176 research outputs found
Metrological characterization of the pulsed Rb clock with optical detection
We report on the implementation and the metrological characterization of a
vapor-cell Rb frequency standard working in pulsed regime. The three main parts
that compose the clock, physics package, optics and electronics, are described
in detail in the paper. The prototype is designed and optimized to detect the
clock transition in the optical domain. Specifically, the reference atomic
transition, excited with a Ramsey scheme, is detected by observing the
interference pattern on a laser absorption signal.
\ The metrological analysis includes the observation and characterization of
the clock signal and the measurement of frequency stability and drift. In terms
of Allan deviation, the measured frequency stability results as low as
, being the averaging time, and
reaches the value of few units of for s, an
unprecedent achievement for a vapor cell clock. We discuss in the paper the
physical effects leading to this result with particular care to laser and
microwave noises transferred to the clock signal. The frequency drift, probably
related to the temperature, stays below per day, and no evidence of
flicker floor is observed.
\ We also mention some possible improvements that in principle would lead to
a clock stability below the level at 1 s and to a drift of few units
of per day
Towards the electron EDM search. Theoretical study of PbF
We report ab initio relativistic correlation calculations of potential curves
and spectroscopic constants for four lowest-lying electronic states of the lead
monofluoride. We also calculated parameters of the spin-rotational Hamiltonian
for the ground and the first excited states including P,T-odd and P-odd terms.
In particular, we have obtained hyperfine constants of the Pb nucleus.
For the state MHz, MHz and for
the A MHz, MHz. Our values of
the ground state hyperfine constants are in good agreement with the previous
theoretical studies. We discuss and explain seeming disagreement in the sign of
the constant with the recent experimental data. The effective
electric field on the electron , which is important for the planned
experiment to search for the electric dipole moment of the electron, is found
to be 3.3 * 10^{10} V/cm
ETEKOS experimental ecological system
The problem of changes in the ecology resulting, for example, in increases in water temperature because of discharges from large thermal power plants is considered. An experiment creating a model of such an ecological system is described
On Nonperturbative Calculations in Quantum Electrodynamics
A new approach to nonperturbative calculations in quantum electrodynamics is
proposed. The approach is based on a regular iteration scheme for solution of
Schwinger-Dyson equations for generating functional of Green functions. The
approach allows one to take into account the gauge invariance conditions (Ward
identities) and to perform the renormalization program. The iteration scheme
can be realized in two versions. The first one ("perturbative vacuum")
corresponds to chain summation in the diagram language. In this version in
four-dimensional theory the non-physical singularity (Landau pole) arises which
leads to the triviality of the renormalized theory. The second version
("nonperturbative vacuum") corresponds to ladder summation and permits one to
make non-perturbative calculations of physical quantities in spite of the
triviality problem. For chiral-symmetrical leading approximation two terms of
the expansion of the first-step vertex function over photon momentum are
calculated. A formula for anomalous magnetic moment is obtained. A problem of
dynamical chiral symmetry breaking (DCSB) is considered, the calculations are
performed for renormalized theory in Minkowsky space. In the strong coupling
region DCSB-solutions arise. For the renormalized theory a DCSB-solution is
also possible in the weak coupling region but with a subsidiary condition on
the value of .Comment: 31 pages, Plain LaTex, no figures. Journal version: some discussion
and refs. are adde
Sampling and counting genome rearrangement scenarios
Even for moderate size inputs, there are a tremendous number of optimal rearrangement scenarios, regardless what the model is and which specific question is to be answered. Therefore giving one optimal solution might be misleading and cannot be used for statistical inferring. Statistically well funded methods are necessary to sample uniformly from the solution space and then a small number of samples are sufficient for statistical inferring
Лимфаденэктомия у больных раком почки
Sixty hundred and twenty-six case histories of patients with renal-cell carcinoma, who underwent nephrectomy at the Department of Oncourology, P.A. Herzen Moscow Research Oncological Institute, in November 1992 to November 2005, have been restrospectively analyzed.Results. Metastatic lymph nodal lesion was identified in 23 (6.49%) patients of 354 patients with renal-cell carcinoma without distant metastasis, who had undergone regional lymphadenectomy. Metastatic regional lymph nodal lesions were found in 9 (2.54%) patients on preoperative examination (as verified by ultrasound study and computed tomography). Metastatic lymph nodal lesion was intraoperatively suspected in 3 (0.85%) patients. This was revealed in 11 (3.11%) patients after planned histological study.Conclusion. The frequency of metastatic regional lymph nodal lesions is 3.11% in patients with early renal-cell carcinoma with unaltered regional lymph nodes, as shown by preoperative and operative examinations. In renal-cell carcinoma, the probability of metastasis into the regional lymph nodes increases in patients with a more 5-cm renal tumor, in those with non-clear or mixed carcinoma, and or those with a locally advanced tumorous process.
A Unifying Model of Genome Evolution Under Parsimony
We present a data structure called a history graph that offers a practical
basis for the analysis of genome evolution. It conceptually simplifies the
study of parsimonious evolutionary histories by representing both substitutions
and double cut and join (DCJ) rearrangements in the presence of duplications.
The problem of constructing parsimonious history graphs thus subsumes related
maximum parsimony problems in the fields of phylogenetic reconstruction and
genome rearrangement. We show that tractable functions can be used to define
upper and lower bounds on the minimum number of substitutions and DCJ
rearrangements needed to explain any history graph. These bounds become tight
for a special type of unambiguous history graph called an ancestral variation
graph (AVG), which constrains in its combinatorial structure the number of
operations required. We finally demonstrate that for a given history graph ,
a finite set of AVGs describe all parsimonious interpretations of , and this
set can be explored with a few sampling moves.Comment: 52 pages, 24 figure
Таксотер® — новый стандарт лечения гормонорефрактерного рака предстательной железы
One of the options in the treatment of hormone-refractory prostate cancer is the administration of cytostatic agents. This article addresses the Taxoter — one of the cytostatic agents. Clinical studies discussed in the article have demonstrated the high activity and efficacy of the agent which allows using it in the treatment of hormone-refractory prostate cancer.
ИССЛЕДОВАНИЕ СОСТОЯНИЯ МЕТАЛЛА В ПРОЦЕССЕ РАДИАЛЬНО-СДВИГОВОЙ ПРОКАТКИ НА СТАНЕ СРВП-130
Radial-shear rolling is prominent in production of titanium alloys at «VSMPO-AVISMA» Open Society (V. Salda city) and has a number of advantages over other plastic metal working processes. In the present investigation on the basis of engineering design procedures, a complex of software has been developed for forming simulation and heat transfer in the metal volume,and with its help the rolling of VT-6 alloy bar of 155 mm in diameter has been studied. «ThermoRSR» program has been developed that allows us to visualize design data in «Mathcad» medium; rolling process simulation has been carried out by means of DEFORM-3D package; and the conditions of its application are shown. Prospective ways of rolled stock temperature and rolling torque measurement are considered.Радиально-сдвиговая прокатка (РСП) играет большую роль в производстве титановых сплавов в ОАО «ВСМПО-АВИСМА» (г. В. Салда), имея ряд преимуществ перед другими процессами обработки металлов давлением. В настоящем исследовании на базе инженерных методик расчета разработан комплекс программных средств для моделирования формоизменения и теплопередачи в объеме металла и с его помощью изучена прокатка прутка диаметром 155 мм из сплава ВТ-6. Разработана программа «ThermoRSR», позволяющая визуализировать расчетные данные в среде «Mathcad», проведено моделирование процесса прокатки с помощью пакета DEFORM-3D и показаны условия его применимости. Рассмотрены перспективные способы измерения температуры проката и крутящего момента на шпинделе прокатного стана
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