Characterization of dielectric spheres by spiral imaging

This paper was published in Optics Letters and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OL.37.000869. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.We study the spiral spectra scattered off transparent dielectric spheres when probed by different Laguerre–Gaussian light beams, carrying nested topological wavefront dislocations. We show that such scattering data may be employed to determine geometrical properties of the spheres, such as their position. The technique is a generalization of standard Mie scattering, and it can be extended to study and to characterize nanospheres.Postprint (published version

Reporte de un caso de hematofagia indirecta por una araña Salticidae (Arachnida: Araneae) en Quintana Roo, México

Se reporta un caso de hematofagia indirecta en el que participó la araña saltarina Frigga pratensis (Peckham y Peckham) al consumir un ejemplar hembra de Aedes albopictus Skuse en la ciudad de Chetumal, Quintana Roo, México. Este es el primer registro de tan inusual fenómeno en el Neotrópico; se discute si se trata de un caso aislado o existen implicancias ecológicas mayores

Análisis comparativo del transporte de sedimentos con cambio granulométrico

[ES] La mayor parte de los modelos de fondo móvil existentes son aplicados a un diámetro representativo del material del fondo. Esta consideración puede no ser la más recomendable, ya que si la muestra de sedimentos es no uniforme, se genera un error sustancial en la estimación del transporte y depósito de partículas en el fondo. En estos casos lo más conveniente es dividir la muestra en fracciones con un diámetro representativo para cada una y calcular el transporte de sedimento por partes. En el presente trabajo se desarrolla un modelo numérico unidimensional de fondo móvil, que pronostica los procesos de erosión y depósito y determina el cambio granulométrico asociado al movimiento del fondo. Las ecuaciones hidrodinámicas se resuelven por el método de pasos fraccionados y las ecuaciones de sedimentos a través de un esquema explícito. Ambos sistemas se acoplan en el tiempo. El cambio granulométrico se determina adoptando el concepto de capa activa. Se comparan y analizan los resultados obtenidos al modelar empleando la fórmula de transporte en sus posibles variantes: a) empleando un diámetro representativo de la muestra, b) dividiendo la muestra en fracciones y c) dividiendo en fracciones y asociando el cambio granulométrico. Los resultados muestran una mejor representación y caracterización del fondo al considerar el cambio granulométrico durante la simulación, de manera que el modelo desarrollado proporciona criterios útiles que se pueden emplear en estudios posteriores.Se agradece al CONACYT, al Instituto de Ingeniería de la UNAM y a la Universidad Autónoma Metropolitana por el apoyo económico y moral otorgado para la realización de este trabajo.Rivera Trejo, F.; Soto Cortés, G. (2002). Análisis comparativo del transporte de sedimentos con cambio granulométrico. Ingeniería del Agua. 9(1):73-79. https://doi.org/10.4995/ia.2002.2609SWORD737991BEREZOWSKY M., A. JIMÉNEZ (1995), "Flujo no permanente en ríos", Capítulo 6 del Manual de Ingeniería de Ríos. Series del Instituto de Ingeniería, UNAM, México.BENNET, J.P., C.F. NORDIN, (1977), "Simulation of sediment transport and armoring", Hydrological Sciences Bulletin, XXII, Vol.4, No.12, pp. 555-569BENQUÉ, J.P, J.A. CUNGE, J. FEUILLET, A. HAUGUEL & F.M. HOLLY. (1982), "New method for tidal current computation". J. of the Waterway, Port, Coastal and Ocean Div., ASCE, Vol. 108, No. WW3, 396-417.EINSTEIN, H.A., N. CHIEN, (1953). "Transport of sediment mixtures with large ranges of grain sizes." Univ. of Calif. Inst. of Engrg. Res., Berkeley, Calif., M.R.D. Series No. 2.HOLLY F., J. RAHUEL (1990)., "New numerical/physical framework for mobile-bed modeling", Journal of Hydraulics Research, Vol 28, No. 5, pp. 545-564HOLLYF., J. RAHUEL (1989), "Advances in Computational Mobil-Bed Hydraulics", Sediment Transport Modeling, Proceedings of the International Sympotion. ASCE, pp. 58-63.KARIM F. (1998) "Bed Material Discharge Prediction for Nonuniform Bed Sediments", Journal of Hydraulic Engineering, Vol 124, No. 6 June, pp. 597-604.LÓPEZ J. And M FALCÓN. (1999) "Calculation of bed changes in mountain streams", Journal of Hydraulic Engineering, Vol 125, No. 3 March, pp. 263-270.KEH-CHIA YEH, C WU, J. YANG, S. LI (1993) "Nonuniform Transient Sediment Transport Modeling" Procc, Nat. Conference on Hydraulic Engrg. ASCE. New York. NY. Vol. 2, pp. 893-898.RAHUEL J., HOLLY F, CHOLLET J, BELLEUDY P. and YANG G. (1989) "Modeling of Riverbed Evolution for Bedload sediment Mixtures" Journal of Hydraulics Engineering. Vol 115, No. 11, November, pp. 1521-1542RIVERA F. (2001), Modelo bidimensional de fondo móvil". Tesis doctoral DEPFI, UNAM, México. (2001).SOTO. G., (2001). "Mallas adaptables para la solución de la hidrodinámica de cuerpos de agua", Tesis doctoral. DEPFI, UNAM.SPASOJEVIC M. F HOLLY (1990)., "2-D Bed Evolution in Natural Watercourses - New Simulation Approach", Journal of Waterway, Port and Ocean Engineering, Vol 116, No. 4 July/August, pp. 425-443.TARELA P., A. MENÉNDEZ, F. BOMBARDELLI, P JAIME P. (1998), "Metodología para la predicción de la evolución bidimensional de lechos fluviales". XVIII Congreso Latinoamericano de Hidráulica. Oaxaca, México.VAN NICKERK A., K. VOGEL, R. SLINGERLAND, J. BRIDGE (1992), "Routing of Heterogeneous Sediment over Movable Bed: Model Development", Journal of Hydraulic Engineering, Vol 118, No. 2 February, pp. 246-261.YANENKO. J.N. (1971), "The method of fractional steps".Springer

Structural and biophysical investigation of the interaction of a mutant Grb2 SH2 domain (W121G) with its cognate phosphopeptide

The adaptor protein Grb2 is a key element of mitogenetically important signaling pathways. With its SH2 domain it binds to upstream targets while its SH3 domains bind to downstream proteins thereby relaying signals from the cell membranes to the nucleus. The Grb2 SH2 domain binds to its targets by recognizing a phosphotyrosine (pY) in a pYxNx peptide motif, requiring an Asn at the +2 position C-terminal to the pY with the residue either side of this Asn being hydrophobic. Structural analysis of the Grb2 SH2 domain in complex with its cognate peptide has shown that the peptide adopts a unique β-turn conformation, unlike the extended conformation that phosphopeptides adopt when bound to other SH2 domains. TrpEF1 (W121) is believed to force the peptide into this unusual conformation conferring this unique specificity to the Grb2 SH2 domain. Using X-ray crystallography, electron paramagnetic resonance (EPR) spectroscopy, and isothermal titration calorimetry (ITC), we describe here a series of experiments that explore the role of TrpEF1 in determining the specificity of the Grb2 SH2 domain. Our results demonstrate that the ligand does not adopt a pre-organized structure before binding to the SH2 domain, rather it is the interaction between the two that imposes the hairpin loop to the peptide. Furthermore, we find that the peptide adopts a similar structure when bound to both the wild-type Grb2 SH2 domain and a TrpEF1Gly mutant. This suggests that TrpEF1 is not the determining factor for the conformation of the phosphopeptide

Shallow sediment transport flow computation using time-varying sediment adaptation length

YesBased on the common approach, the adaptation length in sediment transport is normally estimated in the temporal independence. However, this approach might not be theoretically justified as the process of reaching of the sediment transport equilibrium stage is affected by the flow conditions in time, especially for those fast sediment moving flows, such as scour-hole developing flow. In this study, the 2D shallow water formulation together with a sediment continuity-concentration (SCC) model were applied to flow with mobile sediment boundary. A time-varying approach was proposed to determine the sediment transport adaptation length to treat the flow sediment erosion-deposition rate. The proposed computational model was based on the Finite Volume (FV) method. The Monotone Upwind Scheme of Conservative Laws (MUSCL)-Hancock scheme was used with the Harten Lax van Leer-contact (HLLC) approximate Riemann solver to discretize the FV model. In the flow applications of this paper, a highly discontinuous dam-break fast sediment transport flow was used to calibrate the proposed time-varying sediment adaptation length model. Then the calibrated model was further applied to two separate experimental sediment transport flow applications documented in literature, i.e. a highly concentrated sediment transport flow in a wide alluvial channel and a sediment aggradation flow. Good agreements with the experimental data were presented by the proposed model simulations. The tests prove that the proposed model, which was calibrated by the discontinuous dam-break bed scouring flow, also performed well to represent the rapid bed change and the steady sediment mobility conditions.The National Natural Science Foundation of China NSFC (Grant Number 20101311246), Major State Basic Research Development Program (973 program) of China (Grant Number 2013CB036402) and Open Fund of the State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University of China (Grant Number SKLH-OF-1103)

Development of Grb2 SH2 Domain Signaling Antagonists: A Potential New Class of Antiproliferative Agents

Aberrant signaling through protein-tyrosine kinase (PTK)-dependent pathways is associated with several proliferative diseases. Accordingly, PTK inhibitors are being developed as new approaches for the treatment of certain cancers. Growth factor receptor bound protein 2 (Grb2) is an important downstream mediator of PTK signaling that serves obligatory roles in many pathogenic processes. One of the primary functions of Grb2 is to bind to specific phosphotyrosyl (pTyr)-containing sequences through its Src homology 2 (SH2) domain. Agents that bind to the Grb2 SH2 domain and prevent its normal function could disrupt associated PTK signaling and serve as alternatives to kinase-directed inhibitors. Starting from the X-ray crystal structure of a lead peptide bound to the Grb2 SH2 domain, this review will summarize important contributions to these efforts. The presentation will be thematically arranged according to the region of peptide modified, proceeding from the N-terminus to the C-terminus, with a special section devoted to aspects of conformational constraint

Laminin isoforms in human embryonic stem cells : synthesis, receptor usage and growth support

Sanna Vuoristo, Ismo Virtanen, Minna Takkunen, Jaan Palgi, Yamato Kikkawa, Patricia Rousselle, Kiyotoshi Sekiguchi, Timo Tuuri, and Timo Otonkoski, "Laminin isoforms in human embryonic stem cells: synthesis, receptor usage and growth support", Journal of Cellular and Molecular Medicine, 13, 8b, pp. 2622-2633, Wiley, 200