48,624 research outputs found
Minimal conductivity in graphene: interaction corrections and ultraviolet anomaly
Conductivity of a disorder-free intrinsic graphene is studied to the first
order in the long-range Coulomb interaction and is found to be
\sigma=\sigma_0(1+0.01 g), where 'g' is the dimensionless ("fine structure")
coupling constant. The calculations are performed using three different
methods: i) electron polarization function, ii) Kubo formula for the
conductivity, iii) quantum transport equation. Surprisingly, these methods
yield different results unless a proper ultraviolet cut-off procedure is
implemented, which requires that the interaction potential in the effective
Dirac Hamiltonian is cut-off at small distances (large momenta).Comment: 5 pages, 1 figure; Reply to the Comment by I.F. Herbut, V. Juricic,
O. Vafek, and M.J. Case, "Comment on "Minimal conductivity in graphene:
Interaction corrections and ultraviolet anomaly" by Mishchenko E. G.",
arXiv:0809.0725, is added in Appendi
Shiga Toxin Detection Methods : A Short Review
The Shiga toxins comprise a family of related protein toxins secreted by
certain types of bacteria. Shigella dysenteriae, some strain of Escherichia
coli and other bacterias can express toxins which caused serious complication
during the infection. Shiga toxin and the closely related Shiga-like toxins
represent a group of very similar cytotoxins that may play an important role in
diarrheal disease and hemolytic-uremic syndrome. The outbreaks caused by this
toxin raised serious public health crisis and caused economic losses. These
toxins have the same biologic activities and according to recent studies also
share the same binding receptor, globotriosyl ceramide (Gb3). Rapid detection
of food contamination is therefore relevant for the containment of food-borne
pathogens. The conventional methods to detect pathogens, such as
microbiological and biochemical identification are time-consuming and
laborious. The immunological or nucleic acid-based techniques require extensive
sample preparation and are not amenable to miniaturization for on-site
detection. In the present are necessary of techniques of rapid identification,
simple and sensitive which can be employed in the countryside with
minimally-sophisticated instrumentation. Biosensors have shown tremendous
promise to overcome these limitations and are being aggressively studied to
provide rapid, reliable and sensitive detection platforms for such
applications.Comment: 16 pages, 2 figure
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