STUDY OF ACOUSTIC SIGNAL DURING LASER HYDROACOUSTIC PROCESSING OF BIOLOGICAL TISSUE BY MICROSECOND PULSES OF YTTERBIUM-ERBIUM GLASS LASER RADIATION

Subject of Research.The paper describes the research results of an acoustic signal recorded by a hydrophone while effect on a liquid by microsecond pulses of laser radiation with a wavelength of 1.54 μm and different time substructure. We discuss the influence of energy and time substructure of the laser pulse on the magnitude of generated pressure drops in the liquid and removal efficiency of cataract eye lens tissues. Method. Microsecond pulses of ytterbium-erbium glass laser radiation with different peak power of the "leading" spike and equivalent energy were delivered to the volume of distilled water through an optical fiber. The acoustic signal was registered with "NP 10-1" needle hydrophone (Dapco Inc., USA). An in vitro hydroacoustic treatment of cataract human eye lens was performed. Main Results. We obtained the dependences of the amplitude of the first (thermo-optical) and the second (associated with "collapse-rebound" process of a steam-gas cavity) components of the acoustic signal on the pulse energy for laser pulses with different time substructures. It was established that with an increase in the peak power of the "leading" spike of microsecond pulse, the threshold for the appearance of the second component decreases, and the maximum amplitude of both components increases. The angular distributions of the amplitude of acoustic signal components were obtained. It was found that the first component has a pronounced maximum amplitude in a direction perpendicular to the optical axis of the fiber, whereas the angular distribution of the second component is more uniform. In the in vitro experiment, it was shown that an increase in the peak power of the "leading" spike results in a significant increase in the removed volume and removal efficiency of the human cataract eye lens. Practical Relevance. The obtained results can be used to optimize the parameters of laser radiation for processing of tissue surrounded by a liquid, for example, during laser cataract extraction

ИСКУССТВО ФУГИ: РИСК

The text offered to the reader is the first part of the monograph being prepared for publication (the approximate release date is the end of 2019) by two authors – A. M. Sergeev and B. G. Sokolov – «the Art of Fugue». The Fugue is a musical form and, at the same time, a poisonous fish, the art of cooking which puts at risk the death of someone who dares to taste it. Already in this first part sounds one of the cross-cutting themes of this work – Risk. Risk as a philosophical theme has always remained in the shadow of the main problems of philosophy, but in one form or another present in philosophical texts. The authors pass the topic of risk through two adjacent problem fields: the field of Master-Slave and Male-FemaleПредлагаемый читателю текст – первая часть готовящейся к изданию монографии (ориентировочный срок выхода – конец 2019 года) книги двух авторов – А.М.Сергеева и Б.Г. Соколова – «Искусство Фуги». Фуга – музыкальная форма и, одновременно, ядовитая рыба, искусство приготовления которой ставит перед риском смерти того, кто отваживается ее отведать. Уже в этой первой части звучит одна из сквозных тем тем данной работы – Риск. Риск как философская тема всегда оставалась в тени магистральных проблем философии, однако в том или ином виде присутствуя в философских текстах. Тему риска авторы пропускают через две смежные проблемные поля: поле Господина-Раба, и Мужского-Женского

Influence of temperature gradients on tunnel junction thermometry below 1 K: cooling and electron-phonon coupling

We have studied thermal gradients in thin Cu and AlMn wires, both experimentally and theoretically. In the experiments, the wires were Joule heated non-uniformly at sub-Kelvin temperatures, and the resulting temperature gradients were measured using normal metal-insulator-superconducting tunnel junctions. The data clearly shows that even in reasonably well conducting thin wires with a short ($\sim 10 \mu$m) non-heated portion, significant temperature differences can form. In most cases, the measurements agree well with a model which includes electron-phonon interaction and electronic thermal conductivity by the Wiedemann-Franz law.Comment: J. Low Temp. Phys. in pres

Non-perturbative calculations for the effective potential of the PTPT symmetric and non-Hermitian (−gϕ4)(-g\phi^{4}) field theoretic model

We investigate the effective potential of the $PT$ symmetric $(-g\phi^{4})$ field theory, perturbatively as well as non-perturbatively. For the perturbative calculations, we first use normal ordering to obtain the first order effective potential from which the predicted vacuum condensate vanishes exponentially as $G\to G^+$ in agreement with previous calculations. For the higher orders, we employed the invariance of the bare parameters under the change of the mass scale $t$ to fix the transformed form totally equivalent to the original theory. The form so obtained up to $G^3$ is new and shows that all the 1PI amplitudes are perurbative for both $G\ll 1$ and $G\gg 1$ regions. For the intermediate region, we modified the fractal self-similar resummation method to have a unique resummation formula for all $G$ values. This unique formula is necessary because the effective potential is the generating functional for all the 1PI amplitudes which can be obtained via $\partial^n E/\partial b^n$ and thus we can obtain an analytic calculation for the 1PI amplitudes. Again, the resummed from of the effective potential is new and interpolates the effective potential between the perturbative regions. Moreover, the resummed effective potential agrees in spirit of previous calculation concerning bound states.Comment: 20 page

Exawatt-Zettawatt Pulse Generation and Applications

A new amplification method, weaving the three basic compression techniques, Chirped Pulse Amplification (CPA), Optical Parametric Chirped Pulse Amplification (OPCPA) and Plasma Compression by Backward Raman Amplification (BRA) in plasma, is proposed. It is called C3 for Cascaded Conversion Compression. It has the capability to compress with good efficiency kilojoule to megajoule, nanosecond laser pulses into femtosecond pulses, to produce exawatt and beyond peak power. In the future, C3 could be used at large-scale facilities such as the National Ignition Facility (NIF) or the Laser Megajoule (LMJ) and open the way to zettawatt level pulses. The beam will be focused to a wavelength spot size with a f#1. The very small beam size, i.e. few centimeters, along with the low laser repetition rate laser system will make possible the use of inexpensive, precision, disposable optics. The resulting intensity will approach the Schwinger value, thus opening up new possibilities in fundamental physics.Comment: 13 pages, 4 figure

Large enhancement of deuteron polarization with frequency modulated microwaves

We report a large enhancement of 1.7 in deuteron polarization up to values of 0.6 due to frequency modulation of the polarizing microwaves in a two liters polarized target using the method of dynamic nuclear polarization. This target was used during a deep inelastic polarized muon-deuteron scattering experiment at CERN. Measurements of the electron paramagnetic resonance absorption spectra show that frequency modulation gives rise to additional microwave absorption in the spectral wings. Although these results are not understood theoretically, they may provide a useful testing ground for the deeper understanding of dynamic nuclear polarization.Comment: 10 pages, including the figures coming in uuencoded compressed tar files in poltar.uu, which also brings cernart.sty and crna12.sty files neede

Energetic particle influence on the Earth's atmosphere

This manuscript gives an up-to-date and comprehensive overview of the effects of energetic particle precipitation (EPP) onto the whole atmosphere, from the lower thermosphere/mesosphere through the stratosphere and troposphere, to the surface. The paper summarizes the different sources and energies of particles, principally galactic cosmic rays (GCRs), solar energetic particles (SEPs) and energetic electron precipitation (EEP). All the proposed mechanisms by which EPP can affect the atmosphere are discussed, including chemical changes in the upper atmosphere and lower thermosphere, chemistry-dynamics feedbacks, the global electric circuit and cloud formation. The role of energetic particles in Earth’s atmosphere is a multi-disciplinary problem that requires expertise from a range of scientific backgrounds. To assist with this synergy, summary tables are provided, which are intended to evaluate the level of current knowledge of the effects of energetic particles on processes in the entire atmosphere

Astronomical Distance Determination in the Space Age: Secondary Distance Indicators

The formal division of the distance indicators into primary and secondary leads to difficulties in description of methods which can actually be used in two ways: with, and without the support of the other methods for scaling. Thus instead of concentrating on the scaling requirement we concentrate on all methods of distance determination to extragalactic sources which are designated, at least formally, to use for individual sources. Among those, the Supernovae Ia is clearly the leader due to its enormous success in determination of the expansion rate of the Universe. However, new methods are rapidly developing, and there is also a progress in more traditional methods. We give a general overview of the methods but we mostly concentrate on the most recent developments in each field, and future expectations. © 2018, The Author(s)

Search for Gravitational Waves Associated with Gamma-Ray Bursts Detected by Fermi and Swift during the LIGO-Virgo Run O3b

We search for gravitational-wave signals associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the second half of the third observing run of Advanced LIGO and Advanced Virgo (2019 November 1 15:00 UTC-2020 March 27 17:00 UTC). We conduct two independent searches: A generic gravitational-wave transients search to analyze 86 GRBs and an analysis to target binary mergers with at least one neutron star as short GRB progenitors for 17 events. We find no significant evidence for gravitational-wave signals associated with any of these GRBs. A weighted binomial test of the combined results finds no evidence for subthreshold gravitational-wave signals associated with this GRB ensemble either. We use several source types and signal morphologies during the searches, resulting in lower bounds on the estimated distance to each GRB. Finally, we constrain the population of low-luminosity short GRBs using results from the first to the third observing runs of Advanced LIGO and Advanced Virgo. The resulting population is in accordance with the local binary neutron star merger rate. © 2022. The Author(s). Published by the American Astronomical Society