Estimating physical properties from liquid crystal textures via machine learning and complexity-entropy methods

Imaging techniques are essential tools for inquiring a number of properties from different materials. Liquid crystals are often investigated via optical and image processing methods. In spite of that, considerably less attention has been paid to the problem of extracting physical properties of liquid crystals directly from textures images of these materials. Here we present an approach that combines two physics-inspired image quantifiers (permutation entropy and statistical complexity) with machine learning techniques for extracting physical properties of nematic and cholesteric liquid crystals directly from their textures images. We demonstrate the usefulness and accuracy of our approach in a series of applications involving simulated and experimental textures, in which physical properties of these materials (namely: average order parameter, sample temperature, and cholesteric pitch length) are predicted with significant precision. Finally, we believe our approach can be useful in more complex liquid crystal experiments as well as for probing physical properties of other materials that are investigated via imaging techniques.Comment: 11 two-column pages, 7 figures; accepted for publication in Physical Review

Formation of disclination lines near a free nematic interface

We have studied the nucleation and the physical properties of a -1/2 wedge disclination line near the free surface of a confined nematic liquid crystal. The position of the disclination line has been related to the material parameters (elastic constants, anchoring energy and favored anchoring angle of the molecules at the free surface). The use of a planar model for the structure of the director field (whose predictions have been contrasted to those of a fully three-dimensional model) has allowed us to relate the experimentally observed position of the disclination line to the relevant properties of the liquid crystals. In particular, we have been able to observe the collapse of the disclination line due to a temperature-induced anchoring angle transition, which has allowed us to rule out the presence of a real disclination line near the nematic/isotropic front in directional growth experiments. 61.30.Jf,61.30.G

Web-based interface system for bedside monitor

From face-to-face consultation to medicine at a distance, technology is changing the way medical services are delivered to the people. We are going into an era where the information is being digitized to be stored in a database. This is done in order to reduce information overlap and redundancy that are the main problems the health care sector are facing right now. More hospitals in other more advanced countries are going paperless. In order to provide better services to the critically ill patients in the ICU or CCU, a data acquisition program is developed for the acquisition of vital signs monitored in the critical care units. This work discusses the work done in extracting the data and signal from patient monitor BSM 8800 to the computer. The data are acquired using RS232C Interface Protocol. The vital signs acquired include oxygen saturation (SaCh), heart rate (HR), electrocardiograph (ECG) signal, non-invasive blood pressure (NIBP), respiration rate (RR), temperature (TEMP) and end tidal carbon dioxide (PETCO2 or ETCO2). Ventricular Premature Contraction (VPC), ST level and arrhythmia information are also acquired and displayed to provide a more thorough information on the condition of the patients. Alarm detection is also programmed so that in critical conditions the vital signs will be displayed in red for extra caution. An ECG user control is designed and embedded in the web page in order to convert and plot the ECG waveform from hexadecimal values sent from the bedside monitor. The user control has been tested its accuracy and proved its validity to reconstruct the original ECG waveform. Basic patient information can also be seen from the graphical user interface (GUI) that has been developed. Physicians and medical practitioners have to register with the system before gaining access to the system and only the physician-in-charge of the patient can see the more intricate details of the patient

Optimization of the GAFF Force Field to Describe Liquid Crystal Molecules: The Path to a Dramatic Improvement in Transition Temperature Predictions

The physical properties and phase transitions of thermotropic liquid crystals are highly sensitive to small changes in chemical structure. However, these changes are challenging to model, as both the phase diagram and mesophase properties obtained from fully atomistic simulations are strongly dependent on the force field model employed, and the current generation of chemical force fields has not proved accurate enough to provide reliable predictions of transition temperatures for many liquid crystals. This paper presents a strategy for improving the nematic clearing point, TNI, in atomistic simulations, by systematic optimization of the General Amber Force Field (GAFF) for key mesogenic fragments. We show that with careful optimization of the parameters describing a series of liquid crystal fragment molecules, it is possible to transfer these parameters to larger liquid crystal molecules and make accurate predictions for nematic mesophase formation. This new force field, GAFF-LCFF, is used to predict the nematic-isotropic clearing point to within 5°C for the nematogen 1,3-benzenedicarboxylic acid,1,3-bis(4-butylphenyl)ester, an improvement of 60°C over the standard GAFF force field

Wetting of cholesteric liquid crystals

We investigate theoretically the wetting properties of cholesteric liquid crystals at a planar substrate. If the properties of substrate and of the interface are such that the cholesteric layers are not distorted the wetting properties are similar to those of a nematic liquid crystal. If, on the other hand, the anchoring conditions force the distortion of the liquid crystal layers the wetting properties are altered, the free cholesteric-isotropic interface is non-planar and there is a layer of topological defects close to the substrate. These deformations can either promote or hinder the wetting of the substrate by a cholesteric, depending on the properties of the cholesteric liquid crystal

Properties of the Broad-Range Nematic Phase of a Laterally Linked H-Shaped Liquid Crystal Dimer

In search for novel nematic materials, a laterally linked H-shaped liquid crystal dimer have been synthesized and characterized. The distinct feature of the material is a very broad temperature range (about 50 oC) of the nematic phase, which is in contrast with other reported H-dimers that show predominantly smectic phases. The material exhibits interesting textural features at the scale of nanometers (presence of smectic clusters) and at the macroscopic scales. Namely, at a certain temperature, the flat samples of the material show occurrence of domain walls. These domain walls are caused by the surface anchoring transition and separate regions with differently tilted director. Both above and below this transition temperature the material represents a uniaxial nematic, as confirmed by the studies of defects in flat samples and samples with colloidal inclusions, freely suspended drops, X-ray diffraction and transmission electron microscopy.Comment: 30 pages (including Supplementary Information), 7 Figure

Comparative analysis of anisotropic material properties of uniaxial nematics formed by flexible dimers and rod-like monomers

We report temperature dependencies of material properties such as dielectric anisotropy, birefringence, splay (K₁₁), twist (K₂₂), and bend (K₃₃) elastic constants of the uniaxial nematic (N) phase formed by flexible dimers of DTC5C9 and compare their behavior to that of a corresponding monomer MCT5. DTC5C9 forms a twist-bend nematic (Ntb) at temperatures below the N phase. Anisotropic properties of MCT5 are typical of the rod-like mesogens. In particular, birefringence increases as the temperature is reduced, following the classic behavior, described by Haller. The elastic constants also follow the standard behavior, with their ratios being practically temperature-independent. In contrast, DTC5C9 shows a dramatic departure from the standard case. Birefringence changes non-monotonously with temperature, decreasing on approaching the N-Ntb phase transition. K₃₃ decreases strongly to 0.4 pN near the N - Ntb transition, although remains finite. The ratios of the elastic constants in DTC5C9 show a strong temperature dependence that can be associated with the bend-induced changes in the orientational distribution function. The measured elastic properties are consistent with the tendency of the dimeric molecules to adopt bent configurations that give rise to the Ntb phase

New way to create high-speed LCDs based on the use of modified nanomaterials

Modified “detonation nanodiamond” (MDND), graphene oxide (MGO) and nanoclay (MNC) were doped to nematic (NLCs) and ferroelectric liquid crystals (FLCs). The effect of modified nanomaterials on the physical and electro-optical properties of liquid crystals was investigated