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Topic Review
Types of Liquid Crystals
The liquid-crystalline state of matter (mesomorphic state, or mesophase) is intermediate between the crystalline and liquid states, simultaneously showing some of the anisotropic properties of solids and the fluidity of liquids. In this state, materials demonstrate a tendency to flow like liquids and have some properties similar to solids. LCs may be divided into two main classes, named thermotropics and lyotropics. The importance of liquid crystals, alongside with their technical applications, lies in their role as carriers of life. In fact, fully ordered solids are a dead matter, and fully disordered liquids are also dead. But liquid crystals, as partially ordered soft matter systems, bear all qualities that had been necessary for the emergence of life. Practically all biological structures show some features pf liquid crystalline ordering. 
  • 655
  • 15 Jun 2023
Topic Review
Types of Membrane Transporters in Plants
Membrane transporters are proteins that mediate the entry and exit of substances through the plasma membrane and organellar membranes and are capable of recognizing and binding to specific substances, thereby facilitating substance transport. Membrane transporters are divided into different types, e.g., ion transporters, sugar transporters, amino acid transporters, and aquaporins, based on the substances they transport. These membrane transporters inhibit reactive oxygen species (ROS) generation through ion regulation, sugar and amino acid transport, hormone induction, and other mechanisms. They can also promote enzymatic and nonenzymatic reactions in plants, activate antioxidant enzyme activity, and promote ROS scavenging. Moreover, membrane transporters can transport plant growth regulators, solute proteins, redox potential regulators, and other substances involved in ROS metabolism through corresponding metabolic pathways, ultimately achieving ROS homeostasis in plants.
  • 173
  • 20 Feb 2024
Topic Review
Types of Snow
Types of snow can be designated by the shape of its flakes, description of how it is falling, and by how it collects on the ground. A blizzard and snow storm indicate heavy snowfalls over a large area, snow squalls give heavy snowfalls over narrow bands, while flurries are used for the lightest snowfall. Types which fall in the form of a ball, rather than a flake, are known as graupel, with sleet and snow grains as types of graupel. Once on the ground, snow can be categorized as powdery when fluffy, granular when it begins the cycle of melting and refreezing, and crud or eventually ice once it packs down into a dense drift after multiple melting and refreezing cycles. When powdering, snow drifts with the wind or ground blizzard, sometimes to the depth of several metres. After attaching to hillsides, blown snow can evolve into a snow slab, which is an avalanche hazard on steep slopes.
  • 2.8K
  • 04 Nov 2022
Topic Review
U-NII
The Unlicensed National Information Infrastructure (U-NII) radio band is part of the radio frequency spectrum used by IEEE 802.11a devices and by many wireless ISPs. It operates over four ranges: Wireless ISPs generally use 5.725–5.825 GHz. In the USA licensed amateur radio operators are authorized 5.650–5.925 GHz by Part 97.303 of the FCC rules. U-NII is an FCC regulatory domain for 5 GHz wireless devices. U-NII power limits are defined by the United States CFR Title 47 (Telecommunication), Part 15 - Radio Frequency Devices, Subpart E - Unlicensed National Information Infrastructure Devices, Paragraph 15.407 - General technical requirements. Regulatory use in individual countries may differ. The European HiperLAN standard operates in same frequency band as the U-NII.
  • 886
  • 17 Oct 2022
Topic Review
Udwadia–Kalaba Equation
In theoretical physics, the Udwadia–Kalaba equation is a method for deriving the equations of motion of a constrained mechanical system. The equation was first described by Firdaus E. Udwadia and Robert E. Kalaba in 1992. The approach is based on Gauss's principle of least constraint. The Udwadia–Kalaba equation applies to both holonomic constraints and nonholonomic constraints, as long as they are linear with respect to the accelerations. The equation generalizes to constraint forces that do not obey D'Alembert's principle.
  • 516
  • 14 Oct 2022
Topic Review
Ultrafast Fiber Technologies for Compact Laser Wake Field
Technologies, performances and maturity of ultrafast fiber lasers and fiber delivery of ultrafast pulses are used for the medical deployment of laser-wake-field acceleration (LWFA). The compact ultrafast fiber lasers produce intense laser pulses with flexible hollow-core fiber delivery to facilitate electron acceleration in the laser-stimulated wake field near treatment site, empowering endoscopic LWFA brachytherapy. With coherent beam combination of multiple fiber amplifiers, the advantages of ultrafast fiber lasers are further extended to bring in more capabilities in compact LWFA applications.
  • 537
  • 08 Jul 2022
Topic Review
Ultrafast Laser in Orthopedic Surgery
The potential of ultrafast lasers (pico- to femtosecond) in orthopedics-related procedures has been studied extensively for clinical adoption. As compared to conventional laser systems with continuous wave or longer wave pulse, ultrafast lasers provide advantages such as higher precision and minimal collateral thermal damages. Translation to surgical applications in the clinic has been restrained by limitations of material removal rate and pulse average power, whereas the use in surface texturing of implants has become more refined to greatly improve bioactivation and osteointegration within bone matrices.
  • 596
  • 07 May 2022
Topic Review
Ultrasensitive Magnetic Field Sensors
One of the cutting-edge topics today is the use of magnetic field sensors for applications such as magnetocardiography, magnetotomography, magnetomyography, magnetoneurography, or their application in point-of-care devices. Types of magnetic field sensors include direct current superconducting quantum interference devices, search coil, fluxgate, magnetoelectric, giant magneto-impedance, anisotropic/giant/tunneling magnetoresistance, optically pumped, cavity optomechanical, Hall effect, magnetoelastic, spin wave interferometry, and those based on the behavior of nitrogen-vacancy centers in the atomic lattice of diamond. Current developments of magnetometry in biological diagnostics are revised in review paper DOI: 10.3390/s20061569.
  • 2.6K
  • 11 Jun 2021
Topic Review Peer Reviewed
Undecidability and Quantum Mechanics
Recently, great attention has been devoted to the problem of the undecidability of specific questions in quantum mechanics. In this context, it has been shown that the problem of the existence of a spectral gap, i.e., energy difference between the ground state and the first excited state, is algorithmically undecidable. Using this result herein proves that the existence of a quantum phase transition, as inferred from specific microscopic approaches, is an undecidable problem, too. Indeed, some methods, usually adopted to study quantum phase transitions, rely on the existence of a spectral gap. Since there exists no algorithm to determine whether an arbitrary quantum model is gapped or gapless, and there exist models for which the presence or absence of a spectral gap is independent of the axioms of mathematics, it infers that the existence of quantum phase transitions is an undecidable problem. 
  • 1.2K
  • 18 Oct 2022
Topic Review
Undernutrition in fragility hip fracture
Geriatric patients with hip fractures often experience overlap in problems related to nutrition, including undernutrition, sarcopenia, and frailty. Such problems are powerful predictors of adverse responses, although few healthcare professionals are aware of them and therefore do not implement effective interventions.
  • 814
  • 30 Sep 2021
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