Equilibration of High Molecular-Weight Polymer Melts: A Hierarchical Strategy

A strategy is developed for generating equilibrated high molecular-weight polymer melts described with microscopic detail by sequentially backmapping coarse-grained (CG) configurations. The microscopic test model is generic but retains features like hard excluded volume interactions and realistic melt densities. The microscopic representation is mapped onto a model of soft spheres with fluctuating size, where each sphere represents a microscopic subchain with $N_{\rm b}$ monomers. By varying $N_{\rm b}$ a hierarchy of CG representations at different resolutions is obtained. Within this hierarchy, CG configurations equilibrated with Monte Carlo at low resolution are sequentially fine-grained into CG melts described with higher resolution. A Molecular Dynamics scheme is employed to slowly introduce the microscopic details into the latter. All backmapping steps involve only local polymer relaxation thus the computational efficiency of the scheme is independent of molecular weight, being just proportional to system size. To demonstrate the robustness of the approach, microscopic configurations containing up to $n=1000$ chains with polymerization degrees $N=2000$ are generated and equilibration is confirmed by monitoring key structural and conformational properties. The extension to much longer chains or branched polymers is straightforward

Ecological restoration and environmental philosophy: International visitor experiences at Aotearoa (New Zealand) eco-sanctuaries

Ecological restoration projects have been developed in various regions in Aotearoa (New Zealand) to address biodiversity loss and to provide human-assisted recovery of damaged, destroyed and degraded ecosystems. While the success of the ecological restoration is primarily assessed in terms of the science of ecology, it is also dependent on sustained social and economic support. Human values and action profoundly shape the implementation and success of ecological restoration projects. Societal discourses relating to ecological restoration are important to an extent that demands rigorous social science insights. Tourism provides biodiversity conservation and ecological restoration with both economic justification and opportunities arising from human-nature experiences. Nevertheless, the intersection of ecological restoration and the social sciences is largely overlooked in rigorous academic studies. In Aotearoa, a number of eco-sanctuaries have set out to develop tourism to financially support their primary function of ecological restoration. The development of these projects is mainly in response to New Zealand’s biodiversity crisis which has been historically driven by the ravages of introduced alien (exotic) species. Accordingly, eco-sanctuaries are predominantly characterized by intensive eradication and control of invasive alien species, and the translocation and breeding of endangered native species. These aspects of ecological intervention and management raise a number of complex moral and ethical issues that are poorly understood. Although tourism is argued to bring both opportunities and challenges to the development of eco-sanctuaries, little is known about eco-sanctuary visitors and their experiences at these sites. This thesis examines social perceptions of ecological restoration and considers their implications for visitor experiences in mainland eco-sanctuaries. The thesis focuses on international visitors and eco-sanctuary stakeholders, employing theories of environmental philosophy, including environmental ethics and aesthetics, in order to achieve in-depth insights into how aspects of ecological restoration are perceived and understood by different actors. Guided by social constructionism, the thesis uses a case study approach at three mainland eco-sanctuaries, using qualitative methods including photo-elicitation and flash interviews, combined with a comprehensive programme of semi-structured interviews. The thesis provides empirical evidence of the multiple meanings of ecological restoration by international visitors. It finds that international visitor perceptions of ecological restoration reflect disparate biodiversity interpretations and contrasting conservation narratives which inform potentially polarising visitor experiences at New Zealand eco-sanctuaries. At a deeper level, the thesis uncovers the critical roles of environmental ethics and knowledge and awareness in shaping distinct individual perceptions of ecological restoration. These perceptions cast light upon sharp distinctions and subtle nuances between the eco-sanctuary experiences among international visitors. The thesis also reveals a wide range of perceptions of ecological restoration and tourism held by eco-sanctuary stakeholders. Informed by these insights, the philosophies of eco-sanctuary stakeholders can either challenge visitors to reflect upon their ecological perspectives or pay increased attention to visitor interests and accommodate diverse perspectives in the provision of the tourist experience. The different philosophies of eco-sanctuary stakeholders may offer valuable insights into the co-creation of diverse international visitor experiences at New Zealand eco-sanctuaries. Through addressing several significant gaps in the existing literature, the thesis responds to calls to advance the social sciences of ecological restoration through the development of relevant tourism knowledge. Furthermore, it complements and extends current research on environmental and conservation narratives in Aotearoa by highlighting contrasting tourist narratives. The thesis empirically advances the transdisciplinary agenda of tourism and environmental philosophy by adding new understandings of environmental ethics and aesthetics on both the supply and demand sides of tourism. Two empirically informed conceptual frameworks are presented and discussed to cast light upon (co-created) visitor experiences that are produced by key actors and consumed by international visitors at mainland eco-sanctuaries in Aotearoa. Given that ecological restoration projects and tourism have been increasingly connected at a global scale, the thesis also provides valuable information for international audiences through building emerging theory which clarifies the relationship between international visitor experiences and perceptions of ecological restoration

Organic Sulphur Transfers in Coke Oven Gas via Noncatalytic Partial Oxidation

The organic sulfur transformation was studied during coke oven gas to produce syngas via noncatalytic partial oxidation. The concentration of CS2 and thiophene was examined in syngas by sulfide detector. For comparison, the sulfur transfer was also studied in coke oven gas under dry and hydrous conditions. When the ratio of O2 / Gas was 0.32, complete thiophene and about 83% of CS2 in feed gas could be transformed via noncatalytic partial oxidation in the dry condition. It was mainly because of burner nozzle unique structure forming local hyperthemia, which benefited OH, O free radical and active atoms. During steam transforming to produce syngas, the ratio of water to carbon was less than 3, a higher ratio of O2/Gas favored sulfur transformation. However, compared to dry feed, transforming rate of CS2 and thiophene was decreased. This indicates that the steam added was disadvantageous to the transformation of organic sulphur during the production of syngas by noncatalytic partial oxidation, steam and mass H2S in feed gas, resulting in the decrease of local hyperthermia temperature and the formation of organic sulfu

Improving the ostrich genome assembly using optical mapping data

BACKGROUND: The ostrich (Struthio camelus) is the tallest and heaviest living bird. Ostrich meat is considered a healthy red meat, with an annual worldwide production ranging from 12,000 to 15,000 tons. As part of the avian phylogenomics project, we sequenced the ostrich genome for phylogenetic and comparative genomics analyses. The initial Illumina-based assembly of this genome had a scaffold N50 of 3.59 Mb and a total size of 1.23 Gb. Since longer scaffolds are critical for many genomic analyses, particularly for chromosome-level comparative analysis, we generated optical mapping (OM) data to obtain an improved assembly. The OM technique is a non-PCR-based method to generate genome-wide restriction enzyme maps, which improves the quality of de novo genome assembly. FINDINGS: In order to generate OM data, we digested the ostrich genome with KpnI, which yielded 1.99 million DNA molecules (>250 kb) and covered the genome at least 500×. The pattern of molecules was subsequently assembled to align with the Illumina-based assembly to achieve sequence extension. This resulted in an OM assembly with a scaffold N50 of 17.71 Mb, which is 5 times as large as that of the initial assembly. The number of scaffolds covering 90% of the genome was reduced from 414 to 75, which means an average of ~3 super-scaffolds for each chromosome. Upon integrating the OM data with previously published FISH (fluorescence in situ hybridization) markers, we recovered the full PAR (pseudoatosomal region) on the ostrich Z chromosome with 4 super-scaffolds, as well as most of the degenerated regions. CONCLUSIONS: The OM data significantly improved the assembled scaffolds of the ostrich genome and facilitated chromosome evolution studies in birds. Similar strategies can be applied to other genome sequencing projects to obtain better assemblies

Track-before-detect Algorithm based on Cost-reference Particle Filter Bank for Weak Target Detection

Detecting weak target is an important and challenging problem in many applications such as radar, sonar etc. However, conventional detection methods are often ineffective in this case because of low signal-to-noise ratio (SNR). This paper presents a track-before-detect (TBD) algorithm based on an improved particle filter, i.e. cost-reference particle filter bank (CRPFB), which turns the problem of target detection to the problem of two-layer hypothesis testing. The first layer is implemented by CRPFB for state estimation of possible target. CRPFB has entirely parallel structure, consisting amounts of cost-reference particle filters with different hypothesized prior information. The second layer is to compare a test metric with a given threshold, which is constructed from the output of the first layer and fits GEV distribution. The performance of our proposed TBD algorithm and the existed TBD algorithms are compared according to the experiments on nonlinear frequency modulated (NLFM) signal detection and tracking. Simulation results show that the proposed TBD algorithm has better performance than the state-of-the-arts in detection, tracking, and time efficiency

Fast Exact NPN Classification with Influence-aided Canonical Form

NPN classification has many applications in the synthesis and verification of digital circuits. The canonical-form-based method is the most common approach, designing a canonical form as representative for the NPN equivalence class first and then computing the transformation function according to the canonical form. Most works use variable symmetries and several signatures, mainly based on the cofactor, to simplify the canonical form construction and computation. This paper describes a novel canonical form and its computation algorithm by introducing Boolean influence to NPN classification, which is a basic concept in analysis of Boolean functions. We show that influence is input-negation-independent, input-permutation-dependent, and has other structural information than previous signatures for NPN classification. Therefore, it is a significant ingredient in speeding up NPN classification. Experimental results prove that influence plays an important role in reducing the transformation enumeration in computing the canonical form. Compared with the state-of-the-art algorithm implemented in ABC, our influence-aided canonical form for exact NPN classification gains up to 5.5x speedup.Comment: To be appeared in ICCAD'2