Lag-time

In practice, colloidal systems do not always reach tlie predicted equilibrium state, which is observed here for tlie case of narrow attractions. On increasing tlie polymer concentration, a fluid-crystal phase separation may be induced, but at higher concentration crystallization is arrested and amorjihous gels have been found to fonn instead [101, 102]. Close to the phase boundary, transient gels were observed, in which phase separation proceeded after a lag time. 

Environmental Aspects. Airborne particulate matter (187) and aerosol (188) samples from around the world have been found to contain a variety of organic monocarboxyhc and dicarboxyhc acids, including adipic acid. Traces of the acid found ia southern California air were related both to automobile exhaust emission (189) and, iadirecfly, to cyclohexene as a secondary aerosol precursor (via ozonolysis) (190). Dibasic acids (eg, succinic acid) have been found even ia such unlikely sources as the Murchison meteorite (191). PubHc health standards for adipic acid contamination of reservoir waters were evaluated with respect to toxicity, odor, taste, transparency, foam, and other criteria (192). BiodegradabiUty of adipic acid solutions was also evaluated with respect to BOD/theoretical oxygen demand ratio, rate, lag time, and other factors (193). 

When fouling occurs, even mechanical cleaning does not remove all traces of the bio film. Previously fouled and cleaned surfaces are more rapidly colonized than new surfaces. Residual biofilm materials promote colonization and reduce the lag time before significant fouling reappears. 

First-Order Lag (Time Constant Element) Next consider the system to be the tank itself. A dynamic mass balance on the tank gives ... 

When a flocculated feed is added to a filter tank, there is a definite time lag before this material reaches the surface of the filter medium. Since this lag time is not known at the time of testing, a lag time of 8 to 10 minutes should be allowed before starting the first leaf test on a flocculated shiny. Two, or perhaps three, tests can be run before the elapsed time exceeds the probable retention time in the full-scale filter tank. With knowledge of the elapsed time after flocculation and data relating to the rate of degradation, the rates obtained on the leaf test runs can be adjusted to some constant lag time consistent with the anticipated full-sc e design. 

Manual sampling/ analysis is part of control scheme resulting in a large lag time in determining when to proceed and what to do (heat/cool, etc.). 

Remember that ordinary pneumatie eontrol instrumentation ean have an appreeiable lag time, therefore, valve aetion probably will not start for 3 see. 

Lag time The time interval between a step change in input concentration and the first observable corresponding change in response. 

Equipment operating schedules Confirm that the timing of occupied and unoccupied cycles is compatible with actual occupied periods, and that the building is flushed by the ventilation system before occupants arrive. ASHRAE 62-1989 provides guidance on lead and lag times for HVAC equipment. In hot, humid climates, ventilation may be needed during long unoccupied periods to prevent mold grow th. 

The recommended initial step is to determine the duration of the study period for the analysis by first defining a start date. The end date is determined by the maintenance records. For computerized systems, the last update of the overall system provides the end date. For manual systems, it may be necessary to define an end date to accommodate the lag time in updating records. The start and end dates define the maximum calendar time that a piece of equipment is available for service. The operating time for this equipment will be equal to or less than the calendar period, depending on plant operations and the equipment s operating mode. 

The project of communicating new technology to processors and users is the subject of much discussion in the industry. The lag time from laboratory discovery to end user benefits is generally three years or more. 

Manche and Carroll [1253] suggest that errors due to lag time at the onset of reaction can be avoided by using rates at fixed values of a in the determination of E values. 

Therefore, full-face phenol-based peel should always be performed under full cardiopulmonary monitoring. The average lag time for the onset of the arrhythmias was 17.5 min from the beginning of the peel, and they are usually not delayed for more than 30 min after the peel. Cardiac arrhythmias are more common while applying the solution on the thin skin of eyelids. In this area skin absorption is maximal therefore, application should be performed extremely cautiously. If arrhythmia occurs, the application of phenol should be stopped until... 

Owing to the lag time between initiation and effect, capsaicin is not used for treatment of acute pain from injury. Instead, topical capsaicin is used for chronic pain from musculoskeletal and neuropathic disorders. Capsaicin preparations have been studied in the treatment of pain from diabetic neuropathy, osteoarthritis, rheumatoid arthritis, postherpetic neuralgia, and other disorders.48 It is often used as an adjuvant to systemic analgesics in these chronic pain conditions. 

The lag time is the intercept that results by extrapolating the steady-state line of a plot of cumulative amount of drug penetrated versus time to the time axis. 

Fig. 4 Generalized permeation profile. From left to right the data are for n-butanol permeating hairless mouse skin at 20°, 25°, and 30° C respectively. Increasing temperature raises the flux (slope) and shortens the lag time. 

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