Subject annual frequency

Surface Chemistry. The schedule of sample exposure during the first year of the test program was as follows for each three-month period, briquettes were exposed in racks and then replaced with fresh samples for the following three-month period. An additional set of briquettes was exposed for the entire year, and other samples present in the racks are part of a planned multiyear exposure program. Quarterly withdrawals for chemical analysis are to be made for two years, after which a cumulative annual frequency is to be maintained. One set of samples is continuously exposed for posterity or for unforeseen developments. Three samples of each stone type are employed in each cycle of tests. The plan is subject to change in the light of analysis results as they are produced. 

The period under review has seen a small, but apparently real, decrease in the annual number of publications in the field of the vibrational spectroscopy of transition metal carbonyls. Perhaps more important, and not unrelated, has been the change in perspective of the subject over the last few years. Although it continues to be widely used, the emphasis has moved from the simple method of v(CO) vibrational analysis first proposed by Cotton and Kraihanzel2 which itself is derived from an earlier model4 to more accurate analyses. One of the attractions of the Cotton-Kraihanzel model is its economy of parameters, making it appropriate if under-determination is to be avoided. Two developments have changed this situation. Firstly, the widespread availability of Raman facilities has made observable frequencies which previously were either only indirectly or uncertainly available. Not unfrequently, however, these additional Raman data have been obtained from studies on crystalline samples, a procedure which, in view of the additional spectral features which can occur with crystalline solids (vide infra), must be regarded as questionable. The second source of new information has been studies on isotopically-labelled species. 

Most HPLC systems in pharmaceutical laboratories are calibrated every 6-12 months. Periods longer than 12 months are not recommended while periods shorter than 3 months are deemed unnecessary because each HPLC system is also subjected to a daily system suitability check to ensure sufficiency for the application. Ideally, the frequency of calibration should be dictated by the historical data of calibration failures and the manufacturer s recommendation. In practice, 6 months appears to be the norm adopted by most laboratories. Calibration is also required after annual preventive maintenance or major repairs though only the affected modules, and not the entire system, need to be recalibrated. 

The HSE/IS produces annually a list of over 1600 titles taken within its Information Service entitled Health and Safety Executive Information Service Current Periodicals List . This lists the current title, former title(s), and frequency of publication. A companion volume entitled Subject Index to the HSE Current Periodical List gives under an alphabetical subject heading a list of relevant magazines. Both are available free of charge from the Health and Safety Executive, Information Centre, Broad Lane, Sheffield S3 7HQ, England. 

Perhaps varying the frequency of certain sections of the physical makes sense for your organization. X-rays were mentioned previously. Does your medical provider feel that X-rays should be given to all workers of all ages annually There are a variety of views on this subject. Some physicians believe that the amount of radiation workers are exposed to should be limited as much as possible, especially for workers under 40. The Nuclear Regulatory Commission has different amounts of allowable radiation depending on age. 

Some insights into membrane failure can be found in the literature (Childress et al., 2005 Gijsbertsen et al., 2006). The frequency of failure will depend on applications, but Gijsbertsen et al. (2006) estimate annual rates in water treatment of 1-10 per million fibers. Higher rates would be anticipated in MBRs where membranes are subject to more fouling conditions and greater operational stresses. Even flat-sheet membranes used in MBRs are not immune to occasional failure (Cornel and Krause, 2003). 

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