Investigation of a square-based pyramidal-sheet roof

Imperial Users onl

Molecular-level organization of coassembled β-sheet peptide nanofibers

Functional biomaterials that recapitulate the complexity and sophistication of biological systems can be difficult to access given current techniques. One promising route towards building biomaterials with controlled nanoscale organization is coassembling β-sheet peptides. Coassembling β-sheet peptide designs are predominated by the concept of charge complementarity in which the two peptide sequences are modified to include charged amino acids giving rise to either an overall positive or overall negative charge. Electrostatic repulsion prevents self-assembly while attraction between oppositely charged peptides promotes β-sheet assembly. While previous studies have assessed the secondary structure of nanofibers fabricated from charge-complementary peptides, there is no detailed molecular-level description of how these peptides strands arrange within the nanofiber. Consequently, we lack an understanding of how these peptides coassemble and how to design the sequences to form a specific coassembled structure. In this thesis, we investigate the molecular-level organization within coassembling β-sheet peptide nanofibers by a combination of experimental and computational techniques. Results reveal a significant number of structural defects are formed highlighting the challenge in designing coassembling β-sheet peptides and providing insights into future designs.Ph.D

Time-Periodic Solutions of the Einstein's Field Equations II

In this paper, we construct several kinds of new time-periodic solutions of the vacuum Einstein's field equations whose Riemann curvature tensors vanish, keep finite or take the infinity at some points in these space-times, respectively. The singularities of these new time-periodic solutions are investigated and some new physical phenomena are found. The applications of these solutions in modern cosmology and general relativity can be expected.Comment: 10 pages, 1 figur

RON: Reverse Connection with Objectness Prior Networks for Object Detection

We present RON, an efficient and effective framework for generic object detection. Our motivation is to smartly associate the best of the region-based (e.g., Faster R-CNN) and region-free (e.g., SSD) methodologies. Under fully convolutional architecture, RON mainly focuses on two fundamental problems: (a) multi-scale object localization and (b) negative sample mining. To address (a), we design the reverse connection, which enables the network to detect objects on multi-levels of CNNs. To deal with (b), we propose the objectness prior to significantly reduce the searching space of objects. We optimize the reverse connection, objectness prior and object detector jointly by a multi-task loss function, thus RON can directly predict final detection results from all locations of various feature maps. Extensive experiments on the challenging PASCAL VOC 2007, PASCAL VOC 2012 and MS COCO benchmarks demonstrate the competitive performance of RON. Specifically, with VGG-16 and low resolution 384X384 input size, the network gets 81.3% mAP on PASCAL VOC 2007, 80.7% mAP on PASCAL VOC 2012 datasets. Its superiority increases when datasets become larger and more difficult, as demonstrated by the results on the MS COCO dataset. With 1.5G GPU memory at test phase, the speed of the network is 15 FPS, 3X faster than the Faster R-CNN counterpart.Comment: Project page will be available at https://github.com/taokong/RON, and formal paper will appear in CVPR 201

Exploring Mechanisms Underlying Extinction of Cue-Elicited Cocaine Seeking

A prominent feature of drug addiction is that drug-associated cues can elicit drug-seeking behaviors and contribute significantly to the high propensity to relapse. We have been investigating the notion that the dopamine D1 receptor and the immediate early gene product c-Fos expressed in D1 receptor-bearing neurons mediate the development of persistent neuroadaptation in the brain dopamine system by regulating cell signaling and gene expression. We generated and analyzed genetically engineered mouse models and found that the D1 receptor and c-Fos expressed in D1 receptor-bearing neurons mediate the locomotor sensitization and reinforcing effects of cocaine. Moreover, these molecules regulate cocaine-induced dendritic remodeling, electrophysiological responses, and changes in cell signaling and gene expression in the brain. Notably, a lack of Fos expression in D1 receptor-bearing neurons in mice results in no change in the induction but a significantly delayed extinction of cocaine-induced conditioned place preference. These findings suggest that D1 receptor-mediated and c-Fos-regulated changes in cell signaling and gene expression may play key roles in the extinction process, and they provide a foundation for further exploring mechanisms underlying extinction of cue-elicited cocaine seeking