Dynamical Linear Response of TDDFT with LDA+U Functional: strongly hybridized Frenkel excitons in NiO

Within the framework of time-dependent density-functional theory (TDDFT), we derive the dynamical linear response of LDA+U functional and benchmark it on NiO, a prototypical Mott insulator. Formulated using real-space Wannier functions, our computationally inexpensive framework gives detailed insights into the formation of tightly bound Frenkel excitons with reasonable accuracy. Specifically, a strong hybridization of multiple excitons is found to significantly modify the exciton properties. Furthermore, our study exposes a significant generic limitation of adiabatic approximation in TDDFT with hybrid functionals and in existing Bethe-Salpeter-equation approaches, advocating the necessity of strongly energy-dependent kernels in future development.Comment: 5 pages, 2 figure

High-Energy String Scattering Amplitudes and Signless Stirling Number Identity

We give a complete proof of a set of identities (7) proposed recently from calculation of high-energy string scattering amplitudes. These identities allow one to extract ratios among high-energy string scattering amplitudes in the fixed angle regime from high-energy amplitudes in the Regge regime. The proof is based on a signless Stirling number identity in combinatorial theory. The results are valid for arbitrary real values $L$ rather than only for $L=0,1$ proved previously. The identities for non-integer real value $L$ were recently shown to be realized in high-energy compactified string scattering amplitudes [He S., Lee J.C., Yang Y., arXiv:1012.3158]. The parameter $L$ is related to the mass level of an excited string state and can take non-integer values for Kaluza-Klein modes

Nasal septal perforation repair with an inferior turbinate flap and acellular dermal matrix

Nasal septal perforation is an uncommon disorder that can cause disturbance of nasal physiology. The perforations can vary widely in size, location, and symptomatology. Many different closure techniques have been described in the literature; however, no gold standard has been recognized. The choice of surgical technique usually depends on the characteristics of the perforation and surgeon experience. Due to the goal of perforation repair being restoration of normal nasal physiology, techniques with the best outcomes have been those resurfacing the septum with nasal respiratory mucosa. Here we present our novel surgical method for large (\u3e 2 cm) septal perforation closure using a modification of the inferior turbinate flap repair using a polydioxanone plate and the acellular dermal matrix allograft (Alloderm, Allergan Inc.)

Crosslinking-induced endocytosis of acetylcholine receptors by quantum dots

In a majority of patients with myasthenia gravis (MG), anti-acetylcholine receptor (AChR) antibodies target postsynaptic AChR clusters and thus compromise the membrane integrity of neuromuscular junctions (NMJs) and lead to muscle weakness. Antibody-induced endocytosis of AChRs in the postsynaptic membrane represents the initial step in the pathogenesis of MG; however, the molecular mechanisms underlying AChR endocytosis remain largely unknown. Here, we developed an approach to mimic the pathogenic antibodies for inducing the crosslinking and internalization of AChRs from the postsynaptic membrane. Using biotin-α-bungarotoxin and quantum dot (QD)-streptavidin, cell-surface and internalized AChRs could be readily distinguished by comparing the size, fluorescence intensity, trajectory, and subcellular localization of the QD signals. QD-induced AChR endocytosis was mediated by clathrin-dependent and caveolin-independent mechanisms, and the trafficking of internalized AChRs in the early endosomes required the integrity of microtubule structures. Furthermore, activation of the agrin/MuSK (muscle-specific kinase) signaling pathway strongly suppressed QD-induced internalization of AChRs. Lastly, QD-induced AChR crosslinking potentiated the dispersal of aneural AChR clusters upon synaptic induction. Taken together, our results identify a novel approach to study the mechanisms of AChR trafficking upon receptor crosslinking and endocytosis, and demonstrate that agrin-MuSK signaling pathways protect against crosslinking-induced endocytosis of AChRs. © 2014 Lee et al.published_or_final_versio

Smart Cardiovascular Stent against In-Stent Restenosis

Jump Starting Technologies, Patent Issues, & Translational Medicine Poster SessionA smart cardiovascular stent to be used as a single set of theranostics (therapeutics and diagnostics) is developed. The stent is aimed at delivering nitric oxide as a therapeutic agent and monitoring stent-induced restenosis. This novel approach is intended to reduce the risks stemmed from implanted stents and lowering manufacturing cost. The proposed stent will provide a non-invasive and continuous monitoring of restenosis caused by the stent. To assess the level of restenosis, pressure and blood flow will be monitored inside the blood vessel where the stent is placed. Existing techniques that employ catheters to measure pressure inside blood vessels are not suitable because they are too invasive, cannot monitor pressure for long periods of time and restrict the patient to be in a hospital setting. Our approach consists of two miniature pressure sensors and a small microchip incorporated into the stent. The pressure sensors are placed at the opposite sides of the stent. Blood flow is obtained by assessing the pressure difference at these two points. The microchip reads out the pressure sensors outputs and wirelessly transmits them to a reader outside the body. Due to size constraints and safety reasons a battery cannot be used as a power source for the microchip. Instead, power is provided from the reader via electromagnetic coupling. In order to reduce the number of components to be implanted, we are proposing to employ the stent body not only as a mechanical supporter but also as an antenna. To provide an optimal power match between the microchip and the antenna, the impedance of the stent was fully characterized. This characterization has been performed using computer simulations of five different commercially available stent designs. It was found that at the frequencies of interest (902 to 928 MHz) the impedance is highly reactive. To compensate for the reactive impedance of the antenna, a matching network was designed. A prototype microchip with different components has been designed and is currently being fabricated. Future work includes micro-assembly of a prototype stent for the collection of pressure measurements using an aortic bifurcation model. Once completed, this stent will be useful in monitoring the level of restenosis and will lower the risks presented by implantable stents

First-principles method of propagation of tightly bound excitons: exciton band structure of LiF and verification with inelastic x-ray scattering

We propose a simple first-principles method to describe propagation of tightly bound excitons. By viewing the exciton as a composite object (an effective Frenkel exciton in Wannier orbitals), we define an exciton kinetic kernel to encapsulate the exciton propagation and decay for all binding energy. Applied to prototypical LiF, our approach produces three exciton bands, which we verified quantitatively via inelastic x-ray scattering. The proposed real-space picture is computationally inexpensive and thus enables study of the full exciton dynamics, even in the presence of surfaces and impurity scattering. It also provides intuitive understanding to facilitate practical exciton engineering in semiconductors, strongly correlated oxides, and their nanostructures.Comment: 5 pages, 4 figures. Accepted by PR

Robust pinning of magnetic moments in pyrochlore iridates

Pyrochlore iridates A2Ir2O7 (A = rare earth elements, Y or Bi) hold great promise for realizing novel electronic and magnetic states owing to the interplay of spin-orbit coupling, electron correlation and geometrical frustration. A prominent example is the formation of all-in/all-out (AIAO)antiferromagnetic order in the Ir4+ sublattice that comprises of corner-sharing tetrahedra. Here we report on an unusual magnetic phenomenon, namely a cooling-field induced shift of magnetic hysteresis loop along magnetization axis, and its possible origin in pyrochlore iridates with non-magnetic Ir defects (e.g. Ir3+). In a simple model, we attribute the magnetic hysteresis loop to the formation of ferromagnetic droplets in the AIAO antiferromagnetic background. The weak ferromagnetism originates from canted antiferromagnetic order of the Ir4+ moments surrounding each non-magnetic Ir defect. The shift of hysteresis loop can be understood quantitatively based on an exchange-bias like effect in which the moments at the shell of the FM droplets are pinned by the AIAO AFM background via mainly the Heisenberg (J) and Dzyaloshinsky-Moriya (D) interactions. The magnetic pinning is stable and robust against the sweeping cycle and sweeping field up to 35 T, which is possibly related to the magnetic octupolar nature of the AIAO order.Comment: 16 pages, 4 figure

Computational analysis and predictive modeling of polymorph descriptors

Abstract Background A computation approach based on integrating high throughput binding affinity comparison and binding descriptor classifications was utilized to establish the correlation among substrate properties and their affinity to Breast Cancer Resistant Protein (BCRP). The uptake rates of Mitoxantrone in the presence of various substrates were evaluated as an in vitro screening index for comparison of their binding affinity to BCRP. The effects of chemical properties of various chemotherapeutics, such as antiviral, antibiotic, calcium channel blockers, anticancer and antifungal agents, on their affinity to BCRP, were evaluated using HEK (human embryonic kidney) cells in which 3 polymorphs, namely 482R (wild type) and two mutants (482G and 482T) of BCRP, have been identified. The quantitative structure activity relationship (QSAR) model was developed using the sequential approaches of Austin Model 1 (AM1), CODESSA program, heuristic method (HM) and multiple linear regression (MLR) to establish the relationship between structural specificity of BCRP substrates and their uptake rates by BCRP polymorphs. Results The BCRP mutations may induce conformational changes as manifested by the altered uptake rates of Mitoxantrone by BCRP in the presence of other competitive binding substrates that have a varying degree of affinities toward BCRP efflux. This study also revealed that the binding affinity of test substrates to each polymorph was affected by varying descriptors, such as constitutional, topological, geometrical, electrostatic, thermodynamic, and quantum chemical descriptors. Conclusion Descriptors involved with the net surface charge and energy level of substrates seem to be the common integral factors for defining binding specificity of selected substrates to BCRP polymorph. The reproducible outcomes and validation process further supported the accuracy of the computational model in assessing the correlation among descriptors involved with substrate affinity to BCRP polymorph. A quantitative computation approach will provide important structural insight into optimal designing of new chemotherapeutic agents with improved pharmacological efficacies.Peer Reviewe

Enhancement of service life of polymer electrolyte fuel cells through application of nanodispersed ionomer

Copyright © 2020 The Authors, some rights reserved.In polymer electrolyte fuel cells (PEFCs), protons from the anode are transferred to the cathode through the ionomer membrane. By impregnating the ionomer into the electrodes, proton pathways are extended and high proton transfer efficiency can be achieved. Because the impregnated ionomer mechanically binds the catalysts within the electrode, the ionomer is also called a binder. To yield good electrochemical performance, the binder should be homogeneously dispersed in the electrode and maintain stable interfaces with other catalyst components and the membrane. However, conventional binder materials do not have good dispersion properties. In this study, a facile approach based on using a supercritical fluid is introduced to prepare a homogeneous nanoscale dispersion of the binder material in aqueous alcohol. The prepared binder exhibited high dispersion characteristics, crystallinity, and proton conductivity. High performance and durability were confirmed when the binder material was applied to a PEFC cathode electrode11sciescopu