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Two fluorinated isothiocyanato nematic liquid crystalline compounds, 4′-butylcyclohexyl-3, 5-difluoro-4-isothiocyanatobiphenyl and 4′-pentylcyclohexyl-3, 5-difluoro-4-isothiocynatobiphenyl are studied in detail to obtain their different physical parameters. Optical polarizing microscopy, differential scanning calorimetry, density and dielectric studies have been carried out for the two samples. Both the samples were found to have high clearing temperature (>100 °C) and exhibit small enthalpy of transition. The two samples exhibit high optical birefringence (Δ n > 0.2). The values of order parameters for the two samples were obtained using different approaches, namely, Vuks', Neugebauer's, modified Vuks' and direct extrapolation method from birefringence data. Experimentally obtained values of order parameters have also been compared with theoretical Maier-Saupe values. The parallel and perpendicular components of dielectric permittivity values of the two compounds were also calculated and their anisotropy values were found to be small. The effect of temperature on the molecular dipole moment μ and the angle of inclination β of the dipole axis with the director have also been investigated in this work. [ABSTRACT FROM AUTHOR]

Composites were prepared by inserting Single-Walled Carbon Nanotubes (SWCNTs) in the Nematic Liquid Crystal (NLC) to fasten the reorientation dynamics of the system under the electric field. Dispersion of SWCNTs in NLC medium enhanced the orientational order and consequently the display parameters of composite systems improved. Various display parameters such as orientational order, dielectric anisotropy, threshold voltage and splay elastic constant were explored for pure and composite systems. [ABSTRACT FROM AUTHOR]

Frequency- and temperature-dependent dielectric and switching parameters of a room temperature tri-component antiferroelectric liquid crystal mixture W-287 have been determined. Dielectric, optical texture and thermodynamic studies show wide room temperature range antiferroelectric SmC*a(˜91.1°C to <–25°C) phase in addition to high temperature paraelectric SmA* (˜2.6°C) and ferroelectric SmC* (˜4.4°C) phases. The dielectric studies carried out in the frequency range of 1–35 MHz under planar anchoring condition of the molecules show five different relaxation modes appearing in the SmA*, SmC* and SmC*aphases. Using Curie–Weiss law fit, ferroelectric SmC* to paraelectric SmA* transition temperature has been found to be 91.8°C. The dielectric response of SmC*aphase exhibits unusually three relaxation modes due to collective as well as individual molecular processes in addition to phason mode in the SmC* phase and amplitudon mode in the SmA* phase. Spontaneous polarisation, switching time and rotational viscosity have also been determined. The maximum value of PSis ˜300 nC/cm2, whereas viscosity is moderate. Switching time is of the order of few milli seconds. [ABSTRACT FROM AUTHOR]

In this article, optical properties of four fluoro-substituted 4-propyl-4′-[(4-ethylphenyl)ethynyl] biphenyls and liquid crystal mixture A are presented in the terahertz (THz) range. Birefringence, refractive indices and absorption coefficients for ordinary and extraordinary ray of liquid crystals are described in the range of 0.3 to 3.0 THz. It shows that the measured parameters are dependent on the number and placement of fluorine atoms in the molecules. Measurements have been performed using time-pulsed spectroscopy. [ABSTRACT FROM AUTHOR]

Highlights: [•] ZnO microflower grown by nanospikes/nanocapsules with nanorods/nanoflakes using hydrazine hydrate and CTAB. [•] Well crystalline structure of liquid crystal doped ZnO nanomaterials. [•] 1-dimensional nanoflakes in hydrothermal process and doped W-182 AFLC were tailored porous structure. [•] Higher temperature and CTAB surfactant easy to transform nanospikes to nanoflakes. [•] The optical and dielectric behavior drastically changes with those different nanostructures and doped with AFLC. [ABSTRACT FROM AUTHOR]

Abstract: We successfully synthesized nanocabbage like structures of TiO2 with diameter around 42nm after annealing the anatase TiO2 nanowires of diameter around 1.5nm. We obtained an interesting photoluminescence and dielectric behavior of nanocabbage doped W-182 antiferroelectric liquid crystal (AFLC). We observed a blue shift of photoluminescence spectra by 3nm for TiO2 nanocabbage doped AFLC in comparison to TiO2 nanowire doped AFLC. Significantly, we observed a single relaxation of mixed nanostructures. Due to the doping of AFLC in TiO2 nanowires and nanocabbages, dc conductivity was decreased remarkably in comparison to pure TiO2 nanocabbages. The threshold voltage was increased to 2V and 4V due to the doping of TiO2 nanowires and TiO2 nanocabbages in AFLC, respectively. [Copyright &y& Elsevier]

Abstract: We observed microsecond order response ranging from 100 to 600μs with respect to temperature for a single component fluorinated rigid core antiferroelectric liquid crystals having highly tilted phases. In the antiferroelectric region, we observed V-shaped electro-optic switching in a 4 μm indium tin oxide coated homogeneously aligned cell having PS, ranging from 100 to 200nC/cm2. Dielectric studies have revealed an interesting phase that exists during heating in the temperature region between 74°C and 84°C. From dielectric results studied we calculated activation energies associated with different relaxation modes using Arrhenius law. [Copyright &y& Elsevier]

The advancement on ferroelectric liquid crystals and their novel appliance is just changing from being largely focused on display devices and fast optical shutter elements to several other fields such as spatial light modulator, optical sensor, polarisation grating, photonic and optical devices. In the present work, we report the thermodynamical, textural, electrical and switching behaviour of a highly tilted FLC material. The studies have been performed on a 5 μm thick planar oriented sample. The above material possess cholesteric (N*), chiral smectic C* (SmC*) and hexatic (SmB*) phases in cooling cycle as confirmed by optical, thermodynamic and dielectric studies. The spontaneous polarisation is highly temperature dependent and increases while cooling in the SmC* phase. The maximum value of spontaneous polarisation is ∼117 nC cm−2 at 76 °C. The switching time is of the order of a few milli seconds (∼1.3 ms). The conductivity (ionic and dipolar both) of the material has also been determined in all the above exhibited phases. [Display omitted] • Electro optical and dielectric assets of a highly tilted FLC material are reported. • The material possess cholesteric, smectic C* and smectic B* hex phases. • Three different relaxation modes show different characteristics of mesophases. • Spontaneous polarisation, viscosity and switching time have been determined. • Various parameters suggest it to be appropriate base material for EO devices. [ABSTRACT FROM AUTHOR]

Abstract: We report the electro-optical properties of liquid crystal cells containing pure nitrile–ester mixture liquid crystal (NEMLC) and its doped form with 0.05% (wt/wt) single-wall carbon nanotubes (SWCNT). Diffraction efficiencies of 441-nm pump and 632-nm probe beams were measured in two-wave mixing experiment. Efficiencies and rise time were found to increase in SWCNT doped nematic liquid crystals. A maximum diffraction efficiency of ∼15% was found for cell doped with SWCNT, while cells without SWCNT had a maximum efficiency of 7%. We also have observed that photoconductivity in SWCNT doped liquid crystals is highly dependent on the light intensity. This is attributed to the doping, which enhances the efficient photo-charge generation, combined with enlarged conductivity. [Copyright &y& Elsevier]

Abstract: The dielectric properties of the antiferroelectric liquid crystal (AFLC) have been investigated under different confined geometries. The measurements of dielectric permittivities have been carried out in the frequency region from 10 Hz to 13 MHz in two planar aligned cells of thickness 2 μm and 10 μm, as well as in an Anopore membrane having pore diameter 0.2 μm and thickness 60 μm. In SmC⁎ phase the Goldstone mode (GM) has been observed in both the 10 μm and 2 μm planar aligned cells. Dielectric strength of GM is significantly diminished whereas the relaxation frequency is increased in the 2 μm thick cell compared to that in the 10 μm thick cell. In SmC⁎ A phase two antiferroelectric modes have been observed in two distinct frequency regions. In the lower frequency region below the Goldstone mode process another relaxation process is observed in both cells that arise due to the non-homogenous distribution of thermally generated ionic charges. The Goldstone mode present in planar aligned cells is not observed when the sample is confined in an anopore membrane. But two other modes are observed in the Anopore membrane. One is due to molecular reorientation around the short axis is usually observed in the quasi-homeotropic orientation of tilted smectics. The other mode is related to the internal curved surface of the anopore membrane. The results have been discussed. [Copyright &y& Elsevier]

The effect of Iron Oxide Nanoparticles (γ -Fe 2 O 3 NPs) on a room temperature nematic liquid crystalline material namely 4-(4′-hexylcyclohexyl) isothiocyanatobenzene (6CHBT) has been studied. The ferronematic composites have been characterized using differential scanning calorimetry, polarizing optical microscopy, dielectric spectroscopy and electro-optical measurements. It is found that the ferronematic with the low concentration of γ -Fe 2 O 3 NPs enhanced the orientational ordering of nematic matrix due to the strong orientational coupling between magnetic dipole moments associated to nanoparticles and nematic liquid crystal director, which is the essential feature of these systems. It resulted the improvement of various parameters of liquid crystals important for the application. In the ferronematics, the nematic to isotropic transition temperature increased as compared to that of the pure material. Dielectric spectroscopy has shown an increase of dielectric anisotropy in the composite systems. Electro-optical results reveal a decrement in both the splay elastic constant and the electric threshold voltage, in line with a noteworthy improvement of the steepness of transmission- voltage curves. Unlabelled Image • Composites of γ -Fe 2 O 3 NPs with a LC material have been prepared. • Thermal, optical, dielectric and electro-optical studies have been carried out. • Nematic-isotropic transition temperature increased due to the dispersion of NPs. • Dielectric anisotropy has also increased after the dispersion of γ-Fe 2 O3 NPs. • Presence of NPs reduced the splay elastic constant and threshold voltage. [ABSTRACT FROM AUTHOR]

Gold nanorods (GNRs) have a capsule-like structure with different optical properties than spherical gold nanoparticles due to surface plasmon resonance. Liquid crystals (LCs) are mesogenic compounds having crystal-like orientation and liquid-like fluidity. They are important materials from a technological point of view. Both GNRs and LC compounds are anisotropic in shape and properties. Different nano entities show interesting results when dispersed in different liquid crystalline materials which are instrumental from the application point of view. In the present work, GNRs have been dispersed in nematic liquid crystalline materials, namely 4-( trans -4- n -hexylcyclohexyl) isothiocyanatobenzene (6CHBT). Calorimetric, texture, spectroscopic, and dielectric studies were carried out for a pure 6CHBT and its composites with GNRs. Different calorimetric and dielectric parameters such as transition temperature, enthalpy, heat flow, permittivity, dielectric strength, dielectric anisotropy, and relaxation frequency have been determined, and the effect of GNRs has been explored. This article gives an insight into the influence of GNRs on the morphology and anisotropic physical properties of the nematic liquid crystalline material., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

For recent applications, liquid crystal-carbon nanotube based nanocomposite systems have been proven to be highly attractive. In this paper, we give a thorough analysis of a nanocomposite system made of both functionalized and nonfunctionalized multiwalled carbon nanotubes that are disseminated in a 4'-octyl-4-cyano-biphenyl liquid crystal medium. Thermodynamic study reveals a decrease in the nanocomposites' transition temperatures. In contrast to nonfunctionalized multiwalled carbon nanotube dispersed systems, the enthalpy of functionalized multiwalled carbon nanotube dispersed systems has increased. In comparison to the pure sample, the dispersed nanocomposites have a smaller optical band gap. A rise in the longitudinal component of permittivity and, consequently, the dielectric anisotropy of the dispersed nanocomposites has been observed by dielectric studies. When compared to the pure sample, the conductivity of both dispersed nanocomposite materials has increased by two orders of magnitude. For the system with dispersed functionalized multiwalled carbon nanotubes, the threshold voltage, splay elastic constant, and rotational viscosity all decreased. For the dispersed nanocomposite of nonfunctionalized multiwalled carbon nanotubes, the value of the threshold voltage is somewhat decreased but the rotational viscosity and splay elastic constant both are enhanced. These findings show the applicability of the liquid crystal nanocomposites for display and electro-optical systems with appropriate tuning of the parameters.

We investigate the role of competing nonlinear responses in the formation and propagation of bright spatial solitons. We use nematic liquid crystals (NLCs) exhibiting both thermo-optic and reorientational nonlinearities with continuous-wave beams. In a suitably prepared dye-doped sample and dual beam collinear geometry, thermal heating in the visible affects reorientational self-focusing in the near infrared, altering light propagation and self-trapping.

We propose an electrically tunable phase shifter for terahertz frequencies. The device is based on a polymer stabilized liquid crystal which allows for a simple device geometry. The polymer stabilized liquid crystal enables continuous tuning of the introduced phase shift with only one pair of electrodes. By characterizing the device with terahertz time-domain spectroscopy we demonstrate a phase shift up to 2.5 terahertz, only slightly changed properties of the neat liquid crystal and significantly reduced response times.

Investigations on the voltage induced conductance switching behavior in the nematic liquid crystal-multiwalled carbon nanotube composite have performed. We have found that, the system formed electrical conduction pathways with increasing voltages. Anomalous conductance switching took place at a certain threshold voltage. Percolation threshold voltage depends on the frequencies of the measuring electric field. We have made an analogy between concentration dependent percolation and voltage induced percolation. A two dimensional (2D) renormalization model calculation reveals that if the CNTs form a 2D network then percolation threshold concentration (p(c)) should be 0.768. After careful analysis we have found that voltage analogy of percolation threshold concentration in our system is also very close to the above value. The connectivity exponent (beta) for 2D site percolation agrees well with our proposed voltage induced percolation connectivity exponent. Which gives a glimpse that voltage induced percolating network may forms a two dimensional network in this particular system.

A partially fluorinated terphenyl liquid crystal with low absorption in both mid-wave infrared (MWIR) and near IR regions is developed and its properties evaluated. This compound exhibits a nematic phase (although only about 2 °C), reasonably high birefringence (Δn~0.2), low visco-elastic coefficient, and modest dielectric anisotropy (Δε = -2.7). This compound serves as an important first example for future development of low-loss MWIR liquid crystals and devices.

The objective of the present study was to analyse the immune status of mares in the early stages of pregnancy and mares which experienced early embryonic death (EED). Forty-eight fertile purebred Arabian mares were used for the study. The mares were divided into two groups. Group I was the control group composed of 32 mares in the early stages of a normal pregnancy. Group II was composed of 12 mares which had experienced EED. In both groups, subpopulations of T lymphocytes containing CD2(+), CD4(+) and CD8(+) were characterized using flow cytometry. The percentages of CD3(+) lymphocytes (adding up the cells with CD4(+) and CD8(+) phenotypes) and of NK cells (subtracting CD3(+) cells from CD2(+) lymphocytes) calculated. Due to its suppressive effects on T lymphocytes during pregnancy, TGF-beta1 was determined using ELISA. The findings revealed that in mares with EED, the percentages of lymphocytes TCD2(+), TCD4(+), NK cells at EED, i.e. between days 14 and 21, were significantly higher compared to mares without EED. The changes in the CD4(+)/CD8(+) ratio were similar. In the EED group, this ratio significantly increased between the 96th hour and the 30th day after ovulation compared to mares without EED. Otherwise, serum levels of TGF-beta1 in the EED group were significantly lower than in the control group. The results show that mares which experienced an EED develop inflammatory reactions which activate Th1 cell immune responses., (Copyright 2010 Elsevier B.V. All rights reserved.)

Experimental investigations of microstructured fibers filled with liquid crystals (LCs) have so far been performed only by using host fibers made of the silica glass. In this paper, the host photonic crystal fiber (PCF) was made of the PBG08 high-refractive index glass (approximately 1.95) that is much higher than silica glass index (approximately 1.46) and also higher then both ordinary and extraordinary refractive indices of the majority of LCs. As a result, low-loss and index-guiding propagation is observed regardless of the LC molecules orientation. Attenuation of the host PCF was measured to be approximately 0.15 dB/cm and for the PCF infiltrated with 5CB LC was slightly higher (approximately 0.19 dB/cm), resulting in a significant reduction to approximately 0.04 dB/cm of the scattering losses caused by the LC. Moreover, an external transverse electric field applied to the effective photonic liquid crystal fiber (PLCF) allowed for continuous phase birefringence tuning from 0 to 2.10(-4).

The aim of the study was to assess changes in serum C-reactive protein (CRP), serum amyloid A component (SAA) and haptoglobin (Hp) concentrations in healthy bitches and in those with pyometra undergoing ovariohysterectomy, and to establish the usefulness of such determinations for monitoring the postoperative period. Our results indicate that CRP and SAA determinations serve to evaluate the severity of the inflammatory process in pyometra since the concentrations of these acute phase proteins were increased immediately after surgery and diminished thereafter. The CRP and SAA response was rapidly produced while Hp concentrations increased in a more gradual manner. Thus, postoperative concentrations of CRP and SAA provide valuable information on the subsidence of the inflammatory response during the uneventful postoperative period. Our findings also suggest that acute phase proteins might be useful diagnostic markers of early postoperative complications.

The rapid tourism development resulted in higher incidence of the diseases related to oxygen metabolism pathologies at high altitudes. On the other hand, the lack of ability of close monitoring of changes during oxygen breathing in these conditions still makes it a subject of high interest for clinical studies. It seems that the main problem in oxygen metabolism at high altitudes is the disorder of pulmonary oxygen diffusion. In this paper the authors present the current knowledge, based on available literature, about the high-altitude oxygen metabolism.

Linear and nonlinear dielectric measurements of liquid crystalline chiral isopentylcyanobiphenyl (5*CB) and n -pentylcyanobiphenyl (5CB), combined with viscosity eta (T) data, are presented. The 5*CB compound glassifies on cooling in the cholesteric phase whereas 5CB crystallizes in the nematic phase. In both compounds the temperature evolution of dielectric relaxation times, the dc conductivity, and the viscosity are well described by the "critical-like" description from mode coupling theory (MCT). However, for 5*CB a unique coincidence of the MCT "critical" temperature and extrapolated temperature of the hypothetical continuous isotropic-cholesteric (T*) phase transition was found. The temperature dependence of the strong electric-field-induced changes of the dielectric permittivity exhibits a strong anomaly in the direction of negative values on approaching T* , not observed up to now. The anomaly is described by the susceptibility-related critical exponent gamma=1 . The divergence of the "nonlinear" dielectric relaxation follows a power dependence described by the exponent y=1 . This paper recalls the recent discussions on the glassy dynamics of a "hard-ellipsoid" liquid and the possible relationship between the glass transition, critical phenomena, and isotropic-nematic transition.