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Experimental observations of the gerade (g) states of O2 that exist between the dissociation limit of the B 3 Σ u − state and the X 2 Π g ground state of O2+ are reexamined. Emphasis is placed on the assignment of electronic structures of the [X 2 Π g ]ndλ 1,3 Λ g Rydberg states for which experimental data can be obtained from the literature: mainly, ndπg- and ndδg-based 1,3 Λ g states with n=3–5 and the ndπ g 1 Σ g + and 3 Σ g − series with n=6–11. In many cases, characterizations of these electronic structures are limited by the quality of existing experimental data and, in cases where rotational band structures were analyzed, by the unavailability of most of the rotational energy level data upon which reported parameterizations were based. Thus, while a general picture of some segments of the ndπg- and ndδg-based structures can be presented, quantitative descriptions of these structures and unique identification of the causes of many apparent structural irregularities will not be possible until a new well-calibrated, rotationally resolved database is developed.

Well-calibrated, resonance-enhanced multiphoton-ionization (REMPI) spectra of eight bands of d 1 Π g ←a 1 Δ g and four bands of d 1 Π g ←b 1 Σ g + in O2 have been recorded and analyzed. These data provide detailed characterizations of the complex rotational structures in the five lowest vibrational levels (v=0–4) of the d 1 Π g state. The observed complexities in the rovibronic structure of d 1 Π g are the result of strong perturbations between the d 1 Π g Rydberg and the II 1 Π g valence states. Weaker perturbations resulting from interactions between d and the II 1 Δ g valence state also are observed.

Existing experimental (2+1) REMPI spectra for transitions into rotationally resolved levels of the 3sσg d 1Πg and 3sσg C 3Πg Rydberg states of O2 have been rotationally analyzed, resulting in the first characterization of rotational perturbations in d(v=1–3) and C(v=2). In addition, the results of this analysis have been interpreted with the aid of a coupled-channel Schrodinger-equation (CSE) model of the interacting electronic states. The identification and characterization of perturbations in the d and C states have allowed the nature of the interactions between the 3sσg 1,3Πg Rydberg states and the II 1Πg valence state to be clarified and a realistic empirical potential-energy curve for the II 1Πg state to be determined. While it is found that first- and second-order interactions with the II 1Πg valence state are responsible for the strongest perturbations observed in d(v=1–3) and C(v=2), additional weak perturbations found in d(v=2 and 3) are shown to result from a second-order interaction with the II...

The results of a critical reexamination of previous experimental observations of the (X 2Πg) nsσg 1,3Πg Rydberg states of O2 are employed to optimize a coupled-channel Schrodinger-equation (CSE) model describing rovibronic interactions among a number of 1,3Πg Rydberg and valence states. The results of calculations using this CSE model are compared with the experimental energy-level and predissociation linewidth data base. As a result of the optimization process, relevant potential-energy curves and Rydberg–valence, Rydberg–Rydberg, and valence–valence interactions are characterized for 1,3Πg states in the ∼6.5–9.5 eV region above the ground state of O2. The precision of these characterizations and the interpretation of the experimental observations are found to be limited by the quality of the existing data, which exhibit a number of inconsistencies that cannot be reconciled without new, well-characterized experimental studies. In spite of these difficulties, the present CSE model, as currently parametriz...

Cells of the intestinal mucosa of the infant and adult rat maintain a pattern of continuous growth, accumulating structural and functional proteins and lipids while migrating the length of the villus column. Cells of jejunal and ileal segments were fractionated sequentially from villus tip to inner crypt and distribution patterns were determined for DNA, total protein, cholesterol, phospholipid, and disaccharidases. Patterns of increasing ratios of protein, lipids, and disaccharidases to DNA were maintained to villus tips, with only slight fall-off of enzymes observed. Distribution profiles of disaccharidases, when computed relative to protein (as seen in previous reports), show distortion of the true cellular distribution pattern of these enzymes as determined by the DNA content of the fractions. Wide variation in cell protein concentrations was evident between jejunal and ileal segments in pre- and postweaned rats. Ileal cells of the suckling rat contained particularly high protein concentrations, which appeared to be largely transitory in nature and related to food intake. Cholesterol and phospholipids were found to be concentrated in the microvillus membrane and account for a significantly large fraction of the cellular content of these lipids.

Adult rats when fed a high carbohydrate diet of 70% sucrose or glucose for 24 h following a 4-day fast showed increased concentrations of intestinal sucrase-isomaltase (EC 3.2.1.48, EC 3.2.1.10) and maltase-glucoamylase (EC 3.2.1.20) but not lactase-phlorizin hydrolase (EC 3.2.1.23, EC 3.2.1.62). The concentration increases of these enzymes were accompanied by corresponding acceleration of their synthesis rates. Contrary to earlier studies by others, suggesting that upper villus cells in the fasted intestine are unresponsive to stimulation of sucrase activity by refeeding a high-sucrose diet, the concentration increases of both sucrase-isomaltase and maltase-glucoamylase were seen to occur in cells all along the length of the villus column. The earlier studies differed from the present study by basing enzyme assays relative to protein rather than the DNA content of villus cell fractions. We have shown that villus cells increase their protein content severalfold while migrating to villus tip, providing the basis for the difference between earlier and the present findings. Further evidence that stimulation of sucrase-isomaltase and maltase-glucoamylase by high carbohydrate is not restricted to the crypt and lower villus region was obtained by the finding that their synthesis rates appeared to be equally stimulated along the length of the villus column.

L'auteur evalue les avantages et les inconvenients de l'utilisation de microformes pour les recherches en histoire. A cote des grands editeurs comme UMI (University Microfilms International) et Harvester Press Microforms Lnd, l'auteur presente les initiatives d'editeurs plus modestes qui se consacrent a des periodes bien precises de l'histoire de l'Angleterre