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Topic Review
Dialysis (Biochemistry)
In biochemistry, dialysis is the process of separating molecules in solution by the difference in their rates of diffusion through a semipermeable membrane, such as dialysis tubing. Dialysis is a common laboratory technique that operates on the same principle as medical dialysis. In the context of life science research, the most common application of dialysis is for the removal of unwanted small molecules such as salts, reducing agents, or dyes from larger macromolecules such as proteins, DNA, or polysaccharides. Dialysis is also commonly used for buffer exchange and drug binding studies. The concept of dialysis was introduced in 1861 by the Scottish chemist Thomas Graham. He used this technique to separate sucrose (small molecule) and gum Arabic solutes (large molecule) in aqueous solution. He called the diffusible solutes crystalloids and those that would not pass the membrane colloids. From this concept dialysis can be defined as a spontaneous separation process of suspended colloidal particles from dissolved ions or molecules of small dimensions through a semi permeable membrane. Most common dialysis membrane are made of cellulose, modified cellulose or synthetic polymer (cellulose acetate or nitrocellulose).
  • 9.0K
  • 07 Nov 2022
Topic Review
Misogyny in Horror Films
Misogyny can occur in horror films when there is a degrading representation of women. This is found particularly in slasher films, where there is often gendered specific violence towards women. Female characters experience violence and brutality at the hands of male antagonists far more often than male characters in these films. Female characters are likely to experience sexual violence, particularly in the rape-and-revenge subgenre.
  • 9.0K
  • 28 Nov 2022
Topic Review
Doubling Time
The doubling time is time it takes for a population to double in size/value. It is applied to population growth, inflation, resource extraction, consumption of goods, compound interest, the volume of malignant tumours, and many other things that tend to grow over time. When the relative growth rate (not the absolute growth rate) is constant, the quantity undergoes exponential growth and has a constant doubling time or period, which can be calculated directly from the growth rate. This time can be calculated by dividing the natural logarithm of 2 by the exponent of growth, or approximated by dividing 70 by the percentage growth rate (more roughly but roundly, dividing 72; see the rule of 72 for details and derivatiatives of this formula). The doubling time is a characteristic unit (a natural unit of scale) for the exponential growth equation, and its converse for exponential decay is the half-life. For example, given Canada's net population growth of 0.9% in the year 2006, dividing 70 by 0.9 gives an approximate doubling time of 78 years. Thus if the growth rate remains constant, Canada's population would double from its 2006 figure of 33 million to 66 million by 2084.
  • 9.0K
  • 28 Nov 2022
Topic Review
Agricultural Expansion Drivers and Constraints
Agricultural expansion refers to the conversion of uncultivated land, including natural forests, woodlands, grasslands and wetlands into crop or grazing land, and may be undertaken by smallholders or largescale farmers. 
  • 9.0K
  • 30 Apr 2021
Topic Review
Unmanned Systems
An Unmanned System (US) or Vehicle (UV) can be defined as an “electro-mechanical system, with no human operator aboard, that is able to exert its power to perform designed missions”
  • 9.0K
  • 17 Mar 2021
Topic Review
Underwater Wireless Sensor Networks
The underwater wireless sensor network (UWSN) is a network used to perform monitoring of tasks over a specific region; it is equipped with smart sensors and vehicles that are adapted to communicate cooperatively through wireless connections [1]. The surface sink retrieves the data from sensor nodes. The sink node has a transceiver that can control acoustic signals received from underwater nodes. The transceiver also can transmit and receive long-range radio frequency signals for communication with the onshore station. The collected data are used locally or connected to another network for a particular purpose [2].
  • 8.9K
  • 26 Oct 2020
Topic Review
Burden of Proof
The burden of proof (Latin: onus probandi, shortened from Onus probandi incumbit ei qui dicit, non ei qui negat) is the obligation on a party in a dispute to provide sufficient warrant for its position.
  • 9.0K
  • 25 Nov 2022
Topic Review
Monochromatic X-rays
Monochromatic X-ray has a single energy level in contrast to white X-rays used in conventional radiation therapy. Irradiation of high Z elements such as gadolinium, gold and silver with a monochromatic X-ray can result in photoelectric effects that includes the release of the Auger electrons that have strong cell killing effect. To apply this principle to cancer therapy, various nanoparticles loaded with high Z elements have been developed that enabled high Z elements to be delivered to tumor. The recent addition is gadolinium-loaded mesoporous silica nanoparticle (Gd-MSN). Tumor spheroids have been used as a convenient tumor model to demonstrate that monochromatic X-rays with energy level at or higher than the K-edge energy of gadolinium can destruct tumor mass that has Gd-MSN distributed throughout tumor spheroids.
  • 8.9K
  • 22 Jul 2020
Topic Review
Cretaceous–Paleogene Extinction Event
The Cretaceous–Paleogene (K–Pg) extinction event, also known as the Cretaceous–Tertiary (K–T) extinction,[lower-alpha 2] was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the exception of some ectothermic species such as the sea turtles and crocodilians, no tetrapods weighing more than 25 kilograms (55 pounds) survived. It marked the end of the Cretaceous period, and with it the end of the entire Mesozoic Era, opening the Cenozoic Era that continues today. In the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows high levels of the metal iridium, which is rare in the Earth's crust, but abundant in asteroids. As originally proposed in 1980 by a team of scientists led by Luis Alvarez and his son Walter, it is now generally thought that the K–Pg extinction was caused by the impact of a massive comet or asteroid 10 to 15 km (6 to 9 mi) wide, 66 million years ago, which devastated the global environment, mainly through a lingering impact winter which halted photosynthesis in plants and plankton. The impact hypothesis, also known as the Alvarez hypothesis, was bolstered by the discovery of the 180 km (112 mi) Chicxulub crater in the Gulf of Mexico's Yucatán Peninsula in the early 1990s, which provided conclusive evidence that the K–Pg boundary clay represented debris from an asteroid impact. The fact that the extinctions occurred simultaneously provides strong evidence that they were caused by the asteroid. A 2016 drilling project into the Chicxulub peak ring confirmed that the peak ring comprised granite ejected within minutes from deep in the earth, but contained hardly any gypsum, the usual sulfate-containing sea floor rock in the region: The gypsum would have vaporized and dispersed as an aerosol into the atmosphere, causing longer-term effects on the climate and food chain. In October 2019, researchers reported that the event rapidly acidified the oceans producing ecological collapse and, in this way as well, produced long-lasting effects on the climate, and accordingly was a key reason for the end-Cretaceous mass extinction. In January 2020, scientists reported new evidence that the extinction event was mostly a result of the meteorite impact and not volcanism. Other causal or contributing factors to the extinction may have been the Deccan Traps and other volcanic eruptions, climate change, and sea level change. A wide range of species perished in the K–Pg extinction, the best-known being the non-avian dinosaurs. It also destroyed a myriad of other terrestrial organisms, including some mammals, pterosaurs, birds, lizards, insects, and plants. In the oceans, the K–Pg extinction killed off plesiosaurs and mosasaurs and devastated teleost fish, sharks, mollusks (especially ammonites, which became extinct), and many species of plankton. It is estimated that 75% or more of all species on Earth vanished. Yet the extinction also provided evolutionary opportunities: In its wake, many groups underwent remarkable adaptive radiation — sudden and prolific divergence into new forms and species within the disrupted and emptied ecological niches. Mammals in particular diversified in the Paleogene, evolving new forms such as horses, whales, bats, and primates. The surviving group of dinosaurs were avians, ground and water fowl who radiated into all modern species of bird. Teleost fish, and perhaps lizards also radiated.
  • 8.9K
  • 03 Nov 2022
Topic Review
Biomechanics of Table Tennis
Table tennis is a popular recreational and competitive sports at all levels. Recent research on table tennis maneuvers identified the differences between playing levels and between maneuvers using parameters which included ball and racket speed, joint kinematics and kinetics, electromyography, and plantar pressure distribution. Different maneuvers underlined changes on body posture and lines of movement which were accommodated particularly by the racket face angle, trunk rotation, knee and elbow joint movements, and thus different contributions of muscles. Higher-level players produced ball and strike at higher accuracy and repeatability but not necessarily lead to higher speed. In addition, higher-level players utilize superior whole-body coordination and footwork to compromise between agility and stability for a quality strike. Strengthening shoulder and wrist muscles could enhance the speed of the strike while personalized training shall be considered since motor coordination and adaptation vary among individuals.
  • 8.9K
  • 29 Oct 2020
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