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Topic Review
Old Quantum Theory
The old quantum theory is a collection of results from the years 1900–1925 which predate modern quantum mechanics. The theory was never complete or self-consistent, but was rather a set of heuristic corrections to classical mechanics. The theory is now understood as the semi-classical approximation to modern quantum mechanics. The main and final accomplishments of the old quantum theory were the determination of the modern form of the periodic table by Edmund Stoner and the Pauli Exclusion Principle which were both premised on the Arnold Sommerfeld enhancements to the Bohr model of the atom. The main tool of the old quantum theory was the Bohr–Sommerfeld quantization condition, a procedure for selecting out certain states of a classical system as allowed states: the system can then only exist in one of the allowed states and not in any other state.
  • 873
  • 22 Nov 2022
Topic Review
Applications of Thermal Plasma Waste Treatment
Non-thermal as well as thermal plasmas are used for the processing of materials and waste. Thermal (hot) plasmas are characterized by their high energy density and by the equal temperatures of the electrons and the heavy particles, i.e., thermal plasmas are in local thermodynamic equilibrium. Non-thermal plasmas (also called cold plasmas), on the other hand, are non-equilibrium ionized gases, which are characterized by lower energy densities and by the large difference between the electron temperature and the temperature of the heavy particles.
  • 872
  • 25 Jul 2022
Topic Review Peer Reviewed
Wavefunction Collapse Broadens Molecular Spectrum
Spectral lines in the optical spectra of atoms, molecules, and other quantum systems are characterized by a range of frequencies ω or a range of wavelengths λ=2πc/ω, where c is the speed of light. Such a frequency or wavelength range is called the width of the spectral lines (linewidth). It is influenced by many specific factors. Thermal motion of the molecules results in broadening of the lines as a result of the Doppler effect (thermal broadening) and by their collisions (pressure broadening). The electric fields of neighboring molecules lead to Stark broadening. The linewidth to be considered here is the so-called parametric broadening (PB) of spectral lines in the optical spectrum. PB can be considered the fundamental type of broadening of the electronic vibrational–rotational (rovibronic) transitions in a molecule, which is the direct manifestation of the basic concept of the collapse of a wavefunction that is postulated by the Copenhagen interpretation of quantum mechanics. Thus, that concept appears to be not only valid but is also useful for predicting physically observable phenomena.
  • 871
  • 11 Apr 2023
Topic Review
Rigid Templates for Fabricating 3D Nanostructures
Rigid templates are defined as opposed to soft templates, and are made of hard materials. Rigid templates have good chemical stability and mechanical rigidity, which are mostly used for the fabrication of nanostructure arrays. A wide choice of rigid templates is available, such as silicon, anodic aluminum oxide, carbon, silica spheres, biological structures, and so forth.
  • 869
  • 14 Jun 2022
Biography
Barbara Jacak
Barbara Jacak is a nuclear physicist who uses heavy ion collisions for fundamental studies of hot, dense nuclear matter. She is Director of the Nuclear Science Division, Lawrence Berkeley National Laboratory, and a professor of Physics at UC Berkeley.[1] Before going to Berkeley, she was a member of the Department of Physics and Astronomy at Stony Brook University, where she held the rank of Dis
  • 869
  • 06 Dec 2022
Topic Review
The Concept of “Quantum-Like”
The birth and spread of the prefix “quantum-” to disciplines other than physics, and the introduction of the term “quantum-like”, reflect the increasing dissatisfaction with the perceived limits and pitfalls of classic Western thought. Of course, the latter remains valuable; what is wrong is its dogmatic use and the claim of its exclusive capacity to comprehend the world. The development of quantum physics has been paralleled by the introduction of paraconsistent logics, such as fuzzy logic and dialetheism, a clear sign of the need for smoothing the inflexibility of Aristotelian logic. There is also a fil rouge (viz. an epistemological symmetry) linking the paradigm of quantum physics to ancient pre-Socratic and Eastern philosophies, suggesting the need for reappraising them in the process of reexamination of the classical thought. The increasing use of the term “quantum-like” calls for the defining and sharing of its meaning in order to properly adopt it and avoid possible misuse. 
  • 868
  • 14 Mar 2022
Biography
John Holdren
John Paul Holdren (Sewickley, Pennsylvania, March 1, 1944) is an American scientist. He served as the senior advisor to President Barack Obama on science and technology issues through his roles as Assistant to the President for Science and Technology, Director of the White House Office of Science and Technology Policy, and Co-Chair of the President’s Council of Advisors on Science and Technolo
  • 868
  • 30 Nov 2022
Topic Review
Electrostatic Fluid Accelerator
An electrostatic fluid accelerator (EFA) is a device which pumps a fluid such as air without any moving parts. Instead of using rotating blades, as in a conventional propeller or in the turbine of an airbreathing jet engine, an EFA uses the Coulomb force from a high voltage electric field to accelerate electrically charged air molecules, a phenomenon studied in the academic discipline called electrohydrodynamics (EHD). Because air molecules are normally electrically neutral, not charged, the EFA has to create some charged molecules, or ions, first. Thus there are three basic steps in the fluid acceleration process: ionize air molecules, accelerate those charge carriers and, through ion-ion and ion-neutral collisions, push many more neutral molecules in a desired direction, and finally neutralize ions again to eliminate any net charge in the downstream flow. This principle is used for spacecraft propulsion in ion thrusters. The basic working principle has been understood for some time but only in recent years have seen developments in the design and manufacture of EFA devices that may allow them to find practical and economical applications, such as in micro-cooling of electronics components.
  • 865
  • 31 Oct 2022
Biography
Paul Steinhardt
Paul Joseph Steinhardt (born December 25, 1952) is an American theoretical physicist whose principal research is in cosmology and condensed matter physics. He is currently the Albert Einstein Professor in Science at Princeton University where he is on the faculty of both the Departments of Physics and of Astrophysical Sciences. [1] Steinhardt is best known for his development of new theories of
  • 864
  • 30 Nov 2022
Topic Review
Geiger-Marsden Experiments
The Geiger–Marsden experiments (also called the Rutherford gold foil experiment) were a landmark series of experiments by which scientists learned that every atom has a nucleus where all of its positive charge and most of its mass is concentrated. They deduced this after measuring how an alpha particle beam is scattered when it strikes a thin metal foil. The experiments were performed between 1908 and 1913 by Hans Geiger and Ernest Marsden under the direction of Ernest Rutherford at the Physical Laboratories of the University of Manchester.
  • 863
  • 25 Oct 2022
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