2,410 research outputs found
The Importance of the Study of the Hemodynamics of the Uterine Tumors by the Method of Dopplerometry in the Two- and Three-dimensional Echography Modes for Differential Diagnostics of Simple, Proliferating Leiomyomas and Uterine Sarcomas (Review of Litera
The article analyzes modern literature data on the importance of studying the hemodynamics of uterine tumors with dopplerometry in two - and three - dimensional regimens of echography for differential diagnosis of simple proliferating leiomyomas and sarcomas of the uterus. It is shown that the differential diagnosis of benign and Malignant tumors using the dopplerometry is based on various features of the blood supply of these tumors. On the basis of the analysis of literature data, it was concluded that in the dopplerometry evaluation of benign, borderline and Malignant tumors of myometrium in the two-dimensional regime, there were differences in the localization of the detected vessels in the CDM regimen, in the rates of vascular blood flow and vascular resistance in pulse dopplerometry. For a simple leiomyoma, the absence of a central intra-node localization of blood vessels in the CDM regimen, a low rate of arterial and venous blood flow, as well as an average resistance of arterial blood flow in the regime of impulsive dopplerometry are most typical; in a leiomyoma with eating disorders, the absence of a central intra-node localization of blood vessels, a low rate of arterial and venous blood flow in combination with high arterial resistance were more often observed. For the proliferating leiomyoma, the central intra-node localization of the vessels and the average blood flow velocities with low and medium resistance are characteristic. For sarcoma of the uterus, there is abundant vascularization both around the periphery and in the center, high blood flow rates and low resistance. The authors emphasize that there is information about the low specificity of this gradation, since the detection of a central type of vascularization and low resistance values can be in simple myomatous nodes with edema, eating disorders and destruction, and leads to diagnostic errors and suspicion of Malignancy. In the three-dimensional dopplerometry mode for simple leiomyomas, low indices of volume perfusion indices were characteristic, and for proliferating leiomyomas and sarcomas of the uterus – high indices of volume perfusion indices exceeding those in the uterus as a whole.Based on the review of the literature, the authors concluded that the presently available echographic and dopplerometric two- and three-dimensional markers are characterized by high sensitivity, but very low specificity. The low specificity of the known ultrasonic and dopplerometric criteria combined with the rarity of cases of sarcoma in the uterus against the background of a large number of similar echographically and dopplerometrically leiomyomas lead to low diagnostic accuracy of ultrasound diagnostics. This situation requires a further continuation of the scientific search for differential diagnostic ultrasound criteria by leiomyomas and sarcomas of the uterus using modern technologies, including three-dimensional echography
When renormalizability is not sufficient: Coulomb problem for vector bosons
The Coulomb problem for vector bosons W incorporates a known difficulty; the
boson falls on the center. In QED the fermion vacuum polarization produces a
barrier at small distances which solves the problem. In a renormalizable SU(2)
theory containing vector triplet (W^+,W^-,gamma) and a heavy fermion doublet F
with mass M the W^- falls on F^+, to distances r ~ 1/M, where M can be made
arbitrary large. To prevent the collapse the theory needs additional light
fermions, which switch the ultraviolet behavior of the theory from the
asymptotic freedom to the Landau pole. Similar situation can take place in the
Standard Model. Thus, the renormalizability of a theory is not sufficient to
guarantee a reasonable behavior at small distances for non-perturbative
problems, such as a bound state problem.Comment: Four page
Frequency comparisons and absolute frequency measurements of 171Yb+ single-ion optical frequency standards
We describe experiments with an optical frequency standard based on a laser
cooled Yb ion confined in a radiofrequency Paul trap. The
electric-quadrupole transition from the ground state to the
state at the wavelength of 436 nm is used as the reference
transition. In order to compare two Yb standards, separate
frequency servo systems are employed to stabilize two probe laser frequencies
to the reference transition line centers of two independently stored ions. The
experimental results indicate a relative instability (Allan standard deviation)
of the optical frequency difference between the two systems of only, so that shifts in the sub-hertz range can be
resolved. Shifts of several hertz are observed if a stationary electric field
gradient is superimposed on the radiofrequency trap field. The absolute optical
transition frequency of Yb at 688 THz was measured with a cesium atomic
clock at two times separated by 2.8 years. A temporal variation of this
frequency can be excluded within a relative uncertainty of yr. Combined with recently published values for the constancy
of other transition frequencies this measurement provides a limit on the
present variability of the fine structure constant at the level of
yr.Comment: 12 pages, 5 figures, Proceedings of MPLP'04, Novosibirsk, August
22.-27., 200
Comparison of two single-ion optical frequency standards at the sub-Hertz level
We describe experimental investigations on an optical frequency standard
based on a laser cooled 171Yb+ ion confined in a radiofrequency Paul trap. The
electric-quadrupole transition from the 2S1/2(F=0) ground state to the
2D3/2(F=2) state at the wavelength of 436 nm is used as the reference
transition. The reference transition is probed by a frequency-doubled,
frequency-stabilized diode laser and is resolved with a Fourier-limited full
halfwidth of approximately 30 Hz. In order to compare two 171Yb+ standards,
separate frequency shift and servo systems are employed to stabilise the probe
frequency to the reference transition line centers of two independently stored
171Yb+ ions. The present experimental results indicate a relative instability
(Allan standard deviation)of the optical frequency difference between
the two systems of sigma_y(1000 s)=1.0E-15 and a mean frequency difference of
0.2 Hz. Shifts in the range of several Hertz are observed in the frequency
difference if a stationary electric field gradient is superimposed on the
radiofrequency trap field. This measurement permits a first experimental
estimate of the electric quadrupole moment of the 2D3/2 state of Yb+.Comment: To appear in "Laser Spectroscopy XVI", eds: P. Hannaford, A. Sidorov,
H. Bachor, and K. Baldwin (World Scientific, Singapore, 2004
Monopole Vector Spherical Harmonics
Eigenfunctions of total angular momentum for a charged vector field
interacting with a magnetic monopole are constructed and their properties
studied. In general, these eigenfunctions can be obtained by applying vector
operators to the monopole spherical harmonics in a manner similar to that often
used for the construction of the ordinary vector spherical harmonics. This
construction fails for the harmonics with the minimum allowed angular momentum.
These latter form a set of vector fields with vanishing covariant curl and
covariant divergence, whose number can be determined by an index theorem.Comment: 21 pages, CU-TP-60
Statistics of layered zigzags: a two-dimensional generalization of TASEP
A novel discrete growth model in 2+1 dimensions is presented in three
equivalent formulations: i) directed motion of zigzags on a cylinder, ii)
interacting interlaced TASEP layers, and iii) growing heap over 2D substrate
with a restricted minimal local height gradient. We demonstrate that the
coarse-grained behavior of this model is described by the two-dimensional
Kardar-Parisi-Zhang equation. The coefficients of different terms in this
hydrodynamic equation can be derived from the steady state flow-density curve,
the so called `fundamental' diagram. A conjecture concerning the analytical
form of this flow-density curve is presented and is verified numerically.Comment: 5 pages, 4 figure
Flux- and volume-limited groups/clusters for the SDSS galaxies: catalogues and mass estimation
We provide flux-limited and volume-limited galaxy group and cluster
catalogues, based on the spectroscopic sample of the SDSS data release 10
galaxies. We used a modified friends-of-friends (FoF) method with a variable
linking length in the transverse and radial directions to identify as many
realistic groups as possible. The flux-limited catalogue incorporates galaxies
down to m_r = 17.77 mag. It includes 588193 galaxies and 82458 groups. The
volume-limited catalogues are complete for absolute magnitudes down to M_r =
-18.0, -18.5, -19.0, -19.5, -20.0, -20.5, and -21.0; the completeness is
achieved within different spatial volumes, respectively. Our analysis shows
that flux-limited and volume-limited group samples are well compatible to each
other, especially for the larger groups/clusters. Dynamical mass estimates,
based on radial velocity dispersions and group extent in the sky, are added to
the extracted groups. The catalogues can be accessed via http://cosmodb.to.ee
and the Strasbourg Astronomical Data Center (CDS).Comment: 16 pages, 18 figures, 2 tables, accepted for publication in A&
Endoscopic and surgical treatment of the Mirizzi syndrome
Academia Medicală de Studii Postuniversitare, Harkov, Ucraina, Al XII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova cu participare internațională 23-25 septembrie 2015Introducere: Sindromul Mirizzi se caracterizează prin compresia căii biliare de către colecist sau formarea unei fistule între
acestea, care corespunde tipului Mirizzi I şi II (McSherry, 1984). Diagnosticul se confirmă prin ERCP. Corecţia chirurgicală este
complexă şi adesea în cazurile de Mirizzi II este necesară aplicarea hepaticojejunostomiei.
Scop: Evaluarea oportunităţilor tratamentului endoscopic şi chirurgical al sindromului Mirizzi pentru păstrarea pasajului bilei
spre duoden.
Material şi metode: Dintre 2144 pacienţi cu litiază biliară, obstrucţia căilor biliare a fost evidențiată la 328 (15,3%). Sindromul
Mirizzi a fost diagnosticat în 21 (6,4%) cazuri: de tip I – la 6 (28,6%) pacienţi, de tip II – la 15 (71,4%).
Rezultate: În două cazuri de Mirizzi I iniţial a fost practicat drenajul biliar transnazal, într-un caz – stentarea ductului biliar
comun. Colecistectomia laparoscopică s-a efectuat la 5 pacienţi şi deschisă – la unul. La 2 din 15 (13,3%) pacienţi cu Mirizzi II
s-a reuşit litotripsia, la un bolnav a fost realizată stentarea biliară. Pentru a reduce icterul în 12 cazuri a fost aplicat drenajul biliar
transnazal. Ulterior, 9 pacienţi au suportat colecistectomie cu plastia defectului ductului biliar comun, la 2 bolnavi s-a efectuat
colecistectomie laparoscopică cu extragerea calculilor biliari, şi într-un caz s-a practicat hepaticojejunostomia. Astfel, la 14 din
15 (93,3%) bolnavi cu Mirizzi II pasajul biliar fiziologic a fost restabilit cu succes. Mortalitatea postoperatorie a constituit 0,
morbiditatea – 19% (4 pacienţi).
Concluzie: Aplicarea tratamentului endoscopic şi chirurgical la pacienţii cu Mirizzi II a permis restabilirea pasajul biliar fiziologic
în 93% din cazurile noastre.Introduction: The Mirizzi syndrome is characterized by compression of bile duct by gallbladder or fistula formation between
them, that corresponds to the Mirizzi type I and type II (McSherry, 1984). The diagnosis confirms by ERCP. Surgical correction
is complex and often needs hepaticojejunostomy in cases of Mirizzi II.
Aim: Evaluate opportunities of the endoscopic and surgical treatment of Mirizzi syndrome in the preservation of bile passage to
the duodenum.
Material and methods: Among 2144 patients with cholelithiasis, biliary tract obstruction occurred in 328 (15.3%). Mirizzi
syndrome was diagnosed in 21 (6.4%): type I – in 6 (28.6%) patients, type II – in 15 (71.4%).
Results: In two cases of Mirizzi I initially transnasal biliary drainage was performed and in one – the common bile duct stenting.
In 5 patients laparoscopic and in one open cholecystectomy was performed. In 2 of 15 (13.3%) patients with Mirizzi II lithotr ipsy
was successful; in one bile duct stenting was performed. To reduce jaundice in 12 cases transnasal biliary drainage was
introduced. Thereafter, 9 patients underwent cholecystectomy with the common bile duct defect plasty, 2 patients underwent
laparoscopic cholecystolitotomy with bile duct stones extraction, and in one case hepaticojejunostomy was formed. Thus, in 14
of 15 (93.3%) of Mirizzi II physiological bile passage was successfully restored. Postoperative mortality was 0, morbidity was
19% (4 patients).
Conclusion: The use of endoscopic and surgical treatment in cases of Mirizzi II allowed restoring the physiological bile
passage in 93% of cases
Testing resistance of apple cultivars to Marssonina coronaria
The apple pathogen Marssonina coronaria (teleomorph: Diplocarpon mali) has recently become a significant problem in Central European organic apple production, causing dark spots on both the leaves and fruit, and early leaf fall. Field observations and resistance testing under controlled conditions indicate that there are differences in resistance to M.coronaria between cultivars. We screened 39 apple cultivars, selected from a large collection of genetic resources, for their susceptibility or resistance to M.coronaria. 1 year old saplings were artificially inoculated under semi-controlled conditions. The development of disease symptoms was observed and assessed several times over more than two months. Symptoms varied largely between cultivars, from small spots on which acervuli immediately developed to large round brown necrotic spots, often with one acervulus in the centre. Leaf fall often started in the middle of the shoot and in parallel on the lower, older leaves. Even though important differences in susceptibility were observed, no cultivar with complete resistance was identified. The observations suggest that resistance to the disease is complex, and involves a number of mechanisms
Atomic clocks with suppressed blackbody radiation shift
We develop a nonstandard concept of atomic clocks where the blackbody
radiation shift (BBRS) and its temperature fluctuations can be dramatically
suppressed (by one to three orders of magnitude) independent of the
environmental temperature. The suppression is based on the fact that in a
system with two accessible clock transitions (with frequencies v1 and v2) which
are exposed to the same thermal environment, there exists a "synthetic"
frequency v_{syn} (v1-e12 v2) largely immune to the BBRS. As an example, it is
shown that in the case of ion 171Yb+ it is possible to create a clock in which
the BBRS can be suppressed to the fractional level of 10^{-18} in a broad
interval near room temperature (300\pm 15 K). We also propose a realization of
our method with the use of an optical frequency comb generator stabilized to
both frequencies v1 and v2. Here the frequency v_{syn} is generated as one of
the components of the comb spectrum and can be used as an atomic standard.Comment: 5 pages, 2 figure
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