The distributions of a wide range of taxonomic groups are expanding polewards

Evidence is accumulating of shifts in species' distributions during recent climate warming. However, most of this information comes predominantly from studies of a relatively small selection of taxa (i.e., plants, birds and butterflies), which may not be representative of biodiversity as a whole. Using data from less well‐studied groups, we show that a wide variety of vertebrate and invertebrate species have moved northwards and uphill in Britain over approximately 25 years, mirroring, and in some cases exceeding, the responses of better‐known groups.     

Estimation of the Temporal Course of Evoked Secretion of Transmitter Quanta in the Frog Neuromuscular Junction

In experiments on the cutaneothoracic muscle of the frog, we recorded, using the technique of two-electrode voltage clamp at a normal Ca²⁺ concentration (1.8 mM), multiquantum end-plate currents (EPC) and miniature uniquantum EPC (mEPC). Multiquantum signals, when compared with uniquantum currents, were characterized by longer leading and trailing edges. The quantum composition of multiquantum signals estimated according to the ratios of EPC and mEPC amplitudes was, on average, 27% lower than that calculated according to the ratios of their integral values (areas). These data demonstrate that stimulus-evoked transmitter secretion from the motor nerve endings is noticeably asynchronous. Based on the parameters of the experimental EPC and mEPC, we estimated the temporal course of evoked secretion using various techniques: spectral analysis, a system of linear equations, and Van der Kloot's method. Using convolution with uniquantum signals, we found that spectral analysis is the best technique for such estimation. Calculated parameters of the temporal course of secretion were the following: risetime 0.20 msec and decay time constant 0.33 msec. The respective distribution significantly differed from that of the synaptic delays of extracellularly recorded uniquantum EPC by longer durations (150-200%) of the leading and trailing edges. We hypothesize that these differences are related to the geometry of the junction and the temporal sequence of switching on of the active zones in the nerve ending upon their activation by spreading action potentials. Factors influencing the temporal course of evoked secretion of the transmitter in the junction under study (its asynchronicity, in particular) are discussed.     

Trajectory log file sensitivity: A critical analysis using DVH and EPID

Aim

The aim of this study was to investigate the sensitivity of the trajectory log file based quality assurance to detect potential errors such as MLC positioning and gantry positioning by comparing it with EPID measurement using the most commonly used criteria of 3%/3?mm.

Répartiteur de dose des médicaments radiopharmaceutiques : contrôle qualité sur deux sites hospitaliers et comparaison avec la législation en vigueur en France

An increasing number of nuclear medicine departments are equipped with automated measurement systems for the preparation of radiopharmaceuticals, with the main aim of minimising technician's irradiation. However, the automatic measurement of the patient activity differs from the manual measurement in material and method. In this context, the objective of the present study was to test the performances of one of these systems, the Unidose by TRASIS^®, in two newly equipped hospitals. The particularity of these systems is they are made up of two dose calibrators: the entrance calibrator (well chamber) and the exit calibrator (probe). Controls were performed on both of these dose calibrators. The results obtained, as well as the methodology employed, were then compared with the regulatory requirements in France. The results found are coherent between the two sites and have highlighted several non-conformities compared to the current regulations, part of which concerning the carpule dose calibrator, which is actually a probe. These results raise the question of a suitable regulation for the new automated measurement systems in nuclear medicine.     

Residue packing in globular and intrinsically disordered proteins

Intrinsically disordered proteins (IDPs)/regions do not have well‐defined secondary and tertiary structures, however, they are functional and it is critical to gain a deep understanding of their residue packing. The shape distributions methodology, which is usually utilized in pattern recognition, clustering, and classification studies in computer science, may be adopted to study the residue packing of the proteins. In this study, shape distributions of the globular proteins and IDPs were obtained to shed light on the residue packing of their structures. The shape feature that was used is the sphericity of tetrahedra obtained by Delaunay Tessellation of points of Cα coordinates. Then the sphericity probability distributions were compared by using Principal Component Analysis. This computational structural study shows that the set of IDPs constitute a more diverse set than the set of globular proteins in terms of the geometrical properties of their network structures.     

Japanese maple (Acer palmatum var. Matsumurae, Aceraceae) recruitment patterns: seeds, seedlings, and saplings in relation to conspecific adult neighbors

We analyzed the spatial patterns among seeds, seedlings, saplings, and conspecific adult trees of the cool-temperate tree species Acer palmatum var. Matsumurae in a conifer-hardwood mixed forest in northern Japan, using two models that consider the influence of each adult within the neighborhood of the offspring. The results showed that recruitment patterns of each stage could be characterized and that significant shifts occur between successive stages. Sound seeds were more widely dispersed than unsound seeds; the mean dispersal distance (MDD) was 41.5 m for sound seeds, but only 12.6 m for unsound seeds. Most seedlings were located near conspecific adult trees, with a MDD of 14.3 m. Saplings, however, were more dispersed away from conspecific adult trees, with an MDD of more than 35 m. Light and gap distributions did not strongly affect the spatial distribution of the offspring; most saplings were located under nonconspecific canopies. These results suggest that the recruitment pattern of Japanese maple offspring is strongly affected by conspecific adult neighbors, rather than by light and gap distributions, with close proximity to conspecific adult trees reducing the growth and survival of seedlings during the transition to saplings.     

Unifying and distinguishing diversity ordering methods for comparing communities

Diversity indices have been widely used in ecological research, but they remain problematic in that different indices may rank communities inconsistently. This problem can be solved by using diversity ordering methods, the output of which is a diversity profile in graphical form for each community being compared. In this paper, we demonstrate that existing diversity ordering methods can be classified into four groups and that within-group methods are essentially equivalent, while among-group methods are not. We find that the intrinsic diversity-related methods—i.e., the group containing the right tail-sum method, the logarithmic dominance plot, the majorization method, and the k-dominance plot—provide the most stringent test of diversity ordering, and we recommend the right tail-sum method as the method of preference for practical purposes.     

Scale, time, space, and predictability: species distributions of preimaginal black flies (Diptera: Simuliidae)

This study examines species-specific distributions of preimaginal black flies (Diptera: Simuliidae) over two large spatial scales (within and across ecoregions) and two seasons (spring and summer). The study area in the western two-thirds of South Carolina, United States, was divided into three ecoregions (Mountains, Piedmont, Sandhills). The mean correct classification of species distributions among stream sites was 81.3%. Predictability of species distributions varied with spatial scale, location, and time. Species occurrence was not independent of ecoregion; distributions of 12 of the 13 species examined at this scale were predictable on the basis of changes in water column (temperature, percentage dissolved oxygen) and channel characters (velocity, streambed-particle size). However, with the exception of the Mountains during the summer, predicting species distributions within ecoregions was far less successful than predicting distributions across these regions; predictability was particularly poor in the Sandhills. Seasonal effects on predictability were most pronounced in the Mountains. As stream sites became more homogeneous, predictive capability declined. Species-level identifications, aided by cytogenetic techniques, were of paramount importance in recognizing the association between species distributions and stream conditions, emphasizing that considerable ecological information is lost when species are not considered. This study emphasizes the critical role of taxonomic resolution, linked with spatial and temporal scale of observation, in elucidating patterns of species assemblages. It also demonstrates that predictability of species distributions at a fixed scale can vary with geographic location and time. Received: 2 May 1997 / Accepted: 22 September 1997