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Topic Review
Phase Curve
In astronomy a phase curve describes the brightness of a reflecting body as a function of its phase angle. The brightness usually refers the object's absolute magnitude, which, in turn, is its apparent magnitude at a distance of astronomical unit from the Earth and Sun. The phase angle equals the arc subtended by the observer and the sun as measured at the body. The phase curve is useful for characterizing an object's regolith (soil) and atmosphere. It is also the basis for computing the geometrical albedo and the Bond albedo of the body. In ephemeris generation, the phase curve is used in conjunction with the distances from the object to the Sun and the Earth to calculate the apparent magnitude.
  • 638
  • 15 Nov 2022
Topic Review
Pulse Forming Network
A pulse forming network (PFN) is an electric circuit that accumulates electrical energy over a comparatively long time, then releases the stored energy in the form of a relatively square pulse of comparatively brief duration for various pulsed power applications. In a PFN, energy storage components such as capacitors, inductors or transmission lines are charged by means of a high voltage power source, then rapidly discharged into a load via a high voltage switch, such as a spark gap or hydrogen thyratron. Repetition rates range from single pulses to about 104 per second. PFNs are used to produce precise nanosecond-length pulses of electricity to power devices such as klystron or magnetron tube oscillators in radar sets, pulsed lasers, particle accelerators, flashtubes, and high voltage utility test equipment. Much high energy research equipment is operated in a pulsed mode, both to keep heat dissipation down and because high energy physics often occurs at short time scales, so large PFNs are widely used in high energy research. They have been used to produce nanosecond length pulses with voltages of up to 106 - 107 volts and currents up to 106 amps, with peak power in the terawatt range, similar to lightning bolts.
  • 637
  • 01 Nov 2022
Topic Review
Role of Uranium in the Nuclear Fuel Cycle
Uranium was discovered in 1789 by the German chemist Martin Heinrich Klaproth. It is the most known and used actinide element mainly because of its usage in nuclear fuel processing; however, the application potential of uranium compounds is much broader, stretching, e.g., into the field of organometallic synthesis, catalysis and beyond. Moreover, uranium is one of the few naturally occurring actinides, whereas the other members, with the exception of thorium, are considered to be human-made, despite their natural occurrence in traces as a result of uranium and thorium spontaneous fissions. In nature, uranium occurs as three main isotopes, where the non-fissile 238U is the most abundant, encompassing over 99% of the available uranium resources.
  • 635
  • 23 May 2022
Topic Review
Neck-Tongue Syndrome
Neck-tongue syndrome (NTS) is rare, and characterized by unilateral upper neck or occipital pain and paresthesia in the ipsilateral hemisphere of the tongue due to neck movement. Treatment for NTS is mainly conservative. 
  • 634
  • 22 Nov 2021
Topic Review
Thermal Conductivity Improvement of PCCs
To overcome the long-standing disadvantages of PCMs, for instance, small values of thermal conductivity, liquid leakage, separation of phase, and the problem of supercooling, advanced phase change composites (PCCs) manufactured by chemical modifications or the incorporation of functional additives are essential to overcome these disadvantages and promote the large-scale application of PCMs.
  • 634
  • 29 Nov 2022
Topic Review
Soyuz TM-22
Soyuz TM-22 was a Soyuz spaceflight to the Soviet space station Mir. It launched from Baikonur Cosmodrome Launch Pad 1 on September 3, 1995. After two days of free flight, the crew docked with Mir to become Mir Principal Expedition 20 and Euromir 95. Mir 20 was a harbinger of the multinational missions that would be typical of the International Space Station. After 179 days, 1 hour and 42 minutes on orbit, Reiter obtained the record for spaceflight duration by a Western European.
  • 633
  • 11 Oct 2022
Topic Review
Cosmology Can Serve to Determine Neutrino's Properties
Neutrino particles have been found, due to their non-interacting, almost-vanishing mass, and relativistic nature, as being suitable to hold roles in many phenomena in nature, which have made them attract a large interest among the scientific community. In particular, on the cosmological level, the neutrino is one of the few components whose contribution to the Universe energy budget changes with its expansion, from being part of the radiation to that of the matter density, with implications on the expansion of the background or the growth of large-scale structures. It has also the feature of being abundantly present since the Universe’s early beginning, participating by then to the different phases of its evolution, which allows us to constrain its main properties such as its mass and number of species by any of the known cosmological observables.
  • 632
  • 27 May 2022
Topic Review
InN SAs for Ultrafast Lasers
New fabrication methods are strongly demanded for the development of thin-film saturable absorbers with improved optical properties (absorption band, modulation depth, nonlinear optical response). In this sense, we investigate the performance of indium nitride (InN) epitaxial layers with low residual carrier concentration (<1018 cm^-3), which results in improved performance at telecom wavelengths (1560 nm). These materials have demonstrated a huge modulation depth of 23% and a saturation fluence of 830 uJ/cm2, and a large saturable absorption around -3 x10^4 cm/GW has been observed, attaining an enhanced, nonlinear change in transmittance. We have studied the use of such InN layers as semiconductor saturable absorber mirrors (SESAMs) for an erbium (Er)-doped fiber laser to perform mode-locking generation at 1560 nm. We demonstrate highly stable, ultrashort (134 fs) pulses with an energy of up to 5.6 nJ.a
  • 631
  • 01 Dec 2020
Topic Review
Advances in Bioinspired Superhydrophobic Surfaces Made from Silicones
As research on superhydrophobic materials inspired by the self-cleaning and water-repellent properties of plants and animals in nature continues, the superhydrophobic preparation methods and the applications of superhydrophobic surfaces are widely reported. Silicones are preferred for the preparation of superhydrophobic materials because of their inherent hydrophobicity and strong processing ability. In the preparation of superhydrophobic materials, silicones can both form micro-/nano-structures with dehydration condensation and reduce the surface energy of the material surface because of their intrinsic hydrophobicity. The superhydrophobic layers of silicone substrates are characterized by simple and fast reactions, high-temperature resistance, UV resistance, and anti-aging. Although silicone superhydrophobic materials have the disadvantages of relatively low mechanical stability, this can be improved by the rational design of the material structure. 
  • 629
  • 27 Feb 2023
Topic Review
Exploration Mission-1
Exploration Mission-1 or EM-1 (previously known as Space Launch System 1 or SLS-1) is the uncrewed first planned flight of the Space Launch System and the second flight of the Orion Multi-Purpose Crew Vehicle. The launch is planned for June 2020 from Launch Complex 39B at the Kennedy Space Center. The Orion spacecraft will spend approximately 3 weeks in space, including 6 days in a retrograde orbit around the Moon. It is planned to be followed by Exploration Mission 2 in 2023.
  • 627
  • 28 Sep 2022
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