Travel and tourism: Into a complex network

It is discussed how the worldwide tourist arrivals, about 10% of the world’s domestic product, form a largely heterogeneous and directed complex network. Remarkably the random network of connectivity is converted into a scale-free network of intensities. The importance of weights on network connections is brought into discussion. It is also shown how strategic positioning particularly benefits from market diversity and that interactions among countries prevail on a technological and economic pattern, questioning the backbone of driving forces in traveling.     

Knight shifts and relaxation in gadolinium above the curie temperature

We have studied the transverse μSR signal in Gd metal in the temperature region 1–2 T_C, and it is demonstrated that measurements in the paramagnetic range can be used to obtain the hyperfine field at the muon site, as well as to give information on the fluctuations of the Gd spins. The critical exponent for slowing down of Gd spin fluctuations is 0.56(5) above 1.05 T_C but decreases to 0.15(5) below 1.05 T_C. Comparisons with results from PAC and Mössbauer measurements are discussed.     

Berechnung des Wirkungsquerschnitts der direkten Paarerzeugung bei Streuung von 5,511 MeV- und 32 MeV-Elektronen an einem statischen Coulombfeld

Differential cross sections for direct pair production by electrons with total energiesE ₀=5.511 and 32 MeV in copper are calculated in lowest order of pertubation theory and Born approximation, including the matrix elements of the electron exchange effect. Integration over particle angles and — in the case ofE ₀=32 MeV — over the energy of one outgoing electron was performed numerically on an IBM 7044 computer by using Gaussian quadrature formulas in FORTRAN-programs. The results forE ₀=5.511 MeV show a severe reduction of the differential cross section due to the exchange effect, while the results for 32 MeV are in fairly good agreement with the pair production experiment performed byCriegee in 1959.     

Mössbauer effect study of the pseudo-binary system (Ti1−x Nb x )Fe2

Mössbauer spectroscopy and X-ray diffraction measurements have been done on (Ti_1–x Nb _x )Fe₂ compounds in order to investigate the effect of Nb on the magnetic properties of TiFe₂. The experimental results show that Nb enters the lattice by filling Ti sites, thereby forming a continuous phase over the whole range of Nb concentrations. The Mössbauer spectra at 80 K fitted with a magnetic hyperfine field distribution show a continuous decrease of the average magnetic hyperfine field with increasing Nb concentration, as well as several different magnetic configurations forx0.3.     

Validation of three rapid screening methods for detection of verotoxin-producing Escherichia coli in foods: interlaboratory study

An interlaboratory study was conducted for the validation of 3 methods for the detection of all verotoxin-producing Escherichia coli (VTEC) in foods. The methods were a multi-analyte 1-step lateral flow immunoassay (LFIA) for detection of E. coli O157 and verotoxin (VT); an enzyme-linked immunosorbent assay targeted against VT1, VT2, and VT2c (VT-ELISA); and a polymerase chain reaction (PCR) method for detection of VT genes (VT-PCR). Aliquots (25 g or 25 mL) of 4 food types (raw minced [ground] beef, unpasteurized milk, unpasteurized apple juice [cider], and salami) were individually inoculated with low numbers (<9 to 375 cells/25 g) of 6 test strains of E. coli (serogroups O26, O103, O111, O145, and O157) with differing VT-producing capabilities. Five replicates for each test strain and 5 uninoculated samples were prepared for each food type. Fourteen participating laboratories analyzed samples using the LFIA, 9 analyzed the samples by ELISA, and 9 by PCR. The LFIA for O157 and VT had a specificity (correct identification of negative samples) of 92 and 94%, respectively, and a sensitivity (correct identification of positive samples) of 94 and 55%, respectively. The VT-ELISA and VT-PCR had a specificity of 98 and 99%, respectively, and a sensitivity of 89 and 72%, respectively.     

Pleistocene age paleo-groundwater inferred from water-stable isotope values in the central part of the Baltic Artesian Basin

A new data set of δ²H and δ¹⁸O in the groundwater from the central part of the Baltic Artesian Basin is presented. The hydrogeological section is subdivided into stagnation, slow exchange and active exchange zones. Na–Ca–Cl brine found at the deepest part – the stagnation zone – is characterized by δ¹⁸O values above ?5?‰ and δ²H values approaching ?40?‰ with respect to Vienna Standard Mean Ocean Water. The slow exchange zone where waters of mostly intermediate salinity reside is characterized by δ¹⁸O values around ?11.7?‰ and δ²H values around ?85.3?‰. Mean δ¹⁸O and δ²H values of the fresh groundwater in the active water exchange zone are ?11.1 and ?79.9?‰, respectively. Characteristically, the groundwater in the active and slow exchange zone is isotopically more depleted compared with the precipitation values observed, and the depletion increases with depth down to the level where strongly enriched brines are encountered.