Cholesteric Crystal Research Articles

Modeling of the lyotropic cholesteric liquid crystal based toxic gas sensor using adaptive neuro-fuzzy inference systems

Detection of toxic gases is important in a variety of settings, including industrial facilities, laboratories, and even in homes. In these settings, toxic gas detection can help prevent accidents and protect the health and safety of workers, researchers, and others who may be exposed to these gases. This study evaluates an Adaptive Neuro-Fuzzy Inference System (ANFIS) models in predicting the machining responses in the detection of toxic gases vapor, such as toluene (T), phenol (P) and 1,2 dichloropropane (D) using lyotropic cholesteric crystal (CLC) have been shown to have potential as gas sensors due to their unique optical and liquid crystal (LC) properties, and the ANFIS model may be used to better understand and optimize these properties for toxic gas detection. Experiments were carefully carried out to gather data on the response of a lyotropic CLC toxic gas vapor sensor. The effectiveness of using ANFIS combined with Grid Partitioning (GP) was then carefully studied and evaluated in terms of modeling and predicting the responses of the sensor. The best ANFIS-GP model is chosen from these criteria; RSS, PCC, R2, RMSE, MSE, MAE, and MAPE. In addition, validation was performed between the model and experimental data using the LOOCV method. The results show that the ANFIS-GP5 model with 96 fuzzy inference systems (FIS) rules with high R2 values. According to the ANFIS-GP5 model, R2varied ranges from 0.77 to 1 for train, test, and total data of lyotropic CLC sensor exposed to toluene, phenol and 1,2 dichloropropane toxic gases vapors.

Maxillary Sinusitis of Odontogenic Origin in Relation to Ectopic 2.8 Associated with Follicular Dentigerous Cyst – Combined Transnasal and Oral Endoscopic Approach: A Case Report

Purpose: To describe the management of orosinusal pathology by combined transnasal and oral endoscopy. Methods: The 54-year-old patient underwent a dental and otolaryngological evaluation for left odontogenic maxillary sinusitis in relation to plausible dental follicular cyst of ectopic element 2.8. The symptoms reported at the time of access to the hospital were nasal obstruction and nocturnal rhonchopathy. In the ENT evaluation by videorhinoscopy with rigid optics, complex deviation of the nasal septum was revealed, without any evident formation or pathological secretion. On inspection of the oral cavity, the mucous membranes appeared unscathed. The previously extracted aleveolus of 1.6 was evident. The radiological examination, facial CT, revealed the left maxillary sinus almost completely occupied by a cystic appearance, with thin calcified walls and homogeneous content that had a dental element, probably the 2.8, which fenestrates the vestibular cortex of the lateral wall of the maxillary sinus. This lesion erodes the medial wall of the sinus, obliterating the ostiomeatal complex and imprinting the ipsilateral ethmoidal cells. Biohumoral tests showed normal coagulation parameters, indices of renal function, liver and ionemia. The patient under general anesthesia and oral intubation with a combined intervention of the left anterior FESS, intrasulcular flap from dental elements 2.7 to 2.3 with mesial releasing incision, moderate osteotomy, ectopic 2.8 extraction and enucleation of the cystic lesion with simultaneous closure of the orosinusal communication with advancement of the Bichat fat pad and closure by first intention. In the same session, the ENT moment is carried out transnasally for total left uncinectomy, medium antrostomy with the union of the natural ostium and the accessory ostium. Bilateral lower turbinoplasty with bipolar forceps. The patient was then controlled after 15 days and then six months, showing good healing and no signs of recurrence at the rhinoscopic check on the physical examination of the oral cavity. Results: Based on the clinical and radiological aspect, the diagnosis of a follicular dentigerous cyst (WHO 2017) covered by a multi-layered non-keratinized paving epithelium, with moderate chronic inflammation, including gigantocellular and cholesteric crystals, is reached from the microbiological and histological examination. Necrotic amorphous material coexists including rare hyphae and fungal spores, with mycotic and actinomycotic superinfection. Conclusions: The combined oral and nasal intervention, allowed by the collaboration between the oral surgeon and ENT, has made it possible to shorten the healing time and resolve the pathology without recurrence.

Maxillary sinusitis of odontogenic origin in relation to ectopic 2.8 associated with follicular dentigerous cyst: Combined transnasal and oral endoscopic approach, a case report

Purpose of the study: To describe the management of orosinusal pathology by combined transnasal endoscopy and oral combined. Methods: The 54-year-old patient underwent a dental and otolaryngological evaluation for left odontogenic maxillary sinusitis in relation to plausible dental follicular cyst of ectopic element 2.8. The symptoms reported at the time of access to the hospital were nasal obstruction and nocturnal rhonchopathy. To the ENT evaluation in videorinoscopy with rigid optics, complex deviation of the nasal septum was relevated with not any evident formations or pathological secretions. While on inspection of the oral cavity the mucous membranes appeared unscathed. Alveolus of 1.6 previosuly extracted was evident. The radiological examination, facial CT, revealed the left maxillary sinus almost completely occupied by a cystic appearance, with thin calcified walls and homogeneous content that has a dental element, probably the 2.8, which fenestrates the vestibular cortex of the lateral wall of the maxillary sinus. This lesion erodes the medial wall of the sinus, obliterating the ostio-meatal complex and imprinting the ipsilateral ethmoidal cells. Biohumoral tests showed normal coagulation parameters, indices of renal function, liver and ionemia. The patient under general anesthesia and oral intubation with a combined intervention of the left anterior FESS, intrasulcular flap from dental elements 2.7 to 2.3 with mesial releasing incision, moderate osteotomy, ectopic 2.8 extraction and enucleation of the cystic lesion with simultaneous closure of the orosinusal communication with advancement of the Bichat adipose bolla and closure by first intention. In the same session, the ENT moment is carried out trans nasally for total left uncinectomy, medium antrostomy with the union of the natural ostium and the accessory ostium. Bilateral lower turbinoplasty with bipolar forceps. The patient was then controlled after 15 days and six months, showing good healing and no signs of recurrence at the rhinoscopic check on the physical examination of the oral cavity. Results: based on the clinical and radiological aspect, the diagnosis of a follicular dentigerous cyst (WHO 2017) covered by a multi-layered non-keratinized paving epithelium, with moderate chronic inflammation, including gigantocellular and cholesteric crystals, is reached from the microbiological and histological examination. Necrotic amorphous material coexists including rare hyphae and fungal spores, with therefore mycotic and actinomycotic super infection. Conclusions: The combined oral and nasal intervention, allowed by the collaboration between the oral surgeon and ENT, has made it possible to shorten the healing time and to resolve the pathology without any sign of recurrence.

The study of the helical pitch of cholesteric liquid crystals by introducing achiral rod-like molecules

To design and synthesize achiral rod-like ester compounds, 4-n-octyloxybiphenyl-4′-octyloxybenzoate. The compound is similar to 4-octyloxyphenyl 4-octyloxybenzoate, which could provide expectantly with effects like chiral materials. n-4′-methoxybenzylidene-n-butylaniline (MBBA) is also an achiral rod-like molecule, which is not chiral in terms of conformation. Two compounds were added to a mixture with several types of cholesteric liquid crystals that are liquid crystals at room temperature, and it was found that the helical pitch of cholesteric crystals that were mixed with 4-n-octyloxybiphenyl-4′-octyloxybenzoate was inclined to become longer. The other compound, MBBA, added in cholesteric liquid crystals made helical pitch shorter. The results are the same as when chiral molecules are added to cholesteric liquid crystals.

Angular dependences of the luminescence and density of photon states in a chiral liquid crystal

Luminescence spectra of a laser dye-doped chiral liquid crystal have been studied in a wide range of angles (up to 60°) to the axis of its helical structure using a semicylindrical quartz prism, which made it possible to observe the shift and evolution of the photonic band gap in response to changes in angle. Using measured spectra and numerical simulation, we calculated the spectral distributions of the density of photon states in such a cholesteric crystal for polarised and unpolarised light, which characterise its structure as that of a chiral one-dimensional photonic crystal.

Comment on “Direct measurements of the thermomechanical Lehmann coefficient in a compensated cholesteric crystal” by Oswald P. and Dequidt A.

Comment on “Direct measurements of the thermomechanical Lehmann coefficient in a compensated cholesteric crystal” by Oswald P. and Dequidt A.

Reflection and transmission of light by cholesteric liquid crystal-glass-cholesteric liquid crystal and cholesteric liquid crystal(1)-cholesteric crystal(2) systems

Reflection and transmission of light by cholesteric liquid crystal-glass-cholesteric liquid crystal and cholesteric liquid crystal(1)-cholesteric liquid crystal(2) systems were studied. The classical Ambartsumyan method of adding layers and the concept of a sewing function were used. This approach was developed earlier in astrophysics for the theory of radiation transfer. Here, we used a version of this method adapted to wave optics. The Jones matrices are constructed for these systems. The features of the reflection and transmission spectra, optical rotation and ellipticity of polarization were studied for these systems. It is proposed to use these systems as tunable narrow-band filters and mirrors. These systems can be used, for example, to develop a variety of optical elements for lasers and of polarimetric elements in ellipsometry. The specific features of eigenpolarization are also discussed. It is shown that optical rotation of the two layers of cholesteric liquid crystals, which differ from each other only by the sign of the helix, is nonzero, and it becomes substantial in the diffraction reflection region. A unique property of these systems is the degeneracy (coincidence) of eigenpolarizations.

Improvements in a new technique for measuring and mapping heat transfer coefficients

Two important improvements in a new technique for measuring and mapping local heat transfer coefficients are described. The first improvement involves the use of a new encapsulated thermochromic liquid crystal which has better stability and a narrower bandwidth than the cholesteric crystals previously used. The second important improvement is in the packaging arrangement. In this new arrangement, useful for gas flows, the liquid crystal is applied directly on the surface of an electrically conducting gold coating used as an electric heater, and is essentially in direct contact with the fluid. The encapsulated liquid crystal used in this study was applied directly to the gold surface without affecting the electrical characteristics of the gold coating. This new packaging arrangement has two advantages. First, no correction for the temperature drop across the plastic substrate is required. Second, a significant increase in the maximum detectable frequency is predicted.

Matrix-addressable controlled transparency

An investigation was made of the characteristics of a matrix-addressable controlled transparency of 1 kbit capacity. Spatial modulation of the radiation was due to the dynamic scattering with memory in a mixture of nematic and cholesteric crystals. The recording, storage, and erasure times, the modulation coefficient, the control power, and the distribution of the transmitted radiation across the transparency area were all investigated. A working cycle of the transparency was 4 sec and the modulation coefficient was 97%. The results demonstrated that the transparency was suitable for recording information in holographic memories.

Momentary distribution of forces under the foot

The difference in distribution of forces between walking and running is compared in ten normal subjects. Our analysis of walking gait demonstrates the smooth progression of force distribution from heel strike through push-off with multiple areas of the foot utilized for balance throughout weight bearing. Running shifts weightbearing to the forefoot as the flexors of the foot decelerate the rate of impact and then provide the propulsive force necessary for push-off. Comparison of walking versus running demonstrates that the average duration of foot contact in ten subjects decreases from 0·47 ± 0·01 to 0·29 ± 0·02 sec. The pattern and rate of progression of weight distribution from one area of the foot to another also changes. The time interval from heel strike to first metatarsal head strike shortens by 75 per cent. The average duration and progression of forces in these ten subjects was then compared to several patients with either pes cavus, pes planus, or a tibio-fibular synostosis. Alterations in walking and running gait patterns seen on the cholesteric crystals demonstrated abnormal distribution of force consistent with their pathology.

Comparison between square, triangular, or one dimensional lattice of distortions in smectic A and cholesteric crystals for superposed strain and magnetic field of any directions

We study the conditions of observations of a static periodic square grid or lattice of distortions in cholesteric of smectic A liquid crystals under a static magnetic field or fast tensile strain. We show that a square lattice is energetically favorable with respect to other lattices. With a tilted magnetic field H we expect two threshold fields: (a) a one dimensional distortion threshold field H1 and (b) a two dimensional square distortion field H2>H1. H1 and H2 are function of the angle θ of H with the normal to the layers. There exists only a one dimensional solution for θ>30°.

A Microwave Analog of Optical Rotation in Cholesteric Liquid Crystals

A microwave structure was built that is, essentially a scaled up model of a cholesteric liquid crystal. The model consists of a series of thin plastic sheets to which copper wires are attached of dimensions small compared to the microwave length. The direction of the wires on successive sheets varies in a screw-type fashion while the distance between successive sheets and thus the pitch of the screw can be varied. This model shows optical rotation and also, when the period of the screw structure is approximately equal to the wavelength of the microwaves used, the behavior typical of cholesteric crystals, that is, one sense of circular polarization is reflected, the opposite sense is transmitted. Qualitative agreement with experiments in light reflection and transmission using a cholesteric liquid crystal was obtained.

Visual estimation of body temperature in neonates

Abdominal skin temperature of human neonates who are dressed and blanketed closely approximates core temperature. Although valuable in the detection of such illness as sepsis and hypoglycemia, the low yield of detecting abnormalities in term infants has resulted in temperature being measured at widely spaced intervals in most nurseries. This report describes a widely spaced intervals in most nurseries. This report describes a way of visually estimating body temperature using the cholesteric phenomenon. A mixture of cholesteric crystals was formulated whose color was green between 36.3–37.1°C (normal abd. skin temp.). Below this temp. the color brown; above, green-blue (37.2–37.9°C) or blue(>37.9°C). The crystals were fixed to black saran plastic with an adhesive undersurface which permitted fixation to the skin. 365 observations (65 infants) were made of the color of the abdominal tape compared to rectal temperature.Conclusions: Body temperature of term infants can be estimated accurately, quickly, simply and frequently by this method.

LIGNES DE DISLOCATION DANS LES CHOLESTÉRIQUES

A topological study of dislocations in liquid crystals leads to a distinction between perfect disclinations with a rotation either parallel or orthogonal to the helical axis of a cholesteric crystal. The pairing of two disclinations of the second kind with opposite signs leads to a low energy splitting of a multiple disclination of the first kind. With small corrections which slightly increase their energy, such pairs can take arbitrary forms. The molecular configuration within the core of these pairs explains satisfactorily their instability under magnetic fields.

The Use of Liquid Cholesteric Crystals for Thermographic Measurement of Skin Temperature in Man

Abstract The skin over subcutaneous lesions of primary or metastatic carcinomas and sarcomas is frequently warmer than the apparently normal surrounding skin.1–3 Thus thermotopographic measurement of skin temperature over tumor lesions can be useful for measurement of size, vascular physiology and response to treatment.