8,084 research outputs found
Dengue Vectors and their Spatial Distribution
The distribution of dengue vectors, Ae. aegypti and Ae. albopictus, is affected by climatic factors. In addition, since their life cycles are well adapted to the human environment, environmental changes resulting from human activity such as urbanization exert a great impact on vector distribution. The different responses of Ae. aegypti and Ae albopictus to various environments result in a difference in spatial distribution along north-south and urban-rural gradients, and between the indoors and outdoors. In the north-south gradient, climate associated with survival is an important factor in spatial distribution. In the urban-rural gradient, different distribution reflects a difference in adult niches and is modified by geographic and human factors. The direct response of the two species to the environment around houses is related to different spatial distribution indoors and outdoors. Dengue viruses circulate mainly between human and vector mosquitoes, and the vector presence is a limiting factor of transmission. Therefore, spatial distribution of dengue vectors is a significant concern in the epidemiology of the disease
Low temperature metallic state induced by electrostatic carrier doping of SrTiO
Transport properties of SrTiO-channel field-effect transistors with
parylene organic gate insulator have been investigated. By applying gate
voltage, the sheet resistance falls below 10 k at low
temperatures, with carrier mobility exceeding 1000 cm/Vs. The temperature
dependence of the sheet resistance taken under constant gate voltage exhibits
metallic behavior (/ 0). Our results demonstrate an insulator to
metal transition in SrTiO driven by electrostatic carrier density control.Comment: 3 pages, 4 figure
Negative Differential Resistance Induced by Mn Substitution at SrRuO3/Nb:SrTiO3 Schottky Interfaces
We observed a strong modulation in the current-voltage characteristics of
SrRuO/Nb:SrTiO Schottky junctions by Mn substitution in SrRuO,
which induces a metal-insulator transition in bulk. The temperature dependence
of the junction ideality factor indicates an increased spatial inhomogeneity of
the interface potential with substitution. Furthermore, negative differential
resistance was observed at low temperatures, indicating the formation of a
resonant state by Mn substitution. By spatially varying the position of the Mn
dopants across the interface with single unit cell control, we can isolate the
origin of this resonant state to the interface SrRuO layer. These results
demonstrate a conceptually different approach to controlling interface states
by utilizing the highly sensitive response of conducting perovskites to
impurities
Field Effect Transistor Based on KTaO3 Perovskite
An n-channel accumulation-type field effect transistor (FET) has been
fabricated utilizing a KTaO3 single crystal as an active element and a
sputtered amorphous Al2O3 film as a gate insulator. The device demonstrated an
ON/OFF ratio of 10^4 and a field effect mobility of 0.4cm^2/Vs at room
temperature, both of which are much better than those of the SrTiO3 FETs
reported previously. The field effect mobility was almost temperature
independent down to 200K. Our results indicate that the Al2O3 / KTaO3 interface
is worthy of further investigations as an alternative system of future oxide
electronics.Comment: 3 pages, 3 Postscript figures, submitted to Appl.Phys.Let
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