Magnetic excitations in the spin-1 anisotropic antiferromagnet NiCl2−4SC(NH2)2NiCl_2-4SC(NH_2)_2

The spin-1 anisotropic antiferromagnet NiCl_2-4SC(NH2)_2 exhibits a field-induced quantum phase transition that is formally analogous to Bose-Einstein condensation. Here we present results of systematic high-field electron spin resonance (ESR) experimental and theoretical studies of this compound with a special emphasis on single-ion two-magnon bound states. In order to clarify some remaining discrepancies between theory and experiment, the frequency-field dependence of magnetic excitations in this material is reanalyzed. In particular, a more comprehensive interpretation of the experimental signature of single-ion two-magnon bound states is shown to be fully consistent with theoretical results. We also clarify the structure of the ESR spectrum in the so-called intermediate phase.Comment: 9 pages, 10 figure

Efimov effect in quantum magnets

Physics is said to be universal when it emerges regardless of the underlying microscopic details. A prominent example is the Efimov effect, which predicts the emergence of an infinite tower of three-body bound states obeying discrete scale invariance when the particles interact resonantly. Because of its universality and peculiarity, the Efimov effect has been the subject of extensive research in chemical, atomic, nuclear and particle physics for decades. Here we employ an anisotropic Heisenberg model to show that collective excitations in quantum magnets (magnons) also exhibit the Efimov effect. We locate anisotropy-induced two-magnon resonances, compute binding energies of three magnons and find that they fit into the universal scaling law. We propose several approaches to experimentally realize the Efimov effect in quantum magnets, where the emergent Efimov states of magnons can be observed with commonly used spectroscopic measurements. Our study thus opens up new avenues for universal few-body physics in condensed matter systems.Comment: 7 pages, 5 figures; published versio

In vitro biocompatibility between mitomycin-C (MMC) and bacillus Calmette-Guerin (BCG)

Background: Mitomycin-C (MMC) and bacillus Calmette-Guerin (BCG) intravesical instillations are widely and effectively used as adjuvant treatment for superficial bladder cancer. In an attempt to improve the efficacy of intravesical therapy, MMC and BCG have also been used in a sequential or an alternating mode. The aim of this study was to assess the in vitro biocompatibility between these agents. Materials and Methods: The effect of MMC on BCG clumping tendency was assessed by estimating the number of colony forming units (CFU) of BCG in suspension, during incubation at 37 degrees C for 3 h, with repeated recordings of the suspension optical density (OD). Preparations containing either BCG plus MMC or BCG plus an equivalent amount of sterile water were cultivated using the non-radiometric system BACTEC MGIT 960. The final concentrations of the agents, following transfer of the preparations into the tubes of the system, were 1.25 mg/ml for BCG and 1 mg/ml for MMC. During the cultivation process, the tubes of the system were automatically checked every 60 min for fluorescence emission, which is an indication of mycobacteria growth. A comparative cultivation of the same preparations on Lowenstein-Jensen solid medium was also performed. Results: The OD of the BCG preparation remained almost unaffected for 3 h and was minimally altered by inclusion of MMC. After 34-38 h of cultivation in the BACTEC MGIT 960 system, all 7 cultures of the BCG+sterile water preparations became positive. In contrast, no BCG+MMC specimen became positive after an incubation period of 42 days. Following re-cultivation of the 7 negative BCG+MMC specimens, 6 remained negative, whereas 1 specimen became positive after an incubation period of 22 days. On Lowenstein-Jensen medium, growth of mycobacteria was noted only in the BCG+sterile water specimens and not in the BCG+MMC specimens. Conclusion: The results of this study indicate that, although MMC has no apparent effect on BCG tendency to form clumps in suspension, it may inhibit its growth in vitro. However, this does not necessarily compromise BCG anti-tumour activity. As the in vivo interaction of the drugs may be different, the efficacy of the combined BCG+MMC treatment should be defined in clinical trials

Risk factors for tracheobronchial acquisition of resistant gram-negative bacterial pathogens in mechanically ventilated ICU patients

The aim of this study was to identify risk factors for tracheobronchial acquisition with the most commonresistant Gram-negative bacteria in the intensive care unit (ICU) during the first week after intubation and mechanical ventilation. Tracheobronchial and oropharyngeal cultures were obtained at admission, after 48 hours, and after 7 days of mechanical ventilation. Patient characteristics, interventions, and antibiotic usage were recorded. Among 71 eligible patients with two negative bronchial cultures for resistant Gramnegative bacteria (at admission and within 48 hours), 41 (58%) acquired bronchial resistant Gram-negative bacteria by day 7. Acquisition strongly correlated with presence of the same pathogens in the oropharynx: Acinetobacter baumannii [odds ratio (OR)520.2, 95% confidence interval (CI): 5.5–73.6], Klebsiella pneumoniae (OR58.0, 95% CI: 1.9–33.6), and Pseudomonas aeruginosa (OR527, 95%: CI 2.7–273). Bronchial acquisition with resistant K. pneumoniae also was associated with chronic liver disease (OR53.9, 95% CI: 1.0–15.3), treatment with aminoglycosides (OR54.9, 95% CI: 1.4–18.2), tigecycline (OR54.9, 95% CI: 1.4–18.2), and linezolid (OR53.9, 95% CI: 1.1–15.0). In multivariate analysis, treatment with tigecycline and chronic liver disease were independently associated with bronchial resistant K. pneumoniae acquisition. Our results show a high incidence of tracheobronchial acquisition with resistant Gramnegative microorganisms in the bronchial tree of newly intubated patients. Oropharynx colonization with the same pathogens and specific antibiotics use were independent risk factors. © 2015 Edizioni Scientifiche per l’Informazione su Farmaci e Terapia