Calculating the energy spectra of magnetic molecules: application of real- and spin-space symmetries

The determination of the energy spectra of small spin systems as for instance given by magnetic molecules is a demanding numerical problem. In this work we review numerical approaches to diagonalize the Heisenberg Hamiltonian that employ symmetries; in particular we focus on the spin-rotational symmetry SU(2) in combination with point-group symmetries. With these methods one is able to block-diagonalize the Hamiltonian and thus to treat spin systems of unprecedented size. In addition it provides a spectroscopic labeling by irreducible representations that is helpful when interpreting transitions induced by Electron Paramagnetic Resonance (EPR), Nuclear Magnetic Resonance (NMR) or Inelastic Neutron Scattering (INS). It is our aim to provide the reader with detailed knowledge on how to set up such a diagonalization scheme.Comment: 29 pages, many figure

One-year intensive characterization on PM2.5 nearby port area of Thessaloniki, Greece

The chemical characterization of particulate matter (PM) 2.5 fraction was studied during a 1-year sampling campaign conducted at a site near Thessaloniki’s port area. PM2.5 collected samples were chemically analyzed for polycyclic aromatic hydrocarbons, minerals, and trace elements (Pb, Ni, Cu, V, Mn, Cr, Zn, Mg, K, Ti, Fe, Ca, and Al); water-soluble ions (Cl−, NO3−, SO42−, K+, Na+, NH4+, Mg2+, Ca2+); and organic and elemental carbon. The average annual PM2.5 concentration (66.0 μg/m3) was at the highest level compared with other studies reported for the same city but different sampling sites. The average daily sum of the measured concentration of polycyclic aromatic hydrocarbons (PAHs) was 12.76 ng/m3; this value decreased to 6.73 ng/m3 for the warm period and reached the value of 19.8 ng/m3 for the cold period. The average concentration of benzo[a]pyrene during the sampling period was 0.75 ng/m3, which is below the European Union limit value of 1.0 ng/m3. The ionic content comprised, on average, 22.6 % of the PM2.5 mass, with sulfate and ammonium being the most abundant species (31 and 26 %, respectively, of measured ions during the whole sampling period). The annual mean concentrations of organic carbon (OC) and elemental carbon (EC) were 10.5 ± 6.3 and 2.3 ± 1.5 μg/m3, respectively. The OC/EC ratio ranged from 1.6 to 9.9, suggesting that there is a significant influence of residential wood burning for heating as well as ship and vehicle emissions to the sampling area. Finally, the elemental composition of associated PM2.5 was dominated by Ca, Fe, and Al. Although conclusions based only on PM2.5 measurements cannot entirely estimate all harbor sources’ contribution, there is evidence to support that port activities affect the city’s air quality and vice versa

Dinuclear copper (II) phosphonates containing chelating nitrogen ligands: synthesis, structure, magnetism and nuclease activity

The reaction of Cu(ClO4)2·6H2O with RPO3H2 (R = cyclopentyl, isopropyl, trichloromethyl) in the presence of chelating nitrogen ligands bpya or bpy afforded dinuclear copper phosphonates [Cu2(μ 2-C5H9PO3)2(bpya)2(H2O)2] (H2O)4 (1), [Cu2(μ 2-C3H7PO3)2(bpya)2(H2O)2] (H2O)2 (2) and [Cu2(μ 2-CCl3PO3)2(bpy)2(MeOH)2] (H2O) (3) [bpya = 2,2'-bipyridylamine, bpy = 2,2'-bipyridine]. The molecular structures of these complexes reveal that they are isostructural and possess two copper centres that are bridged to each other by two isobidentate phosphonate ligands generating an eight-membered Cu2O4P2 ring. Magnetic studies on 2 reveal antiferromagnetic behaviour at low temperatures. Dinuclear complexes 1-3 were found to be excellent nucleases and can convert supercoiled pBR322 DNA form I into nick form II in only 30 min without the need for any external oxidant through a hydrolytic pathway

Microstuctural analysis and determination of PM10 emission sources in an industrial Mediterranean city

International audienceScientists are interested in knowing more about the control of sources which contribute to environmental pollution. Air pollution has two main sources: anthropogenic and natural sources. The natural contributions to environmental pollution can be assessed, but cannot be totally controlled. while the emissions from the anthropogenic sources can be controlled. These air pollutants can be dispersed and transferred by winds in the atmosphere. The focus area of this study is the Mediterranean basin. The most important winds in this area are the land and sea breezes. Scanning Electron Microscopy (SEM) was applied to characterize the morphology of the PM10 samples in order to identify possible emission sources for the occuring pollution. Energy Dispersive X-ray Spectroscopy (EDS) was performed for the elemental analysis and chemical characterization of the PM10 samples. The analysis showed that the PM10 samples can be divided into three different groups: the samples containing mineral phases, the compounds from combustion processes and the particles emitted from high-temperature processes