270 research outputs found
Spectrum for the electric dipole which nonradially falling into a black hole
The electromagnetic bremsstrahlung spectrum for the dipole which falling by a
spiral orbit into the Schwarzschild black hole was found. The characteristic
features in this electromagnetic spectrum can be used for determine of the
black hole mass by the new way. This new way (if implemented) provides higher
accuracy in determining of the black hole mass. Also these features in the
spectrum can be used for determine of the certain characteristics in the black
hole magnetosphere or in the accretion disk characteristics around the black
hole. It is also shown that the asymptotic behavior of this spectrum (at high
frequencies) is practically independent from the impact parameter of the
falling dipole.Comment: 15 pages, 3 figures. To appear in IJMPD, 201
Constructive control of quantum systems using factorization of unitary operators
We demonstrate how structured decompositions of unitary operators can be
employed to derive control schemes for finite-level quantum systems that
require only sequences of simple control pulses such as square wave pulses with
finite rise and decay times or Gaussian wavepackets. To illustrate the
technique it is applied to find control schemes to achieve population transfers
for pure-state systems, complete inversions of the ensemble populations for
mixed-state systems, create arbitrary superposition states and optimize the
ensemble average of dynamic observables.Comment: 28 pages, IoP LaTeX, principal author has moved to Cambridge
University ([email protected]
Evidence of a kallikrein inhibitor in human kidney. A new ring of the kallikrein-renin-angiotensin-aldosterone chain
By means of immunohistochemical reactions, the authors proved the inhibitor II-related immunoreactivity in distal convoluted tubules of human kidney. A sharp inhibitor II-related immunoreactivity was also present in the blood vessels' wall. On the contrary, in the wall of proximal tubules and glomeruli only low reactivity was found. The demonstration of an inhibitor II-related immunoreactivity in the distal convoluted tubules and vessels of human kidney represents a strong evidence that an inhibitor of kallikrein exists and acts also in humans as an important key in the kallikrein-renin-angiotensin aldosterone chain and hitherto confirms the experimental data of the literature. The proved inhibitor in the human kidney may intervene in the modulation of the kallikrein-kinin system and thus represents a key role in the intrarenal mechanisms related to the blood flow and arterial pressure regulation
Anharmonicity, vibrational instability and Boson peak in glasses
We show that a {\em vibrational instability} of the spectrum of weakly
interacting quasi-local harmonic modes creates the maximum in the inelastic
scattering intensity in glasses, the Boson peak. The instability, limited by
anharmonicity, causes a complete reconstruction of the vibrational density of
states (DOS) below some frequency , proportional to the strength of
interaction. The DOS of the new {\em harmonic modes} is independent of the
actual value of the anharmonicity. It is a universal function of frequency
depending on a single parameter -- the Boson peak frequency, which
is a function of interaction strength. The excess of the DOS over the Debye
value is at low frequencies and linear in in the
interval . Our results are in an excellent
agreement with recent experimental studies.Comment: LaTeX, 8 pages, 6 figure
Coherent population transfer in a chain of tunnel coupled quantum dots
We consider the dynamics of a single electron in a chain of tunnel coupled
quantum dots, exploring the formal analogies of this system with some of the
laser-driven multilevel atomic or molecular systems studied by Bruce W. Shore
and collaborators over the last 30 years. In particular, we describe two
regimes for achieving complete coherent transfer of population in such a
multistate system. In the first regime, by carefully arranging the coupling
strengths, the flow of population between the states of the system can be made
periodic in time. In the second regime, by employing a "counterintuitive"
sequence of couplings, the coherent population trapping eigenstate of the
system can be rotated from the initial to the final desired state, which is an
equivalent of the STIRAP technique for atoms or molecules. Our results may be
useful in future quantum computation schemes
Coherent control using adaptive learning algorithms
We have constructed an automated learning apparatus to control quantum
systems. By directing intense shaped ultrafast laser pulses into a variety of
samples and using a measurement of the system as a feedback signal, we are able
to reshape the laser pulses to direct the system into a desired state. The
feedback signal is the input to an adaptive learning algorithm. This algorithm
programs a computer-controlled, acousto-optic modulator pulse shaper. The
learning algorithm generates new shaped laser pulses based on the success of
previous pulses in achieving a predetermined goal.Comment: 19 pages (including 14 figures), REVTeX 3.1, updated conten
Momentum transfer using chirped standing wave fields: Bragg scattering
We consider momentum transfer using frequency-chirped standing wave fields.
Novel atom-beam splitter and mirror schemes based on Bragg scattering are
presented. It is shown that a predetermined number of photon momenta can be
transferred to the atoms in a single interaction zone.Comment: 4 pages, 3 figure
Patterns of Forming the Urban Surface Deposited Sediments
The contemporary sedimentation processes participate in the formation of fluxes of the solid substances in an urban area, forming together a source of pollution, transit and depositing media. The patterns of forming the urban surface deposited sediments were determined on the example of Russian metropolis Nizhny Novgorod. Two schemes of the research were implemented in residential districts of the city in the summer field season 2018. The first research design scheme represented a detailed survey of residential quarters of the city. It included a collection of 25 samples of environmental compartments from five residential quarters with multi-storey buildings. The sampling was conducted in various functional landscape parts at the courtyard and facade areas. Each sample was separated into particle size fractions. Chemical and mineral analysis was performed in each granulometric subsample of the collected samples. The second scheme represented the urban geochemical study based on sampling the sediments from local surface depressed zones of microrelief in the city. The 40 samples were collected at the territory of the city on an irregular grid. The sampling was carried out in residential areas in blocks with multi-storey buildings. One sample represented a combined sample of sediments from local surface zones of microrelief by 3-5 localizations from the area of the block. Chemical analysis of the collected samples was conducted. The maximum content of dust (0.002-0.01 mm) 39% was found in soil, while the lower mean dust content was found in the samples of sediment from local surface depressed zones of microrelief (30 %) and in the road deposited sediments (30 %). The mineral composition of soil and sediment in Nizhny Novgorod is represented by quartz sand (approx. 55 %). In the samples of sediments, the minerals' content is basically characteristic for acid and metasomatic rocks. Building materials' content in the sediments reaches up to 20%. The maximum organic matter content was found in fine dust fraction 2-10 microns 21% in soils and 5% on the roads. Differentiation of the mineral content in the samples is observed for the various particle size fractions and different functional parts of the quarters. The highest content of metals of anthropogenic association (such as Pb, Zn and Cu) was found in the dust fraction. The Pb and Zn concentrations in samples of sediment of depressed areas of microrelief and road dust were significantly lower than in the soil. © Published under licence by IOP Publishing Ltd.Russian Science Foundation, RSF: 18-77-10024The study was supported by Russian Science Foundation (grant No. 18-77-10024)
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