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Vase-like β-Polymorph Guanine Crystal Aggregates Formed at the Air–Water Interface
No full textGuanine in the anhydrous β-form is a common light manipulator in organisms to produce structural colors for a variety of purposes. The level of control over crystal nucleation and growth of guanine exhibited by these organisms to produce crystals with precise morphology, size, and polymorphism far surpasses what has so far been achieved synthetically from aqueous solution. Here, we show that the morphology of guanine crystals can be altered significantly by inducing crystallization at the air–water interface to produce vase-like morphologies with a few hundred nanometers thick, micron-longcrystals pointing away from the vase opening. The exact morphology is highly dependent on the initial guanine concentration with increasing templating efficiency from the air–water interface at decreasing sample volumes. Scanning nanobeam X-ray diffraction experiments reveal that the vases consist exclusively of the anhydrous β-polymorph and that the crystal long axes coincide with a*. While the morphology does not match the biogenic counterparts that usually are thin along a*, the results demonstrate that interfacial crystallization templates the aggregate morphology and dictates the polymorph of guanine
Improved constraints on parton distributions using LHCb, ALICE and HERA heavy-flavour measurements and implications for the predictions for prompt atmospheric-neutrino fluxes
No full textThe impact of measurements of heavy-flavour production in deep inelastic ep scattering and in pp collisions on parton distribution functions is studied in a QCD analysis at next-to-leading order. Recent combined results of inclusive and heavy-flavour produc- tion cross sections in deep inelastic scattering at HERA are investigated together with heavy-flavour production measurements at the LHC. Differential cross sections of charm- and beauty-hadron production measured by the LHCb collaboration at the centre-of-mass energies of 5, 7 and 13 TeV as well as the recent measurements of the ALICE experiment at the centre-of-mass energies of 5 and 7 TeV are explored. These data impose additional constraints on the gluon and the sea-quark distributions at low partonic fractions x of the proton momentum, down to x ≈ 10. The impact of the resulting parton distribution function in the predictions for the prompt atmospheric-neutrino fluxes is studied.[graphic not available: see fulltext
Influence of TMAO as co-solvent on the gelation of silica-PNIPAm core-shell nanogels at intermediate volume fractions
No full textWe study the structure and dynamics of poly(N‐isopropylacrylamide) (PNIPAm) core‐shell nanogels dispersed in aqueous trimethylamine N‐oxide (TMAO) solutions by means of small‐angle X‐ray scattering and X‐ray photon correlation spectroscopy (XPCS). Upon increasing the temperature above the lower critical solution temperature of PNIPAm at 33 °C, a colloidal gel is formed as identified by an increase of I (q ) at small q as well as a slowing down of sample dynamics by various orders of magnitude. With increasing TMAO concentration the gelation transition shifts linearly to lower temperatures. Above a TMAO concentration of approximately 0.40 mol/L corresponding to a 1 : 1 ratio of TMAO and NIPAm groups, collapsed PNIPAm states are found for all temperatures without any gelation transition. This suggests that reduction of PNIPAm‐water hydrogen bonds due to the presence of TMAO results in a stabilisation of the collapsed PNIPAm state and suppresses gelation of the nanogel
Coherent modulation of the electron temperature and electron–phonon couplings in a 2D material
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Use of synergistic mixture of chelating agents for in situ LDH growth on the surface of PEO-treated AZ91
No full textThe principal possibility to grow layered double hydroxide (LDH) at ambient pressure on plasma electrolytic oxidation (PEO) treated magnesium alloy AZ91 in the presence of chelating agents is demonstrated for the first time. It avoids hydrothermal autoclave conditions, which strongly limit wide industrial application of such coating systems, and the presence of carbonate ions in the electrolyte, which lead to the formation of “passive” non-functionalizable LDH. A combination of chelating agents (sodium diethylenetriamine-pentaacetate (DTPA) and salicylate) were introduced to the treatment solution. The role of each additive and the influence of treatment bath composition on the LDH formation processes are discussed. A synergistic effect of DTPA and salicylate during LDH formation is discovered and its possible explanation is proposed
Compression behavior of dense mixtures up to 160 GPa
No full textWe have studied the compression behavior of H2-He mixtures in comparison with pure H2and He usingpowder synchrotron x-ray diffraction, and we present the pressure-volume (PV) compression data of H2-Hemixtures to 160 GPa. The results indicate that both H2andHeinH2-He mixtures remain in hcp to the maximumpressure studied, yet they develop a substantial level of lattice distortion in the (100) plane, most profound inHe-rich solids and below 66 GPa. The measured PV data also indicate the softening of an He (or H2) -rich latticeupon increasing the level of the guest H2(or He) concentration. We suggest that the observed softening and latticedistortion are due to a substitutional incorporation of H2(guest) molecules into the basal plane of the hcp-He(host) lattice, and thereby reflect the miscibility between H2andHeinH2-He mixtures. Interestingly, solid Heexhibits a lesser degree of preferred orientation in H2-He mixtures than in pure He, likely due to the presence ofsolid H2disturbing the crystalline ordering of He-rich solids. Finally, the present PV compression data of H2-richand He-rich solids to 160 GPa deviate from those of pure H2andpureHeabove∼70 and 45 GPa respectively,providing new constraints for the development of the equation of state for H2-He mixtures for planetary models
Dependence of inclusive jet production on the anti- distance parameter in pp collisions at 13 TeV
No full textThe dependence of inclusive jet production in proton-proton collisions with a center-of-mass energy of 13 TeV on the distance parameter of the anti- algorithm is studied using data corresponding to integrated luminosities up to 35.9 fb collected by the CMS experiment in 2016. The ratios of the inclusive cross sections as functions of transverse momentum and rapidity , for in the range 0.1 to 1.2 to those using 0.4 are presented in the region 84 1588 GeV and 2.0. The results are compared to calculations at leading and next-to-leading order in the strong coupling constant using different parton shower models. The variation of the ratio of cross sections with is well described by calculations including a parton shower model, but not by a leading-order quantum chromodynamics calculation including nonperturbative effects. The agreement between the data and the theoretical predictions for the ratios of cross sections is significantly improved when next-to-leading order calculations with nonperturbative effects are used
Search for an excited lepton that decays via a contact interaction to a lepton and two jets in proton-proton collisions at 13 TeV
No full textResults are presented from a search for events containing an excited lepton (electron or muon) produced in association with an ordinary lepton of the same flavor and decaying to a lepton and two hadronic jets. Both the production and the decay of the excited leptons are assumed to occur via a contact interaction with a characteristic energy scale Λ. The branching fraction for the decay mode under study increases with the mass of the excited lepton and is the most sensitive channel for very heavy excited leptons. The analysis uses a sample of proton-proton collisions collected by the CMS experiment at the LHC at = 13 TeV, corresponding to an integrated luminosity of 77.4 fb. The four-body invariant mass of the two lepton plus two jet system is used as the primary discriminating variable. No significant excess of events beyond the expectation for standard model processes is observed. Assuming that Λ is equal to the mass of the excited leptons, excited electrons and muons with masses below 5.6 and 5.7 TeV, respectively, are excluded at 95% confidence level. These are the best limits to date.[graphic not available: see fulltext