Slow-Roll Inflation Preceded by a Topological Defect Phase \`a la Chaplygin Gas

We present a simple toy model corresponding to a network of frustrated topological defects of domain walls or cosmic strings that exist previous to the standard slow-roll inflationary era of the universe. Such a network (i) can produce a slower inflationary era than that of the standard scenario if it corresponds to a network of frustrated domain walls or (ii) can induce a vanishing universal acceleration; i.e., the universe would expand at a constant speed, if it corresponds to a network of frustrated cosmic strings red. Those features are phenomenologically modeled by a Chaplygin gas that can interpolate between a network of frustrated topological defects and a de Sitter-like or a power-law inflationary era. We show that this scenario can alleviate the quadruple anomaly of the cosmic microwave background spectrum. Using the method of the Bogoliubov coefficients, we obtain the spectrum of the gravitational waves as would be measured today for the whole range of frequencies. We comment on the possible detection of this spectrum by the planned detectors like BBO and DECIGO.Comment: 11 pages, 12 figures. RevTex4-1. Expanded discussion. Version accepted in PR

Computation-Performance Optimization of Convolutional Neural Networks with Redundant Kernel Removal

Deep Convolutional Neural Networks (CNNs) are widely employed in modern computer vision algorithms, where the input image is convolved iteratively by many kernels to extract the knowledge behind it. However, with the depth of convolutional layers getting deeper and deeper in recent years, the enormous computational complexity makes it difficult to be deployed on embedded systems with limited hardware resources. In this paper, we propose two computation-performance optimization methods to reduce the redundant convolution kernels of a CNN with performance and architecture constraints, and apply it to a network for super resolution (SR). Using PSNR drop compared to the original network as the performance criterion, our method can get the optimal PSNR under a certain computation budget constraint. On the other hand, our method is also capable of minimizing the computation required under a given PSNR drop.Comment: This paper was accepted by 2018 The International Symposium on Circuits and Systems (ISCAS

Designing Visible Light-Cured Thiol-Acrylate Hydrogels for Studying the HIPPO Pathway Activation in Hepatocellular Carcinoma Cells

Various polymerization mechanisms have been developed to prepare peptide-immobilized poly(ethylene glycol) (PEG) hydrogels, a class of biomaterials suitable for studying cell biology in vitro. Here, a visible light mediated thiol-acrylate photopolymerization scheme is reported to synthesize dually degradable PEG-peptide hydrogels with controllable crosslinking and degradability. The influence of immobilized monothiol pendant peptide is systematically evaluated on the crosslinking of these hydrogels. Further, methods are proposed to modulate hydrogel crosslinking, including adjusting concentration of comonomer or altering the design of multifunctional peptide crosslinker. Due to the formation of thioether ester bonds, these hydrogels are hydrolytically degradable. If the dithiol peptide linkers used are susceptible to protease cleavage, these thiol-acrylate hydrogels can be designed to undergo partial proteolysis. The differences between linear and multiarm PEG-acrylate (i.e., PEGDA vs PEG4A) are also evaluated. Finally, the use of the mixed-mode thiol-acrylate PEG4A-peptide hydrogels is explored for in situ encapsulation of hepatocellular carcinoma cells (Huh7). The effects of matrix stiffness and integrin binding motif (e.g., RGDS) on Huh7 cell growth and HIPPO pathway activation are studied using PEG4A-peptide hydrogels. This visible light poly-merized thiol-acrylate hydrogel system represents an alternative to existing light-cured hydrogel platforms and shall be useful in many biomedical applications