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When a liquid is cooled to produce a glass its dynamics, dominated by the structural relaxation, become very slow, and at the glass-transition temperature T g its characteristic relaxation time is about 100 s. At slightly elevated temperatures (~1.2 T g ) however, a second process known as the Johari-Goldstein relaxation, β JG , decouples from the structural one and remains much faster than it down to T g . While it is known that the β JG -process is strongly coupled to the structural relaxation, its dedicated role in the glass-transition remains under debate. Here we use an experimental technique that permits us to investigate the spatial and temporal properties of the β JG relaxation, and give evidence that the molecules participating in it are highly mobile and spatially connected in a system-spanning, percolating cluster. This correlation of structural and dynamical properties provides strong experimental support for a picture, drawn from theoretical studies, of an intermittent mosaic structure in the deeply supercooled liquid phase. The Johari-Goldstein relaxation is a precursor of the glass transition in liquids. Caporaletti et al. use time-dependent interferometry data to substantiate its suggested structural appearance as a globally percolating, fluctuating mosaic.

Understanding the glass transition requires getting the picture of the dynamical processes that intervene in it. Glass-forming liquids show a characteristic decoupling of relaxation processes when they are cooled down towards the glassy state. The faster ( β JG ) process is still under scrutiny, and its full explanation necessitates information at the microscopic scale. To this aim, nuclear γ -resonance time-domain interferometry (TDI) has been utilized to investigate 5-methyl-2-hexanol, a hydrogen-bonded liquid with a pronounced β JG process as measured by dielectric spectroscopy. TDI probes in fact the center-of-mass, molecular dynamics at scattering-vectors corresponding to both inter- and intra-molecular distances. Our measurements demonstrate that, in the undercooled liquid phase, the β JG relaxation can be visualized as a spatially-restricted rearrangement of molecules within the cage of their closest neighbours accompanied by larger excursions which reach out at least the inter-molecular scale and are related to cage-breaking events. In-cage rattling and cage-breaking processes therefore coexist in the β JG relaxation.

With the advent of new wide-field, high-cadence optical transient surveys, our understanding of the diversity of core-collapse supernovae has grown tremendously in the last decade. However, the pre-supernova evolution of massive stars, which sets the physical backdrop to these violent events, is theoretically not well understood and difficult to probe observationally. Here we report the discovery of the supernova iPTF 13dqy = SN 2013fs a mere ∼3 h after explosion. Our rapid follow-up observations, which include multiwavelength photometry and extremely early (beginning at ∼6 h post-explosion) spectra, map the distribution of material in the immediate environment (≲10 15  cm) of the exploding star and establish that it was surrounded by circumstellar material (CSM) that was ejected during the final ∼1 yr prior to explosion at a high rate, around 10 −3 solar masses per year. The complete disappearance of flash-ionized emission lines within the first several days requires that the dense CSM be confined to within ≲10 15  cm, consistent with radio non-detections at 70–100 days. The observations indicate that iPTF 13dqy was a regular type II supernova; thus, the finding that the probable red supergiant progenitor of this common explosion ejected material at a highly elevated rate just prior to its demise suggests that pre-supernova instabilities may be common among exploding massive stars. Type II supernova explosions are common, but our understanding of such events is not complete. Such an event was observed just three hours after the explosion started, providing important information about the early stages.

Shifting the focus of Type Ia supernova (SN Ia) cosmology to the near infrared (NIR) is a promising way to significantly reduce the systematic errors, as the strategy minimizes our reliance on the empirical width-luminosity relation and uncertain dust laws. Observations in the NIR are also crucial for our understanding of the origins and evolution of these events, further improving their cosmological utility. Any future experiments in the rest-frame NIR will require knowledge of the SN Ia NIR spectroscopic diversity, which is currently based on a small sample of observed spectra. Along with the accompanying paper, Phillips et al., we introduce the Carnegie Supernova Project-II (CSP-II), to follow-up nearby SNe Ia in both the optical and the NIR. In particular, this paper focuses on the CSP-II NIR spectroscopy program, describing the survey strategy, instrumental setups, data reduction, sample characteristics, and future analyses on the data set. In collaboration with the Harvard-Smithsonian Center for Astrophysics (CfA) Supernova Group, we obtained 661 NIR spectra of 157 SNe Ia. Within this sample, 451 NIRspectra of 90 SNe Ia have corresponding CSP-II follow-up light curves. Such a sample will allow detailed studies of the NIR spectroscopic properties of SNe Ia, providing a different perspective on the properties of the unburned material; the radioactive and stable nickel produced; progenitor magnetic fields; and searches for possible signatures of companion stars.

ObjectiveThe impact of a screening programme on colorectal cancer (CRC) incidence in its target population depends on several variables, including coverage with invitations, participation rate, positivity rate of the screening test, compliance with an invitation to second-level assessment and endoscopists’ sensitivity. We propose a synthetic indicator that may account for all the variables influencing the potential impact of a screening programme on CRC incidence.DesignWe defined the ‘rate of advanced adenoma on the target population’ (AA-TAP) as the rate of patients who received a diagnosis of advanced adenoma within a screening programme, divided by the programme target population. We computed the AA-TAP for the CRC Italian screening programmes (biennial faecal immunochemical test, target population 50–69 year olds) using the data of the Italian National Survey from 2003 to 2016, overall and by region, and assessed the association between AA-TAP and CRC incidence fitting a linear regression between the trend of regional CRC incidence rates in 50–74 year old subjects and the cumulative AA-TAP.ResultsIn 2016, the AA-TAP at a national level was 105×100 000, whereas significant differences were observed between the northern and central regions (respectively 126 and 149×100 000) and the South and Islands (36×100 000). The cumulative AA-TAP from 2004 to 2012 was significantly correlated with the difference between CRC incidence rates in 2013–2014 and those in 2003–2004 (p=0.009).ConclusionThe AA-TAP summarises into a single indicator the potential impact of a screening programme in reducing CRC incidence rates.

A supernova with a past Theory suggests that stars with initial masses greater than 25–30 times that of the Sun end their stellar lives as Wolf–Rayet stars, becoming hydrogen-deficient by rapidly losing mass through strong stellar winds. Any subsequent supernova explosion should produce ejecta of low kinetic energy and faint optical luminosity, with a small mass fraction of radioactive nickel. Until now no core-collapse supernovae fitting this description have been detected. But SN 2008ha, discovered on 7 November 2008, appears to fit the bill. A detailed photometric and spectroscopic study shows SN 2008ha to be the faintest and lowest-luminosity hydrogen-deficient supernova known. This discovery raises the possibility that other similar events have been observed previously — SN 2002cx is one candidate — but were classified as 'peculiar thermonuclear supernovae'. Theory suggests that stars with initial masses greater than 25–30 solar masses end up as Wolf-Rayet stars, which are deficient in hydrogen in their outer layers; subsequent supernova explosions should produce ejecta of low kinetic energy, a faint optical luminosity and a small mass fraction of radioactive nickel, but no weak, hydrogen-deficient, core-collapse supernovae have hitherto been see. Now, SN 2008ha is reported to be a faint hydrogen-poor supernova. The final fate of massive stars depends on many factors. Theory suggests that some with initial masses greater than 25 to 30 solar masses end up as Wolf–Rayet stars, which are deficient in hydrogen in their outer layers because of mass loss through strong stellar winds. The most massive of these stars have cores which may form a black hole and theory predicts that the resulting explosion of some of them produces ejecta of low kinetic energy, a faint optical luminosity and a small mass fraction of radioactive nickel 1 , 2 , 3 . An alternative origin for low-energy supernovae is the collapse of the oxygen–neon core of a star of 7–9 solar masses 4 , 5 . No weak, hydrogen-deficient, core-collapse supernovae have hitherto been seen. Here we report that SN 2008ha is a faint hydrogen-poor supernova. We propose that other similar events have been observed but have been misclassified as peculiar thermonuclear supernovae (sometimes labelled SN 2002cx-like events 6 ). This discovery could link these faint supernovae to some long-duration γ-ray bursts, because extremely faint, hydrogen-stripped core-collapse supernovae have been proposed to produce such long γ-ray bursts, the afterglows of which do not show evidence of associated supernovae 7 , 8 , 9 .

Recent all-sky surveys have led to the discovery of new types of transients. These include stars disrupted by the central supermassive black hole, and supernovae that are 10–100 times more energetic than typical ones. However, the nature of even more energetic transients that apparently occur in the innermost regions of their host galaxies is hotly debated 1 – 3 . Here we report the discovery of the most energetic of these to date: PS1-10adi, with a total radiated energy of ~2.3 × 10 52  erg. The slow evolution of its light curve and persistently narrow spectral lines over ∼ 3 yr are inconsistent with known types of recurring black hole variability. The observed properties imply powering by shock interaction between expanding material and large quantities of surrounding dense matter. Plausible sources of this expanding material are a star that has been tidally disrupted by the central black hole, or a supernova. Both could satisfy the energy budget. For the former, we would be forced to invoke a new and hitherto unseen variant of a tidally disrupted star, while a supernova origin relies principally on environmental effects resulting from its nuclear location. Remarkably, we also discover that PS1-10adi is not an isolated case. We therefore surmise that this new population of transients has previously been overlooked due to incorrect association with underlying central black hole activity. The discovery of the most energetic transient event to date is reported. Its spectroscopic properties and temporal evolution imply it is powered by shock interaction between expanding material and large quantities of surrounding dense matter.

Dry run for a supernova When a bright optical transient was discovered in galaxy UGC 4904 in October 2004 the signs were that it was big enough and bright enough to be a supernova. Further work suggested that it was not quite on that scale; but almost exactly two years after its discovery it seems to have exploded in a big way. Supernova SN 2006jc is in exactly the same place in the sky as the earlier optical transient. This is the first time that such a double outburst has been observed. One possibility is that the initial transient was an outburst from a Wolf-Rayet star, a very hot massive star losing mass rapidly. Or the system might be a binary containing a luminous blue variable star that erupted in 2004, followed two years later by a companion Wolf-Rayet star exploding as SN 2006jc. The peculiar Type Ib supernova SN 2006jc is spatially coincident with a bright optical transient that occurred in 2004. An outburst (similar to that of a luminous blue variable star) of a Wolf–Rayet star could be invoked for the transient, but this would be the first observational evidence of such a phenomenon. Alternatively a massive binary system composed of an LBV which erupted in 2004, and a Wolf–Rayet star exploding as SN 2006jc, could explain the observations. The death of massive stars produces a variety of supernovae, which are linked to the structure of the exploding stars 1 , 2 . The detection of several precursor stars of type II supernovae has been reported (see, for example, ref. 3 ), but we do not yet have direct information on the progenitors of the hydrogen-deficient type Ib and Ic supernovae. Here we report that the peculiar type Ib supernova SN 2006jc is spatially coincident with a bright optical transient 4 that occurred in 2004. Spectroscopic and photometric monitoring of the supernova leads us to suggest that the progenitor was a carbon-oxygen Wolf–Rayet star embedded within a helium-rich circumstellar medium. There are different possible explanations for this pre-explosion transient. It appears similar to the giant outbursts of luminous blue variable stars (LBVs) of 60–100 solar masses 5 , but the progenitor of SN 2006jc was helium- and hydrogen-deficient (unlike LBVs). An LBV-like outburst of a Wolf–Rayet star could be invoked, but this would be the first observational evidence of such a phenomenon. Alternatively, a massive binary system composed of an LBV that erupted in 2004, and a Wolf–Rayet star exploding as SN 2006jc, could explain the observations.

This paper is the data release of a new sample of 140 type Ia supernovae (SNe Ia) from the LaSilla-QUEST/Las Cumbres Observatory (LCO) collaboration. The discovery of the supernovae came from the LaSilla-QUEST variability survey, the ASASSN survey, as well as smaller low redshift supernova surveys. All of the supernovae in this sample were spectroscopically identified as SNe Ia using spectra from the PESSTO survey using the 3.5 m NTT telescope at LaSilla and spectra from the LCO 2 m Faulkes telescopes. The light-curves were obtained from a rapid cadence photometric follow up of the supernovae with the 9 LCO 1 m telescopes located at various observatories around the globe. Reference images of the host galaxies were taken approximately a year after the supernova have faded to allow precise galaxy background subtraction from the supernova magnitudes. The supernovae in this sample were discovered over a seven year period from 2012 October to 2019 June, and the last galaxy reference images were taken before 2020 June.

Red supergiants have been confirmed as the progenitor stars of the majority of hydrogen-rich type II supernovae 1 . However, while such stars are observed with masses >25  M ⊙ (ref. 2 ), detections of >18  M ⊙ progenitors remain elusive 1 . Red supergiants are also expected to form at all metallicities, but discoveries of explosions from low-metallicity progenitors are scarce. Here, we report observations of the type II supernova, SN 2015bs, for which we infer a progenitor metallicity of ≤0.1  Z ⊙ from comparison to photospheric-phase spectral models 3 , and a zero-age main-sequence mass of 17–25  M ⊙ through comparison to nebular-phase spectral models 4 , 5 . SN 2015bs displays a normal ‘plateau’ light-curve morphology, and typical spectral properties, implying a red supergiant progenitor. This is the first example of such a high-mass progenitor for a ‘normal’ type II supernova, suggesting a link between high-mass red supergiant explosions and low-metallicity progenitors. Supernova SN 2015bs is a hydrogen-rich type II supernova that appears to have been generated by a high-mass (>18  M ⊙ ) and low-metallicity (<0.1  Z ⊙ ) red supergiant progenitor.