One Solar Cycle of Heliosphere Observations with the Interstellar Boundary Explorer: Energetic Neutral Hydrogen Atoms Observed with IBEX-Lo from 10 eV to 2 keV

The Interstellar Boundary Explorer (IBEX) is a NASA satellite in Earth orbit, dedicated to observing both interstellar neutral atoms entering the heliosphere and energetic neutral atoms (ENAs) from the interstellar boundaries from roughly 10 eV to 6 keV. This work presents the averaged maps, energy spectra, and temporal variability of heliospheric ENA intensities measured with the IBEX-Lo instrument at 1 au at energies between 10 eV and 2 keV, covering one entire solar cycle from 2009 through 2019. These results expand the range in time and energy for studying the globally distributed ENA flux and the IBEX Ribbon. The observed ENA intensities exceed model predictions, in particular below 500 eV. Moreover, the ENA intensities between 50–200 eV energy show an unexpected rise and fall around the year 2015 in most sky regions

Differential Cathelicidin Expression in Duodenal and Gastric Biopsies from Tanzanian and German Patients

Epithelial surfaces such as the gastrointestinal mucosa depend on expression of antimicrobial peptides like cathelicidin for immune defence against pathogens. The mechanisms behind mucosal cathelicidin regulation are incompletely understood. Cathelicidin expression was analysed in duodenal, antral and corpus/fundic mucosal biopsies from African and German patients. Additionally, cathelicidin expression was correlated with Helicobacter pylori (HP) infection and the inflammatory status of the mucosa. High cathelicidin transcript abundance was detected in duodenal biopsies from African subjects. On the contrary, cathelicidin mRNA expression was either undetectable or very low in tissue specimens from German patients. Also, in the antrum and corpus/fundus regions of the stomach significantly higher cathelicidin transcript levels were measured in Tanzanian compared to German patients. In gastric biopsies from African patients cathelicidin expression was increased in HP positive compared to HP negative subjects. Additionally, the inflammatory status measured by IL-8 expression correlated well with the HP infection status. A higher duodenal and gastric cathelicidin expression in African (compared with European) individuals may be due to upregulation by antigenic stimulation and may confer a higher resistance against enteric infections

A combination of three surface modifiers for the optimal generation and application of natural hybrid nanopigments in a biodegradable resin

Our purpose was to improve the thermal, mechanical and optimal properties of an epoxy bioresin using optimum hybrid natural pigments previously synthesised in our lab. Next, we searched for the best combinations of factors in the synthesis of natural hybrid nanopigments and then incorporated them into the bioresin. We combined three structural modifiers in the nanopigment synthesis, surfactant, coupling agent (silane) and a mordant salt (alum), selected to replicate mordant textile dyeing with natural dyes. We used Taguchi s design L8 to seek final performance optimisation. We selected three natural dyes, chlorophyll, beta-carotene and beetroot extract, and used two laminar nanoclay types, montmorillonite and hydrotalcite. The thermal, mechanical and colorimetric characterisation of the composite obtained by mixing natural hybrid nanopigments (bionanocomposite) was made. The natural dye interactions with both nanoclays improved the thermal stabilities, colour performance and UV VIS light exposure stability of natural dyes and bioresins. The best bionanocomposite materials were found in an acidic pH [3, 4] environment and by modifying nanoclays with mordant and surfactant during the nanopigment synthesis processWe thank the Spanish Ministry of Economy and Competitiveness for funding Projects DPI2011-30090-C02-02 and DPI2015-68514-R.Micó Vicent, B.; Jordán Núñez, J.; Martinez Verdu, FM.; Balart Gimeno, RA. (2017). A combination of three surface modifiers for the optimal generation and application of natural hybrid nanopigments in a biodegradable resin. Journal of Materials Science. 52(2):889-898. https://doi.org/10.1007/s10853-016-0384-8S889898522Majdzadeh-Ardakani K, Nazari B (2010) Improving the mechanical properties of thermoplastic starch/poly(vinyl alcohol)/clay nanocomposites. Compos Sci Technol 70(10):1557–1563. doi: 10.1016/j.compscitech.2010.05.022Najafi N, Heuzey MC, Carreau PJ (2012) Polylactide (PLA)-clay nanocomposites prepared by melt compounding in the presence of a chain extender. Compos Sci Technol 72(5):608–615. doi: 10.1016/j.compscitech.2012.01.005Acharya H, Srivastava SK, Bhowmick AK (2007) Synthesis of partially exfoliated EPDM/LDH nanocomposites by solution intercalation: structural characterization and properties. Compos Sci Technol 67(13):2807–2816. doi: 10.1016/j.compscitech.2007.01.030Marras SI, Zuburtikudis I, Panayiotou C (2007) Nanostructure vs. microstructure: morphological and thermomechanical characterization of poly(L-lactic acid)/layered silicate hybrids. Eur Polymer J 43(6):2191–2206. doi: 10.1016/j.eurpolymj.2007.03.013Leszczyńska A, Njuguna J, Pielichowski K, Banerjee JR (2007) Polymer/montmorillonite nanocomposites with improved thermal properties: Part I. Factors influencing thermal stability and mechanisms of thermal stability improvement. Thermochim Acta 453(2):75–96. doi: 10.1016/j.tca.2006.11.002Park HM, Lee WK, Park CY, Cho WJ, Ha CS (2003) Environmentally friendly polymer hybrids Part I Mechanical, thermal, and barrier properties of thermoplastic starch/clay nanocomposites. J Mater Sci 38(5):909–915. doi: 10.1023/a:1022308705231Porter D, Metcalfe E, Thomas MJK (2000) Nanocomposite fire retardants—a review. Fire Mater 24(1):45–52. doi: 10.1002/(sici)1099-1018(200001/02)24:13.0.co;2-sRay SS, Okamoto M (2003) Polymer/layered silicate nanocomposites: a review from preparation to processing. Prog Polym Sci 28(11):1539–1641. doi: 10.1016/j.progpolymsci.2003.08.002Gao D, Li R, Lv B, Ma J, Tian F, Zhang J (2015) Flammability, thermal and physical-mechanical properties of cationic polymer/montmorillonite composite on cotton fabric. Compos B Eng 77:329–337. doi: 10.1016/j.compositesb.2015.03.061LeBaron PC, Wang Z, Pinnavaia TJ (1999) Polymer-layered silicate nanocomposites: an overview. Appl Clay Sci 15(1–2):11–29. doi: 10.1016/s0169-1317(99)00017-4Karuntarut Sermsantiwanita SP (2012) Preparation of bio-based nanocomposite emulsions: effect of clay type. Prog Org Coat 74:660–666Pascual J, Fages E, Fenollar O, Garcia D, Balart R (2009) Influence of the compatibilizer/nanoclay ratio on final properties of polypropylene matrix modified with montmorillonite-based organoclay. Polym Bull 62(3):367–380. doi: 10.1007/s00289-008-0018-7Beltrán MI, Benavente V, Marchante V, Marcilla A (2013) The influence of surfactant loading level in a montmorillonite on the thermal, mechanical and rheological properties of EVA nanocomposites. Appl Clay Sci 83–84:153–161. doi: 10.1016/j.clay.2013.08.028Bitinis N, Verdejo R, Maya EM, Espuche E, Cassagnau P, Lopez-Manchado MA (2012) Physicochemical properties of organoclay filled polylactic acid/natural rubber blend bionanocomposites. Compos Sci Technol 72(2):305–313. doi: 10.1016/j.compscitech.2011.11.018Sanchez-Garcia MD, Lopez-Rubio A, Lagaron JM (2010) Natural micro and nanobiocomposites with enhanced barrier properties and novel functionalities for food biopackaging applications. Trends Food Sci Technol 21(11):528–536. doi: 10.1016/j.tifs.2010.07.008Huskić M, Žigon M, Ivanković M (2013) Comparison of the properties of clay polymer nanocomposites prepared by montmorillonite modified by silane and by quaternary ammonium salts. Appl Clay Sci 85:109–115. doi: 10.1016/j.clay.2013.09.004Osman MA, Rupp JEP, Suter UW (2005) Effect of non-ionic surfactants on the exfoliation and properties of polyethylene-layered silicate nanocomposites. Polymer 46(19):8202–8209. doi: 10.1016/j.polymer.2005.06.101Wang H, Fang P, Chen Z, Wang S, Xu Y, Fang Z (2008) Effect of silane grafting on the microstructure of high-density polyethylene/organically modified montmorillonite nanocomposites. Polym Int 57(1):50–56. doi: 10.1002/pi.2310Montgomery DC (2008) Design and analysis of experiments. Wiley, HobokenBaena-Murillo E, Micó-Vicent B, Martínez-Verdú FM (2013) Method for the synthesis of nanostructured hybrid pigments having properties that can be syntonized. https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2013110841&recNum=229&docAn=ES2013070026&queryString=(ANA:ES)&maxRec=25813Kohno Y, Inagawa M, Ikoma S, Shibata M, Matsushima R, Fukuhara C, Tomita Y, Maeda Y, Kobayashi K (2011) Stabilization of a hydrophobic natural dye by intercalation into organo-montmorillonite. 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Searches for Neutrinos from Gamma-Ray Bursts Using the IceCube Neutrino Observatory

Gamma-ray bursts (GRBs) are considered as promising sources of ultra-high-energy cosmic rays (UHECRs) due to their large power output. Observing a neutrino flux from GRBs would offer evidence that GRBs are hadronic accelerators of UHECRs. Previous IceCube analyses, which primarily focused on neutrinos arriving in temporal coincidence with the prompt gamma-rays, found no significant neutrino excess. The four analyses presented in this paper extend the region of interest to 14 days before and after the prompt phase, including generic extended time windows and targeted precursor searches. GRBs were selected between 2011 May and 2018 October to align with the data set of candidate muon-neutrino events observed by IceCube. No evidence of correlation between neutrino events and GRBs was found in these analyses. Limits are set to constrain the contribution of the cosmic GRB population to the diffuse astrophysical neutrino flux observed by IceCube. Prompt neutrino emission from GRBs is limited to ≲1% of the observed diffuse neutrino flux, and emission on timescales up to 104 s is constrained to 24% of the total diffuse flux.Peer Reviewe

IceCube Search for Neutrinos Coincident with Compact Binary Mergers from LIGO-Virgo's First Gravitational-Wave Transient Catalog

Using the IceCube Neutrino Observatory, we search for high-energy neutrino emission coincident with compact binary mergers observed by the LIGO and Virgo gravitational wave (GW) detectors during their first and second observing runs. We present results from two searches targeting emission coincident with the sky localization of each gravitational wave event within a 1000 second time window centered around the reported merger time. One search uses a model-independent unbinned maximum likelihood analysis, which uses neutrino data from IceCube to search for point-like neutrino sources consistent with the sky localization of GW events. The other uses the Low-Latency Algorithm for Multi-messenger Astrophysics, which incorporates astrophysical priors through a Bayesian framework and includes LIGO-Virgo detector characteristics to determine the association between the GW source and the neutrinos. No significant neutrino coincidence is seen by either search during the first two observing runs of the LIGO-Virgo detectors. We set upper limits on the time-integrated neutrino emission within the 1000 second window for each of the 11 GW events. These limits range from 0.02-0.7 $\mathrm{GeV~cm^{-2}}$. We also set limits on the total isotropic equivalent energy, $E_{\mathrm{iso}}$, emitted in high-energy neutrinos by each GW event. These limits range from 1.7 $\times$ 10$^{51}$ - 1.8 $\times$ 10$^{55}$ erg. We conclude with an outlook for LIGO-Virgo observing run O3, during which both analyses are running in real time

Search for PeV gamma-ray emission from the southern hemisphere with 5 Yr of data from the IceCube observatory

The measurement of diffuse PeV gamma-ray emission from the Galactic plane would provide information about the energy spectrum and propagation of Galactic cosmic rays, and the detection of a pointlike source of PeV gamma-rays would be strong evidence for a Galactic source capable of accelerating cosmic rays up to at least a few PeV. This paper presents several unbinned maximum-likelihood searches for PeV gamma-rays in the Southern Hemisphere using 5 yr of data from the IceTop air shower surface detector and the in-ice array of the IceCube Observatory. The combination of both detectors takes advantage of the low muon content and deep shower maximum of gamma-ray air showers and provides excellent sensitivity to gamma-rays between similar to 0.6 and 100 PeV. Our measurements of pointlike and diffuse Galactic emission of PeV gamma-rays are consistent with the background, so we constrain the angle-integrated diffuse gamma-ray flux from the Galactic plane at 2 PeV to 2.61 x 10(-19) cm(-2) s(-1) TeV-1 at 90% confidence, assuming an E-3 spectrum, and we estimate 90% upper limits on pointlike emission at 2 PeV between 10(-21) and 10(-20) cm(-2) s(-1) TeV-1 for an E-2 spectrum, depending on decl. Furthermore, we exclude unbroken power-law emission up to 2 PeV for several TeV gamma-ray sources observed by the High Energy Spectroscopic System and calculate upper limits on the energy cutoffs of these sources at 90% confidence. We also find no PeV gamma-rays correlated with neutrinos from IceCube's high-energy starting event sample. These are currently the strongest constraints on PeV gamma-ray emission

Characteristics of the diffuse astrophysical electron and tau neutrino flux with six years of IceCube high energy cascade data

We report on the first measurement of the astrophysical neutrino flux using particle showers (cascades) in IceCube data from 2010 -- 2015. Assuming standard oscillations, the astrophysical neutrinos in this dedicated cascade sample are dominated ($\sim 90 \%$) by electron and tau flavors. The flux, observed in the sensitive energy range from $16\,\mathrm{TeV}$ to $2.6\,\mathrm{PeV}$, is consistent with a single power-law model as expected from Fermi-type acceleration of high energy particles at astrophysical sources. We find the flux spectral index to be $\gamma=2.53\pm0.07$ and a flux normalization for each neutrino flavor of $\phi_{astro} = 1.66^{+0.25}_{-0.27}$ at $E_{0} = 100\, \mathrm{TeV}$, in agreement with IceCube's complementary muon neutrino results and with all-neutrino flavor fit results. In the measured energy range we reject spectral indices $\gamma\leq2.28$ at $\ge3\sigma$ significance level. Due to high neutrino energy resolution and low atmospheric neutrino backgrounds, this analysis provides the most detailed characterization of the neutrino flux at energies below $\sim100\,{\rm{TeV}}$ compared to previous IceCube results. Results from fits assuming more complex neutrino flux models suggest a flux softening at high energies and a flux hardening at low energies (p-value $\ge 0.06$). The sizable and smooth flux measured below $\sim 100\,{\rm{TeV}}$ remains a puzzle. In order to not violate the isotropic diffuse gamma-ray background as measured by the Fermi-LAT, it suggests the existence of astrophysical neutrino sources characterized by dense environments which are opaque to gamma-rays.Comment: 4 figures, 4 tables, includes supplementary materia

IceCube Search for High-Energy Neutrino Emission from TeV Pulsar Wind Nebulae

Pulsar wind nebulae (PWNe) are the main gamma-ray emitters in the Galactic plane. They are diffuse nebulae that emit nonthermal radiation. Pulsar winds, relativistic magnetized outflows from the central star, shocked in the ambient medium produce a multiwavelength emission from the radio through gamma rays. Although the leptonic scenario is able to explain most PWNe emission, a hadronic contribution cannot be excluded. A possible hadronic contribution to the high-energy gamma-ray emission inevitably leads to the production of neutrinos. Using 9.5 yr of all-sky IceCube data, we report results from a stacking analysis to search for neutrino emission from 35 PWNe that are high-energy gamma-ray emitters. In the absence of any significant correlation, we set upper limits on the total neutrino emission from those PWNe and constraints on hadronic spectral components.Comment: 11 pages, 2 figures; matches the published version in Ap