Constructions of Almost Optimal Resilient Boolean Functions on Large Even Number of Variables

In this paper, a technique on constructing nonlinear resilient Boolean functions is described. By using several sets of disjoint spectra functions on a small number of variables, an almost optimal resilient function on a large even number of variables can be constructed. It is shown that given any $m$, one can construct infinitely many $n$-variable ($n$ even), $m$-resilient functions with nonlinearity $>2^{n-1}-2^{n/2}$. A large class of highly nonlinear resilient functions which were not known are obtained. Then one method to optimize the degree of the constructed functions is proposed. Last, an improved version of the main construction is given.Comment: 14 pages, 2 table

Computational Studies of Chemical Systems: I. A Molecular Dynamics Simulation of Methane Hydrate; II. Theoretical Investigation of Water Loading on a Pyrophyllite (001) Surface

This dissertation consists of two independent parts: Part I. methane hydrate, and Part II. water loading on a clay surface. In Part I (chapter 2-3), we conducted molecular dynamics simulations with non-polarizable force fields to study structural and thermal properties of methane hydrate. We show that the TIP4P/Ice and TIP4P/2005 model potentials do well in the description of the lattice constant and radial distribution functions. Yet they, together with SPC/E and TIP4P models, overestimate the thermal expansion coefficient due to the inadequate description of the non-linear response of lattice constant to temperature. We also show that TIP4P/Ice and TIP4P/2005 overestimate the decomposition temperature of methane hydrate from the experimental value by 50 K and 30 K respectively, while SPC/E gives a good estimation deviating by about 5 K. All these force fields are found to overestimate the thermal conductivity of methane hydrate, but they are able to describe the weak temperature dependence from 100 to 150 K and 225 to 270 K. It is also found that all initial structures used in the work have a proton ordering tendency, suggesting a potential role of proton arrangement in the temperature dependence of the thermal conductivity. In part II (chapter 4), we conducted dispersion-corrected density function theory (DFT-D) and classical force field calculations to study the water loading on a pyrophyllite (001) surface. We disclose low-energy binding motifs from one water molecule to six water molecules and reinterpret the hydrophobic nature of the pyrophyllite surface from the point of view that a water molecule prefers to interact with other water molecules than to be bound on the surface. The force field approach, while providing a similar trend of the water binding to the DFT-D result, predicts some low-energy binding motifs which are not confirmed by the DFT-D calculation. It suggests a refinement of the force field to better describe the interfacial orientation of water on a clay surface

Carbon Monoxide Oxidation Promoted by Surface Polarization Charges in a CuO/Ag Hybrid Catalyst.

Composite structures have been widely utilized to improve material performance. Here we report a semiconductor-metal hybrid structure (CuO/Ag) for CO oxidation that possesses very promising activity. Our first-principles calculations demonstrate that the significant improvement in this system's catalytic performance mainly comes from the polarized charge injection that results from the Schottky barrier formed at the CuO/Ag interface due to the work function differential there. Moreover, we propose a synergistic mechanism underlying the recovery process of this catalyst, which could significantly promote the recovery of oxygen vacancy created via the M-vK mechanism. These findings provide a new strategy for designing high performance heterogeneous catalysts

Atomic-scale identification of novel planar defect phases in heteroepitaxial YBa2_2Cu3_3O7−δ_{7-\delta} thin films

We have discovered two novel types of planar defects that appear in heteroepitaxial YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO123) thin films, grown by pulsed-laser deposition (PLD) either with or without a La$_{2/3}$Ca$_{1/3}$MnO$_3$ (LCMO) overlayer, using the combination of high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging and electron energy loss spectroscopy (EELS) mapping for unambiguous identification. These planar lattice defects are based on the intergrowth of either a BaO plane between two CuO chains or multiple Y-O layers between two CuO$_2$ planes, resulting in non-stoichiometric layer sequences that could directly impact the high-$T_c$ superconductivity

Role of Hydrogen Bonding in Green Fluorescent Protein-like Chromophore Emission.

The fluorescence emission from green fluorescent protein (GFP) is known to be heavily influenced by hydrogen bonding between the core fluorophore and the surrounding side chains or water molecules. Yet how to utilize this feature for modulating the fluorescence of GFP chromophore or GFP-like fluorophore still remains elusive. Here we present theoretical calculations to predict how hydrogen bonding could influence the excited states of the GFP-like fluorophores. These studies provide both a new perspective for understanding the photophysical properties of GFP as well as a solid basis for the rational design of GFP-based fluorophores

Frontal EEG Asymmetry and Middle Line Power Difference in Discrete Emotions

A traditional model of emotion cannot explain the differences in brain activities between two discrete emotions that are similar in the valence-arousal coordinate space. The current study elicited two positive emotions (amusement and tenderness) and two negative emotions (anger and fear) that are similar in both valence and arousal dimensions to examine the differences in brain activities in these emotional states. Frontal electroencephalographic (EEG) asymmetry and midline power in three bands (theta, alpha and beta) were measured when participants watched affective film excerpts. Significant differences were detected between tenderness and amusement on FP1/FP2 theta asymmetry, F3/F4 theta and alpha asymmetry. Significant differences between anger and fear on FP1/FP2 theta asymmetry and F3/F4 alpha asymmetry were also observed. For midline power, midline theta power could distinguish two negative emotions, while midline alpha and beta power could effectively differentiate two positive emotions. Liking and dominance were also related to EEG features. Stepwise multiple linear regression results revealed that frontal alpha and theta asymmetry could predict the subjective feelings of two positive and two negative emotions in different patterns. The binary classification accuracy, which used EEG frontal asymmetry and midline power as features and support vector machine (SVM) as classifiers, was as high as 64.52% for tenderness and amusement and 78.79% for anger and fear. The classification accuracy was improved after adding these features to other features extracted across the scalp. These findings indicate that frontal EEG asymmetry and midline power might have the potential to recognize discrete emotions that are similar in the valence-arousal coordinate space