Geometric algorithms for modeling protein structures

Understanding the structures of macromolecular assemblies is necessary to describe the mechanics of a wide variety of cellular processes. Such assemblies often consist of hundreds of proteins and nucleic acid, each with a unique shape. Modern imaging techniques, including electron cryo-microscopy, create 3D density maps to portray the shapes of these assemblies. However, computational methods for deriving structural models from these images are not fully developed because structural geometry varies depending on the image resolution. To address this issue, we developed geometric algorithms in Gorgon, a molecular visualization software. First, we created an interface for Pathwalking. This algorithm determines protein backbones by first creating a pre-determined number of pseudo-atoms at regions with high densities, then determining a path through these pseudo-atoms with a travelling-salesman heuristic. As long as structural features are resolvable, Pathwalking accurately constructs models even at resolutions as low 7-8 ̊A. Our interface allows for biomedical researchers to adjust parameters for an algorithm which was previously restricted to the command line. To address the cases in which parameters for Pathwalking are not known and when maps are of higher resolution (\u3c5 \u3e̊A), we also developed Extremal Curve Skeletonization. Skeletonization uses the geometric profiles of locally maximal density curves and surfaces to identify α-helices and β-sheets. Such secondary structures (SSEs) play in pivotal role in protein interactions. We found that the SSEs which could be accurately obtained through skeletonization can be used as anchors for identifying the rest of the protein structure. Our future work involves creating algorithms that will detect the resolution and automatically adjust the algorithm accordingly. Such resolution-aware algorithms will reduce the labour involved in converting density maps into structural models and reduce the human bias that often results from this process

On the Education in The Catcher in the Rye From Perspectives of Family, School and Society

Among today’s intense international competition, human resource has exactly become the chief concern of the world comprehensive strength. And more and more attention is paid to education. However, while school education is valued, another two kinds of education are ignored, namely, family education and social education. Therefore, in order to bring the equally importance of them to people, this thesis tries to analyze The Catcher in the Rye from these three perspectives of education, and call on all of us to contribute to the cause of education

Dynamic asset allocation with uncertain jump risks : a pathwise optimization approach

This paper studies the dynamic portfolio choice problem with ambiguous jump risks in a multi-dimensional jump-diffusion framework. We formulate a continuous-time model of incomplete market with uncertain jumps. We develop an efficient pathwise optimization procedure based on the martingale methods and minimax results to obtain closed-form solutions for the indirect utility function and the probability of the worst scenario. We then introduce an orthogonal decomposition method for the multi-dimensional problem to derive the optimal portfolio strategy explicitly under ambiguity aversion to jump risks. Finally, we calibrate our model to real market data drawn from ten international indices and illustrate our results by numerical examples. The certainty equivalent losses affirm the importance of jump uncertainty in optimal portfolio choice

Research on the Quality Management Mechanism of Chinese Government Procurement of Public Services

The government meets the growing surge of social supply and demand through the purchase of public services from social organizations. Since the introduction of concept to China in the 1990s, government procurement of services has become one of the main ideas of public service reform; government procurement plays an increasingly important role in constructing a service-oriented government and improving public services. In recent years, China attaches a growing importance to the government procurement of public services and starts to reform the way, process and scope of government procurement of public services, and constantly improves quality control mechanisms of government procurement of public services. Based on a wide literature review of texts on the purchase of public services at home and abroad, this paper combines with the actual needs of our citizens and studies the quality control mechanisms of government procurement of public services

A survey of face recognition techniques under occlusion

The limited capacity to recognize faces under occlusions is a long-standing problem that presents a unique challenge for face recognition systems and even for humans. The problem regarding occlusion is less covered by research when compared to other challenges such as pose variation, different expressions, etc. Nevertheless, occluded face recognition is imperative to exploit the full potential of face recognition for real-world applications. In this paper, we restrict the scope to occluded face recognition. First, we explore what the occlusion problem is and what inherent difficulties can arise. As a part of this review, we introduce face detection under occlusion, a preliminary step in face recognition. Second, we present how existing face recognition methods cope with the occlusion problem and classify them into three categories, which are 1) occlusion robust feature extraction approaches, 2) occlusion aware face recognition approaches, and 3) occlusion recovery based face recognition approaches. Furthermore, we analyze the motivations, innovations, pros and cons, and the performance of representative approaches for comparison. Finally, future challenges and method trends of occluded face recognition are thoroughly discussed