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RISS 인기검색어
- 검색키워드
- 저자 : D. van Veen (검색결과 4 건)
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Nuclear Data Uncertainty Propagation: Total Monte Carlo vs. Covariances
D. Rochman,A. J. Koning,S. C. van der Marck,A. Hogenbirk,D. van Veen 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
Two distinct methods of propagation for basic nuclear data uncertainties to large scale systems will be presented and compared. The "Total Monte Carlo" method is using a statistical ensemble of nuclear data libraries randomly generated by means of a Monte Carlo approach with the TALYS system. These libraries are then directly used in a large number of reactor calculations (for instance with MCNP) after which the exact probability distribution for the reactor parameter is obtained. The second method makes use of available covariance files and can be done in a single reactor calculation (by using the perturbation method). In this exercise, both methods are using consistent sets of data files, which implies that covariance files used in the second method are directly obtained from the randomly generated nuclear data libraries from the first method. This is a unique and straightforward comparison allowing to directly apprehend advantages and drawbacks of each method. Comparisons for different reactions and criticality-safety benchmarks from ^(19)F to actinides will be presented. We can thus conclude whether current methods for using covariance data are good enough or not.
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A high-throughput microfluidic assay to study neurite response to growth factor gradients
Kothapalli, Chandrasekhar R.,van Veen, Ed,de Valence, Sarra,Chung, Seok,Zervantonakis, Ioannis K.,Gertler, Frank B.,Kamm, Roger D. Royal Society of Chemistry 2011 Lab on a chip Vol.11 No.3
<P>Studying neurite guidance by diffusible or substrate bound gradients is challenging with current techniques. In this study, we present the design, fabrication and utility of a microfluidic device to study neurite guidance under chemogradients. Experimental and computational studies demonstrated the establishment of a steep gradient of guidance cue within 30 min and stable for up to 48 h. The gradient was found to be insensitive to external perturbations such as media change and movement of device. The effects of netrin-1 (0.1–10 µg mL<SUP>−1</SUP>) and brain pulp (0.1 µL mL<SUP>−1</SUP>) were evaluated for their chemoattractive potential on neurite turning, while slit-2 (62.5 or 250 ng mL<SUP>−1</SUP>) was studied for its chemorepellant properties. Hippocampal or dorsal root ganglion (DRG) neurons were seeded into a micro-channel and packed onto the surface of a 3D collagen gel. Neurites grew into the matrix in three dimensions, and a gradient of guidance cue was created orthogonal to the direction of neurite growth to impact guidance. The average turning angle of each neurite was measured and averaged across multiple devices cultured under similar conditions to quantify the effect of guidance cue gradient. Significant positive turning towards gradient was measured in the presence of brain pulp and netrin-1 (1 µg mL<SUP>−1</SUP>), relative to control cultures which received no external guidance cue (<I>p</I> < 0.001). Netrin-1 released from transfected fibroblasts had the most positive turning effect of all the chemoattractive cues tested (<I>p</I> < 0.001). Slit-2 exhibited strong chemorepellant characteristics on both hippocampal and DRG neurite guidance at 250 ng mL<SUP>−1</SUP> concentration. Slit-2 also showed similar behavior on DRG neuron invasion into 3D collagen gel (<I>p</I> < 0.01 relative to control cultures). Taken together, the results suggest the utility of this microfluidic device to generate stable chemogradients for studying neurobiology, cell migration and proliferation, matrix remodeling and co-cultures with other cell lines, with potential applications in cancer biology, tissue engineering and regenerative medicine.</P> <P>Graphic Abstract</P><P>We describe a three-channel microfluidic device to study the role of chemogradients on neurite outgrowth and guidance in 3D scaffolds, using experimental and computational studies. The stable chemogradients in these devices could also be used to screen potential drugs for neuron pathway regeneration under disease/ injury conditions, cell migration and cell–cell interactions. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0lc00240b'> </P>
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International comparison CCQM-K119 liquefied petroleum gas
Brewer, P J,Downey, M L,Atkins, E,Brown, R J C,Brown, A S,Zalewska, E T,van der Veen, A M H,Smeulders, D E,McCallum, J B,Satumba, R T,Kim, Y D,Kang, N,Bae, H K,Woo, J C,Konopelko, L A,Popova, T A,Mesh IOP 2018 Metrologia Vol.55 No.-
<P></P> <P>Liquefied hydrocarbon mixtures with traceable composition are required in order to underpin measurements of the composition and other physical properties of LPG (liquefied petroleum gas), thus meeting the needs of an increasingly large industrial market.</P> <P>This comparison aims to assess the analytical capabilities of laboratories for measuring the composition of a Liquid Petroleum Gas (LPG) mixture when sampled in the liquid phase from a Constant Pressure Cylinder. Mixtures contained ethane, propane, propene, i-butane, n-butane, but-1-ene and i-pentane with nominal amount fractions of 2, 71, 9, 4, 10, 3 and 1 cmol mol<SUP>−1</SUP> respectively.</P> <H2>Main text</H2> <P> To reach the main text of this paper, click on <A HREF='https://www.bipm.org/utils/common/pdf/final_reports/QM/K119/CCQM-K119.pdf'>Final Report</A>. Note that this text is that which appears in Appendix B of the BIPM key comparison database <A HREF='http://kcdb.bipm.org/'>kcdb.bipm.org/</A>.</P> <P>The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).</P>
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