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The method of widening of the blue phase (BP) temperature range is presented. By means of polarising optical microscopy, we demonstrate that the temperature regime in which BP is stable is greatly enhanced by the cell thickness changes in mixtures of nematic liquid crystal (LC) and chiral dopant. [ABSTRACT FROM AUTHOR]

The chiral smectic phases of two liquid crystals (LCs) were investigated, one of them is a high tilted, long pitch, near ortoconic LC mixture and the second exhibits broad temperature of thephase. For both materials second-harmonic electro-optic (EO) spectra were studied. The particular LC phases were characterised by a specific temperature dependence of the frequency at which the real part of the second-order electro-optic response (EOR) possesses an extremum (fext). The obtained values offext(correlated with the phase-type mode processes) were used to identify LC phases and temperature of phase transitions. The sensitivity of the used method allowed to identify theandphases for the studied materials, not detected before by DSC or dielectric measurements. [ABSTRACT FROM PUBLISHER]

Measurements of the non-linear electro-optical effects for the well-known prototype liquid crystal material (MHPOBC) are presented. The method to identify liquid crystalline phases and to determine temperatures of phase transitions based on the analysis of the second harmonic component of electro-optical response spectra is used. Applying that method, the values of the frequency () at which the second harmonic electro-optic response (EOR) possesses an extremum are determined for each smectic phase. We suggest that this characteristic frequency correspond to the phase-type mode processes. Furthermore, we show that the usually neglected results on heating can be useful in discussions of dynamical behaviour of second harmonic EOR in case of smectic phases. [ABSTRACT FROM PUBLISHER]

Background: The overall aim of this prospective, randomized study was to compare the reproductive potential of fresh and frozen-thawed ejaculated spermatozoa from oligoasthenoteratozoospermic patients in an intracytoplasmic sperm injection (ICSI) procedure.Methods: All patients consenting to participate in this study had a sperm sample frozen prior to the start of a cycle. Patients were randomized using a random number table to undergo ICSI with either fresh (group A, n = 118) or frozen-thawed (group B, n = 122) spermatozoa. All prognostic variables were equally distributed among the two groups.Results: The pregnancy rate per started cycle was 29.7% in group A and 38.5% in group B, P > 0.05. A significant difference was observed in the rate of ongoing pregnancies between group A (23.7%) and group B (35.2%), P < 0.05.Conclusion: From our data we can conclude that cryopreservation of spermatozoa from men with poor sperm quality does not negatively affect fertilization and pregnancy rates after ICSI. A larger study will be needed to investigate whether the use of cryopreserved spermatozoa can be helpful in selecting the most vital spermatozoa for ICSI. [ABSTRACT FROM AUTHOR]

Theoretical and experimental studies of the director distribution of a chiral nematic liquid crystal placed in a wedge-shaped cell with weak surface anchoring were performed. We measured local value of pitch as function of position inside each Grandjean-Cano zone by registering selective reflection spectra from narrow stripes cut from each Cano zone. We also measured the rotation of the polarisation plane as function of thickness of the wedge sample. These data allowed determination of the angle between the local director and the easy direction on the surface. The obtained director distributions in individual Cano zones were compared with the results of theory and thus used for restoration of the actual shape of the surface anchoring potential. [ABSTRACT FROM AUTHOR]

We present the results of the study of three fluorinated mesogens with three aromatic rings and different length of alkyl chain. The investigated substances might be of interest for using in technical devices. Calorimetric, dielectric and electro-optical properties were examined. Special attention was paid to the dependence of the first and second harmonics of the electrooptic response on temperature. It is shown that the analysis of the light modulation depth of the first and second harmonics prove to be useful for the identification of phase transition. [ABSTRACT FROM AUTHOR]

This article discusses an experimental analysis of the influence of periodically generated external hydrodynamic disturbances on the condensation process of the R134 refrigerant in circular pipe mini-channels. The investigations were carried out for horizontal single mini-channels with internal diameters in the range of d = 0.64–3.30 mm. It was established that within the range of frequencies under investigation (f = 0.2–5 Hz), i.e., the frequencies at which disturbances are generated, the disturbances exert an influence on the structure of the characteristic condensation areas in the mini-channel. The disturbances have an unfavorable impact on the reduction of the two-phase length of specific condensation and a reduction of the heat flux in this area. The heat removal intensity in the two-phase area has an impact on the efficiency of the operation of a compact condenser. The impact of more important parameters on this efficiency is discussed. [ABSTRACT FROM AUTHOR]

The knowledge of the material parameters related to the microscopic structure of liquid crystals is one of the main problems in the construction of the liquid crystal devices. In the case of ferroelectric liquid crystals, the viscoelastic properties are very important as they determine the switching speed and the threshold voltage in displays. There exist several experimental methods for measurements of viscosity and elasticity constants in tilted smectic phases which exploit various phenomena for deformation detection, e.g., light transmission, polarization current, light modulation, dielectric constant, and helix deformation or helix unwinding. In this article, we compared the results of measurements obtained for the same material using various methods. The experiments proved that the correct bulk values of the mentioned material constants can be determined using thick, homeotropically aligned samples only. [ABSTRACT FROM AUTHOR]

Excitation of solitary waves and their propagation in surface-stabilized ferroelectric liquid crystal cells under alternating external electric field is investigated both theoretically and experimentally. The effect of solitary waves on electro-optic response spectra is analyzed for different amplitudes of applied fields, temperatures, and sample thicknesses. It is shown that solitons can only be excited within narrow ranges of frequencies of the sufficiently strong electric fields. The minimal frequency, at which soliton waves appear in ferroelectric smectic liquid crystals, is found to be related to the material constants of these systems. It is proved that measuring this threshold frequency gives the possibility to determine one of the material parameters, if the others are known. In this way, the intra-smectic-layer elastic constant is found for systems with the chevron geometry. [ABSTRACT FROM AUTHOR]

Propagation of solitary waves activated in thin ferroelectric liquid crystal cells under external, sinusoidally alternating electric fields is investigated using the electro-optic technique. It is shown that solitons give contributions only to the loss component of the response spectrum, within rather narrow ranges of frequencies and in sufficiently strong fields. The limit frequency, at which the amplitude of the velocity of the solitary waves is greatest, is found to be related to material constants of liquid crystals. Measuring this threshold frequency provides the capability to determine the elastic constant of surface stabilized liquid crystalline materials in the bookshelf or chevron layer geometries. [ABSTRACT FROM AUTHOR]

The method of determination of the bulk values of the rotational viscosity coefficient of the smectic c-director in chiral smectic liquid crystals with a helical structure is described. The measurements were performed using optical detection in the small deformation limit. In contrast to the usual methods, the initial deformation of the helix (caused by strong surface interactions) was avoided by using homeotropic aligned thick samples. The coefficient was measured in 4-methylbutyloxy phenyl-4-octyloxy-benzoate (C8) in the presence of laminar flow. The critical temperature dependence of the measured coefficient was found. The relation between the measured coefficient and the smectic C order parameter is shown. [ABSTRACT FROM AUTHOR]

Purpose: The study objective was to evaluate the prevalence of urogenital Chlamydia trachomatis (C.tr.) infection in women with diagnosed infertility. Material and methods: The study involved patients from the Department of Gynecological Endocrinology and from the Center for Reproductive Medicine &bquo;Kriobank" in Bialystok. Female patients (n=71), aged 23 - 41, were divided into two groups according to the main diagnosis: A -- tubal infertility (23) and B - infertility of another origin (48). For direct testing, PCR method was used to detect C.tr. infection in cervical samples (Roche, Molecular Systems, N.J., USA). Specific IgA and IgG anti-chlamydial antibodies in the serum were determined by immunoenzymatic assay (medac, Hamburg, Germany). Diagnostic procedures were performed at the Centre for STD Research and Diagnostics in Bialystok. Results: In group A, C. infection was detected in: 8.7% patients, in group B - 8.3%. Specific anti - C.tr. antibodies IgA were detected in: 13.0 in group A and 6.3 in group BI IgG respectively in 39.1% and in 10.4%. Conclusions: 1. C.tr. infection is very important etiological factor of female infertility. 2. The detection of specific anti-chlamydial antibodies is a valuable, noninvasive diagnostic procedure. 3. Infertile women should be routinely tested for C.tr. infection. [ABSTRACT FROM AUTHOR]

Dielectric and optical methods to investigate the response of surface-stabilized ferroelectric liquid crystals (SSFLCs) of the chevron structure are examined and compared in the case of the azimuthal mode of collective relaxation processes. It is found that the variation of an effective (averaged over the chevron cell volume) dielectric permittivity tensor under the influence of a weak alternating external electric field is approximately equivalent to the transformation of this tensor as a consequence of the rotation of the laboratory frame around the axis perpendicular to the smectic plane about a small angle. Then, using an analytic solution of the equation of motion describing the azimuthal rotation of molecules, it is shown that both of the analysed approaches to calculate and measure the response of SSFLCs yield consistent results for these rotational dynamic processes. This allows the calculation of the spontaneous polarization of the unit volume of chevron slabs, provided that the pretilted azimuthal angle (in the absence of an applied electric field) within the smectic plane is known. [ABSTRACT FROM AUTHOR]

The chiral liquid crystalline (S)-4-(methylheptyloxycarbonyl) phenyl 4-(4'-octyloxyphenylcarbonyloxy) benzoate is distinguished by the exceptionally large temperature range of its [image omitted] phase. This allowed us to study in detail the director tilt angle and electric permittivity of [image omitted] in comparison to the temperature T and the electric field strength E. We basically observed that the SmCα temperature range is reduced at increasing electric field strength and completely disappears beyond a certain critical field. Tilt angle measurements were supplemented by dielectric studies, which accurately indicated the field-dependent phase transition temperatures and led to the accurate phase diagram in the T, E-plane. [ABSTRACT FROM AUTHOR]

Weak external electric field E causes two effects in chiral smectic liquid crystals: linear change of the optic axis direction and modification of the shape of the indicatrix. The relative changes in the light intensity consist of two components. The first component represents the modulation with the fundamental frequency f and the second one, with the doubled frequency 2f (second harmonic). We carried out measurements of the electrooptic modulation at both the first and second harmonics frequency. The applied calibration procedure allowed for expressing the experimental results as angular quantities independent of experimental conditions. Therefore we were able to determine the absolute values of the coefficients describing both effects of the electric field on the optical properties of the sample. We studied the temperature dependence of the first and second order coefficients in the ferroelectric smectic C* and paraelectric smectic A phases. The experiments delivered an information on the structure of tilted smectic liquid crystals and its dependence on the electric field. [ABSTRACT FROM AUTHOR]

Dielectric properties of a chiral smectic liquid crystal exhibiting ferroelectric and antiferroelectric forms of dipole order have been studied in the frequency range 10 Hz ÷ 1 MHz. Three relaxation bands were found in the hexatic ferroelectric phase and in the antiferroelectric phase, and six bands in the apparently ferrielectric state. The number of relaxation processes observed in the studied frequency range reduces to one in the smectic C α * and A phases. The results of measurement suggest that phases exhibiting ferrielectric properties might be in fact a mixture of ferroelectric and antiferroelectric clusters. This mixed state is stabilized by surface interactions. [ABSTRACT FROM AUTHOR]

Many methods for the determination of the order parameter in nematic liquid crystals are known. However, most of them are not applicable to cholesteric and smectic phases. Therefore, experimental data on the order parameter in cholesteric and smectic phases are hardly available. To determine the orientational order parameter S we exploited the de Gennes observation, that any anisotropic physical quantity may be a measure of orientational ordering in nematic mesophase. The order parameter can be calculated directly from a macroscopic quantity measured in the experiment. From this idea we developed a simple method for the determination of the order parameter based on birefringence measurements, which can be applied for nematic, cholesteric, and smectic phases. A precise and simple method for measurement of the optical birefringence is described. An approximate empirical formula is applied for normalization of the optical birefringence similar to that used by Haller for polarizabilities. The results are in excellent agreement with the literature data. We proved that in the case of optical anisotropy the order parameter is equal within ±1% to the one evaluated from polarizability anisotropy. Thus, the discussion concerning the local field can be omitted. Using the described method we determined the orientational order parameter in various mesophases. [ABSTRACT FROM PUBLISHER]

Many methods for the determination of the order parameter in nematic liquid crystals are known. However, most of them are not applicable to cholesteric and smectic phases. Therefore, experimental data on the order parameter in cholesteric and smectic phases are hardly available. To determine the orientational order parameter S we exploited the de Gennes observation, that any anisotropic physical quantity may be a measure of orientational ordering in nematic mesophase. The order parameter can be calculated directly from a macroscopic quantity measured in the experiment. From this idea we developed a simple method for the determination of the order parameter based on birefringence measurements, which can be applied for nematic, cholesteric, and smectic phases. A precise and simple method for measurement of the optical birefringence is described. An approximate empirical formula is applied for normalization of the optical birefringence similar to that used by Haller for polarizabilities. The results are in excellent agreement with the literature data. We proved that in the case of optical anisotropy the order parameter is equal within ±1% to the one evaluated from polarizability anisotropy. Thus, the discussion concerning the local field can be omitted. Using the described method we determined the orientational order parameter in various mesophases. [ABSTRACT FROM AUTHOR]

The paper presents an experimental analysis of the influence of dynamic disturbances on the size of the condensation zone of the appropriate new R1234yf environment-friendly refrigerant in circular mini-channels. Experimental tests were conducted for single minichanells placed horizontally, with an inner diameter d = {1.44; 2.30; 3.30} mm. A range of frequencies from f = 0.2 - 5 Hz of periodically generated disturbances showed an explicit and unfavourable influence on the decrease of the length of the proper condensation region. This influence reduced the efficiency of the process. A computational model was developed to calculate the length of the two-phase region under disturbance conditions. The model proposed was verified by the results of the experiment, and compliance was obtained in the range of ±25%.

The following paper presents the results of preliminary experimental research on the influence of instabilities of a hydrodynamic type on the condensation phase change process in tubular minichannels. The research was focused on a new pro-ecological refrigerant, R1234yf, intended as a substitute for R134a that currently is being phased out. The flow condensation phase change process was investigated for both steady and un-steady conditions in singular tubular minichannels with an internal diameter d = {1,44; 2,30; 3,30} mm. The scope of the analysis of the experimental data covered an estimation of propagation velocities for both pressure and temperature instabilities as well as the shrinkage of the condensation zone. The results were also compared with the previous results obtained for the flow condensation phase change of R134a refrigerant in tubular minichannels with the same internal diameters.

Orientational order parameter in five fluorinated nematogens have been investigated by means of optical, dielectric and 19F NMR techniques. Quantum mechanical calculations were also employed to derive molecular and nuclear properties necessary for the analysis of the spectroscopic quantities. The obtained data were compared and discussed taking into account the differences among the three methods. The values of the order parameter differ due to different anisotropic physical quantities measured and, consequently, the different axes frame in which the order parameters are defined. However, the temperature trends, expressed with the aid of the Haller-type relation, are very close within the broad range of the nematic phase. [ABSTRACT FROM AUTHOR]

Nonlinear dynamics induced in surface stabilized ferroelectric liquid crystals by strong alternating external electric fields is studied both theoretically and experimentally. As has already been shown, molecular reorientations induced by sufficiently strong fields of high-enough frequencies can reveal a long transient behavior that has a weakly chaotic character. The resulting complex dynamics of ferroelectric liquid crystals can be considered not only as a consequence of irregular motions of particular molecules but also as a repercussion of a surface-enforced partial decorrelation of nonlinear molecular motions within smectic layers. To achieve more insight into the nature of this phenomenon and to show that the underlying complex field-induced behavior of smectic liquid crystals is not exceptional, ranges of system parameters for which the chaotic behavior occurs are determined. It is proved that there exists a large enough set of initial phase trajectory points, for which weakly chaotic long-time transitory phenomena occur, and, thereby, it is demonstrated that such a chaotic behavior can be regarded as being typical for strongly field-driven thin liquid crystal systems. Additionally, the influence of low-amplitude random noise on the duration of the transient processes is numerically studied. The strongly nonlinear contribution to the electro-optic response, experimentally determined for liquid crystal samples at frequencies lower than the actual field frequency, is also analyzed for long-time signal sequences. Using a statistical approach to distinguish numerically response signals of samples from noise generated by measuring devices, it is shown that the distribution of sample signals distinctly differs from the device noise. This evidently corroborates the occurrence of the nonlinear low-frequency effect, found earlier for different surface stabilized liquid crystal samples. [ABSTRACT FROM AUTHOR]

Background: The 2D:4D digit ratio (DR), representing the relative length of the index finger to the ring finger, is an anthropometric marker that shows sexual dimorphism, with males typically having a lower ratio than females. This parameter is linked to prenatal androgen exposure (PAE), which influences sexual differentiation of the brain and behavior. This study aimed to investigate the correlation between PAE and sleep among young adults., Methods: Anthropometric measurements were used to assess PAE, while sleep was evaluated using the Pittsburgh Sleep Quality Index (PSQI), Morningness-Eveningness Questionnaire (MEQ), actigraphy, and polysomnography (PSG). Data was collected from 720 participants via surveys, with 290 completing all questionnaires. Of these, 138 underwent anthropometric measurements, and 38 were further recruited for actigraphy, PSG., Results: Men exhibited a lower 2D:4D ratio than women, indicating higher PAE. The average PSQI score was 6.94 ± 2.98, and the MEQ score was 35.43 ± 19.59, with no significant gender differences in sleep quality or chronotype. Low PAE was associated with better sleep efficiency and a morning chronotype, but worse sleep quality in males. Actigraphy results showed no significant differences based on PAE. PSG data revealed that males with longer 2nd fingers and higher 2D:4D ratios were more likely to suffer from mild sleep apnea, a pattern not observed in women. PAE did not significantly impact other sleep architecture parameters., Conclusions: PAE, indicated by the 2D:4D ratio, is linked to sleep efficiency and chronotype, with significant gender differences. Men with lower PAE exhibited poorer sleep quality, and those with certain finger length patterns were more prone to mild sleep apnea. These findings underscore the potential long-term impacts of PAE on sleep health and emphasize the need for further research into gender-specific sleep regulation mechanisms., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2025 Bartoszek, Sawic, Pierzchała, Kudrycka, Białasiewicz and Kuczyński.)

Background/Objectives: Male infertility is a significant global health issue, comprising approx. 50% of all infertility cases. Semen cryopreservation, a critical component of assisted reproductive technologies (ARTs), is a method commonly used in a wide range of situations, including gonadotoxic treatments such as radiation or chemotherapy, hazardous occupational exposures, and various medical conditions. Although historically viewed as potentially damaging to sperm, recent findings suggest that cryopreservation, when performed with appropriate techniques, may in fact enhance semen quality by improving the proportion of healthy spermatozoa, particularly in terms of their morphological parameters. The aim of this study was to evaluate the impact of cryopreservation on sperm morphology and viability, utilizing advanced morphological assessments pre- and post-freezing. Methods: Semen samples were collected from 97 patients undergoing infertility treatment at the KRIOBANK clinic (Białystok, Poland). The semen was liquefied and prepared in the form of slides. Sperm morphology was then assessed using an OLYMPUS BX40 microscope at 60× magnification. Results: The findings of the study revealed significant improvements in sperm morphology, with increased percentages of normal sperm and reductions in deformation indices post-thaw. Conclusions: The findings indicate that optimized cryopreservation protocols may support the selection of higher-quality sperm, offering valuable benefits for ART applications. These results challenge certain past assumptions regarding the impact of cryopreservation and underscore the need for refined freezing techniques to maintain and potentially enhance semen quality for reproductive use.