Sizable Enhancement Research Articles

Ultrafast antiferromagnetic switching of Mn2Au with laser-induced optical torques

Ultrafast manipulation of the Néel vector in metallic antiferromagnets most commonly occurs by generation of spin-orbit (SOT) or spin-transfer (STT) torques. Here, we predict another possibility for antiferromagnetic domain switching by using novel laser optical torques (LOTs). We present results of atomistic spin dynamics simulations from the application of LOTs for all-optical switching of the Néel vector in the antiferromagnet Mn2Au. The driving mechanism takes advantage of the sizeable exchange enhancement, characteristic of antiferromagnetic dynamics, allowing for picosecond 90 and 180-degree precessional toggle switching of the Néel vector with laser fluences on the order of mJ/cm2. A special symmetry of these novel torques greatly minimises the over-shooting effect common to precessional spin switching by SOT and STT methods. We demonstrate the opportunity for LOTs to produce deterministic, non-toggle switching of single antiferromagnetic domains. Lastly, we show that even with sizeable ultrafast heating by laser in metallic systems, there exist a large interval of laser parameters where the LOT-assisted toggle and preferential switchings in magnetic grains have probabilities close to one. The proposed protocol could be used on its own for all-optical control of antiferromagnets for computing or memory storage, or in combination with other switching methods to lower energy barriers and/or to prevent over-shooting of the Néel vector.

Controllable Sign Reversal of the Seebeck Coefficient and Thermoelectric Performance of the Janus MoSH Monolayer.

The Janus MoSH monolayer has attracted extensive attention from researchers; however, to our knowledge, there is no work yet to investigate the thermoelectric properties governed by electron-phonon (e-ph) interactions of the Janus MoSH monolayer in detail, either experimentally or theoretically. In this work, we carry out first-principles calculations on the thermoelectric performance of the MoSH monolayer in the presence of e-ph scattering by solving the Boltzmann transport equation iteratively. We find that by adjusting the Fermi level to the nearby band edge which corresponds to the van Hove singularity (VHS), the sign of the Seebeck coefficient of MoSH can be inverted and the ZT value (figure of merit) increases about 13 times (from 0.0011 to 0.0145). This sizable enhancement of ZT value requires not only the existence of the VHS at Fermi level, but also a constant Fermi surface. Such a case is expected to occur often in realistic materials, not limited only to the MoSH monolayer. In view of the nature of two-dimensional (2D) materials, the Fermi level of the Janus MoSH monolayer can be readily controlled by applying a gate voltage instead of chemical carrier doping. As such, our study proposes a feasible way to control the thermoelectric performance in a 2D structure.

PDSMNet: Parallel pyramid dual-stream modeling for automatic lung COVID-19 infection segmentations

Artificial intelligence-based segmentation models can assist the early-stage detection of lung COVID-19 infections or lesions from medical images with higher efficiency versus traditional techniques, yet challenges remain attributable to factors such as heterogeneities in infection traits, small infection regions, blurred boundary context, mixtures of varying infection regions, and obscure intensity contrast between lesions and normal tissues. This study aims to improve the performance of automatic segmentation of lung COVID-19 infections by proposing a novel approach named parallel pyramid dual-stream modeling network (PDSMNet) with two major contributions: (1) refined design of the framework including (a) a transformer module termed parallel pyramid dual-stream module (PDSM) to effectively preserve channel, spatial, and other latent features; (b) fusion of a multi-scale pyramid parallel-pooling module (MPM) that extracts features in parallel at differentiated scales; (c) calibration of the skip-connection architectures to optimize prediction and preserve features; (d) calibration of attention mechanisms reflecting multiple sources of information including parallel-, serial-, and cross-attention contexts; and (e) improvement of the integral functionality of the framework in curtailing the burdens of parameter computations in a multi-modality scenario. (2) loss functions accounting for the training losses of normal tissues, diseases, and boundaries respectively to enhance the performance of the network. The calibrated loss design allowing for a margin improves the capacity of predictions. We conducted experiments using three different datasets with different modalities and compared the proposed framework PDSMNet with two other benchmarks and eight similar state-of-the-art (SOTA) networks. The experiments observed consistent performance improvements across all datasets. PDSMNet attained asymptotically a maximum increase of 16.5%, 6.2%, and 15.5% for mean F1 score (mF1S), mean dice-score coefficient (mDSC), mean intersection over union (mIoU) versus SOTA PDEAtt-UNet, a maximum increase of 49.6%, 25.6%, and 38.0% for mF1S, mDSC, and mIoU versus InfNet, a maximum increase of 26.1%, 10.8%, 21.8% versus MiniSeg, a maximum increase of 14.0%, 3.0%, and 13.4% versus TransUNet, and a maximum increase of 37.9%, 16.8%, 31.2% versus Attention-UNet respectively. For other SOTA models such as MT-UNet, UCTransNet, and UTNetV2, a sizeable enhancement of performance was observed as well. PDSMNet also yielded asymptotically a maximum 30.6%, 14.8%, 26.3% increase of mF1S, mDSC, mIoU versus benchmark UNet, and a maximum increase of 42.8%, 21.5%, 33.3% versus benchmark UNet++ respectively. PDSMNet demonstrated reduced computational costs as well, yielding approximately 0.53 M of parameters and 6.55G of floating-point operations per second (FLOPs) respectively using different datasets, and the quantitative and qualitative ablation tests reinforced the effectiveness of the various components of the proposed framework.

Controlled Frustration Release on the Kagome Lattice by Uniaxial-Strain Tuning.

It is predicted that strongly interacting spins on a frustrated lattice may lead to a quantum disordered ground state or even form a quantum spin liquid with exotic low-energy excitations. However, a controlled tuning of the frustration strength, separating its effects from those of disorder and other factors, is pending. Here, we perform comprehensive ^{1}H NMR measurements on Y_{3}Cu_{9}(OH)_{19}Cl_{8} single crystals revealing an unusual Q[over →]=(1/3×1/3) antiferromagnetic state below T_{N}=2.2 K. By applying insitu uniaxial stress, we break the symmetry of this disorder-free, frustrated kagome system in a controlled manner yielding a linear increase of T_{N} with strain, in line with theoretical predictions for a distorted kagome lattice. In-plane strain of ≈1% triggers a sizable enhancement ΔT_{N}/T_{N}≈10% due to a release of frustration, demonstrating its pivotal role for magnetic order.

Atom Interferometry with Coherent Enhancement of Bragg Pulse Sequences.

We report here on the realization of light-pulse atom interferometers with large-momentum-transfer atom optics based on a sequence of Bragg transitions. We demonstrate momentum splitting up to 200 photon recoils in an ultracold atom interferometer. We highlight a new mechanism of destructive interference of the losses leading to a sizable efficiency enhancement of the beam splitters. We perform a comprehensive study of parasitic interferometers due to the inherent multiport feature of the quasi-Bragg pulses. Finally, we experimentally verify the phase shift enhancement and characterize the interferometer visibility loss.

Cavity-renormalized quantum criticality in a honeycomb bilayer antiferromagnet

Strong light-matter interactions as realized in an optical cavity provide a tantalizing opportunity to control the properties of condensed matter systems. Inspired by experimental advances in cavity quantum electrodynamics and the fabrication and control of two-dimensional magnets, we investigate the fate of a quantum critical antiferromagnet coupled to an optical cavity field. Using unbiased quantum Monte Carlo simulations, we compute the scaling behavior of the magnetic structure factor and other observables. While the position and universality class are not changed by a single cavity mode, the critical fluctuations themselves obtain a sizable enhancement, scaling with a fractional exponent that defies expectations based on simple perturbation theory. The scaling exponent can be understood using a generic scaling argument, based on which we predict that the effect may be even stronger in other universality classes. Our microscopic model is based on realistic parameters for two-dimensional magnetic quantum materials and the effect may be within the range of experimental detection.

Ultrahigh dielectric permittivity in oxide ceramics by hydrogenation.

Boosting dielectric permittivity representing electrical polarizability of dielectric materials has been considered a keystone for achieving scientific breakthroughs as well as technological advances in various multifunctional devices. Here, we demonstrate sizable enhancements of low-frequency dielectric responses in oxygen-deficient oxide ceramics through specific treatments under humid environments. Ultrahigh dielectric permittivity (~5.2×106 at 1 Hz) is achieved by hydrogenation, when Ni-substituted BaTiO3 ceramics are exposed to high humidity. Intriguingly, thermal annealing can restore the dielectric on-state (exhibiting huge polarizability in the treated ceramics) to the initial dielectric off-state (displaying low polarizability of ~103 in the pristine ceramics after sintering). The conversion between these two dielectric states via the ambient environment-mediated treatments and the successive application of external stimuli allows us to realize reversible control of dielectric relaxation characteristics in oxide ceramics. Conceptually, our findings are of practical interest for applications to highly efficient dielectric-based humidity sensors.

Non-uniform superlattice magnetic tunnel junctions

We propose a new class of non-uniform superlattice magnetic tunnel junctions (Nu-SLTJs) with the linear, Gaussian, Lorentzian, and Pöschl–Teller width and height based profiles manifesting a sizable enhancement in the TMR (≈104 − 106%) with a significant suppression in the switching bias (≈9 folds) owing to the physics of broad-band spin filtering. By exploring the negative differential resistance region in the current–voltage characteristics of the various Nu-SLTJs, we predict the Nu-SLTJs offer fastest spin transfer torque switching in the order of a few hundred picoseconds. We self-consistently employ the atomistic non-equilibrium Green’s function formalism coupled with the Landau–Lifshitz–Gilbert–Slonczewski equation to evaluate the device performance of the various Nu-SLTJs. We also present the design of minimal three-barrier Nu-SLTJs having significant TMR (≈104%) and large spin current for the ease of device fabrication. We hope that the class of Nu-SLTJs proposed in this work may lay the bedrock to embark on the exhilarating voyage of exploring various non-uniform superlattices for the next generation of spintronic devices.

Behavior of lap splices in reinforced concrete beams after bar yielding

AbstractStructural ductility in the case of plastic hinges forming close to a lap splice has been an open issue with the revision process of the next version of Eurocode EC2 concerning reinforced‐concrete structures. This research has provided experimental evidence by the large experimental campaign for the background for revision of the Eurocode EC2. Within this context, 38 specimens were tested in four‐point bending, with the longitudinal bars either lap‐spliced (partly or fully), or un‐spliced (for reference). The tests were carried out involving the variation of the bar diameter (12, 16, 20, and 25 mm), and the lap length (20–60 times the bar diameter). The main result is the sizeable enhancement of the structural ductility brought in by the extension of the lap length in excess of the length required by the yielding of the longitudinal bars. Based on these findings, a preliminary model is developed to describe the bond‐stress profiles in lap splices, after the yielding of the bars.

Neutrino forces and the Sommerfeld enhancement

The Sommerfeld enhancement plays an important role in dark matter (DM) physics, and can significantly enhance the annihilation cross section of non-relativistic DM particles. In this paper, we study the effect of neutrino forces, which are generated by the exchange of a pair of light neutrinos, on the Sommerfeld enhancement. We demonstrate that in certain cases, a neutrino force can cause a significant correction to the Sommerfeld enhancement. Models that can realise DM-neutrino interactions and sizeable Sommerfeld enhancement are also briefly discussed, together with the impacts on DM phenomenology of neutrino forces.

SERS and EC-SERS detection of local anesthetic procaine using Pd loaded highly reduced graphene oxide nanocomposite substrate

The localized surface plasmon resonance (LSPR) excitations are critical towards achieving sizable spectral enhancements of the Raman scattered light. Herein, the synthesis of palladium-based highly reduced graphene oxide (Pd-HRG) with LSPR properties as an effective surface-enhanced Raman scattering (SERS) substrate and its utility in the highly sensitive detection of procaine are reported. The concentration detection of procaine samples was optimized by applying a set of pre-concentration parameters. The Pd-HRG nanocomposite showed a remarkable LSPR response with a Raman enhancement factor of 8.7 × 102. The Pd-HRG is employed to modify fluorine doped tin oxide electrode (Pd-HRG/FTO), resulted with an enhancement factor of 7.5 × 104 corresponding to the EC-SERS technique. The electronic and surface properties of synthesized Pd-HRG and functionalized FTO electrode were evaluated using Raman, infrared, EIS, XRD, FESEM and EDX techniques. Quantum chemical calculations were carried out to elaborate on the nature of interaction of procaine molecules with a nanostructured surface model. Pd-HRG, with an efficient and cost-effective fabrication, can be considered as a promising EC-SERS substrate for the detection of organic therapeutic drugs.

Magic angle spinning dynamic nuclear polarization solid-state NMR spectroscopy of γ-irradiated molecular organic solids

In the past 15 years, magic angle spinning (MAS) dynamic nuclear polarization (DNP) has emerged as a method to increase the sensitivity of high-resolution solid-state NMR spectroscopy experiments. Recently, γ-irradiation has been used to generate significant concentrations of homogeneously distributed free radicals in a variety of solids, including quartz, glucose, and cellulose. Both γ-irradiated quartz and glucose previously showed significant MAS DNP enhancements. Here, γ-irradiation is applied to twelve small organic molecules to test the applicability of γ-irradiation as a general method of creating stable free radicals for MAS DNP experiments on organic solids and pharmaceuticals. Radical concentrations in the range of 0.25 ​mM–10 ​mM were observed in irradiated glucose, histidine, malic acid, and malonic acid, and significant 1H DNP enhancements of 32, 130, 19, and 11 were obtained, respectively, as measured by 1H→13C CPMAS experiments. However, concentrations of free radicals below 0.05 ​mM were generally observed in organic molecules containing aromatic rings, preventing sizeable DNP enhancements. DNP sensitivity gains for several of the irradiated compounds exceed that which can be obtained with the relayed DNP approach that uses exogeneous polarizing agent solutions and impregnation procedures. In several cases, significant 1H DNP enhancements were realized at room temperature. This study demonstrates that in many cases γ-irradiation is a viable alternative to addition of stable exogenous radicals for DNP experiments on organic solids.

Study of Z Bosons Produced in Association with Charm in the Forward Region

Events containing a Z boson and a charm jet are studied for the first time in the forward region of proton-proton collisions. The data sample used corresponds to an integrated luminosity of 6 fb^{-1} collected at a center-of-mass energy of 13 TeV with the LHCb detector. In events with a Z boson and a jet, the fraction of charm jets is determined in intervals of Z-boson rapidity in the range 2.0<y(Z)<4.5. A sizable enhancement is observed in the forwardmost y(Z) interval, which could be indicative of a valencelike intrinsic-charm component in the proton wave function.

Large enhancement of total reaction cross sections at the edge of the island of inversion in Ti, Cr, and Fe isotopes

A systematic analysis of nuclear deformation is made for neutron-rich Ti, Cr, and Fe isotopes to explore the nuclear structure in the island of inversion near N = 40, where strong nuclear deformation is predicted. The nuclear ground states are obtained by the Skyrme Hartree-Fock method in three-dimensional coordinate space, which properly describes any nuclear shape. Three types of Skyrme interactions are employed to generate various deformed states in its isotopic chain. We find that in the island of inversion the occupation of highly elongated intruder orbits induces not only large quadrupole deformation but also large hexadecapole deformation. This appears as a sizable enhancement of the nuclear matter radius, showing the characteristic shell effect of the density profile near the nuclear surface. We show that the edge of the island of inversion, where the intruder orbit starts being occupied, can be determined by measuring the enhancement of the total reaction cross section at high incident energy. The possibility of constraining the hexadecapole deformation by a measurement of the total reaction cross sections is discussed.

Process evaluation and kinetic analysis of 3D-printed monoliths comprised of CaO and Cr/H-ZSM-5 in combined CO2 Capture-C2H6 oxidative dehydrogenation to C2H4

In this study, dual-function materials (DFMs) comprised of CaO and Cr/H-ZSM-5 were formulated in 3D-printed monolithic structures and investigated in a combined process for capture and utilization of CO2in oxidative dehydrogenation of C2H6 to C2H4 (CO2-ODHE). Various formulation strategies were employed to fabricate these DFM structures. Two bed designs were considered: i) a layered-bed in which adsorbent (CaO) and catalyst were printed separately and stacked on top of each other, and ii) a single-layer bed where the adsorbent-catalyst materials were 3D-printed into a singular monolith and loaded into the bed as DFMs. Between these, the layered-bed displayed enhanced performance as compared to the composite DFMs, as this configuration generated a 3.73 mmol/g CO2 adsorption capacity, 42.5% C2H6 conversion, 90.6% C2H4 selectivity and 38.6% C2H4 yield compared to 2.4 mmol/g CO2 adsorption capacity, 37.9% C2H6 conversion, 89% C2H4 selectivity and 33.8% C2H4 yield in the best singular monolith configuration. The enhanced performance of this configuration was attributed to a higher degree of adsorptive site accessibility and a lesser degree of active site blockage from intraparticle binding (as evident from the textural properties). This work also assessed the effects of monolith cell density on CO2 adsorption and utilization for ODHE by varying the cells per square inch (cpsi) from 200 to 600 cpsi. These experiments revealed that increasing the cell density from 200 to 600 cpsi enhanced the overall mass transfer coefficient from 0.40 × 10-2 to 1.01 × 10-2 s-1 due to a sizable enhancement in film mass transfer between the two geometric designs. Such enhancement improved the C2H4 selectivity and yield to 92 and 45.1% in the 600 cpsi sample. As such, this work also indicated that higher cell densities lead to better performance of the layered-bed configuration, where the optimum configuration is separate stacking of the adsorbent and catalyst phases. Overall, these findings provide a deeper understanding of DFM materials, bed configuration, and establish a groundwork which can be used to optimize their structures for CO2 adsorption-reaction processes.

Variation in cosmic ray flux during Solar Eclipse on 21 June, 2020 at Jaipur, India

Variation in gamma ray flux was recorded during the Annular Solar Eclipse on 21 June, 2020 at Jaipur, India where 88.3% of the solar disk was eclipsed. Two Sodium Iodide NaI (Tl) scintillation detectors were employed for the experiment and flux was recorded in the energy range 300 keV to 2 MeV. The first detector employed to record data for the duration of 3 h and 30 min records a sizeable enhancement at the characteristic energy 1460 keV and the corresponding single escape peak at 949 keV. No substantial variation in the radiations was noticed by the detector employed for recording data for 20 critical minutes during the peak of the eclipse.

Heavy neutral leptons in effective field theory and the high-luminosity LHC

Heavy neutral leptons (HNLs) with masses around the electroweak scale are expected to be rather long-lived particles, as a result of the observed smallness of the active neutrino masses. In this work, we study long-lived HNLs in NRSMEFT, a Standard Model (SM) extension with singlet fermions to which we add non-renormalizable operators up to dimension-6. Operators which contain two HNLs can lead to a sizable enhancement of the production cross sections, compared to the minimal case where HNLs are produced only via their mixing with the SM neutrinos. We calculate the expected sensitivities for the ATLAS detector and the future far-detector experiments: AL3X, ANUBIS, CODEX-b, FASER, MATHUSLA, and MoEDAL-MAPP in this setup. The sensitive ranges of the HNL mass and of the active-heavy mixing angle are much larger than those in the minimal case. We study both, Dirac and Majorana, HNLs and discuss how the two cases actually differ phenomenologically, for HNL masses above roughly 100 GeV.

Enhancement of the double Higgs production via leptoquarks at the LHC

Measurements of single Higgs production and its decays are in good agreement with the Standard Model. There is still room for large modifications in double Higgs production at LHC, though these effects may be correlated with large corrections to other observables, in particular single Higgs production. In this work we address the issue of enhancing double Higgs production in the presence of scalar leptoquarks while satisfying all experimental constraints. We show at leading order that including more than one species of leptoquarks, large cubic interactions with the Higgs can lead to sizable enhancement of di-Higgs production cross section at LHC, while at the same time keeping other Higgs observables and precision measurements under control. For masses above 800 GeV these corrections are in general below 30%, whereas in a viable scenario in which one of the leptoquarks can be light, specifically in the mass range 400 − 600 GeV, we show that it is possible to roughly double the SM cross section for di-Higgs production, implying that possible first hints of it may be probed at the high luminosity LHC at mathcal{L} ∼ 2 ab−1.

Marine macroalgae biofabricated silver nanoparticles as naked-eye colorimetric and turn-on fluorescent sensor for cyanide ions in aqueous media

The present study investigated the naked eye colorimetric and turn on fluorescent detection of cyanide ions in aqueous medium using marine macroalgae (seaweed) mediated biosynthesized silver nanoparticles (AgNPs). The bioactive metabolites in the seaweed extract act as reducing agents to produce nanoparticles. They also act as capping agent and stabilizer for them. Since no extra reducing and stabilizing agents were used in the synthetic route, it is completely a green chemistry approach. In addition, this method is facile, fast and cost effective. The biosynthesized AgNPs were characterized using UV–vis spectroscopy, HR-TEM and XRD techniques. The biogenic AgNPs are dark brown in colour due to the intense surface plasmon resonance absorption band. In the presence of CN- ions, the brown AgNPs solution turned to colourless accompanying the disappearance of absorption maximum at 414 nm along with a sizable enhancement in fluorescence intensity. The selectivity and sensitivity of biogenic AgNPs towards CN- ions were also studied and the limit of detection was found to be 1 μM. The cyanide sensing mechanism is also proposed based on TEM analysis. Moreover a test strip approach is developed for real time detection of CN- ions. The proposed method has been successfully used for the determination of cyanide in water samples.

Manipulated Optical Absorption and Accompanied Photocurrent Using Magnetic Field in Charger Transfer Engineered C/ZnO Nanowires.

The rarely explored, spin‐polarized band engineering, enables direct dynamic control of the magneto‐optical absorption (MOA) and associated magneto‐photocurrent (MPC) by a magnetic field, greatly enhancing the range of applicability of photosensitive semiconductor materials. It is demonstrated that large negative and positive MOA and MPC effects can be tuned alternately in amorphous carbon (a‐C)/ZnO nanowires by controlling the sp2/sp3 ratio of a‐C. A sizeable enhancement of the MPC ratio (≈15%) appears at a relatively low magnetic field (≈0.2 T). Simulated two peaks spin‐polarized density of states is applied to explain that the alternate sign switching of the MOA is mainly related to the charge transfer between ZnO and C. The results indicate that the enhanced magnetic field performance of (a‐C)/ZnO nanowires may have applications in renewable energy‐related fields and tunable magneto‐photonics.