Current cosmological analyses which use Type Ia supernova (SN Ia) observations combine SN samples to expand the redshift range beyond that of a single sample and increase the overall sample size. The inhomogeneous photometric calibration between different SN samples is one of the largest systematic uncertainties of the cosmological parameter estimation. To place these different samples on a single system, analyses currently use observations of a small sample of very bright flux standards on the HST system. We propose a complementary method, called 'Supercal', in which we use measurements of secondary standards in each system, compare these to measurements of the same stars in the Pan-STARRS1 (PS1) system, and determine offsets for each system relative to PS1, placing all SN observations on a single, consistent photometric system. PS1 has observed 3π of the sky and has a relative calibration of better than 5 mmag (for ∼ 15 < griz < 21 mag), making it an ideal reference system. We use this process to recalibrate optical observations taken by the following SN samples: PS1, SNLS, SDSS, CSP, and CfA1-4. We measure discrepancies on average of 10 mmag, but up to 35 mmag, in various optical passbands. We find that correcting for these differences changes recovered values for the dark energy equation-of-state parameter, w, by on average 2.6%. This change is roughly half the size of current statistical constraints on w. The size of this effect strongly depends on the error in the B − V calibration of the low-z surveys. The Supercal method will allow future analyses to tie past samples to the best calibrated sample.

A plateau phase in the X-ray afterglow is observed in a significant fraction of gamma-ray bursts (GRBs). Previously, it has been found that there exists a correlation among three key parameters concerning the plateau phase, i.e., the end time of the plateau phase in the GRB rest frame (T a ), the corresponding X-ray luminosity at the end time (L X ) and the isotropic energy of the prompt GRB (E γ,iso ). In this study, we systematically search through all the Swift GRBs with a plateau phase that occurred between 2005 May and 2018 August. We collect 174 GRBs, with redshifts available for all of them. For the whole sample, the correlation between L X , T a and E γ,iso is confirmed, with the best fit relation being L X ∝ T −0.92 a E 0.83 γ,iso . Such an updated three-parameter correlation still supports that the central leftover after GRBs is probably a millisecond magnetar. It is interesting to note that short GRBs with duration less than 2 s in our sample also follow the same correlation, which hints that the merger production of two neutron stars could be a high mass magnetar, but not necessarily a black hole. Moreover, GRBs having an "internal" plateau (i.e., with a following decay index being generally smaller than -3) also obey this correlation. It further strengthens the idea that the internal plateau is due to the delayed collapse of a high mass neutron star into a black hole. The updated three-parameter correlation indicates that GRBs with a plateau phase may act as a standard candle for cosmology study.

Neutrophils are implicated in numerous inflammatory diseases, and especially in acute ischemic stroke (AIS). The unchecked migration of neutrophils into cerebral ischemic regions, and their subsequent release of reactive oxygen species, are considered the primary causes of reperfusion injury following AIS. Reducing the infiltration of inflammatory neutrophils may therefore be a useful therapy for AIS. Here, inspired by the specific cell–cell recognition that occurs between platelets and inflammatory neutrophils, we describe platelet-mimetic nanoparticles (PTNPs) that can be used to directly recognize, intervene, and monitor inflammatory neutrophils in the AIS treatment and therapeutic evaluation. We demonstrate that PTNPs, coloaded with piceatannol, a selective spleen tyrosine kinase inhibitor, and superparamagnetic iron oxide (SPIO), a T2 contrast agent, can successfully recognize adherent neutrophils via platelet membrane coating. The loaded piceatannol could then be delivered to adherent neutrophils and detach them into circulation, thus decreasing neutrophil infiltration and reducing infarct size. Moreover, when coupled with magnetic resonance imaging, internalized SPIO could be used to monitor the inflammatory neutrophils, associated with therapeutic effects, in real time. This approach is an innovative method for both the treatment and therapeutic evaluation of AIS, and provides new insights into how to treat and monitor neutrophil-associated diseases.

The nucleation and growth of Li metal deposits and whiskers were studied using a novel in-situ scanning electron microscopy (SEM) platform. The experiments utilized a thin carbon film as a substrate for Li deposition. Rather than depositing primarily at the carbon-electrolyte interface, much of the Li deposits at the carbon-vacuum interface. This allows the effects of concentration polarization and electric field localization to be eliminated as primary mechanisms for whisker and dendrite growth. Instead, measurements performed as a function of vacuum pressure reveal that whisker growth is sensitive to vacuum level. It is proposed that whisker growth results from diffusional relaxation of compressive stress imposed by a thin surface oxide. Similar mechanisms may be extended to Li dendrite growth in solution where solid electrolyte interphase introduces a compressive stress.

No abstract

No abstract

Creating oxide interfaces with precise chemical specificity at the atomic layer level is desired for the engineering of quantum phases and electronic applications, but highly challenging, owing partially to the lack of in situ tools to monitor the chemical composition and completeness of the surface layer during growth. Here we report the in situ observation of atomic layer-by-layer inner potential variations by analysing the Kikuchi lines during epitaxial growth of strontium titanate, providing a powerful real-time technique to monitor and control the chemical composition during growth. A model combining the effects of mean inner potential and step edge density (roughness) reveals the underlying mechanism of the complex and previously not well-understood reflection high-energy electron diffraction oscillations observed in the shuttered growth of oxide films. General rules are proposed to guide the synthesis of atomically and chemically sharp oxide interfaces, opening up vast opportunities for the exploration of intriguing quantum phenomena at oxide interfaces.

Surface reactions occurring on LiMnO, LiCoO, LiNiO, Li[NiMnCo]O, and LiFePO during charging and overcharging are studied by in situ and ex situ Auger electron spectroscopy. Carbon surface stability at the cathode solid-electrolyte interphase (SEI), associated with carbonate formation, decomposition, and CO/CO evolution, on different electrodes during cycling correlates with their cycle life. To understand how associated CO and CO evolution affects cycle stability, LiMnO is cycled in flowing gas. Flowing Ar enhances cycle life by a factor of 2, while flowing Ar with 1% CO reduces cycle life by a factor of 2. CO is proposed to degrade cycle life by trapping Li and metal ions as carbonate in the anode SEI.