Polarity-dependent dielectric torque in nematic liquid crystals

The dielectric dispersion in the uniaxial nematic liquid crystals affects the switching dynamics of the director, as the dielectric torque is determined by not only the present values of the electric field and director but also by their past values. We demonstrate that this dielectric memory leads to an unusual contribution to the dielectric torque that is linear in the present field and thus polarity-sensitive. This torque can be used to accelerate the switch-off phase of director dynamics.Comment: 12 pages, 4 figure

Distributed consensus of discrete time-varying linear multi-agent systems with event-triggered intermittent control

The consensus problem of discrete time-varying linear multi-agent systems (MASs) is studied in this paper. First, an event-triggered intermittent control (ETIC) protocol is designed, aided by a class of auxiliary functions. Under this protocol, some sufficient conditions for all agents to achieve consensus are established by constructing an error dynamical system and applying the Lyapunov function. Second, in order to further reduce the communication burden, an improved event triggered intermittent control (I-ETIC) strategy is presented, along with corresponding convergence analysis. Notably, the difference between the two control protocols lies in the fact that the former protocol only determines when to control or not based on the trigger conditions, while the latter, building upon this, designs new event trigger conditions for the update of the controller during the control stage. Finally, two numerical simulation examples are provided to demonstrate the effectiveness of the theoretical results

MicroRNA-483 amelioration of experimental pulmonary hypertension.

Endothelial dysfunction is critically involved in the pathogenesis of pulmonary arterial hypertension (PAH) and that exogenously administered microRNA may be of therapeutic benefit. Lower levels of miR-483 were found in serum from patients with idiopathic pulmonary arterial hypertension (IPAH), particularly those with more severe disease. RNA-seq and bioinformatics analyses showed that miR-483 targets several PAH-related genes, including transforming growth factor-β (TGF-β), TGF-β receptor 2 (TGFBR2), β-catenin, connective tissue growth factor (CTGF), interleukin-1β (IL-1β), and endothelin-1 (ET-1). Overexpression of miR-483 in ECs inhibited inflammatory and fibrogenic responses, revealed by the decreased expression of TGF-β, TGFBR2, β-catenin, CTGF, IL-1β, and ET-1. In contrast, inhibition of miR-483 increased these genes in ECs. Rats with EC-specific miR-483 overexpression exhibited ameliorated pulmonary hypertension (PH) and reduced right ventricular hypertrophy on challenge with monocrotaline (MCT) or Sugen + hypoxia. A reversal effect was observed in rats that received MCT with inhaled lentivirus overexpressing miR-483. These results indicate that PAH is associated with a reduced level of miR-483 and that miR-483 might reduce experimental PH by inhibition of multiple adverse responses

Electromagnetically induced transparency in terahertz plasmonic metamaterials via dual excitation pathways of the dark mode

We observe the excitation and tuning of electromagnetically induced transparency (EIT) by the interference between different excitation pathways of the dark mode in a planar terahertz metamaterial. The EIT unit cell consists of a cut wire as the bright resonator and a pair of split ring resonators (SRRs) as the dark element. The dark mode resonance is excited by both the electric and magnetic fields when the SRR pair translates along the wire without altering the lateral distance between the resonators. The electric and magnetic pathways of exciting the dark mode allows for a giant amplitude modulation of the EIT resonance.Peer reviewedElectrical and Computer Engineerin

Frataxin deficiency promotes endothelial senescence in pulmonary hypertension

The dynamic regulation of endothelial pathophenotypes in pulmonary hypertension (PH) remains undefined. Cellular senescence is linked to PH with intracardiac shunts; however, its regulation across PH subtypes is unknown. Since endothelial deficiency of iron-sulfur (Fe-S) clusters is pathogenic in PH, we hypothesized that a Fe-S biogenesis protein, frataxin (FXN), controls endothelial senescence. An endothelial subpopulation in rodent and patient lungs across PH subtypes exhibited reduced FXN and elevated senescence. In vitro, hypoxic and inflammatory FXN deficiency abrogated activity of endothelial Fe-S–containing polymerases, promoting replication stress, DNA damage response, and senescence. This was also observed in stem cell–derived endothelial cells from Friedreich’s ataxia (FRDA), a genetic disease of FXN deficiency, ataxia, and cardiomyopathy, often with PH. In vivo, FXN deficiency–dependent senescence drove vessel inflammation, remodeling, and PH, whereas pharmacologic removal of senescent cells in Fxn-deficient rodents ameliorated PH. These data offer a model of endothelial biology in PH, where FXN deficiency generates a senescent endothelial subpopulation, promoting vascular inflammatory and proliferative signals in other cells to drive disease. These findings also establish an endothelial etiology for PH in FRDA and left heart disease and support therapeutic development of senolytic drugs, reversing effects of Fe-S deficiency across PH subtypes

Temperature dependent elastic, lattice vibronic and thermal properties of nanomaterials

It is well known that the physical properties of a macroscopic system can be well described using classical approaches such as the Gibbs free energy or the continuum medium mechanics, which relates the measurable quantities directly to the external applied stimulus such as temperature, pressure, chemical composition, electric and magnetic field, etc, without considering the atomistic origin. At atomic scale, quantum effect becomes dominant and the physical properties of a small object can be reliably obtained from computations by solving the Schrödinger equations or Newton motion equations with a sum of averaged interatomic potentials as a key element. However, for a small system in nanometer scale, both classical and quantum approaches have their limitations. Therefore, an effective approach solving the difficulties encountered by both classical and quantum approximations has been a great challenge. The recently advanced bond-order-length-strength (BOLS) correlation suggests that the size dependent material property is mainly attributed to the interaction between under-coordinated atoms in the surface skins. The coordination number imperfection in the surface skin leads spontaneous bond length contraction and bond energy strengthening. This causes densification and localization of charge, energy, mass at surface region, and hence modifies atomic coherency, Hamiltonian, etc. By extending the BOLS correlation mechanism to temperature domain, an approach of local bond average (LBA) has been developed in this thesis, which states that: (i) the entire specimen or a specific location of a specimen can be represented by a representative bond; (ii) the detectable quantity of a specimen can be obtained once the relationship between this detectable quantity and the bond identities (bond order, nature, length, and strength) of the representative bond and the response of these bond identities to the stimulus is established. This thesis discusses the size and temperature dependent elastic, lattice vibronic,and thermal properties of various materials. Deeper insight into the mechanism behind the size and temperature dependence together with analytical solutions is presented. Theoretical reproductions of experimental observations reveal that the surface coordination number imperfection induced spontaneous bond contraction and bond energy strengthening dictate the size-induced mechanical strength enhancement, optical Raman frequency redshift, and thermal conductivity variation; whereas the thermally-driven bond length expansion and bond energy weakening lead to mechanical strength depression, Raman frequency redshift, as well as surface energy reduction. Reproductions of size and temperature dependent Young’s modulus, Raman frequency shift, thermal expansion coefficient, thermal conductivity and surface energy for various materials, such as metals, group IV, group III-nitrides, and carbon based materials give quantitative information about the atomic cohesive energy and the dimer frequency, which is beyond the scope of currently available approaches in literature. Current progress in BOLS correlation and LBA approximation could pave a path to bridge the gap between the classical approach in macroscopic system and the quantum confinement approach in atomic level by considering the interatomic bond formation, dissociation, relaxation, vibration and associated energetic response of corresponding atoms and electrons and the consequences on the measurable quantities.DOCTOR OF PHILOSOPHY (EEE

Harnessing the Power of Stem Cell Models to Study Shared Genetic Variants in Congenital Heart Diseases and Neurodevelopmental Disorders

Advances in human pluripotent stem cell (hPSC) technology allow one to deconstruct the human body into specific disease-relevant cell types or create functional units representing various organs. hPSC-based models present a unique opportunity for the study of co-occurring disorders where “cause and effect” can be addressed. Poor neurodevelopmental outcomes have been reported in children with congenital heart diseases (CHD). Intuitively, abnormal cardiac function or surgical intervention may stunt the developing brain, leading to neurodevelopmental disorders (NDD). However, recent work has uncovered several genetic variants within genes associated with the development of both the heart and brain that could also explain this co-occurrence. Given the scalability of hPSCs, straightforward genetic modification, and established differentiation strategies, it is now possible to investigate both CHD and NDD as independent events. We will first overview the potential for shared genetics in both heart and brain development. We will then summarize methods to differentiate both cardiac & neural cells and organoids from hPSCs that represent the developmental process of the heart and forebrain. Finally, we will highlight strategies to rapidly screen several genetic variants together to uncover potential phenotypes and how therapeutic advances could be achieved by hPSC-based models