982 research outputs found
Impact ionization fronts in Si diodes: Numerical evidence of superfast propagation due to nonlocalized preionization
We present numerical evidence of a novel propagation mode for superfast
impact ionization fronts in high-voltage Si -- structures. In
nonlinear dynamics terms, this mode corresponds to a pulled front propagating
into an unstable state in the regime of nonlocalized initial conditions. Before
the front starts to travel, field-ehanced emission of electrons from deep-level
impurities preionizes initially depleted base creating spatially nonuniform
free carriers profile. Impact ionization takes place in the whole high-field
region. We find two ionizing fronts that propagate in opposite directions with
velocities up to 10 times higher than the saturated drift velocity.Comment: 3 pages, 4 figure
Theory of superfast fronts of impact ionization in semiconductor structures
We present an analytical theory for impact ionization fronts in reversely
biased p^{+}-n-n^{+} structures. The front propagates into a depleted n base
with a velocity that exceeds the saturated drift velocity. The front passage
generates a dense electron-hole plasma and in this way switches the structure
from low to high conductivity. For a planar front we determine the
concentration of the generated plasma, the maximum electric field, the front
width and the voltage over the n base as functions of front velocity and doping
of the n base. Theory takes into account that drift velocities and impact
ionization coefficients differ between electrons and holes, and it makes
quantitative predictions for any semiconductor material possible.Comment: 18 pagers, 10 figure
Soliton dual comb in crystalline microresonators
We present a novel compact dual-comb source based on a monolithic optical
crystalline MgF multi-resonator stack. The coherent soliton combs generated
in two microresonators of the stack with the repetition rate of 12.1 GHz and
difference of 1.62 MHz provided after heterodyning a 300 MHz wide
radio-frequency comb. Analogous system can be used for dual-comb spectroscopy,
coherent LIDAR applications and massively parallel optical communications.Comment: 5 pages, 5 figure
To the practical design of the optical lever intracavity topology of gravitational-wave detectors
The QND intracavity topologies of gravitational-wave detectors proposed
several years ago allow, in principle, to obtain sensitivity significantly
better than the Standard Quantum Limit using relatively small anount of optical
pumping power. In this article we consider an improved more ``practical''
version of the optical lever intracavity scheme. It differs from the original
version by the symmetry which allows to suppress influence of the input light
amplitude fluctuation. In addition, it provides the means to inject optical
pumping inside the scheme without increase of optical losses.
We consider also sensitivity limitations imposed by the local meter which is
the key element of the intracavity topologies. Two variants of the local meter
are analyzed, which are based on the spectral variation measurement and on the
Discrete Sampling Variation Measurement, correspondingly. The former one, while
can not be considered as a candidate for a practical implementation, allows, in
principle, to obtain the best sensitivity and thus can be considered as an
ideal ``asymptotic case'' for all other schemes. The DSVM-based local meter can
be considered as a realistic scheme but its sensitivity, unfortunately, is by
far not so good just due to a couple of peculiar numeric factors specific for
this scheme.
From our point of view search of new methods of mechanical QND measurements
probably based on improved DSVM scheme or which combine the local meter with
the pondermotive squeezing technique, is necessary.Comment: 27 pages, 6 figure
Fragmentation of Stability Domains of Dark Solitons and Dark Breathers and Drifting Solitons at High Pump Intensities in Normal Dispersion Kerr Microresonators
Stability domains (i.e. pump frequency detuning range) of a single dark
soliton (or platicon) and dark breather in high-Q Kerr optical microresonators
with normal group velocity dispersion is studied for a wide range of pump
amplitudes within the framework of the Lugiato-Lefever model. The effect of the
significant fragmentation of the stability domains at high pump intensities is
revealed. The existence of stable drifting dark solitons (platicons) is
demonstrated above the threshold pump amplitude value. Properties of drifting
solitons are investigated.Comment: 28 pages, 13 figures; to appear in PR
Optimizing the regimes of Advanced LIGO gravitational wave detector for multiple source types
We develop here algorithms which allow to find regimes of signal-recycled
Fabry-Perot--Michelson interferometer (for example, Advanced LIGO), optimized
concurrently for two (binary inspirals + bursts) and three (binary inspirals +
bursts + millisecond pulsars) types of gravitational waves sources. We show
that there exists a relatevely large area in the interferometer parameters
space where the detector sensitivity to the first two kinds of sources differs
only by a few percent from the maximal ones for each kind of source. In
particular, there exists a specific regime where this difference is ~0.5 for
both of them. Furthermore we show that even more multipurpose regimes are also
possible, that provide significant sensitivity gain for millisecond pulsars
with only minor sensitivity degradation for binary inspirals and bursts.Comment: 10 pages, 14 figures, 3 tables. Minor corrections in main text are
done in version 2 and two plots and one table are added for the sake of
clarity of the obtained result
Comparison of survival rates made by the 6-th and 7-th editions of TNM classification in stomach cancer patients
The available classifications of malignant tumors reflect various aspects of their
growth and some biological features. The most commonly used in Ukraine is the 6-th revision of TNM
classification, which differs from the previous classifications of the section "Gastric cancer", mainly
staging of category N, reflecting the presence of metastases in regional lymph nodes. Transition to the
7-th classification of TNM translates a part of patients from one stage to another, there is a so-called
"stage migration" phenomenon. The famous mathematical phenomenon of Will Rogers describes this
transition and theoretically substantiates its objectivity. The authors tracked the migration of patients
and the change in the stage mainly from the point of view of the effect of this event on the survival of
patients with stomach cancer
Evaluation advanced lymph node dissection impact on long-term survival rate of gastric cancer patients. Journal of Education
Over a period of 2007-2011 188 stomach cancer (SC) patients have been included in the
research in abdominal oncosurgical department of Odessa regional oncological dispensary. It
was retrospective, one-center, nonrandomized research. Volume of lymph node dissections
differed by quantity of lymph nodes to be removed. All patients were divided into three groups.
Patients with D1 or D1+ lymph node dissections have been performed, totally 90 patients are
included in group of historical control. The main group includes 33 patients to whom D3 lymph
node dissections is executed and, finally, control group – 65 patients dissected up to the D2
volume. In all cases so-called lymph node dissections for principal reasons have been executed.
The multifactorial analysis of patients survival is implemented depending on a type of a lymph
node dissections, a stage of the cancer, number of involved lymph nodes, involvement of the
tumoral microcirculatory net (ly is carried out, v) signs of a perinevral invasion (Nev),
availability of residual tumoral tissue (R), degree of a differentiation (G). Regardless of a disease
stage, SC at 60% of patients, represented with initially hematologicaly disseminated disease.
40% of SC`s had no signs of intratumoral microcirculatory net involvement even in case of more
than 15 regional lymph nodes are involved. In the absence of a SC perinevral invasion appeared
to be the most precise predictive marker. The conclusion is made some brand new additional53
prognostic factors could play a crucial role in more accurate patients selection for expanded
lymph node dissections
Analysis of survival after radical surgery for stomach cancer in odessa regional cancer center
The survival of patients with the locally advanced stage of stomach cancer
(SC), who underwent various variants of preventive lymphatic nodes
dissection, was considered. The survival of patients was compared with the
stage and T, N indexes. Lymphadenectomy D2 were effective and increased
cumulative survival in patient`s group T4aNoMo, stage IIB and T4aN1Mo,
stage III A, and in groups of patients where D2 lymphadenectomy were
ineffective - T4bNoMo, stage ІІІB, T4bN1Мo, stage ІІІB and T4aN2Мo,
stage IIIB. D2 were more efficient operation in the case of tumor serosa
invasion and invasion to the peritoneal cavity (SE) in the absence of multiple
metastases to the regional lymph nodes (N1 according to the 7th revision of
the classification - 1-2 metastatic lymph nodes), and when
the tumor infiltrated the surrounding organs (SI) and the presence of multiple
regional metastases, D2 lymphodissection did not gave positive results,
comparising with D1
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