Integrated analyses of litho- and biofacies in a Pliocene cyclothemic, alluvial to shallow marine succession (Tuscany, Italy)

Lithofacies analysis of the upper part of the Pliocene succession of the Valdelsa basin (central Italy) unravelled a number of depositional environments, ranging from alluvial plain to coastal, to marine. Strata are arranged in a hierarchy of elementary and composite unconformity-bounded units. A palaeoecological study of macro- (molluscs) and microfossils (pollen, dinocysts, foraminifera) allowed to finely reconstruct sub-environments within fine-grained terrestrial, coastal and marine deposits and thence to track the spatial and temporal change of physical conditions. The stacking pattern of sedimentary units highlights the lateral switching of onshore-offshore gradients and documents relative sea-level changes. These units are interpreted in a sequence stratigraphic framework. Elementary depositional sequences are arranged to form six composite depositional sequences, in turn encased within two major synthems. This hierarchy of unconformity-bounded sedimentary units suggests that sea-level variation has occurred at different time-frequencies. Glacio-eustasy and active tectonism are discussed as the main forcing factors regulating the different scales of sedimentary cyclicity.     

Alternative rib bone biopsy measurements to estimate changes in skeletal mineral reserves in cattle

Rib bone biopsy samples are often used to estimate changes in skeletal mineral reserves in cattle but differences in sampling procedures and the bone measurements reported often make interpretation and comparisons among experiments difficult. ‘Full-core’ rib bone biopsy samples, which included the external cortical bone, internal cortical bone and trabecular bone (CB_ext, CB_int and Trab, respectively), were obtained from cattle known to be in phosphorus (P) adequate (P_adeq) or severely P-deficient (P_defic) status. Experiments 1 and 2 examined growing steers and Experiment 3 mature breeder cows. The thickness of cortical bone, specific gravity (SG), and the amount and concentration of ash and P per unit fresh bone volume, differed among CB_ext, CB_int and Trab bone. P concentration (mg/cc) was closely correlated with both SG and ash concentrations (pooled data, r=0.99). Thickness of external cortical bone (CBT_ext) was correlated with full-core P concentration (FC-P_conc) (pooled data, r=0.87). However, an index, the amount of P in CB_ext per unit surface area of CB_ext (PSACB; mg P/mm²), was more closely correlated with the FC-P_conc (pooled data, FC-P_conc=37.0+146×PSACB; n=42, r=0.94, RSD=7.7). Results for measured or estimated FC-P_conc in 10 published studies with cattle in various physiological states and expected to be P_adeq or in various degrees of P_defic status were collated and the ranges of FC-P_conc indicative of P adequacy and P deficiency for various classes of cattle were evaluated. FC-P_conc was generally in the range 130 to 170 and 100 to 120 mg/cc fresh bone in P_adeq mature cows and young growing cattle, respectively. In conclusion, the FC-P_conc could be estimated accurately from biopsy samples of CB_ext. This allows comparisons between studies where full-core or only CB_ext biopsy samples of rib bone have been obtained to estimate changes in the skeletal P status of cattle and facilitates evaluation of the P status of cattle.     

La glande coquillière non pigmentée d'Artemia salina Leach

Résumé Ce travail concerne l'étude morphologique de la glande coquillière non pigmentée ou blanche d'Artemia salina. La structure de celle-ci est comparée à celle de la glande coquillière brune de la même espèce. Les différences sont apparemment plus fondamentales qu'une simple variation de la quantité de produit de sécrétion ou de la pigmentation des cellules.Là où les glandes coquillières brunes formeraient la coque chez les animaux ovipares les glandes coquillières blanches pourraient sécréter les produits nécessaires ou utiles au développement des nauplii chez les animaux ovovivipares.

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Morphological study of the white shell gland of Artemia salina leach

Summary The white shell glands of Artemia salina have been investigated. Our results, compared to those obtained in the brown-coloured shell glands, occuring within the same species, reveal differences not only in the aspect of the secretory granules but also in the structure of the nucleus and the cytoplasm. These differences between the two types of glands appear to be more striking than a simple variation in the quantity of secretion or in the pigmentation of the gland. As the brown glands are supposed to contribute to the formation of the egg shells in oviparous animals, the secretion of white glands could favour the development of nauplii in ovoviviparous animals.

     

The problematic cemented Devonian brachiopod Schuchertellopsis durbutensis Maillieux, 1939

The Devonian cemented brachiopod Schuchertellopsis durbutensis has proved difficult to classify and its possible taxonomic relationships are unknown. Morphologically Schuchertellopsis resembles more closely members of the Orthotetidina than the Davidsoniidina. Examination of the shell structure, a key diagnostic feature of the Orthotetidina, shows that Schuchertellopsis has the cross laminar secondary shell typical of all orthotetidines. However, the presence of both pseudopunctate and incipient an extropunctate fabric within the ventral valve is unique amongst orthotetidine brachiopods and is thought to represent a phase of shell fabric experimentation. Schuchertellopsis probably fits most comfortably within the Schuchertellidae, and is the earliest representative of that family.     

Influence of larval outbreaks on the climate reconstruction potential of an Arctic shrub

Arctic shrubs have a strong potential for climate and environmental reconstructions in the chronically understudied regions of the high northern latitudes. The climate dynamics of these regions are important to understand because of large-scale feedbacks to the global climate system. However, little is known about other factors influencing shrub ring growth, possibly obscuring their climate signal. For example, as of yet we are not able to differentiate between herbivory or climatically induced growth depressions. Here, we use one of the most common Arctic shrubs, Alnus viridis as a test case to address this question. We sampled Alnus in Kobbefjord, Greenland, measured shrub-ring width and cell wall thickness and built site chronologies of each parameter. We analysed climate-growth relationships, tested their stability over time and employed a pointer-year analysis to detect growth depressions. We employed bootstrapped transfer function stability tests (BTFS) to assess the suitability of our shrub chronologies for climate reconstruction. Correlations with climate data showed strong significantly positive and stable correlations between summer temperature and ring-width with the exception of the recent decade. A climate reconstruction model failed stability tests, when the complete period of record was used for calibration and verification. Wood anatomy analysis uncovered the occurrence of unusual cell structure (very thin cell walls) in the exceptionally narrow ring of 2004, a recorded insect outbreak year in other parts of Greenland. When excluding the affected ring and a recovery period, the reconstruction model passed all tests, suggesting that the unusual 2004 ring was not climate driven, but rather the result of an insect attack. When combining anatomical analysis with traditional ring-width measurements, we move a step further in potentially distinguishing small rings caused by insect attacks from small rings formed in climatically challenging years. While this study does not provide unambiguous evidence, it does provide potential useful methodological combinations to enable more robust climate reconstructions in areas where climatic records are extremely sparse.     

Photosynthesis of herbaceous plants from nutrient-poor tropical forests

Photosynthetic characteristics, specific leaf mass, chlorophyll and total leaf nitrogen concentrations of four herbaceous plants (Dicranopteris linearis, Hanguana malayana, Pentaphragma ellipticum, Tacca integrifolia) from nutrient-poor tropical forests showed that all these plants were well-adapted to their natural growth environments. No photoinhibition was observed even in the understorey plants. This revised version was published online in June 2006 with corrections to the Cover Date.     

The influence of basic plan parameters on calculated small field output factors – A multicenter study

PurposeThe influence of basic plan parameters such as slice thickness, grid resolution, algorithm type and field size on calculated small field output factors (OFs) was evaluated in a multicentric study.Methods and materialsThree computational homogeneous water phantoms with slice thicknesses (ST) 1, 2 and 3 mm were shared among twenty-one centers to calculate OFs for 1x1, 2x2 and 3x3 cm² field sizes (FSs) (normalized to 10x10 cm² FS), with their own treatment planning system (TPS) and the energy clinically used for stereotactic body radiation therapy delivery. OFs were calculated for each combination of grid resolution (GR) (1, 2 and 3 mm) and ST and finally compared with the OFs measured for the TPS commissioning. A multivariate analysis was performed to test the effect of basic plan parameters on calculated OFs.ResultsA total of 509 data points were collected. Calculated OFs are slightly higher than measured ones. The multivariate analysis showed that Center, GR, algorithm type, and FS are predictive variables of the difference between calculated and measured OFs (p < 0.001). As FS decreases, the spread in the difference between calculated and measured OFs became larger when increasing the GR. Monte Carlo and Analytical Anisotropic Algorithms, presented a dependence on GR (p < 0.01), while Collapsed Cone Convolution and Acuros did not. The effect of the ST was found to be negligible.ConclusionsModern TPSs slightly overestimate the calculated small field OFs compared with measured ones. Grid resolution, algorithm, center number and field size influence the calculation of small field OFs.