This study was aimed to investigate associations between birth weight and multiple adiposity indicators in youth, and to examine potential mediating effects by biological maturation. This was a school-based study involving 981 Brazilian adolescents aged between 10 and 17 years. Birth weight was reported retrospectively by mothers. Maturation was estimated by age of peak height velocity. Adiposity indicators included body mass index (BMI), waist circumference and percent body fat estimated from triceps and subscapular skinfolds. Multilevel mediation analyses were performed using the Sobel test, adjusted for chronological age, gestational age, cardiorespiratory fitness and socio-economic status. Except for body fat in girls, biological maturation partly or fully mediated (P<0.05) positive relationships between birth weight with all other obesity indicators in both sexes with their respective values of indirect effects with 95% confidence intervals: BMI [boys: 0.44 (0.06–0.82); girls: 0.38 (0.13–0.64)], waist circumference [boys: 1.14 (0.22–2.05); girls: 0.87 (0.26–1.48)] and body fat [boys: 0.60 (0.13–1.07)]. To conclude, birth weight is associated with elevated obesity risk in adolescence and biological maturation seems to at least partly mediate this relationship.

Tholins are polymeric hydrogenated carbon nitrides formed from N2:CH4 mixtures exposed to electrical discharges. They are complex disordered solids, and their structural chemistry and formation processes are not yet fully understood. Tholins have been widely adopted as useful analogs of reddish organic solids associated with planetary bodies or in interstellar space (e.g., Titan's aerosols, reddish surfaces of outer objects, interstellar organics, etc.) for fitting astronomical observations. However, there has been little evidence to date that they in fact constitute pertinent model materials, i. e. with chemical structure/composition similar to those presumed to be present in planetary or interstellar organic solids. In this contribution, we first review recent advances made regarding the determination of composition and structure of tholins produced in the laboratory. They point to a high chemical selectivity in the range of functional groups present, the control of unsaturation by nitrogen, and the highly disordered character of the structures. In a second section, we discuss the relationship between chemistry and the optical properties of tholins, and we point out the lack of a unique relationship between the shape and strength of the visible absorption bands and the chemical composition or structure of the model tholins. The tholins exhibit similarities with HCN “polymers”, that are suspected to be present in cometary refractory dust. This points to the existence of possible similar polymerisation processes, and it suggests they could also be used as analogs of N-rich cometary organics. Laboratory-based studies of cometary dust might offer new insights on the “chemical relevancy” of tholins, as combined micro-analytical techniques will allow direct comparison of chemical information between the materials produced. In a third section we present recent results pertaining to the search for such compounds in cometary grains (Stardust grains, interplanetary dust particles - IDPs). We show that some N-rich spots in stratospheric IDPs are rich in cyanide species, but no tholin-like compounds or polymeric HCN have been detected to date.

As a prerequisite to returning their molecular inventory to the gas phase, icy grain mantles must desorb from the refractory core material of the grain. This desorption process can be instigated through interactions with photons or cosmic rays but can equally well be thermally driven. In this invited paper, the application of thermal desorption techniques borrowed from ultrahigh vacuum surface science to problems of astronomical interest will be discussed. The experimental methods employed by surface scientists to probe thermal desorption processes will be described and the analysis of the resulting empirical data outlined. The results of recent laboratory measurements from a number of groups will be highlighted.

Laboratory surface science under ultra-high vacuum (UHV) conditions allows us to simulate the growth of ices in astrophysical environments. Using the techniques of temperature programmed desorption (TPD), reflection-absorption infrared spectroscopy (RAIRS) and micro-balance methods, we have studied binary ice systems consisting of water (H2O) and variety of other species including carbon monoxide (CO), at astrophysically relevant conditions of temperature and pressure. We present results that demonstrate that the morphology of water ice has an important influence on the behavior of such systems, by allowing processes such as diffusion and trapping that can not be understood through a knowledge of the binding energies of the species alone. Through an understanding of the implications of water ice morphology on the behavior of ice mixtures in the interstellar environment, additional constraints can be placed on the thermodynamic conditions and ice compositions during comet formation.

We analysed a strain collection representative of the overall Neisseria meningitidis population circulating in an open community (46000 inhabitants, Spain) during an endemic period (30 isolates from patients and 191 from throat cultures of healthy individuals) by both phenotypic and molecular techniques. Almost all patient isolates were assigned to three hyper-virulent lineages (ET-5 complex, ET-37 complex and cluster A4) by both multilocus enzyme electrophoresis (MEE) and pulsed-field gel electrophoresis (PFGE). In contrast, MEE and PFGE assigned 20% and 15% respectively of carrier isolates to the hyper-virulent clones (4% for both methods together). There was also a higher correlation between PFGE and phenotypes associated with virulent clones. These notable differences between the two molecular methods were further observed in more than half the carrier isolates, suggesting that the associations between these strains were distorted by recombination events. However, almost one-third of total endemic strains from symptom-free carriers and almost all patient strains belonged to clones defined by MEE and PFGE, with no known epidemiological connection. These data indicate low transmission and a weak clonal structure for N. meningitidis.

Effect of organic acids on 241 americium and 237 neptunium desorption from an acidic cultivated soil. Naturally occurring organic substances have been recognised as one important factor affecting the behaviour in the environment of transuranic actinides. This experimental study aims at evaluating if some naturally occurring carboxylic acids (vanillic, citric, lactic, oxalic) would affect 241Am or 237Np availability in an acidic agricultural soil. Data show that these acids enhance the desorption of americium and neptunium from the soil, with a noticeable effect of citric acid. The fraction desorbed is multiplied by more than 10 for 0.1 M citric acid, and by 3 or 4 with other acids, in relation with the complexation of radionuclides with these acids. The desorption increases with molar concentration of the acids because of the decrease of pH in acidified soils, except for oxalic acid. The soil moisture conditions seem to affect the desorption results: the percentage desorbed is approximately 10 times lower for batch experiments (saturated conditions) than for centrifugation corresponding to unsaturated soil conditions. These preliminary data are mainly qualitative, but they show that it could be interesting to take into account more realistic physico-chemical conditions when measuring desorption ratios for cultivated soils.

Le plutonium a été mesuré, en 1991, sur 5 échantillons de sols et 12 échantillons de sédiments du Rhône prélevés autour du site de la centrale électronucléaire de Creys-Malville. Les concentrations des sols (fraction tamisée à 2 mm) varient, pour 239+240Pu, de 35 ± 4 à 1411 ± 135 mBq.kg-1 sec et, pour 238Pu, de moins de 1 à 101 ± 6 mBq.kg-1 sec. Dans les sédiments, on observe de l7 ± 4 à 147 ± 12 mBq.kg-1 sec en 239+240Pu et de moins de 1 à 7,2 ± 1,6 mBq.kg-1 sec en 238Pu. Ces résultats sont du même ordre que les résultats de mesures de plutonium faites, à ce jour, dans l'environnement français et les rapports isotopiques 238Pu/239+240Pu sont analogues à ceux des retombées atmosphériques (0,03 à 0,08) et sont différents des rapports caractéristiques de l'usine (0,7 à 0,8). La variabilité des résultats selon les échantillons confirme que la fixation du plutonium sur les sols et les sédiments dépend, pour une large part, des teneurs de ces substrats en matière organique et en particules fines.

Materials processing in a microgravity environment is aimed at developing commercial materials as well as investigating basic phenomena to improve earth-based processing. Materials research in space has dealt with glasses and ceramics, crystal growth, electronic materials, metals and alloys, polymers, composites, and biological materials. Battelle has been conducting research in this area since the early-1970s. Several important results have been obtained in: immiscible alloys, containerless under-cooling of clustering alloys, sol-gel glasses, and collagen fibers.

More recently, Battelle's Advanced Materials Center for the Commercial Development of Space (CCDS) has been established to utilize the microgravity environment in the commercial development of composite and mixed-phase materials with substantially improved properties. Currently, the Center is conducting research in catalysts (variant-phase chlorides, zeolites, and mixed oxides), polymer systems, electronic materials (float-zone crystal growth on Type II-VI semiconductor crystals, particularly CdTe), and con-trolled- porosity glass. The present program focuses on a proof of principle for each research thrust, utilizing ground-based and suborbital facilities, together with modeling to demonstrate the potential for producing commercially important materials.

Each of these research programs is outlined. In addition, the more important developments in each of the major categories of microgravity materials research is reviewed.

Two types of limit theorems are proved for processes of randomly displaced regular events. Firstly, as the displacements tend to infinity, the counting process is shown to converge weakly to a Poisson process and secondly, as the interval between events tends to zero, convergence of the finite-dimensional distributions of the associated storage process to a diffusion is proved.

In this paper a dam with autoregressive inputs and unit outputs is considered. Approximations for the distributions of the times to first emptiness and overflow are obtained using a Wald-type identity. The limiting behaviour of the dam content is also investigated

The results obtained by Lehoczky on the first emptiness of a dam subject to random outputs are extended to a more general model.

The first year's campaign of rescue excavations by York Archaeological Trust is described. A sewer and part of a substantial building, perhaps the baths, were located within the Roman legionary fortress, and the sequence of defensive ditches on the south-west front was examined. Extra-mural settlement near the fortress was also examined in two places. Four small trenches in the heart of Anglo-Scandinavian York revealed 10 m of deposits including a post-Roman sequence giving a stratified series of timber buildings with C14 dates, ceramics, and artefacts. Well-preserved biological materials revealed in detail the palaeoecology of the buildings and immediate area. The development of riverside properties in Skeldergate was investigated: the land between Skeldergate and the Ouse proved to have been a late medieval reclamation. Part of the medieval suburb of Newbiggin was examined outside Monk Bar. The Hospital of St. Mary in the Horsefair was found at Union Terrace, where a twelfth- or early thirteenth-century building was traced through various phases of alteration and addition for use as a Carmelite church, as a hospital, and finally as a school which survived until the seventeenth century.