Publications by authors named "Ewa Gorecka"

A material showing a sequence of three ferroelectric liquid crystalline phases below the paraelectric nematic phase is synthesized and studied. The polar order of molecules appearing due to the dipole-dipole interactions in the ferroelectric nematic, N, phase is preserved also in the smectic phases: orthogonal SmA and tilted SmC. The ferroelectric ground state of both smectic phases is confirmed by their second harmonic generation (SHG) activity and polarization switching.

View Article and Find Full Text PDF
Article Synopsis
  • - The study identifies a new diatom species from the highly alkaline Lake Van in Turkey, characterized through light and scanning electron microscopy on both wild and cultivated samples.
  • - Genome analysis revealed that the two monoclonal cultures have very similar DNA sequences with only a few mutations, particularly in the mitochondrial and plastid genomes, indicating some differences in protein coding genes.
  • - Phylogenetic analysis placed the new diatom species within the K clade, known for its diversity of species from hypersaline to freshwater environments.
View Article and Find Full Text PDF

The spontaneous polarisation of the SmC phase is over two orders of magnitude larger than that found in conventional ferroelectric SmC phase of chiral materials used in some LCD devices. Fully atomistic molecular dynamics simulations faithfully and spontaneously reproduce the proposed structure and associated bulk properties; comparison of experimental and simulated X-ray scattering patterns shows excellent agreement. The materials disclosed here have significantly smaller dipole moments than typical polar liquid crystals such as RM734 which suggests the role of molecular electrical polarity in generating polar order is perhaps overstated, a view supported by consideration of other molecular systems.

View Article and Find Full Text PDF

Until recently, the data on the diversity of the entire microbial community from the Baltic Sea were relatively rare and very scarce. However, modern molecular methods have provided new insights into this field with interesting results. They can be summarized as follows.

View Article and Find Full Text PDF

Spontaneous mirror symmetry breaking by formation of chiral structures from achiral building blocks and emergent polar order are phenomena rarely observed in fluids. Separately, they have both been found in certain nematic liquid crystalline phases; however, they have never been observed simultaneously. Here, we report a heliconical arrangement of achiral molecules in the ferroelectric nematic phase.

View Article and Find Full Text PDF

The current article describes , a new species of diatom from Lake Van, a highly alkaline lake in Eastern Anatolia (Türkiye). The description is based on light and scanning electron microscopy performed on two monoclonal cultures. The complete nuclear rRNA clusters and plastid genomes have been sequenced for these two strains and the complete mitogenome for one of them.

View Article and Find Full Text PDF

The syntheses and characterisation of the 4-[{[4-({n-[4-(4-cyanophenyl)phenyl]-n-yl}oxy)phenyl]-methylidene}amino]phenyl-4-alkoxybenzoates (CBnOIBeOm) are reported with n=8 and 10 and m=1-10. The two series display fascinating liquid crystal polymorphism. All twenty reported homologues display an enantiotropic nematic (N) phase at high temperature.

View Article and Find Full Text PDF

We report two new series of compounds that show the ferroelectric nematic, N, phase in which the terminal chain length is varied. The longer the terminal chain, the weaker the dipole-dipole interactions of the molecules are along the director and thus the lower the temperature at which the axially polar N phase is formed. For homologues of intermediate chain lengths, between the non-polar and ferroelectric nematic phases, a wide temperature range nematic phase emerges with antiferroelectric character.

View Article and Find Full Text PDF

A critical end point above which an isotropic phase continuously evolves into a polar (ferroelectric) nematic phase with an increasing electric field is found in a ferroelectric nematic liquid crystalline material. The critical end point is approximately 30 K above the zero-field transition temperature from the isotropic to nematic phase and at an electric field of the order of 10  V/μm. Such systems are interesting from the application point of view because a strong birefringence can be induced in a broad temperature range in an optically isotropic phase.

View Article and Find Full Text PDF

The front cover artwork is provided by Dr Rebecca Walker of the Liquid Crystals Group at the University of Aberdeen. The image is a cartoon depiction of the formation of the heliconical chiral twist-bend nematic phase (N* ) from its constituent bent molecules. The presence of a single enantiomer of the chiral, lactate-based liquid crystal dimers biases the formation of helices with only one handedness, unlike in the conventional N phase, observed for achiral molecules, for which the left- and right-handed helices are doubly degenerate.

View Article and Find Full Text PDF

We describe the fabrication of dual-responsive (thermo/light) chiral plasmonic films. The idea is based on using photoswitchable achiral liquid crystal (LCs) forming chiral nanotubes for templating helical assemblies of Au NPs. Circular dichroism spectroscopy (CD) confirms chiroptical properties coming from the arrangement of organic and inorganic components, with up to 0.

View Article and Find Full Text PDF

The synthesis and characterisation of two series of low molar mass mesogens, the (4-nitrophenyl) 2-alkoxy-4-(4-methoxybenzoyl)oxybenzoates (NT3.m) and the (3-fluoro-4-nitrophenyl) 2-alkoxy-4-(4-methoxybenzoyl)oxybenzoates (NT3F.m), are reported in order to investigate the effect of changing the position of a lateral alkoxy chain from the methoxy-substituted terminal ring to the central phenyl ring in these two series of materials based on RM734.

View Article and Find Full Text PDF

Non-symmetric lactate-based chiral liquid crystal dimers containing an odd-membered spacer are shown to exhibit a chiral twist-bend nematic phase which is stable on cooling to room temperature. A comparison of racemic and optically pure materials reveals that the pitch length in the N* phase is not influenced by molecular chirality, whereas the nematic-twist-bend nematic transition temperature is increased.

View Article and Find Full Text PDF

A resonant X-ray scattering response for two structural models of a chiral cubic phase with a giant unit cell, one composed of a continuous grid and micelles and the other with three continuous grids, is studied theoretically and compared to experimental measurements. For both structural models resonant enhancement of all the symmetry-allowed diffraction peaks is predicted, as well as the existance of several symmetry forbidden peaks (pure resonant peaks). Experimental measurements were performed at the carbon and sulphur absorption edge.

View Article and Find Full Text PDF

The synthesis and characterisation of the 1-(4-cyanobiphenyl-4'-yl)-10-(4-alkylanilinebenzylidene-4'-oxy)decanes (CB10O·) are reported. This series shows a rich liquid crystal polymorphism including twist-bend nematic and smectic phases. All the homologues reported exhibit an enantiotropic conventional nematic phase.

View Article and Find Full Text PDF

Liquid crystalline (LC) dimers formed helical nanofilaments depending on the parity of the alkyl linker, revealing an unusual odd-even effect. Molecular dynamics simulations were used to investigate the observed tendency. Elongation of the linker translates to an increase of the pitch of the helices, which allows achieving tuneable helical assemblies of Au nanoparticles doped to the LC matrix.

View Article and Find Full Text PDF

Janus-type structures were obtained from gold nanoparticles grafted with two types of chemically incompatible mesogenic ligands with a strong tendency for nano-segregation. A lamellar arrangement, in which metallic nanoparticle-rich sublayers are separated by organic ligand-rich sublayers of various composition, was formed due to the ligand segregation process. The layers could be easily aligned by mechanical shearing; for most materials the layer normal was parallel to the shearing direction but perpendicular to the shearing gradient, such transverse mode is only rarely observed for lamellar materials.

View Article and Find Full Text PDF

Mesogenic materials, quinoxaline derivatives with semi-flexible cores, are reported to form a new type of 3D columnar phase with a large crystallographic unit cell and lattice below the columnar hexagonal phase. The 3D columnar structure is a result of frustration imposed by the arrangement of helical columns of opposite chiralities into a triangular lattice. The studied materials exhibit fluorescence properties that could be easily tuned by modification of the molecular structure; for compounds with the extended π electron conjugated systems the fluorescence is quenched.

View Article and Find Full Text PDF

A photonic lattice is an efficient platform for optically exploring quantum phenomena. However, its fabrication requires high costs and complex procedures when conventional materials, such as silicon or metals, are used. Here, we demonstrate a simple and cost-effective fabrication method for a reconfigurable chiral photonic lattice of the helical nanofilament (HNF) liquid crystal (LC) phase and diffraction grating showing wavelength-dependent diffraction with a rotated polarization state.

View Article and Find Full Text PDF

We provide for the first time the complete plastid and mitochondrial genomes of a monoraphid diatom: The mitogenome is 41,957 bp in size and displays two group II introns in the gene. The 187,029 bp plastid genome features the typical quadripartite architecture of diatom genomes. It contains a group II intron in the gene that overlaps the large single-copy and the inverted repeat region.

View Article and Find Full Text PDF

Liquid-crystal materials exhibiting up to three nematic phases are reported. Dielectric response measurements show that while the lower temperature nematic phase has ferroelectric order and the highest temperature nematic phase is apolar, the intermediate phase has local antiferroelectric order. The modification of the molecular structure by increasing the number of lateral fluorine substituents leads to one of the materials showing a direct isotropic-ferronematic phase transition.

View Article and Find Full Text PDF

Achiral mesogenic molecules are shown to be able to spontaneously assemble into liquid crystalline smectic phases having either simple or double-helical structures. At the transition between these phases, the double-helical structure unwinds. As a consequence, in some temperature range, the pitch of the helix becomes comparable to the wavelength of visible light and the selective reflection of light in the visible range is observed.

View Article and Find Full Text PDF

Presented here are new insights into the marine monoraphid diatom genera Schizostauron and Astartiella, based on molecular and morphological data, including descriptions of new species. Although no unambiguous morphological synapomorphies between the two genera are currently recognized, they are closely related by DNA sequence data. Heterovalvate frustules of Schizostauron are characterized by a bifid stauros on the raphe-bearing valve and intricate areolate occlusions on the sternum valve.

View Article and Find Full Text PDF

A PHP Error was encountered

Severity: Notice

Message: fwrite(): Write of 34 bytes failed with errno=28 No space left on device

Filename: drivers/Session_files_driver.php

Line Number: 272

Backtrace:

A PHP Error was encountered

Severity: Warning

Message: session_write_close(): Failed to write session data using user defined save handler. (session.save_path: /var/lib/php/sessions)

Filename: Unknown

Line Number: 0

Backtrace: