40 research outputs found
Shot noise of series quantum point contacts intercalating chaotic cavities
Shot noise of series quantum point contacts forming a sequence of cavities in
a two dimensional electron gas are studied theoretically and experimentally.
Noise in such a structure originates from local scattering at the point
contacts as well as from chaotic motion of the electrons in the cavities. We
found that the measured shot noise is in reasonable agreement with our
theoretical prediction taking the cavity noise into account.Comment: 4 pages, 5 figure
Influence of a Random Telegraph Process on the Transport through a Point Contact
We describe the transport properties of a point contact under the influence
of a classical two-level fluctuator. We employ a transfer matrix formalism
allowing us to calculate arbitrary correlation functions of the stochastic
process by mapping them on matrix products. The result is used to obtain the
generating function of the full counting statistics of a classical point
contact subject to a classical fluctuator, including extensions to a pair of
two-level fluctuators as well as to a quantum point contact. We show that the
noise in the quantum point contact is a sum of the (quantum) partitioning noise
and the (classical) noise due to the two-level fluctuator. As a side result, we
obtain the full counting statistics of a quantum point contact with
time-dependent transmission probabilities.Comment: 8 pages, 2 figure; a new section about experiments and a figure
showing the crossover from sub- to superpoissonian noise have been adde
Адресная доставка фотосенсибилизатора для фотохимиотерапии витилиго
Aim. In this work, the authors set out to develop an effective method for the intrafollicular delivery of “Ammi majus fructuum furocumarines” photosensitizer (AMFF) followed by UVA irradiation (λ = 320–400 nm). Materials and methods. The proposed delivery method consists in using calcium carbonate particles acting as AMFF carriers. In vivo monitoring of hair follicle filling was carried out via optical coherence tomography, as well as by means of analyzing epilated hair using confocal laser scanning microscopy. Following the administration of free and encapsulated AMFF to three healthy volunteers, the character of UVA-induced skin pigmentation was registered under dermatoscopic examination. Results. The obtained results demonstrate a profuse filling of hair follicles with calcium carbonate particles, thus confirming the possibility of intrafollicular photosensitizer delivery. It was established that exposure to UVA irradiation causes intense pigment accumulation in the area of AMFF carrier administration. Conclusion. The proposed method of the targeted photosensitizer delivery allows photochemical therapy to be improved.Цель: разработка эффективного способа доставки фотосенсибилизатора Ammi majus fructuum furocumarines (AMFF) в волосяные фолликулы с последующим применением УФА-облучения (λ = 320–400 нм). Материалы и методы. Предлагаемый способ доставки заключается в применении частиц карбоната кальция, выступающих в роли контейнера-носителя AMFF. Исследование заполнения волосяных фолликулов было проведено in vivo методом оптической когерентной томографии, а также путем экстракции волос с последующим исследованием методом лазерной конфокальной флуоресцентной микроскопии. Регистрация характера пигментации кожи 3 здоровых добровольцев после сеанса УФА-облучения участков с предварительным внедрением препарата AMFF в свободном и иммобилизованном виде была осуществлена методом дерматоскопии. Результаты. Продемонстрировано обильное заполнение волосяных фолликулов частицами карбоната кальция, доказана возможность интрафолликулярной доставки фотосенсибилизатора с их помощью. Установлено, что в результате УФА-облучения в месте внедрения контейнеров, нагруженных AMFF, происходит значительное накопление пигмента. Заключение. Предложенный способ адресной доставки фотосенсибилизатора позволяет оптимизировать методику фотохимиотерапевтического воздействия
Nonlocal effects in the shot noise of diffusive superconductor - normal-metal systems
A cross-shaped diffusive system with two superconducting and two normal
electrodes is considered. A voltage is applied between the normal
leads. Even in the absence of average current through the superconducting
electrodes their presence increases the shot noise at the normal electrodes and
doubles it in the case of a strong coupling to the superconductors. The
nonequilibrium noise at the superconducting electrodes remains finite even in
the case of a vanishingly small transport current due to the absence of energy
transfer into the superconductors. This noise is suppressed by
electron-electron scattering at sufficiently high voltages.Comment: 4 pages, RevTeX, 2 eps figure
Shot noise in tunneling transport through molecules and quantum dots
We consider electrical transport through single molecules coupled to metal
electrodes via tunneling barriers. Approximating the molecule by the Anderson
impurity model as the simplest model which includes Coulomb charging effects,
we extend the ``orthodox'' theory to expand current and shot noise
systematically order by order in the tunnel couplings. In particular, we show
that a combined measurement of current and shot noise reveals detailed
information of the system even in the weak-coupling limit, such as the ratio of
the tunnel-coupling strengths of the molecule to the left and right electrode,
and the presence of the Coulomb charging energy. Our analysis holds for
single-level quantum dots as well.Comment: 8 page
Shot Noise in Nanoscale Conductors From First Principles
We describe a field-theoretic approach to calculate quantum shot noise in
nanoscale conductors from first principles. Our starting point is the
second-quantization field operator to calculate shot noise in terms of single
quasi-particle wavefunctions obtained self-consistently within density
functional theory. The approach is valid in both linear and nonlinear response
and is particularly suitable in studying shot noise in atomic-scale conductors.
As an example we study shot noise in Si atomic wires between metal electrodes.
We find that shot noise is strongly nonlinear as a function of bias and it is
enhanced for one- and two-Si wires due to the large contribution from the metal
electrodes. For longer wires it shows an oscillatory behavior for even and odd
number of atoms with opposite trend with respect to the conductance, indicating
that current fluctuations persist with increasing wire length.Comment: 4 pages, 4 figure
Electron-electron scattering effects on the Full Counting Statistics of Mesoscopic Conductors
In the hot electron regime, electron-electron scattering strongly modifies
not only the shot noise but also the full counting statistics. We employ a
method based on a stochastic path integral to calculate the counting statistics
of two systems in which noise in the hot electron regime has been
experimentally measured. We give an analytical expression for the counting
statistics of a chaotic cavity and find that heating due to electron-electron
scattering renders the distribution of transmitted charge symmetric in the shot
noise limit. We also discuss the frequency dispersion of the third order
correlation function and present numerical calculations for the statistics of
diffusive wires in the hot electron regime
Shot Noise at High Temperatures
We consider the possibility of measuring non-equilibrium properties of the
current correlation functions at high temperatures (and small bias). Through
the example of the third cumulant of the current () we demonstrate
that odd order correlation functions represent non-equilibrium physics even at
small external bias and high temperatures. We calculate for a quasi-one-dimensional diffusive constriction. We calculate the
scaling function in two regimes: when the scattering processes are purely
elastic and when the inelastic electron-electron scattering is strong. In both
cases we find that interpolates between two constants. In the low (high)
temperature limit is strongly (weakly) enhanced (suppressed) by the
electron-electron scattering.Comment: 11 pages 4 fig. submitted to Phys. Rev.
Encapsulation of basic fibroblast growth factor by polyelectrolyte multilayer microcapsules and its controlled release for enhancing cell proliferation
10.1021/bm3005879Biomacromolecules1372174-2180BOMA