Photonic crystal bers are optical waveguides based on a periodic air-glass structure o ering higher design exibility compared to that of standard single-mode bers. On one hand, such bers allow for ...extremely tight mode con nement related to increased nonlinearity and better chromatic dispersion controllability. On the other hand, photonic crystal bers enable light guiding in very large cores keeping the single-mode regime of operation and low loss.This doctoral thesis deals with scienti c problems related to control of light propagation within photonic crystal bers and it contributes mainly to the areas of optics, photonics, telecommunication and sensing. The objective is to describe main design principles, nd their limitations and consequently optimize ber geometries. Until now, these limitations have not been investigated thoroughly and therefore became the central point for the doctoral thesis.The goal is not to present ber structures with novel geometries, but to investigate new limits in designing photonic crystal bers. One of the presented designs is a photonic crystal ber with a dispersion parameter as close as possible to zero value. Further e ort is applied on a hexagonal ber structure that is optimized to operate as a dispersion compensator of standard single-mode bers. The author predicts that the negative dispersion parameter cannot be higher in this structure operating over a bandwidth larger than that considered in this thesis.Another important part of the thesis aims to control of con nement loss, which is used to design a narrowband ber lter as well as an e ectively single-mode photonic crystal ber with large e ective mode area and chalcogenide background.Fiber designs were carried out by varying key geometrical parameters such as holeto- hole spacing, airhole diameters in selected rings and number of rings around the ber core. The in uence of each structural parameter on modal properties is examined and described in detail. Understanding the mechanism governing chromatic dispersion as well as con nement loss is necessary not only for the ber design, but also to predict the potential manufacturing tolerances.Last but not least, supercontinuum generation is investigated in the designed chalcogenide ber using the split-step Fourier method. The modal properties are calculated by the full-vectorial nite di erence frequency domain method. The simulation models of presented bers are veri ed by convergence testing.
The paper deals with the experimental analysis focused on the determination of strain in wooden building structures using optical fibers with FBG sensors. Firstly, optical fibers were used to measure ...displacements of layers and surface strain of the lower surface of the ceiling panels made from mechanically jointed cross laminated timber (CLT). The measured displacement values of the optical fibers were compared with the results obtained from the inductive displacement sensors. Secondly, optical fibers were used for long-term monitoring of the roof structure of the sports hall. The fibers were mounted on chords of timber trusses and their correct function was verified by a load test.
In this paper, an effectively single mode reasonably bendable leakage channel fibre is designed having the highly nonlinear As 2 S 3 chalcogenide glass as the fibre background. The fibre is designed ...to have effective mode area as large as possible as well as to have low confinement loss in the bent fibre. The fibre modal properties are calculated through the finite difference frequency domain method to investigate supercontinuum generation inside the designed fibre. Using the light pump near the zero dispersion wavelength at 4.9 μm, the supercontinuum is numerically observed as nearly flat and broad from 3 to 8 μm.
Questions
We sampled epiphytic bryophytes along the entire vertical gradient, from tree base to upper canopy, in tropical and subtropical forests in order to answer the following questions: (a) how ...do diversity, composition and life forms differ between forests; (b) how do communities change along the vertical gradient in each forest; (c) what are the likely environmental drivers of this; and (d) what is the conservation significance of the results?
Location
Canopy crane sites in tropical lowland seasonal rain forest (TRF) and subtropical montane moist forest (STF) in Yunnan, southwest China.
Methods
Bryophytes were sampled from 1,600–2,400 cm2 of bark surface in 14 vertical segments in three canopy layers on 142 trees, using canopy cranes. Microclimate was measured at five levels on the crane towers. Diversity was compared within and between forests using ANOVA. NMDS was used to compare species composition and assess potential drivers.
Results
In total, 184 species were recorded in 106 genera and 39 families. STF had a richer bryoflora than TRF. More species occurred in the canopy than the sub‐canopy and understorey in both sites. The fan life form was dominant in the lower two layers of both forests, while mats were more common in the canopy of TRF and tall turfs in STF. The main axis of variation in species composition was associated with the vertical gradient of declining humidity and vapour pressure, and increasing temperature, light and wind speed.
Conclusions
This study demonstrates the value of canopy cranes for complete sampling of the epiphytic bryoflora in complex forests. Both forest types had very high species richness, reflecting the diversity of microhabitats along the vertical gradient. Observed and projected climate change may threaten this bryoflora as a result of rising temperatures and, in some areas, declining rainfall and fog frequency.
Epiphytic bryophytes—mosses, liverworts, and hornworts—are diverse and important in tropical and subtropical forests, but studies have been limited by difficult access to the forest canopy. We took advantage of the construction of two new canopy cranes in southwest China to conduct the first systematic study of the vertical gradient in bryophyte diversity and species composition in this region.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NMLJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
The results of the inter-RMO key comparison EURAMET.L-K5.2016 on the calibration of a step gauge are reported. Twenty-two National Metrology Institutes from four different metrological regions all ...over the world participated in this comparison which lasted three years, from December 2015 to December 2018.
Two artefacts were circulated so that the varying ranges of participants equipment could be accommodated. A 1020 mm ceramic monolithic step gauge remained stable throughout the comparison. A 610 mm steel step gauge changed length, possibly due to an impact while travelling between participants. The comparison of this artefact was divided into two groups, those before the damage and those after, with the reference value for each group derived from a linking participant who had demonstrated equivalence in the 1020 mm artefact circulation. For the 1020 mm comparison the inverse-variance weighted mean was taken as reference value.
Of the twenty two participants, eleven successfully demonstrated the validity of the claimed measurement capability. Of the remaining 11, 3 submitted revised uncertainties after the initial circulation of results which were shown to be valid when compared to the reference value. A set of recommendations and actions were agreed with the remaining participants.
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Final Report
. Note that this text is that which appears in Appendix B of the BIPM key comparison database
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The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
The long held but challenged view that plants do not synthesize sialic acids was re-evaluated using two different procedures to isolate putative sialic acid containing material from plant tissues and ...cells. The extracts were reacted with 1,2-diamino-4,5-methylene dioxybenzene and the fluorescently labelled 2-keto sugar acids analysed by reversed phase and normal phase HPLC and by HPLC-electrospray tandem mass spectrometry. No N-glycolylneuraminic acid was found in the protein fraction from Arabidopsis thaliana MM2d cells. However, we did detect 3-deoxy-d-manno-octulosonic acid and trace amounts (3-18 pmol/g fresh weight) of a compound indistinguishable from N-acetylneuraminic acid by its retention time and its mass spectral fragmentation pattern. Thus, plant cells and tissues contain five orders of magnitude less sialic acid than mammalian tissues such as porcine liver. Similar or lower amounts of N-acetylneuraminic acid were detected in tobacco cells, mung bean sprouts, apple and banana. Yet even yeast and buffer blanks, when subjected to the same isolation procedures, apparently contained the equivalent of 5 pmol of sialic acid per gram of material. Thus, we conclude that it is not possible to demonstrate unequivocally that plants synthesize sialic acids because the amounts of these sugars detected in plant cells and tissues are so small that they may originate from extraneous contaminants.
Cystoid macular edema is a vision-threatening complication infrequently associated with hydroxychloroquine retinal toxicity. There are limited data on the best treatment for this pathology.
A ...retrospective case series is presented.
In this series, we present three cases of cystoid macular edema in patients with diagnosed hydroxychloroquine maculopathy successfully treated with intravitreal dexamethasone implantation.
Minimal literature has been published regarding the best management of cystoid macular edema related to hydroxychloroquine toxicity. Our case series suggests a possible new agent in the treatment of this rare occurrence.
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