AFM measurements of the force acting between silica surfaces in the presence of varied alkali chloride salts and pH's elucidate the origin of the Hofmeister adsorption series and its reversal. At low pH, electrostatics is shown to be insignificant. The preferential adsorption of Cs(+) to the silica surface is traced to the weak hydration of neutral silanols and the resulting hydrophobic expulsion of weakly hydrated ions from bulk solution to the interface. The same interactions keep the strongly hydrated Na(+) and Li(+) in solution. As pH is increased, a tightly bound hydration layer forms on deprotonating silanols. Cs(+) is correspondingly expelled from the surface, and adsorption of small ions is encouraged. The deduced role of surface hydration is corroborated by hydration repulsion observed at high pH, surface overcharging at low pH, and data in other oxides.

We present a critical analysis of the observational constraints on, and of the theoretical modelling of, aspects of cosmic ray (CR) generation and propagation in the Galaxy, which are relevant for the interpretation of recent positron and antiproton measurements. We give simple, analytic, model-independent expressions for the secondaryp flux, and an upper limit for the secondary e + flux, obtained by neglecting e + radiative losses, e + /(e + + e − ) < 0.2 ± 0.1 up to ∼300 GeV. These expressions are completely determined by the rigidity-dependent grammage, which is measured from stable CR secondaries up to ∼150 GeV nucleon −1 , and by nuclear cross-sections measured in the laboratory.p and e + measurements, available up to ∼100 GeV, are consistent with these estimates, implying that there is no need for new, non-secondary,p or e + sources. The radiative loss suppression factor f s,e + of the e + flux depends on the e + propagation in the Galaxy, which is not understood theoretically. A rough, model-independent estimate of f s,e + ∼ 1/3 can be obtained at a single energy, ε ∼ 20 GeV, from unstable secondary decay and is found to be consistent with e + measurements, including the positron fraction measured by Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA). We show that specific detailed models, that agree with compositional CR data, agree with our simple expressions for the e + andp flux, and that the claims that the positron fraction measured by PAMELA requires new primary e + sources are based on assumptions, that are not supported by observations. If PAMELA results are correct, they suggest that f s,e + (ε) is slightly increasing with energy, which provides an interesting constraint on CR propagation models. We argue that measurements of the e + top ratio are more useful for challenging secondary production models than the e + /(e + + e − ) fraction.

Supernova light curves are dominated at early time, hours to days, by photons escaping from the expanding shock heated envelope. We provide a simple analytic description of the time dependent luminosity, L, and color temperature, Tcol, for explosions of red supergiants (with convective polytropic envelopes), valid up to H recombination (T ≈ 0.7 eV). The analytic description interpolates between existing expressions valid at different (planar then spherical) stages of the expansion, and is calibrated against numerical hydrodynamic diffusion calculations for a wide range of progenitor parameters (mass, radius, core/envelope mass and radius ratios, metalicity), and explosion energies. The numerically derived L and Tcol are described by the analytic expressions with $10{{\%}}$ and $5{{\%}}$ accuracy respectively. Tcol is inferred from the hydrodynamic profiles using frequency independent opacity, based on tables we constructed for this purpose (and will be made publicly available) including bound-bound and bound-free contributions. In an accompanying paper (Paper II) we show, using a large set of multi-group photon diffusion calculations, that the spectral energy distribution is well described by a Planck spectrum with T = Tcol, except at UV frequencies, where the flux can be significantly suppressed due to strong line absorption. We defer the full discussion of the multi-group results to paper II, but provide here for completeness an analytic description also of the UV suppression. Our analytic results are a useful tool for inferring progenitor properties, explosion velocity, and also relative extinction based on early multi-band shock cooling observations of supernovae.

High cadence transient surveys are able to capture supernovae closer to their first light than before. Applying analytical models to such early emission, we can constrain the progenitor stars properties. In this paper, we present observations of SN 2018 fif (ZTF18abokyfk). The supernova was discovered close to first light and monitored by the Zwicky Transient Facility (ZTF) and the Neil Gehrels Swift Observatory. Early spectroscopic observations suggest that the progenitor of SN 2018 fif was surrounded by relatively small amounts of circumstellar material (CSM) compared to all previous cases. This particularity, coupled with the high cadence multiple-band coverage, makes it a good candidate to investigate using shock-cooling models. We employ the SOPRANOS code, an implementation of the model by Sapir & Waxman (2017). Compared with previous implementations, SOPRANOS has the advantage of including a careful account of the limited temporal validity domain of the shockcooling model. We find that the progenitor of SN 2018 fif was a large red supergiant, with a radius of R = 1174 +208 −81 R and an ejected mass of M ej = 5.6 +9.1 −1.0 M. Our model also gives information on the explosion epoch, the progenitor inner structure, the shock velocity and the extinction. The large radius differs from previously modeled objects, and the difference could be either intrinsic or due to the relatively small amount of CSM around SN 2018 fif, perhaps making it a "cleaner" candidate for applying shock-cooling analytical models.

High cadence transient surveys are able to capture supernovae closer to their first light than before. Applying analytical models to such early emission, we can constrain the progenitor stars properties. In this paper, we present observations of SN 2018 fif (ZTF18abokyfk). The supernova was discovered close to first light and monitored by the Zwicky Transient Facility (ZTF) and the Neil Gehrels Swift Observatory. Early spectroscopic observations suggest that the progenitor of SN 2018 fif was surrounded by relatively small amounts of circumstellar material (CSM) compared to all previous cases. This particularity, coupled with the high cadence multiple-band coverage, makes it a good candidate to investigate using shock-cooling models. We employ the SOPRANOS code, an implementation of the model by Sapir & Waxman (2017). Compared with previous implementations, SOPRANOS has the advantage of including a careful account of the limited temporal validity domain of the shockcooling model. We find that the progenitor of SN 2018 fif was a large red supergiant, with a radius of R = 1174 +208 −81 R and an ejected mass of M ej = 5.6 +9.1 −1.0 M . Our model also gives information on the explosion epoch, the progenitor inner structure, the shock velocity and the extinction. The large radius differs from previously modeled objects, and the difference could be either intrinsic or due to the relatively small amount of CSM around SN 2018 fif, perhaps making it a "cleaner" candidate for applying shock-cooling analytical models.