Predicting substrate exchange in marine diatom-heterocystous cyanobacteria symbioses

In the open ocean, some phytoplankton establish symbiosis with cyanobacteria. Some partnerships involve diatoms as hosts and heterocystous cyanobacteria as symbionts. Heterocysts are specialized cells for nitrogen fixation, and a function of the symbiotic cyanobacteria is to provide the host with nitrogen. However, both partners are photosynthetic and capable of carbon fixation, and the possible metabolites exchanged and mechanisms of transfer are poorly understood. The symbiont cellular location varies from internal to partial to fully external, and this is reflected in the symbiont genome size and content. In order to identify the membrane transporters potentially involved in metabolite exchanges, we compare the draft genomes of three differently located symbionts with known transporters mainly from model free-living heterocystous cyanobacteria. The types and numbers of transporters are directly related to the symbiont cellular location: restricted in the endosymbionts and wider in the external symbiont. Three proposed models of metabolite exchanges are suggested which take into account the type of transporters in the symbionts and the influence of their cellular location on the available nutrient pools. These models provide a basis for several hypotheses that given the importance of these symbioses in global N and C budgets, warrant future testing. This article is protected by copyright. All rights reserved.España, Gobierno BFU2017-88202-

Musculoskeletal patients’ preferences for care from physiotherapists or support workers : a discrete choice experiment

Acknowledgements The authors would like to thank the study participants, members of the study’s Patient and Public Involvement and Engagement (PPIE) group and members of the study’s Clinical Advisory group for their valuable input and advice.Peer reviewe

Adaptation to an Intracellular Lifestyle by a Nitrogen-Fixing, Heterocyst-Forming Cyanobacterial Endosymbiont of a Diatom

The symbiosis between the diatom Hemiaulus hauckii and the heterocyst-forming cyanobacterium Richelia intracellularis makes an important contribution to new production in the world’s oceans, but its study is limited by short-term survival in the laboratory. In this symbiosis, R. intracellularis fixes atmospheric dinitrogen in the heterocyst and provides H. hauckii with fixed nitrogen. Here, we conducted an electron microscopy study of H. hauckii and found that the filaments of the R. intracellularis symbiont, typically composed of one terminal heterocyst and three or four vegetative cells, are located in the diatom’s cytoplasm not enclosed by a host membrane. A second prokaryotic cell was also detected in the cytoplasm of H. hauckii, but observations were infrequent. The heterocysts of R. intracellularis differ from those of free-living heterocyst-forming cyanobacteria in that the specific components of the heterocyst envelope seem to be located in the periplasmic space instead of outside the outer membrane. This specialized arrangement of the heterocyst envelope and a possible association of the cyanobacterium with oxygen-respiring mitochondria may be important for protection of the nitrogen-fixing enzyme, nitrogenase, from photosynthetically produced oxygen. The cell envelope of the vegetative cells of R. intracellularis contained numerous membrane vesicles that resemble the outer-inner membrane vesicles of Gram-negative bacteria. These vesicles can export cytoplasmic material from the bacterial cell and, therefore, may represent a vehicle for transfer of fixed nitrogen from R. intracellularis to the diatom’s cytoplasm. The specific morphological features of R. intracellularis described here, together with its known streamlined genome, likely represent specific adaptations of this cyanobacterium to an intracellular lifestyle

Low-Power Upconversion in Poly(Mannitol-Sebacate) Networks with Tethered Diphenylanthracene and Palladium Porphyrin

[EN] Efforts to fabricate low-power up converting solid-state systems have rapidly increased in the past decade because of their possible application in several fields such as bio-imaging, drug delivery, solar harvesting or displays. The synthesis of upconverting cross-linked polyester rubbers with covalently tethered chromophores is presented here. Cross-linked films were prepared by reacting a poly(mannitol- sebacate) pre-polymer with 9,10-bis(4-hydroxymethylphenyl) anthracene (DPA-(CH2OH)2) and palladium mesoporphyrin IX. These chromophores served as emitters and sensitizers, respectively, and through a cascade of photophysical events, resulted in an anti-Stokes shifted emission. Indeed, blue emission (*440 nm) of these solid materials was detected upon excitation at 543 nm with a green laser and the power dependence of integrated unconverted intensity versus excitation was examined. The new materials display upconversion at power densities as low as 32 mW/cm2, and do not display phase de-mixing, which has been identified as an obstacle in rubbery blends comprising untethered chromophores.The authors are thankful for the financial support of the Swiss National Science Foundation (200021_13540/1 and 200020_152968), Spanish Ministry of Economy and Competitiveness (Project MAT2010/21494-C03) and the Adolphe Merkle Foundation. The authors thank Prof. Christoph Weder for his help and support.Lee, S.; Sonseca, A.; Vadrucci, R.; Giménez Torres, E.; Foster, E.; Simon, YC. (2014). Low-Power Upconversion in Poly(Mannitol-Sebacate) Networks with Tethered Diphenylanthracene and Palladium Porphyrin. Journal of Inorganic and Organometallic Polymers. 24(5):898-903. https://doi.org/10.1007/s10904-014-0063-7S898903245C. A. Parker, C. G. Hatchard. P. Chem. Soc. London, 386–387 (1962)Y.C. Simon, C. Weder, J. Mater. Chem. 22, 20817–20830 (2012)J.Z. Zhao, S.M. Ji, H.M. 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Prospectus, February 28, 1990

https://spark.parkland.edu/prospectus_1990/1006/thumbnail.jp

Formation of lower bainite in a high carbon steel – an in-situ synchrotron XRD study

The microstructural evolution of and simultaneous dimensional changes in high-carbonSAE 52100 bearing steel were monitored continuously during austempering for 120 min atselected temperatures in the range of 210 C-270 C, and also during its subsequenttempering to 340 C for an additional 120 min, via high-energy X-ray diffraction in real timeand in-situ dilatometry. The austenite-to-bainitic ferrite transformation induces lattice defectsand internal lattice stresses that increase with austempering time and at lower austemperingtemperatures. These changes are evidenced by the increase in the full-width halfmaximumof the relevant reflections in X-ray diffraction. The lattice parameter of bainiticferrite takes its highest value during the early stages of austempering, and then graduallydecreases as the transformation progresses. This observation points to an initial state ofcarbon supersaturation in the ferritic lattice that is likely reducing due to carbon segregationclose to dislocations, fine carbide precipitation within the bainitic ferrite, and carbon partitioninginto the surrounding austenite. The carbon partitioning into austenite is evidencedin particular at the higher austempering temperatures of 240 C and 270 C, at which there isa noticeable increase in the lattice parameter of the remaining austenite at longer times. Thedimensions of the bearing steel specimens are governed by the volume change due to theformation of bainitic ferrite during austempering and by the relaxation of its lattice distortionduring tempering at 340 C in the absence of further phase transformation

Mechanical and Shape-Memory Properties of Poly(mannitol sebacate)/Cellulose Nanocrystal Nanocomposites

"This is the peer reviewed version of the following article: Sonseca, Á., Camarero‐Espinosa, S., Peponi, L., Weder, C., Foster, E. J., Kenny, J. M., & Giménez, E. (2014). Mechanical and shape‐memory properties of poly (mannitol sebacate)/cellulose nanocrystal nanocomposites. Journal of Polymer Science Part A: Polymer Chemistry, 52(21), 3123-3133., which has been published in final form at https://doi.org/10.1002/pola.27367. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."[EN] Polyesters based on polyols and sebacic acid, known as poly(polyol sebacate)s (PPS), are attracting considerable attention, as their properties are potentially useful in the context of soft-tissue engineering applications. To overcome the drawback that PPSs generally display rather low strength and stiffness, we have pursued the preparation of nano composites based poly(mannitol sebacate) (PMS), a prominent example of this materials family, with cellulose nanocrystals (CNCs). Nanocomposites were achieved in a two-step process. A soluble, low-molecular-weight PMS pre-polymer was formed via the polycondensation reaction between sebacic acid and D-mannitol. Nanocomposites with different CNC content were prepared by solution-casting and curing under vacuum using two different profiles designed to prepare materials with low and high degree of crosslinking. The as-prepared nano composites have higher stiffness and toughness than the neat PMS matrix while maintaining a high elongation at break. A highly crosslinked nanocomposite with a CNC content of 5 wt % displays a sixfold increase in Young s modulus and a fivefold improvement in toughness. Nanocomposites also exhibit a shape memory effect with a switch temperature in the range of 15 to 45 C; in particular the materials with a thermal transition in the upper part of this range are potentially useful for biomedical applicationsThe authors gratefully acknowledge financial support received from Spanish Ministry of Economy and Competitiveness (Project MAT2010/21494-C03), as well as the support of FPU grant from MED (MED-FPU; AP2009-2482), JAE-Doc grant (CSIC co-financed by FSE), Swiss National Science foundation (National Research Programme 64, Project #406440_131264/1) and the Adolphe Merkle Foundation.Sonseca, A.; Camarero-Espinosa, S.; Peponi, L.; Weder, C.; Foster, E.; Kenny, JM.; Giménez Torres, E. (2014). Mechanical and Shape-Memory Properties of Poly(mannitol sebacate)/Cellulose Nanocrystal Nanocomposites. Journal of Polymer Science Part A Polymer Chemistry. 52(21):3123-3133. https://doi.org/10.1002/pola.27367S312331335221Bruggeman, J. 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Acta Biomaterialia, 8(8), 2911-2918. doi:10.1016/j.actbio.2012.04.026Sun, Z.-J., Wu, L., Lu, X.-L., Meng, Z.-X., Zheng, Y.-F., & Dong, D.-L. (2008). The characterization of mechanical and surface properties of poly (glycerol–sebacate–lactic acid) during degradation in phosphate buffered saline. Applied Surface Science, 255(2), 350-352. doi:10.1016/j.apsusc.2008.06.157Liu, Q., Tan, T., Weng, J., & Zhang, L. (2009). Study on the control of the compositions and properties of a biodegradable polyester elastomer. Biomedical Materials, 4(2), 025015. doi:10.1088/1748-6041/4/2/025015SUNDBACK, C., SHYU, J., WANG, Y., FAQUIN, W., LANGER, R., VACANTI, J., & HADLOCK, T. (2005). Biocompatibility analysis of poly(glycerol sebacate) as a nerve guide material. Biomaterials, 26(27), 5454-5464. doi:10.1016/j.biomaterials.2005.02.004Sun, Z.-J., Chen, C., Sun, M.-Z., Ai, C.-H., Lu, X.-L., Zheng, Y.-F., … Dong, D.-L. (2009). The application of poly (glycerol–sebacate) as biodegradable drug carrier. 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Prospectus, October 16, 1985

https://spark.parkland.edu/prospectus_1985/1022/thumbnail.jp

Inverse dispersion engineering in silicon waveguides

We present a numerical tool that searches an optimal cross section geometry of silicon-on-insulator waveguides given a target dispersion profile. The approach is a gradient-based multidimensional method whose efficiency resides on the simultaneous calculation of the propagation constant derivatives with respect to all geometrical parameters of the structure by using the waveguide mode distribution. The algorithm is compatible with regular mode solvers. As an illustrative example, using a silicon slot hybrid waveguide with 4 independent degrees of freedom, our approach finds ultra-flattened (either normal or anomalous) dispersion over 350 nm bandwidth in less than 10 iterations