Irradiance, laboratory-accelerated

Since the early 2000s, different sources of CO have been explored and applied to carbonylation reactions for laboratory organic synthesis. For example, the use a stoichiometric amount of metal-carbonyl complexes, thermolysis of formic acid at high temperature, and the use of aldehydes via decarbonylation have been investigated. For the use of metal-carbonyl complexes and formaldehyde as carbonyl source, it has been shown that microwave irradiation greatly accelerates the process. ... 

T n 1962 the U. S. Army opened at its Natick Laboratories in Natick, Mass., the world s largest irradiation laboratory (2) for preserving foods by ionizing energy (Figure 1). This laboratory is unique in that, in addition to having two radiation sources, a 24-m.e.v., 18-kw. electron linear accelerator and a 1,250,000-curie cobalt-60 isotope source, it includes a food development-preparation laboratory and an experimental development kitchen (Figure 2). 

Acceleration factors are material dependent and can be significantly different for each material and for different formulations of the same material. Therefore, it is erroneous to attempt to establish a single acceleration factor for a laboratory accelerated test to be used to predict lifetimes under natural weather conditions for a variety of materials and formulations. Because of the complex nature of the interaction of the combined weather stresses with a material, there is presently no simple way to estimate the acceleration factor for a material. Increase in irradiance cannot be equated with acceleration of degradation. For most polymeric materials, the rate of degradation is not simply a linear function of the level of irradiance. Also, it does not take into account the effect of temperature, moisture, and other weather factors. Thus, there is no substitute for determining the acceleration factor for a given material experimentally. 

In many modern laboratory accelerated test devices, the irradiance in watts per square meter (W/m ) in a specified spectral range is photometrically monitored and the lamp power is automatically adjusted to maintain constant irradiance. In xenon arc devices, it is commonly controlled at either 340 nm, referred to as narrow band control or over the full uv, 300-400 nm, referred to as broad... 

Bis(tributyltin) oxide is known to break down to inorganic tin under UV irradiation in laboratory conditions (509, 510), and the decomposition may be accelerated by absorbing the organotin compound on a cel-lulosic matrix (511). As bis(tributyltin) oxide is known to react rapidly with carbon dioxide (atmospheric, or trapped in various cellulosic materials, such as cotton or wood) (512), to form bis(tributyltin) carbonate, (BusSnO)2CO, the observed UV degradation pattern may be rationalized in terms of more-ready breakdown of the carbonate than of the oxide, due to the presence of the carbonyl chromophore. The half-life of bis(tributyltin) oxide in pond water has recently been given as 16 days (513). Diorganotin compounds have also been shown to decompose to inorganic tin under UV irradiation (514, 515). 

Based on the photoelectric effect, electrons in evacuated tubes (photoelectrons) are released from a metal surface if it is irradiated with photons of sufficient quantum energy. These are simple photocells. Photomultipliers are more sophisticated and used in modem spectrophotometers where, via high voltage, the photoelectrons are accelerated to another electrode (dynode) where one electron releases several electrons more, and by repetition up to more than ten times a signal amplification on the order of 10 can be obtained. This means that one photon finally achieves the release of 10 electrons from the anode, which easily can be measured as an electric current. The sensitivity of such a photomultiplier resembles the sensitivity of the human eye adapted to darkness. The devices described are mainly used in laboratory-bound spectrophotometers. 

The instrument MIMOS 11 is extremely miniaturized compared to standard laboratory Mossbauer spectrometers and is optimized for low power consumption and high detection efficiency (see Sect. 3.3) and [326, 327, 336-339]. All components were selected to withstand high acceleration forces and shocks, temperature variations over the Martian diurnal cycle, and cosmic ray irradiation. Mossbauer measurements can be done during day and night covering the whole diurnal temperature... 

Any dosimeter used to determine absorbed dose in an irradiated product has to be calibrated. The adiabatic character of electron beam deposition is used in calorimetry, which is the primary absolute method of measuring the absorbed dose (energy per unit mass). An example of the instrument for this purpose is the water calorimeter developed in Ris0 National Laboratory in Denmark. " This calorimeter is reported to be suitable for electrons from a linear accelerator with energies higher than 5 MeV and... 

The hydrated electron may well find use in analytical chemistry laboratories. Not only have we shown that e aq is a valuable species for measuring submicromolar concentrations of its scavengers, but we have also demonstrated that satisfactory results may be obtained by very feeble x-ray pulses. While we irradiated our samples with 16 m.e.v. electrons or x-rays from a linear accelerator, an inexpensive pulsed x-ray unit of 150-200 k.e.v., capable of delivering 1 to 2 r/pulse, should serve equally well. Furthermore only minimal shielding is required under these conditions, thereby greatly facilitating manipulations needed for carrying out routine analyses. 

The somatic mutation theory is based, in part, on the idea that background radiation and/or various endogenous mutagens produce random chromosome damage in all cells. Over time, the genetic loci become sufficiently altered such that various critical functions fail and the cell dies. The fact that irradiation of laboratory animals results in accelerated aging and premature death lends some support to this hypothesis. However, since irradiation produces free radicals, it could be considered part of that theory. 

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