyte infected grasses requires the balancing of protection against insect pests with reduced impacts on animal health and welfare.
  • 3.7K
  • 13 Apr 2022
Topic Review
European Hedgehog (Erinaceus Europaeus): Sentinel
Erinaceus europaeus is a cosmopolitan mammalian species broadly distributed in Europe, from natural to suburban areas. Due to its ecological role and susceptibility to distinct zoonotic agents, E. europaeus could be a suitable sentinel candidate for many global problems that negatively affect human and animal health. Hedgehogs can work as bioindicators to environmental contamination and can be hosts for multiple tickborne zoonotic agents. 
  • 3.7K
  • 04 Jul 2022
Topic Review
The Swampland Distance Conjecture
The Swampland Distance Conjecture (SDC) is one of the most studied and well-established Swampland Conjetures, and it introduces an omnipresent feature in effective field theories (EFTs) of quantum gravity, namely the appearance of infinite towers of states that become light an imply a breakdown of the EFT in the infinite distance limits in moduli space. In this entry we present the conjecture, a simple example and some comments on relations to other conjectures.
  • 3.7K
  • 18 Aug 2021
Topic Review
Surface-Functionalized Nanoparticles for Bio-Application
Surface functionalization of nanoparticles applies to the use of covalent and non-covalent bonds—such as hydrogen bonds, electrostatic force, and the van der Waals interactions—to integrate diverse organic and inorganic molecules at the nanoscale. Typically, multiple linker molecules are used to form covalent bonds between ligands and the surfaces of nanoparticles (NPs).
  • 3.7K
  • 20 Apr 2022
Topic Review
Secure Shell Protocol
The Secure Shell Protocol (SSH) is a cryptographic network protocol for operating network services securely over an unsecured network. Typical applications include remote command-line, login, and remote command execution, but any network service can be secured with SSH. SSH provides a secure channel over an unsecured network by using a client–server architecture, connecting an SSH client application with an SSH server. The protocol specification distinguishes between two major versions, referred to as SSH-1 and SSH-2. The standard TCP port for SSH is 22. SSH is generally used to access Unix-like operating systems, but it can also be used on Microsoft Windows. Windows 10 uses OpenSSH as its default SSH client and SSH server. SSH was designed as a replacement for Telnet and for unsecured remote shell protocols such as the Berkeley rsh and the related rlogin and rexec protocols. Those protocols send information, notably passwords, in plaintext, rendering them susceptible to interception and disclosure using packet analysis. The encryption used by SSH is intended to provide confidentiality and integrity of data over an unsecured network, such as the Internet.
  • 3.7K
  • 29 Sep 2022
Topic Review
Collagen in Wound Healing
Collagens are the most abundant protein found throughout the body. In the healing wound, these collagens are synthesized by cells such as fibroblasts and modified into complex morphologies . The type, amount and organization of collagen changes in the healing wound and determines the tensile strength of the healed skin. Collagen III is the first to be synthesized in the early stages of wound healing and is replaced by collagen I, the dominant skin collagen. The initial random deposition of collagen during the granulation tissue formation is further enhanced by lysyl oxidase enzyme-induced covalent cross-linking. This process matures the collagen into complex structures that are reoriented for tensile strength restoration. Collagen remodeling continues for months after wound closure and the tensile strength of the repaired tissue increases to about 80–85% of normal tissue if all processes proceed without any perturbations.In the skin, the fibrillar collagens types I, III and V are the most common, followed by fibril-associated collagens type XII, XIV, XVI, and VI. The non-fibrillar collagens type IV, XVIII are found in the basement membrane of the skin
  • 3.7K
  • 23 Jun 2021
Topic Review
Single-Speed Bicycle
A single-speed bicycle is a type of bicycle with a single gear ratio. These bicycles are without derailleur gears, hub gearing or other methods for varying the gear ratio of the bicycle. There are many types of modern single speed bicycles; BMX bicycles, most bicycles designed for children, cruiser type bicycles, classic commuter bicycles, unicycles, bicycles designed for track racing, fixed-gear road bicycles, and single-speed mountain and cyclocross bikes. Although most fixed-gear bicycles (fixies) are technically single speed, the term single-speed generally refers to a single gear ratio bicycle with a freewheel mechanism to allow it to coast.
  • 3.7K
  • 20 Oct 2022
Topic Review
Climate Change Education in Finland
The climate change education (CCE) is understood as a component of environmental education and education for sustainable development. Its core concept is CC literacy, which means that students understand the scientific concepts related to CC and the relationships between them, as well as the effects of CC and their own activities on the environment. CCE is multidisciplinary and interdisciplinary. Multidisciplinarity means that knowledge of various individual sciences is needed. Interdisciplinarity, on the other hand, incorporates elements from a variety of disciplines and also integrates environmental, economic, social and political issues.
  • 3.7K
  • 30 Mar 2022
Topic Review
Choleretic and Cholagogic Effects of Anticholelithiatic Plants
A large number of people suffer from gall stone worldwide and this problem is now being increased significantly due to the malnutrition, changes in living style, lack of exercise and conditions i.e. industrialization. Medicinal plants are used from centuries due to their cultural acceptability, efficacy, safety and fewer side effects as compared to modern synthetic medicines.
  • 3.7K
  • 15 Aug 2022
Topic Review Peer Reviewed
Molecular Aspects of Spike–ACE2 Interaction
A new betacoronavirus (CoV-2) is responsible for the pandemic of severe acute respiratory syndrome (SARS) that began in China at the end of 2019, today known as COronaVIrus Disease 2019 (COVID-19). Subsequent studies confirmed the human angiotensin-converting enzyme 2 (hACE2) as the main cell receptor of spike trimeric glycoprotein, located on the viral envelope, mediating the CoV-2 invasion into the host cells through the receptor-binding domain (RBD) of the spike. Computational analysis of the known experimental 3D structures of spike–ACE2 complexes evidenced distinguishing features in the molecular interactions at the RBD-cell receptor binding interface between CoV-2 and previous CoV-1. The spike represents a key target for drug design as well as an optimal antigen for RNA/viral vector vaccines and monoclonal antibodies in order to maximize prevention and therapy of COVID-19.
  • 3.7K
  • 13 Apr 2022
Topic Review
Historia Animalium (Gessner)
Historia animalium ("History of the Animals"), published at Zurich in 1551–58 and 1587, is an encyclopedic "inventory of renaissance zoology" by Conrad Gessner (1516–1565). Gessner was a medical doctor and professor at the Carolinum in Zürich, the precursor of the University of Zurich. The Historia animalium is the first modern zoological work that attempts to describe all the animals known, and the first bibliography of natural history writings. The five volumes of natural history of animals cover more than 4500 pages.
  • 3.7K
  • 22 Nov 2022
Topic Review
Class D Audio Power Amplifier
Class D power amplifiers, one of the most critical devices for application in sound systems, face severe challenges due to the increasing requirement of smartphones, digital television, digital sound, and other terminals. The audio power amplifier has developed from a transistor amplifier to a field-effect tube amplifier, and digital amplifiers have made significant progress in circuit technology, components, and ideological understanding. The stumbling blocks for a successful power amplifier are low power efficiency and a high distortion rate.
  • 3.7K
  • 01 Nov 2022
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