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Topic Review
Solar Chemical
Solar chemical refers to a number of possible processes that harness solar energy by absorbing sunlight in a chemical reaction. The idea is conceptually similar to photosynthesis in plants, which converts solar energy into the chemical bonds of glucose molecules, but without using living organisms, which is why it is also called artificial photosynthesis. A promising approach is to use focused sunlight to provide the energy needed to split water into its constituent hydrogen and oxygen in the presence of a metallic catalyst such as zinc. This is normally done in a two-step process so that hydrogen and oxygen are not produced in the same chamber, which creates an explosion hazard. Another approach involves taking the hydrogen created in this process and combining it with carbon dioxide to create methane. The benefit of this approach is that there is an established infrastructure for transporting and burning methane for power generation, which is not true for hydrogen. One main drawback to both of these approaches is common to most methods of energy storage: adding an extra step between energy collection and electricity production drastically decreases the efficiency of the overall process.
  • 487
  • 22 Nov 2022
Topic Review
Simple Models of Pulmonary Artifacts
Nowadays, the diagnostic value of the artefactual information provided by lung ultrasound images is widely recognized by physicians. In particular, the existence of a correlation between the visual characteristics of the vertical artifacts, which arise from the pleura line, and the genesis (pneumogenic or cardiogenic) of a pulmonary disorder is commonly accepted. However, the link between these visual characteristics and the causes which determine them is still unclear. In order to derive further information from the visual inspection of the vertical artifacts the mechanisms which control the artifact formation must be identified. The link between the visual characteristics of the vertical artifacts (the observed effect) and the distribution of the aerated spaces at the pleural level (the cause) must be addressed. Plausible mechanisms should be illustrated through experimental results and through the theoretical analysis of simple models.
  • 486
  • 27 Oct 2021
Topic Review
Polymer Waveguide-Based Sensors
The optical waveguide (WG) is one of the fundamental components of integrated photonics. Polymer WGs can operate in either single-mode (with core diameters between 2 μm and 5 μm) or multimode (with core dimensions generally between 30 μm and 500 μm) regimes. They are both entirely consistent with the matching optical fiber type due to the similar mode field diameter. A WG is simply utilized as a light link to connect external instruments to a sampling point or an optical sensing element in an extrinsic sensor. In biomedicine, environmental monitoring, process control, and safety, extrinsic sensors are already widely employed.
  • 486
  • 08 Mar 2023
Topic Review
Treatment of Chrysanthemum Synthetic Seeds by SDBD Plasma
Implementation of the surface dielectric barrier discharge (SDBD) plasma treatment before sowing represents a promising strategy for future investigations and sustainable use of cold plasma in synseed biotechnology. Plasma-treated chrysanthemum synseeds showed a better survival rate and overall plantlet growth under greenhouse conditions in comparison to untreated synseeds.
  • 485
  • 12 Apr 2022
Topic Review
RESOLFT
RESOLFT, an acronym for REversible Saturable OpticaL Fluorescence Transitions, denotes a group of optical fluorescence microscopy techniques with very high resolution. Using standard far field visible light optics a resolution far below the diffraction limit down to molecular scales can be obtained. With conventional microscopy techniques, it is not possible to distinguish features that are located at distances less than about half the wavelength used (i.e. about 200 nm for visible light). This diffraction limit is based on the wave nature of light. In conventional microscopes the limit is determined by the used wavelength and the numerical aperture of the optical system. The RESOLFT concept surmounts this limit by temporarily switching the molecules to a state in which they cannot send a (fluorescence-) signal upon illumination. This concept is different from for example electron microscopy where instead the used wavelength is much smaller.
  • 477
  • 25 Nov 2022
Topic Review
Nanoflares
A nanoflare is a very small episodic heating event which happens in the corona, the external atmosphere of the Sun. The hypothesis of small impulsive heating events as a possible explanation of the coronal heating was first suggested by Thomas Gold and then later developed and dubbed "nanoflares" by Eugene Parker. According to Parker a nanoflare arises from an event of magnetic reconnection which converts the energy stored in the solar magnetic field into the motion of the plasma. The plasma motion (thought as fluid motion) occurs at length-scales so small that it is soon damped by the turbulence and then by the viscosity. In such a way the energy is quickly converted into heat, and conducted by the free electrons along the magnetic field lines closer to the place where the nanoflare switches on. In order to heat a region of very high X-ray emission, over an area 1" x 1", a nanoflare of 1017 J should happen every 20 seconds, and 1000 nanoflares per second should occur in a large active region of 105 x 105 km2. On the basis of this theory, the emission coming from a big flare could be caused by a series of nanoflares, not observable individually. The nanoflare model has long suffered from a lack of observational evidence. Simulations predict that nanoflares produce a faint, hot (~10 MK) component of the emission measure. Unfortunately, current instruments, such as the Extreme-Ultraviolet Imaging Spectrometer on board Hinode, are not adequately sensitive to the range in which this faint emission occurs, making a confident detection impossible. Recent evidence from the EUNIS sounding rocket has provided some spectral evidence for non-flaring plasma at temperatures near 9 MK in active region cores.
  • 477
  • 30 Nov 2022
Topic Review
Isotopes of Osmium
Osmium (76Os) has seven naturally occurring isotopes, five of which are stable: 187Os, 188Os, 189Os, 190Os, and (most abundant) 192Os. The other natural isotopes, 184Os, and 186Os, have extremely long half-life (1.12×1013 years and 2×1015 years, respectively) and for practical purposes can be considered to be stable as well. 187Os is the daughter of 187Re (half-life 4.56×1010 years) and is most often measured in an 187Os/188Os ratio. This ratio, as well as the 187Re/188Os ratio, have been used extensively in dating terrestrial as well as meteoric rocks. It has also been used to measure the intensity of continental weathering over geologic time and to fix minimum ages for stabilization of the mantle roots of continental cratons. However, the most notable application of Os in dating has been in conjunction with iridium, to analyze the layer of shocked quartz along the Cretaceous–Paleogene boundary that marks the extinction of the dinosaurs 66 million years ago. There are also 30 artificial radioisotopes, the longest-lived of which is 194Os with a half-life of six years; all others have half-lives under 94 days. There are also nine known nuclear isomers, the longest-lived of which is 191mOs with a half-life of 13.10 hours. All isotopes and nuclear isomers of osmium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.
  • 477
  • 27 Oct 2022
Topic Review
Impact of Nanostructured Silicon on Thermoelectric Performance
Nanostructured materials remarkably improve the overall properties of thermoelectric devices, mainly due to the increase in the surface-to-volume ratio. This behavior is attributed to an increased number of scattered phonons at the interfaces and boundaries of the nanostructures. Among many other materials, nanostructured Si was used to expand the power generation compared to bulk crystalline Si, which leads to a reduction in thermal conductivity. However, the use of nanostructured Si leads to a reduction in the electrical conductivity due to the formation of low dimensional features in the heavily doped Si regions. Accordingly, the fabrication of hybrid nanostructures based on nanostructured Si and other different nanostructured materials constitutes another strategy to combine a reduction in the thermal conductivity while keeping the good electrical conduction properties. 
  • 476
  • 08 Aug 2022
Topic Review
Dense Superconducting Hydrides
To date, about twenty hydrides experiments have been reported to exhibit high-Tc superconductivity and their Tc agree well with the predicted values. However, there are still some controversies existing between the predictions and experiments.
  • 475
  • 20 Dec 2021
Topic Review
An introduction to the Recent Advances in Nanophotonics
Nanophotonics is an emerging multidisciplinary frontier of science and engineering. Its high potential in contributing to the development of many areas of technology makes nanophotonics a focus of interest for many researchers from different fields.
  • 474
  • 09 Feb 2022
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