A new species of Colletes (Hymenoptera: Apoidea: Colletidae) from northern Florida and Georgia, with notes on the Colletes of those states

Colletes ultravalidus Hall & Ascher, new species, is described from several sites in northwestern Florida and southeastern Georgia.  It is a member of the inaequalis species group, very similar to C. validus Cresson, a specialist of Ericaceae, but can be distinguished by an even more elongate malar area and the absence of conspicuous tergal fascia.  Colletes ultravalidus has been found flying from early winter to early spring when it forms nest aggregations in xeric sites adjacent to shrub bog or basin swamp, the habitat of Pieris phyllyreifolia (Hook.) DC. (Ericaceae), the most likely, but as yet unconfirmed, host plant of the new species.  State records of Colletes for Florida and Georgia are reviewed and discrepancies in taxonomy and distributional limits between Stephen’s 1954 revision of the genus and Mitchell’s 1960 monograph of eastern North American bees are noted.  We concur with Stephen that the distributions of several taxa in Colletes are more limited than that reported by Mitchell

Toward an Integrated Model for Raised-Bog Development: Theory and Field Evidence

The development and distribution of Northern mires, including minerotrophic fens and ombrotrophic raised bogs, frequently are presumed to be strongly controlled by the interplay of regional climate and site geomorphology and history. Investigations of these relationships provide insights into long-term trends in ecosystem development by linking geological and landscape-scale processes. In this study, a theoretical model for raised-bog development integrates internal bog hydrodynamics with external factors, including local substrate characteristics, and regional temperature and moisture conditions. The model is used to interpret the development of raised bogs in the Bergslagen region, which coincides with the modern northern distributional limit of those mires in central Sweden. The development of minerotrophic fens that precede bog formation is also considered. Basal radiocarbon dates along surveyed transects are used to assess the pattern and timing of peatland formation and rates of lateral expansion. Previous palynological and lake-level studies from the same region provide independent evidence for changes in Holocene climate. Fen initiation in the region occurred throughout the Holocene under a broad range of environmental conditions. Once established, fens appear to expand faster during moister periods. Locally, substrate slope is an important mediator of fen development, with slopes >0.5% inhibiting lateral expansion. Accumulation of Sphagnum peat, an indicator of raisedbog initiation, occurred from -4000 to 5000 yr BP during relatively dry phases. Rates of lateral expansion were not significantly affected by increasing moisture or by decreasing temperatures until at least 2000 yr BP However, modern geographic trends in cross sectional shape of mires suggest that, at the northern limit of their range today, raised bogs are limited by low temperatures.Organismic and Evolutionary Biolog

Parton cascade description of relativistic heavy-ion collisions at CERN SPS energies ?

We examine Pb+Pb collisions at CERN SPS energy 158 A GeV, by employing the earlier developed and recently refined parton-cascade/cluster-hadronization model and its Monte Carlo implementation. This space-time model involves the dynamical interplay of perturbative QCD parton production and evolution, with non-perturbative parton-cluster formation and hadron production through cluster decays. Using computer simulations, we are able to follow the entwined time-evolution of parton and hadron degrees of freedom in both position and momentum space, from the instant of nuclear overlap to the final yield of particles. We present and discuss results for the multiplicity distributions, which agree well with the measured data from the CERN SPS, including those for K mesons. The transverse momentum distributions of the produced hadrons are also found to be in good agreement with the preliminary data measured by the NA49 and the WA98 collaboration for the collision of lead nuclei at the CERN SPS. The analysis of the time evolution of transverse energy deposited in the collision zone and the energy density suggests an existence of partonic matter for a time of more than 5 fm.Comment: 16 pages including 7 postscript figure

Synergistic and antagonistic effects of land use and non‐native species on community responses to climate change

Climate change, land‐use change and introductions of non‐native species are key determinants of biodiversity change worldwide. However, the extent to which anthropogenic drivers of environmental change interact to affect biological communities is largely unknown, especially over longer time periods. Here, we show that plant community composition in 996 Swedish landscapes has consistently shifted to reflect the warmer and wetter climate that the region has experienced during the second half of the 20th century. Using community climatic indices, which reflect the average climatic associations of the species within each landscape at each time period, we found that species compositions in 74% of landscapes now have a higher representation of warm‐associated species than they did previously, while 84% of landscapes now host more species associated with higher levels of precipitation. In addition to a warmer and wetter climate, there have also been large shifts in land use across the region, while the fraction of non‐native species has increased in the majority of landscapes. Climatic warming at the landscape level appeared to favour the colonization of warm‐associated species, while also potentially driving losses in cool‐associated species. However, the resulting increases in community thermal means were apparently buffered by landscape simplification (reduction in habitat heterogeneity within landscapes) in the form of increased forest cover. Increases in non‐native species, which generally originate from warmer climates than Sweden, were a strong driver of community‐level warming. In terms of precipitation, both landscape simplification and increases in non‐natives appeared to favour species associated with drier climatic conditions, to some extent counteracting the climate‐driven shift towards wetter communities. Anthropogenic drivers can act both synergistically and antagonistically to determine trajectories of change in biological communities over time. Therefore, it is important to consider multiple drivers of global change when trying to understand, manage and predict biodiversity in the future

A Relational Event Approach to Modeling Behavioral Dynamics

This chapter provides an introduction to the analysis of relational event data (i.e., actions, interactions, or other events involving multiple actors that occur over time) within the R/statnet platform. We begin by reviewing the basics of relational event modeling, with an emphasis on models with piecewise constant hazards. We then discuss estimation for dyadic and more general relational event models using the relevent package, with an emphasis on hands-on applications of the methods and interpretation of results. Statnet is a collection of packages for the R statistical computing system that supports the representation, manipulation, visualization, modeling, simulation, and analysis of relational data. Statnet packages are contributed by a team of volunteer developers, and are made freely available under the GNU Public License. These packages are written for the R statistical computing environment, and can be used with any computing platform that supports R (including Windows, Linux, and Mac).

Relativistic Heavy--Ion Collisions in the Dynamical String--Parton Model

We develop and extend the dynamical string parton model. This model, which is based on the salient features of QCD, uses classical Nambu-Got\=o strings with the endpoints identified as partons, an invariant string breaking model of the hadronization process, and interactions described as quark-quark interactions. In this work, the original model is extended to include a phenomenological quantization of the mass of the strings, an analytical technique for treating the incident nucleons as a distribution of string configurations determined by the experimentally measured structure function, the inclusion of the gluonic content of the nucleon through the introduction of purely gluonic strings, and the use of a hard parton-parton interaction taken from perturbative QCD combined with a phenomenological soft interaction. The limited number of parameters in the model are adjusted to $e^+e^-$ and $p$--$p$ data. Utilizing these parameters, the first calculations of the model for $p$--$A$ and $A$--$A$ collisions are presented and found to be in reasonable agreement with a broad set of data.Comment: 26 pages of text with 23 Postscript figures placed in tex

Disappearance of myocardial perfusion defects on prone SPECT imaging: Comparison with cardiac magnetic resonance imaging in patients without established coronary artery disease

<p>Abstract</p> <p>Background</p> <p>It is of great clinical importance to exclude myocardial infarction in patients with suspected coronary artery disease who do not have stress-induced ischemia. The diagnostic use of myocardial perfusion single-photon emission computed tomography (SPECT) in this situation is sometimes complicated by attenuation artifacts that mimic myocardial infarction. Imaging in the prone position has been suggested as a method to overcome this problem.</p> <p>Methods</p> <p>In this study, 52 patients without known prior infarction and no stress-induced ischemia on SPECT imaging were examined in both supine and prone position. The results were compared with cardiac magnetic resonance imaging (CMR) with delayed-enhancement technique to confirm or exclude myocardial infarction.</p> <p>Results</p> <p>There were 63 defects in supine-position images, 37 of which disappeared in the prone position. None of the 37 defects were associated with myocardial infarction by CMR, indicating that all of them represented attenuation artifacts. Of the remaining 26 defects that did not disappear on prone imaging, myocardial infarction was confirmed by CMR in 2; the remaining 24 had no sign of ischemic infarction but 2 had other kinds of myocardial injuries. In 3 patients, SPECT failed to detect small scars identified by CMR.</p> <p>Conclusion</p> <p>Perfusion defects in the supine position that disappeared in the prone position were caused by attenuation, not myocardial infarction. Hence, imaging in the prone position can help to rule out ischemic heart disease for some patients admitted for SPECT with suspected but not documented ischemic heart disease. This would indicate a better prognosis and prevent unnecessary further investigations and treatment.</p

Rotational knee laxity: Reliability of a simple measurement device in vivo

<p>Abstract</p> <p>Background</p> <p>Double bundle ACL reconstruction has been demonstrated to decrease rotational knee laxity. However, there is no simple, commercially-available device to measure knee rotation. The investigators developed a simple, non-invasive device to measure knee rotation. In conjunction with a rigid boot to rotate the tibia and a force/moment sensor to allow precise determination of torque about the knee, a magnetic tracking system measures the axial rotation of the tibia with respect to the femur. This device has been shown to have acceptable levels of test re-test reliability to measure knee rotation in cadaveric knees.</p> <p>Methods</p> <p>The objective of this study was to determine reliability of the device in measuring knee rotation of human subjects. Specifically, the intra-tester reliability within a single testing session, test-retest reliability between two testing sessions, and inter-tester reliability were assessed for 11 male subjects with normal knees.</p> <p>Results</p> <p>The 95% confidence interval for rotation was less than 5° for intra-tester, test-retest, and inter-tester reliability, and the standard error of measurement for the differences between left and right knees was found to be less than 3°.</p> <p>Conclusion</p> <p>It was found that the knee rotation measurements obtained with this device have acceptable limits of reliability for clinical use and interpretation.</p