Earthshine observation of vegetation and implication for life detection on other planets - A review of 2001 - 2006 works

The detection of exolife is one of the goals of very ambitious future space missions that aim to take direct images of Earth-like planets. While associations of simple molecules present in the planet's atmosphere ($O_2$, $O_3$, $CO_2$ etc.) have been identified as possible global biomarkers, we review here the detectability of a signature of life from the planet's surface, i.e. the green vegetation. The vegetation reflectance has indeed a specific spectrum, with a sharp edge around 700 nm, known as the "Vegetation Red Edge" (VRE). Moreover vegetation covers a large surface of emerged lands, from tropical evergreen forest to shrub tundra. Thus considering it as a potential global biomarker is relevant. Earthshine allows to observe the Earth as a distant planet, i.e. without spatial resolution. Since 2001, Earthshine observations have been used by several authors to test and quantify the detectability of the VRE in the Earth spectrum. The egetation spectral signature is detected as a small 'positive shift' of a few percents above the continuum, starting at 700 nm. This signature appears in most spectra, and its strength is correlated with the Earth's phase (visible land versus visible ocean). The observations show that detecting the VRE on Earth requires a photometric relative accuracy of 1% or better. Detecting something equivalent on an Earth-like planet will therefore remain challenging, moreover considering the possibility of mineral artifacts and the question of 'red edge' universality in the Universe.Comment: Invited talk in "Strategies for Life Detection" (ISSI Bern, 24-28 April 2006) to appear in a hardcopy volume of the ISSI Space Science Series, Eds, J. Bada et al., and also in an issue of Space Science Reviews. 13 pages, 8 figures, 1 tabl

Sex Hormones Regulate Tenofovir-Diphosphate in Female Reproductive Tract Cells in Culture

The conflicting results of recent pre-exposure prophylaxis (PrEP) trials utilizing tenofovir (TFV) to prevent HIV infection in women led us to evaluate the accumulation of intracellular TFV-diphosphate (TFV-DP) in cells from the female reproductive tract (FRT) and whether sex hormones influence the presence of TFV-DP in these cells. Following incubation with TFV, isolated epithelial cells, fibroblasts, CD4+ T cells and CD14+ cells from the FRT as well as blood CD4+ T cells and monocyte-derived macrophages convert TFV to TFV-DP. Unexpectedly, we found that TFV-DP concentrations (fmol/million cells) vary significantly with the cell type analyzed and the site within the FRT. Epithelial cells had 5-fold higher TFV-DP concentrations than fibroblasts; endometrial epithelial cells had higher TFV-DP concentrations than cells from the ectocervix. Epithelial cells had 125-fold higher TFV-DP concentrations than FRT CD4+ T cells, which were comparable to that measured in peripheral blood CD4+ T cells. These findings suggest the existence of a TFV-DP gradient in the FRT where epithelial cells \u3e fibroblasts \u3e CD4+ T cells and macrophages. In other studies, estradiol increased TFV-DP concentrations in endometrial and endocervical/ectocervical epithelial cells, but had no effect on fibroblasts or CD4+ T cells from FRT tissues. In contrast, progesterone alone and in combination with estradiol decreased TFV-DP concentrations in FRT CD4+ T cells. Our results suggest that epithelial cells and fibroblasts are a repository of TFV-DP that is under hormonal control. These cells might act either as a sink to decrease TFV availability to CD4+ T cells and macrophages in the FRT, or upon conversion of TFV-DP to TFV increase TFV availability to HIV-target cells. In summary, these results indicate that intracellular TFV-DP varies with cell type and location in the FRT and demonstrate that estradiol and/or progesterone regulate the intracellular concentrations of TFV-DP in FRT epithelial cells and CD4+ T cells

Existence of Ricci flows of incomplete surfaces

We prove a general existence result for instantaneously complete Ricci flows starting at an arbitrary Riemannian surface which may be incomplete and may have unbounded curvature. We give an explicit formula for the maximal existence time, and describe the asymptotic behaviour in most cases.Comment: 20 pages; updated to reflect galley proof correction

Fermi Surface Measurements on the Low Carrier Density Ferromagnet Ca1-xLaxB6 and SrB6

Recently it has been discovered that weak ferromagnetism of a dilute 3D electron gas develops on the energy scale of the Fermi temperature in some of the hexaborides; that is, the Curie temperature approximately equals the Fermi temperature. We report the results of de Haas-van Alphen experiments on two concentrations of La-doped CaB6 as well as Ca-deficient Ca1-dB6 and Sr-deficient Sr1-dB6. The results show that a Fermi surface exists in each case and that there are significant electron-electron interactions in the low density electron gas.Comment: 4 pages, 5 figures, submitted to PR

Poly(vinylidene) fluoride membranes coated by heparin/collagen layer-by-layer, smart biomimetic approaches for mesenchymal stem cell culture

[EN] The use of piezoelectric materials in tissue engineering has grown considerably since inherent bone piezoelectricity was discovered. Combinations of piezoelectric polymers with magnetostrictive nanoparticles (MNP) can be used to magnetoelectrically stimulate cells by applying an external magnetic field which deforms the magnetostrictive nanoparticles in the polymer matrix, deforming the polymer itself, which varies the surface charge due to the piezoelectric effect. Poly(vinylidene) fluoride (PVDF) is the piezoelectric polymer with the largest piezoelectric coefficients, being a perfect candidate for osteogenic differentiation. As a first approach, in this paper, we propose PVDF membranes containing magnetostrictive nanoparticles and a biomimetic heparin/ collagen layer-by-layer (LbL) coating for mesenchymal stem cell culture. PVDF membranes 20% (w/v) with and without cobalt ferrite oxide (PVDF-CFO) 10% (w/w) were produced by non-solvent induced phase separation (NIPS). These membranes were found to be asymmetric, with a smooth surface, crystallinity ranging from 65% to 61%, and an electroactive beta-phase content of 51.8% and 55.6% for PVDF and PVDF-CFO, respectively. Amine groups were grafted onto the membrane surface by an alkali treatment, confirmed by ninhydrin test and X-ray photoelectron spectroscopy (XPS), providing positive charges for the assembly of heparin/collagen layers by the LbL technique. Five layers of each polyelectrolyte were deposited, ending with collagen. Human mesenchymal stem cells (hMSC) were used to test cell response in a short-term culture (1, 3 and 7 days). Nucleus cell counting showed that LbL favored cell proliferation in PVDF-CFO over non-coated membranes.This work has been funded by the Spanish State Research Agency (AEI) and the European Regional Development Fund (ERFD) through the PID2019-106099RB-C41/AEI/10.13039/501100011033 and PID2019-106099RB-C43/AEI/10.13039/501100011033 projects and the Associate Laboratory for Green Chemistry-LAQV financed by national funds from FCT/MCTES (UIDB/50006/2020). Maria GuillotFerriols acknowledges the Spanish Government funding of her doctoral thesis through a BES-2017-080398 FPI Grant. The CIBER-BBN (CB06/01/1026) initiative is funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program. CIBER actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. D.M.C is also grateful to the FCT-Fundacao para a Ciencia e Tecnologia for grant SFRH/BPD/121526/2016. Finally, the authors acknowledge funding from the Basque Government Industry and Education Department under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06) programs, respectively, also Dr. Carlos Sa (CEMUP) for assistance with the XPS analyses.Guillot-Ferriols, MT.; Rodriguez-Hernandez, J.; Correia, D.; Carabineiro, S.; Lanceros-Méndez, S.; Gómez Ribelles, JL.; Gallego Ferrer, G. (2020). Poly(vinylidene) fluoride membranes coated by heparin/collagen layer-by-layer, smart biomimetic approaches for mesenchymal stem cell culture. Materials Science and Engineering C: Materials for Biological Applications (Online). 117:1-12. https://doi.org/10.1016/j.msec.2020.111281112117Jacob, J., More, N., Kalia, K., & Kapusetti, G. (2018). Piezoelectric smart biomaterials for bone and cartilage tissue engineering. Inflammation and Regeneration, 38(1). doi:10.1186/s41232-018-0059-8Fukada, E., & Yasuda, I. (1957). On the Piezoelectric Effect of Bone. Journal of the Physical Society of Japan, 12(10), 1158-1162. doi:10.1143/jpsj.12.1158Martins, P., Lopes, A. C., & Lanceros-Mendez, S. (2014). Electroactive phases of poly(vinylidene fluoride): Determination, processing and applications. Progress in Polymer Science, 39(4), 683-706. doi:10.1016/j.progpolymsci.2013.07.006Gregorio, R. (2006). Determination of the α, β, and γ crystalline phases of poly(vinylidene fluoride) films prepared at different conditions. Journal of Applied Polymer Science, 100(4), 3272-3279. doi:10.1002/app.23137Sencadas, V., Gregorio, R., & Lanceros-Méndez, S. (2009). α to β Phase Transformation and Microestructural Changes of PVDF Films Induced by Uniaxial Stretch. Journal of Macromolecular Science, Part B, 48(3), 514-525. doi:10.1080/00222340902837527Gregorio, R., & Borges, D. S. (2008). Effect of crystallization rate on the formation of the polymorphs of solution cast poly(vinylidene fluoride). Polymer, 49(18), 4009-4016. doi:10.1016/j.polymer.2008.07.010Sencadas, V., Gregorio Filho, R., & Lanceros-Mendez, S. (2006). Processing and characterization of a novel nonporous poly(vinilidene fluoride) films in the β phase. Journal of Non-Crystalline Solids, 352(21-22), 2226-2229. doi:10.1016/j.jnoncrysol.2006.02.052Buonomenna, M. G., Macchi, P., Davoli, M., & Drioli, E. (2007). Poly(vinylidene fluoride) membranes by phase inversion: the role the casting and coagulation conditions play in their morphology, crystalline structure and properties. European Polymer Journal, 43(4), 1557-1572. doi:10.1016/j.eurpolymj.2006.12.033Ribeiro, C., Costa, C. M., Correia, D. M., Nunes-Pereira, J., Oliveira, J., Martins, P., … Lanceros-Méndez, S. (2018). Electroactive poly(vinylidene fluoride)-based structures for advanced applications. Nature Protocols, 13(4), 681-704. doi:10.1038/nprot.2017.157Liu, F., Hashim, N. A., Liu, Y., Abed, M. R. M., & Li, K. (2011). Progress in the production and modification of PVDF membranes. Journal of Membrane Science, 375(1-2), 1-27. doi:10.1016/j.memsci.2011.03.014Abzan, N., Kharaziha, M., & Labbaf, S. (2019). Development of three-dimensional piezoelectric polyvinylidene fluoride-graphene oxide scaffold by non-solvent induced phase separation method for nerve tissue engineering. Materials & Design, 167, 107636. doi:10.1016/j.matdes.2019.107636Young, T.-H., Chang, H.-H., Lin, D.-J., & Cheng, L.-P. (2010). Surface modification of microporous PVDF membranes for neuron culture. Journal of Membrane Science, 350(1-2), 32-41. doi:10.1016/j.memsci.2009.12.009Gonçalves, R., Martins, P., Correia, D. M., Sencadas, V., Vilas, J. L., León, L. M., … Lanceros-Méndez, S. (2015). Development of magnetoelectric CoFe2O4 /poly(vinylidene fluoride) microspheres. RSC Advances, 5(45), 35852-35857. doi:10.1039/c5ra04409jFernandes, M. M., Correia, D. M., Ribeiro, C., Castro, N., Correia, V., & Lanceros-Mendez, S. (2019). Bioinspired Three-Dimensional Magnetoactive Scaffolds for Bone Tissue Engineering. ACS Applied Materials & Interfaces, 11(48), 45265-45275. doi:10.1021/acsami.9b14001Hermenegildo, B., Ribeiro, C., Pérez-Álvarez, L., Vilas, J. L., Learmonth, D. A., Sousa, R. A., … Lanceros-Méndez, S. (2019). Hydrogel-based magnetoelectric microenvironments for tissue stimulation. Colloids and Surfaces B: Biointerfaces, 181, 1041-1047. doi:10.1016/j.colsurfb.2019.06.023Gonçalves, R., Martins, P., Moya, X., Ghidini, M., Sencadas, V., Botelho, G., … Lanceros-Mendez, S. (2015). Magnetoelectric CoFe2O4/polyvinylidene fluoride electrospun nanofibres. Nanoscale, 7(17), 8058-8061. doi:10.1039/c5nr00453eSilva, J. M., Reis, R. L., & Mano, J. F. (2016). Biomimetic Extracellular Environment Based on Natural Origin Polyelectrolyte Multilayers. Small, 12(32), 4308-4342. doi:10.1002/smll.201601355Costa, R. R., & Mano, J. F. (2014). Polyelectrolyte multilayered assemblies in biomedical technologies. Chemical Society Reviews, 43(10), 3453. doi:10.1039/c3cs60393hCastilla-Casadiego, D. A., Pinzon-Herrera, L., Perez-Perez, M., Quiñones-Colón, B. A., Suleiman, D., & Almodovar, J. (2018). Simultaneous characterization of physical, chemical, and thermal properties of polymeric multilayers using infrared spectroscopic ellipsometry. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 553, 155-168. doi:10.1016/j.colsurfa.2018.05.052Mhanna, R. F., Vörös, J., & Zenobi-Wong, M. (2011). Layer-by-Layer Films Made from Extracellular Matrix Macromolecules on Silicone Substrates. Biomacromolecules, 12(3), 609-616. doi:10.1021/bm1012772Billings, P. C., & Pacifici, M. (2015). Interactions of signaling proteins, growth factors and other proteins with heparan sulfate: mechanisms and mysteries. Connective Tissue Research, 56(4), 272-280. doi:10.3109/03008207.2015.1045066Chen, J., Huang, N., Li, Q., Chu, C. H., Li, J., & Maitz, M. F. (2016). The effect of electrostatic heparin/collagen layer-by-layer coating degradation on the biocompatibility. Applied Surface Science, 362, 281-289. doi:10.1016/j.apsusc.2015.11.227Zhang, K., Huang, D., Yan, Z., & Wang, C. (2017). Heparin/collagen encapsulating nerve growth factor multilayers coated aligned PLLA nanofibrous scaffolds for nerve tissue engineering. Journal of Biomedical Materials Research Part A, 105(7), 1900-1910. doi:10.1002/jbm.a.36053Ferreira, A. M., Gentile, P., Toumpaniari, S., Ciardelli, G., & Birch, M. A. (2016). Impact of Collagen/Heparin Multilayers for Regulating Bone Cellular Functions. ACS Applied Materials & Interfaces, 8(44), 29923-29932. doi:10.1021/acsami.6b09241Castilla-Casadiego, D. A., García, J. R., García, A. J., & Almodovar, J. (2019). Heparin/Collagen Coatings Improve Human Mesenchymal Stromal Cell Response to Interferon Gamma. ACS Biomaterials Science & Engineering, 5(6), 2793-2803. doi:10.1021/acsbiomaterials.9b00008Martins, P., Gonçalves, R., Lanceros-Mendez, S., Lasheras, A., Gutiérrez, J., & Barandiarán, J. M. (2014). Effect of filler dispersion and dispersion method on the piezoelectric and magnetoelectric response of CoFe2O4/P(VDF-TrFE) nanocomposites. Applied Surface Science, 313, 215-219. doi:10.1016/j.apsusc.2014.05.187Gamboa-Martínez, T. C., Luque-Guillén, V., González-García, C., Gómez Ribelles, J. L., & Gallego-Ferrer, G. (2014). Crosslinked fibrin gels for tissue engineering: Two approaches to improve their properties. Journal of Biomedical Materials Research Part A, 103(2), 614-621. doi:10.1002/jbm.a.35210Gregorio, Jr., R., & Cestari, M. (1994). Effect of crystallization temperature on the crystalline phase content and morphology of poly(vinylidene fluoride). Journal of Polymer Science Part B: Polymer Physics, 32(5), 859-870. doi:10.1002/polb.1994.090320509Martins, P., Costa, C. M., & Lanceros-Mendez, S. (2010). Nucleation of electroactive β-phase poly(vinilidene fluoride) with CoFe2O4 and NiFe2O4 nanofillers: a new method for the preparation of multiferroic nanocomposites. Applied Physics A, 103(1), 233-237. doi:10.1007/s00339-010-6003-7Qi, L., Knapton, E. K., Zhang, X., Zhang, T., Gu, C., & Zhao, Y. (2017). Pre-culture Sudan Black B treatment suppresses autofluorescence signals emitted from polymer tissue scaffolds. Scientific Reports, 7(1). doi:10.1038/s41598-017-08723-2Young, T.-H., Cheng, L.-P., Lin, D.-J., Fane, L., & Chuang, W.-Y. (1999). Mechanisms of PVDF membrane formation by immersion-precipitation in soft (1-octanol) and harsh (water) nonsolvents. Polymer, 40(19), 5315-5323. doi:10.1016/s0032-3861(98)00747-2Cheng, L.-P. (1999). Effect of Temperature on the Formation of Microporous PVDF Membranes by Precipitation from 1-Octanol/DMF/PVDF and Water/DMF/PVDF Systems. Macromolecules, 32(20), 6668-6674. doi:10.1021/ma990418lSupriya, S., Kumar, L., & Kar, M. (2018). Optimization of dielectric properties of PVDF-CFO nanocomposites. Polymer Composites, 40(3), 1239-1250. doi:10.1002/pc.24840Lin, D.-J., Beltsios, K., Young, T.-H., Jeng, Y.-S., & Cheng, L.-P. (2006). Strong effect of precursor preparation on the morphology of semicrystalline phase inversion poly(vinylidene fluoride) membranes. Journal of Membrane Science, 274(1-2), 64-72. doi:10.1016/j.memsci.2005.07.043Cai, X., Lei, T., Sun, D., & Lin, L. (2017). A critical analysis of the α, β and γ phases in poly(vinylidene fluoride) using FTIR. RSC Advances, 7(25), 15382-15389. doi:10.1039/c7ra01267eBoccaccio, T., Bottino, A., Capannelli, G., & Piaggio, P. (2002). Characterization of PVDF membranes by vibrational spectroscopy. Journal of Membrane Science, 210(2), 315-329. doi:10.1016/s0376-7388(02)00407-6Liu, J., Lu, X., & Wu, C. (2013). Effect of Preparation Methods on Crystallization Behavior and Tensile Strength of Poly(vinylidene fluoride) Membranes. Membranes, 3(4), 389-405. doi:10.3390/membranes3040389ZHANG, M., ZHANG, A., ZHU, B., DU, C., & XU, Y. (2008). Polymorphism in porous poly(vinylidene fluoride) membranes formed via immersion precipitation process. Journal of Membrane Science, 319(1-2), 169-175. doi:10.1016/j.memsci.2008.03.029Xiao, L., Davenport, D. M., Ormsbee, L., & Bhattacharyya, D. (2015). Polymerization and Functionalization of Membrane Pores for Water Related Applications. Industrial & Engineering Chemistry Research, 54(16), 4174-4182. doi:10.1021/ie504149tDuca, M. D., Plosceanu, C. L., & Pop, T. (1998). Effect of X-rays on poly(vinylidene fluoride) in X-ray photoelectron spectroscopy. Journal of Applied Polymer Science, 67(13), 2125-2129. doi:10.1002/(sici)1097-4628(19980328)67:133.0.co;2-gCorreia, D. M., Ribeiro, C., Sencadas, V., Botelho, G., Carabineiro, S. A. C., Ribelles, J. L. G., & Lanceros-Méndez, S. (2015). Influence of oxygen plasma treatment parameters on poly(vinylidene fluoride) electrospun fiber mats wettability. Progress in Organic Coatings, 85, 151-158. doi:10.1016/j.porgcoat.2015.03.019Kehrer, M., Duchoslav, J., Hinterreiter, A., Cobet, M., Mehic, A., Stehrer, T., & Stifter, D. (2019). XPS investigation on the reactivity of surface imine groups with TFAA. Plasma Processes and Polymers, 16(4), 1800160. doi:10.1002/ppap.201800160Morales-Román, R. M., Guillot-Ferriols, M., Roig-Pérez, L., Lanceros-Mendez, S., Gallego-Ferrer, G., & Gómez Ribelles, J. L. (2019). Freeze-extraction microporous electroactive supports for cell culture. European Polymer Journal, 119, 531-540. doi:10.1016/j.eurpolymj.2019.07.011Camacho, N. P., West, P., Torzilli, P. A., & Mendelsohn, R. (2000). FTIR microscopic imaging of collagen and proteoglycan in bovine cartilage. Biopolymers, 62(1), 1-8. doi:10.1002/1097-0282(2001)62:13.0.co;2-oRibeiro, C., Panadero, J. A., Sencadas, V., Lanceros-Méndez, S., Tamaño, M. N., Moratal, D., … Gómez Ribelles, J. L. (2012). Fibronectin adsorption and cell response on electroactive poly(vinylidene fluoride) films. Biomedical Materials, 7(3), 035004. doi:10.1088/1748-6041/7/3/035004Ribeiro, C., Pärssinen, J., Sencadas, V., Correia, V., Miettinen, S., Hytönen, V. P., & Lanceros‐Méndez, S. (2014). Dynamic piezoelectric stimulation enhances osteogenic differentiation of human adipose stem cells. Journal of Biomedical Materials Research Part A, 103(6), 2172-2175. doi:10.1002/jbm.a.35368Sobreiro-Almeida, R., Tamaño-Machiavello, M., Carvalho, E., Cordón, L., Doria, S., Senent, L., … Sempere, A. (2017). Human Mesenchymal Stem Cells Growth and Osteogenic Differentiation on Piezoelectric Poly(vinylidene fluoride) Microsphere Substrates. International Journal of Molecular Sciences, 18(11), 2391. doi:10.3390/ijms18112391Moise, S., Céspedes, E., Soukup, D., Byrne, J. M., El Haj, A. J., & Telling, N. D. (2017). The cellular magnetic response and biocompatibility of biogenic zinc- and cobalt-doped magnetite nanoparticles. Scientific Reports, 7(1). doi:10.1038/srep3992

Laser-induced collective excitations in a two-component Fermi gas

We consider the linear density response of a two-component (superfluid) Fermi gas of atoms when the perturbation is caused by laser light. We show that various types of laser excitation schemes can be transformed into linear density perturbations, however, a Bragg spectroscopy scheme is needed for transferring energy and momentum into a collective mode. This makes other types of laser probing schemes insensitive for collective excitations and therefore well suited for the detection of the superfluid order parameter. We show that for the special case when laser light is coupled between the two components of the Fermi gas, density response is always absent in a homogeneous system.Comment: 6 pages, no figure