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Coordinates: 12h 28m 24.97s, +31° 28′ 37.7″ Ton 618 is a hyperluminous, broad-absorption-line, radio-loud quasar and Lyman-alpha blob located near the border of the constellations Canes Venatici and Coma Berenices, with the projected comoving distance of approximately 18.2 billion light-years from Earth. It possesses one of the most massive black holes ever found, with a mass of 66 billion M☉.

38.7K
24 Nov 2022

Topic Review

Polar Moment of Inertia

The polar moment (of inertia), also known as second (polar) moment of area, is a quantity used to describe resistance to torsional deformation (deflection), in cylindrical (or non-cylindrical) objects (or segments of an object) with an invariant cross-section and no significant warping or out-of-plane deformation. It is a constituent of the second moment of area, linked through the perpendicular axis theorem. Where the planar second moment of area describes an object's resistance to deflection (bending) when subjected to a force applied to a plane parallel to the central axis, the polar second moment of area describes an object's resistance to deflection when subjected to a moment applied in a plane perpendicular to the object's central axis (i.e. parallel to the cross-section). Similar to planar second moment of area calculations ([math]\displaystyle{ I_x }[/math],[math]\displaystyle{ I_y }[/math], and [math]\displaystyle{ I_{xy} }[/math]), the polar second moment of area is often denoted as [math]\displaystyle{ I_z }[/math]. While several engineering textbooks and academic publications also denote it as [math]\displaystyle{ J }[/math] or [math]\displaystyle{ J_z }[/math], this designation should be given careful attention so that it does not become confused with the torsion constant, [math]\displaystyle{ J_t }[/math], used for non-cylindrical objects. Simply put, the polar moment of inertia is a shaft or beam's resistance to being distorted by torsion, as a function of its shape. The rigidity comes from the object's cross-sectional area only, and does not depend on its material composition or shear modulus. The greater the magnitude of the polar moment of inertia, the greater the torsional resistance of the object.

33.3K
14 Nov 2022

Topic Review

Impact of Nanotechnology

The impact of nanotechnology extends from its medical, ethical, mental, legal and environmental applications, to fields such as engineering, biology, chemistry, computing, materials science, and communications. Major benefits of nanotechnology include improved manufacturing methods, water purification systems, energy systems, physical enhancement, nanomedicine, better food production methods, nutrition and large-scale infrastructure auto-fabrication. Nanotechnology's reduced size may allow for automation of tasks which were previously inaccessible due to physical restrictions, which in turn may reduce labor, land, or maintenance requirements placed on humans. Potential risks include environmental, health, and safety issues; transitional effects such as displacement of traditional industries as the products of nanotechnology become dominant, which are of concern to privacy rights advocates. These may be particularly important if potential negative effects of nanoparticles are overlooked. Whether nanotechnology merits special government regulation is a controversial issue. Regulatory bodies such as the United States Environmental Protection Agency and the Health and Consumer Protection Directorate of the European Commission have started dealing with the potential risks of nanoparticles. The organic food sector has been the first to act with the regulated exclusion of engineered nanoparticles from certified organic produce, firstly in Australia and the UK, and more recently in Canada , as well as for all food certified to Demeter International standards

11.8K
18 Oct 2022

Biography

Albert Sherman Osborn, commonly known as A. S. Osborn (1858-1946), was a renowned forensic document examiner who is often referred to as the "Father of Document Examination". His contributions to forensic science and his ground-breaking work in the area of questioned document analysis have earned him recognition. Osborn, who started his career in document analysis in the late 19th century and es

11.7K
22 Mar 2023

Topic Review

Timoshenko-Ehrenfest Beam Theory

The Timoshenko-Ehrenfest beam theory was developed by Stephen Timoshenko and Paul Ehrenfest early in the 20th century. The model takes into account shear deformation and rotational bending effects, making it suitable for describing the behaviour of thick beams, sandwich composite beams, or beams subject to high-frequency excitation when the wavelength approaches the thickness of the beam. The resulting equation is of 4th order but, unlike Euler–Bernoulli beam theory, there is also a second-order partial derivative present. Physically, taking into account the added mechanisms of deformation effectively lowers the stiffness of the beam, while the result is a larger deflection under a static load and lower predicted eigenfrequencies for a given set of boundary conditions. The latter effect is more noticeable for higher frequencies as the wavelength becomes shorter (in principle comparable to the height of the beam or shorter), and thus the distance between opposing shear forces decreases. Rotary inertia effect was introduced by Bresse and Rayleigh. If the shear modulus of the beam material approaches infinity—and thus the beam becomes rigid in shear—and if rotational inertia effects are neglected, Timoshenko beam theory converges towards ordinary beam theory.

10.8K
20 Oct 2022

Topic Review

The drag polar or drag curve is the relationship between the lift on an aircraft and its drag, expressed in terms of the dependence of the drag coefficient on the lift coefficient. It may be described by an equation or displayed in a diagram called a polar plot.

8.8K
24 Oct 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.

8.2K
22 Jul 2020

Topic Review

Closed Timelike Curves

Closed timelike curves (CTCs) are space-time trajectories that return to their starting point without violating the laws of special relativity. A traveler along a CTC could journey into the future but arrive in its past, creating a possible violation of the principle of causality. Such CTCs occur in Gödel’s rotating universe and many other general relativistic solutions of classical Einstein’s field equations. The chronological protection conjecture suggests that Nature forbids this kind of situation.

7.8K
27 Jan 2021

Topic Review

Hiranyakashipu (Sanskrit: हिरण्यकशिपु, "clothed in gold"; the name is said to depict one who is very much fond of wealth: hiranya "gold," kashipu "soft cushion") is an Asura from the Puranic scriptures of Hinduism. Hiranyakashipu's Younger Brother, Hiranyaksha was slain by Varaha, one of the Avatars of Vishnu. Angered by this, Hiranyakashipu decided to gain magical powers by performing a penance for Lord Brahma. He was subsequently killed by the Narasimha Avatara of Lord Vishnu. His tale depicts the futility of desiring power over others and the strength of God's protection over his fully surrendered devotees (in the case of his son Prahlada). Hiranyakashipu, according to legend, was the king of the daityas and had earned a boon from Brahma that made him virtually indestructible. He grew arrogant, thought he was God, and demanded that everyone worship only him. The story of Hiranyakashipu is in three parts. The first has to do with the curse of the Four Kumaras on the gatekeepers of Vaikuntha, Jaya and Vijaya, which causes them to be born as the daityas Hiranyakashipu and Hiranyaksha. The second part deals with Hiranyakashipu's penance to propitiate Brahma and gain a boon from him. The final part deals with his efforts to kill his son Prahlada (a devotee of Vishnu) and his subsequent death at the hands of Narasimha.

6.3K
15 Nov 2022

Topic Review

Mooning is the act of displaying one's bare buttocks by removing clothing, e.g., by lowering the backside of one's trousers and underpants, usually bending over, whether also exposing the genitals or not. Mooning is used in the English-speaking world to express protest, scorn, disrespect, or provocation, or can be done for shock value, fun, or as a form of exhibitionism. Some jurisdictions regard mooning to be indecent exposure, sometimes depending on the context.

6.1K
27 Oct 2022

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