Controllable direction of liquid jets generated by thermocavitation within a droplet.

A high-velocity fluid stream ejected from an orifice or nozzle is a common mechanism to produce liquid jets in inkjet printers or to produce sprays among other applications. In the present research, we show the generation of liquid jets of controllable direction produced within a sessile water droplet by thermocavitation. The jets are driven by an acoustic shock wave emitted by the collapse of a hemispherical vapor bubble at the liquid-solid/substrate interface. The generated shock wave is reflected at the liquid-air interface due to acoustic impedance mismatch generating multiple reflections inside the droplet. During each reflection, a force is exerted on the interface driving the jets. Depending on the position of the generation of the bubble within the droplet, the mechanical energy of the shock wave is focused on different regions at the liquid-air interface, ejecting cylindrical liquid jets at different angles. The ejected jet angle dependence is explained by a simple ray tracing model of the propagation of the acoustic shock wave inside the droplet.

Raman-induced polarization stabilization of vector solitons in circularly birefringent fibers.

Vector soliton propagation in circularly birefringent fibers was studied by perturbation analysis and numerically. The results show that in presence of both Raman self-frequency shift and group velocity difference between circularly polarized components the Raman cross-polarization term causes an energy transfer from the slower to the faster circular component of vector solitons. This effect leads to polarization stabilization of circularly polarized vector solitons.

Time-resolved analysis of cavitation induced by CW lasers in absorbing liquids.

We present novel results on thermocavitation using a CW medium-power near infrared laser (lambda=975 nm) focused into a saturated copper nitrate saline solution. Due to the large absorption coefficient at the laser wavelength, the solution can be heated to its superheat limit (T(sh) approximately 270-300 degrees C). Superheated water undergoes explosive phase transition around T(sh) producing approximately half-hemispheric bubbles (gamma approximately 0.5) in close contact with the substrate. We report the temporal dynamic of the cavitation bubble, which is much shorter than previously reported under similar conditions. It was found that the bubble radius and pressure wave amplitude emitted on bubble collapse decreases exponentially with the power laser. Thermocavitation can be a useful tool for the generation of ultrasonic waves and controlled ablation for use in high-resolution lithography.

[Comparison of transthoracic, transesophageal, and intracardiac echocardiography sensitivity for guiding transseptal puncture during radiofrequency ablation in the left atrium].

The paper contains comparison of sensitivity and rates of false negative results of transthoracic (TT), transesophageal (TE), and intracardiac (IC) echocardiography (echoCG) during transseptal puncture in the run of the procedure of radiofrequency ablation of atrial fibrillation. In the work fulfilled we analyzed results of 208 echocardiographical intraprocedural investigations conducted with the aim of visualization of interatrial septum (IAS) during transseptal puncture. TT, TE and IC echoCG were carried out in 32, 26, and 150 cases, respectively. Phenomenon of IAS stretching was visualized by TT echoCG in 2 (6%) cases (sensitivity 6.7%). At TE tenting phenomenon was verified in 20 patients (20%) (sensitivity 86.9%). Puncture of IAS was carried out under IC echoCG control in 127 patients. Puncture was made in the center of thin portion of IAS (in the region of fossa ovalis), in its upper and lower portions in 65, 28, and 15.7% of cases, respectively. Sensitivity of IC echoCG was 98.4%. Rate of false positive results reached 92.8, 13.04 and 1.5% for TT, TE and IC echoCG, respectively. At present IC echoCG is most sensitive and safe ultrasound technique for verification of optimal positioning of the system for conduct of transseptal puncture in the region of IAS in comparison with TT and TE echoCG.

Perturbation series for calculation of invariant surface splitting in volume-preserving maps.

The invariant surface splittings for small perturbation are described for two-dimensional and three-dimensional sample volume-preserving maps by explicit analytic expressions obtained from perturbation series for the self-adjoint operator related to the Frobenius-Perron operator.

[The experience of the use of intracardiac echocardiography during puncture of atrial septum].

We analyzed results of 175 intracardiac ultrasound studies (ICUS) in 113 men (mean age 54,6 +/- 11,0 years) and 62 women (mean age 49,7 +/- 8,9 years) with atrial fibrillation (n=146) and WPW syndrome (n=29). ICUS was used for guidance of catheters or electrodes from right to left atrium through atrial septum in 160 procedures of radiofrequency ablations for atrial fibrillation (n=146) or WPW syndrome (n=14). Complications of transseptal puncture developed in 4 patients (2,7%) with atrial fibrillation. There were no procedure related deaths. In all cases ICUS allowed to visualize interatrial septum and its thinnest part. Thus ICUS facilitates transseptal approach to the left atrium, provides lowering of risk of dangerous complications, and allows real time monitoring of possible intraprocedural complications.

Initial development of supercontinuum in fibers with anomalous dispersion pumped by nanosecond-long pulses.

We propose and compare with experimental data a two-stage model of supercontinuum formation in a fiber for nanosecond-long pulse with intensities in 10 W range. As a result of the first stage, the sea of solitons is formed. The second stage is spectrum modification because of Raman interaction.

Regular approximations to chaotic maps.

We construct regular analytic approximations to partly chaotic maps on a two-dimensional torus-the Standard Map in particular. Possible extensions are discussed.

Spectral limits for periodic pattern propagation in Kerr media.

We consider the propagation of periodic waves with initially narrow spatial spectra in a Kerr medium. The set of constants of motion closely related to the order amplitudes is introduced. It is shown that the spatial spectrum remains uniformly narrow with propagation for both self-focusing and self-defocusing nonlinearity. In addition, for sufficiently weak nonlinearity, initially strong orders always remain strong. Thus the problem is shown to be essentially finite dimensional and well approximated by a proper set of coupled ordinary differential equations.

Propagation dynamics of weakly localized cnoidal waves in dispersion-managed fiber: from stability to chaos.

We study the dynamics of propagation of the pulse train modeled by truncated cnoidal-type wave in a nonlinear dispersion-managed (DM) fiber. Computer simulations permit to select fiber parameters and waveform to ensure self-repeating of wave after the dispersion map period. It is shown that the long-period maps lead to the complicated chaotic behavior of cnoidal type wave, namely the Kolmogorov-Arnold-Moser (KAM) chaos.

Transverse modulational instability of periodic light patterns in photorefractive strontium barium niobate crystal.

Interference fringes produced by the intersection of two plane waves in photorefractive strontium barium niobate crystal break in the transverse direction if the external electric field is high enough. For a certain relation between fringe spacing and nonlinearity strength, the tendency to regular pattern formation has been observed. We present a simple theory that qualitatively explains this effect.

Efficient attractor analysis based on self-dependent subsets of elements--an application to signal transduction studies.

External signals are transmitted to the cells through receptors activating signal transduction pathways. These pathways form a complicated interconnected network, which is able to answer to different stimuli. Here we analyze an important pathway for oncogenesis namely RAS/MAPK signal transduction pathway. We show that the interaction of the elements of this pathway induces topological structure in the element set and that the knowledge of the topology simplifies the analysis of the set. With a computer algorithm, we isolate from a large and complex group, smaller, independent, more manageable subsets, and build their hierarchy. Subsets introduction makes easier the search for attractors in discrete dynamical system, it permits the prediction of final states for elements involved in signal transduction pathways.

Analytical solutions for three and four diffraction orders interaction in Kerr media.

The analytical solution for the interaction of three diffraction orders in the Kerr medium is obtained by reducing the problem to the completely integrable Hamiltonian task. Intensities of all waves are periodic with propagation length and linearly related, the amplitudes are quasi-periodic and expressed in elliptic functions. Symmetrical four-order interaction also admits an analytical solution.

[Transesophageal echocardiography in diagnosis of infectious endocarditis]. / Chrespishchevodnaia ékhokardiografiia v diagnostike infektsionnogo éndokardita.

Transthoracic and transesophagal echocardiography (TT EChG and TE EChG) were performed in 43 patients with infectious endocarditis (IE). Sensitivity and specificity of TE EChG in detection of vegetations were higher (92 and 75%, 81 and 50% for TE EChG and TT EChG, respectively). Vegetations and thromboembolism were unrelated. With TE EChG, morphologically verified perforations of valvular cusps were revealed 3 times more frequently than with TT EChG. Along with detection of vegetations and dysfunction of the prosthetic valve, an essential diagnostic marker of IE of the artificial valve is visualization of paraprosthetic fistulas in 2 of 5 patients. Indications for TT and TE EChG and techniques of their performance are described. TT EChG is used in screening for IE. TE EChG is conducted in complications of IE.

Beam amplification resulting from non-Bragg wave mixing in photorefractive strontium barium niobate.

Two-wave mixing with a small angle between beams in a photorefractive crystal biased with an external electric field leads to the formation of additional non-Bragg orders and to wave amplification. A steady-state gain of 25 cm (-1) was obtained for an external voltage of 3 kV/cm in strontium barium niobate. Noise amplification and oscillation are also demonstrated.

[Non-invasive mapping of cardiac electric potential of a specific quasi-epicardium]. / Neinvazivnoe kartirovanie élektricheskogo potentsiala serdtsa na sfericheskom kvaziépikarde.

A procedure was proposed for non-invasive mapping of the cardiac electrical potential or a spherical quasiepicardium from its synchronous multichannel measurement on the surface of the chest, i.e. routine electrocardiodraphic mapping. Mathematical simulation was used to demonstrate that the quasiepicardial potential can be calculated with the accuracy sufficient for clinical diagnosis by applying the multipole electric field resolution method with allowance made for three lowest resolution terms. Due to the fact that the spherical quasiepicardium is more approximate to the heart and more concentric as to its center than the chest surface, the maps of the quasiepicardial potential permit recognition of some features of the pattern of a cardiac electric process, which do not manifest themselves in the distribution of the potential on the body's surface. The examples showing that the assessment of a cardiac abnormality can be made more accurate by using this method are given in the paper.