Karin Jungnikl

Austrian Academy of Sciences

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Ingo Burgert

ETH Zurich

Heinz Amenitsch

Graz University of Technology

Barbara Sartori

Graz University of Technology

Peter Fratzl

Max Planck Institute of Colloids and Interfaces

Michael Rappolt

University of Leeds

P. Laggner

Austrian Academy of Sciences

G. Panaccione

Istituto Officina dei Materiali

I. Shyjumon

Austrian Academy of Sciences

Cristina Africh

Istituto Officina dei Materiali

Regina Ciancio

AREA Science Park

Cooperative Institutions

Istituto Officina dei Materiali

AREA Science Park

Elettra-Sincrotrone Trieste S.C.p.A.

Austrian Academy of Sciences

Max Planck Institute of Colloids and Interfaces

Graz University of Technology

Max Planck Society

National Research Council

Czech Academy of Sciences, Institute of Biophysics

Institute of Inorganic Chemistry of the Slovak Academy of Sciences

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Self Assembly of Mesoporous Materials in the Gas-Phase: An in situ SAD Study

Heinz Amenitsch Benedetta Marmiroli Fernando Cacho Nerin Barbara Sartori Karin Jungnikl

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NFFA : nanoscience foundries and fine analysis

Giulia Rossi Regina Ciancio Cristina Africh R. Gotter G. Panaccione

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Stress generation in the tension wood of poplar is based on the lateral swelling power of the G‐layer

The Plant Journal (2008)

Luna Goswami John Dunlop Karin Jungnikl Michaela Eder Notburga Gierlinger

The mechanism of active stress generation in tension wood is still not fully understood. To characterize the functional interdependency between the G-layer and the secondary cell wall, nanostructural characterization and mechanical tests were performed on native tension wood tissues of poplar (Populus nigra x Populus deltoids) and on tissues in which the G-layer was removed by an enzymatic treatment. In addition to the well-known axial orientation of the cellulose fibrils in the G-layer, it was shown that the microfibril angle of the S2-layer was very large (about 36 degrees). The removal of the G-layer resulted in an axial extension and a tangential contraction of the tissues. The tensile stress-strain curves of native tension wood slices showed a jagged appearance after yield that could not be seen in the enzyme-treated samples. The behaviour of the native tissue was modelled by assuming that cells deform elastically up to a critical strain at which the G-layer slips, causing a drop in stress. The results suggest that tensile stresses in poplar are generated in the living plant by a lateral swelling of the G-layer which forces the surrounding secondary cell wall to contract in the axial direction.

Tension (geology)

Microfibril

Necking

10.1111/j.1365-313x.2008.03617.x

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Citations (100)

A comprehensive analysis of the relation of cellulose microfibril orientation and lignin content in the S2 layer of different tissue types of spruce wood (Picea abies (L.) Karst.)

Holzforschung (2008)

Karin Jungnikl Gerald Koch Ingo Burgert

Abstract A possible relation between cellulose microfibril angle and lignin content in the S2 layer was investigated by X-ray diffraction and cellular UV microspectrophotometry on spruce tissues [ Picea abies ] with different structural features and chemical composition. A strong correlation was not found, neither for the individual tissue types nor for the compiled data of all tissues. As the data did not confirm the findings in former studies, further examinations are necessary concerning a possible general interrelation between microfibril angle and lignin content.

Microfibril

Softwood

Suberin

10.1515/hf.2008.079

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Aerosol Flow Reactor with Controlled Temperature Gradient forIn SituGas-Phase X-Ray Experiments—Measurements of Evaporation-Induced Self-Assembly (EISA) in Aerosols

Aerosol Science and Technology (2011)

Karin Jungnikl Michael Rappolt I. Shyjumon Barbara Sartori P. Laggner

We present a new in situ aerosol flow reactor for gas-phase studies during drying of aerosol droplets by small-angle X-ray scattering (SAXS). The setup consists of an outer confinement shell and an inner tube for aerosol flow that can be positioned by a remote-controlled motor to perform scanning measurements along the flow path, providing “quasi-time-resolved” information on the drying process. A controlled temperature step is provided by an insulating separation between a cooled and a heated section in the dryer. First experiments were performed on aerosols of surfactant- and silica-precursor/surfactant solutions (CTAB/ethanol, TEOS/CTAB). Measurements of the mesostructure formation during the initial steps of evaporation-induced self-assembly (EISA) were made to illustrate the working principle of aerosol drying during passage through an adjustable temperature gradient.

Temperature Gradient

Small-angle X-ray scattering

10.1080/02786826.2011.564680

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Citations (6)

NFFA - Nanoscience Foundries and Fine Analysis - A EUROPEAN OPEN-ACCESS DISTRIBUTED RESEARCH INFRASTRUCTURE FOR NANOSCIENCE AND ADVANCED ANALYSIS

Zenodo (CERN European Organization for Nuclear Research) (2020)

Cristina Africh Heinz Amenitsch Graham G. Arthur Fernando Cacho‐Nerin Regina Ciancio

10.5281/zenodo.3613564

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Adaptive Growth of Gymnosperm Branches-Ultrastructural and Micromechanical Examinations

Journal of Plant Growth Regulation (2004)

Ingo Burgert Karin Jungnikl

Gymnosperm

Tracheid

Plant Physiology

Microfibril

10.1007/s00344-004-0042-2

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Citations (22)

The implication of chemical extraction treatments on the cell wall nanostructure of softwood

Cellulose (2007)

Karin Jungnikl Oskar Paris Peter Fratzl Ingo Burgert

Spruce wood was subjected to well-defined extraction treatments with sodium chlorite (NaClO2) for delignification, as well as with sodium hydroxide (NaOH) at different concentrations for extraction of hemicelluloses. The corresponding changes of the macromolecular polymer assembly were investigated by small-angle X-ray scattering (SAXS). Measurements with Fourier-transform infrared (FTIR) spectroscopy and wide-angle scattering (WAXS) gave qualitative information about the effectiveness of the extraction process, while the scattering experiments provided information about the regularity and typical dimensions of the molecular structures. The scattering data indicated that delignification had only a moderate effect on the structural organisation of the cell wall, while further extraction with NaOH induced considerable nanostructural changes.

Small-angle X-ray scattering

Sodium hydroxide

Softwood

Sodium chlorite

10.1007/s10570-007-9181-5

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Citations (75)

A close-up view of wood structure and properties across a growth ring of Norway spruce (Picea abies [L] Karst.)

Trees (2008)

Michaela Eder Karin Jungnikl Ingo Burgert

A growth ring of an adult Norway spruce (Picea abies [L] Karst.) was analyzed to a high resolution at the single cell level with respect to structural and mechanical changes during the growth period. For this purpose structural characterization was performed by means of light microscopy, scanning electron microscopy and wide angle X-ray diffraction for investigating the geometry of cells, their cell wall fractions and cellulose microfibril angles (MFA). The mechanical properties were determined in microtensile tests on individual tracheids which had been taken from sequentially cut tangential slices. The results revealed pronounced differences in tensile stiffness between earlywood and latewood cells but only minor differences in tensile stiffness between the cell walls of both tissue types. These comparatively small changes in cell wall stiffness across the growth ring were caused by slight changes in MFA. The findings suggest that trees mainly vary cell size to optimize water transport and mechanical stability during the growth period and that modification of the cell wall organisation plays a minor role.

Tracheid

Microfibril

Softwood

Secondary cell wall

10.1007/s00468-008-0256-1

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Citations (72)

The role of material properties for the mechanical adaptation at branch junctions

Trees (2008)

Karin Jungnikl Jürgen Goebbels Ingo Burgert Peter Fratzl

Branch junctions are mechanically particularly interesting areas of trees, because they have to withstand a combination of static and dynamic loads, from the stem as well as from the branch. In the present work, the local adaptation of material properties at branch junctions was assessed by mapping microfibril angle and tissue density. Images of the density distribution were obtained by computer tomography (CT). Wide angle X-ray scattering (WAXS) was used to determine the microfibril angle distribution with high-resolution around the junctions. The stem tissue around the junctions showed increased density and microfibril angle, which points towards an optimisation for fracture toughness. The tissue at the branch bases showed low density combined with high MFA, which provides deformability and flexibility and might act as protection of the stem against load transmission from the branch.

Microfibril

Morphing

10.1007/s00468-008-0305-9

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Citations (43)