Two-step exposure

To reduce or to take into account the effect of the ambient atmosphere and other experimental factors, we used the heavier hydrogen isotope, deuterium, in this study. SWNTs deuterated under the final pressure of 5 GPa during a two-step exposure at T = 350°C for 21 h and at T = 460-490°C for 9 h. According to the data of two combustion tests, deuterated SWNT contained 10.8 0.1 wt% D. 

Procedure One step exposure Mostly two step exposure... 

We fabricated an LC grating using a two-step exposure method with a line-and-space patterned photomask. The PLCP consisted of a methacrylate group with mesogenic 4-(4-methoxycinnamoyloxy)biphenyl side groups and nonmesogenic Wphenylmaleimide (PI). The chemical structure and synthesis procedure of PI was previously reported (Kawatsuki et al. 2004). PI has a nematic LC phase between 89 and 298 °C. Figure 9.1a shows the fabrication process and the structure... 

Fig. 9.1 The structure of the LC grating that was fabricated using a two-step exposure method and a diffraction pattern of the LC grating (a) the fabrication process. E is the polarization direction of the LP UV light. The rods and circles show the direction of the orientation (b) POM images. The arrows show the transmission axes of the polarizer and analyzer, (c) a diffraction pattern. The diffraction pattern was observed by removing the 0th order beam...

Fig. 9.2 The polarization states of the beams diffracted from the LC grating that was fabricated using the two-step exposure method. The probe beam was incident on (a) film A or (b) film B. The polarization azimuth angle of the LP probe beam was 0°, 45°, or 90°. The filled circles show the experimental results and solid lines show the calculated results...

In summary, using a two-step exposure method with a line-and-space photomask we fabricated an LC grating inner coated with PLCP photoalignment films. The diffraction efficiencies and the unique polarization conversion properties of the LC grating were well explained based on the simple binary model involving planar and TN alignments, the Jones matrix method, and diffraction theory. 

There are two steps required to detennine whetlier risks or haaird indices for two or more pathways should be combined for a single exposed individual or group of individuals. The first is to identify reasonable exposure pathway combinations. The second is to examine whcUier it is likely that the same individiuils would consistently face the "reasonable ma.ximum exposure (RME) by more than one pathway. 

The synthesis of the right-wing sector, compound 4, commences with the prochiral diol 26 (see Scheme 4). The latter substance is known and can be conveniently prepared in two steps from diethyl malonate via C-allylation, followed by reduction of the two ethoxy-carbonyl functions. Exposure of 26 to benzaldehyde and a catalytic amount of camphorsulfonic acid (CSA) under dehydrating conditions accomplishes the simultaneous protection of both hydroxyl groups in the form of a benzylidene acetal (see intermediate 32, Scheme 4). Interestingly, when benzylidene acetal 32 is treated with lithium aluminum hydride and aluminum trichloride (1 4) in ether at 25 °C, a Lewis acid induced reduction takes place to give... 

When determining the impact of a stressor using this approach, there are two main steps, exposure assessment and hazard assessment [28]. The exposure assessment is aimed to determine the concentrations of a substance that a certain organism can be exposed to due to the emission of a certain amount of a substance. The first step is the release estimation. The release estimation aims to determine how much of... 

Sometimes orthogonal offline SPE steps were used prior to online SPE LC/MS/MS. These preparation steps were used to remove interference and concentrate samples. In an application to measure urinary N7-(benzo[a]pyren-6-yl)guanine (BP-6-N7Gua), a biomarker for exposure to polyaromatic hydrocarbons (PAHs), a two-step offline SPE was first performed using Sep-Pak C8 (Waters, Milford, Massachusetts) and Strata SCX (Phenomenex, Torrance, California) cartridges to obtain high sensitivity (Chen et al. 2005). The extracts were applied to an online reversed phase SPE LC/MS system. The lower limit of detection was 2.5 fmol/mL when 10 mL of urine was used. 

Compound 51 was found to be unstable and difficult to purify, as described in the literature [93—95]. Therefore, 51 was not isolated, but was instead converted to the stable pinacol 1-acetamido-l-hexylboronate derivative 52. However, the acylated derivative 52 could not be purified by column chromatography as it was destroyed on silica gel and partially decomposed on alumina. Fortunately, we found that it dissolves in basic aqueous solution (pH > 11) and can then be extracted into diethyl ether when the pH of the aqueous layer is 5—6. Finally, pure 52 was obtained by repeated washing with weak acids and bases. It should be mentioned here that exposure to a strongly acidic solution, which also dissolves compound 51, results in its decomposition. Compared with other routes, the present two-step method involves mild reaction conditions (THF, ambient temperature) and a simple work-up procedure. It should prove very useful in providing an alternative access to a-aminoboronic esters, an important class of inhibitors of serine proteases. 

The exact mechanism by which chemical exposures cause MCS is unknown. It is believed that a two-step process occurs. First, an initial exposure or chronic exposures interacts with a susceptible individual, leading to loss of that person s prior, natural tolerance for everyday, low-level chemicals, as well as certain foods, drugs, alcohol, and caffeine. In the second stage, symptoms are thereafter triggered by extremely low doses of previously tolerated products and exposures.2 This theory is called toxicant-induced loss of tolerance or TILT. 3... 

Thus two components, exposure and hazard, must be evaluated together in determining the level of risk posed by a given colorant or other chemical. Risk management may therefore be regarded as a series of interdependent steps ... 

Two repeated exposures of resin 38 to the catalyst (9% mol) for 18 h in dichloromethane at room temperature afforded the expected allyl lactoside in an encouraging isolated yield of 81% from resin 35 (90% per step). Traces of dimerized compounds resulting from cross-metathesis were detected as the only side products. Extension of the oligosaccharide chain was subsequently performed first by deacetylation (excess NaOMe in 4/1 CH2Cl2/MeOH at r.t.) and glycosylation with known lactosyl donor 40 in conditions similar to those mentioned above. Cleavage was performed twice as described above, but with a reduced reaction time of 6 h in this case tetrasaccharide 42 was isolated in 51% yield from 35 (84% per step). No dimerized products were detected. 

We also note two reports on the degradation of stacked films of oriented PET. In the first [36], photodegradation is said to be two-step in nature with weak links cleaving first followed by a much slower cleaving of the strong links . The chain scission process was tracked versus exposure time by measurement of solution viscosity [37], In the second paper [38], the surface nature of the degradation was reported and the rationale elucidated for why surface degradation causes overall mechanical failure limited by that layer, much as we have discussed in the impact properties of the PECT (see above). 

Those crystalline salicylideneanilines that are not thermochromic are photo-chromic that is, they undergo a reversible color change on exposure to light. In these materials the molecules are markedly nonplanar (45b see discussion on biphenyls in Section II-D) and the crystal structures are very open. It has been suggested that the color change here is due to a two-step process (102) ... 

The coatings were cured in two steps first, a room temperature exposure for at least five hours to allow any solvent present to evaporate and/or the resin to gel and, second, an elevated temperature cure. The vinyl ester, polyester and epoxies were baked at 60°C for 4-16 hours. The coating thickness after curing was measured with a micrometer, subtracting the substrate thickness. The thickness of the coatings ranged from 6 to 12 mils (150-300 urn) and is shown for each type in Table I. 

Cancer risk assessment is basically a two-step procedure, involving a qualitative assessment of how likely it is that a compound is a human carcinogen, and a quantitative assessment of the cancer risk that is likely to occur at given exposure levels and duration of exposure. 

Dose-response assessment today is generally performed in two steps (1) assessment of observed data to derive a dose descriptor as a point of departure and (2) extrapolation to lower dose levels for the mmor type under consideration. The extrapolation is based on extension of a biologically based model (see Section 6.2.1) if supported by substantial data. Otherwise, default approaches that are consistent with current understanding of mode of action of the agent can be applied, including approaches that assume linearity or nonlinearity of the dose-response relationship, or both. The default approach is to extend a straight line to the human exposure doses. 

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