Ultraviolet response

Devary, Y., Gottlieb, R.A., Smeal, T., Karin, M. (1992). The mammalian ultraviolet response is triggered by activation of Src tyrosine kinases. Cell 71, 1081-1091. 

The effect is easily achieved in the ion chromatography system where the preferred buffer solution (potassium hydrogen phthalate (5xlO 3M at pH 4.6) has a strong ultraviolet response with tanax at 280nm. At this... 

The response is greater for ultraviolet detection by a factor of 5-30. A relatively stronger, negative ultraviolet response occurs for weakly acidic anions because there is no dependence on their ionisation. 

The major limitation of both UV and MS detectors is that neither can provide quantitative or even semiquantitative information without reference standards. Ultraviolet response depends on the presence of a chromophore in a molecule and evidently might vary from one molecular species to another in a library. Although successful application of electrospray mass spectrometry for quantitative analysis of peptides has been reported [35], one should always keep in mind that signal intensity in a mass spectrum depends on the ability of a molecule to ionize. The ability to produce ions, especially with soft ionization techniques, might be very different for different molecules within one library, and the difference might be even bigger from one library to another. 

Figure 4.11 (a) Schematic illustration of a self-assembled monolayer of malachite green-terminated aUcanethiol (MG-CN-SH) with pH- and ultraviolet-responsive wetting properties, (b) Curves A and B represent the ideal model for two kinds of pH-responsive surfaces with completely different pH responses. 

Qiu, X., et al., 2011. The effects of temperature, relative humidity and reducing gases on the ultraviolet response of ZnO based film bulk acoustic-wave resonator. Sens. Actuators B 151 (2), 360-364. Available at http //linkinghub.elsevier.eom/retrieve/pii/S0925400510006544. 

Note that in liquid phase chromatography there are no detectors that are both sensitive and universal, that is, which respond linearly to solute concentration regardless of its chemical nature. In fact, the refractometer detects all solutes but it is not very sensitive its response depends evidently on the difference in refractive indices between solvent and solute whereas absorption and UV fluorescence methods respond only to aromatics, an advantage in numerous applications. Unfortunately, their coefficient of response (in ultraviolet, absorptivity is the term used) is highly variable among individual components. 

Application of the exact continuum analysis of dispersion forces requires significant calculations and the knowledge of the frequency spectmm of the material dielectric response over wavelengths X = 2irc/j/ around 10-10 nm. Because of these complications, it is common to assume that a primary absorption peak at one frequency in the ultraviolet, j/uv. dominates the dielectric spectrum of most materials. This leads to an expression for the dielectric response... 

Chromophore (Section 13 21) The structural unit of a mole cule principally responsible for absorption of radiation of a particular frequency a term usually applied to ultraviolet visible spectroscopy... 

An illustration of the technological significance of the relaxation phenomenon can be taken from photographic chemistry. Dyes of the cyanine class where Y = S, 0, CH—CH— n = 0,1,2,3...X = haUde, etc, are used as spectral sensitizers to extend photochemical response of the photographic silver hahdes, which only absorb blue and ultraviolet light, into the visible spectral regime. 

The most important hardware items appeared to be the detectors themselves. The gas detection system gave frequent spurious alarms, and on both platforms the ultraviolet (UV) fire detectors were also prone to spurious activation from distant hot work for example, and had a limited ability to detect real fires. The tmreliability of these systems had a general effect on response time and would, overall, lengthen the time to respond. The second aspect which was related to hardware was fimction and performance testing of the emergency blowdown systems. It is critical that the workers believe the systems will work when required, and this can only be achieved by occasional use or at least fimction testing. 

These combined HDF and GPC separations require the use of detectors such as static light scattering or viscometers to help sort out the convoluted elution profiles seen in those type of experiments. It should also be remembered in these situations that the typical refractive index or ultraviolet detector responses may not be representative of the actual mass fraction of insolubles eluting from the column because of the significant light scattering that can occur with those large particles in the detector cell. 

About 51 percent of solar energy incident at the top of the atmosphere reaches Earth s surface. Energetic solar ultraviolet radiation affects the chemistry of the atmosphere, especially the stratosphere where, through a series of photochemical reactions, it is responsible for the creation of ozone (O,). Ozone in the stratosphere absorbs most of the short-wave solar ultraviolet (UV) radiation, and some long-wave infrared radiation. Water vapor and carbon dioxide in the troposphere also absorb infrared radiation. 

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