Jiri Kanka

Expression of Growth Differentiation Factor 9 Messenger RNA in Porcine Growing and Preovulatory Ovarian Follicles

Abstract We have shown previously that porcine cumulus and mural granulosa cells produce a factor that is very similar, if not identical, to the oocyte-derived cumulus expansion-enabling factor (CEEF). Because growth differentiation factor 9 (GDF9) is the most likely candidate for the CEEF, in the present study we tested the hypothesis that GDF9 is expressed not only in oocytes in the pig but also in somatic follicular cells. In addition, we asked whether the relative abundance (RA) of GDF9 mRNA changes in oocytes and/or follicular cells during the periovulatory period or culture of oocyte-cumulus complexes (OCCs) in vitro. Denuded oocytes, OCCs, cumulus, and mural granulosa cells were isolated from growing and preovulatory follicles. Total RNA was extracted from the cells, and reverse transcription-polymerase chain reaction (RT-PCR) was carried out using specific oligonucleotide primers. The RT-PCR resulted in amplification of a product of expected size (277 base pairs) in samples prepared from all follicular cell types. The identity of the RT-PCR products with GDF9 was confirmed by analysis of their nucleotide sequence, which was 88% and 91% identical to human and ovine GDF9, respectively. The RA of GDF9 mRNA in the somatic follicular cells was approximately fourfold lower than in oocytes. Assessment of the RA of GDF9 mRNA during the periovulatory period and during culture and expansion of OCCs in vitro revealed that it remained stable in oocytes and mural granulosa cells and decreased significantly in expanding cumulus cells. We conclude that GDF9 mRNA can be produced by somatic follicular cells in the pig and that cumulus expansion is not preceded or accompanied by an increase in the RA of GDF9 mRNA in any of the tested cell types.

Structure fits the purpose: photonic crystal fibers for evanescent-field surface-enhanced Raman spectroscopy

We report numerical simulation and hyperspectral Raman imaging of three index-guiding solid-core photonic crystal fibers (PCFs) of different air-cladding microstructures to assess their respective potential for evanescent-field Raman spectroscopy, with an emphasis on achieving surface-enhanced Raman scattering (SERS) over the entire fiber length. Suspended-core PCF consisting of a silica core surrounded by three large air channels conjoined by a thin silica web is the most robust of the three SERS-active PCFs, with a demonstrated detection sensitivity of 1x10(-10) M R6G in an aqueous solution of only approximately 7.3 microL sampling volume.

Advantage of multi-mode sapphire optical fiber for evanescent-field SERS sensing

An unclad, multi-mode single crystal sapphire fiber was used as a platform, and immobilized colloidal Ag nanoparticles (NPs) were used as enabler, for evanescent-field fiber-optic sensing via surface-enhanced Raman scattering (SERS) of Rhodamine 6G (R6G) solution. The dependence of the measured Raman intensity on NP coverage density (to a maximum of 120  particles/μm²) as well as the coverage length (to a maximum of 6 cm) was investigated. We demonstrate the utility of SERS-active sapphire fibers for sensitive measurements (10⁻⁸ M R6G). We further reveal, with the aid of theoretical analysis, that multi-mode fiber offers a significant advantage compared to its single-mode counterpart because the former allows two orders of magnitude higher particle coverage density than the latter to maximize SERS benefit, while maintaining the dominance of Raman gain despite the competitive interplay of NP-induced absorption and scattering loss along the interaction path length.

Large signal model of TDM-pumped Raman fiber amplifier

In this letter, we study spectral optical signal-to-noise ratio (OSNR) profile of a wide-band Raman fiber amplifier (RFA)with time-division-multiplexed (TDM) pumping. We derive a comprehensive large-signal numerical model which incorporates time variation effects and the downstream propagation of signals, upstream propagation of pumps, and downstream and upstream propagation of amplified spontaneous emission spectral components. We present results for a four-wavelength-pumped discrete RFA with TDM and continuous-wave pumping. Improvement in OSNR flatness of 0.9 dB due to TDM pumping is demonstrated.

Twin-core fiber design and preparation for easy splicing

Several methods of preparing twin-core fibers (TCFs) that can be easily spliced to standard single-core single-mode fiber are proposed. Unlike the conventional TCF preparation methods that are used to fabricate a TCF with both cores placed symmetrically with respect to the fiber axis, these methods result in twin-core fibers that have one core in the fiber center. Experimental results obtained with the TCF fabricated by using one of the designs are presented.

A scalable pathway to nanostructured sapphire optical fiber for evanescent-field sensing and beyond

We here report an innovative and scalable strategy of transforming a commercial unclad sapphire optical fiber to an all-alumina nanostructured sapphire optical fiber (NSOF). The strategy entails fiber coating with metal aluminum followed by anodization to form alumina cladding of highly organized pore channel structure. Through experiments and numerical simulation, we demonstrate the utility and benefit of NSOF, analogous to all-silica microstructured optical fiber, for evanescent-field surface-enhanced Raman scattering (SERS) measurements. We experimentally reveal the feasibility of Ag nanoparticles (NPs)-enabled NSOF SERS sensing of 10−6 M Rhodamine 6G (R6G) after thermal treatment at 500 °C for 6 h by taking advantage of porous anodic aluminum oxide (AAO) structure to stabilize the Ag NPs. We show, via numerical simulations, that AAO cladding significantly increases the evanescent-field overlap, lower porosity of AAO results in higher evanescent-field overlap, and optimized AAO nanostructure yields gre...

Generation of high-repetition-rate pulse trains in a fiber laser through a twin-core fiber

We demonstrate the application of a twin-core fiber comb filter to the generation of high repetition rate pulse trains in fiber lasers. We have found experimentally that passive mode locking of the fiber laser can be established due to concurrent effects of a nearly periodic transmission function of the twin-core fiber filter and of the modulational instability. The period of the generated pulse train is determined by the intermodal dispersion of the twin-core fiber inserted into the fiber laser cavity. A repetition rate as high as 206 GHz was achieved. The width of the generated pulses was 2.7 ps.

Long-period grating and its cascaded counterpart in photonic crystal fiber for gas phase measurement.

Regular and cascaded long period gratings (LPG, C-LPG) of periods ranging from 460 to 590 μm were inscribed in an endlessly single mode photonic crystal fiber (PCF) using CO(2) laser for sensing measurements of helium, argon and acetylene. High index sensitivities in excess of 1700 nm/RIU were achieved in both grating schemes with a period of 460 μm. The sharp interference fringes in the transmission spectrum of C-PCF-LPG afforded not only greatly enhanced sensing resolution, but also accuracy when the phase-shift of the fringe pattern is determined through spectral processing. Comparative numerical and experimental studies indicated LP(01) to LP(03) mode coupling as the principal coupling step for both PCF-LPG and C-PCF-LPG with emergence of multi-mode coupling at shorter grating periods or longer resonance wavelengths.

Photonic crystal fiber for layer-by-layer assembly and measurements of polyelectrolyte thin films

The cladding air channels of an endlessly single-mode photonic crystal fiber (PCF) and the high-index sensitivity of its long-period gratings (LPG) inscribed by CO(2) laser have been exploited to deposit poly(vinyl pyrrolidone) (PVPON)/poly(methacrylic acid) (PMAA) polyelectrolyte thin films via layer-by-layer assembly (LbL) and to measure the deposition process. We show that LbL can be controllably carried out within the axially aligned air channels. PCF-LPG is highly sensitive to the LbL process as reflected by ~1.625 nm shift in the resonance wavelength per polyelectrolyte layer incorporated. PCF-LPG is also very robust for in situ monitoring of the release of PVPON from cross-linked polyelectrolytes, which results in the formation of pH-responsive PMAA hydrogel. PCF-LPG containing the hydrogel exhibits well-behaved response to changes in solution pH over 2 to 7.5. We demonstrate that PCF-LPG is 2 orders of magnitude more sensitive than its traditional all-solid counterpart through parallel investigation.

Design of photonic crystal fibers with highly nonlinear glasses for four-wave-mixing based telecom applications

A fully-vectorial mode solver based on the finite element method is employed in a combination with the downhill simplex method the dispersion optimization of photonic crystal fibers made from highly nonlinear glasses. The nonlinear fibers are designed for telecom applications such as parametric amplification, wavelength conversion, ultra-fast switching and regeneration of optical signals. The optimization is carried in terms of the zero dispersion wavelength, dispersion magnitude and nonlinear coefficient and confinement loss in the wavelength range around 1.55 microm. We restrict our work to the index-guiding fiber structures a small number of hexagonally arrayed air holes.