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Cobalt-Catalyzed C(sp2)-C(sp3) Suzuki-Miyaura Cross-Coupling Enabled by Well-Defined Precatalysts with L,X-Type Ligands
No full textCobalt(II) halides in combination with phenoxy-imine (FI) ligands generated efficient precatalysts in situ for the C(sp2)-C(sp3) Suzuki-Miyaura cross coupling between alkyl bromides and neopentylglycol (hetero)arylboronic esters. The protocol enabled efficient C-C bond formation with a host of nucleophiles and electrophiles (36 examples, 34-95%) with precatalyst loadings of 5 mol%. Studies with alkyl halide electrophiles that function as radical clocks support the intermediacy of alkyl radicals during the course of the catalytic reaction. The improved performance of the FI-cobalt catalyst was correlated with decreased lifetimes of cage-escaped radicals as compared to diamine-type ligands. Studies of the phenoxy(imine)-cobalt coordination chemistry validate the L,X interaction leading to the discovery of an optimal, well defined, air-stable mono-FI cobalt(II) precatalyst structure
Ferromagnetic Double Perovskite Semiconductors with Tunable Properties
No full textThe authors successfully dope the magnetically silent double perovskite semiconductor Sr2GaSbO6 to induce ferromagnetism and tune its bandgap, with Ga3+ partially substituted by the magnetic trivalent cation Mn3+, in a rigid cation ordering with Sb5+. The new ferromagnetic semiconducting Sr2Ga1−xMnxSbO6 double perovskite, which crystallizes in tetragonal symmetry (space group I4/m) and has tunable ferromagnetic ordering temperature and bandgap, suggests that magnetic ion doping of double perovskites is a productive avenue toward obtaining materials for application in next-generation oxide-based spintronic devices
Hydrostatic pressure effect on Co-based honeycomb magnet BaCo2(AsO4)2
No full textThe honeycomb antiferromagnet BaCo2(AsO4)2, in which small in-plane magnetic fields (1≈0.26 T and 2≈0.52 T at =1.8 K<≈5.4 K) induce two magnetic phase transitions, has attracted attention as a possible candidate material for the realization of Kitaev physics based on the 3 element Co2+. Here, we report on the change in the transition temperature and the critical fields 1 and 2 of BaCo2(AsO4)2 with hydrostatic pressure up to ∼20 kbar, as determined from magnetization and specific heat measurements. Within this pressure range, a marginal increase in the magnetic ordering temperature is observed. At the same time, the critical fields are changed significantly (up to ∼25–35%). Specifically, we find that 1 is increased with hydrostatic pressure, i.e., the antiferromagnetic state is stabilized, whereas 2, which was previously associated with a transition into a proposed Kitaev spin-liquid state, decreases with increasing pressure. We discuss to what extent these results are compatible with suggested models with sizable third-nearest-neighbor exchange. Overall, the results put constraints on the magnetic models that are used to describe the low-temperature magnetic properties of BaCo2(AsO4)2
Magnetic cations doped into a double perovskite semiconductor
No full textWe report two solid solutions based on the magnetic ion doping of the double perovskite oxide Sr2GaSbO6: Sr2Ga1−xCrxSbO6 (0.1 ≤ x ≤ 0.4) and Sr2Ga1−xFexSbO6 (0.1 ≤ x ≤ 0.4). All compositions crystallize in the same space group (I4/m) as their undoped parent phase Sr2GaSbO6, with the trivalent magnetic cations Cr3+ or Fe3+ partially substituting for non-magnetic Ga3+ in one of the B-cation sites. The Cr- and Fe-doped phases display dominant antiferromagnetic coupling among the dopant magnetic moments, and exhibit decreasing band gaps with increasing substitution level
One-dimensional Luttinger liquids in a two-dimensional moiré lattice
No full textThe Luttinger liquid (LL) model of one-dimensional (1D) electronic systems provides a powerful tool for understanding strongly correlated physics, including phenomena such as spin–charge separation1. Substantial theoretical efforts have attempted to extend the LL phenomenology to two dimensions, especially in models of closely packed arrays of 1D quantum wires2,3,4,5,6,7,8,9,10,11,12,13, each being described as a LL. Such coupled-wire models have been successfully used to construct two-dimensional (2D) anisotropic non-Fermi liquids2,3,4,5,6, quantum Hall states7,8,9, topological phases10,11 and quantum spin liquids12,13. However, an experimental demonstration of high-quality arrays of 1D LLs suitable for realizing these models remains absent. Here we report the experimental realization of 2D arrays of 1D LLs with crystalline quality in a moiré superlattice made of twisted bilayer tungsten ditelluride (tWTe2). Originating from the anisotropic lattice of the monolayer, the moiré pattern of tWTe2 hosts identical, parallel 1D electronic channels, separated by a fixed nanoscale distance, which is tuneable by the interlayer twist angle. At a twist angle of approximately 5 degrees, we find that hole-doped tWTe2 exhibits exceptionally large transport anisotropy with a resistance ratio of around 1,000 between two orthogonal in-plane directions. The across-wire conductance exhibits power-law scaling behaviours, consistent with the formation of a 2D anisotropic phase that resembles an array of LLs. Our results open the door for realizing a variety of correlated and topological quantum phases based on coupled-wire models and LL physics
Superclustering with the Atacama Cosmology Telescope and Dark Energy Survey. I. Evidence for Thermal Energy Anisotropy Using Oriented Stacking
No full textThe cosmic web contains filamentary structure on a wide range of scales. On the largest scales, superclustering
aligns multiple galaxy clusters along intercluster bridges, visible through their thermal Sunyaev–Zel’dovich signal
in the cosmic microwave background. We demonstrate a new, flexible method to analyze the hot gas signal from
multiscale extended structures. We use a Compton y-map from the Atacama Cosmology Telescope (ACT) stacked
on redMaPPer cluster positions from the optical Dark Energy Survey (DES). Cutout images from the y-map are
oriented with large-scale structure information from DES galaxy data such that the superclustering signal is aligned
before being overlaid. We find evidence of an extended quadrupole moment of the stacked y signal at the 3.5σ
level, demonstrating that the large-scale thermal energy surrounding galaxy clusters is anisotropically distributed.
We compare our ACT × DES results with the Buzzard simulations, finding broad agreement. Using simulations,
we highlight the promise of this novel technique for constraining the evolution of anisotropic, non-Gaussian
structure using future combinations of microwave and optical survey
Cross-correlation of Dark Energy Survey Year 3 lensing data with ACT and Planck thermal Sunyaev-Zel'dovich effect observations. I. Measurements, systematics tests, and feedback model constraints
No full textWe present a tomographic measurement of the cross-correlation between thermal Sunyaev-Zeldovich (tSZ) maps from Planck and the Atacama Cosmology Telescope (ACT) and weak galaxy lensing shears measured during the first three years of observations of the Dark Energy Survey (DES Y3). This correlation is sensitive to the thermal energy in baryons over a wide redshift range, and is therefore a powerful probe of astrophysical feed-back. We detect the correlation at a statistical significance of 21σ, the highest significance to date. We examine the tSZ maps for potential contaminants, including cosmic infrared background (CIB) and radio sources, finding that CIB has a substantial impact on our measurements and must be taken into account in our analysis. We use the cross-correlation measurements to test different feedback models. In particular, we model the tSZ using several different pressure profile models calibrated against hydrodynamical simulations. Our analysis marginalises over redshift uncertainties, shear calibration biases, and intrinsic alignment effects. We also marginalise over Ωm and σ8 using Planck or DES priors. We find that the data prefers the model with a low amplitude of the pressure profile at small scales, compatible with a scenario with strong AGN feedback and ejection of gas from the inner part of the halos. When using a more flexible model for the shear profile, constraints are weaker, and the data cannot discriminate between different baryonic prescriptions
Diana and Actaeon: The Myth as Synthesis
No full textThe myth of Actaeon offers a structure in which artists can express complex combinations of ideas. Ovid's Actaeon is a victim of the gods but also a visionary and a prototype of the self-conscious man, while other ancient sources see him as a dangerous lover. Medieval mythographers including Dante added interpretations involving the limits of power and the dangers of prodigality, until in the Lusiads and Cynthia's Reveh the myth could embody tensions between politics and love. Petrarch uses Actaeon's metamorphosis as part of a spiritual autobiography, and Petrarchan lovers all the way to Shakespeare's Orsino remain under this influence. Christianizers like the poet of the Ovide Moralisé and Platonists like Bruno see the story in visionary terms. All these significations cluster together in two Renaissance masterpieces: Titian's Diana Surprised by Actaeon, where carnal voyeurism is combined with Platonic contemplation, and Shakespeare's A Midsummer Night's Dream, in which the meeting of Bottom and Titania affirms that in the world of syncretic comedy forbidden visions need not always be forbidden
The Intersection of Conflict-related Sexual Violence Against Men, Boys, and LGBTQI+ Persons and Human Trafficing
No full textThe genesis of the workshop was a desire to understand how conflict-related sexual violence (CRSV) intersects with the crime of trafficking and to examine the role that gender, sex, sexual orientation and gender identities/
expression (SOGIE) and age play in creating vulnerabilities. The workshop included keynotes and presentations by experts from the fields of CRSV, trafficking human beings (THB), and issues relating to SOGIE.
The workshop explored the intersection of CRSV and THB against men, boys, and lesbian, gay, bisexual, transgender, transsexual, intersexual, and other individuals whose sexual and/or gender identity differs from the cis heterosexual. In 2016, United Nations (UN) Security Council Resolution 2331 addressed the nexus between trafficking in human beings and CRSV, as well as the gender-related nature of these crimes. In the 2018 report on CRSV, the UN Secretary-General reemphasized the importance of addressing the link with human trafficking for purposes of sexual exploitation
in conflict. The armed conflict in Ukraine has again brought this problem to the foreground. Allegations of sexual violence, including against
men and boys, have been reported to national and international agencies. But the complexity of the nexus between CRSV and human trafficking is still not well understood, particularly in the case of men, boys, and
LGBTQI+ persons.
The workshop brought together 36 international experts from each field of
knowledge to identify and discuss possible lacunae in present research on the nexus between CRSV against men, boys, and LGBTQI+ persons and human trafficking; to assess potential legal, policy, and programmatic gaps
in the responses to trafficked victims/survivors of CRSV; and to determine the need and direction for follow-up research on the topic
CODEBench: A Neural Architecture and Hardware Accelerator Co-Design Framework
No full textRecently, automated co-design of machine learning (ML) models and accelerator architectures has attracted significant attention from both the industry and academia. However, most co-design frameworks either explore a limited search space or employ suboptimal exploration techniques for simultaneous design decision investigations of the ML model and the accelerator. Furthermore, training the ML model and simulating the accelerator performance is computationally expensive. To address these limitations, this work proposes a novel neural architecture and hardware accelerator co-design framework, called CODEBench. It comprises two new benchmarking sub-frameworks, CNNBench and AccelBench, which explore expanded design spaces of convolutional neural networks (CNNs) and CNN accelerators. CNNBench leverages an advanced search technique, BOSHNAS, to efficiently train a neural heteroscedastic surrogate model to converge to an optimal CNN architecture by employing second-order gradients. AccelBench performs cycle-accurate simulations for diverse accelerator architectures in a vast design space. With the proposed co-design method, called BOSHCODE, our best CNN-accelerator pair achieves 1.4% higher accuracy on the CIFAR-10 dataset compared to the state-of-the-art pair while enabling 59.1% lower latency and 60.8% lower energy consumption. On the ImageNet dataset, it achieves 3.7% higher Top1 accuracy at 43.8%
lower latency and 11.2% lower energy consumption. CODEBench outperforms the state-of-the-art framework, i.e., Auto-NBA, by achieving 1.5% higher accuracy and 34.7× higher throughput while enabling 11.0× lower energy-delay product (EDP) and 4.0× lower chip area on CIFAR-10