1,247 research outputs found
My Brother, My Witness against Me: The Constitutionality of the against Penal Interest Hearsay Exception in Confrontation Clause Analysis
My Brother, My Witness against Me: The Constitutionality of the against Penal Interest Hearsay Exception in Confrontation Clause Analysis
Tessellations and Pattern Formation in Plant Growth and Development
The shoot apical meristem (SAM) is a dome-shaped collection of cells at the
apex of growing plants from which all above-ground tissue ultimately derives.
In Arabidopsis thaliana (thale cress), a small flowering weed of the
Brassicaceae family (related to mustard and cabbage), the SAM typically
contains some three to five hundred cells that range from five to ten microns
in diameter. These cells are organized into several distinct zones that
maintain their topological and functional relationships throughout the life of
the plant. As the plant grows, organs (primordia) form on its surface flanks in
a phyllotactic pattern that develop into new shoots, leaves, and flowers.
Cross-sections through the meristem reveal a pattern of polygonal tessellation
that is suggestive of Voronoi diagrams derived from the centroids of cellular
nuclei. In this chapter we explore some of the properties of these patterns
within the meristem and explore the applicability of simple, standard
mathematical models of their geometry.Comment: Originally presented at: "The World is a Jigsaw: Tessellations in the
Sciences," Lorentz Center, Leiden, The Netherlands, March 200
Recommended from our members
Organizational Factors that Contribute to Operational Failures in Hospitals
The performance gap between hospital spending and outcomes is indicative of inefficient care delivery. Operational failuresâbreakdowns in internal supply chains that prevent work from being completedâcontribute to inefficiency by consuming 10% of nursesâ time (Hendrich et al. 2008, Tucker 2004). This paper seeks to identify organizational factors associated with operational failures, with a goal of providing insight into effective strategies for removal. We observed nurses on medical/ surgical units at two hospitals, shadowed support staff who provided materials, and interviewed employees about their internal supply chainâs performance. These activities created a database of 120 operational failures and the organizational factors that contributed to them. We found that employees believed their departmentâs performance was satisfactory, but poorly trained employees in other departments caused the failures. However, only 14% of the operational failures arose from errors or training. They stemmed instead from multiple organizationally-driven factors: insufficient workspace (29%), poor process design (23%), and a lack of integration in the internal supply chains (23%). Our findings thus suggest that employees are unlikely to discern the role that their departmentâs routines play in operational failures, which hinders solution efforts. Furthermore, in contrast to the âPareto Principleâ which advocates addressing âlargeâ problems that contribute a disproportionate share of the cumulative negative impact of problems, the failures and causes were dispersed over a wide range of factors. Thus, removing failures will require deliberate cross-functional efforts to redesign workspaces and processes so they are better integrated with patientsâ needs
Recommended from our members
Designed for Workarounds: A Qualitative Study of the Causes of Operational Failures in Hospitals
Frontline care providers in hospitals spend at least 10% of their time working around operational failures, which are situations where information, supplies, or equipment needed for patient care are insufficient. However, little is known about underlying causes of operational failures and what hospitals can do to reduce their occurrence. To address this gap, we examined the internal supply chains at two hospitals with the aim of discovering organizational factors that contribute to operational failures. We conducted in-depth qualitative research, including observations and interviews of over 80 individuals from 4 nursing units and the ancillary support departments that provide equipment and supplies needed for patient care. We found that a lack of interconnectedness among interdependent departments' routines was a major source of operational failures. The low levels of interconnectedness occurred because of how the internal supply chains were designed and managed rather than because of employee error or a shortfall in training. Thus, we propose that the time that hospital staff spend on workarounds can be reduced through deliberate efforts to increase interconnectedness among hospitals' internal supply departments. Four dimensions of interconnectedness include (1) hospital-levelârather than department-levelâperformance measures; (2) internal supply department routines that respond to specific patients' needs rather than to predetermined stocking routines; (3) knowledge that is necessary for efficient handoffs of materials is translated across departmental boundaries; and (4) cross-departmental collaboration mechanisms that enable improvement in the flow of materials across departmental boundaries
Star Formation in Sculptor Group Dwarf Irregular Galaxies and the Nature of "Transition" Galaxies
We present new H-alpha narrow band imaging of the HII regions in eight
Sculptor Group dwarf irregular (dI) galaxies. Comparing the Sculptor Group dIs
to the Local Group dIs, we find that the Sculptor Group dIs have, on average,
lower values of SFR when normalized to either galaxy luminosity or gas mass
(although there is considerable overlap between the two samples). The
properties of ``transition'' (dSph/dIrr) galaxies in Sculptor and the Local
Group are also compared and found to be similar. The transition galaxies are
typically among the lowest luminosities of the gas rich dwarf galaxies.
Relative to the dwarf irregular galaxies, the transition galaxies are found
preferentially nearer to spiral galaxies, and are found nearer to the center of
the mass distribution in the local cloud. While most of these systems are
consistent with normal dI galaxies which currently exhibit temporarily
interrupted star formation, the observed density-morphology relationship (which
is weaker than that observed for the dwarf spheroidal galaxies) indicates that
environmental processes such as ``tidal stirring'' may play a role in causing
their lower SFRs.Comment: 35 pages, 10 figures, accepted for Feb 2003 AJ, companion to
astro-ph/021117
Expression and function of the bHLH genes ALCATRAZ and SPATULA in selected Solanaceae species
[EN] The genetic mechanisms underlying fruit development have been identified in Arabidopsis and have been comparatively studied in tomato as a representative of fleshy fruits. However, comparative expression and functional analyses on the bHLH genes downstream the genetic network, ALCATRAZ (ALC) and SPATULA (SPT), which are involved in the formation of the dehiscence zone in Arabidopsis, have not been functionally studied in the Solanaceae. Here, we perform detailed expression and functional studies of ALC/SPT homologs in Nicotiana obtusifolia with capsules, and in Capsicum annuum and Solanum lycopersicum with berries. In Solanaceae, ALC and SPT genes are expressed in leaves, and all floral organs, especially in petal margins, stamens and carpels; however, their expression changes during fruit maturation according to the fruit type. Functional analyses show that downregulation of ALC/SPT genes does not have an effect on gynoecium patterning; however, they have acquired opposite roles in petal expansion and have been co-opted in leaf pigmentation in Solanaceae. In addition, ALC/SPT genes repress lignification in time and space during fruit development in Solanaceae. Altogether, some roles of ALC and SPT genes are different between Brassicaceae and Solanaceae; while the paralogs have undergone some subfunctionalization in the former they are mostly redundant in the latter.This work was funded by COLCIENCIAS (111565842812), the iCOOP + 2016 COOPB20250 from the Centro Superior de InvestigaciĂłn CientĂfica, CSIC, the ExpoSeed (H2020.MSCA-RISE-2015-691109) EU grant, the Convocatoria ProgramĂĄticas 2017-16302, and the Estrategia de Sostenibilidad 2018-2019, from the Universidad de Antioquia. The authors would like to thank the group members of the FerrĂĄndiz and Madueño Labs at IBMCP-UPV for training and help in the standardization of in situ hybridization. Finally, the authors thank Ricardo Callejas and Zulma Monsalve, from the Universidad de Antioquia, for their helpful suggestions during this research.Ortiz-Ramirez, CI.; Giraldo, MA.; Ferrandiz Maestre, C.; Pabon-Mora, N. (2019). Expression and function of the bHLH genes ALCATRAZ and SPATULA in selected Solanaceae species. The Plant Journal. 99(4):686-702. https://doi.org/10.1111/tpj.14352S686702994Golam Masu, A. S. M., Khandaker, L., Berthold, J., Gates, L., Peters, K., Delong, H., & Hossain, K. (2011). Anthocyanin, Total Polyphenols and Antioxidant Activity of Common Bean. American Journal of Food Technology, 6(5), 385-394. doi:10.3923/ajft.2011.385.394Atchley, W. R., Terhalle, W., & Dress, A. (1999). Positional Dependence, Cliques, and Predictive Motifs in the bHLH Protein Domain. Journal of Molecular Evolution, 48(5), 501-516. doi:10.1007/pl00006494Ballester, P., & FerrĂĄndiz, C. (2017). Shattering fruits: variations on a dehiscent theme. Current Opinion in Plant Biology, 35, 68-75. doi:10.1016/j.pbi.2016.11.008Baudry, A., Heim, M. A., Dubreucq, B., Caboche, M., Weisshaar, B., & Lepiniec, L. (2004). TT2, TT8, and TTG1 synergistically specify the expression ofBANYULSand proanthocyanidin biosynthesis inArabidopsis thaliana. The Plant Journal, 39(3), 366-380. doi:10.1111/j.1365-313x.2004.02138.xBemer, M., Karlova, R., Ballester, A. R., Tikunov, Y. M., Bovy, A. G., Wolters-Arts, M., ⊠de Maagd, R. A. (2012). The Tomato FRUITFULL Homologs TDR4/FUL1 and MBP7/FUL2 Regulate Ethylene-Independent Aspects of Fruit Ripening. The Plant Cell, 24(11), 4437-4451. doi:10.1105/tpc.112.103283Besseau, S., Hoffmann, L., Geoffroy, P., Lapierre, C., Pollet, B., & Legrand, M. (2007). Flavonoid Accumulation in Arabidopsis Repressed in Lignin Synthesis Affects Auxin Transport and Plant Growth. The Plant Cell, 19(1), 148-162. doi:10.1105/tpc.106.044495Dardick, C., & Callahan, A. M. (2014). Evolution of the fruit endocarp: molecular mechanisms underlying adaptations in seed protection and dispersal strategies. Frontiers in Plant Science, 5. doi:10.3389/fpls.2014.00284Dardick, C. D., Callahan, A. M., Chiozzotto, R., Schaffer, R. J., Piagnani, M. C., & Scorza, R. (2010). Stone formation in peach fruit exhibits spatial coordination of the lignin and flavonoid pathways and similarity to Arabidopsisdehiscence. BMC Biology, 8(1). doi:10.1186/1741-7007-8-13Dinneny, J. R., Weigel, D., & Yanofsky, M. F. (2005). A genetic framework for fruit patterning inArabidopsis thaliana. Development, 132(21), 4687-4696. doi:10.1242/dev.02062Dong, Y., Burch-Smith, T. M., Liu, Y., Mamillapalli, P., & Dinesh-Kumar, S. P. (2007). A Ligation-Independent Cloning Tobacco Rattle Virus Vector for High-Throughput Virus-Induced Gene Silencing Identifies Roles for NbMADS4-1 and -2 in Floral Development. Plant Physiology, 145(4), 1161-1170. doi:10.1104/pp.107.107391Dong, T., Hu, Z., Deng, L., Wang, Y., Zhu, M., Zhang, J., & Chen, G. (2013). A Tomato MADS-Box Transcription Factor, SlMADS1, Acts as a Negative Regulator of Fruit Ripening. PLANT PHYSIOLOGY, 163(2), 1026-1036. doi:10.1104/pp.113.224436Feller, A., Machemer, K., Braun, E. L., & Grotewold, E. (2011). Evolutionary and comparative analysis of MYB and bHLH plant transcription factors. The Plant Journal, 66(1), 94-116. doi:10.1111/j.1365-313x.2010.04459.xFerrandiz, C. (2002). Regulation of fruit dehiscence in Arabidopsis. Journal of Experimental Botany, 53(377), 2031-2038. doi:10.1093/jxb/erf082FerraÌndiz, C., Liljegren, S. J., & Yanofsky, M. F. (2000). Negative Regulation of the
SHATTERPROOF
Genes by FRUITFULL During
Arabidopsis
Fruit Development. Science, 289(5478), 436-438. doi:10.1126/science.289.5478.436Fourquin, C., & FerrĂĄndiz, C. (2012). Functional analyses of AGAMOUS family members in Nicotiana benthamiana clarify the evolution of early and late roles of C-function genes in eudicots. The Plant Journal, 71(6), 990-1001. doi:10.1111/j.1365-313x.2012.05046.xFourquin, C., & FerrĂĄndiz, C. (2014). The essential role of
NGATHA
genes in style and stigma specification is widely conserved across eudicots. New Phytologist, 202(3), 1001-1013. doi:10.1111/nph.12703Fujisawa, M., Nakano, T., & Ito, Y. (2011). Identification of potential target genes for the tomato fruit-ripening regulator RIN by chromatin immunoprecipitation. BMC Plant Biology, 11(1). doi:10.1186/1471-2229-11-26Fujisawa, M., Shima, Y., Higuchi, N., Nakano, T., Koyama, Y., Kasumi, T., & Ito, Y. (2011). Direct targets of the tomato-ripening regulator RIN identified by transcriptome and chromatin immunoprecipitation analyses. Planta, 235(6), 1107-1122. doi:10.1007/s00425-011-1561-2Garceau, D. C., Batson, M. K., & Pan, I. L. (2017). Variations on a theme in fruit development: the PLE lineage of MADS-box genes in tomato (TAGL1) and other species. Planta, 246(2), 313-321. doi:10.1007/s00425-017-2725-5Girin, T., Paicu, T., Stephenson, P., Fuentes, S., Körner, E., OâBrien, M., ⊠Ăstergaard, L. (2011). INDEHISCENT and SPATULA Interact to Specify Carpel and Valve Margin Tissue and Thus Promote Seed Dispersal in Arabidopsis
 . The Plant Cell, 23(10), 3641-3653. doi:10.1105/tpc.111.090944Gomariz-FernĂĄndez, A., SĂĄnchez-Gerschon, V., Fourquin, C., & FerrĂĄndiz, C. (2017). The Role of SHI/STY/SRS Genes in Organ Growth and Carpel Development Is Conserved in the Distant Eudicot Species Arabidopsis thaliana and Nicotiana benthamiana. Frontiers in Plant Science, 8. doi:10.3389/fpls.2017.00814Gould, K. S. (2000). Functional role of anthocyanins in the leaves of Quintinia serrata A. Cunn. Journal of Experimental Botany, 51(347), 1107-1115. doi:10.1093/jexbot/51.347.1107Groszmann, M., Paicu, T., & Smyth, D. R. (2008). Functional domains of SPATULA, a bHLH transcription factor involved in carpel and fruit development in Arabidopsis. The Plant Journal, 55(1), 40-52. doi:10.1111/j.1365-313x.2008.03469.xGroszmann, M., Bylstra, Y., Lampugnani, E. R., & Smyth, D. R. (2010). Regulation of tissue-specific expression of SPATULA, a bHLH gene involved in carpel development, seedling germination, and lateral organ growth in Arabidopsis. Journal of Experimental Botany, 61(5), 1495-1508. doi:10.1093/jxb/erq015Groszmann, M., Paicu, T., Alvarez, J. P., Swain, S. M., & Smyth, D. R. (2011). SPATULA and ALCATRAZ, are partially redundant, functionally diverging bHLH genes required for Arabidopsis gynoecium and fruit development. The Plant Journal, 68(5), 816-829. doi:10.1111/j.1365-313x.2011.04732.xHorbowicz, M., Kosson, R., Grzesiuk, A., & DÄbski, H. (2008). Anthocyanins of Fruits and Vegetables - Their Occurrence, Analysis and Role in Human Nutrition. Journal of Fruit and Ornamental Plant Research, 68(1), 5-22. doi:10.2478/v10032-008-0001-8Ichihashi, Y., Horiguchi, G., Gleissberg, S., & Tsukaya, H. (2009). The bHLH Transcription Factor SPATULA Controls Final Leaf Size in Arabidopsis thaliana. Plant and Cell Physiology, 51(2), 252-261. doi:10.1093/pcp/pcp184Itkin, M., Seybold, H., Breitel, D., Rogachev, I., Meir, S., & Aharoni, A. (2009). TOMATO AGAMOUS-LIKEĂą 1 is a component of the fruit ripening regulatory network. The Plant Journal, 60(6), 1081-1095. doi:10.1111/j.1365-313x.2009.04064.xIto, Y., Nishizawa-Yokoi, A., Endo, M., Mikami, M., Shima, Y., Nakamura, N., ⊠Toki, S. (2017). Re-evaluation of the rin mutation and the role of RIN in the induction of tomato ripening. Nature Plants, 3(11), 866-874. doi:10.1038/s41477-017-0041-5KAY, Q. O. N., DAOUD, H. S., & STIRTON, C. H. (1981). Pigment distribution, light reflection and cell structure in petals. Botanical Journal of the Linnean Society, 83(1), 57-83. doi:10.1111/j.1095-8339.1981.tb00129.xLiljegren, S. J., Ditta, G. S., Eshed, Y., Savidge, B., Bowman, J. L., & Yanofsky, M. F. (2000). SHATTERPROOF MADS-box genes control seed dispersal in Arabidopsis. Nature, 404(6779), 766-770. doi:10.1038/35008089Liljegren, S. J., Roeder, A. H. ., Kempin, S. A., Gremski, K., Ăstergaard, L., Guimil, S., ⊠Yanofsky, M. F. (2004). Control of Fruit Patterning in Arabidopsis by INDEHISCENT. Cell, 116(6), 843-853. doi:10.1016/s0092-8674(04)00217-xLiu, E., & Page, J. E. (2008). Optimized cDNA libraries for virus-induced gene silencing (VIGS) using tobacco rattle virus. Plant Methods, 4(1), 5. doi:10.1186/1746-4811-4-5Liu, Y., Schiff, M., Marathe, R., & Dinesh-Kumar, S. P. (2002). Tobacco Rar1, EDS1 and NPR1/NIM1 like genes are required for N-mediated resistance to tobacco mosaic virus. The Plant Journal, 30(4), 415-429. doi:10.1046/j.1365-313x.2002.01297.xLivak, K. J., & Schmittgen, T. D. (2001). Analysis of Relative Gene Expression Data Using Real-Time Quantitative PCR and the 2âÎÎCT Method. Methods, 25(4), 402-408. doi:10.1006/meth.2001.1262Nesi, N., Debeaujon, I., Jond, C., Pelletier, G., Caboche, M., & Lepiniec, L. (2000). The TT8 Gene Encodes a Basic Helix-Loop-Helix Domain Protein Required for Expression of DFR and BAN Genes in Arabidopsis Siliques. The Plant Cell, 12(10), 1863-1878. doi:10.1105/tpc.12.10.1863Ortiz-RamĂrez, C. I., Plata-Arboleda, S., & PabĂłn-Mora, N. (2018). Evolution of genes associated with gynoecium patterning and fruit development in Solanaceae. Annals of Botany, 121(6), 1211-1230. doi:10.1093/aob/mcy007PabĂłn-Mora, N., & Litt, A. (2011). Comparative anatomical and developmental analysis of dry and fleshy fruits of Solanaceae. American Journal of Botany, 98(9), 1415-1436. doi:10.3732/ajb.1100097PabĂłn-Mora, N., Ambrose, B. A., & Litt, A. (2012). Poppy APETALA1/FRUITFULL Orthologs Control Flowering Time, Branching, Perianth Identity, and Fruit Development
Â
 . Plant Physiology, 158(4), 1685-1704. doi:10.1104/pp.111.192104Pan, I. L., McQuinn, R., Giovannoni, J. J., & Irish, V. F. (2010). Functional diversification of AGAMOUS lineage genes in regulating tomato flower and fruit development. Journal of Experimental Botany, 61(6), 1795-1806. doi:10.1093/jxb/erq046Penfield, S., Josse, E.-M., Kannangara, R., Gilday, A. D., Halliday, K. J., & Graham, I. A. (2005). Cold and Light Control Seed Germination through the bHLH Transcription Factor SPATULA. Current Biology, 15(22), 1998-2006. doi:10.1016/j.cub.2005.11.010Pires, N., & Dolan, L. (2009). Origin and Diversification of Basic-Helix-Loop-Helix Proteins in Plants. Molecular Biology and Evolution, 27(4), 862-874. doi:10.1093/molbev/msp288Rajani, S., & Sundaresan, V. (2001). The Arabidopsis myc/bHLH gene ALCATRAZ enables cell separation in fruit dehiscence. Current Biology, 11(24), 1914-1922. doi:10.1016/s0960-9822(01)00593-0Roeder, A. H. K., & Yanofsky, M. F. (2006). Fruit Development in Arabidopsis. The Arabidopsis Book, 4, e0075. doi:10.1199/tab.0075Roeder, A. H. K., FerrĂĄndiz, C., & Yanofsky, M. F. (2003). The Role of the REPLUMLESS Homeodomain Protein in Patterning the Arabidopsis Fruit. Current Biology, 13(18), 1630-1635. doi:10.1016/j.cub.2003.08.027Schulz, M., & Weissenböck, G. (1986). Isolation and Separation of Epidermal and Mesophyll Protoplasts from Rye Primary Leaves â Tissue-Specific Characteristics of Secondary Phenolic Product Accumulation. Zeitschrift fĂŒr Naturforschung C, 41(1-2), 22-27. doi:10.1515/znc-1986-1-205Seymour, G. B., Ăstergaard, L., Chapman, N. H., Knapp, S., & Martin, C. (2013). Fruit Development and Ripening. Annual Review of Plant Biology, 64(1), 219-241. doi:10.1146/annurev-arplant-050312-120057Smykal, P., Gennen, J., De Bodt, S., Ranganath, V., & Melzer, S. (2007). Flowering of strict photoperiodic Nicotiana varieties in non-inductive conditions by transgenic approaches. Plant Molecular Biology, 65(3), 233-242. doi:10.1007/s11103-007-9211-6Tani, E., Polidoros, A. N., & Tsaftaris, A. S. (2007). Characterization and expression analysis of FRUITFULL- and SHATTERPROOF-like genes from peach (Prunus persica) and their role in split-pit formation. Tree Physiology, 27(5), 649-659. doi:10.1093/treephys/27.5.649Tani, E., Tsaballa, A., Stedel, C., Kalloniati, C., Papaefthimiou, D., Polidoros, A., ⊠Tsaftaris, A. (2011). The study of a SPATULA-like bHLH transcription factor expressed during peach (Prunus persica) fruit development. Plant Physiology and Biochemistry, 49(6), 654-663. doi:10.1016/j.plaphy.2011.01.020Tisza, V., KovĂĄcs, L., Balogh, A., Heszky, L., & Kiss, E. (2010). Characterization of FaSPT, a SPATULA gene encoding a bHLH transcriptional factor from the non-climacteric strawberry fruit. Plant Physiology and Biochemistry, 48(10-11), 822-826. doi:10.1016/j.plaphy.2010.08.001Van der Kooi, C. J., Elzenga, J. T. M., Staal, M., & Stavenga, D. G. (2016). How to colour a flower: on the optical principles of flower coloration. Proceedings of the Royal Society B: Biological Sciences, 283(1830), 20160429. doi:10.1098/rspb.2016.0429Vrebalov, J., Ruezinsky, D., Padmanabhan, V., White, R., Medrano, D., Drake, R., ⊠Giovannoni, J. (2002). A MADS-Box Gene Necessary for Fruit Ripening at the Tomato
Ripening-Inhibitor
(
Rin
) Locus. Science, 296(5566), 343-346. doi:10.1126/science.1068181Vrebalov, J., Pan, I. L., Arroyo, A. J. M., McQuinn, R., Chung, M., Poole, M., ⊠Irish, V. F. (2009). Fleshy Fruit Expansion and Ripening Are Regulated by the Tomato SHATTERPROOF Gene TAGL1
Â
 . The Plant Cell, 21(10), 3041-3062. doi:10.1105/tpc.109.066936Xu, W., Dubos, C., & Lepiniec, L. (2015). Transcriptional control of flavonoid biosynthesis by MYBâbHLHâWDR complexes. Trends in Plant Science, 20(3), 176-185. doi:10.1016/j.tplants.2014.12.001Zumajo-Cardona, C., Ambrose, B. A., & PabĂłn-Mora, N. (2017). Evolution of the SPATULA/ALCATRAZ gene lineage and expression analyses in the basal eudicot, Bocconia frutescens L. (Papaveraceae). EvoDevo, 8(1). doi:10.1186/s13227-017-0068-
Control of surface plasmon resonance in out-diffused silver nanoislands for surface-enhanced Raman scattering
Abstract We present the studies of self-assembled silver nanoislands on the surface of silver ion-exchanged glasses. The nanoislands were formed by out-diffusion of reduced silver atoms from the bulk of the glass to its surface. Control of silver ions distribution in the glass by thermal poling after the ion exchange allowed formation of relatively big, up to 250 nm, isolated silver nanoislands while without the poling an ensemble of silver nanoislands with average size from several to tens of nanometers with random size distribution was formed. The nanoislands were characterized using atomic force microscopy and spectral measurements. We used optical absorption spectroscopy for ârandomâ nanoislands and dark field scattering spectroscopy for isolated ones, corresponding spectra showed peaks in the vicinity of 450 nm and 600 nm, respectively. The ârandomâ nanoislands significantly enhanced Raman scattering from Rhodamine 6G, also the modification of Raman signal from deposited on the surface of the samples bacteriorhodopsin in purple membranes was registered
Theoretical Modeling of Starburst Galaxies
We have modeled a large sample of infrared starburst galaxies using both the
PEGASE v2.0 and STARBURST99 codes to generate the spectral energy distribution
of the young star clusters. PEGASE utilizes the Padova group tracks while
STARBURST99 uses the Geneva group tracks, allowing comparison between the two.
We used our MAPPINGS III code to compute photoionization models which include a
self-consistent treatment of dust physics and chemical depletion. We use the
standard optical diagnostic diagrams as indicators of the hardness of the EUV
radiation field in these galaxies. These diagnostic diagrams are most sensitive
to the spectral index of the ionizing radiation field in the 1-4 Rydberg
region. We find that warm infrared starburst galaxies contain a relatively hard
EUV field in this region. The PEGASE ionizing stellar continuum is harder in
the 1-4 Rydberg range than that of STARBURST99. As the spectrum in this regime
is dominated by emission from Wolf-Rayet (W-R) stars, this difference is most
likely due to the differences in stellar atmosphere models used for the W-R
stars. We believe that the stellar atmospheres in STARBURST99 are more
applicable to the starburst galaxies in our sample, however they do not produce
the hard EUV field in the 1-4 Rydberg region required by our observations. The
inclusion of continuum metal blanketing in the models may be one solution.
Supernova remnant (SNR) shock modeling shows that the contribution by
mechanical energy from SNRs to the photoionization models is << 20%. The models
presented here are used to derive a new theoretical classification scheme for
starbursts and AGN galaxies based on the optical diagnostic diagrams.Comment: 36 pages, 16 figures, to be published in ApJ, July 20, 200
Intracerebroventricular Catalase Reduces Hepatic Insulin Sensitivity and Increases Responses to Hypoglycemia in Rats
Specialized metabolic-sensors in the hypothalamus regulate blood glucose levels by influencing hepatic glucose output and hypoglycemic counter regulatory responses. Hypothalamic reactive oxygen species (ROS) may act as a metabolic signal mediating responses to changes in glucose, other substrates and hormones. The role of ROS in the brain's control of glucose homeostasis remains unclear. We hypothesized that hydrogen peroxide (HO), a relatively stable form of ROS, acts as a sensor of neuronal glucose consumption and availability and that lowering brain HO with the enzyme catalase would lead to systemic responses increasing blood glucose. During hyperinsulinemic euglycemic clamps in rats, ICV catalase infusion resulted in increased hepatic glucose output, which was associated with reduced neuronal activity in the arcuate nucleus of the hypothalamus (ARC). Electrophysiological recordings revealed a subset of ARC neurons expressing pro-opiomelanocortin (POMC) that were inhibited by catalase and excited by HO. During hypoglycemic clamps, ICV catalase increased glucagon and epinephrine responses to hypoglycemia, consistent with perceived lower glucose levels. Our data suggest that HO represents an important metabolic cue which, through tuning the electrical activity of key neuronal populations such as POMC neurons, may have a role in the brain's influence of glucose homeostasis and energy balance.This work was supported by the Juvenile Diabetes Research Foundation Grant 1-2006-29 and the Diabetes UK Grant RD05/ 003059 (to M.L.E.), the Wellcome Trust Grant WT098012 (to L.K.H.), and Cambridge Medical Research Council Centre for Study of Obesity and Related Disorders. In addition, PhD studentships/fellowships were supported for S.P.M. (Elmore Fund), P.H. (Sir Jules Thorn Trust), and C.-Y.Y. (Chang Gung University College of Medicine Grant numbers CMRPG6B0291 and CMRPG6B0292)
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