Quantum light sources in solid-state systems are of major interest as a basic ingredient for integrated quantum photonic technologies. The ability to tailor quantum emitters via site-selective defect ...engineering is essential for realizing scalable architectures. However, a major difficulty is that defects need to be controllably positioned within the material. Here, we overcome this challenge by controllably irradiating monolayer MoS
using a sub-nm focused helium ion beam to deterministically create defects. Subsequent encapsulation of the ion exposed MoS
flake with high-quality hBN reveals spectrally narrow emission lines that produce photons in the visible spectral range. Based on ab-initio calculations we interpret these emission lines as stemming from the recombination of highly localized electron-hole complexes at defect states generated by the local helium ion exposure. Our approach to deterministically write optically active defect states in a single transition metal dichalcogenide layer provides a platform for realizing exotic many-body systems, including coupled single-photon sources and interacting exciton lattices that may allow the exploration of Hubbard physics.
Electron transport and photoresponse in the terahertz range in a GaN/AlGaN field-effect transistor with the submicrometer gate (0.25 μm) and two-dimensional electron gas in the channel (the electron ...concentration ns = 5 × 1012 cm−2) were studied at 4.2 K. The charge-carrier mobility in the transistor’s channel μ = 3500 cm2/(V s) was determined from the dependence of the conductance on magnetic field. It is found that the dependence of photovoltage at the radiation frequency f = 574 GHz on the gate voltage (i.e., on the concentration of two-dimensional electrons) features a characteristic maximum, which is related to a resonance response of the subgate plasma in the transistor channel.
ABSTRACT
Multivariate Bayesian linear-threshold models were used to estimate genetic parameters of peri- and postnatal piglet survival and individual birth weight of piglets reared under outdoor ...conditions. Data of 21,835 individual piglet observations were available from a 2-generation crossbreeding experiment selected for direct and maternal genetic effects of postnatal piglet survival on piglet and dam levels, respectively. In the first generation, approximately one-half of the Landrace sires used were selected for large or average breeding values of maternal genetic effects on postnatal piglet survival, whereas in the second generation the Large White sires used were selected for direct genetic effects of the same trait. Estimates of direct and maternal heritability were 0.21 and 0.15, 0.24 and 0.14, and 0.36 and 0.28 for piglet survival at birth and during the nursing period, and individual birth weight, respectively. In particular, direct heritabilities are substantially larger than those from the literature estimated for indoor-reared piglets, suggesting that genetic effects of these traits are substantially greater under outdoor conditions. Direct or maternal genetic correlations between survival traits or with birth weight were small (ranging from 0.06 to 0.17), indicating that peri- and postnatal survival are genetically under rather different control, and survival was only slightly positively influenced by birth weight. There were significant (P < 0.05) negative genetic correlations between direct and maternal genetic effects within each of the analyzed traits ranging from –0.36 to –0.45, which have to be considered when selecting for piglet survival. Adjustment of traits for litter size or inclusion of genetic groups showed insignificant effects on the magnitude of the estimated genetic parameters. The magnitude of genetic parameters suggested that there is substantial potential for genetic improvement of survival traits and birth weight in direct and maternal genetic effects, especially when piglets are kept under outdoor conditions.
In 1986 more than 8 million liters of crude oil spilled into a complex region of mangroves, seagrasses, and coral reefs just east of the Caribbean entrance to the Panama Canal. This was the largest ...recorded spill into coastal habitats in the tropical Americas. Many populations of plants and animals in both oiled and unoiled sites had been studied previously, thereby providing an unprecedented measure of ecological variation before the spill. Documentation of the spread of oil and its biological effects begun immediately. Intertidal mangroves, seagrasses, algae, and associated invertebrates were covered by oil and died soon after. More surprisingly, there was also extensive mortality of shallow subtidal reef corals and infauna of seagrass beds. After 1.5 years only some organisms in areas exposed to the open sea have recovered.
Showing clear estrus symptoms contributes to the reproductive effectiveness of a sow. The aim of the study was to estimate genetic parameters and breeding values for estrus symptoms, a trait which ...included swelling and reddening of the vulva, interest in the boar and strength of the standing reflex. Around 31,000 reproductive sow cycles from three lines were scored on farms, using an ordinal scale (five categories). Variance component estimation was done by applying a threshold model. The estimates for the additive genetic variance, permanent environmental variance, heritability and repeatability are (standard errors in parenthesis) 0.10 (0.02), 0.06 (0.02), 0.09 (0.02) and 0.14 (0.02), respectively. The genetic correlation between estrus symptoms and litter size at birth was very weak (−0.05±0.04). It seems that a selection for the trait estrus symptoms is possible and is not accompanied by a change in the litter size.
This paper presents low detection limit (ppm level) measurements of admixtures dissolved in gasoline liquid samples using Terahertz Time-Domain Spectroscopy (THz-TDS). Contrary to the methods which ...are based on spectroscopic measurements we found that the pulse delay is an adequate parameter to detect water or alcohol admixtures in gasoline. The method is validated for water and isopropanol admixtures in gasoline with a precision of down to 250 ppm in case of water.
We present experimental results of THz detection signal dependence on the magnetic field. THz radiation was detected with AlGaAs/GaAs high electron mobility transistor where 2D plasma excitations are ...responsible for the detection signal appearance. We observe both Shubnikov-de Haas oscillations and cyclotron resonance in the detection signal. Fourier transform analysis of the oscillations allowed us to observe two parts of the 2D electron gas: gated and ungated. This allows us to conclude that 2D electrons in the transistor channel are necessary for detection process and both gated and ungated parts takes part in that process.
Graphene is a quantum spin Hall insulator, with a nontrivial topological gap induced by the spin-orbit coupling. Such splitting is weak (\sim 45 \mu eV) in the absence of external magnetic field. ...However, due to rather long spin-relaxation time, graphene is an attractive candidate for applications in quantum technologies. When it is encapsulated in hexagonal boron nitride, the coupling between graphene and the substrate compensates intrinsic spin-orbit coupling and decreases the nontrivial topological gap, which may lead to phase transition into a trivial band insulator state. In this work, we have measured experimentally the zero-field splittings in monolayer and bilayer graphene by the means of subterahertz photoconductivity-based electron spin resonance technique. The dependance in temperature of such splittings have been also studied in the 2-12K range. We observed a decrease of the spin splittings with increasing temperature. Such behavior might be understood from several physical mechanisms that could induce a temperature dependence of the spin-orbit coupling. These includes the difference in the expansion coefficients between the graphene and the boron nitride substrate or the metal contacts, the electronphonon interactions, and the presence of a magnetic order at low temperature.
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