First-principles Modeling of the Surface Reactivity of Transition Metals with Perturbed Electronic Properties

The surface reactivity of transition metals can be varied substantially by introducing perturbations into the electronic system. Previously, the electronic properties of transition metal surfaces have been tailored for improved catalytic performance compared to pure metals. However, the immense phase space of catalytic materials spanned by electronic and structural degrees of freedom precludes thorough screening, even with combinatorial high-throughput experiments or quantum-chemical calculations. The ultimate objective of fundamental research in heterogeneous catalysis is the development of physically transparent, yet sufficiently accurate models for designing catalytic active sites which can perform desired chemical transformations with utmost energy efficiency and minimal environmental impact. The critical question we attempt to answer in this dissertation is: How does a perturbation of surface electronic properties affect the energetics for elementary reaction steps? To tackle this question, we have developed a general theoretical framework, based on the basic principles of electronic structure theory, providing a fundamental basis for the understanding of variations in the surface reactivity of transition metals with perturbed electronic properties. The implications of the theoretical framework for unravelling the physical factors governing the energetics for elementary reaction steps on metal surfaces and eventually for rational catalyst design are discussed. By utilizing various theoretical tools, mainly Density Functional Theory calculations and Monte Carlo simulations, supported with experimental measurements, we have elaborated the fundamental mechanism of variations in the surface reactivity of transition metals with tailored electronic properties in three different applications: (i) rapid screening of multimetallic electrocatalysts for the oxygen reduction reaction in fuel cells; (ii) understanding of alkali promotion mechanisms for chemical reactions on metal surfaces; (iii) coupling of phonons and energetic electrons for chemical transformations on metallic nanoparticles. Each model system is characterized by one specific type of perturbation introduced by alloying with impurity elements, doping of substrates with chemical promoters, or imposing stimuli for electronic excitations. Many of the concepts developed in these studies can be readily transferable to other types of catalytic materials.Ph.D.Chemical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/89655/1/hxin_1.pd

Preparation and Characterization of Epitope-Based Ratiometric Fluorescent Molecularly Imprinted Polymers

In order to solve the problem of difficult detection of neuronal nitric oxide synthase in the screening of neuronal nitric oxide synthase-postsynaptic density95 (nNOS-PSD95) uncoupling agent, this study used 133 amino acids (nNOS1-133) at the nitrogen terminal of nNOS as template molecules, carbon dots and quantum dots as ratio fluorescence recognition elements, SiO2 as matrix for the first time, combined with surface molecular imprinting technology and antigen-determining principle, to prepare ratiometric flurescent molecularly imprinted polymers (RFMIPs). The resulting RFMIPs were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis，exhibiting uniform spherical morphology, which unambiguously confirmed the successful formation of the nanosensor. The result indicates that the synthesized sensors have promising potential for the assay of trace peptides in complex matrices

Efficient Screening of nNOS-PSD95 Uncoupling Agents Based on Radiometric Fluorescent Molecularly Imprinted Sensors

Novel and efficient ratiometric fluorescent molecularly imprinted sensors (RFMIS) based on epitopes were developed, which can be used for the sensitive detection of neuronal nitric oxide synthase in the screening of neuronal nitric oxide synthase-postsynaptic density95 (nNOS-PSD95) coupling inhibitors. Under appropriate conditions, the fluorescence of the carbon dots quenched with the increasing concentration of nNOS1-133, while the fluorescence of the quantum dots remained unchanged. The fluorescence ratio had a good linearity in the concentration range of 0-500 ng mL-1 for nNOS1-133 and the determination limit was 0.14 ng mL-1. Using the classical nNOS-PSD95 coupling inhibitor (ZL006) as a control, the RFMIS were used as the detector to detect the free nNOS released by Gnetol and 2,3,5,4ʹ-tetrahydroxystilbene-2-O-β-Dglucoside from natural medicine after inhibition of nNOS-PSD95. The results have shown that the uncoupling efficiencies was consistent with co-immunoprecipitation experiments. The study provides a new idea and a new way for efficient screening of nature nNOS-PSD95 coupling inhibitors from natural medicine with the advantages of high efficiency, sensitivity and traceability

Improving Fine-grained Entity Typing with Entity Linking

Fine-grained entity typing is a challenging problem since it usually involves a relatively large tag set and may require to understand the context of the entity mention. In this paper, we use entity linking to help with the fine-grained entity type classification process. We propose a deep neural model that makes predictions based on both the context and the information obtained from entity linking results. Experimental results on two commonly used datasets demonstrates the effectiveness of our approach. On both datasets, it achieves more than 5\% absolute strict accuracy improvement over the state of the art.Comment: EMNLP 201

Ultra-broadband and compact 2×\times2 3-dB silicon adiabatic coupler based on supermode-injected adjoint shape optimization

The 2$\times$2 3-dB couplers are one of the most widely used and important components in silicon photonics. We propose an ultra-broadband and compact 2$\times$2 3-dB adiabatic coupler defined by b-splines and optimized with an efficient supermode-injected adjoint shape optimization. By employing mode adiabatic evolution and mode coupling at two different wavelength ranges, respectively, we achieve an ultra-broad bandwidth of 530 nm from 1150nm to1680nm with a power imbalance below $\pm$0.76 dB in a compact coupling length of 30 $\mu m$ according to our simulation results. The supermode-injected adjoint shape optimization can also be applied to the design of other photonic devices based on supermode manipulation

Mathematical Modeling and Intelligent Algorithm for Multirobot Path Planning

10.1155/2017/1465158Mathematical Problems in Engineering2017146515