Magnetic properties of the low-dimensional spin-1/2 magnet \alpha-Cu_2As_2O_7

In this work we study the interplay between the crystal structure and magnetism of the pyroarsenate \alpha-Cu_2As_2O_7 by means of magnetization, heat capacity, electron spin resonance and nuclear magnetic resonance measurements as well as density functional theory (DFT) calculations and quantum Monte Carlo (QMC) simulations. The data reveal that the magnetic Cu-O chains in the crystal structure represent a realization of a quasi-one dimensional (1D) coupled alternating spin-1/2 Heisenberg chain model with relevant pathways through non-magnetic AsO_4 tetrahedra. Owing to residual 3D interactions antiferromagnetic long range ordering at T_N\simeq10K takes place. Application of external magnetic field B along the magnetically easy axis induces the transition to a spin-flop phase at B_{SF}~1.7T (2K). The experimental data suggest that substantial quantum spin fluctuations take place at low magnetic fields in the ordered state. DFT calculations confirm the quasi-one-dimensional nature of the spin lattice, with the leading coupling J_1 within the structural dimers. QMC fits to the magnetic susceptibility evaluate J_1=164K, the weaker intrachain coupling J'_1/J_1 = 0.55, and the effective interchain coupling J_{ic1}/J_1 = 0.20.Comment: Accepted for publication in Physical Review

Multi-interaction mean-field renormalization group

We present an extension of the previously proposed mean-field renormalization method to model Hamiltonians which are characterized by more than just one type of interaction. The method rests on scaling assumptions about the magnetization of different sublattices of the given lattice and it generates as many flow equations as coupling constants without arbitrary truncations on the renormalized Hamiltonian. We obtain good results for the test case of Ising systems with an additional second-neighbor coupling in two and three dimensions. An application of the method is also done to a morphological model of interacting surfaces introduced recenlty by Likos, Mecke and Wagner [J. Chem. Phys. {\bf{102}}, 9350 (1995)]. PACS: 64.60.Ak, 64.60.Fr, 05.70.JkComment: Tex file and three macros appended at the end. Five figures available upon request to: [email protected], Fax: [+]39-40-224-60

Phase I clinical and pharmacokinetic study of the oral platinum analogue JM216 given daily for 14 days

Background: The oral bis (acetate) ammine dichloro cyclo-hexylamine platinum (IV) analogue (BMS-182751) was brought into clinical development because it was shown to be cytotoxic against some human tumour cell lines and to have an antitu-mor activity in murine tumours at least comparable to that of parenteral cisplatin and carboplatin. In early clinical studies in which the optimal schedule of treatment was daily for five consecutive days, dose-dependent nausea and vomiting occurred in about two-thirds of patients. Patients and methods: To evaluate if the use of lower daily doses for longer periods of time could result in a better toler-ability, JM216 was given once daily for 14 consecutive days every four to five weeks to adult patients with solid tumors. Oral antiemetics were given prophylactically only at the highest doses. The pharmacokinetics of total and ultrafiltrable platinum were studied on days 1 and 14 of the first cycle by Inductively Coupled-Mass-Spectrometry (ICP-MS). Results: Forty-six patients were treated at doses ranging from 10 mg/m2/d to 50 mg/m2/d and 39 were evaluable for hematologic toxicity over 74 cycles. MTDs were reached at 45 mg/m2/d and 50 mg/m2/d × 14 repeated every five weeks in patients with extensive, or limited/no prior treatment, respectively. The dose-limiting toxicity was neutropenia which was delayed and variable among patients. Other non-hematological toxicities were severe vomiting (22% of cycles), diarrhea (28% of cycles) and drug-associated fever (32% of patients), controlled with paracetamol. Subjective improvement with disappearance of tumour-related pain was observed in one patient with chemotherapy-resistant metastatic prostate cancer and in one previously untreated patient with malignant mesothelioma. Cmax and AUC values of both total and ultrafiltrable platinum on days 1 and 14 were highly variable among patients. Only Cmax on day 1 was linearly related to the dose. Total and ultrafiltrable platinum were still detectable two weeks after the last dose. No relationship could be established between AUC values and toxicities. Conclusions: Daily doses of JM216 of 40 mg/m2 and 45 mg/m2 for 14 consecutive days every five weeks with oral antiemetic prophylaxis are selected for phase II evaluation of single agent in patients with extensive or limited/no prior treatment, respectively. The administration of JM216 on a day × 14 schedule produced nausea and vomiting comparable to that observed with the day × 5 regimen but of longer duration. The variability of pharmacokinetics and pharmacodynamics, even though limited at the doses proposed for phase II evaluation of JM216 as single agent, recommend a careful monitoring of the patient

Lymphatic Filariasis Control in Tanzania: Effect of Six Rounds of Mass Drug Administration with Ivermectin and Albendazole on Infection and Transmission.

Control of lymphatic filariasis (LF) in most countries of sub-Saharan Africa is based on annual mass drug administration (MDA) with a combination of ivermectin and albendazole, in order to interrupt transmission. We present findings from a detailed study on the effect of six rounds of MDA with this drug combination as implemented by the National Lymphatic Filariasis Elimination Programme (NLFEP) in a highly endemic rural area of north-eastern Tanzania.\ud The effect of treatment on transmission and human infection was monitored in a community- and a school-based study during an 8-year period (one pre-intervention and 7 post-intervention years) from 2003 to 2011. Before intervention, 24.5% of the community population had microfilariae (mf) in the blood, 53.3% had circulating filarial antigens (CFA) and 78.9% had specific antibodies to the recombinant filarial antigen Bm14. One year after the sixth MDA, these values had decreased considerably to 2.7%, 19.6% and 27.5%, respectively. During the same period, the CFA prevalence among new intakes of Standard 1 pupils in 10 primary schools decreased from 25.2% to 5.6%. In line with this, transmission by the three vectors (Anopheles gambiae, An. funestus and Culex quinquefasciatus) as determined by dissection declined sharply (overall vector infectivity rate by 99.3% and mean monthly transmission potential by 99.2% between pre-intervention and fifth post-intervention period). A major shift in vector species composition, from predominantly anopheline to almost exclusively culicine was observed over the years. This may be largely unrelated to the MDAs but may have important implications for the epidemiology of LF in the area. Six MDAs caused considerable decrease in all the measured indices for transmission and human infection. In spite of this, indices were still relatively high in the late period of the study, and it may take a long time to reach the recommended cut-off levels for interruption of transmission unless extra efforts are made. These should include increased engagement of the target population in the control activities, to ensure higher treatment coverage. It is expected that the recent initiative to distribute insecticide impregnated bed nets to every household in the area will also contribute towards reaching the goal of successful LF elimination

Deep ALTAIR + NIRI Imaging of the Disk and Bulge of M31

Deep J, H, and K' images, recorded with the ALTAIR adaptive optics system and NIRI imager on Gemini North, are used to probe the stellar content of the disk and bulge of the Local Group galaxy M31. With FWHM near 0.08 arcsec in K, these are the highest angular resolution near-infrared images yet obtained of this galaxy. Four fields that sample M31 at galactocentric radii of 62, 9, 4, and 2 arcmin were observed. The RGB-tip occurs between K = 17.0 and 17.2, and the color of the RGB in the field closest to the center of M31 is consistent with that of NGC 6528. After accounting for random photometric errors, the upper RGB in each field has a width on the (K, J-K) CMD that is consistent with a +/- 0.5 dex dispersion in [Fe/H], in rough agreement with what is seen in other disk and spheroid fields in M31. A population of very bright red stars, which we identify as C stars, are seen in the three fields that are closest to the center of M31. The spatial distribution of these objects suggests that they are well mixed throughout this part of M31, and so likely did not form in a compact region near the galactic nucleus, but more probably formed in the inner disk. We speculate that these C stars may be the most luminous members of the intermediate age population that has been detected previously in studies of the integrated spectrum of the central regions of M31.Comment: 36 pages of text + 16 eps figures; Astronomical Journal in pres

Tracing the evolution of nearby early-type galaxies in low density environments. The Ultraviolet view from GALEX

We detected recent star formation in nearby early-type galaxies located in low density environments, with GALEX Ultraviolet (UV) imaging. Signatures of star formation may be present in the nucleus and in outer rings/arm like structures. Our study suggests that such star formation may be induced by different triggering mechanisms, such as the inner secular evolution driven by bars, and minor accretion phenomena. We investigate the nature of the (FUV-NUV) color vs. Mg2 correlation, and suggest that it relates to "downsizing" in galaxy formation.Comment: Conference "UV Universe 2010" S. Petersburg 31 May - 3 June, 2010 Accepted for publication in Astrophysics & Space Science . The final publication is available at http://www.springerlink.co

Looking backward: From Euler to Riemann

We survey the main ideas in the early history of the subjects on which Riemann worked and that led to some of his most important discoveries. The subjects discussed include the theory of functions of a complex variable, elliptic and Abelian integrals, the hypergeometric series, the zeta function, topology, differential geometry, integration, and the notion of space. We shall see that among Riemann's predecessors in all these fields, one name occupies a prominent place, this is Leonhard Euler. The final version of this paper will appear in the book \emph{From Riemann to differential geometry and relativity} (L. Ji, A. Papadopoulos and S. Yamada, ed.) Berlin: Springer, 2017

On the geometry of C^3/D_27 and del Pezzo surfaces

We clarify some aspects of the geometry of a resolution of the orbifold X = C3/D_27, the noncompact complex manifold underlying the brane quiver standard model recently proposed by Verlinde and Wijnholt. We explicitly realize a map between X and the total space of the canonical bundle over a degree 1 quasi del Pezzo surface, thus defining a desingularization of X. Our analysis relys essentially on the relationship existing between the normalizer group of D_27 and the Hessian group and on the study of the behaviour of the Hesse pencil of plane cubic curves under the quotient.Comment: 23 pages, 5 figures, 2 tables. JHEP style. Added references. Corrected typos. Revised introduction, results unchanged

Persistence of Gamma-H2AX Foci in Irradiated Bronchial Cells Correlates with Susceptibility to Radiation Associated Lung Cancer in Mice

The risk of developing radiation-induced lung cancer differs between different strains of mice, but the underlying cause of the strain differences is unknown. Strains of mice also differ in their ability to efficiently repair DNA double strand breaks resulting from radiation exposure. We phenotyped mouse strains from the CcS/Dem recombinant congenic strain set for their efficacy in repairing DNA double strand breaks during protracted radiation exposures. We monitored persistent gamma-H2AX radiation induced foci (RIF) 24 hours after exposure to chronic gamma-rays as a surrogate marker for repair deficiency in bronchial epithelial cells for 17 of the CcS/Dem strains and the BALB/cHeN founder strain. We observed a very strong correlation R2 = 79.18%, P < 0.001) between the level of persistent RIF and radiogenic lung cancer percent incidence measured in the same strains. Interestingly, spontaneous levels of foci in non-irradiated strains also showed good correlation with lung cancer incidence (R2=32.74%, P =0.013). These results suggest that genetic differences in DNA repair capacity largely account for differing susceptibilities to radiation-induced lung cancer among CcS/Dem mouse strains and that high levels of spontaneous DNA damage is also a relatively good marker of cancer predisposition. In a smaller pilot study, we found that the repair capacity measured in peripheral blood leucocytes also correlated well with radiogenic lung cancer susceptibility, raising the possibility that such phenotyping assay could be used to detect radiogenic lung cancer susceptibility in humans