Factors associated with diversity, quantity and zoonotic potential of ectoparasites on urban mice and voles

Wild rodents are important hosts for tick larvae but co-infestations with other mites and insects are largely neglected. Small rodents were trapped at four study sites in Berlin, Germany, to quantify their ectoparasite diversity. Host-specific, spatial and temporal occurrence of ectoparasites was determined to assess their influence on direct and indirect zoonotic risk due to mice and voles in an urban agglomeration. Rodent-associated arthropods were diverse, including 63 species observed on six host species with an overall prevalence of 99%. The tick Ixodes ricinus was the most prevalent species, found on 56% of the rodents. The trapping location clearly affected the presence of different rodent species and, therefore, the occurrence of particular host-specific parasites. In Berlin, fewer temporary and periodic parasite species as well as non-parasitic species (fleas, chiggers and nidicolous Gamasina) were detected than reported from rural areas. In addition, abundance of parasites with low host-specificity (ticks, fleas and chiggers) apparently decreased with increasing landscape fragmentation associated with a gradient of urbanisation. In contrast, stationary ectoparasites, closely adapted to the rodent host, such as the fur mites Myobiidae and Listrophoridae, were most abundant at the two urban sites. A direct zoonotic risk of infection for people may only be posed by Nosopsyllus fasciatus fleas, which were prevalent even in the city centre. More importantly, peridomestic rodents clearly supported the life cycle of ticks in the city as hosts for their subadult stages. In addition to trapping location, season, host species, body condition and host sex, infestation with fleas, gamasid Laelapidae mites and prostigmatic Myobiidae mites were associated with significantly altered abundance of I. ricinus larvae on mice and voles. Whether this is caused by predation, grooming behaviour or interaction with the host immune system is unclear. The present study constitutes a basis to identify interactions and vector function of rodent-associated arthropods and their potential impact on zoonotic diseases

Mechanism of Thermal Interaction of In with GaAs

General behavior of In/GaAs couple heat-treated at 570°C for 2 hours was studied with secondary-ion-mass spectrometry, scanning electron microscopy, Rutherford backscattering spectroscopy and Nomarski microscopy. It is shown that, besides the well-known InGaAs crystallites which epitaxially grow upon dissolution of the substrate, In interacts with the substrate dislocations to form In(Ga)As dendrites. The driving force for this process is presumably excess arsenic reported to be present in the vicinity of the individual dislocations

Dual Role of TiN Reaction Barrier in Gold Based Metallization to GaAs

Reactively sputtered TiN films were evaluated as annealing cap improving the formation of Au(Zn) ohmic contact and as antidiffusion barrier protecting contact metallization and underlying GaAs against reaction with Au overlayers

Shallow Ohmic Contact System to n-GaAs

Low resistance (Au)GeNi ohmic contacts to n-GaAs with smooth morphology and restricted penetration into the substrate have been fabricated. Rapid thermally nitrided tungsten has been demonstrated to be an effective capping layer during the contact processing

Changes of GaP: N Defect Structure under Hydrostatic Pressure

The changes of defect structure of GaP:N epitaxial layers subjected to hydrostatic pressures up to 1.8 GPa are investigated by X-ray diffraction and photoluminescence. The observed changes are more pronounced at higher pressures and depend on the nitrogen concentration, c$\text{}_{N}$, and on initial defect structure. Especially complex hydrostatic pressure induced properties are observed for the sample with c$\text{}_{N}$ > 10$\text{}^{20}$ at. cm$\text{}^{-3}$. The model explaining the hydrostatic pressure induced defect structure changes is proposed

ACTA PHYSICA POLONICA Α SHALLOW OHMIC CONTACT SYSTEM TO n-GaAs

Low resistance (Au)GeNi ohmic contacts to n-GaAs with smooth morphology and restricted penetration into the substrate have been fabricated. Rapid thermally nitrided tungsten has been demonstrated to be an effective capping layer during the contact processing. PACS numbers: 73.40.Ns The penetration of metallization during the formation of ohmic contacts to semiconductor microstuctures is one of the most important faction presently limiting the minimum useful size of modern GaAs devices. Consequently, much attention has been recently devoted to the development of shallow ohmic contact systems. Since the first study on the use of AuGeNi metallization Contacts were fabricated on (100) n-GaAs bulk doped with Si at 10 18 cm-3. Prior to the deposition of metallization, the samples were processed in hot organic solvents and etched in ΝΗ4OH+H2O2+Η2O solution. 70 nm thick (Au)GeNi metallization consisting of 10 at.%Au, 45 at.%Ge and 45at.%Νi was thermally evaporated from the resistance-heated crucible. The top tungsten layer of a thickness of 40 nm was deposited by DC magnetron sputtering. To study the effect of annealing conditions on the effectiveness of W cap, comparative experiments involving conventional heat treatment under flowing H2 and rapid thermal annealings in SHS-100 system, in N2 or O2 ambient, have been performed. (804

Electrical, Magnetic, and Structural Properties of Sn1−x\text{}_{1-x}Mnx\text{}_{x}Te Layers Grown by Molecular Beam Epitaxy

Layers of Sn$\text{}_{1-x}$Mn$\text{}_{x}$Te (x ≤ 0.1) with thickness 0.2-2 μm were grown by molecular beam epitaxy on BaF$\text{}_{2}$ substrates with a 0.01-1 μm thick SnTe buffer layer. Both SnTe and Sn$\text{}_{1-x}$Mn$\text{}_{x}$Te layers show metallic p-type conductivity with conducting hole concentrations (at T=77 K) p$\text{}_{77}$=7×10$\text{}^{19}$ -2×10$\text{}^{21}$ cm$\text{}^{-3}$. The layers grown under the conditions of an extra Te flux have a high carrier concentration and exhibit ferromagnetic phase transition at T$\text{}_{C}$ ≤ 7 K. The layers grown with no (or very low) additional Te flux show low carrier concentrations (below 10$\text{}^{20}$ cm$\text{}^{-3}$) and remain paramagnetic in the temperature range studied T=4.5÷70 K

Effect of high temperature-pressure on GaAs layers grown on vicinal Si substrates

The effect of high hydrostatic pressure - high temperature treatment on strain state of thin GaAs layers, grown on vicinal (001) Si substrate, misoriented towards [110] with different miscut angles and with two different orientations of GaAs layer in relation to the miscut direction, was investigated by X-ray diffraction methods. The strain of the GaAs layers and GaAs/Si samples bending decreases when subjected to the treatment at T = 670 K under enhanced hydrostatic pressure (1.2 GPa). Dependence between the stress-induced structural changes and the orientation of GaAs miscut angle as well as peculiarities of the temperature-pressure treatment were determined. It has been shown that the amount of relaxed strain depends on the initial defect structure of the GaAs/Si hetrostructure. After reannealing the samples at higher temperature (870 K - 1.2 GPa), the strain and sample bending were the same as that after the treatment at 670 K - 1.2 GPa but the defect structure of layers was improved

Detection of immunotoxicity using T-cell based cytokine reporter cell lines ("Cell Chip")

Safety assessment of chemicals and drugs is an important regulatory issue. The evaluation of potential adverse effects of compounds on the immune system depends today on animal experiments. An increasing demand, however, exists for in vitro alternatives. Cytokine measurement is a promising tool to evaluate chemical exposure effects on the immune system. Fortunately, this type of measurement can be performed in conjunction with in vitro exposure models. We have taken these considerations as the starting point to develop an in vitro method to efficiently screen compounds for potential immunotoxicity. The T-cell lymphoma cell line EL-4 was transfected with the regulatory sequences of interleukin (IL)-2, IL-4, IL-10, interferon (IFN)-gamma or actin fused to the gene for enhanced green fluorescent protein (EGFP) in either a stabile or a destabilised form. Consequently, changes in fluorescence intensity represent changes in cytokine expression with one cell line per cytokine. We used this prototype "Cell Chip" to test, by means of flow cytometry, the immunomodulatory potential of 13 substances and were able to detect changes in cytokine expression in 12 cases (successful for cyclosporine, rapamycin, pentamidine, thalidomide, bis(tri-n-butyltin)oxide, house dust mite allergen (Der p I), 1-chloro-2,4-dinitrobenzene, benzocaine, tolylene 2,4-diisocyanate, potassium tetrachloroplatinate, sodium dodecyl sulphate and mercuric chloride; unsuccessful for penicillin G). In conclusion, this approach seems promising for in vitro screening for potential immunotoxicity, especially when additional cell lines besides T-cells are included