ЗАЖИВЛЕНИЕ ПЕРЕЛОМА В УСЛОВИЯХ ИНТРАМЕДУЛЛЯРНОГО ВВЕДЕНИЯ СПИЦ С ПОКРЫТИЕМ ИЗ ГИДРОКСИАПАТИТА

Aim: To study morphological features of the bone formation process in consolidation of fractures of long tubular bones in conditions of intramedullary wires insertion with bioactive calcium-phosphate coating of hydroxyapatite. Materials and methods: In experimental study in dogs was simulated open comminuted tibia fracture and performed intramedullary insertion of wires with hydroxyapatite coating. Using light and electron microscopy, using X-ray electron microprobe microanalyses were studied bone regenerates in 14–360 days after surgery. Results: It was found that around wires there is a formation of an area of active reparative bone formation and angiogenesis, bone shaped case with the properties of the conductor and inducer of osteogenesis. Fracture consolidation is carried out in the early stages of the primary type without formation of cartilage and connective tissue in the bone adhesion. Conclusion: Study results testify that intramedullary wires with hydroxyapatite coating positively influence on the process and intensity of reparative bone formation in fracture healing.Цель исследования: изучить морфологические особенности костеобразовательного процесса при консолидации переломов длинных трубчатых костей в условиях интрамедуллярного введения спиц с биоактивным кальций-фосфатным покрытием из гидроксиапатита. Материалы и методы: в эксперименте на собаках моделировали открытый оскольчатый перелом большеберцовой кости и осуществляли интрамедуллярное введение спиц с покрытием из гидроксиапатита. При помощи световой и электронной микроскопии, рентгеновского электронно-зондового микроанализа исследовали регенераты костей через 14–360 сут после операции. Результаты: установлено, что вокруг спиц образуется зона активного репаративного костеобразования и ангиогенеза, формируется костный футляр со свойствами кондуктора и индуктора остеогенеза. Консолидация перелома осуществляется в ранние сроки по первичному типу без образования хрящевой и соединительной ткани в костной спайке. Выводы: результаты исследования свидетельствуют, что интрамедуллярные спицы с покрытием из гидроксиапатита положительно влияют на течение и интенсивность репаративного костеобразования при заживлении перелома

Advanced configuration of erbium fiber passively Q-switched laser with Co²⁺: ZnSe crystal as saturable absorber

An advanced design of a diode-pumped passively Q-switched erbium fiber laser with a Co2+:ZnSe crystal as a saturable absorber is reported. The laser giant-pulse operation is obtained with threshold of 8.3 mW, repetition rate of pulses of 235 kHz, and pulse energy, peak power, and duration of 15 nJ, 43 mW, and 350 ns, respectively. The self-mode-locking effect in the passively Q-switched fiber laser has been observed experimentally for the first time

Nonlinear dynamics of Ytterbium-doped fiber laser Q-switched using acousto-optical modulator

A comprehensive experimental analysis of the dynamics of an ytterbium-doped fiber laser actively Q-switched (QS) using an intracavity acousto-optical modulator (AOM) is presented. It is shown that type of QS pulsing strongly depends on AOM repetition rate and pump power. In particular, at low repetition rates, including zero-rate, and at relatively high pump powers peculiar QS pulsing, switched by stimulated Brillouin scattering (SBS), is established in the laser. The cause of such kind of pulsing is the SBS-process boosted by spurious narrow-line CW lasing that arises in auxiliary low-Q cavity formed by an output coupler (in our experiments – fiber Bragg gratings) and weak reflections from blocked AOM. The parameters’ area where this regime occurs is limited by certain values of pump power and AOM repetition rate. At increasing AOM repetition rate or decreasing pump power spurious CW lasing is not attained in the system; consequently, the SBS type of QS fades, while “conventional” QS (CQS) lasing is established in the system and remains. However CQS pulsing strongly suffers the nonlinear-dynamics effects: depending on AOM repetition rate and pump power the laser switches to common P1, P2, or P3 attractors, when QS pulses arise at sub-harmonics of AOM repetition rate, or to the specific transient regimes between them, or to chaotic operation. These and other sides (e.g. pulse jittering) of operation of the QS ytterbium-doped fiber laser with AOM are under scope of the present review as they have big interest for practical applications

Dynamics of an erbium-doped fiber laser with pump modulation: Theory and experiment

We study in detail the complex dynamics of an erbium-doped fiber laser that has been subjected to harmonic modulation of a diode pump laser. We introduce a novel laser model that describes perfectly all experimentally observed features. The model is generalized to a nonlinear oscillator. The coexistence of different periodic and chaotic regimes and their relation to subharmonics and higher harmonics of the relaxation oscillation frequency of the laser are demonstrated with codimensional-one and codimensional-two bifurcation diagrams in parameter space of the modulation frequency and amplitude. The phase difference between the laser response and the pump modulation is also investigated. � 2005 Optical Society of America

Seebeck nanoantennas for solar energy harvesting

The characteristics of self-pulsing in a large mode area, end-pumped, double-clad Yb-doped fiber laser are presented. The laser operates in a self-pulsing regime, either by using one or two perpendicularly cleaved ends as the feedback mirrors, while it transforms in a broadband amplified spontaneous emission source when both ends are angle cleaved. In the pulsed regime, up to 2 ?s full width at half maximum pulse widths and repetition rates of the order of hundreds of kHz are generated. " 2014 Astro Ltd.",,,,,,"10.1088/1054-660X/24/10/105107",,,"http://hdl.handle.net/20.500.12104/44445","http://www.scopus.com/inward/record.url?eid=2-s2.0-84907209368&partnerID=40&md5=b76339b04406827c51371f1426f4180f",,,,,,"10",,"Laser Physics",,,,"24",,"Scopu

Self-pulsing in a large mode area, end-pumped, double-clad ytterbium-doped fiber laser

The characteristics of self-pulsing in a large mode area, end-pumped, double-clad Yb-doped fiber laser are presented. The laser operates in a self-pulsing regime, either by using one or two perpendicularly cleaved ends as the feedback mirrors, while it transforms in a broadband amplified spontaneous emission source when both ends are angle cleaved. In the pulsed regime, up to 2 μs full width at half maximum pulse widths and repetition rates of the order of hundreds of kHz are generated. © 2014 Astro Ltd

EXAFS studies of the local structure of bismuth centers in multicomponent silica glass based optical fiber preforms

An Extended X-ray Absorption Fine Structure (EXAFS) analysis of the local structure of bismuth in silicate-glass based optical fiber preforms exhibiting broadband near-infrared luminescence is presented. The valence state of the bismuth ions in alumino-silicate and yttria-alumino-silicate glass hosts is revealed to be Bi3+ and the local geometry is suggested to be a trigonal oxygen pyramid with the electron lone pair positioned opposite to the oxygen atom plane. Furthermore we found that the incorporation of Y2O3 into alumino-silicate glass host does not result in any change in the surrounding Bi structure

Fabrication of large core Yb₂O₃ doped phase separated yttria-alumino silicate nano-particles based optical fiber for use as fiber laser

Development of new rare-earth (RE)-doped optical fibers for high power amplifiers and lasers require continuous improvements in the fiber spectroscopic properties like gain and efficiency characteristics, resistance to spectral hole burning and photodarkening (PD) phenomena besides reduction in device size and economical efficiency. Silica glass as a host material for fibers has proved to be very attractive though some potential applications of RE-doped fibers suffer from limitations in terms of spectroscopic properties resulting from clustering or inappropriate local environment when doped into silica. Several mixed-oxide and non-oxide alternatives to silica have been successfully proposed to obtain spectroscopically improved amplifying single mode fibers in spite of fabrication difficulties and high cost. (& more..

Recent developments in rare-earths doped nano-engineered glass based optical fibers for high power fiber lasers

Recent advances of development of rare-earth (RE) doped optical fibers have become increasingly important due to their applications in various optoelectronic devices such as high power optical fiber amplifiers, fiber lasers, etc. We present a review of recent progress on development of RE-doped glass host based optical fiber materials with special emphasis on large mode area fibers for efficient laser and amplifier. The challenging task is to manage high power inside the active core otherwise output power instability would affect the beam quality. Best solution is to use suitable dopants in addition to active elements during the process of fabrication. Modified chemical vapour deposition (MCVD) process combined with solution doping technique is deployed to develop RE-doped nano-engineered glass based optical fibers through suitable thermal annealing of optical preforms. The developed doped fibers are characterized by DTA, TEM, XRD, XAS, EPMA and EXAFS to assess the structural parameters. This new class of optical fiber materials will open up new possibilities for extended functionality and greater optoelectronic integration

Yb₂O₃ doped yttrium-alumino-silicate nano-particles based LMA optical fibers for high-power fiber lasers

Yb2O3 doped yttrium-rich alumino-silicate nanoparticles based D- and P- (pentagonal) shaped optical fibers with core diameter ~30-35 µm are fabricated using the conventional MCVD process and solution doping technique. Parameters of different stages of the fiber preforms fabrication are optimized to get uniform distributions of Al, Y, F, and Yb ions in the core region, ensured by the data of an EPMA analysis. In the presence of small amounts of fluorine, the size of nano-particles is maintained within 5-10 nm; the EDX data reveal that the nano-particles are rich in yttrium-alumino-silicate phase and are dispersed uniformly across the preforms core. The critical parameters of the processes involved at the fibers fabrication along with the nano-structuring and spectroscopic features are highlighted. It is shown experimentally that the drawn D- and P- shaped fibers support high laser efficiency (80% at 976-nm pumping) and demonstrate negligible photodarkening