59 research outputs found
Hepatitis C virus as cause of fulminant hepatitis-sequence analysis of the 5’ nontranslated region
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A fiber-based beam profiler for high-power laser beams in confined spaces and ultra-high vacuum
Laser beam profilometry is an important scientific task with well-established
solutions for beams propagating in air. It has, however, remained an open
challenge to measure beam profiles of high-power lasers in ultra-high vacuum
and in tightly confined spaces. Here we present a novel scheme that uses a
single multi-mode fiber to scatter light and guide it to a detector. The method
competes well with commercial systems in position resolution, can reach through
apertures smaller than ~m and is compatible with
ultra-high vacuum conditions. The scheme is simple, compact, reliable and can
withstand laser intensities beyond 2~MW/cm
Differential Polarization Imaging of Plant Cells. Mapping the Anisotropy of Cell Walls and Chloroplasts
Modern light microscopy imaging techniques have substantially advanced our knowledge about the ultrastructure of plant cells and their organelles. Laser-scanning microscopy and digital light microscopy imaging techniques, in general-in addition to their high sensitivity, fast data acquisition, and great versatility of 2D-4D image analyses-also opened the technical possibilities to combine microscopy imaging with spectroscopic measurements. In this review, we focus our attention on differential polarization (DP) imaging techniques and on their applications on plant cell walls and chloroplasts, and show how these techniques provided unique and quantitative information on the anisotropic molecular organization of plant cell constituents: (i) We briefly describe how laser-scanning microscopes (LSMs) and the enhanced-resolution Re-scan Confocal Microscope (RCM of Confocal.nl Ltd. Amsterdam, Netherlands) can be equipped with DP attachments-making them capable of measuring different polarization spectroscopy parameters, parallel with the 'conventional' intensity imaging. (ii) We show examples of different faces of the strong anisotropic molecular organization of chloroplast thylakoid membranes. (iii) We illustrate the use of DP imaging of cell walls from a variety of wood samples and demonstrate the use of quantitative analysis. (iv) Finally, we outline the perspectives of further technical developments of micro-spectropolarimetry imaging and its use in plant cell studies
Imaging FTIR microscopy – technique for rapid screening of plant cell walls
It has been shown that xylan is oriented in parallel to the cellulose and more or less parallel to the
axis of a cell wall, in isolated CW fragments from maize leaves. There was also a clear indication of
lignin orientation parallel to the longitudinal CW axis. This means that all of these components show
strong anisotropic behaviour and organisation
Serbian spruce (Picea omorika (Pančić) Purkyné) - endemicity and advantages
Conifers, as a response to mechanical stress, such as wind and stem lean, form
reaction wood called compression wood (CW). CW occurs in a range of gradations
from near normal wood (NW) to severe CW (SCW). As the severity of
CW affects the mechanical and chemical properties of wood, and as CW has
limited value in the forest products industry, it is desirable to be able to measure
CW severity. Picea omorika belong to slow-growing conifer species in
which CW typically occurs in a severe form. We developed different morphometric
and non-morphometric methods for estimation of CW severity tested
on wood samples of P. omorika juvenile trees exposed to long term static
bending. This specific review is aimed at presenting P. omorika as one of the
most adaptable spruces, and as a good model for testing of methods for estimation
of compression wood severity. First, we summarize main knowledge
about P. omorika, features of CW, and methods for assessment of wood quality.
Then, we present breifly our recently published methods for estimation
of compression wood severity tested on P. omorika juvenile wood samples.Konifere kao odgovor na mehanički stres (vetar, savijanje) formiraju reakciono
drvo koje se naziva kompresiono drvo (CW). CW se javlja u nizu
gradacija od skoro normalnog drveta (NW) do jako izraženog CW (SCW).
S obzirom da stepen izraženosti osobina CW ima značajan uticaj na
mehaničke i hemijske osobine drveta i da CW ima ograničenu vrednost za
drvnu industriju, poželjno je moći odrediti stepen izraženosti osobina CW
u uzorku. Picea omorika spada u sporo rastuće četinarske vrste kod kojih se
CW tipočno javlja u jako izraženoj formi. Mi smo razvili nekoliko morfometrijskih
i ne-morfometrijskih metoda za procenu izraženosti osobina CW
u uzorku, testiranih na uzorcima drveta juvenilnih stabala P. omorika koja
su bila izložena dugotajnom statičkom savijanju. Ovaj revijski rad ima za
cilj da predstavi Pančićevu omoriku kao jednu od najadaptabilnijih smrča i
kao dobar model za testiranje metoda za procenu izraženosti osobina CW u
uzorku. U prvom delu sumiramo znanja o Pančićevoj omorici, osobinama
CW i metodama za procenu kvaliteta drveta, a u drugom ukratko predstavljamo
naše nedavno objavljene metode za za procenu izraženosti osobina
CW u uzorku, testirane na uzorcima drveta juvenilnih stabala P. omorika
Serbian spruce, endemicity and advantages
Picea omorika (Pančić) Purkynĕ is Balkan endemic coniferous species and
Tertiary relict of the European flora. Its natural habitat is fragmented and reduced to
the middle and upper courses of the Drina River, in Western Serbia and Eastern
Bosnia and Herzegovina. This region represents species long-term, cryptic and last
refugium. The current limited natural range of Serbian spruce is mainly the result of
the species poor competing ability. It retreats to areas less inhabitable by its
competitors, predominantly Picea abies and Fagus orientalis. It inhabits open
habitats, comprising cliffs and forest clearings, characterized by strong northerlywind,
snow and rockfalls. Since the middle of the 19th century, its natural range declines
continuously. Planting Serbian spruce outside its natural range has a long tradition,
either as an ornamental tree species, or for afforestation, throughout Central and
Northern Europe. Despite its endemism, P. omorika is considered as one of the most
adaptable spruces.
Wood properties are determined by cell arrangement, size and shape, and cell
wall structure and thickness. Conifers, as a response to mechanical stress, such as
wind and stem lean, form reaction wood called compression wood (CW). Its
formation occurs on the lower side of the leaning stem, resulting in eccentric growth.
Wood opposite to the CW in the same growth ring is termed opposite wood (OW),
while wood from growth rings that do not contain any CW is termed normal wood
(NW). CW is characterized by reduced tracheid length, rounder cell cross-sectional
profile, presence of intercellular spaces, absence of the S3 cell wall layer and presence
of helical cavities in S2 layer. Higher lignification, as one of the main characteristics
of CW, is associated with changed lignin composition, increased amounts of phydroxyphenyl monomers and increased condensation of monomer units in the
polymer. Consequently, CW contains less cellulose, with greatly increased amounts
of galactan, and slightly lower amounts of mannan and xylan, and with higher angle
of cellulose microfibrils in the S2 layer of the cell wall, compared to NW.
CW occurs in a range of gradations from near NW to severe CW (SCW), mild
CW (MCW) forming a continuum between NW and SCW. The degree of
development of particular features of CW does not necessarily change in parallel to
each other, so the severity of a given tracheid is represented as a function of the
degrees of development of individual features, mainly lignification, helical cavities
and cell wall thickness. Visual detection of compression wood severity, more
precisely the determination of MCW, is difficult. As the severity of CW affects
mechanical and chemical properties of wood in forest products industry it is desirable
to be able to measure CW severity.
We developed different morphometric and non-morphometric methods for
distinguishing wood samples on a compression severity scale. They are based on
tracheid double wall thickness, cellulose microfibrils order (distribution and
alignment of cellulose microfibrils), or variation in lignin structure. We used confocal
fluorescence microscopy and spectroscopy, and fluorescence-detected linear
dichroism (FDLD) microscopy, combined with development of new algorithms and
statistical analysis. We tested our methods on stem samples of P. omorika juvenile
trees exposed to long term static bending. P. omorika belongs to slow-growing conifer
species in which CW typically occurs in a severe form, while juvenile conifer wood
is characterized by randomly distributed MCW, NW often being absent. These are the
features that suggest P. omorika juvenile wood a good choice of samples for
evaluation of the precision of methods suggested for estimation of compression wood
severity.
Our methods for distinguishing wood samples on a compression severity scale
provide a fine gradation of juvenile P. omorika wood samples from NW to the severest
form of CW, compression severity scales being partially different. The presented
results qualify our methods for use in estimation of compression wood severity in
forest products industries, individually or in combination, and confirm juvenile P.
omorika stem samples as a good choice of samples for evaluation of the precision of
methods suggested for compression wood severity estimation
The use of fluorescence microscopy for classification of pollen grains
In this pilot research, we showed that pollen autofluorescence varied between the pollen of the
different botanical species. Our findings suggest that classification of pollen grains may be obtained
based on their fluorescence images
Bragg diffraction of large organic molecules
We demonstrate Bragg diffraction of the antibiotic ciprofloxacin and the dye
molecule phthalocyanine at a thick optical grating. The observed patterns show
a single dominant diffraction order with the expected dependence on the
incidence angle as well as oscillating population transfer between the
undiffracted and diffracted beams. We achieve an equal-amplitude splitting of
(photon momenta) and maximum momentum transfer of .
This paves the way for efficient, large-momentum beam splitters and mirrors for
hot and complex molecules.Comment: 8 pages, 7 figures (including Supplemental Material). Corrected
errors in bibliograph
Mehanički stres i drvenaste biljke
Целулоза, лигнин и хемицелулозе су главне компоненте ћелијског зида које су комплексно повезане. Начин на који су ови полимери дрвета спрегнути међусобно и њихове особине утичу на својства влакана и дрвета, па је разумевање интеракција између ових полимера важно за разумевање механичких својстава дрвета, као одговора биљке на стрес, али такође и као могућу употребу дрвета као извора нових биоматеријала. Ћелијски зид се састоји од примарног зида (P), спољашњег секундарног зида (S1), средњег секундарног зида (S2) и унутрашњег секундарног зида (S3). У ћелијском зиду су доминантне особине S2 слоја јер он чини 80% укупне масе ћелијског зида. Целулоза је релативно паралелно оријентисана у односу на осу ћелијског зида што даје механичку снагу ћелијском зиду.1,2 Главна разлика између хемицелулозе тврдог и меког дрвета је у садржају ксилана и глукоманана. Постоје разлике и у лигнинским мономерним прекурсорима у ћелијским зидовима ове две врсте дрвета. Лигнин у меком дрвету садржи јединице гвајакола, док лигнин у тврдом дрвету садржи и гвајакол и сирингил мономере.3 Већина истраживања која се односе на оријентацију су фокусирана само на оријентацију целулозних микрофибрила. Међутим, организација преосталих полимера дрвета је од значаја код разумевања формирања ћелијског зида током раста. Анизотропију односно структурну уређеност ћелијског зида проучавали смо применом диференцијално поларизоване флуоресцентне микроскопије, као и применом ФТИР микро-спектроскопије
FTIR analysis of xylem vessel cell walls in twining stem of Dioscorea balcanica
Using stem cross sections of Dioscorea balcanica, as a model, we detected changes in anatomy and structural organization of xylem vessel cell walls (CWs) linked to stem twining in liana plants. UV microscopy, scanning electron microscopy and Fourier transform infrared (FTIR) microspectrometry were used. Different microfibrils orientation in vessel CWs of twisted compared to straight internodes, revealed by histological examination, coincide with the lower lignin content, the lower amount of xylan and cellulose, and the higher amount of xyloglucan, showed by FTIR. Xylem vessels resist high mechanical strain developed in twisted internodes by decreased CW rigidity (lower lignin content) and extensibility (higher xyloglucan content), and increased elasticity (lower xylan content)
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