Dark phase

Aldehydes are important because they are temporary reservoirs of free radicals (see eqs. 11 and 12). HCHO is a known carcinogen. Nitric acid is formed by OH attack on NO2 and by a dark-phase series of reactions initiated by O3 + NO2. Nitric acid is important because it is the second most abundant acid in precipitation. In addition, in southern California it is the major cause of acid fog. 

Fig. 9. Transmission electron photomicrographs of HIPS where the dark phase is OsO -stained mbber (218).

Figure 11 Polarized microscope photographs ( x 800) (A) PBT-TLCP-elastomer blend (60 25 15 wt ratio). Dark phase is the TLCP phase. (B) Nylon 6-TLCP-elastomer blend (60 25 15 wt ratio). Dark phase is the TLCP phase and large white one is the elastomer phase. Source Ref. 56.

Kantor, S., Jakus, R., Bodizs, R., Halasz, P. Bagdy, G. (2002). Acute and long-term effects of the 5-HT2 receptor antagonist ritanserin on EEG power spectra, motor acivity, and sleep changes at the light-dark phase shift. Brain Res. 943, 105-11. 

Figure 15.6 The mean hourly distribution of wakefulness time (min/h) in orexin/ataxin-3 rats and wild-type littermates. Although over the 24 h period there is little total difference in the time spent in wakefulness, it is evident that the transgenic rats spend less time awake during the dark phase, which is denoted by the horizontal bar, especially at the photoperiod boundaries. Note, in particular, the difference at the end of the dark phase. The latter corresponds to a time of maximum orexin levels in the rat, and may be related to a circadian wakefulness signal. Asterisks designate those hours with a significant difference in wakefulness times between the genotypes (p < 0.05). Adapted from Beuckmann et al. (2004).

Sleepiness in narcolepsy has also been considered a subjective phenomenon associated with the instability of boundaries between behavioral states and the constant intrusion of sleep episodes into wakefulness. Under baseline conditions, 0X2R, orexin , and orexin/ataxin-3 transgenic mice have normal amounts of wakefulness and non-REM sleep during the light and dark phases and over 24 h (Chemelli et al, 1999 Hara et al, 2001 Mochizuki et al, 2004 Willie... 

Photosynthetic plant cells at differ ent (light and dark) phases... 

The still hypothetical RNA world must fill the gap. Orgel suspects that, in this still dark phase of chemical and molecular evolution, a class of molecules was present which could have been relatively easily formed under the conditions present on the young Earth, and which was found in rocks from meteorites perhaps amino acids. These need not to have been the 20 proteinogenic amino acids which we know today, and which are in part quite complex, such as phenylalanine, histidine and tryptophane simple examples would have sufficed. 

Electron injection has been observed during the chemical dissolution of an oxide film in HF [Mai, Ozl, Bi5]. The injected electrons are easily detected if the anodized electrode is n-type and kept in the dark. Independently of oxide thickness and whether the oxide is thermally grown or formed by anodization, injected electrons are only observed during the dissolution of the last few monolayers adjacent to the silicon interface. The electron injection current transient depends on dissolution rate respectively HF concentration, however, the exchanged charge per area is always in the order of 0.6 mC cm-2. This is shown in Fig. 4.14 for an n-type silicon electrode illuminated with chopped light. The transient injection current is clearly visible in the dark phases. 

Adverse environmental conditions or stimuli, which create stress in an animal, may influence drug metabolism and disposition. Cold stress, for instance, increases aromatic hydroxylation, as does stress due to excessive noise. It should be noted that the microsomal monooxygenases show a diurnal rhythm in both rats and mice, with the greatest activity at the beginning of the dark phase. 

Temperature measurements should be performed at the same time due to circadian rhythm. Baseline body temperature is significantly higher during the night. If testing occurs during the dark phase, there may be an interference with the amplitude of hyperthermia when the stressor is presented (21). 

Figure 19.20 Piezoelectric vibration maps of phase ((a), (c)) and amplitude ((b), (d)) (3x3 /um2) of a fatigued Pt-PZT-Pt structure after positive ((a), (b)) and negative ((c), (d)) poling. Bright and dark phase areas correspond to bottom-to-top and top-to-bottom polarization orientations, respectively.

Figure 8.2 Confocal micrograph of a sample from the rag layer shown in Figure 9.1. The oil is the bright phase it exhibits structures typical of gels (black arrows) which are often found in oxidized crude oil. This rag layer contained between 20 to 30% oil, which represents a significant potential loss of recovery. The water is the dark phase it exhibits aggregates of clay particles and emulsified oil (white arrow). Bar = 50 Xm. From Mikula and Munoz [68]. Copyright 2000, Cambridge University Press.

Superimpose the bright annulus exactly on the dark phase ring by centering the annulus holder. 

Answer This observation suggests that photosynthesis occurs in two phases (1) a light-dependent phase that generates ATP and NADPH, which are essential for C02 fixation, and (2) a light-independent (dark) phase, in which these energy-rich components are used for synthesis of glucose. In the absence of additional illumination, the supplies of NADPH and ATP become exhausted and C02 fixation ceases. 

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