Consecutive Paths Research Articles

Impact of Temperature Variations on the Entrapment of Bacterial Endotoxins in Aqueous Solutions of Four-Antennary Oligoglycines

Specific self-assembly is registered in aqueous solution formulations based on four-antennary oligoglycines (T4), namely a spontaneous onset of highly ordered nanostructures—tectomers. This phenomenon is initiated by the action of hydrogen-bonding interactions that promote molecular recognition propensities involving Polyglycine-II-type non-canonical architecture. The result is the formation of positively charged supramolecular entities. These have high potential to capture bacterial endotoxins, like lipopolysaccharides (LPSs). By now, it has been established that the overall properties of these systems can be precisely regulated and gradually changed through fine-tuning the parameters in the aqueous environment (composition, pH, etc.). One unexplored option is to clarify the impact of temperature variations. The aim of the present study is to implement systematic investigations on how changes in temperature influence the various options for the removal of trace LPS quantities, captured by the T4 tectomers. The additional goal is to verify the possibility to develop consecutive paths of recovering the extra T4 quantities that have not participated in the formation of T4+LPS complexes. Some prospects for further applications, e.g., in medicine and pharmaceutics, are also generally outlined.

Multistage s–t Path: Confronting Similarity with Dissimilarity

Addressing a quest by Gupta et al. (in: Proceedings of the 41st international colloquium on automata, languages, and programming (ICALP 2014), vol 8572 of LNCS. Springer, pp 563–575, 2014), we provide a first, comprehensive study of finding a short s–t path in the multistage graph model, referred to as the Multistages–tPath problem. Herein, given a sequence of graphs over the same vertex set but changing edge sets, the task is to find short s–t paths in each graph (“snapshot”) such that in the found path sequence the consecutive s–t paths are “similar”. We measure similarity by the size of the symmetric difference of either the vertex set (vertex-similarity) or the edge set (edge-similarity) of any two consecutive paths. We prove that these two variants of Multistages–tPath are already {text {NP}}-hard for an input sequence of only two snapshots and maximum vertex degree four. Motivated by this fact and natural applications of this scenario e.g. in traffic route planning, we perform a parameterized complexity analysis. Among other results, for both variants, vertex- and edge-similarity, we prove parameterized hardness ({text {W[1]}}-hardness) regarding the parameter path length (solution size). As a further conceptual investigation, we then modify the multistage model by asking for dissimilar consecutive paths. As one of the main technical results (employing so-called representative sets known from non-temporal settings), we prove that dissimilarity allows for fixed-parameter tractability for the parameter solution size, contrasting with our W[1]-hardness proof of the corresponding similarity case. We also provide partially positive results concerning efficient and effective data reduction (kernelization).

Robot-assisted surface treatment strategies of AA6014 sheet metal for accumulative roll bonding

The application of high strength aluminum sheet metal components in automotive and aviation products effectively saves material and thus weight. Material strengthening can be realized by accumulative roll bonding (ARB), which belongs to the severe plastic deformation processes. Through repeated rolling steps a multilayered sheet metal is produced, which possesses increased strength due to its ultra-fine grained microstructure. Prior to each rolling step a surface treatment via wire brushing is mandatory for removing the oxide layer and roughening the sheet surface, which enables the bonding between the unique layers during rolling. The necessary surface treatment of the sheets is not fully understood by the current state of the art. In the past, it was not possible to achieve a defined and stable surface finish, because the brushing operation was done manually. The improvement of the process stability is essential to determine the relationship between the input parameters for brushing and the resulting bond strength of multilayered ARB sheets. For this reason, a robot-controlled surface treatment is introduced. The investigated material is the precipitation-hardened aluminum AA6014 with a sheet thickness of 1 mm. A suitable brushing kinematic under constant load is implemented and its effects on the surface properties are investigated by roughness measurements. The investigation shows, that the parameter combination leads to comparable or even higher roughness values than through manual brushing. Through 16 consecutive brushing paths a homogeneous and sufficient high surface roughness is realized, which enables material bonding in the rolling step. Thus, the research results indicate, that the robot-assisted surface treatment of ARB sheet metal is a promising method for a better automation and reproducibility of the brushing and the overall ARB process.

Importance sampling for a robust and efficient multilevel Monte Carlo estimator for stochastic reaction networks

The multilevel Monte Carlo (MLMC) method for continuous-time Markov chains, first introduced by Anderson and Higham (SIAM Multiscal Model. Simul. 10(1), 2012), is a highly efficient simulation technique that can be used to estimate various statistical quantities for stochastic reaction networks (SRNs), in particular for stochastic biological systems. Unfortunately, the robustness and performance of the multilevel method can be affected by the high kurtosis, a phenomenon observed at the deep levels of MLMC, which leads to inaccurate estimates of the sample variance. In this work, we address cases where the high-kurtosis phenomenon is due to \textit{catastrophic coupling (characteristic of pure jump processes where coupled consecutive paths are identical in most of the simulations, while differences only appear in a tiny proportion) and introduce a pathwise-dependent importance sampling (IS) technique that improves the robustness and efficiency of the multilevel method. Our theoretical results, along with the conducted numerical experiments, demonstrate that our proposed method significantly reduces the kurtosis of the deep levels of MLMC, and also improves the strong convergence rate from $\beta=1$ for the standard case (without IS), to $\beta=1+\delta$, where $0<\delta<1$ is a user-selected parameter in our IS algorithm. Due to the complexity theorem of MLMC, and given a pre-selected tolerance, $\text{TOL}$, this results in an improvement of the complexity from $\mathcal{O}\left(\text{TOL}^{-2} \log(\text{TOL})^2\right)$ in the standard case to $\mathcal{O}\left(\text{TOL}^{-2}\right)$, which is the optimal complexity of the MLMC estimator. We achieve all these improvements with a negligible additional cost since our IS algorithm is only applied a few times across each simulated path.

Analyzing the operational performance migration of telecom operators

Due to the rapid development of mobile Internet services, such as Skype and WeChat, traditional telecom services have suffered a large decline in the business volumes in recent years. Thus, telecom operators pay much attention to analyzing the changes of the enterprise performance, in order to adjust market strategies in time. In this paper, we propose a new methodology to analyze the operation data of telecom operators dynamically, which can characterize the changing process of the operating states and predict the developing trends. In particular, the proposed methodology contains two steps: migration pattern analysis and trajectory pattern analysis. Firstly, migration analysis is based on the changing of operating states between two points-in-time, which is referred to as the migration paths. Applying the clustering analysis to the migration paths can obtain the migration patterns, which characterize the changing feature of telecom operators during a short period, e.g. one month. Secondly, we combine a sequence of consecutive migration paths to obtain the migration trajectory. Through analyzing different trajectories based on the hierarchical cluster method and the Markov chain model, we obtain the trajectory patterns, which describe the changing progress during a relatively long period, e.g. one year. Based on the trajectory patterns, we can predict the possible performance changes. Finally, we apply the proposed method to a Chinese telecom operator for an empirical research, and has obtained a lot of development rules which provides insights into current telecom.

Deriving bisimulation relations from path based equivalence checkers

Abstract Translation validation is an undecidable problem. Bisimulation relation based approaches, nevertheless, have been widely successful in translation validation of programs albeit with some drawbacks. These drawbacks include non-termination of the verification methodology and significant restrictions on the structures of programs to be checked for equivalence. We have developed a path based equivalence checker which propagates mismatched values over consecutive paths to alleviate these drawbacks. In this work, we show how a bisimulation relation between a program and its translated version can be constructed from the outputs of such a value propagation based equivalence checker. Moreover, none of the earlier methods that establish equivalence through construction of bisimulation relations has been shown to tackle code motions across loops; the present work demonstrates, for the first time, the existence of a bisimulation relation under such a situation.

Rerouting shortest paths in planar graphs

A rerouting sequence is a sequence of shortest st-paths such that consecutive paths differ in one vertex. We study the Shortest Path Rerouting Problem, which asks, given two shortest st-paths P and Q in a graph G, whether a rerouting sequence exists from P to Q. This problem is PSPACE-hard in general, but we show that it can be solved in polynomial time if G is planar. In addition, it can be solved in polynomial time when every vertex has at most two neighbors closer to s and at most two neighbors closer to t. To this end, we introduce a dynamic programming method for reconfiguration problems, based on using small encodings of reconfiguration graphs.

Oxidative conversion of ethane over VMoTeNb oxide catalyst

The oxidative conversion of ethane over a multicomponent oxide catalyst with the composition V0.3Mo1Te0.23Nb0.12 was studied in the temperature range of 360–450°C. It was found that temperature did not affect the contribution from the parallel and consecutive paths of reaction product formation. The obtained data could be useful in developing applications for the process, particularly in choosing the type and design of a reactor (tubular fixed bed, fluidized bed, and so on).

Geometry of optimal path hierarchies

We investigate the hierarchy of optimal paths in a disordered landscape, based on the best path, the second best path and so on in terms of an energy. By plotting each path at a height according to its energy above some zero level, a landscape appears. This landscape is self-affine and controlled by two Hurst exponents: the one controlling the height fluctuations is 1/3 and the one controlling the fluctuations of the equipotential lines in the landscape is 2/3. These two exponents correspond to the exponents controlling energy and shape fluctations in the directed polymer problem. We furthermore find that the density of spanning optimal paths scale as the length of the paths to −2/3 and the histogram of energy differences between consecutive paths scale as a power law in the difference size with exponent −2.5.

Effects of metal nanoparticles deposition on the photocatalytic oxidation of ammonia in TiO2 aqueous suspensions

TiO2 powders modified through the deposition of surfactant-stabilized preformed metal (Pt, Pd, Au and Ag) nanoparticles (NPs) were tested as photocatalysts for batch ammonia photo-oxidation in aqueous suspension, under UVA irradiation. NH3 conversion and the selectivity toward mildly oxidized N2 and highly oxidized nitrite and nitrate anions were monitored during the runs, in order to study the effects of noble metal NPs deposition on the reaction mechanism. This involves parallel and consecutive paths, also depending on the type of metal deposited on TiO2, as also highlighted by the nitrite photo-oxidation tests performed in the present study. Metal NPs acted as electron traps ensuring better separation of the photoproduced charge couples and consequently higher rates of hole-mediated oxidation reactions. Apart from Au/TiO2, the metal-modified powders exhibited higher photoactivity with respect to that of naked titania, with Ag/TiO2 being the best performing photocatalyst in terms of ammonia conversion. On the other hand, Pd NPs on TiO2 ensured a considerable increase of the selectivity toward N2 and may thus be considered the best co-catalysts of TiO2 for environmentally friendly photocatalytic NH3 abatement.

ChemInform Abstract: Modeling Unimolecular Reactions in Photoelectron Photoion Coincidence Experiments

AbstractReview: 102 refs.

Alleviating the computational load of the probabilistic algorithms for circles detection using the connectivity represented by graph

The probabilistic algorithms are effective and widely used to recognize the curves in machine vision and image processing. In this paper, a novel algorithm for detecting circles is presented. It is based on the observation that the connectivity can help to alleviate the computational load of the probabilistic algorithm. A graph model is introduced to express connectivity in the detected edges, and a modified depth-first-search algorithm is developed to segment the whole graph into connected subgraphs and then partition the complex subgraph into simple paths. Then, four pixels are randomly selected from the sampling set, consisting of one proper path or several consecutive paths, to detect circles. The connectivity constraint is further employed to verify the candidates of circles to eliminate the pseudo ones. The experiments, comparing the proposed algorithm with the randomized Hough transform and the efficient randomized circle detection algorithm, show that it has the advantages of computational efficiency and robustness.

Kinetic study on biological reduction of selenium compounds

Biological treatment of selenium-containing wastewater was investigated using the selenium-reducing sludge acclimatized from denitrifying sludge. The kinetic behavior of selenium reduction was evaluated for both selenate- and selenite-acclimatized sludge using methanol as an electron donor in batch and continuous runs. Selenate and selenite concentrations decreased linearly till the end of reaction, indicating the zero-order kinetics of the consecutive reduction paths. The temperature dependency was satisfactorily expressed by the Arrhenius type equation with different activation energy in selenate and selenite reduction. The pH dependency was quite different, too. The inhibitory effects of nitrate coexistence in reacting fluid were different depending on the type of selenium and sludge employed. The continuous runs with actual industrial wastewater could be performed satisfactorily resulting in full reduction of the aqueous selenium species to native Se, which was reflected in quite low selenium concentration of the effluent.

An Efficient Approach for Analyzing User Behaviors in a Web-Based Training Environment

Mining frequent traversal patterns is to discover the consecutive reference paths traversed by a sufficient number of users from Web logs in a Web environment where users can travel from one object to another through the corresponding hyperlinks. Previous approaches for mining frequent traversal patterns only consider the forward references, such that the information about backward references will be lost. In this paper, we propose an efficient algorithm to discover the non-simple frequent traversal patterns. The non-simple frequent traversal patterns include forward and backward references, and are used to suggest potentially interesting traversal path to the users, which are useful, especially, in a Web-based training environment. The experimental results show that the discovered patterns can present the complete browsing paths traversed by most of the users and our algorithm outperforms other algorithms in discovered information and execution times.

Faraday quantum clock and nonlocal photon pair correlations

We study the use of the Faraday effect as a quantum clock for measuring traversal times of evanescent photons through magneto-refractive structures. The Faraday effect acts both as a phase-shifter and as a filter for circular polarizations. Only measurements based on the Faraday phase-shift properties are relevant to the traversal time measurements. The Faraday polarization filtering may cause the loss of non-local (Einstein-Podolsky-Rosen) two-photon correlations, but this loss can be avoided without sacrificing the clock accuracy. We show that a mechanism of destructive interference between consecutive paths is responsible for superluminal traversal times measured by the clock.

98/01103 Pyrolysis treatment of hydrocarbon sources such as petroleum heavy oils and naphtha using sensible heat of rough coke oven gas: Ueno, I. Jpn. Kokai Tokkyo Koho JP 09,286,986 [97,286,986] (Cl. C10B27/00), 4 Nov 1997, Appl. 96/102,571, 24 Apr 1996, 4 pp. (in Japanese)

Fischer–Tropsch synthesis seems to develop the following two consecutive paths: a primary process that involves the formation of α-olefin products and a secondary process leading to the production of branched isomers and paraffins and requiring the readsorption of primary α-olefin products. It was already shown by Iglesiaet al.(E. Iglesia, S. C. Reyes, and R. J. Madon,J. Catal.129, 238 (1991)) that such readsorption steps are of fundamental importance for Ru catalysts and that they occur due to the slow diffusive removal of α-olefins when the molecular size increases, this resulting in a long intraparticle residence time. In the present paper α-olefins readsorption was enhanced by changing the metal distribution inside the pores of a titanium silicate (ETS-10), modified by ion exchange with alkali metal ions, used as a support for Ru-based catalysts.

Experimental Evidence of α-Olefin Readsorption in Fischer–Tropsch Synthesis on Ruthenium-Supported ETS-10 Titanium Silicate Catalysts

Fischer–Tropsch synthesis seems to develop the following two consecutive paths: a primary process that involves the formation of α-olefin products and a secondary process leading to the production of branched isomers and paraffins and requiring the readsorption of primary α-olefin products. It was already shown by Iglesiaet al.(E. Iglesia, S. C. Reyes, and R. J. Madon,J. Catal.129, 238 (1991)) that such readsorption steps are of fundamental importance for Ru catalysts and that they occur due to the slow diffusive removal of α-olefins when the molecular size increases, this resulting in a long intraparticle residence time. In the present paper α-olefins readsorption was enhanced by changing the metal distribution inside the pores of a titanium silicate (ETS-10), modified by ion exchange with alkali metal ions, used as a support for Ru-based catalysts.

Consecutive cuts and paths, and bounds onk‐terminal reliability

AbstractShanthikumar developed an upper bound for two‐terminal reliability based on consecutives – tcutsets. Subsequently, Shier generalized this strategy to obtain upper bounds from cutsets, and lower bounds from pathsets, when the cutsets or pathsets form a semilattice structure. We examine a restricted case of Shier's method that yields ak‐terminal lower bound based on consecutive pathsets. Our approach employs a common reduction of consecutive cut and path bounds to the computation of the two‐terminal reliability of an interval graph with imperfect vertices. Computational results are given to support the observation that the consecutive paths lower bound is competitive with the best efficiently computable bounds that are currently available. We then apply the consecutive path bound to reduce, in some cases dramatically, the number of states generated in a most probable state bounding method.

95/01389 Humic acids from coal. Production, Characterization and ultilization

Fischer–Tropsch synthesis seems to develop the following two consecutive paths: a primary process that involves the formation of α-olefin products and a secondary process leading to the production of branched isomers and paraffins and requiring the readsorption of primary α-olefin products. It was already shown by Iglesiaet al.(E. Iglesia, S. C. Reyes, and R. J. Madon,J. Catal.129, 238 (1991)) that such readsorption steps are of fundamental importance for Ru catalysts and that they occur due to the slow diffusive removal of α-olefins when the molecular size increases, this resulting in a long intraparticle residence time. In the present paper α-olefins readsorption was enhanced by changing the metal distribution inside the pores of a titanium silicate (ETS-10), modified by ion exchange with alkali metal ions, used as a support for Ru-based catalysts.

ChemInform Abstract: SELECTIVITY AND RATE OF ACTIVITY DECLINE OF BIMETALLIC CATALYSTS

Abstract The relevant characteristics of metal catalysts are their activity, selectivity and rate of activity decline. For bimetallic catalysts, these characteristics often deviate strongly from additivity. The pronounced changes in selectivity caused by alloying an active transition metal with an inactive diluent are conveniently described in terms of different ensemble requirements for parallel and consecutive reaction paths. The significant lowering of the rate of activity decline, which results from the addition of, for instance, rhenium to a Pt/Al 2 O 3 reforming catalyst in the presence of a feed containing non-negligible traces of sulfur compounds, has been rationalized qualitatively in terms of several models. In the present paper, these models are discussed and compared with experimental results in the scientific literature. One model assumes that adsorbed carbonaceous fragments become deleterious catalyst poisons only after atomic reorganizations resulting in graphitic structures. The ease of such reorganizations is controlled by the chemistry and the atomic topography of the catalyst surface.