1,516 research outputs found
Population Regulation of Gypsy Moth (Lepidoptera: Lymantriidae) by Parasitoids: Does Spatial Density Dependence Lead to Temporal Density Dependence?
In 1987, four gypsy moth, Lymantria dispar, (L.) densities were established in eight 1-ha plots in western Massachusetts, ranging from 50,000 to 1.4 M neonates per hectare. Two tachinid parasitoid species, Compsilura concinnata (Meigen) and Parasetigena silvestris (Robineau-Desvoidy), exhibited spatial density-dependent parasistism and C. concinnata was the major source of gypsy moth mortality. This study investigated whether spatial density-dependent mortality in 1987 translated into temporal density-dependent mortality of experimental gypsy moth populations created the following year (1988). C. concinnata was responsible for the largest percentage of gypsy moth mortality again in 1988, however, overall mortality caused by C. concinnata in 1988 was considerably less than in 1987. Gypsy moth mortality caused by P. silvestris was greater in 1988. The killing power of either parasitoid in 1988 were not linearly related to the estimated density of the parasitoids produced in the previous year. We saw no evidence for a between-generation numerical response (1-ha scale) of either the generalist parasitoid, C. concinnata, or the specialist parasitoid, P. silvestris, between 1987 and 198
Ion Sources for MedAustron
The MedAustron Ion therapy center will be constructed in Wiener Neustadt (Austria) in the vicinity of Vienna. Its accelerator complex consists of four ion sources, a linear accelerator, a synchrotron and a beam delivery system to the three medical treatment rooms and to the research irradiation room. The ion sources shall deliver beams of H31+, C4+ and light ions with utmost reliability and stability. This paper describes the features of the ion sources presently planned for the MedAustron facility; such as ion source main parameters, gas injection, temperature control and cooling systems. A dedicated beam diagnostics technique is proposed in order to characterize ECR ions beams; in the first drift region after the ion source, a fraction of the mixed beam is selected via moveable aperture. With standard beam diagnostics, we then aim to produce position-dependant observables such as ion-current density, beam energy distribution and emittance for each charge states to be compared to simulations of ECR e-heating, plasma simulation, beam formation and transport
Simulating ice core 10Be on the glacial–interglacial timescale
10Be ice core measurements are an important tool for paleoclimate research, e.g., allowing for the reconstruction of past solar activity or changes in the geomagnetic dipole field. However, especially on multi-millennial timescales, the share of production and climate-induced variations of respective 10Be ice core records is still up for debate. Here we present the first quantitative climatological model of the 10Be ice concentration up to the glacial–interglacial timescale. The model approach is composed of (i) a coarse resolution global atmospheric transport model and (ii) a local 10Be air–firn transfer model. Extensive global-scale observational data of short-lived radionuclides as well as new polar 10Be snow-pit measurements are used for model calibration and validation. Being specifically configured for 10Be in polar ice, this tool thus allows for a straightforward investigation of production- and non-production-related modulation of this nuclide. We find that the polar 10Be ice concentration does not immediately record the globally mixed cosmogenic production signal. Using geomagnetic modulation and revised Greenland snow accumulation rate changes as model input, we simulate the observed Greenland Summit (GRIP and GISP2) 10Be ice core records over the last 75 kyr (on the GICC05modelext timescale). We show that our basic model is capable of reproducing the largest portion of the observed 10Be changes. However, model–measurement differences exhibit multi-millennial trends (differences up to 87% in case of normalized to the Holocene records) which call for closer investigation. Focusing on the (12–37) b2k (before the year AD 2000) period, mean model–measurement differences of 30% cannot be attributed to production changes. However, unconsidered climate-induced changes could likely explain the model–measurement mismatch. In fact, the 10Be ice concentration is very sensitive to snow accumulation changes. Here the reconstructed Greenland Summit (GRIP) snow accumulation rate record would require revision of +28% to solely account for the (12–37) b2k model–measurement differences
Search for supernova-produced 60Fe in a marine sediment
An 60Fe peak in a deep-sea FeMn crust has been interpreted as due to the
signature left by the ejecta of a supernova explosion close to the solar system
2.8 +/- 0.4 Myr ago [Knie et al., Phys. Rev. Lett. 93, 171103 (2004)]. To
confirm this interpretation with better time resolution and obtain a more
direct flux estimate, we measured 60Fe concentrations along a dated marine
sediment. We find no 60Fe peak at the expected level from 1.7 to 3.2 Myr ago.
However, applying the same chemistry used for the sediment, we confirm the 60Fe
signal in the FeMn crust. The cause of the discrepancy is discussed.Comment: 15 pages, 5 figures, submitted to PR
Interactional positioning and narrative self-construction in the first session of psychodynamic-interpersonal psychotherapy
The purpose of this study is to identify possible session one indicators of end of treatment psychotherapy outcome using the framework of three types of interactional positioning; client’s self-positioning, client’s positioning between narrated self and different partners, and the positioning between client and therapist. Three successful cases of 8-session psychodynamic-interpersonal (PI) therapy were selected on the basis of client Beck Depression Inventory scores. One unsuccessful case was also selected against which identified patterns could be tested. The successful clients were more descriptive about their problems and demonstrated active rapport-building, while the therapist used positionings expressed by the client in order to explore the positionings developed between them during therapy. The unsuccessful case was characterized by lack of positive self-comment, minimization of agentic self-capacity, and empathy-disrupting narrative confusions. We conclude that the theory of interactional positioning has been useful in identifying patterns worth exploring as early indicators of success in PI therapy
Hidden Consequence of Active Local Lorentz Invariance
In this paper we investigate a hidden consequence of the hypothesis that
Lagrangians and field equations must be invariant under active local Lorentz
transformations. We show that this hypothesis implies in an equivalence between
spacetime structures with several curvature and torsion possibilities.Comment: Some misprints appearing in the published version have been correcte
Locally Anisotropic Structures and Nonlinear Connections in Einstein and Gauge Gravity
We analyze local anisotropies induced by anholonomic frames and associated
nonlinear connections in general relativity and extensions to affine Poincare
and de Sitter gauge gravity and different types of Kaluza-Klein theories. We
construct some new classes of cosmological solutions of gravitational field
equations describing Friedmann-Robertson-Walker like universes with rotation
(ellongated and flattened) ellipsoidal or torus symmetry.Comment: 37 page
A rare presentation of atypical demyelination: tumefactive multiple sclerosis causing Gerstmann's syndrome
r. KS has been supported by a Higher Education Funding Council for
England (HEFCE) Clinical Senior Lectureshi
Hamiltonian Poincar\'e Gauge Theory of Gravitation
We develop a Hamiltonian formalism suitable to be applied to gauge theories
in the presence of Gravitation, and to Gravity itself when considered as a
gauge theory. It is based on a nonlinear realization of the Poincar\'e group,
taken as the local spacetime group of the gravitational gauge theory, with
as the classification subgroup. The Wigner--like rotation induced by
the nonlinear approach singularizes out the role of time and allows to deal
with ordinary vectors. We apply the general results to the
Einstein--Cartan action. We study the constraints and we obtain Einstein's
classical equations in the extremely simple form of time evolution equations of
the coframe. As a consequence of our approach, we identify the
gauge--theoretical origin of the Ashtekar variables.Comment: 38 pages, plainTe
Clinical significance of VEGF-A, -C and -D expression in esophageal malignancies
Vascular endothelial growth factors ( VEGF)- A, - C and - D are members of the proangiogenic VEGF family of glycoproteins. VEGF-A is known to be the most important angiogenic factor under physiological and pathological conditions, while VEGF-C and VEGF-D are implicated in the development and sprouting of lymphatic vessels, so called lymphangiogenesis. Local tumor progression, lymph node metastases and hematogenous tumor spread are important prognostic factors for esophageal carcinoma ( EC), one of the most lethal malignancies throughout the world. We found solid evidence in the literature that VEGF expression contributes to tumor angiogenesis, tumor progression and lymph node metastasis in esophageal squamous cell carcinoma ( SCC), and many authors could show a prognostic value for VEGF-assessment. In adenocarcinoma (AC) of the esophagus angiogenic properties are acquired in early stages, particularly in precancerous lesions like Barrett's dysplasia. However, VEGF expression fails to give prognostic information in AC of the esophagus. VEGF-C and VEGF-D were detected in SCC and dysplastic lesions, but not in normal mucosa of the esophagus. VEGF-C expression might be associated with lymphatic tumor invasion, lymph node metastases and advanced disease in esophageal SCC and AC. Therapeutic interference with VEGF signaling may prove to be a promising way of anti-angiogenic co-treatment in esophageal carcinoma. However, concrete clinical data are still pending
- …