Anchoring Energy And Pretilt Angle Effects On Liquid Crystal Response Time

This dissertation covers some important topics on the liquid crystal-substrate surface effects, including theoretical derivations and confirming experimental results. The research work is expected to make important impacts on liquid crystal device designs and to open new doors for further research along these topics. In this dissertation, a novel high-electric-field technique is developed to characterize the anchoring energy of vertically-aligned liquid crystal cells. Both theoretical analyses and confirming experimental results are presented. Vertically-aligned liquid crystal cells with buffed polyimide alignment layers are used to validate the measurement techniques. Based on the voltage-dependent transmittance of the liquid crystal cells, a linear fitting can be obtained, which leads to a precise determination of the anchoring energy. If some specific liquid crystal material parameters are known, then the traditional cell capacitance measurements can be avoided. Anchoring energy and cell gap effects on liquid crystal response time is theoretically analyzed and experimentally investigated. A novel theory on the liquid crystal dynamics is developed. In this part, two different theoretical approaches are discussed: one is surface dynamic equation method and the other is effective cell gap method. These two different approaches lead to consistent results, which are also confirmed by our experimental results. This work opens a new door for LCD industry to optimize liquid crystal response time, and it is especially critical for liquid crystal cells with thin cell gap, which is a promising approach for fast response time liquid crystal display. Pretilt angle effects on liquid crystal dynamics are analyzed theoretically and validated experimentally. Analytical expressions are derived to describe liquid crystal response time under nonzero pretilt angle conditions. The theoretical analysis is confirmed experimentally using vertically-aligned liquid crystal cells. These results quantitatively correlate pretilt angles with liquid crystal response time, which is important for optimizing liquid crystal response time

Axially-symmetric sheared polymer network liquid crystals

An axially-symmetric sheared polymer network liquid crystal (SPNLC) device is demonstrated and its performances characterized. Through analyzing the structure of this axially-symmetric SPNLC, we constructed a 3-D model to explain the observed phenomena. The simulation results agree well with the experiment. Two potential applications of such an axially-symmetric SPNLC, namely tunable-focus negative lens and spatial polarization converter, are discussed

Neo-sex chromosomes in the black muntjac recapitulate incipient evolution of mammalian sex chromosomes

The nascent neo-sex chromosomes of black muntjacs show that regulatory mutations could accelerate the degeneration of the Y chromosome and contribute to the further evolution of dosage compensation

Anchoring energy and cell gap effects on liquid crystal response time

The anchoring energy and cell gap effects on liquid crystal response time (tau(0)) is analyzed theoretically and validated experimentally. Analytical expressions are derived using two different approaches: effective cell gap and surface dynamic equation methods. Consistent results are deduced from these two approaches. A simplified equation tau(0)similar to d(x) also fits the experimental data well, where d is the liquid crystal cell gap and x is the exponent. Under two extreme (strong and weak) anchoring limits, the exponent x approaches 2 and 1, respectively. This information is helpful for optimizing liquid crystal devices for display applications

Polar anchoring energy measurement of vertically aligned liquid-crystal cells

An electric-field method is developed for measuring the polar anchoring energy of vertically aligned nematic liquid-crystal cells. Both theoretical analyses and confirming experimental results are presented. Vertically aligned liquid-crystal cells with buffed polyimide alignment layers are used to investigate the measurement techniques. Based on the voltage-dependent transmittance of the liquid-crystal cells, a linear fitting can be obtained, leading to a precise determination of the anchoring energy. If some specific liquid-crystal material parameters are known, measuring of the cell capacitance is not necessary

Color Performance Of An Mva-Lcd Using An Led Backlight

The color performance, including color gamut, color shift, and gamma curve, of a multidomain vertical-alignment (MVA) liquid-crystal display (LCD) using an LED backlight are calculated quantitatively. Simulation results indicate that an LED backlight exhibits better angular color uniformity and smaller color shifts than a CCFL backlight. Color gamut can be further widened and color shift reduced when using a color-sequential RGB-LED backlight without color filters, while the angular-dependent gamma curves are less influenced using different backlights. The obtained quantitative results are useful for optimizing the color performance and color management of high-end LCD monitors and LCD TVs. © Copyright 2008 Society for Information Display

Color Performance Of A Mva Lcd Using Led Backlight

The color performances such as color gamut, color shift, and gamma curve of a MVA LCD using LED backlight are calculated quantitatively. Simulation results indicate that LED backlight exhibits better angular color uniformity and smaller color shifts than CCFL backlight. Color gamut can be further widened and color shift reduced when using color-sequential RGB-LED backlight without color filters. In the meantime, the angulardependent gamma curves are less influenced using different backlights. The obtained quantitative results are useful for optimizing the color performances and color management of highend LCD monitors and LCD TVs. Copyright 2007 Society for Imaging Science and Technology

Cell Gap Effect On The Dynamics Of Liquid Crystal Phase Modulators

This paper provides a complete physical picture of optical response time as a function of cell gap (d) in a wide voltage regime. Normally both rise and decay times are known to be proportional to d 2 in the small angle approximation (), and in the high voltage regime where Vπ \u3c Vi \u3c Vi the optical decay time is independent of d. In this paper, we found that between these two extremes there is a region where the response time is linearly proportional to d. Our analytical derivation is confirmed by experimental results

Second And Fourth Harmonic Frequencies In Electric Field-Induced Liquid Crystal Reorientations

The second and fourth harmonics of low frequency electric field-induced liquid crystal reorientations are analyzed theoretically and confirming results observed experimentally. These transient dynamic optical responses manifest when the phase of a homogeneous cell is nearby N or [image omitted], where N is an integer. These ripples would influence the grayscales of liquid crystal devices if the driving electric field frequency is comparable to the liquid crystal response rate

Insulin resistance in polycystic ovary syndrome across various tissues: an updated review of pathogenesis, evaluation, and treatment

Abstract Polycystic ovary syndrome (PCOS) is a common endocrine disorder characterized by chronic ovulation dysfunction and overabundance of androgens; it affects 6–20% of women of reproductive age. PCOS involves various pathophysiological factors, and affected women usually have significant insulin resistance (IR), which is a major cause of PCOS. IR and compensatory hyperinsulinaemia have differing pathogeneses in various tissues, and IR varies among different PCOS phenotypes. Genetic and epigenetic changes, hyperandrogenaemia, and obesity aggravate IR. Insulin sensitization drugs are a new treatment modality for PCOS. We searched PubMed, Google Scholar, Elsevier, and UpToDate databases in this review, and focused on the pathogenesis of IR in women with PCOS and the pathophysiology of IR in various tissues. In addition, the review provides a comprehensive overview of the current progress in the efficacy of insulin sensitization therapy in the management of PCOS, providing the latest evidence for the clinical treatment of women with PCOS and IR