Search

A first step in the accurate quantitative spectroscopic analysis of central stars of PN has been based on fitting the results of NLTE, hydrostatic, plane-parallel model atmosphere calculations to the observed H and He absorption-line profiles in high-resolution spectra of bright central stars (Méndez et al. 1988, A&A 190, 113 and subsequent papers). Such analyses have provided very useful determinations of the basic atmospheric parameters: Teff, log g and He abundance.

The central stars of the planetary nebulae He 2–131 and He 2–138 show variations in their visual magnitudes, with amplitudes of about 0.1 mag. and time scales of a few hours. This behavior appears to be very similar to that exhibited by the central stars of IC 418 and IC 4593. These four central stars have several other characteristics in common: a relatively low effective temperature, between 27000 and 40000 K; clear spectroscopic evidences of mass loss, both in the ultraviolet (IUE) and visible spectral regions; and short-term spectroscopic variability, in the form of radial velocity variations and/or of substantial changes in emission and P-Cygni-type line profiles. None of these central stars has shown convincing evidence of binarity; we attribute their behavior to variations in the stellar winds.

During the past decade the achievements in the theory of stellar atmospheres of hot stars combined with improved spectrograph and detector technology at large telescopes have led to a significantly improved knowledge of PN nuclei properties (see Méndez et al. 1988, Kudritzki and Méndez 1989).

Spectrograms, scanner, uvby and ANS ultraviolet measurements of the central stars of NGC 2346, He 2-36 and NGC 3132 are analysed. The observations suggest that the first one is a foreground horizontal-branch star, and the second is above the horizontal branch, presumably in a rapid evolutionary phase. Both objects are probably variable. The central star of NGC 3132 is a slightly evolved main-sequence star with a hot visual companion. The evolutionary status of this system is briefly discussed.

The present paper is a progress report on a search for spectroscopic binaries among central stars of planetary nebulae. In the last few years it has become clear that such a program may result in a significant improvement of the available information about the central stars, and, whatever the outcome, it will certainly help to test current theoretical work on the origin of planetary nebulae.

We have started a study of WC central stars of planetary nebulae, including “O VI” objects which show WC characteristics. One of our purposes was to check, all along the WC spectral sequence, if the emission lines of planetary nuclei are narrower than for Population I objects, as they are in the case of the WC9 central star BD+30°3639 (Smith and Aller 1971).

Median daily iron absorption was determined in iron-replete males and females between 2 and 19 years of age from the upper and lower socioeconomic strata of the Venezuelan population. A comparison was made with iron absorption of well-nourished children, on the basis of hematological and anthropometric reference values from the U.S. The median absorption level, which was calculated from the increase in total body iron due to growth and the daily losses through exfoliation and menstruation, was also used to estimate the requirements of 95% of the population. When the requirements were expressed in terms of body weight, no significant difference in iron absorption was observed between the three Venezuelan and one U.S. groups, ranging from about 30 to 38 µg/kg/day in both sexes between 4 and 16 years of age. However, when the requirements were expressed without division by the weight factor, the requirements of the better nourished groups were somewhat higher than those of the Venezuelan lower socioeconomic population with, in addition, a threefold variation over the 5 to 16 year age range. These findings suggest that the total iron requirements of children at a certain age may be most adequately expressed in terms of the optimal body weight for that age. J Am Diet Assoc 88:454, 1988.

1. Introduction. 2. A list of binary and multiple CSPN. 3. A radial velocity study of CSPN at high spectral resolution. 4. Spectroscopic binaries or intrinsic variables? 5. Concluding remarks.

The present observations are part of a search for spectral and radial velocity variations among central stars of planetary nebulae (Méndez 1980). The spectrograms were taken with the image-tube spectrographs of the 1-m and 4-m telescopes at the Cerro Tololo Inter-American Observatory (CTIO). The emulsion was always IIIa-J baked in “forming gas” (N2+H2). The “blue” spectrograms extend from 3600 to 5000 Å at 45 Å mm-1; the “red” ones extend from 5000 to 7000 Å, at 45 Å mm-1 (4-m plates) and 90 Å mm-1 (1-m plates). All plates were calibrated with a spot sensitometer. Seven “blue” and seven “red” spectrograms, all obtained with the 4-m telescope, were traced with the PDS microphotometer of the David Dunlap Observatory. The intensities from each plate were stored in computer memory and were later added together, in order to improve the signal-to-noise ratio. The resulting intensity tracings reveal more details than had previously been observed (Swings and Struve 1941, Aller and Wilson 1954, Andrillat 1957, Aller and Kaler 1964).

CRUDE FAT OR ETHYL ETHER EXTRACT DETERMINATION IN COCONUT MILK

Hematologic studies carried out in inhabitants of the State of Carabobo revealed that 19% of the subjects studied presented iron deficiency, this being more prominent in women and in children. Iron deficiency anemia was absent in men, while in the other groups its frequency, as registered, was from 5 to 13%. Tests for iron absorption from foods which form the average diet of the population in the Carabobo State, and the diet consumed by adults from the low socioeconomic strata in the States of Carabobo and Yaracuy, demonstrated that in normal subjects, bioavailability is lower than physiological requirements of men, women and children. In the iron-deficient subjects, its bioavailability can cover physiological needs. It is estimated that an important proportion of the population strata consuming such diets, suffer from iron nutritional deficiency, especially women during the reproductive age, and children.

We present spectroscopic distances for 22 central stars of planetary nebulae. These distances have been determined using information provided by our non-LTE model atmosphere analyses of the stellar H and He absorption line profiles. In this way, no assumptions about nebular properties are necessary.

HD 50896 (=EZ CMa) has long been known as a variable star.Pecently,Firmani et a1.(1980) derived a period of 3.763 days from spectral and photometric variations.This period was later confirmed by McLean(1980) and by Cherepashchuk(1981).

A 51-year-old man with epilepsy received carbamazepine during three weeks. He developed fever, jaundice, dark urine and pale stools. Laboratory data showed hepatocellular injury and cholestasis; six weeks after withdrawal of the drug these abnormalities returned to normal limits. The liver biopsy showed acute cholangitis, bile duct injury, granulomas and eosinophils in the portal areas.

In this review we will discuss the hottest subluminous H-deficient stars, namely those with Teff > 30000 K. In the absence of reliable distance determinations for hot subluminous stars, the best way to discuss their properties and evolutionary status is to find their positions on the log g — log Teff diagram. In the last few years, after extensive computational work, first in Kiel and more recently also in Munich, it has become possible to obtain log g and Teff, together with the surface He abundance, directly by fitting the observed H and He absorption line profiles with theoretical profiles obtained from non-LTE model atmospheres and associated line formation codes. The non-LTE models are plane-parallel, in hydrostatic and radiative equilibrium, and the atmosphere is assumed to consist of H and He only. A recent paper by Groth et al. (1985) gives most of the references on the application of this non-LTE model atmosphere approach to the study of all kinds of hot subluminous stars.

It is a good tradition in IAU Symposia about PN to have a paper on model atmospheres. However, this is always a difficult task for the authors, because the majority of the PN researchers still believe that the best model atmosphere for a Central Star is a black body. Of course, this puts a theorist in stellar atmospheres into a somewhat desperate position. However, Central Stars of Planetary Nebulae (hereafter CSPN) — as all other stars — show spectral lines. And we will try to use the opportunity of this paper to convince that — as for all other stars — the quantitative analysis of these lines on basis of model atmospheres yields extremely valuable information about the physical nature of the stars.

Proteins, some minerals and vitamins, play important roles in erythropoiesis and the survival of the red blood cell. This article deals specifically with the physiological requirements and recommended intakes of iron, folate and vitamin B12. A comparison of the physiologic iron requirements according to age and sex, and the amount of iron which is actually absorbed from the diets consumed by the lower socioeconomic strata of the Venezuelan population; indicates that these diets do not satisfy the requirements at all ages. Such disparity is most marked in children below three years of age, in adolescents and in women during their reproductive age. Failure to do so leads to varying degrees of iron deficiency. This low bioavailability of the Venezuelan diet is also observed in other Latin American diets consumed by the same low socioeconomic strata, which explains the high prevalence of iron-deficiency anemia in the vulnerable groups. The low intake of fruits and vegetables by the lower socioeconomic strata of the Latin American population prevents these sectors from consuming an adequate intake of folate, failing to fulfill the daily recommended intake (3.3 - 3.6 micrograms/kg body weight). This situation is aggravated in pregnant and lactating women who require an additional intake of 300 micrograms and 100 micrograms, respectively. Prevalence of folate deficiency in the first stage may be in the order of 30% in some regions. In the second stage of deficiency, characterized by megaloblastic changes in the bone marrow and an erythrocyte folate concentration of less than 50 micrograms/lt, it could be as high as 40% in pregnant women. Nutritional vitamin B12 deficiency does not constitute a health problem in Latin America. Various surveys in the lower socioeconomic strata have reported normal or higher than normal serum B12 concentrations, compared to well-nourished populations.

We have started a study of WC central stars of planetary nebulae, including “0 VI” objects which show WC characteristics. One of our purposes was to check, all along the WC spectral sequence, if the emission lines of planetary nuclei are narrower than for Population I objects, as they are in the case of the WC9 central star BD+30°3639 (Smith and Aller 1971).

This is a retrospective study based on growth and development data published in Venezuela by various authors in the period 1936-1978. The data on height for males of the middle and high socioeconomic strata show growth curves which are very similar to the standards for British children. Likewise, the girls of the same socioeconomic condition follow the British standards, but only up to about 10-12 years of age. After that age, the girls studied by the Venezuelan authors, show a pattern of early maturation with a corresponding lower adult height compared with their British counterparts. There were differences in the growth curves according to the socioeconomic strata. These differences were more marked in the girls data. A secular increase for height was discerned, from the published data, in all socioeconomic strata and in both sexes. The data on sexual maturation showed a tendency for progressively early menarche in Venezuelan girls. These changes in growth in height and age of menarche were more notorious and came about at an earlier age in the upper socioeconomic strata. They were less marked, not constant, and came about later in the lower socioeconomic groups. The secular changes in height and sexual maturation apparent from these data, could be explained by an improvement in the environmental conditions, especially nutrition and hygiene of the population, and also be genetic heterosis from European immigration and with improvement in communications.A review of trends in height and weight at menarche in Venezuela is presented using data from studies published during the period 1936 to 1978. Variations by socioeconomic status are identified and discussed. (summary in ENG)

El análisis de crecimiento de 5 híbridos de zanahoria (Daucus carota L.) se efectuó en Cipreses de Oreamuno, Cartago, con el objetivo de describir el crecimiento y la fenología del cultivo de zanahoria. El análisis de crecimiento se realizó mediante la metodología de análisis funcional. Se evaluó el área foliar y peso seco total de cada órgano de la planta, se ajustaron modelos de regresión no lineal para dichas variables, se obtuvieron los parámetros que definen las funciones matemáticas que describen el crecimiento y se representó gráficamente cada modelo para cada variable evaluada. Las variables de peso seco total y de raíz se ajustaron en la función ogística no-lineal asintótica: PS=alfa/(1+exp(-beta(x-gamma))); el peso seco de hojas y el área foliar se ajustaron en la función tipo “campana”: PS=alfa*exp(-beta(x-gamma)2). Las plantas presentaron una curva de crecimiento sigmoidal con fases bien definidas: una fase de crecimiento lento, luego una etapa de crecimiento exponen cial, seguida de una etapa de disminución del crecimiento y por último una etapa de estabilidad. La planta dedica sus primeros estados de desarrollo a establecer su maquinaria fotosintética, en competencia directa con el desarrollo radical. La raíz comienza a engrosar entre los 63 dds y los 77 dds según el híbrido, durante la etapa II de crecimiento, con una mayor proporción de asimilados destinados a la raíz, lo que conduce a un aumento en su diámetro. Finalmente, del análisis de las variables de peso seco total y área foliar, se puede establecer 2 grupos: por un lado Suprema, Esperanza y Bangor, y por otro CLX-3193 y Sirkana. El primer grupo presentó los valores más altos para dichas variables.

The adsorption of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and N,-dimethyl-3,4,9,10-perylenetetracarboxylic diimide (DiMe-PTCDI) on differently treated n-doped GaAs(100) surfaces was investigated using high-resolution photoemission spectroscopy. The chemical interaction between the molecules and the semiconductor substrate is found to be weak; core level photoemission spectra show no additional chemically shifted peaks, indicating the absence of any covalent/ionic bond formation. Only a sharpening of the core level spectra is observed for a coverage lower than one monolayer and this is attributed to a reduction of inhomogeneous band bending at the surface. This is interpreted in terms of preferential sticking of the organic molecules to surface defects. The energy offset between the occupied states in the substrate and the organic film is directly derived from ultraviolet photoemission spectroscopy measurements. Interface dipoles are found to form according to the electron affinities of the substrates and PTCDA films at the interfaces and, consequently, the vacuum level alignment rule does not hold. For vanishing interface dipole the lowest unoccupied molecular orbital of PTCDA is found to align with the conduction band minimum of GaAs resulting in electron affinity of 4.12 eV for PTCDA. This provides an energy gap in the range of 2.44–2.55 eV, which is larger than the onset of optical absorption. The same procedure is applied to DiMe-PTCDI layers.

The objective of this study was to assess the reproductive competence of oocytes obtained by follicular flushing in poor responder patients. This prospective comparative study, at the University of Paris XI, Assistance Publique des Hopitaux de Paris, INSERM Unit 782, was performed on 165 infertile IVF embryo transfer candidates. A total of 271 consecutive minimal stimulation IVF cycles were studied. Oocyte retrieval was performed 34 h after human chorionic gonadotrophin administration and oocytes were allocated into two groups according to their retrieval method: oocytes obtained in the first follicular aspiration (FA, n = 127); and oocytes retrieved in the subsequent follicular flushing (FF, n = 102). The principal outcome was to evaluate clinical pregnancy and embryo implantation rates. Thus, patient characteristics, fertilization rate and clinical pregnancy rate per oocyte were comparable in both of groups. In contrast, embryo morphology (41 versus 59%, P < 0.01) and implantation rates (20.4 versus 34.8%, P < 0.04) were better in the FF group. In conclusion, an optimal reproductive competence was observed in oocytes retrieved by follicular flushing in minimal stimulation IVF in poor responder patients.

This paper presents deep spectra of 14 planetary nebulae (PNs) at a variety of angular distances from the center of the flattened elliptical galaxy NGC 4697. Both near the center and among the most outlying PNs we have found several examples of very strong [O III] 5007, about 20 times brighter than Hbeta. This, together with strong [Ne III] lines, implies a lower limit for O and Ne abundances near solar at the center and also at more than two effective radii from the center of NGC 4697. Thus we have found, for the first time from individual stars, direct evidence of the existence of a metal-rich population in elliptical galaxies, confirming metallicities derived from absorption-line indices and extending the information to angular distances where the stellar surface brightness is too low for absorption-line studies. A comparison with abundances obtained closer to the center of NGC 4697 from integrated absorption-line spectra indicates that the metallicity gradient, which is quite steep within one effective radius, becomes much less pronounced beyond one effective radius. The only alternative to this interpretation would be the presence of a very metal-poor PN population with [Z/H] below -1, which we cannot rule out but would require an extremely bimodal metallicity distribution with almost no intermediate metallicities., Comment: 43 pages, 14 figures, accepted for publication in ApJ

Nanoestructures; quantum dots; molecular beam epitaxy; semiconducting III-V materials.

We present spectroscopic distances for 22 central stars of planetary nebulae. These distances have been determined using information provided by our non-LTE model atmosphere analyses of the stellar H and He absorption line profiles. In this way, no assumptions about nebular properties are necessary.Our spectroscopic distances turn out to be larger than many other frequently cited values. We show that our distances are not in contradiction with the available information about the interstellar extinction, and we describe additional evidence supporting them.

Spectra of eight planetary nebulae are described in the region A3400-A7200. Key words: planetary nebulae - nebular spectra