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Topic Review
Ramchandra Pode
I am involved in the field of organic light emitting devices since 2002. I also worked as visiting Scientist at Korea Electronics Technology Institute, South Korea in 2003 and 2005 (Brain Pool, KOFST) on OLEDs devices. I am specialized in Organic Light Emitting Diode (OLEDs) devices and displays and acquired enough expertize to conduct the research project on OLEDs. During these years, I have published around 65 research articles in various SCI journals of repute. In addition, I have contributed chapters to two books on OLEDs.
  • 840
  • 28 Oct 2020
Topic Review
The BrIdge voLcanic LIdar—BILLI
Volcanologists have demonstrated that carbon dioxide (CO2) fluxes are precursors of volcanic eruptions. Controlling volcanic gases and, in particular, the CO2 flux, is technically challenging, but we can retrieve useful information from magmatic/geological process studies for the mitigation of volcanic hazards including air traffic security. Existing techniques used to probe volcanic gas fluxes have severe limitations such as the requirement of near-vent in situ measurements, which is unsafe for operators and deleterious for equipment. In order to overcome these limitations, a novel range-resolved DIAL-Lidar (Differential Absorption Light Detection and Ranging) has been developed as part of the ERC (European Research Council) Project “BRIDGE”, for sensitive, remote, and safe real-time CO2 observations.
  • 840
  • 09 Oct 2020
Topic Review
Former Constellation
Former constellations are old historical Western constellations that for various reasons are no longer widely recognised or are not officially recognised by the International Astronomical Union (IAU). Prior to 1930, many of these defunct constellations were traditional in one or more countries or cultures. Some only lasted decades but others were referred to over many centuries. All are now recognised only for having classical or historical value. Many former constellations had complex Latinised names after objects, people, or mythological or zoological creatures. Others with unwieldy names were shortened for convenience. For example, Scutum Sobiescianum was reduced to Scutum, Mons Mensae to Mensa, and Apparatus Sculptoris to Sculptor. Some of the Northern Sky's former constellations were placed in the less populated regions between the traditional brighter constellations just to fill gaps. In the Southern Sky, new constellations were often created from about the 15th century by voyagers who began journeying south of the Equator. European countries like England, France, the Netherlands, German or Italian states, etc., often supported and popularised their own constellation outlines. In some cases, different constellations occupied overlapping areas and included the same stars. These former constellations are often found in older books, star charts, or star catalogues. The 88 modern constellation names and boundaries were standardised by Eugene Delporte for the IAU in 1930, under an international agreement, removing any possible astronomical ambiguities between astronomers from different countries. Nearly all former or defunct constellations differ in their designated boundaries in as much as they have outlines that do not follow the exact lines of right ascension and declination.
  • 839
  • 05 Nov 2022
Topic Review
NanoPutian
NanoPutians are a series of organic molecules whose structural formulae resemble human forms. James Tour et al. (Rice University) designed and synthesized these compounds in 2003 as a part of a sequence on chemical education for young students. The compounds consist of two benzene rings connected via a few carbon atoms as the body, four acetylene units each carrying an alkyl group at their ends which represents the hands and legs, and a 1,3-dioxolane ring as the head. Tour and his team at Rice University used the NanoPutians in their NanoKids educational outreach program. The goal of this program was to educate children in the sciences in an effective and enjoyable manner. They have made several videos featuring the NanoPutians as anthropomorphic animated characters. Construction of the structures depends on Sonogashira coupling and other synthetic techniques. By replacing the 1,3-dioxolane group with an appropriate ring structure, various other types of putians have been synthesized, e.g. NanoAthlete, NanoPilgrim, and NanoGreenBeret. Placing thiol (R-SH) functional groups at the end of the legs enables them to "stand" on a gold surface. "NanoPutian" is a portmanteau of nanometer, a unit of length commonly used to measure chemical compounds, and lilliputian, a fictional race of humans in the novel Gulliver's Travels by Jonathan Swift.
  • 840
  • 20 Oct 2022
Topic Review
Direct Ultrafast Laser Processing
Direct ultrafast laser processing is nowadays considered the most flexible technique allowing to generate complex 3D optical functions in bulk glasses. The fact that the built-in optical element is embedded in the material brings several advantages in terms of prototype stability and lifetime, but equally in terms of complexity and number of possible applications, due to the 3D design. The generated optical functions, and in particular the single mode character of the light guiding element alongside the accessibility toward different spectral windows, depend on the refractive index contrast that can be achieved within the material transparency window and on the characteristic dimensions of the optical modification. In particular, the accessibility to the infrared and mid-infrared spectral domains, and to the relevant applications in sensing and imaging, requires increasing the cross-section of the guiding element in order to obtain the desired normalized frequency. Moreover, efficient signal extraction from the transported light requires nanometer size void-like index structures. All this demands a thorough knowledge and an optimal control of the material response within the interaction with the ultrafast laser pulse.
  • 840
  • 25 Jun 2021
Topic Review
Scanless and Detectorless Imaging System
Optical feedback interferometry is a versatile and robust technology for both sensing and imaging applications, available at all wavelengths were a semiconductor laser exists, from 270 nm to 120 μm. It can be easily adapted to fiber integrated systems and promises to be compatible also to silicon photonics.
  • 839
  • 18 Nov 2020
Topic Review
Polarization-Sensitive Digital Holographic Imaging
Polarization-sensitive digital holographic imaging (PS-DHI) is a recent imaging technique based on interference among several polarized optical beams. PS-DHI allows simultaneous quantitative three-dimensional reconstruction and quantitative evaluation of polarization properties of a given sample with micrometer scale resolution. Since this technique is very fast and does not require labels/markers, it finds application in several fields, from biology to microelectronics and micro-photonics.
  • 838
  • 10 Aug 2020
Topic Review
Stationary Action Principle
The stationary action principle – also known as the principle of least action – is a variational principle that, when applied to the action of a mechanical system, yields the equations of motion for that system. The principle states that the trajectories (i.e. the solutions of the equations of motion) are stationary points (a.k.a. critical points) of the system's action functional. The term "least action" is a historical misnomer since the principle has no minimality requirement: the value of the action functional need not be minimal (even locally) on the trajectories. The principle can be used to derive Newtonian, Lagrangian and Hamiltonian equations of motion, and even general relativity (see Einstein–Hilbert action). In relativity, a different action must be minimized or maximized. The classical mechanics and electromagnetic expressions are a consequence of quantum mechanics. The stationary action method helped in the development of quantum mechanics. In 1933, the physicist Paul Dirac demonstrated how this principle can be used in quantum calculations by discerning the quantum mechanical underpinning of the principle in the quantum interference of amplitudes. Subsequently Julian Schwinger and Richard Feynman independently applied this principle in quantum electrodynamics. The principle remains central in modern physics and mathematics, being applied in thermodynamics, fluid mechanics, the theory of relativity, quantum mechanics, particle physics, and string theory and is a focus of modern mathematical investigation in Morse theory. Maupertuis' principle and Hamilton's principle exemplify the principle of stationary action. The action principle is preceded by earlier ideas in optics. In Ancient Greece , Euclid wrote in his Catoptrica that, for the path of light reflecting from a mirror, the angle of incidence equals the angle of reflection. Hero of Alexandria later showed that this path was the shortest length and least time. Scholars often credit Pierre Louis Maupertuis for formulating the principle of least action because he wrote about it in 1744 and 1746. However, Leonhard Euler discussed the principle in 1744, and evidence shows that Gottfried Leibniz preceded both by 39 years.
  • 837
  • 14 Oct 2022
Topic Review
North Magnetic Pole
The North Magnetic Pole is a wandering point on the surface of Earth's Northern Hemisphere at which the planet's magnetic field points vertically downwards (in other words, if a magnetic compass needle is allowed to rotate about a horizontal axis, it will point straight down). There is only one location where this occurs, near (but distinct from) the Geographic North Pole and the Geomagnetic North Pole. The North Magnetic Pole moves over time according to magnetic changes and flux lobe elongation in the Earth's outer core. In 2001, it was determined by the Geological Survey of Canada to lie west of Ellesmere Island in northern Canada at 81°18′N 110°48′W / 81.3°N 110.8°W / 81.3; -110.8 (Magnetic North Pole 2001). It was situated at 83°06′N 117°48′W / 83.1°N 117.8°W / 83.1; -117.8 (Magnetic North Pole 2005 est) in 2005. In 2009, while still situated within the Canadian Arctic at 84°54′N 131°00′W / 84.9°N 131°W / 84.9; -131 (Magnetic North Pole 2009), it was moving toward Russia at between 55 and 60 km (34 and 37 mi) per year. As of 2019, the pole is projected to have moved beyond the Canadian Arctic to 86°26′52.8″N 175°20′45.06″E / 86.448°N 175.34585°E / 86.448; 175.34585 (Magnetic North Pole 2019 est). Its southern hemisphere counterpart is the South Magnetic Pole. Since Earth's magnetic field is not exactly symmetrical, the North and South Magnetic Poles are not antipodal, meaning that a straight line drawn from one to the other does not pass through the geometric center of Earth. Earth's North and South Magnetic Poles are also known as magnetic dip poles, with reference to the vertical "dip" of the magnetic field lines at those points.
  • 831
  • 17 Oct 2022
Topic Review
Micromegas Detectors for Physics
Micromegas (MICRO-MEsh GAseous Structure) detectors have found common use in different applications since their development in 1996 by the group of I. Giomataris and G. Charpak. 
  • 831
  • 23 Jun 2021
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