Conditions for entanglement in multipartite systems

We introduce two entanglement conditions that take the form of inequalities involving expectation values of operators. These conditions are sufficient conditions for entanglement, that is if they are satisfied the state is entangled, but if they are not, one can say nothing about the entanglement of the state. These conditions are quite flexible, because the operators in them are not specified, and they are particularly useful in detecting multipartite entanglement. We explore the range of utility of these conditions by considering a number of examples of entangled states, and seeing under what conditions entanglement in them can be detected by the inequalities presented here.Comment: accepted for publication in Physical Review

Nutrient acquisition in a human gut symbiont : molecular analysis of the carbohydrate utilisation apparatus of Bacteroides thetaiotaomicron

The gut microbiota play a significant role in human health and nutrition, although the mechanisms these organisms use to survive in this densely populated environment are not well understood. Bacteroides thetaiotaomicron is a dominant member of the gut bacterial community whose genome sequence reveals large expansions in protein families involved in the sensing, acquisition and utilisation of complex carbohydrates, pointing to the ability to access a wide range of glycans as playing a significant role in becoming a successful resident of the human gut. Here we have characterised components of the B. thetaiotaomicron polysaccharide utilisation apparatus at molecular level, focusing mainly on fructan sensing, binding and degradation systems. Microarray data from our collaborators revealed that growth of B. thetaiotaomicron on inulin (β-2,1-linked fructan) specifically upregulated a locus of nine genes BT1757-BT1765 and an orphan gene BT3082, encoding a glycoside hydrolase from family 32 (GH32). The locus contains three other GH32s, two predicted polysaccharide binding outer membrane proteins (SusC and SusD homologues), a fructokinase, and an inner membrane monosaccharide transporter. Together these components form a polysaccharide utilisation locus (PUL). The nearest regulatory gene to the PUL is BT1754, a hybrid two component system. Here we show that the periplasmic sensor domain of BT1754 (BT1754peri) binds specifically to fructose, with a Kd of ~2 μM and a stoichiometry of 1:1, but not fructooligosaccharides or other monosaccharides. The crystal structure of BT1754peri revealed a two domain periplasmic binding protein (PBP)-fold with the ligand fructose sandwiched between the two domains. BT1754 is the first periplasmic sensor histidine kinase domain to display a non-PAS fold. The structure in combination with biophysical and site-directed mutagenesis studies also shows how the protein displays such specificity in ligand recognition and provides insights into the mechanism of signal transduction across the inner membrane. The four glycoside hydrolase family 32 members regulated by BT1754 were also biochemically and structurally characterised in this thesis. Three of four GH32 enzymes BT1759, BT1765 and BT3082, digest both β-2,1-linked (inulin) and β-2,6-linked (levan) fructans, indicating that levan is also utilised by the same locus. BT1759 and BT3082 are exo-acting enzymes releasing fructose from both long-chain and short-chain inulins and levans, while BT1765 is also exo-acting and produces fructose, but preferred short-chain sugars. BT1760 is unusual for GH32 as it is specific for levan and has an endo-like activity, releasing a range of different size oligosaccharides from the polysaccharide. The crystal structures of wild type BT3082 and a nucleophile mutant in complex with substrate (kestose) were solved to 2.2 Å and revealed a typical GH32 β-propeller fold as the catalytic domain. Like all other GH32s solved to date, the enzyme has a C-terminal β-sheet domain of unknown function that was shown to be necessary for correct folding of the enzyme. BT3082 also has a unique N-terminal β-sheet domain that was shown to be essential for enzyme activity but not correct folding. Extensive site-directed mutagenesis was carried out to provide insight into the relative importance of different residues in substrate binding and catalysis in BT3082. The crystal structure of wild type BT1760 was solved to 2.6 Å, revealing a surprisingly similar structure to that of the exo-acting enzymes. A rationale for the endo-like activity of this enzyme and the role each of the four GH32s in fructan utilisation by B. thetaiotaomicron is discussed. The outer membrane SusD homologue BT1762 from the fructan locus was shown to bind preferentially to long chain levans, with no recognition of inulin. The crystal structure of BT1762 was solved to 1.9 Å and was shown to share the same novel α-helical fold as SusD. Site-directed mutagenesis of a number of residues in the same region as the SusD binding site showed that while the location of the ligand binding sites are conserved between these two proteins, the identity of the residues involved in polysaccharide recognition are not the same. A model is proposed for levan recognition in BT1762 and also its role in polysaccharide utilisation. B. thetaiotaomicron also has at least 12 ECF sigma/anti-sigma factor gene pairs likely involved in polysaccharide utilisation. Here we show that these systems form a trans-envelope signalling apparatus with their cognate SusC-transducer homologue, but that there is no cross talk between different systems. The significance of this finding in relation to survival of this important gut bacterium is discussed.EThOS - Electronic Theses Online ServiceDorothy Hodgkin Postgraduate Awards : UK Government : Biotechnology and Biological Sciences Research Council : GlaxoSmithKlineGBUnited Kingdo

Quantum walks as a probe of structural anomalies in graphs

We study how quantum walks can be used to find structural anomalies in graphs via several examples. Two of our examples are based on star graphs, graphs with a single central vertex to which the other vertices, which we call external vertices, are connected by edges. In the basic star graph, these are the only edges. If we now connect a subset of the external vertices to form a complete subgraph, a quantum walk can be used to find these vertices with a quantum speedup. Thus, under some circumstances, a quantum walk can be used to locate where the connectivity of a network changes. We also look at the case of two stars connected at one of their external vertices. A quantum walk can find the vertex shared by both graphs, again with a quantum speedup. This provides an example of using a quantum walk in order to find where two networks are connected. Finally, we use a quantum walk on a complete bipartite graph to find an extra edge that destroys the bipartite nature of the graph.Comment: 10 pages, 2 figure

Análise de elasticidade para sistemas agrícolas da planície do norte da China baseada em um modelo dinâmico de sistema

Este trabalho se refere a um estudo de caso da teoria de elasticidade para entender sistemas agrícolas na província de Luancheng na planície do norte da China. Foi construído um modelo de sistema dinâmico acoplado a subsistemas agrícolas sociais, econômicos e ecológicos para a província de Luancheng com um intervalo de tempo de um mês. O modelo inclui cinco componentes principais: recursos hídricos, rentabilidade, irrigação, produção agrícola e área. O lençol freático simulado, a área e a produção de trigo, a área e produção de milho e a transferência de mão de obra refletiram a tendência geral dos resultados observados com coeficientes de determinação maiores que 0.88. A elasticidade dos sistemas agrícolas, indicada pela rentabilidade e segurança alimentar, foi explorada para a província de Luancheng, que mostrou que inicialmente os investimentos em agricultura tiveram sua elasticidade aumentada rapidamente. Entretanto, com a degradação dos recursos e o aumento do investimento agrícola, o custo da produção agrícola tornou-se muito alto para obtenção de lucro. O aumento de população aumenta o risco de segurança alimentar. Como resultado, a elasticidade dos sistemas agrícolas decresceu gradualmente. A província de Luancheng encontra-se agora na fase conservativa do ciclo de adaptação. Ajustes parciais deveriam ser implementados para impulsionar sua elasticidade e promover o desenvolvimento contínuo dos sistemas agrícolas.This paper presents a case study of resilience theory to understand agricultural systems in the Luancheng County of the North China Plain. A dynanic system model coupled with social, economic and ecological subsystems of agriculture for the Luancheng County was constructed with a time step of one month. The model includes five main components, water resources, profitability, irrigation, crop yield and area. The simulated groundwater table, wheat area and yield, maize area and yield, and rural labor transfer reflected the general trend of the observed data, with calculated determination coefficients higher than 0.88. Resilience of agricultural systems, as indicated by agricultural profitability and food security, were explored for the Luancheng County. Initially, investments in agriculture increased its resilience rapidly. However, with the degradation of resources and the increases in agricultural investment, the cost of agricultural production became too high to gain profit. The rise in population increases the risk of food security. As a result, the resilience of agricultural systems decreased gradually. The Luancheng County is now in the conservation phase of the adaptive cycle. Partial adjustments should be introduced to enhance its resilience and promote the continuing development of the agricultural systems

Navigating Beyond Dropout: An Intriguing Solution Towards Generalizable Image Super Resolution

Deep learning has led to a dramatic leap on Single Image Super-Resolution (SISR) performances in recent years. %Despite the substantial advancement% While most existing work assumes a simple and fixed degradation model (e.g., bicubic downsampling), the research of Blind SR seeks to improve model generalization ability with unknown degradation. Recently, Kong et al pioneer the investigation of a more suitable training strategy for Blind SR using Dropout. Although such method indeed brings substantial generalization improvements via mitigating overfitting, we argue that Dropout simultaneously introduces undesirable side-effect that compromises model's capacity to faithfully reconstruct fine details. We show both the theoretical and experimental analyses in our paper, and furthermore, we present another easy yet effective training strategy that enhances the generalization ability of the model by simply modulating its first and second-order features statistics. Experimental results have shown that our method could serve as a model-agnostic regularization and outperforms Dropout on seven benchmark datasets including both synthetic and real-world scenarios

Ice-templating of core/shell microgel fibers through 'Bricks-and-Mortar' assembly

通讯作者地址: Stucky, GD (通讯作者), Univ Calif Santa Barbara, Mat Res Lab, Dept Chem & Biochem, Santa Barbara, CA 93106 USA 地址: 1. Univ Calif Santa Barbara, Mat Res Lab, Dept Chem & Biochem, Santa Barbara, CA 93106 USA 电子邮件地址: [email protected] 'bricks-and-mortar' assembly approach can be used to create well-defined fibers on the microscale with alternating organic-inorganic arrangement through a simple ice-templating strategy. ne fibers are constructed from closely packed monodisperse inorganic nanoparticles@PNIPAm core/shelf microgels. A series of functional 'bricks', such as core/shell and hollow nanoparticles are prepared

Superior Self-Powered Room-Temperature Chemical Sensing with Light-Activated Inorganic Halides Perovskites

Hybrid halide perovskite is one of the promising light absorber and is intensively investigated for many optoelectronic applications. Here, the first prototype of a self-powered inorganic halides perovskite for chemical gas sensing at room temperature under visible-light irradiation is presented. These devices consist of porous network of CsPbBr3 (CPB) and can generate an open-circuit voltage of 0.87 V under visible-light irradiation, which can be used to detect various concentrations of O2 and parts per million concentrations of medically relevant volatile organic compounds such as acetone and ethanol with very quick response and recovery time. It is observed that O2 gas can passivate the surface trap sites in CPB and the ambipolar charge transport in the perovskite layer results in a distinct sensing mechanism compared with established semiconductors with symmetric electrical response to both oxidizing and reducing gases. The platform of CPB-based gas sensor provides new insights for the emerging area of wearable sensors for personalized and preventive medicine.H.C. and M.Z. contributed equally to this work. A.T. gratefully acknowledges the support of Australian Research Council (ARC) DP150101939, ARC DE160100569, and Westpac 2016 Research Fellowship. M.Z., S.H., and A.W.Y. H.-B. acknowledge the support of the Australian government via financial support from the ARC through the DP160102955 program and the Australian Renewable Energy Agency. K.R.C. acknowledges the support of an ARC Future Fellowship. The financial support from ARC through DP160102955 is also acknowledged