From AMANDA to IceCube

The first string of the neoteric high energy neutrino telescope IceCube successfully began operating in January 2005. It is anticipated that upon completion the new detector will vastly increase the sensitivity and extend the reach of AMANDA to higher energies. A discussion of the IceCube's discovery potential for extra-terrestrial neutrinos, together with the prospects of new physics derived from the ongoing AMANDA research will be the focus of this paper. Preliminary results of the first antarctic high energy neutrino telescope AMANDA searching in the muon neutrino channel for localized and diffuse excess of extra-terrestrial neutrinos will be reviewed using data collected between 2000 and 2003. Neutrino flux limits obtained with the all-flavor dedicated UHE and cascade analyses will be described. A first neutrino spectrum above one TeV in agreement with atmospheric neutrino flux expectations and no extra-terrestrial contribution will be presented, followed by a discussion of a limit for neutralino CDM candidates annihilating in the center of the Sun.Comment: 15 pages, 8 figures Invited talk contribution at 5th International Conference on Non-accelerator New Physics (NANP 05), Dubna, Russia, 20-25 Jun 200

A model for MRI contrast enhancement using T_1 agents

Contrast in MRI relies on differences in the local environment of water and is often enhanced by using contrast agents. We present a simple model for evaluating the minimal contrast agent concentration required to produce “satisfactory” contrast enhancement in magnetic resonance images. Previous strategies have been based largely on empirical results for specific systems. The present tissue contrast model (TCM) can be applied to “conventional,” targeted, or biochemically responsive agents. The model results are formulated so that only a small number of parameters are required to analyze a given scenario. The TCM is a particularly useful tool in the development of new classes of magnetic resonance contrast media. These agents will have the ability to target specific cells or tissue, and perhaps be able to report on their physiological status. As an example of the applicability of the TCM, we test it against in vivo magnetic resonance microscopy results in frog embryos that have focal cell populations labeled with contrast agent by using calibrated single-cell microinjection techniques

Ocorrência de nematóides das galhas das raizes, Meloidogyne incognita (Kofoid & White, 1919) Chitwood, 1949 e M. javanica (Treub, 1885) Chitwood, 1949 em Bracatinga Mimosa scabrella (Benth.) no Estado do Paraná.

bitstream/item/101253/1/PA-1983-Iede-OcorrenciaNematoides.pd

Bayesian calibration of a soil organic carbon model using Δ¹⁴C measurements of soil organic carbon and heterotrophic respiration as joint constraints

Soils of temperate forests store significant amounts of organic matter and are considered to be net sinks of atmospheric CO₂. Soil organic carbon (SOC) turnover has been studied using the Δ¹⁴C values of bulk SOC or different SOC fractions as observational constraints in SOC models. Further, the Δ¹⁴C values of CO₂ that evolved during the incubation of soil and roots have been widely used together with Δ¹⁴C of total soil respiration to partition soil respiration into heterotrophic respiration (HR) and rhizosphere respiration. However, these data have not been used as joint observational constraints to determine SOC turnover times. Thus, we focus on (1) how different combinations of observational constraints help to narrow estimates of turnover times and other parameters of a simple two-pool model, the Introductory Carbon Balance Model (ICBM); (2) whether relaxing the steady-state assumption in a multiple constraints approach allows the source/sink strength of the soil to be determined while estimating turnover times at the same time. To this end ICBM was adapted to model SOC and SO¹⁴C in parallel with litterfall and the Δ¹⁴C of litterfall as driving variables. The Δ¹⁴C of the atmosphere with its prominent bomb peak was used as a proxy for the Δ¹⁴C of litterfall. Data from three spruce-dominated temperate forests in Germany and the USA (Coulissenhieb II, Solling D0 and Howland Tower site) were used to estimate the parameters of ICBM via Bayesian calibration. Key findings are as follows: (1) the joint use of all four observational constraints (SOC stock and its Δ¹⁴C, HR flux and its Δ¹⁴C) helped to considerably narrow turnover times of the young pool (primarily by Δ¹⁴C of HR) and the old pool (primarily by Δ¹⁴C of SOC). Furthermore, the joint use of all observational constraints made it possible to constrain the humification factor in ICBM, which describes the fraction of the annual outflux from the young pool that enters the old pool. The Bayesian parameter estimation yielded the following turnover times (mean ± standard deviation) for SOC in the young pool: Coulissenhieb II 1.1 ± 0.5 years, Solling D0 5.7 ± 0.8 years and Howland Tower 0.8 ± 0.4 years. Turnover times for the old pool were 377 ± 61 years (Coulissenhieb II), 313 ± 66 years (Solling D0) and 184 ± 42 years (Howland Tower), respectively. (2) At all three sites the multiple constraints approach was not able to determine if the soil has been losing or storing carbon. Nevertheless, the relaxed steady-state assumption hardly introduced any additional uncertainty for the other parameter estimates. Overall the results suggest that using Δ¹⁴C data from more than one carbon pool or flux helps to better constrain SOC models

RG-improved single-particle inclusive cross sections and forward-backward asymmetry in ttˉt\bar t production at hadron colliders

We use techniques from soft-collinear effective theory (SCET) to derive renormalization-group improved predictions for single-particle inclusive (1PI) observables in top-quark pair production at hadron colliders. In particular, we study the top-quark transverse-momentum and rapidity distributions, the forward-backward asymmetry at the Tevatron, and the total cross section at NLO+NNLL order in resummed perturbation theory and at approximate NNLO in fixed order. We also perform a detailed analysis of power corrections to the leading terms in the threshold expansion of the partonic hard-scattering kernels. We conclude that, although the threshold expansion in 1PI kinematics is susceptible to numerically significant power corrections, its predictions for the total cross section are in good agreement with those obtained by integrating the top-pair invariant-mass distribution in pair invariant-mass kinematics, as long as a certain set of subleading terms appearing naturally within the SCET formalism is included.Comment: 55 pages, 14 figures, 6 table

Upgrade of the Glasgow photon tagging spectrometer for Mainz MAMI-C

The Glasgow photon tagging spectrometer at Mainz has been upgraded so that it can be used with the 1500 MeV electron beam now available from the Mainz microtron MAMI-C. The changes made and the resulting properties of the spectrometer are discussed.Comment: 20 pages, 12 figure

High-Energy Neutrino Astronomy

Kilometer-scale neutrino detectors such as IceCube are discovery instruments covering nuclear and particle physics, cosmology and astronomy. Examples of their multidisciplinary missions include the search for the particle nature of dark matter and for additional small dimensions of space. In the end, their conceptual design is very much anchored to the observational fact that Nature accelerates protons and photons to energies in excess of $10^{20}$ and $10^{13}$ eV, respectively. The cosmic ray connection sets the scale of cosmic neutrino fluxes. In this context, we discuss the first results of the completed AMANDA detector and the reach of its extension, IceCube. Similar experiments are under construction in the Mediterranean. Neutrino astronomy is also expanding in new directions with efforts to detect air showers, acoustic and radio signals initiated by super-EeV neutrinos.Comment: 9 pages, Latex2e, uses ws-procs975x65standard.sty (included), 4 postscript figures. To appear in Proceedings of Thinking, Observing, and Mining the Universe, Sorrento, Italy, September 200

Visualizing Diffusion Tensor Images of the Mouse Spinal Cord

Within biological systems water molecules undergo continuous stochastic Brownian motion. The rate of this diffusion can give clues to the structure of underlying tissues. In some tissues the rate is anisotropic - faster in some directions than others. Diffusion-rate images are second-order tensor fields and can be calculated from diffusion-weighted magnetic resonance images. A 2D diffusion tensor image (DTI) and an associated anatomical scalar field, created during the tensor calculation, define seven dependent values at each spatial location. Understanding the interrelationships among these values is necessary to understand the data. We present two new methods for visually representing DTIs. The first method displays an array of ellipsoids where the shape of each ellipsoid represents one tensor value. The novel aspect of this representation is that the ellipsoids are all normalized to approximately the same size so that they can be displayed in context. The second method uses concepts from oil painting to represent the seven-valued data with multiple layers of varying brush strokes. Both methods successfully display most or all of the information in DTIs and provide exploratory methods for understanding them. The ellipsoid method has a simpler interpretation and explanation than the painting-motivated method; the painting-motivated method displays more of the information and is easier to read quantitatively. We demonstrate the methods on images of the mouse spinal cord. The visualizations show significant differences between spinal cords from mice suffering from Experimental Allergic Encephalomyelitis (EAE) and spinal cords from wild-type mice. The differences are consistent with pathology differences shown histologically and suggest that our new non-invasive imaging methodology and visualization of the results could have early diagnostic value for neurodegenerative diseases

Measurement of the 6Li(e,e'p) reaction cross sections at low momentum transfer

The triple differential cross sections for the 6Li(e,e'p) reaction have been measured in the excitation energy region from 27 to 46 MeV in a search for evidence of the giant dipole resonance (GDR) in 6Li. The cross sections have no distinct structures in this energy region, and decrease smoothly with the energy transfer. Angular distributions are different from those expected with the GDR. Protons are emitted strongly in the momentum-transfer direction. The data are well reproduced by a DWIA calculation assuming a direct proton knockout process.Comment: 19 pages, 7 figures, revised text, to be published in Nucl. Phys.

A photon calorimeter using lead tungstate crystals for the CEBAF Hall A Compton polarimeter

The performances of the calorimeter of the Jlab Hall A Compton Polarimeter have been measured using the Mainz tagged photon beam.Comment: 13 page