Nephropathia epidemica and Puumala virus occurrence in relation to bank vole (Clethrionomys glareolus) dynamics and environmental factors in northern Sweden

The objectives of the thesis were to investigate the spatio-temporal patterns of nephropathia epidemica (NE) in humans and Puumala virus (PUU) occurrence in relation to bank vole (Clethrionomys glareolus) dynamics and environmental factors in a region of high incidence of NE in northern Sweden. Nephropathia epidemica is a mild form of hemorrhagic fever with renal syndrome, and in northern Sweden the most prevailing serious febrile viral infection, second to influenza. All serologically confirmed NE cases during 1991-2001 in the four northernmost counties (n = 2,468) were used to establish spatio-temporal patterns of the occurrence of the human disease. Within the study region, the bank voles show marked population fluctuations with 3-4 yr cycles and the incidence of NE has a temporal component strongly correlated to annual numbers of bank voles in autumn. People living in rural dwellings near coastal areas were abundant among notified cases and middle-aged males were over-represented. The patients were often infected in autumn when engaged in activities such as handling of fire wood, gardening or hay-handling near man-made rodent refugia or cleaning/redecorating within one. A proportion of these patients, confident about site of PUU exposure, were used to establish field sites in two separate studies. Firstly a five year study (1995-1999) at six sites spanning a bank vole population cycle, and secondly a spatially extensive study at 32 sites was conducted in autumn 1998. Densities, fluctuations and demography of vole populations differ between sites of known occurrence of NE were compared to random forest sites. Five years of repeated biannual sampling revealed that case sites harbored more bank voles than random forest sites, in particular during population peaks. For the individual bank voles, the probability of PUU infection was significantly higher in population peak year, increased with age and was higher for males than for females. In the spatially extended study, it was found that in particular environmental characteristics associated with old-growth moist forests (i.e. Alectoria spp., Picea abies, fallen wood and Vaccinium myrtillus) were associated with high bank vole numbers and numbers of PUU infected bank voles. This implies that success in circulation and persistence of PUU within local bank vole populations is strongly influenced by the local environments. In future modeling of PUU transmission, influence of bank vole demography and environmental factors should be useful on establishing risk assessments and identifying areas of particular risk of PUU exposure

DNA extraction from formalin-fixed Franciscana tissues

The present paper reports the extraction of DNA from formalin-fixed Pontoporia blainvillei tissues. Following the Vachot and Monerot (1996) protocol, fragmented DNA (300-700bp) was extracted from more than 95% of liver and muscle samples. DNA yield in liver samples was significantly higher than in muscle samples (4.574 ± 1.169mg DNA/mg versus 0.808 ± 0.297mg DNA/mg). Similar results were obtained from nine other species of cetaceans and five species of pinnipeds. It is of special interest to have a method that allows the utilisation of museum specimens not originally preserved for genetic studies, which may include rarely available, declining or extinct species. SPANISH: El presente trabajo reporta la extracción de ADN a partir de tejidos formolizados de Pontoporia blainvillei. Siguiendo el protocolo de Vachot y Monerot (1996) se pudo extraer ADN degradado (300-700pb) en más del 95% de las muestras de hígado y músculo analizadas. El rendimiento en ADN fue significativamente mayor en muestras de hígado que en muestras de músculo (4.574 ± 1.169mg DNA/mg tejido húmedo versus 0.808 ± 0.297mg DNA/mg tejido húmedo). Resultados similares se obtuvieron en otras nueve especies de Cetáceos y cinco de Pinnípedos. Resulta de gran interés contar con un método que permita la utilización de especímenes depositados en museos y que no hayan sido originalmente colectados para estudios genéticos, incluyendo especies de difícil obtención, en franca declinación o extintas

Star-formation in the central kpc of the starburst/LINER galaxy NGC1614

A high angular resolution, multi-wavelength study of the LINER galaxy NGC1614 has been carried out. OVRO CO 1-0 observations are presented together with extensive multi-frequency radio continuum and HI absorption observations with the VLA and MERLIN. Toward the center of NGC1614, we have detected a ring of radio continuum emission with a radius of 300 pc. This ring is coincident with previous radio and Paschen-alpha observations. The dynamical mass of the ring based on HI absorption is 3.1 x 10E9 Msun. The peak of the integrated CO 1-0 emission is shifted by 1" to the north-west of the ring center and a significant fraction of the CO emission is associated with a crossing dust lane. An upper limit to the molecular gas mass in the ring region is 1.7 x 10E9 Msun. Inside the ring, there is a north to south elongated 1.4GHz radio continuum feature with a nuclear peak. This peak is also seen in the 5GHz radio continuum and in the CO. We suggest that the R=300 pc star forming ring represents the radius of a dynamical resonance - as an alternative to the scenario that the starburst is propagating outwards from the center into a molecular ring. The ring-like appearance probably part of a spiral structure. Substantial amounts of molecular gas have passed the radius of the ring and reached the nuclear region. The nuclear peak seen in 5GHz radio continuum and CO is likely related to previous star formation, where all molecular gas was not consumed. The LINER-like optical spectrum observed in NGC1614 may be due to nuclear starburst activity, and not to an Active Galactic Nucleus (AGN). Although the presence of an AGN cannot be excluded.Comment: Accepted by Astronomy and Astrophysics, 12 pages, 10 figure

Two phase transitions in the fully frustrated XYXY model

The fully frustrated $XY$ model on a square lattice is studied by means of Monte Carlo simulations. A Kosterlitz-Thouless transition is found at $T_{\rm KT} \approx 0.446$, followed by an ordinary Ising transition at a slightly higher temperature, $T_c \approx 0.452$. The non-Ising exponents reported by others, are explained as a failure of finite size scaling due to the screening length associated with the nearby Kosterlitz-Thouless transition.Comment: REVTEX file, 8 pages, 5 figures in uuencoded postscrip

The Pion-Nucleon coupling constant from np charge exchange scattering

A novel extrapolation method has been used to deduce the charged Pion-Nucleon coupling constant from backward $np$ differential scattering cross sections. We applied it to new measurements performed at 162 MeV at the The Svedberg Laboratory in Uppsala. In the angular range $150^\circ-180^\circ$, the carefully normalized data are steeper than those of most previous measurements. The extracted value, $g^2_{\pi^\pm} = 14.52 \pm 0.26$, in good agreement with the classical value, is higher than those determined in recent nucleon-nucleon partial-wave analyses.Comment: 6 pages, 3 encapsulated figures, epsfig, menu97.cls (included

Non-Linear I-V Characteristics of Double Schottky Barriers and Polycrystalline Semiconductors

An attempt to determine theoretically the highly non-linear current-voltage (I-V) characteristics of polycrystalline semiconductors, such as ZnO-based varistors, is made from the electrical properties of individual grain boundaries under dc bias. The role played by the fluctuations of double Schottky barrier heights at grain interfaces on driving electrical breakdown phenomena of macroscopic samples is pointed out in terms of a binary mixture model. An alternative trial form for the double Schottky barrier height is introduced to reproduce the breakdown voltage as well as the high non-linear coefficient alpha, where I propto V^{alpha}. ------------- Copies upon request to: [email protected]: CM-ICTP/92/1