Nitrogen threshold value

Of the few known terpene compounds that contain heteroatoms such as nitrogen or sulfur, the thiol 8-mercapto-p-menthan-3-one described below has qualitatively important applications as a fragrance and flavor substance. The second thiol, -p-menthene-8-thiol, is described because its odor threshold value is far lower than that of most other fragrance and flavor materials. 

Many nitrogen- and sulfur-containing heterocycles have been identified in the aroma fractions of foods [214]. In roasted products (e.g., coffee) and heat-treated foods (e.g., baked bread or fried meat), these heterocycles are formed from reducing sugars and simple or sulfur-containing amino acids by means of Maillard reactions [215, 216]. Their odor threshold values are often extremely low and even minute amounts may significantly contribute to the aroma quality of many products [217, 218]. Therefore, N- and N,S-heterocyclic fragrance and flavor substances are produced in far smaller quantities than most of the products previously described. 

In 1989, Chao [2] reported that LiLSX (lithium ion-exchanged low silica X zeolite, having a Si/Al ratio close to I.O) showed an unexpected high capacitiy and selectivity for nitrogen over oxygen. He found a Li exchange threshold value in LiNaLSX at about 2/3. Below... 

As mentioned above, Li content in LiNaLSX showed a threshold value at about 2/3, above which the nitrogen adsorption capacity increased rapidly [10], as shown in Fig.3 (a). Ca exchanged LSX can also be a good adsorbent for N2 [7]. We noticed that N2 adsorption capacity of CaNaLSX as a function of Ca exchange degree gives a threshold value at 31% (about 1/3) [7], different from that of LiNaLSX, as shown in Fig.3 (b). 

In general, sulfur- or nitrogen-containing compounds and heterocyclic compounds have very low threshold values. 

An important parameter that strongly correlates with membrane permeability is polar surface area (PSA) - a sum of van der Waals surface areas of polar atoms (oxygens and nitrogens).Multiple studies " have found an upper PSA threshold value of —140-150 for oral absorption. Similarly, for blood-brain barrier penetration, the upper PSA threshold is —90A (Figure 12.1). Recently, fast algorithms for PSA calculation have been suggested that do not need a... 

When NOx concentration exceeds the threshold value of about 0.1%, the atomic oxygen reactions with nitrogen oxides, (6-74) and (6-75), become faster than their reactions with molecular oxygen (6-66) to form ozone. That actually explains the discharge poisoiung effect, which was first observed long ago by Andrews and Tait (1860). Even ozone molecules... 

Through EU legislation, major air pollutants have been regulated. For example, through an EU Directive (EC 1999), the EU has estabhshed limit values for concentrations of sulfur dioxide, nitrogen dioxide and nitrogen oxides, particulate matter and lead, as well as alert thresholds for concentrations of sulfur dioxide and nitrogen oxide, in ambient air. Member States must take the measures necessary to ensure that concentrations of the pollutants in ambient air do not exceed the limit values. 

Hoskins and Soffer (117) measured the fluorescent lifetime of the neodymium 4Fy2 state in yttrium oxide. They found a value of approximately 260 /zsec both at room temperature and at liquid-nitrogen temperature. They also observed a weaker long-lived component in the decay. They were unable to say whether this was evidence for a low-transition-probability ion site, or an effect of trapping of the resonance radiation near 0.9 /x. They report laser action, with a threshold of 260joules. This is a fairly high value for most crystalline materials. 

When the threshold stability has been attained, further boiling does not improve the nitrocellulose any more and the gradient An/Af at any temperature is dependent on the nitrogen value of the nitrocellulose (Fig. 113). 

Nitrogen dioxide (NO2) is a brownish irritant gas sometimes associated with fires. It is formed also from fresh silage exposure of farmers to NO2 in the confines of a silo can lead to silo-filler s disease. The 1999-2000 threshold limit values are shown in Table 57-1. 

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