Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, 1994
We investigated the temporal dependence of the second harmonic generation from a 50 μm thick home... more We investigated the temporal dependence of the second harmonic generation from a 50 μm thick homeotropically aligned cell of ferroelectric liquid crystal SCE9 (BDH Ltd.) exposed to a square waveform field varying between non zero and zero value. The field switches the molecular configuration between the efficient phase matching geometry and the inefficient helically modulated structure. The power of the
The transmission characteristics of the central core in seven-core fiber (7CF) are investigated b... more The transmission characteristics of the central core in seven-core fiber (7CF) are investigated both theoretically and experimentally. The 7CF is placed between two standard single-mode fibers (SMF), which forms a so-called S7S structure (SMF–7CF–SMF). From the simulation results it was found that the transmitted power through a S7S structure is highly sensitive to the wavelength of operation. The simulation results are supported by experimental measurements using three different measurement set-ups on spliced S7S structures. The transmission characteristics of the central core in the S7S structure were measured using an unpolarized broadband light source, unpolarized light from an erbium-doped fiber amplifier and polarized light from a tunable laser source. The results from this paper will be useful in the design of novel optical filters using S7S structures.
An appealing property of optical diffractive structures from elastomeric materials is a possibili... more An appealing property of optical diffractive structures from elastomeric materials is a possibility to regulate their optical patterns and consequently also their diffractive features with mechanical straining. We investigated the effect of strain on diffraction characteristics of holographic gratings recorded in a monodomain side-chain liquid crystalline elastomer. The strain was imposed either parallel or perpendicular to the initial alignment direction of the material. At temperatures far below the nematic–paranematic phase transition, straining along the initial alignment affects mainly the diffraction pattern, while the diffraction efficiency remains almost constant. In contrast, at temperatures close to the nematic–paranematic phase transition, the diffraction efficiency is also significantly affected. Straining in the direction perpendicular to the initial alignment strongly and diversely influences both the diffraction pattern and the diffraction efficiency. The difference b...
We investigated magnetic-field-induced modifications of the surface roughness of magnetoactive el... more We investigated magnetic-field-induced modifications of the surface roughness of magnetoactive elastomers (MAEs) with four material compositions incorporating two concentrations of ferromagnetic microparticles (70 wt% and 80 wt%) and exhibiting two shear storage moduli of the resulting composite material (about 10 kPa and 30 kPa). The analysis was primarily based on spread optical reflection measurements. The surfaces of all four materials were found to be very smooth in the absence of magnetic field (RMS roughness below 50 nm). A maximal field-induced roughness modification (approximately 1 μm/T) was observed for the softer material with the lower filler concentration, and a minimal modification (less than 50 nm/T) was observed for the harder material with the higher filler concentration. All four materials showed a significant decrease in the total optical reflectivity with an increasing magnetic field as well. This effect is attributed to the existence of a distinct surface layer...
Micropatterned substrates offer a unique possibility to define and control spatial organization o... more Micropatterned substrates offer a unique possibility to define and control spatial organization of biological cells at the microscale, which greatly facilitates investigations of the cell-to-cell communication in vitro. Here, we developed a simple micropatterning strategy to resolve various spatiotemporal characteristics of intercellular calcium wave (ICW) communication among isolated BV-2 microglial cells. By using a single-ring assembly, we found that the direction of the initial transmitter secretion was strongly correlated with the site of the cell at which the mechanical stimulus triggering the ICWs was imposed. By using multiring assemblies, we observed that the response ratio of the same outmost cells 160 μm away from the center increased from 0% in the single-ring assembly to 9.6% in the four-ring assembly. This revealed that cells located in the interring acted as regenerative amplifiers for the ICWs generated by the central cell. By using a special oval-type micropattern, ...
We develop a new method for smooth and continuous space-variant alignment of the liquid crystal m... more We develop a new method for smooth and continuous space-variant alignment of the liquid crystal medium in micro-patterned structures, which is based on a radial micro-structured pattern of polymeric ribbons exhibiting out-of-plane orientation with respect to the ITO-coated glass plates. Thanks to the broad range of electrical tunability of the optical retardation for the micro-patterned liquid crystal structures, transformation of the fundamental Gaussian beam into different types of specific beams, including generalized cylindrical vector beams, vortex beams, and vectorial vortex beams, is efficiently demonstrated.
Langmuir : the ACS journal of surfaces and colloids, Jan 20, 2015
We investigated the effect of various ions on the surface assembly of a guanosine derivative with... more We investigated the effect of various ions on the surface assembly of a guanosine derivative with one hexadecanoyl chain at the air-water interface. The ions were added to the water subphase prior to spreading of the surface film. Like in bulk water, also at the air-water interface, K(+) ions exhibit the strongest influence on the assembly features as they induce structural transformation from lamellar to mosaic-like assembly. In contrast, Li(+) and Na(+) ions only slightly modify the properties of the assembled film with respect to those observed on pure water. The nature of anions plays an important role in the surface self-assembly as well. We found that (Pic(-)) is 2 orders of magnitude more effective for assembly regulation than Cl(-). All surface assemblies observed in our study are very stable and robust, and consequently they remain practically unperturbed after Langmuir-Blodgett transfer onto a solid support.
We investigated quadruplex formation in aqueous solutions of 2'-deoxyriboguanosine 5'-mon... more We investigated quadruplex formation in aqueous solutions of 2'-deoxyriboguanosine 5'-monophosphate, d(pG), which takes place in the absence of the covalent axial backbone. A series of in-solution small angle X-ray scattering experiments on d(pG) have been performed as a function of temperature in the absence of excess salt, at a concentration just above the critical one at which self-assembling occurs. A global fit approach has been used to derive composition and size distribution of the scattering particles as a function of temperature. The obtained results give thermodynamical justification for the observed phase-behavior, indicating that octamer formation is essential for quadruplex elongation. Our investigation shows that d(pG) quadruplexes are very suitable to assess the potential of G-quadruplex formation and to study the self-assembling thermodynamics.
ABSTRACT We investigated the orientational distribution of MoS2 nanotubes incorporated into a com... more ABSTRACT We investigated the orientational distribution of MoS2 nanotubes incorporated into a commercial photo-reactive liquid crystalline medium. Electron microscopy imaging and Raman spectroscopy measurements show that interaction with the liquid crystalline host induces strong directional alignment of the nanotubes. The obtained alignment is “frozen” into the structure by subsequent photo-polymerization reaction, which on one hand prevents agglomeration and on the other hand produces a solid composite film with controlled orientation of the nanotubes. Analysis of the mechanical properties shows that by adding 0.1 wt% of the nanotubes the elastic modulus of the films is increased by 35%. Our results demonstrate that the nanotube alignment approach based on photo-polymerizable liquid crystalline media, which is relatively inefficient for carbon nanotubes, might be much more promising for inorganic nanotubes.
The formation and dimensions of G-wires by different short G-rich DNA sequences in solution were ... more The formation and dimensions of G-wires by different short G-rich DNA sequences in solution were investigated by dynamic light scattering (DLS) and polyacrilamide gel electrophoresis (PAGE). To explore the basic principles of wire formation, we studied the effects of base sequence, method of preparation, temperature, and oligonucleotide concentration. Both DLS and PAGE show that thermal annealing induces much less macromolecular self-assembly than dialysis. The degree of assembly and consequently length of G-wires (5-6 nm) are well resolved by both methods for DNA sequences with intermediate length, while some discrepancies appear for the shortest and longest sequences. As expected, the longest DNA sequence gives the longest macromolecular aggregates with a length of about 11 nm as estimated by DLS. The quadruplex topologies show no concentration dependence in the investigated DNA concentration range (0.1 mM–0.4 mM) and no structural change upon heating.
... for storage containers. The aim of this work was to investigate the MoS 2 nanotubes and narro... more ... for storage containers. The aim of this work was to investigate the MoS 2 nanotubes and narrow bundles decomposed from wide bundles, which generally show a strong tendency for self-or hetero-assembly. Typically, they are ...
Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, 1994
We investigated the temporal dependence of the second harmonic generation from a 50 μm thick home... more We investigated the temporal dependence of the second harmonic generation from a 50 μm thick homeotropically aligned cell of ferroelectric liquid crystal SCE9 (BDH Ltd.) exposed to a square waveform field varying between non zero and zero value. The field switches the molecular configuration between the efficient phase matching geometry and the inefficient helically modulated structure. The power of the
The transmission characteristics of the central core in seven-core fiber (7CF) are investigated b... more The transmission characteristics of the central core in seven-core fiber (7CF) are investigated both theoretically and experimentally. The 7CF is placed between two standard single-mode fibers (SMF), which forms a so-called S7S structure (SMF–7CF–SMF). From the simulation results it was found that the transmitted power through a S7S structure is highly sensitive to the wavelength of operation. The simulation results are supported by experimental measurements using three different measurement set-ups on spliced S7S structures. The transmission characteristics of the central core in the S7S structure were measured using an unpolarized broadband light source, unpolarized light from an erbium-doped fiber amplifier and polarized light from a tunable laser source. The results from this paper will be useful in the design of novel optical filters using S7S structures.
An appealing property of optical diffractive structures from elastomeric materials is a possibili... more An appealing property of optical diffractive structures from elastomeric materials is a possibility to regulate their optical patterns and consequently also their diffractive features with mechanical straining. We investigated the effect of strain on diffraction characteristics of holographic gratings recorded in a monodomain side-chain liquid crystalline elastomer. The strain was imposed either parallel or perpendicular to the initial alignment direction of the material. At temperatures far below the nematic–paranematic phase transition, straining along the initial alignment affects mainly the diffraction pattern, while the diffraction efficiency remains almost constant. In contrast, at temperatures close to the nematic–paranematic phase transition, the diffraction efficiency is also significantly affected. Straining in the direction perpendicular to the initial alignment strongly and diversely influences both the diffraction pattern and the diffraction efficiency. The difference b...
We investigated magnetic-field-induced modifications of the surface roughness of magnetoactive el... more We investigated magnetic-field-induced modifications of the surface roughness of magnetoactive elastomers (MAEs) with four material compositions incorporating two concentrations of ferromagnetic microparticles (70 wt% and 80 wt%) and exhibiting two shear storage moduli of the resulting composite material (about 10 kPa and 30 kPa). The analysis was primarily based on spread optical reflection measurements. The surfaces of all four materials were found to be very smooth in the absence of magnetic field (RMS roughness below 50 nm). A maximal field-induced roughness modification (approximately 1 μm/T) was observed for the softer material with the lower filler concentration, and a minimal modification (less than 50 nm/T) was observed for the harder material with the higher filler concentration. All four materials showed a significant decrease in the total optical reflectivity with an increasing magnetic field as well. This effect is attributed to the existence of a distinct surface layer...
Micropatterned substrates offer a unique possibility to define and control spatial organization o... more Micropatterned substrates offer a unique possibility to define and control spatial organization of biological cells at the microscale, which greatly facilitates investigations of the cell-to-cell communication in vitro. Here, we developed a simple micropatterning strategy to resolve various spatiotemporal characteristics of intercellular calcium wave (ICW) communication among isolated BV-2 microglial cells. By using a single-ring assembly, we found that the direction of the initial transmitter secretion was strongly correlated with the site of the cell at which the mechanical stimulus triggering the ICWs was imposed. By using multiring assemblies, we observed that the response ratio of the same outmost cells 160 μm away from the center increased from 0% in the single-ring assembly to 9.6% in the four-ring assembly. This revealed that cells located in the interring acted as regenerative amplifiers for the ICWs generated by the central cell. By using a special oval-type micropattern, ...
We develop a new method for smooth and continuous space-variant alignment of the liquid crystal m... more We develop a new method for smooth and continuous space-variant alignment of the liquid crystal medium in micro-patterned structures, which is based on a radial micro-structured pattern of polymeric ribbons exhibiting out-of-plane orientation with respect to the ITO-coated glass plates. Thanks to the broad range of electrical tunability of the optical retardation for the micro-patterned liquid crystal structures, transformation of the fundamental Gaussian beam into different types of specific beams, including generalized cylindrical vector beams, vortex beams, and vectorial vortex beams, is efficiently demonstrated.
Langmuir : the ACS journal of surfaces and colloids, Jan 20, 2015
We investigated the effect of various ions on the surface assembly of a guanosine derivative with... more We investigated the effect of various ions on the surface assembly of a guanosine derivative with one hexadecanoyl chain at the air-water interface. The ions were added to the water subphase prior to spreading of the surface film. Like in bulk water, also at the air-water interface, K(+) ions exhibit the strongest influence on the assembly features as they induce structural transformation from lamellar to mosaic-like assembly. In contrast, Li(+) and Na(+) ions only slightly modify the properties of the assembled film with respect to those observed on pure water. The nature of anions plays an important role in the surface self-assembly as well. We found that (Pic(-)) is 2 orders of magnitude more effective for assembly regulation than Cl(-). All surface assemblies observed in our study are very stable and robust, and consequently they remain practically unperturbed after Langmuir-Blodgett transfer onto a solid support.
We investigated quadruplex formation in aqueous solutions of 2'-deoxyriboguanosine 5'-mon... more We investigated quadruplex formation in aqueous solutions of 2'-deoxyriboguanosine 5'-monophosphate, d(pG), which takes place in the absence of the covalent axial backbone. A series of in-solution small angle X-ray scattering experiments on d(pG) have been performed as a function of temperature in the absence of excess salt, at a concentration just above the critical one at which self-assembling occurs. A global fit approach has been used to derive composition and size distribution of the scattering particles as a function of temperature. The obtained results give thermodynamical justification for the observed phase-behavior, indicating that octamer formation is essential for quadruplex elongation. Our investigation shows that d(pG) quadruplexes are very suitable to assess the potential of G-quadruplex formation and to study the self-assembling thermodynamics.
ABSTRACT We investigated the orientational distribution of MoS2 nanotubes incorporated into a com... more ABSTRACT We investigated the orientational distribution of MoS2 nanotubes incorporated into a commercial photo-reactive liquid crystalline medium. Electron microscopy imaging and Raman spectroscopy measurements show that interaction with the liquid crystalline host induces strong directional alignment of the nanotubes. The obtained alignment is “frozen” into the structure by subsequent photo-polymerization reaction, which on one hand prevents agglomeration and on the other hand produces a solid composite film with controlled orientation of the nanotubes. Analysis of the mechanical properties shows that by adding 0.1 wt% of the nanotubes the elastic modulus of the films is increased by 35%. Our results demonstrate that the nanotube alignment approach based on photo-polymerizable liquid crystalline media, which is relatively inefficient for carbon nanotubes, might be much more promising for inorganic nanotubes.
The formation and dimensions of G-wires by different short G-rich DNA sequences in solution were ... more The formation and dimensions of G-wires by different short G-rich DNA sequences in solution were investigated by dynamic light scattering (DLS) and polyacrilamide gel electrophoresis (PAGE). To explore the basic principles of wire formation, we studied the effects of base sequence, method of preparation, temperature, and oligonucleotide concentration. Both DLS and PAGE show that thermal annealing induces much less macromolecular self-assembly than dialysis. The degree of assembly and consequently length of G-wires (5-6 nm) are well resolved by both methods for DNA sequences with intermediate length, while some discrepancies appear for the shortest and longest sequences. As expected, the longest DNA sequence gives the longest macromolecular aggregates with a length of about 11 nm as estimated by DLS. The quadruplex topologies show no concentration dependence in the investigated DNA concentration range (0.1 mM–0.4 mM) and no structural change upon heating.
... for storage containers. The aim of this work was to investigate the MoS 2 nanotubes and narro... more ... for storage containers. The aim of this work was to investigate the MoS 2 nanotubes and narrow bundles decomposed from wide bundles, which generally show a strong tendency for self-or hetero-assembly. Typically, they are ...
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