UV dose

The UV dose required to reduce the survival fraction of total coliform and fecal streptococcus to 102 (99 percent removal) is approximately 4 x 10 ff Einsteins/ml. 

The contributions of Dr. R. R. Bidigare and M. E. Ondrusek to all aspects of the project, especially pigment analyses and calculations of UV doses, are gratefully acknowledged. This work was supported by the U.S. National Science Foundation, Division of Polar Programs (DPP-88-12972). 

Figure 15 Antiradical capacity of histidine (2 mmol/L) undergoing chemical (NaOCI) and physical (UV, 254 nm) oxidation in equivalent concentrations of ascorbic acid used as calibrator. For UV dose 1 = 60 s, dose 2 = 120 s. For NaOCI after 45 min of incubation with 16 (dose 1) or 32 (dose 2) mg/L NaOCI.

Another problem is degradation of the sensor due to the high UV dose. The radiation resistance of most photodiodes decreases with wavelengths. UV-enhanced Si photodiodes show a loss of 10% in sensitivity already after an accumulated dose of some hundred J/cm2 at X = 254 nm. This is the dose a sensor will have received over the lifetime of an Hg lamp. Special silicon nitride-protected photodiodes are stable up to 105 J/cm2. A filter combined with an attenuator may help to achieve the required selectivity and reduce the exposure of the detector. However, the radiation stability of the filter has to be guaranteed. 

Table XI. Role of UV Dose in Synergistic Effect of Acrylate and Methacrylate Monomers with Inorganic Salts(L) in Photografting Styrene to Polypropylene3...

The cytotoxic and photocytotoxic effects of two water-soluble fullerene derivatives, a dendritic CL mono-adduct and the malonic acid CL tris-adduct were tested on Jurkat cells when irradiated with UVA or UVB light (Rancan et al., 2002). The cell death was mainly caused by membrane damage and it was UV dose-dependent. Tris-malonic acid fullerene was found to be more phototoxic than the dendritic derivative. This result is in contrast to the singlet oxygen quantum yields determined for the two compounds. 

With decreasing UV dose T(tan 6niax) also decreases. When free monomer is still present additional polymerization causes a stepwise increase of E and T(tan max) during a thermal scan. In the presence of sufficient monomer the tan 6 peak splits up into two peaks one at a constant and the other at a dose-dependent position, representing monomer and network, respectively. 

Another important point is the method of assessing UV doses received by samples. 

The curing equipment will operate at the sufficient efficiency if a minimum UV dose (mj/cm ) or a minimum exposure time can be applied to obtain the desired degree of cure. This requires fhat the reactive binders and photoinitiator system match closely the emission spectrum of fhe UV source. 

In the past, electron beam radiation was applied to produce PSA exclusively however, recent improvements in UV curing technology (precise UV dose control, suitable photoinitiators) permit UV to be used to produce pressure-sensitive adhesives. PSA formulations can vary in consistency from low-viscosity liquids up to solids melting at 80°C (176°F). Therefore, applications may vary from screen printing to roll coating to melt extrusion. Coat weights for most PSA materials vary from 1 to 10 g/m. ... 

Some self-contained instruments are designed for on-line measurements in UV curing units to determine the integral UV dose delivered to the material being cured, peak irradiance, and irradiance/temperature profiles. The quantities and units of measurements have been established based on lUPAC s recommendation of 1996. These are listed in Table 9.3. 

Melt time, seconds Type of UV lamp UV dose, mJ/cm2... 

The space distribution of UV radiation in Italy, available through monthly UV dose maps, can be useful for epidemiology research in skin cancer and eye pathologies as well as in those studies dealing with the impact of UV on the biosphere. 

Well-resolved patterns with line widths of 1.0 xm were readily formed when a film of hb-P76 was exposed to a UV dose of 1 ]/cm2 (Fig. 12A). Patterns with submicron resolutions (line width down to 500 nm) were also achievable, as demonstrated by the examples given in panels B and C of Fig. 12. Clearly, hb-P76 is an excellent photoresist material. Similar to hb-PAAs, hb-PYs were also photosensitive. Well-resolved, defect-free pho-... 

As with chemical disinfection, the performance of UV irradiation systems (especially with 254-nm lamps) is determined by the disinfectant UV dose. In the case of solar disinfection of water, dose can then be calculated from the average solar UV intensity and the residence time in the irradiated part of the reactor dose = / x tr, where dose is the solar UV dose (Whm-2), I is the average intensity (W m-2), and t is the residence time (h). Note that only the UV part of the solar spectra is taken into account. 

In order to compare the effect of solar illumination applied at different seasons of the year (2003) and at different moments of the day, we calculated for each period the solar UV dose necessary to reach approximately 99.9900% of E. coli inactivation. As expected, the dose necessary to inactivate a similar quantity of bacteria is higher in the absence (37.28-43.74 Wm 2) than in the presence of Ti02 (17.204-23.720 Wm-2). 

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