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Digitale Medien

Two-Sample Tests of Area-Under-the-Curve in the Presence of Missing Data (2008)

Spritzler, John ; DeGruttola, Victor G ; Pei, Lixia

Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)

The @international journal of biostatistics 4 (2008), S. 1

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ISSN: 1557-4679

Quelle: Berkeley Electronic Press Academic Journals

Thema: Biologie , Mathematik , Medizin

Notizen: The commonly used two-sample tests of equal area-under-the-curve (AUC), where AUC is based on the linear trapezoidal rule, may have poor properties when observations are missing, even if they are missing completely at random (MCAR). We propose two tests: one that has good properties when data are MCAR and another that has good properties when the data are missing at random (MAR), provided that the pattern of missingness is monotonic. In addition, we discuss other non-parametric tests of hypotheses that are similar, but not identical, to the hypothesis of equal AUCs, but that often have better statistical properties than do AUC tests and may be more scientifically appropriate for many settings.

Materialart: Digitale Medien

URL: http://www.bepress.com/ijb/vol4/iss1/1

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2

Digitale Medien

Coalescent Time Distributions in Trees of Arbitrary Size (2008)

Efromovich, Sam ; Salter Kubatko, Laura

Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)

Statistical applications in genetics and molecular biology 7.2008, 1, art2

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ISSN: 1544-6115

Quelle: Berkeley Electronic Press Academic Journals

Thema: Biologie

Notizen: The relationship between speciation times and the corresponding times of gene divergence is of interest in phylogenetic inference as a means of understanding the past evolutionary dynamics of populations and of estimating the timing of speciation events. It has long been recognized that gene divergence times might substantially pre-date speciation events. Although the distribution of the difference between these has previously been studied for the case of two populations, this distribution has not been explicitly computed for larger species phylogenies. Here we derive a simple method for computing this distribution for trees of arbitrary size. A two-stage procedure is proposed which (i) considers the probability distribution of the time from the speciation event at the root of the species tree to the gene coalescent time conditionally on the number of gene lineages available at the root; and (ii) calculates the probability mass function for the number of gene lineages at the root. This two-stage approach dramatically simplifies numerical analysis, because in the first step the conditional distribution does not depend on an underlying species tree, while in the second step the pattern of gene coalescence prior to the species tree root is irrelevant. In addition, the algorithm provides intuition concerning the properties of the distribution with respect to the various features of the underlying species tree. The methodology is complemented by developing probabilistic formulae and software, written in R. The method and software are tested on five-taxon species trees with varying levels of symmetry. The examples demonstrate that more symmetric species trees tend to have larger mean coalescent times and are more likely to have a unimodal gamma-like distribution with a long right tail, while asymmetric trees tend to have smaller mean coalescent times with an exponential-like distribution. In addition, species trees with longer branches generally have shorter mean coalescent times, with branches closest to the root of the tree being most influential.

Materialart: Digitale Medien

URL: http://www.bepress.com/sagmb/vol7/iss1/art2

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3

Digitale Medien

Performance of Statistical Process Control Tools under Different Plant Operation Strategies (2008)

Maestri, Mauricio L. ; Cassanello, Miryan C. ; Horowitz, Gabriel I.

Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)

Chemical product and process modeling 3 (2008), S. 4

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ISSN: 1934-2659

Quelle: Berkeley Electronic Press Academic Journals

Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: The outputs of statistical process control (SPC) tools developed for fault detection are comparatively examined while applied to actual data collected in an industrial plant. The influence of added information gathered from the plant operation under different strategies is analyzed. Particularly, standard principal component analysis (PCA), kernel PCA and the Hotelling's T2 charts are inspected for a reported problem. The effect of training the tools either with an extended historic databank obtained under standard operation, or including also non-conventional conditions, is studied. The ability of the tools to provide a specific alarm and identify the responsible variable is examined by analyzing the contributions per variable to the SPE and the T2 statistics. In addition, the capacity of the tested tools to adapt to a new operation strategy is compared.

Materialart: Digitale Medien

URL: http://www.bepress.com/cppm/vol3/iss1/4

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4

Digitale Medien

Dynamic Model for Polyethylene Production in a Multizone Circulating Reactor (2008)

Ghasem, Nayef M. ; Ang, Wee-Lee ; Hussain, Mohamed Azlan

Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)

Chemical product and process modeling 3 (2008), S. 1

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ISSN: 1934-2659

Quelle: Berkeley Electronic Press Academic Journals

Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: The multizone circulating reactor (MZCR) technology is a newly announced reactor design for solid-catalyzed gas-phase polymerization. The process is characterized by two hydrodynamically distinct but interconnecting polymerization zones, thus forming a continuous loop of polymer flow between the said zones. In the present study, a dynamic model for the MZCR reactor is developed to illustrate the basic dynamic behavior of the new reactor design; the model is used to study the copolymerization of ethylene with butene. Several parameter sensitivity analyses are performed to show the computer-simulated time responses for reactor temperature, number-average molecular weight, weight-average molecular weight, catalyst feed rate and the monomer concentration along the reactor length.

Materialart: Digitale Medien

URL: http://www.bepress.com/cppm/vol3/iss1/1

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5

Digitale Medien

A Modeling and Optimization Tool for the Expandable Polystyrene Batch Process (2008)

Heikkinen, Mikko ; Nurminen, Ville ; Hiltunen, Teri ; [weitere]

Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)

Chemical product and process modeling 3 (2008), S. 3

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ISSN: 1934-2659

Quelle: Berkeley Electronic Press Academic Journals

Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: Expandable Polystyrene (EPS), a material of the insulation productions and packages, is commonly produced in a batch process. The control of the batch process is based on predefined process recipes and process parameters such as mixing properties. The EPS production has to be able to satisfy the aims and quality requirements of the markets, which causes additional demands on the process control. In this paper we demonstrate the optimization and modeling application for the EPS-batch process. The application consists of a production optimization tool and a simulation tool for the process parameters based on the Multi-Layer Perceptron network (MLP) with retrain properties. The software can be used at the operational level as well as at the process management level. The features are programmed into standalone software built up in the Matlab environment and it is tailored for the needs of the EPS production company StyroChem Ltd. The results show that the application can offer an efficient tool to economize production and storage costs.

Materialart: Digitale Medien

URL: http://www.bepress.com/cppm/vol3/iss1/3

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6

Digitale Medien

Investigation and Modeling of Splashing in the Peirce Smith Converter (2008)

Hasanzadeh - Lileh Koohi, Ali ; Halali, Mohammad ; Askari, Masoud ; [weitere]

Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)

Chemical product and process modeling 3 (2008), S. 2

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ISSN: 1934-2659

Quelle: Berkeley Electronic Press Academic Journals

Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: To investigate the factors affecting splashing in Peirce-Smith copper converters of Sarcheshmeh copper complex, South-East Iran, a laboratory scale model with dimensions one eighth of the actual converter was designed and assembled. The model was filled with water. Air was impinged onto the water. The sequence of events was subsequently recorded using high speed cameras. Factors affecting splashing such as blowing angle, volumetric flow rate of air, and the distance of the blowers from water surface were studied.Using a value of 2.65×10-11 for Morton dimensionless number, it was found that splashing may be reduced by 75% if the air speed in the tuyeres is reduced from 155 m/s to 30 m/s while the nozzle distance from the melt free surface is between 2 to 0.5 meters.

Materialart: Digitale Medien

URL: http://www.bepress.com/cppm/vol3/iss1/2

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7

Digitale Medien

Self-Organizing Maps with Statistical Phase Synchronization (SOMPS) for Analyzing Cell Cycle-Specific Gene Expression Data (2008)

Kim, Chang Sik

Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)

Statistical applications in genetics and molecular biology 7.2008, 1, art1

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ISSN: 1544-6115

Quelle: Berkeley Electronic Press Academic Journals

Thema: Biologie

Notizen: Based on previous studies related to the yeast cell cycle, it is well known that the underlying cellular network in yeast consists of many interactions between genes that have periodic expression patterns during the cell division cycle. In this study, it is proposed that cell cycle-specific gene expression can be understood as a phenomenon of collective synchronization or, in other words, an ensemble of non-identical oscillating response signals from different systems. Therefore, we aimed to apply the theory of statistical multivariate phase synchronization to understand the cell's cyclic transcriptome as a phenomenon of collective synchronization. To this end, a novel algorithm called Self-Organizing Maps with statistical Phase Synchronization (SOMPS) is proposed and evaluated using yeast cell cycle-specific gene expression data. From the evaluation experiments, we draw the following conclusions: 1) It is possible to find groups of genes that have biological interactions with each other and significantly share gene ontology slim terms of biological processes using the theory of multivariate phase synchronization with cell cycle-specific gene expression signals; 2) Among all output clusters of SOMPS, a relatively large cluster with high periodicity with respect to its trained mean field can be considered a prominent cluster; 3) For each gene, it is possible to identify the degree of the strength of its biological interactions with other genes using the coupling strength of synchronization with its trained mean field; and 4) It is feasible to understand cell cycle-specific expression patterns as a phenomenon of collective synchronization.

Materialart: Digitale Medien

URL: http://www.bepress.com/sagmb/vol7/iss1/art1

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8

Digitale Medien

Introduction to the Inaugural Issue of Journal of Biomimetics, Biomaterials and Tissue Engineering (2008)

s.l. ; Stafa-Zurich, Switzerland

Journal of biomimetics, biomaterials, and tissue engineering Vol. 1 (July 2008), p. -2--1

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ISSN: 1662-100X

Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008

Thema: Biologie , Technik allgemein

Materialart: Digitale Medien

URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/43/transtech_doi~10.4028%252Fwww.scientific.net%252FJBBTE.1.-2.pdf

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9

Digitale Medien

Mesoporous Bioactive Glasses: Synthesis,Characterization and 〈i〉In Vitro 〈/i〉Bioactivity (2008)

Zhao, Yu Feng ; Ma, Jan

s.l. ; Stafa-Zurich, Switzerland

Journal of biomimetics, biomaterials, and tissue engineering Vol. 1 (July 2008), p. 37-47

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ISSN: 1662-100X

Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008

Thema: Biologie , Technik allgemein

Notizen: In this work, two systems of mesoporous bioactive glasses (MBGs) with a series ofdifferent SiO2:CaO:P2O5 ratios were derived via a sol-gel method involving the usage of blockcopolymers Pluronic F127 and P123 as templates, respectively. A two-dimensional hexagonal(P6mm) mesoporous structure was obtained in the two systems with a SiO2:CaO:P2O5 ratio of80:16:4. With the decrease of the SiO2 content, the porous structure of MBGs became less regular,and the BET surface area and the pore volume were also decreased. Mesoporous bioactive glassesfrom the template F127 displayed a higher degree of bioactivity than those from the template P123,as a result of the existence of more defects on the walls of the mesopores

Materialart: Digitale Medien

URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/43/transtech_doi~10.4028%252Fwww.scientific.net%252FJBBTE.1.37.pdf

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10

Digitale Medien

Surgical Sutures: Performance, Development and Use (2008)

Azhahia Manavalan, R. ; Mukhopadhyay, A.

s.l. ; Stafa-Zurich, Switzerland

Journal of biomimetics, biomaterials, and tissue engineering Vol. 1 (July 2008), p. 1-36

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ISSN: 1662-100X

Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008

Thema: Biologie , Technik allgemein

Notizen: The paper reports about different kind of sutures, their suitability and performance. An ideal suture should possess many characteristics such as - easy to handle, bio-compatibility, minimal tissue reaction, resistance to bacterial growth, adequate tensile strength and elasticity, knot security, strength loss versus healing rate of tissues. Selection of suture is often very complex for satisfying host of physical, mechanical and biological properties, and fulfilling contradictory requirements in varied applications. The paper develops an understanding about the selection of suture depending on the varied requirement. Past research work pertaining to the development of suture as reported in this paper, provides insight about the suitability of different surgical sutures and possible direction of future research

Materialart: Digitale Medien

URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/43/transtech_doi~10.4028%252Fwww.scientific.net%252FJBBTE.1.1.pdf

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