Symmetric and antisymmetric exchange anisotropies in quasi-one-dimensional CuSe2_2O5_5 as revealed by ESR

We present an electron spin resonance (ESR) study of single-crystalline spin chain-system CuSe$_2$O$_5$ in the frequency range between 9 GHz and 450 GHz. In a wide temperature range above the N\'{e}el temperature $T_N=17$ K we observe strong and anisotropic frequency dependence of a resonance linewidth. Although sizeable interchain interaction $J_{IC}\approx 0.1 J$ ($J$ is the intrachain interaction) is present in this system, the ESR results agree well with the Oshikawa-Affleck theory for one-dimensional $S=1/2$ Heisenberg antiferromagnet. This theory is used to extract the anisotropies present in CuSe$_2$O$_5$. We find that the symmetric anisotropic exchange $J_c=(0.04 \pm 0.01) \:J$ and the antisymmetric Dzyaloshinskii-Moriya (DM) interaction $D=(0.05\pm 0.01)\:J$ are very similar in size in this system. Staggered-field susceptibility induced by the presence of the DM interaction is witnessed in the macroscopic susceptibility anisotropy.Comment: 8 pages, 7 figures, 2 tables, published in Phys. Rev.

Ionospheric Calibration of Low Frequency Radio Interferometric Observations using the Peeling Scheme: I. Method Description and First Results

Calibration of radio interferometric observations becomes increasingly difficult towards lower frequencies. Below ~300 MHz, spatially variant refractions and propagation delays of radio waves traveling through the ionosphere cause phase rotations that can vary significantly with time, viewing direction and antenna location. In this article we present a description and first results of SPAM (Source Peeling and Atmospheric Modeling), a new calibration method that attempts to iteratively solve and correct for ionospheric phase errors. To model the ionosphere, we construct a time-variant, 2-dimensional phase screen at fixed height above the Earth's surface. Spatial variations are described by a truncated set of discrete Karhunen-Loeve base functions, optimized for an assumed power-law spectral density of free electrons density fluctuations, and a given configuration of calibrator sources and antenna locations. The model is constrained using antenna-based gain phases from individual self-calibrations on the available bright sources in the field-of-view. Application of SPAM on three test cases, a simulated visibility data set and two selected 74 MHz VLA data sets, yields significant improvements in image background noise (5-75 percent reduction) and source peak fluxes (up to 25 percent increase) as compared to the existing self-calibration and field-based calibration methods, which indicates a significant improvement in ionospheric phase calibration accuracy.Comment: 23 pages, 14 figures, 2 tables. Accepted for publication in A&A. Changes in v2: Corrected minor error in Equations A.3 and A.12. Extended acknowledgment

Imatinib mesylate (STI571) is a substrate for the breast cancer resistance protein (BCRP)/ABCG2 drug pump

Imatinib mesylate (STI571), a potent tyrosine kinase inhibitor, is successfully used in the treatment of chronic myelogenous leukemia and gastrointestinal stromal tumors. However, the intended chronic oral administration of imatinib may lead to development of cellular resistance and subsequent treatment failure. Indeed, several molecular mechanisms leading to imatinib resistance have already been reported, including overexpression of the MDR1/ABCB1 drug pump. We examined whether imatinib is a substrate for the breast cancer resistance protein (BCRP)/ABCG2 drug pump that is frequently overexpressed in human tumors. Using a panel of well-defined BCRP-overexpressing cell lines, we provide the first evidence that imatinib is a substrate for BCRP, that it competes with mitoxantrone for drug export, and that BCRP-mediated efflux can be reversed by the fumitremorgin C analog Ko-143. Since BCRP is highly expressed in the gastrointestinal tract, BCRP might not only play a role in cellular resistance of tumor cells but also influence the gastrointestinal absorption of imatinib

Consolation through music: A survey study

Even though music is widely used as a source of solace, the question as to how and why music offers consolation remains largely unexplored. The aims of the present study are as follows: (a) to compare listening to music versus other self-soothing behaviors, (b) to explore when music is used as a means for solace, (c) to identify aspects of music that are important for providing solace, and (d) to explore behavior while listening to consoling music. Participants completed an internet survey distributed through the websites of Dutch National Radio 2 and Radio 4 (N = 445). The survey consisted of the Geneva Emotion and Music Scale (GEMS), the solace-scale from the Music in Mood Regulation questionnaire (MMR), questions concerning means of solace, situations requiring comfort, song aspects, and feelings and activities during music listening. The main findings indicate that: (1) music is the most important source of consolation compared with other soothing behaviors, (2) situations in which people have experienced loss and sadness are the primary situations in which music offers solace, (3) consoling music induces a feeling of being moved and a mixture of both positive and sad emotions; the most important aspects of a song for soothing purposes are the music itself and the lyrics, and (4) music for comfort is listened to predominately in solitude, as the sole activity. On the basis of these findings, a characterization of listening to consoling music is compiled. Behavior and song aspects are discussed in terms of how and why they are helpful in providing solace

On the Role of Penning Ionization in Photoassociation Spectroscopy

We study the role of Penning ionization on the photoassociation spectra of He(^3S)-He(^3S). The experimental setup is discussed and experimental results for different intensities of the probe laser are shown. For modelling the experimental results we consider coupled-channel calculations of the crossing of the ground state with the excited state at the Condon point. The coupled-channel calculations are first applied to model systems, where we consider two coupled channels without ionization, two coupled channels with ionization, and three coupled channels, for which only one of the excited states is ionizing. Finally, coupled-channel calculations are applied to photoassociation of He(^3S)-He(^3S) and good agreement is obtained between the model and the experimental results.Comment: 14 pages, 18 figures, submitted to the special issue on Cold Molecules of J. Phys.

High-frequency electron paramagnetic resonance of Tm3+ ions in lanthanum and thulium ethylsulphate single crystals

We have observed electron paramagnetic resonance and far-infrared absorption of the transitions between the singlet ground state and the first excited doublet of the Van Vleck paramagnetic Tm3+ ion in ethylsulphate crystals in fields up to 10.5 T. The interaction of the Stark levels with a phonon state is clearly shown. The EPR of Tm3+ in the 1000-1600 GHz range are single Lorentzians in lanthanum ethylsulphate but are asymmetric and richly structured in thulium ethylsulphate. This work illustrates the usefulness of high-frequency EPR in the study of Van Vleck paramagnets, which are inaccessible by EPR at conventional frequencies