Threshold, exceeded

Days with Threshold Exceedance Jun-Aug Difference 2031/2039 - 1991/2000 uv20... 

It was shown that for semiconductor lasers based on InGaN/GaN heterostructures, at optical excitation by the laser pulses of the femtosecond duration ( 150fs) the laser threshold exceed 2 0 GW/cm. It is caused most probably by non-steady excitation conditions. FWHM of the laser spectra alters from 13 to 25 nm. Amplification occurs in a wide interval of 60-80 nm and the gain at maximum reaches 85-153 cm . 

The Lanphear et al. s (1998) analysis of 12 pooled studies of dust and soil Pb relationships to yoimg children s PbB value was described in the previous chapter in terms of modeled estimates of PbB mean values, given changes in interior dust Pb loadings (fig/ft ) and exterior (soil plus exterior surface Pb) Pb concentrations (ppm). Here, the analysis is extended to estimates of percentage of PbB exceeding two health risk thresholds, >10 and sl5 p.g/dl. These health risk threshold exceedances parallel the approach used in the case study for the smelter Superfund site in the Silver Valley of Idaho. 

Compliance embedded in day-to-day activities Key risk indicators with established limits, monitoring of safety risk within limits, corrective actions when thresholds exceeded Leadership and managers demonstrate safety Staff support safety daOy Blame-free culture Safety focus on creating value to business units at a competitive price... 

We noted above that the presence of monomer with a functionality greater than 2 results in branched polymer chains. This in turn produces a three-dimensional network of polymer under certain circumstances. The solubility and mechanical behavior of such materials depend critically on whether the extent of polymerization is above or below the threshold for the formation of this network. The threshold is described as the gel point, since the reaction mixture sets up or gels at this point. We have previously introduced the term thermosetting to describe these cross-linked polymeric materials. Because their mechanical properties are largely unaffected by temperature variations-in contrast to thermoplastic materials which become more fluid on heating-step-growth polymers that exceed the gel point are widely used as engineering materials. 

An even wider range of wavelength, toward the infrared, can be covered with quantum well lasers. In the Al Ga As system, compressively strained wells of Ga In As are used. This ternary system is indicated in Figure 6 by the line joining GaAs and In As. In most cases the A1 fraction is quite small, X < 0.2. Such wells are under compressive strain and their thickness must be carefully controlled in order not to exceed the critical layer thickness. Lasers prepared in this way are characterized by unusually low threshold current density, as low as ca 50 A/cm (l )-... 

Health and Safety Factors. Terephthahc acid has a low order of toxicity. Inhalation by rats for 6 h/d, 5 d/wk for 4 wk produced no fatahties at a dust exposure level of 25 mg/m. The mean acute oral toxicity for rats is over 18 g/kg (86), and for mice over 6 g/kg (87). When terephthahc acid was fed as 3% of the diet to rats, urinary calcuh formed in 90 d, some of which led to cancer. High doses of terephthahc acid lead to formation of calcium terephthalate at levels exceeding its solubihty in urine. This insoluble material leads to the calcuh and provides a threshold below which cancer is not observed (88). Normal precautions used in handling industrial chemicals should be observed with terephthahc acid. If ventilation is inadequate, a toxic-dust respirator should be used to avoid prolonged exposure. 

Because pulp bleaching agents are, for the most part, reactive oxidising agents, appropriate precautions must be taken in their handling and use. For example, it is important to ensure that the threshold limit values (TLV) (20) in Table 2 are not exceeded in the workplace air. These are airborne concentrations in either parts per million by volume under standard ambient conditions or mg per cubic meter of air. They "represent conditions under which it is beUeved that nearly all workers may be repeatedly exposed, day after day, without adverse effect" (20). TWA refers to a time-weighted average for an 8-h workday STEL is a short-term exposure limit or maximum allowable concentration to which workers can be continuously exposed for 15 minutes. 

TLV means threshold limit value (estabhshed by the American Conference of Government Industrial Hygienists, or ACGIH). TLV-C is the concentration in air that should not be exceeded during any pari of the working exposure. 

Silicon diodes have a very high internal resistance on loading in the transmission direction up to their threshold voltage of about -1-0.7 V. If the threshold voltage is exceeded, the internal resistance decreases. With a nonsymmetrical... 

None of the foregoing methods will tell the frequency or duration of exposure of any receptor to irritant or odorous gases when each such exposure may exceed the irritation or odor response threshold for only minutes or seconds. The only way that such an exposure can be measured instrumentally is by an essentially continuous monitoring instrument, the record from which will yield not only this kind of information but also all the information required to assess hourly, daUy, monthly, and annual phenomena. Continuous monitoring techniques may be used at a particular location or involve remote sensing techniques. 

TLV-c, THRESHOLD LIMIT VALUE - CEILING (usa) A limit fof the atmosplieiic concentration of a chemical which may not be exceeded at any time, even instantaneously in workroom air. 

The early concept was that these were values which must not be exceeded in other words, they were truly maximum values. As the understanding of limits and the development of the philosophy for such limits grew, it was realized that short-term exposures to somewhat higher concentrations could be permitted without undue harm if the total exposure during the day was sufficiently below the maximum limit. This led to the development of the concept of Threshold Limit Values (TLV s) by the ACGIH. 

Major Source a stationary facility that emits a regulated pollutant in an amount exceeding the threshold level (100 or 250 tons per year, depending on the type of facility). See also source. 

A serious exposure may also result from a small, single dose over a short period of time and there is no immediate effect. This small dose may exceed t e threshold sensitivity of the individual causing a serious delayed effect. The classic exeimple of this is cancer. 

Section 313 reporting Is required If threshold quantities are exceeded. The thresholds vary depending upon the year for which the report Is submitted and separate thresholds apply to the amount of the chemical that is manufactured, processed, or otherwise used. 

Step 3 involves subtracting the result of Step 2 from the results of Step 1 for each activity. Compare this net sum to the applicable activity threshold. If the threshold is met or exceeded for any of the three activities, your facility must submit a Form R for that chemical or chemical category. This worksheet should be retained In either case, to document your determination for reporting or not reporting. Do not submit this worksheet, or any other calculations, with your Form R report. Retain the worksheet for your records. 

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