Role of the Iodide-Methylammonium Interaction in the Ferroelectricity of CH3 NH3 PbI3.

Excellent conversion efficiencies of over 20 % and facile cell production have placed hybrid perovskites at the forefront of novel solar cell materials, with CH3 NH3 PbI3 being an archetypal compound. The question why CH3 NH3 PbI3 has such extraordinary characteristics, particularly a very efficient power conversion from absorbed light to electrical power, is hotly debated, with ferroelectricity being a promising candidate. This does, however, require the crystal structure to be non-centrosymmetric and we herein present crystallographic evidence as to how the symmetry breaking occurs on a crystallographic and, therefore, long-range level. Although the molecular cation CH3 NH3 + is intrinsically polar, it is heavily disordered and this cannot be the sole reason for the ferroelectricity. We show that it, nonetheless, plays an important role, as it distorts the neighboring iodide positions from their centrosymmetric positions.

Glancing-angle ion enhanced surface diffusion on gaAs(001) during molecular beam epitaxy.

We describe the effects of glancing incidence 3-4 keV Ar ion bombardment on homoepitaxial growth on vicinal GaAs(001). The average adatom lifetime on surface terraces, measured during growth using specular ion scattering, decreased monotonically with increasing ion current density. The results indicated that surface diffusivity was increased by the ions. The ion beam also suppressed growth oscillations and decreased the film surface roughness. This indicates a change from two-dimensional island nucleation to step-flow growth due to increased adatom surface diffusivity. A simple model, involving direct momentum transfer from ions to adatoms, is shown to be consistent with the measured enhanced diffusion.

Analysis of milk-based infant formula. Phase IV. Iodide, linoleic acid, and vitamins D and K: U.S. Food and Drug Administration-Infant Formula Council: collaborative study.

In 1982, the U.S. Food and Drug Administration, the Infant Formula Council and its member companies, contract laboratories, and other government laboratories began a study of analytical methods for the nutrients listed in the Infant Formula Act of 1980. Phases I, II, III, and V have been completed. The present report provides data on Phase IV, in which 13 laboratories collaboratively studied an ion-selective electrode method for analyzing iodide, a gas chromatographic method for linoleic acid, and 2 liquid chromatographic (LC) methods each for vitamins D and K. Data were insufficient to evaluate one each of the LC methods studied for vitamins K and D. The relative standard deviations (RSD) are sufficient for the nutrient levels found in infant formula. RSDs (%) for repeatability (RSDr) and reproducibility (RSDR), respectively, were as follows: iodide, 4.0-11.4 and 13.5-18.2; linoleic acid, 1.0-1.6 and 3.5-5.1; vitamin K1, 3.2-16.0 and 6.2-19.4; and vitamin D3, 4.2 and 35.0. The recommendation to adopt the method for vitamin D was supported by the results of a ministudy. All laboratories were capable of using these methods with little training. The methods for determination of iodide, linoleic acid, and vitamins D and K in ready-to-feed milk-based infant formula have been adopted first action by AOAC International.

Analysis of milk-based infant formula. Phase V. Vitamins A and E, folic acid, and pantothenic acid: Food and Drug Administration-Infant Formula Council: collaborative study.

In 1982, the U.S. Food and Drug Administration, the Infant Formula Council and its member companies, contract laboratories, and other government laboratories began a study of analytical methods for the nutrients listed in the Infant Formula Act of 1980 (P.L. 96-359). Four phases of the study have been completed and are discussed in earlier reports. The present report provides data on Phase V, in which 13 laboratories collaboratively studied individual methods for folic acid, pantothenic acid, and vitamin E, in addition to 2 methods for vitamin A. Vitamins A and E are determined by liquid chromatography. Folic acid and pantothenic acid are determined by microbiological methods using acidimetric and/or turbidimetric assays as the determinative step. In most cases, relative standard deviations for repeatability, RSDr, and reproducibility, RSDR, are as good as those that would be predicted from other collaborative studies. RSDr and RSDR values obtained for the 5 methods are 9.35 and 25.44% for folic acid, 4.59 and 10.23% for pantothenic acid, 8.46 and 11.69% for vitamin E, 3.62 and 9.72% for vitamin A (retinol isomers), and 4.9 and 10.5% for vitamin A (retinol). The 5 methods have been adopted first action by AOAC International.

Wild mice in the cold: some findings on adaptation.

The house mouse, Mus domesticus, can thrive in natural environments much below its optimum temperature. Thermogenesis is then above that at more usual temperatures. In addition, body weight, and the weights of brown adipose tissue and the kidneys, may be higher than usual. In free populations of house mice cold lowers fertility and may prevent breeding. Other possible limiting factors on breeding are food supply, shelter for nesting and social interactions. In captivity, wild-type house mice exposed to severe cold (around 0 degrees C) at first adapt ontogenetically by shivering and reduced activity. But raised thermogenesis is soon achieved without shivering; nest-building improves; and readiness to explore may be enhanced. Endocrine changes probably include, at least initially, a rise in adrenal cortical activity and in catecholamine secretion. Some females become barren, but many remain fertile. The maturity of fertile females is, however, delayed and intervals between births are lengthened; nestling mortality rises. A limiting factor during lactation may be the capacity of the gut. Similar adaptive changes are observed during winter in some species of small mammals that do not hibernate. But neither the house mouse nor other species present a single, universal pattern of cold-adaptation. Wild-type mice bred for about 10 generations in a warm laboratory environment (20-23 degrees C) change little over generations. In cold they become progressively heavier and fatter at all ages; they mature earlier, and nestling mortality declines. The milk of such 'Eskimo' females is more concentrated than that of controls. If 'Eskimo' mice are returned to a warm environment, they are more fertile, and rear heavier young, than controls that remained in the warm. Despite the heavier young, litter size is not reduced: it may be increased, probably as a result of a higher ovulation rate. Parental effects have been analyzed by cross-fostering and hybridizing. Survival, growth and fertility are all favourably influenced by the intra-uterine and nest environments provided by 'Eskimo' females. 'Eskimo' males are also better fathers. Hence after ten generations the phenotype of cold-adapted house mice shows the combined effects of (a) an ontogenetic response to cold, (b) a superior parental environment and (c) a change genotype. The secular changes in the cold that lead to this phenotype give the appearance of evolution in miniature; but it is equally possible that they represent a genetical versatility that allows rapid, reversible shifts in response to environmental demands.(ABSTRACT TRUNCATED AT 400 WORDS)

Methods of analysis for infant formula: Food and Drug Administration and Infant Formula Council Collaborative Study, Phase III.

Phase III of the collaborative study of methods of assay for nutrients in infant formulas was conducted. The study included assay of chloride, phosphorus, proximates (ash, fat, protein, total solids, and carbohydrates), thiamine, total pantothenates, and vitamins A, B12, and E. Most of the methods were those in Official Methods of Analysis, 13th edition, with slight modifications, or methods of the Infant Formula Council. On the basis of the results obtained by the collaborators, the methods for chloride, phosphorus, proximates, thiamine, and vitamin B12 have been adopted official first action. Methods for total pantothenates, vitamin A, and vitamin E were not recommended for adoption at this time because of anticipated improvements in methodology in the foreseeable future.

Methods of analysis for infant formula: Food and Drug Administration and Infant Formula Council Collaborative Study.

Because the U.S. Infant Formula Act of 1980 requires manufacturers to produce formula containing a specific minimum amount of nutrients, it became necessary to establish analytical methods for the nutrients listed in the Act. The Food and Drug Administration, the Infant Formula Council, its member companies, contract laboratories, and other government laboratories undertook a collaborative study of available methods; the specific nutrients studied to date include vitamins A, B6, C, riboflavin, and niacin, and the elements calcium, magnesium, iron, zinc, copper, manganese, sodium, and potassium. The coefficients of variation in most cases have been as good as those that could be predicted from other collaborative studies. The methods studied for these nutrients have been adopted official first action except the method for vitamin A.

Milk production and consumption and growth of young of wild mice after ten generations in a cold environment.

Three classes of wild house mice, Mus musculus, were studied: (a) mice of the tenth generation in captivity in an environment kept at 23 degrees C (controls); (b) a similar stock kept at 3 degrees C (Eskimo); (c) offspring of controls transferred at mating to 3 degrees C (immigrants). For analysis of chemical composition, samples of milk were drawn from lactating females after they had been injected with oxytocin. For estimates of milk yield, lactating females were injected with tritiated water, and yield was calculated from the tritium content of young aged 10 days, over a 24 h period. The milk of Eskimo females had a much higher proportion of both fat and protein than had milk of other classes. The milk of immigrant females had more fat but less protein than that of controls. Eskimo females were heavier than immigrant females; control females were the lightest. Eskimo young at 10 days were heavier than those of the other classes. Their body fat was much higher; but their fat-free body weight was also above that of the others. Young of both classes in the cold drank more milk than the controls, and the Eskimo more than the immigrant young. Maternal body weight, milk intake by the young and body weight of the young were intercorrelated, but milk intake was the principal determinant of the body weight of the young. There was no evidence of differences in the growth potential of the young of different classes.(ABSTRACT TRUNCATED AT 250 WORDS)

Decrement in "social stress" among wild rattus rattus treated with antibiotic.

"Black" rats, Rattus rattus, were trapped and studied in colonies of 6 adult males and 6 adult females. Eight colonies had antibiotic (Neoterramycin) in their drinking water, and eight (controls) had not. Twenty mated pairs were kept in small cages; of these, ten received Neoterramycin. The only deaths of males were in the control colonies. In the antibiotic colonies there were also (1) a lower incidence of attack when behavior was directly observed, (2) less skin wounding, (3) less macroscopic evidence of lung lesions. The lowest incidence of skin scars and lung lesions was among the rats kept in small cages. There was no evidence of an effect of the antibiotic on body or adrenal weights, or on kidney pathology. The locomotor activity of rats was separately recorded, with or without antibiotic, in artificial automated environments There was no evidence that activity was reduced by antibiotic. It is hypothesized that diseased rats provoke more attack than healthy ones.

Sequences of feeding, sampling and exploration by wild and laboratory rats.

Adult male wild rats and male laboratory rats, all Rattus norvegicus, were kept alone for 11 d is a residential maze. The maze had a central nest box and four arms radiating from it. Movement in the arms was automatically recorded. Three foods were supplied, one at the end of each of three arms; the fourth arm was empty. One food was usually much preferred to the othe two. Except on Days 1-3, access to the arms was for only 3h daily. The rate of visiting the arms declined during the first 3 d. The wild rats were more 'active' than the domestic in that they made more visits; but they spent less time in the arms. Visits were of two kinds: (a) short, usually < 1min; (b) long (> 4 min.: meals). The wild rats had shorter meals than the donestic. A 3-h period of access usually began with a bout of short visits to the arms. Each long visit to a food arm (a meal) was also typically followed by such a bout, sometimes after a period in the nest box (drinking). the first short visit after a meal by a wild rat was most often to the empty arm; but domestic rats distributed these visits evenly among the three arms in which they had not been feeding. In a given bout the second short visit by a wild rat, but not a domestic, tended to repeat the first. We interpret a bout of short visits as a patrol or re-exploration of the living space which may include sampling of all accessible foods. When a bout occured at the beginning of access to the maze arms, exploring was in 'competition' with eating; a bout after a meal may have represented 'disinhibition' of exploring.

Ethology and man: science or myth?

What is known of human evolution gives us little help in describing the biological nature of man: even our fossil history is obscure, and most statements on the evolution of human behaviour are guesses. The fact that primitive man was a predator on other species does not signify that man is "naturally aggressive" to his own kind. The notion of an inherent drive to aggression has no scientific foundation. Knowledge of the conduct of other species can lead to no valid conclusions about human behaviour. The same limitations apply to interpretations of modern man based on what is known of human hunter-gatherers. Ethology can contribute to human studies (1) by providing methods of observing and analysing behaviour, and (2) by providing hypotheses that can be tested. Zoologically-based hypotheses on the ill effects of crowding have been useful but have proved to be wrong. Others on the effects of stimulation in early life, and on breast-feeding and milk composition, have been more fruitful. Abnormal conduct, such as that of Kanner's syndrome, can be usefully studied by ethological methods. Man is a learner and a teacher, whose knowledge of himself increases slowly with the growth of critical research.