On the Photometric Accuracy of RHESSI Imaging and Spectrosocopy

We compare the photometric accuracy of spectra and images in flares observed with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI)}spacecraft. We test the accuracy of the photometry by comparing the photon fluxes obtained in different energy ranges from the spectral-fitting software SPEX with those fluxes contained in the images reconstructed with the Clean, MEM, MEM-Vis, Pixon, and Forward-fit algorithms. We quantify also the background fluxes, the fidelity of source geometries, and spatial spectra reconstructed with the five image reconstruction algorithms. We investigate the effects of grid selection, pixel size, field-of-view, and time intervals on the quality of image reconstruction. The detailed parameters and statistics are provided in an accompanying CD-ROM and web page. We find that Forward-fit, Pixon, and Clean have a robust convergence behavior and a photometric accuracy in the order of a few percents, while MEM does not converge optimally for large degrees of freedom (for large field-of-views and/or small pixel sizes), and MEM-Vis suffers in the case of time-variable sources. This comparative study documents the current status of the RHESSI spectral and imaging software, one year after launch.Comment: 2 Figures, full version on http://www.lmsal.com/~aschwand/eprints/2003_photo/index.htm

Quantum Phase Transition in the Itinerant Antiferromagnet (V0.9Ti0.1)2O3

Quantum-critical behavior of the itinerant electron antiferromagnet (V0.9Ti0.1)2O3 has been studied by single-crystal neutron scattering. By directly observing antiferromagnetic spin fluctuations in the paramagnetic phase, we have shown that the characteristic energy depends on temperature as c_1 + c_2 T^{3/2}, where c_1 and c_2 are constants. This T^{3/2} dependence demonstrates that the present strongly correlated d-electron antiferromagnet clearly shows the criticality of the spin-density-wave quantum phase transition in three space dimensions.Comment: 4 pages, 4 figure

Simulation of current-induced microwave oscillation in geometrically confined domain wall

We studied magnetization dynamics of a geometrically confined domain wall under dc current by solving simultaneously the Landau-Lifshitz-Gilbert equation and diffusion equation for spin accumulation. We showed that the oscillation motion of the domain wall is driven by the spin-transfer torque and the dc current is converted to the ac voltage signal. The results means that the geometrically confined domain wall is applicable as a source of microwave oscillator.Comment: 3 pages, 3 figure

Comparison of Effects on Gene Expression Activity of Low-Molecular-Weight Lychee Fruit Polyphenol (Oligonol®), Adenosine, and Minoxidil in Human Dermal Papilla Cells

Background: Oligonol® (OLG) is a functional food product and ingredient for cosmetics derived from a lychee fruit polyphenol. It has been reported to act on the skin as an anti-inflammatory and prevent UVB-induced skin damage.Aim: In this study, with the aim of exploring new functionalities of OLG on the scalp, we investigated the effect of OLG on human dermal papilla cells by comparing with adenosine and minoxidil at the genetic level.Method: OLG, adenosine, and minoxidil were applied to human dermal papilla cell lines for 24 h, after which VEGF, FGF-7, WNT5a, and WNT10a mRNA expressions were measured by real-time PCR analysis. Additionally, using DNA microarrays, we investigated the effect on 205 inflammation-related genes.Result: Consequently, in human dermal papilla cell lines, FGF-7 and WNT10a mRNA expression were observed in 100 µg/mL OLG-supplemented cells. The results of the DNA microarray analysis showed that 10 genes were suppressed by OLG.Conclusions: OLG may be expected to affect function of human dermal papilla cell by regulating the expression of genes related to cell proliferation and inflammation

String correlation functions of the spin-1/2 Heisenberg XXZ chain

We calculate certain string correlation functions, originally introduced as order parameters in integer spin chains, for the spin-1/2 XXZ Heisenberg chain at zero temperature and in the thermodynamic limit. For small distances, we obtain exact results from Bethe Ansatz and exact diagonalization, whereas in the large-distance limit, field-theoretical arguments yield an asymptotic algebraic decay. We also make contact with two-point spin-correlation functions in the asymptotic limit.Comment: 23 pages, 4 figures. An incomplete discussion on the limit to the spin-spin correlation function is corrected on page 1

Lepton Flavor Violation in the SUSY-GUT Models with Lopsided Mass Matrix

The tiny neutrino masses measured in the neutrino oscillation experiments can be naturally explained by the supersymmetric see-saw mechanism. If the supersymmetry breaking is mediated by gravity, the see-saw models may predict observable lepton flavor violating effects. In this work, we investigate the lepton flavor violating process $\mu\to e\gamma$ in the kind of neutrino mass models based on the idea of the ``lopsided'' form of the charged lepton mass matrix. The constraints set by the muon anomalous magnetic moment are taken into account. We find the present models generally predict a much larger branching ratio of $\mu\to e\gamma$ than the experimental limit. Conversely, this process may give strong constraint on the lepton flavor structure. Following this constraint we then find a new kind of the charged lepton mass matrix. The feature of the structure is that both the elements between the 2-3 and 1-3 generations are ``lopsided''. This structure produces a very small 1-3 mixing and a large 1-2 mixing in the charged lepton sector, which naturally leads to small $Br(\mu\to e\gamma)$ and the LMA solution for the solar neutrino problem.Comment: 24 pages, 8 figure

Exact evaluation of density matrix elements for the Heisenberg chain

We have obtained all the density matrix elements on six lattice sites for the spin-1/2 Heisenberg chain via the algebraic method based on the quantum Knizhnik-Zamolodchikov equations. Several interesting correlation functions, such as chiral correlation functions, dimer-dimer correlation functions, etc... have been analytically evaluated. Furthermore we have calculated all the eigenvalues of the density matrix and analyze the eigenvalue-distribution. As a result the exact von Neumann entropy for the reduced density matrix on six lattice sites has been obtained.Comment: 33 pages, 4 eps figures, 3 author

Magnetic spin excitations in Mn doped GaAs : A model study

We provide a quantitative theoretical model study of the dynamical magnetic properties of optimally annealed Ga$_{1-x}$Mn$_x$As. This model has already been shown to reproduce accurately the Curie temperatures for Ga$_{1-x}$Mn$_x$As. Here we show that the calculated spin stiffness are in excellent agreement with those which were obtained from ab-initio based studies. In addition, an overall good agreement is also found with available experimental data. We have also evaluated the magnon density of states and the typical density of states from which the "mobility edge", separating the extended from localized magnon states, was determined. The power of the model lies in its ability to be generalized for a broad class of diluted magnetic semiconductor materials, thus it bridges the gap between first principle calculations and model based studies.Comment: 5 pages, 5 figures, Text and some figures revised to match the accepted versio

Monte Carlo approach to nonperturbative strings -- demonstration in noncritical string theory

We show how Monte Carlo approach can be used to study the double scaling limit in matrix models. As an example, we study a solvable hermitian one-matrix model with the double-well potential, which has been identified recently as a dual description of noncritical string theory with worldsheet supersymmetry. This identification utilizes the nonperturbatively stable vacuum unlike its bosonic counterparts, and therefore it provides a complete constructive formulation of string theory. Our data with the matrix size ranging from 8 to 512 show a clear scaling behavior, which enables us to extract the double scaling limit accurately. The ``specific heat'' obtained in this way agrees nicely with the known result obtained by solving the Painleve-II equation with appropriate boundary conditions.Comment: 15 pages, 10 figures, LaTeX, JHEP3.cls; references added, typos correcte

Both Reintroduction and Recolonization Likely Contributed to the Re-establishment of a Fisher Population in East-central Alberta

Recently, Stewart et al. (2017) investigated the origins of contemporary fisher populations in the Cooking Lake Moraine (CLM) of east-central Alberta, Canada, where fishers (Pekania pennanti) from Ontario and Manitoba, Canada were reintroduced in the early 1990s. To address this objective, Stewart et al. (2017) compared microsatellite alleles from extant fisher populations in the CLM to those from Ontario, Manitoba, and other Alberta populations. They reported that the CLM population clustered with adjacent native Alberta populations, consistent with recolonization, but also that 2 of 109 microsatellite alleles in the CLM occurred only in the source populations from Ontario and Manitoba. Rather than allowing for the possibility that these alleles descended from reintroduced fishers, the authors speculated that they represented random mutations among fishers that recolonized the area naturally from nearby populations in Alberta, and concluded that the reintroduction had failed completely. We disagree with this conclusion for 2 reasons. We contend it is more likely that the 2 alleles represent a genetic signature from the individuals released during the reintroduction, rather than being the result of mutations. We further suggest that, irrespective of the genetic legacy of introduced fishers in the recovered population, the presence of reintroduced fishers in the CLM may have helped facilitate natural recolonization of the area by fishers from surrounding areas. In our view, Stewart et al.’s (2017) findings do not demonstrate conclusively that the reintroduction program failed; on the contrary, we argue that their findings indicate that reintroduced fishers likely contributed to the long-term persistence of fishers in the CLM. The uncertainty surrounding this case underscores the importance of genetic monitoring following reintroductions.https://digitalcommons.snc.edu/faculty_staff_works/1032/thumbnail.jp