Laser Photocoagulation Principles
John P. Papp in Endoscopie Control of Gastrointestinal Hemorrhage, 2019
where h is Plack’s constant, c is the speed of light, and ≈ is the wavelength. Thus, light of a particular wavelength may be viewed as a collection of photons of equal energy. By carefully noting (using absorption spectroscopy) which energy of photons are absorbed by a particular atom, the chemist is able to identify the atom under scrutiny because its “signature” is known. Likewise, the photons which an atom is capable of emitting are energetically related to its own particular quantum levels or energies. Spectroscopy which uses the emission signature of an atom is referred to as emission spectroscopy. Sometimes the emission is forced using a spark or flame in an atmosphere of the atom being tested. The emission of light by an atom can occur at any time provided it has a lower energy state which nature allows for it. The fact that the emission can occur at any time means that the scientist must use a statistical estimate of the likelihood of emission, rather than an absolute prediction of the occurrence. This kind of statistical emission is referred to as “spontaneous emission”.
Dictionary
Mario P. Iturralde in Dictionary and Handbook of Nuclear Medicine and Clinical Imaging, 1990
Atomic absorption spectroscopy. This is a method of chemical analysis where a flame photometer measures the absorption of particular wavelengths of light when passing through a flame in which atoms from metal salts (e.g., sodium and potassium) are being ionized. Small samples of body fluids are aspirated into a nebulizer and injected into a flame of propane or natural gas, or into a flameless electrothermal arc (e.g., carbon rod furnaces). Light is passed through the flame generated by a hollow cathode lamp lined with a coating of the metal to be analyzed. The characteristic spectral lines of the metal in question are radiated from the lamp and partially absorbed in the flame. A photometer detecting the radiation passing out of the flame can measure the quantity absorbed. Light emitted in the flame is separated from that absorbed, by pulsing the light source.
EM behavior when the wavelength is about the same size as the object
James R. Nagel, Cynthia M. Furse, Douglas A. Christensen, Carl H. Durney in Basic Introduction to Bioelectromagnetics, 2018
Spectrum analyzers are another way to measure the power in the mid-frequency band. A spectrum analyzer is connected to an antenna or waveguide to receive electric or magnetic fields and record the power as a function of frequency over a broad range. The spectrum of the power (how much power is at each frequency component) is displayed on a screen as well as stored digitally for output and further processing. Spectrum analyzers therefore distinguish one frequency from another (but do not usually measure the phase of each frequency component). Spectroscopy is an analysis of the power spectrum of a signal. Resonant frequencies display high power (indicating the presence of an element with that resonance), and nonresonant frequencies have lower power. Spectrum analyzers can be purchased for frequencies up to several tens of gigahertz today. They are much more expensive than power meters, because they can make more sophisticated measurements and usually have a wider frequency range. Virtually all spectrum analyzers have 50-ohm input impedance.
Human tear fluid analysis for clinical applications: progress and prospects
Published in Expert Review of Molecular Diagnostics, 2021
Sphurti S Adigal, Alisha Rizvi, Nidheesh V. Rayaroth, Reena V John, Ajayakumar Barik, Sulatha Bhandari, Sajan D George, Jijo Lukose, Vasudevan. B. Kartha, Santhosh Chidangil
In view of the research methodologies being employed at present, some pertinent procedures can be considered for further research and development. The three technologies being pursued at present, in increasing complexity, cost of equipment and expertise required, can be put in the order (i) optical spectroscopy (absorption, fluorescence, scattering), (ii) separation methods (HPLC/UPLC/SDS-PAGE) and mass spectroscopy, followed by (iii) hyphenated methods. It is thus appropriate to think how these three technologies can be coordinated. A suitable modus operandi can be: carry out universal screening using the optical spectroscopy technique, since it needs only trained technicians, can be coupled to automatic data processing to give objective conclusions, requires miniature portable/hand-held equipment only, and above all, preserves the same sample for further tests if warranted. Cases diagnosed as abnormal can then be sent for HPLC/UPLC studies, and if desired, or in case the specific marker identities will be useful for therapy planning and decision making, MS-dependent separation techniques can be used. Such a coordinated procedure will be most helpful for universal healthcare, especially, under low-resource settings.
Scanning electron microscopy in analysis of urinary stones
Published in Scandinavian Journal of Clinical and Laboratory Investigation, 2019
Martin Racek, Jaroslav Racek, Ivana Hupáková
Chemical characteristics of materials including kidney stones can be also achieved with X-ray spectroscopy analytical methods. The use of these methods requires primary irradiation of the sample, which leads to ejection of electrons from the sample atoms. The resulting unstable state leads to an effect where the hole is filled by an electron from a higher orbital. The difference of the energy is balanced by a release of a photon with energy/wavelength characteristic for a given element. The characteristic X-rays emission can be reached in various ways, which is determinative for each method. The sample may be irradiated by high-energy protons (PIXE [47,48]), high-energy electrons (coupled with SEM, [29,35,38]) or primary X-rays (XRF [47–50]). The emitted X-rays can then be characterized based on their energy (energy-dispersive spectroscopy [EDS]) or wavelength (wavelength-dispersive spectroscopy [WDS]).
New Multi-Walled carbon nanotube of industrial interest induce cell death in murine fibroblast cells
Published in Toxicology Mechanisms and Methods, 2021
Krissia Franco de Godoy, Joice Margareth de Almeida Rodolpho, Patricia Brassolatti, Bruna Dias de Lima Fragelli, Cynthia Aparecida de Castro, Marcelo Assis, Juliana Cancino Bernardi, Ricardo de Oliveira Correia, Yulli Roxenne Albuquerque, Carlos Speglich, Elson Longo, Fernanda de Freitas Anibal
The absorption and fluorescence spectroscopy of OCNT-TEPA is shown in Figure 3. In absorption spectroscopy, the spectrometer casts a beam of light into the cuvette, collects the remaining light on the other side, so that we can see which wavelengths were absorbed or not at a given wavelength. This analysis then becomes important considering the objective of checking the fluorescence of OCNT-TEPA, since to understand the fluorescence spectrum it is also necessary to understand the absorption spectrum. In the absorption spectra we observed that the cuvette and the water remain as a baseline, but analyzing the OCNT-TEPA, we observed the scattering of the absorption light, with no peak or absorption bands in this range (400–800 nm) which is in agreement with this class of nanomaterial (Figure 3(a)) (Shetty et al. 2009; Yang et al. 2016). Analyzing the various concentrations of the OCNT-TEPA nanoparticle, we observed that the fluorescence curve pattern did not change compared with water. At higher concentrations the spectrum decreases their signal due to greater scattering of light that OCNT-TEPA can induce, decreasing the fluorescence emission signal (Figure 3(b)).
Related Knowledge Centers
- Chemistry
- Color
- Molecule
- Physical Chemistry
- Spectrophotometry
- Tissue
- Medical Imaging
- Optical Spectrometer
- Spectrum Analyzer
- Hydrogen