Pump and thermal impact on heavily erbium-doped fiber laser generation.

A detailed comparative study of heavily erbium-doped fiber laser generation features was carried out in the case of 1490 nm and 976 nm wavelength pumping. The laser cavity was designed using point-by-point fiber Bragg grating inscription technology with femtosecond laser pulses. The CW and Q-switched lasing regimes were achieved depending on temperature and heat sink performance. It was found experimentally for the first time, to the best of our knowledge, that the frequency and pulse duration of Q-switched laser operations are primarily determined by the output laser power and do not depend on the pump wavelength. The pulse formation is caused by the lasing process itself and depends on the up-conversion rate at the generation wavelength. Additionally, the level of laser cavity heating at the Q-switched generation regime was defined.

Dynamic photonic crystal in a colloidal quantum-dot solution: formation, structure analysis, and dimensionality switching.

We demonstrated, for the first time, to the best of our knowledge, a simple method to create three-dimensional (3D) dynamic photonic crystal (PhC) with controllable lattice symmetry through the interference of four non-coplanar laser beams in a non-linear optical medium [colloidal solution of CdSe/ZnS quantum dots (QDs)]. 3D dynamic PhC was formed due to the periodically changing refraction and absorption of resonantly excited excitons in the colloidal solution of QDs. The formation of dynamic PhC was confirmed by the observed self-diffraction of the laser beams on the dynamic structure which they have created. Tuning of the PhC dimensionality to the two-dimensional (2D) and one-dimensional (1D) was done through the reduction of the number of interfering beams to three and two, respectively, and by controlling the polarization of interacting beams. Physical processes responsible for the observed self-action effects that arise in CdSe/ZnS QDs are discussed in detail.

All-fiber heavily ytterbium-doped, passively mode-locked laser with the 456 MHz repetition rate.

In this Letter, we report on, to the best of our knowledge, the first demonstration of ultrashort pulses generation with an all-fiber laser with the repetition rate of up to 456 MHz, without the use of additional nonlinear optical elements. It was possible to obtain this repetition rate thanks to the use of a specially manufactured heavily doped ytterbium fiber. The generation dynamics of the laser assembled according to the classical Fabry-Perot scheme with two fiber Bragg gratings was investigated. The formation of ultrashort pulses as a result of passive mode-locking (ML) is presented. Passive ML is attributed to the absorption saturation, while the role of the saturable absorber in the active optical fiber with a high ytterbium ion concentration plays itself.

Juvenile idiopathic arthritis patients and their skeletal status: possible role of vitamin D receptor gene polymorphism.

We evaluated bone mineralization and metabolism changes related to vitamin D receptor (VDR) polymorphic genotypes in children with juvenile idiopathic arthritis. One hundred and ninety eight children (82 boys and 116 girls) were included in our study. Bone mineral density (BMD) was measured by lumbar spine DXA. Osteocalcin, CTX, parathyroid hormone, total and ionized calcium, inorganic phosphate, total alkaline phosphatase activity was utilized for assessment of bone metabolism. Molecular testing: TaqI (rs731236) and Cdx2 (rs11568820) polymorphisms of VDR were detected by RFLP. No differences in TaqI and Cdx2 haplotypes, genotypes and alleles distribution related with normal and low BMD (Zscore <-2SD) were found. Children with low linear growth (<10th percentile) had more allele T-contained genotypes of TagI VDR (p = 0.037), compare with medium or high linear growth children. Children with high linear growth (>90th percentile) had the highest frequency of allele A-contained genotypes (GA+AA) of Cdx2 VDR (p = 0.009). Girls with TT TaqI VDR, who never been treated by glucocorticoides had lower BMD-Zscore than C allele carriers (TT = -0.94SD [IQR: -2.1;-0.5], TC+CC = -0.62SD [IQR: -1.26;0.39], p = 0.03). Girls with Tanner I with TT had higher total and ionized Ca level than carriers of C allele (Ca: TT = 2.43 ± 0.15 mmol/l, TC+CC = 2.28 ± 0.2 mmol/l, p = 0.024; Ca(2+): TT = 1.15 ± 0.08 mmol/l, TC+CC = 1.06 ± 0.13 mmol/l, p = 0.026). Presence of TT genotype negatively correlated with BMD-Zscore (r = -0.28, p = 0.04), and positively with frequency of LBMD (r = 0.3, p = 0.037). Boy with GG Cdx2 genotype had lower total Ca (GG = 2.3 ± 0.17 mmol/l, GA+AA = 2.43 ± 0.17 mmol/l, p = 0.004) compare with carriers of A allele. Pubertal boys (Tanner IV-V) with GG had higher CTX (GG = 1.75 ± 0.11 ng/ml, GA+AA = 1.06 ± 0.07 ng/ml, p = 0.04. TT genotype of TaqI and GG genotype of Cdx2 VDR is a negative factor impact bone mineralization metabolism and linear growth.

[Comparative assessment of MR-semiotics of acutest intracerebral hematomas in low- and extra high-field frequency magnetic resonance tomography].

An objective of the study was to compare sensitivity of low- and extra high-field frequency magnetic resonance (MR) tomography of acutest intracerebral hematomas (ICH) and to assess differences between symptoms in obtained images. A study was conducted using experimental ICH in rats (n=6). Hematomas were formed by two injections of autologic blood into the brain. MR-devices "Bio Spec 70/30" with magnetic field strength of 7 T and "Ellipse-150" with magnetic field strength of 0,15 T were used in the study. MR-tomography was carried out 3-5 h after the injections. Both MR-devices revealed the presence of pathological lesion in all animals. Extra highfield frequency MR-tomography showed the specific signs of ICH caused by the paramagnetic effect of deoxyhemoglobin in T2 and T2*-weighted images (WI) and low frequency MR-tomography - in T2*-WI only. The comparable sensitivity of low- and extra high-field frequency MR-devices in acutest ICH was established.

[Possibility of an emission computer tomography for an estimation cerebral perfusion at patients with carotid stenoses before and after stenting].

THE PURPOSE: To estimate possibilities for studies of cerebral perfusion with brain scintigraphy for revealing and an estimation of features of change brain perfusion at patients with a cardio-cerebral vascular pathology before and after carotid stenting (CAS). MATERIAL AND METHODS: 11 patients with established (after carotid angiography) stenosis of internal carotid artery and coronary artery disease have been studied with SPECT with analogue HMPAO teoxim--Tc99M after intravenous introduction 700 MBk up to and in 5 days and in the remote period after stenting. For analysis of results the program "Neurogam" have been used. Standartized perfusion maps have been created. RESULTS: Before performing CAS various variants of the image cerebral perfusion maps have been obtained: from diffuse insignificant reduction in both hemispheres of a brain up to the regions hypoperfusion, characteristic for ischemic changes. Regions of hypoperfusion on the side opposite to a stenosis or occasion were revealed. SPECT, performed after cas on 5th day or after 2-3 months found increase of general brain perfusion, disappearance of symmetric both asymmetric regions hypoperfusion and reduction of a degree local hypoperfusion on the side of stenting. CONCLUSIONS: Maps of brain perfusion before and after CAS adequately reflect microcirculation of a brain with local changes of perfusion. Use of perfusion parameters gives possibility to estimate changes of brain perfusion before and after CAS in patients with combined carotid and coronary pathology.

[The lack of cyclin-dependent phosphoprotein kinase Pho85p leads to defects in mitochondrial nucleoid transmission in yeast Saccharomyces cerevisiae].

Cyclin-dependent phosphoprotein kinases (CDK) play essential role in the regulation of the progression through different phases of the cell cycle, being also involved in metabolic regulation and in actin cytoskeleton organization. The Saccharomyces cerevisiae CDK Pho85p is associated with 10 different cyclins and phosphorylates different substrates, among these transcription factors Pho4p and Gcn4p, and a protein involved in actin polymerization being a homologue of amphiphysin 1 of mammalian Rvs167p. It is known that mutations in the PHO85 gene have a multiple pleotropic effects, one of these effects being a rapid accumulation of mitochondrial [rho-] mutations observed on the background of gene PHO85 inactivation. In this study it was shown that the appearance of [rho-] clones is a result of some defects in mitochondrial nucleoid transmission from mother to bud cells.