Motivated by recent observations suggesting that core-collapse supernovae may on average produce ∼0.3 M of dust, we explore a simple dust production scenario that applies to star-forming galaxies in ...the local environment (the Magellanic Clouds and possibly the Milky Way) as well as to high-redshift (submillimeter, QSO, Lyman-break) galaxies. We assume that the net dust destruction (due to supernova reverse shock, shocks in the interstellar medium, or astration) is negligible on a timescale of 1 Gyr, in which case the dust mass can be estimated as 0.004 times the star formation rate (for a Chabrier initial mass function) multiplied by the duration of the star formation episode. The model can account for observed dust masses over four orders of magnitude and across the redshift range 0-8.4, with dust production rates spanning five orders of magnitude. This suggests that star-forming galaxies may be seen as maximally dusty, in the sense that a dominant fraction of the dust-forming elements forged in a supernova eventually will go into the solid phase. In turn, this indicates little destruction of supernova dust or almost complete replenishment, on a short timescale, of any dust that is destroyed.
Coherent excitation of an ensemble of quantum objects underpins quantum many-body phenomena and offers the opportunity to realize a memory that stores quantum information. Thus far, a deterministic ...and coherent interface between a spin qubit and such an ensemble has remained elusive. In this study, we first used an electron to cool the mesoscopic nuclear spin ensemble of a semiconductor quantum dot to the nuclear sideband-resolved regime. We then implemented an all-optical approach to access individual quantized electronic-nuclear spin transitions. Lastly, we performed coherent optical rotations of a single collective nuclear spin excitation-a spin wave. These results constitute the building blocks of a dedicated local memory per quantum-dot spin qubit and promise a solid-state platform for quantum-state engineering of isolated many-body systems.
AbstractObjectiveTo assess the clinical and cost effectiveness of conservative management compared with laparoscopic cholecystectomy for the prevention of symptoms and complications in adults with ...uncomplicated symptomatic gallstone disease.DesignParallel group, pragmatic randomised, superiority trial.Setting20 secondary care centres in the UK.Participants434 adults (>18 years) with uncomplicated symptomatic gallstone disease referred to secondary care, assessed for eligibility between August 2016 and November 2019, and randomly assigned (1:1) to receive conservative management or laparoscopic cholecystectomy.InterventionsConservative management or surgical removal of the gallbladder.Main outcome measuresThe primary patient outcome was quality of life, measured by area under the curve, over 18 months using the short form 36 (SF-36) bodily pain domain, with higher scores (range 0-100) indicating better quality of life. Other outcomes included costs to the NHS, quality adjusted life years (QALYs), and incremental cost effectiveness ratio.ResultsOf 2667 patients assessed for eligibility, 434 were randomised: 217 to the conservative management group and 217 to the laparoscopic cholecystectomy group. By 18 months, 54 (25%) participants in the conservative management arm and 146 (67%) in the cholecystectomy arm had received surgery. The mean SF-36 norm based bodily pain score was 49.4 (standard deviation 11.7) in the conservative management arm and 50.4 (11.6) in the cholecystectomy arm. The SF-36 bodily pain area under the curve up to 18 months did not differ (mean difference 0.0, 95% confidence interval −1.7 to 1.7; P=1.00). Conservative management was less costly (mean difference −£1033, (−$1334; −€1205), 95% credible interval −£1413 to −£632) and QALYs did not differ (mean difference −0.019, 95% credible interval −0.06 to 0.02).ConclusionsIn the short term (≤18 months), laparoscopic surgery is no more effective than conservative management for adults with uncomplicated symptomatic gallstone disease, and as such conservative management should be considered as an alternative to surgery. From an NHS perspective, conservative management may be cost effective for uncomplicated symptomatic gallstone disease. As costs, complications, and benefits will continue to be incurred in both groups beyond 18 months, future research should focus on longer term follow-up to establish effectiveness and lifetime cost effectiveness and to identify the cohort of patients who should be routinely offered surgery.Trial registrationISRCTN registry ISRCTN55215960.
Non-invasive electrical brain stimulation is a promising add-on approach for neurorehabiliation of visual field loss and visual neglect. Transorbital alternating current stimulation (rtACS) has been ...used in clinical studies to improve visual functions in patients suffering vision loss after optic nerve damage. However, in hemianopic visual field loss the effects of rtACS are less distinct than after optic nerve damage. Combining visual field training with current stimulation may enhance training effects which has been already shown for anodal transcranial direct current stimulation (tDCS) of the occipital cortex in hemianopic visual field loss after strokes. Recent observations also indicate that rebalancing the activity between the two hemispheres as a functional mechanism accompanying recovery may be induced by lateralized respectively dual-mode tDCS application.
The interaction between a confined electron and the nuclei of an optically active quantum dot provides a uniquely rich manifestation of the central spin problem. Coherent qubit control combines with ...an ultrafast spin-photon interface to make these confined spins attractive candidates for quantum optical networks. Reaching the full potential of spin coherence has been hindered by the lack of knowledge of the key irreversible environment dynamics. Through all-optical Hahn echo decoupling we now recover the intrinsic coherence time set by the interaction with the inhomogeneously strained nuclear bath. The high-frequency nuclear dynamics are directly imprinted on the electron spin coherence, resulting in a dramatic jump of coherence times from few tens of nanoseconds to the microsecond regime between 2 and 3 T magnetic field and an exponential decay of coherence at high fields. These results reveal spin coherence can be improved by applying large magnetic fields and reducing strain inhomogeneity.
Stress is ubiquitous in modern life and exerts profound effects on cognitive and emotional functions. Thus, whereas acute stress enhances memory, longer episodes exert negative effects through as yet ...unresolved mechanisms. We report a novel, hippocampus-intrinsic mechanism for the selective memory defects that are provoked by stress. CRH (corticotropin-releasing hormone), a peptide released from hippocampal neurons during stress, depressed synaptic transmission, blocked activity-induced polymerization of spine actin and impaired synaptic plasticity in adult hippocampal slices. Live, multiphoton imaging demonstrated a selective vulnerability of thin dendritic spines to this stress hormone, resulting in depletion of small, potentiation-ready excitatory synapses. The underlying molecular mechanisms required activation and signaling of the actin-regulating small GTPase, RhoA. These results implicate the selective loss of dendritic spine sub-populations as a novel structural and functional foundation for the clinically important effects of stress on cognitive and emotional processes.
Abstract
Radiative transfer models of two transitional type Ia supernovae (SNe Ia) have been produced using the abundance stratification technique. These two objects – designated SN 2007on and SN ...2011iv – both exploded in the same galaxy, NGC 1404, which allows for a direct comparison. SN 2007on synthesized 0.25 $\rm M_{{\odot}}$ of 56Ni and was less luminous than SN 2011iv, which produced 0.31 $\rm M_{{\odot}}$ of 56Ni. SN 2007on had a lower central density (ρc) and higher explosion energy (Ekin ∼1.3 ± 0.3 × 1051erg) than SN 2011iv, and it produced less nuclear statistical equilibrium (NSE) elements (0.06 $\rm M_{{\odot}}$). Whereas, SN 2011iv had a larger ρc, which increased the electron capture rate in the lowest velocity regions, and produced 0.35 $\rm M_{{\odot}}$ of stable NSE elements. SN 2011iv had an explosion energy of ∼Ekin ∼0.9 ± 0.2 × 1051erg. Both objects had an ejecta mass consistent with the Chandrasekhar mass (Ch-mass), and their observational properties are well described by predictions from delayed-detonation explosion models. Within this framework, comparison to the sub-luminous SN 1986G indicates SN 2011iv and SN 1986G have different transition densities (ρtr) but similar ρc. Whereas SN 1986G and SN 2007on had a similar ρtr but different ρc. Finally, we examine the colour–stretch parameter sBV versus Lmax relation and determine that the bulk of SNe Ia (including the sub-luminous ones) are consistent with Ch-mass delayed-detonation explosions, where the main parameter driving the diversity is ρtr. We also find ρc to be driving the second-order scatter observed at the faint end of the luminosity–width relationship.
Abstract
We present 75 near-infrared (NIR; 0.8−2.5
μ
m) spectra of 34 stripped-envelope core-collapse supernovae (SESNe) obtained by the Carnegie Supernova Project-II (CSP-II), encompassing optical ...spectroscopic Types IIb, Ib, Ic, and Ic-BL. The spectra range in phase from pre-maximum to 80 days past maximum. This unique data set constitutes the largest NIR spectroscopic sample of SESNe to date. NIR spectroscopy provides observables with additional information that is not available in the optical. Specifically, the NIR contains the strong lines of He
i
and allows a more detailed look at whether Type Ic supernovae are completely stripped of their outer He layer. The NIR spectra of SESNe have broad similarities, but closer examination through statistical means reveals a strong dichotomy between NIR “He-rich” and “He-poor” SNe. These NIR subgroups correspond almost perfectly to the optical IIb/Ib and Ic/Ic-BL types, respectively. The largest difference between the two groups is observed in the 2
μ
m region, near the He
i
λ
2.0581
μ
m line. The division between the two groups is
not
an arbitrary one along a continuous sequence. Early spectra of He-rich SESNe show much stronger He
i
λ
2.0581
μ
m absorption compared to the He-poor group, but with a wide range of profile shapes. The same line also provides evidence for trace amounts of He in half of our SNe in the He-poor group.
Abstract
The Type Ia supernova (SN Ia) LSQ14fmg exhibits exaggerated properties that may help to reveal the origin of the “super-Chandrasekhar” (or 03fg-like) group. The optical spectrum is typical ...of a 03fg-like SN Ia, but the light curves are unlike those of any SNe Ia observed. The light curves of LSQ14fmg rise extremely slowly. At −23 rest-frame days relative to
B
-band maximum, LSQ14fmg is already brighter than
mag before host extinction correction. The observed color curves show a flat evolution from the earliest observation to approximately 1 week after maximum. The near-infrared light curves peak brighter than −20.5 mag in the
J
and
H
bands, far more luminous than any 03fg-like SNe Ia with near-infrared observations. At 1 month past maximum, the optical light curves decline rapidly. The early, slow rise and flat color evolution are interpreted to result from an additional excess flux from a power source other than the radioactive decay of the synthesized
56
Ni. The excess flux matches the interaction with a typical superwind of an asymptotic giant branch (AGB) star in density structure, mass-loss rate, and duration. The rapid decline starting at around 1 month past
B
-band maximum may be an indication of rapid cooling by active carbon monoxide (CO) formation, which requires a low-temperature and high-density environment. These peculiarities point to an AGB progenitor near the end of its evolution and the core degenerate scenario as the likely explosion mechanism for LSQ14fmg.
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