Large Decay Research Articles

Relativity and diversity of strong coupling in coupled plasmon-exciton systems

Strong coupling between quantum emitters and photonic modes, at which the level splitting (LS) of the mixed quantum states occurs, has aroused great interest due to diverse important quantum applications. The spectral Rabi-splitting (SRS) in photon emission or absorption has been extensively used to characterize strong coupling based on the equality assumption by assigning the SRS to LS. Here, we demonstrate that the equality assumption is usually invalid via a unified quantum treatment on the coupled plasmon-exciton system. It is revealed that the strong coupling characterized by the SRS is easily observed from the subsystem with larger decay, manifesting itself in relativity and diversity, which is highly correlated to the dissipative decays of the coupling subsystems. The plasmon-exciton interactions can be classified into the weak coupling, pseudo-, dark-, intermediate- and super-strong coupling regimes. Our work not only enriches the underlying physics of strong light-matter interactions, but also may stimulate further experimental researches in this field.

Low Threshold Room Temperature Polariton Lasing from Fluorene‐Based Oligomers

AbstractOrganic semiconductors possessing tightly bound Frenkel excitons are known to be attractive candidates for demonstrating polariton lasing at room temperature. As polariton lasing can occur without inversion, it is a potential route to very low threshold coherent light sources. However, so far, the thresholds of organic polariton lasers have generally been much higher than those of organic photon lasers. Here this problem has been addressed by investigating two new organic molecules with a structure combining fluorene and carbazole groups. The materials are readily deposited from solution and exhibit high photoluminescence quantum yields, high absorption coefficients, and large radiative decay rates in neat films. Room temperature polariton lasing is realized in both materials with incident thresholds of 13.5 and 9.7 µJ cm−2, corresponding to absorbed thresholds of 3.3 and 2.2 µJ cm−2, respectively. These are the lowest values reported to date for polariton lasing in organic semiconductor materials, and approach typical values for organic photon lasers. The step‐like power dependent blue‐shift of polariton modes indicates an interplay between different depletion channels of the exciton reservoir. This work brings practical room temperature polaritonic devices and future realization of electrically driven polariton lasers a step closer.

Sn and Na Co‐doping to Suppress Voltage Decay of Li‐rich Layered Oxide

AbstractLi‐rich layered oxides (LLOs) as cathode materials are expected to be applied to advanced lithium‐ion batteries (LIBs) with great potential. However, the electrochemical instability and large voltage decay seriously restrict their development. In this work, a novel LLO cathode material (SN‐LLO) with Sn and Na co‐doping is fabricated through a co‐precipitation process with subsequent calcination, which exhibits enhanced electrochemical stability and suppressed voltage decay. Structural characterizations indicate that with the regulation of Na doping, the impurity Li2SnO3 is inhibited and layered SN‐LLO solid solution with the arrangement of Sn in layers and stacking faults along c axis is obtained. DFT calculations demonstrate that the enhanced electrochemical stability results from the increase in the energy barrier of Mn migration in the slabs due to the steric effect of Sn. This study provides a rational design idea to improve the electrochemical stability of advanced Li‐rich layered oxides.

Weak decays of bottom-charm baryons: mathcal {B}_{bc}rightarrow mathcal {B}_bP

After the discovery of the double-charm baryon Xi _{cc}^{++} by LHCb, one of the most important topics is to search for the bottom-charm baryons which contain a b quark, a c quark and a light quark. In this work, we study the two-body non-leptonic weak decays of a bottom-charm baryon into a spin-1/2 bottomed baryon and a light pseudoscalar meson with the short-distance contributions calculated under the factorization hypothesis and the long-distance contributions considering the final-state-interaction effects. The branching fractions of all fifty-seven decay channels are estimated. The results indicate that Xi _{bc}^+rightarrow Xi _b^0pi ^+, Xi _{bc}^{0}rightarrow Xi _{b}^{-}pi ^+ and Omega _{bc}^0rightarrow Omega _b^-pi ^+ decay modes have relatively large decay rates and thus could be used to experimentally search for the bottom-charm baryons. The topological diagrams and the SU(3) symmetry of bottom-charm baryon decays are discussed.

Marble decay: towards a measure of marble degradation based on ultrasonic wave velocities and thermal expansion data

Marble as ornamental and dimensional stones as well as in their natural environments show complex weathering phenomena. Physical, chemical, and biological weathering of marble are well documented. The impact of climate change on monuments and historic buildings in terms of modeling and predicting future scenarios requires new approaches to forecast the ongoing decay in the near and far future. Ultrasonic wave velocities are a powerful and sensitive tool for the damage assessment of marble. For a maximum porosity of up to 1%, ultrasonic wave velocities (P-wave velocities) are ranging between 1 km/s and over 6 km/s. Water saturation has an important influence on the magnitude and directional dependence of ultrasonic wave velocities together with the mineralogical composition and the rock fabrics. Ongoing experimental alteration approaches were used to document the state of deterioration using Vp-systematics. In addition, thermal expansion and the residual strain values after applying thermal impacts were used to introduce a new quantitative measure based on experimental length changes and volume changes. To quantify such volume changes, a so-called decay index was proposed. Marbles are sensitive to weathering and have different volume changes under exposure depending on fabric parameters. The volume extension index of marble, based on thermal expansion measurements under dry and water-saturated conditions, is proposed as a decay index for quantifying sample stability and for defining the directions of maximum and minimal dilatation. Such decay index was implemented to different marble types and it was turned out that marbles with the larger decay indexes are more prone to weathering than with smaller ones. The effect of changing climate and, in consequence, different weathering actions can help to calculate or forecast risk numbers based on the Vp data in combination with the proposed decay index especially for marbles.

Tree size and crown structure explain the presence of cavities required by wildlife in cool-temperate forests of South America

Maintenance of tree cavity supply is a global conservation priority for forest wildlife, which requires understanding the ecology and population dynamics of cavity-bearing trees. Explaining the occurrence of cavities in trees is particularly important in ecosystems where most secondary cavity-users (SCUs) are critically dependent on the slow formation of cavities by wood-decay processes. Our main objectives were (1) to explain the distribution of decay cavities in trees according to their individual attributes and, (2) to quantify the relative importance of each individual tree attribute to determine the presence of decay cavities. We focused on medium and large decay cavities (smallest entrance dimension ≥ 5 cm), which can limit populations of management-sensitive SCUs. We measured forest attributes and inspected cavities in trees (n = 860) and snags (n = 93) in six 0.5 ha plots from old- and second-growth Nothofagus dombeyi forest stands. We used generalised linear mixed-effects models (GLMM) to analyse the distribution of decay cavities in trees using data on their presence/absence, based on several tree individual attributes, across different sites. We applied an information-theoretical and multi-model inference approach to quantify the strength of alternative sets of hypotheses/models. We used model averaging, which allows estimating coefficients and making inferences that account for model and parameter uncertainty. Diameter at breast height (DBH), crown damage and decay, crown ratio (crown length • trunk length−1) and woodpecker foraging signs were important to explain the presence/absence of decay cavities in trees. Diameter at breast height, woodpecker foraging signs and a moderate-high crown damage and decay were positively related with decay cavity presence. The presence of medium and large decay cavities was also positively related with DBH, but trees with low crown ratios had relatively low probabilities of presenting these cavities, even with DBHs > 150 cm. Trees with DBHs smaller than 50 cm had very low probabilities (<0.25–0.30) to present decay cavities, while the probability of trees presenting decay cavities of medium and large sizes was very low for trees with diameters < 100 cm, even for trees with high crown ratios. Our results point out that conservation of large diameter trees with high crown ratios is important to maintain the supply of decay cavities required by management-sensitive SCUs in these forests. As these keystone structures are globally threatened by climate change induced disturbances (e.g. fires, droughts), they should be maintained/restored through forest management (e.g. retention of keystone structures) to achieve cavity-using wildlife habitat conservation in the long-term.

Global existence and large time behavior of strong solutions to the nonhomogeneous heat conducting magnetohydrodynamic equations with large initial data and vacuum

We investigate an initial boundary value problem of two-dimensional nonhomogeneous heat conducting magnetohydrodynamic equations. We prove that there exists a unique global strong solution. Moreover, we also obtain the large time decay rates of the solution. Note that the initial data can be arbitrarily large and the initial density allows vacuum states. Our method relies upon the delicate energy estimates and Desjardins’ interpolation inequality (B. Desjardins, Regularity results for two-dimensional flows of multiphase viscous fluids, Arch. Rational Mech. Anal. 137(2) (1997) 135–158).

Dissipatively Controlled Optomechanical Interaction via Cascaded Photon-Phonon Coupling.

In an optomechanical system, we experimentally engineer the optical density of state to reduce or broaden the effective linewidth of the optical mode by introducing an ancillary mechanical mode, which has a large decay rate, i.e., stimulated backward Brillouin scattering. Based on this dissipation engineering, we could engineer the optical mode linewidth by one order of magnitude. In addition, we can either enhance or suppress the optomechanical cooling and amplification of the target mechanical oscillations. Our scheme demonstrates the cascaded photon-phonon coupling to control the mechanical interactions, and also presents a novel approach for engineering coherent light-matter interaction in hybrid systems, which consist of different types of nonlinear interactions and multiple modes, and promote the performance of quantum devices.

Large Time Decay of Solutions to a Linear Nonautonomous System in Exterior Domains

In this expository paper, we study Lq-Lr decay estimates of the evolution operator generated by a perturbed Stokes system in n-dimensional exterior domains when the coefficients are time-dependent and can be unbounded at spatial infinity. By following the approach developed by the present author for the physically relevant case where the rigid motion of the obstacle is time-dependent, we clarify that some decay properties of solutions to the same system in whole space Rn together with the energy relation imply the desired estimates in exterior domains provided n≥3.

Global Existence and the Decay of Solutions to the Prandtl System with Small Analytic Data

In this paper, we prove the global existence and the large time decay estimate of solutions to Prandtl system with small initial data, which is analytical in the tangential variable. The key ingredient used in the proof is to derive sufficiently fast decay-in-time estimate of some weighted analytic energy estimate to a quantity, which consists of a linear combination of the tangential velocity with its primitive one, and which basically controls the evolution of the analytical radius to the solutions. Our result can be viewed as a global-in-time Cauchy-Kowalevsakya result for Prandtl system with small analytical data.

Large time behavior of solutions to a Stokes-Magneto equations in three dimensions

This paper is devoted to the large time decay of solutions of a three-dimensional Stokes-Magneto equations. It is shown that, when initial data belong to $$L^2$$ , weak solutions of the equations decay to zero in $$L^{3/2,\infty }\times L^2$$ without a uniform rate, and this decay estimate is optimal. Furthermore, the optimal temporal decay estimates for weak solutions are established when initial data belongs to $$L^1\cap L^2$$ .

THE IMPACT OF COVID-19 PANDEMIC LOCKDOWN ON THE MIGRANT LABOUR CRISIS AND CARDAMOM HARVEST IN HIGH RANGES OF KERALA

This paper analyses the situation of cardamom planters and plantations against the backdrop of COVID-19 pandemic and lack of migrant labor during the harvesting season. The global pandemic resulted in large scale exodus of migrant labor across India. For more than a decade, the cardamom plantations in high ranges of Kerala depended on large-scale migrant labor force for weeding, manual irrigation, spraying of pesticides and fertilizers, and handpicking cardamom cloves. As the cultivation of cardamom is highly labor intensive, the scarcity of labor force resulted in large scale decay of unplucked cardamom cloves in various plantations. The shortage of labor force also resulted in a drastic increase in labor cost for hand picking of cardamom cloves from the plants. The cardamom is harvested around four times a year, but the initial harvest during the ongoing pandemic witnessed a fall in the price. This study focuses on unstructured interviews and conversations with large scale and small-scale planters, labourers, cardamom traders and people employed in commercial large scale drying of cardamom. The findings suggest that many cultivators organized various strategies to overcome the migrant labor crisis such as employing unskilled labourers at a high cost, bringing migrant labourers from their hometowns in private buses at the expense of cultivators. The migrant labor crisis also provided an employment opportunity for many people who lost their livelihood during the lockdown. The attempt here is to look at the larger transformation from below and contextualize the local transformations in the larger economic milieu.

Seeking the origins of a mysteriously large decay length in electrolytes

Researchers aim to corroborate experimental evidence of long-range decay with theory and simulations of primitive model electrolytes.

Global Existence and Large Time Behavior of Strong Solutions for 3D Nonhomogeneous Heat-Conducting Magnetohydrodynamic Equations

We are concerned with an initial boundary value problem of nonhomogeneous heat-conducting magnetohydrodynamic equations in a bounded simply connected smooth domain $$\Omega \subseteq {\mathbb {R}}^3$$ , with Navier-slip boundary conditions for the velocity and magnetic field and Neumann boundary condition for the temperature. We prove the global existence of a unique strong solution provided that $$\left( \Vert \sqrt{\rho _0}{\mathbf {u}}_0\Vert _{L^2}^2 +\Vert {\mathbf {b}}_0\Vert _{L^2}^2\right) $$ $$\left( \Vert {{\,\mathrm{curl}\,}}{\mathbf {u}}_0\Vert _{L^2}^2 +\Vert {{\,\mathrm{curl}\,}}{\mathbf {b}}_0\Vert _{L^2}^2\right) $$ is suitably small. Moreover, we also obtain large time decay rates of the solution.

Primitive model electrolytes in the near and far field: Decay lengths from DFT and simulations

Inspired by recent experimental observations of anomalously large decay lengths in concentrated electrolytes, we revisit the Restricted Primitive Model (RPM) for an aqueous electrolyte. We investigate the asymptotic decay lengths of the one-body ionic density profiles for the RPM in contact with a planar electrode using classical Density Functional Theory (DFT) and compare these with the decay lengths of the corresponding two-body correlation functions in bulk systems, obtained in previous Integral Equation Theory (IET) studies. Extensive Molecular Dynamics (MD) simulations are employed to complement the DFT and IET predictions. Our DFT calculations incorporate electrostatic interactions between the ions using three different (existing) approaches: one is based on the simplest mean-field treatment of Coulomb interactions (MFC), while the other two employ the Mean Spherical Approximation (MSA). The MSAc invokes only the MSA bulk direct correlation function, whereas the MSAu also incorporates the MSA bulk internal energy. Although MSAu yields profiles that are in excellent agreement with MD simulations in the near field, in the far field, we observe that the decay lengths are consistent between IET, MSAc, and MD simulations, whereas those from MFC and MSAu deviate significantly. Using DFT, we calculated the solvation force, which relates directly to surface force experiments. We find that its decay length is neither qualitatively nor quantitatively close to the large decay lengths measured in experiments and conclude that the latter cannot be accounted for by the primitive model. The anomalously large decay lengths found in surface force measurements require an explanation that lies beyond primitive models.

Large time behaviour for the heat equation on [formula omitted], moments and decay rates

The paper is devoted to understand the large time behaviour and decay of the solution of the discrete heat equation in the one dimensional mesh Z on ℓp spaces, and its analogies with the continuous-space case. We do a deep study of the moments of the discrete gaussian kernel (which is given in terms of Bessel functions), in particular the mass conservation principle; that is reflected on the large time behaviour of solutions. We prove asymptotic pointwise and ℓp decay results for the fundamental solution. We use that estimates to get rates on the ℓp decay and large time behaviour of solutions. For the ℓ2 case, we get optimal decay by use of Fourier techniques.

Global small analytic solutions of MHD boundary layer equations

In this paper, we prove the global existence and the large time decay estimate of solutions to the two-dimensional MHD boundary layer equations with small initial data, which is analytical in the tangential variable. The main idea of the proof is motivated by that of [28]. The additional difficulties are: 1. There appears the magnetic field; 2. The far field here depends on the tangential variable; 3. The Reynolds number is different from magnetic Reynolds number. In particular, we solved an open question in [33] concerning the large time existence of analytical solutions to the MHD boundary layer equations.

Assessment of a confined thermal plume by PIV combined with POD analysis

A comprehensive understanding of the flow characteristics of thermal plumes during cooking is an essential prerequisite for designing high-performance cooker hoods. A cooking-related thermal plume under the confinement effect of a wall-mounted range hood in a real-sized kitchen is investigated utilizing particle image velocimetry. The experiment was conducted at Froude numbers ranging from 0.26 to 0.41 with different mounting heights (600 and 750 mm) and heating temperatures (100 and 260 °C). The plume behavior in the confined environment is described in the first section. The velocity profiles followed Gaussian functions well except at the impingement zone. In comparison with a thermal plume in a large space, the growth and decay rates of the velocity along the centerline were enhanced under a confined environment. The normalized velocity and temperature profiles along the centerline presented a clear confined height dependency and heating-temperature dependency. The turbulent intensity was relatively high in the zone near the heat source ((h0/h)z/D < 0.6) and impingement zone ((h0/h)z/D > 2.7). In addition, the distribution of skewness and kurtosis of the velocity fluctuations showed a Gaussian distributions in the zone of 0.4 < (h0/h)z/D < 2.7. Then, vortex and turbulence structures were examined utilizing vortex identification method and proper orthogonal decomposition (POD). The POD analysis visualization showed that the fluctuating energy for the development of plumes was dominated by the vertical velocity fluctuation. Finally, it was found that airflow rate profile of thermal plume follows a logarithmic function with height in the entrainment zone ((h0/h)z/D < 2.7).

Highly efficient carbazolylgold(iii) dendrimers based on thermally activated delayed fluorescence and their application in solution-processed organic light-emitting devices.

A new class of C^C^N ligand-containing carbazolylgold(iii) dendrimers has been designed and synthesized. High photoluminescence quantum yields of up to 82% in solid-state thin films and large radiative decay rate constants in the order of 105 s−1 are observed. These gold(iii) dendrimers are found to exhibit thermally activated delayed fluorescence (TADF), as supported by variable-temperature emission spectroscopy, time-resolved photoluminescence decay and computational studies. Solution-processed organic light-emitting diodes (OLEDs) based on these gold(iii) dendrimers have been fabricated, which exhibit a maximum current efficiency of 52.6 cd A−1, maximum external quantum efficiency of 15.8% and high power efficiency of 41.3 lm W−1. The operational stability of these OLEDs has also been recorded, with the devices based on zero- and second-generation dendrimers showing maximum half-lifetimes of 1305 and 322 h at 100 cd m−2, respectively, representing the first demonstration of operationally stable solution-processed OLEDs based on gold(iii) dendrimers.

Global well-posedness and large time decay for the d-dimensional tropical climate model

<abstract> This paper investigates the Cauchy problem on the d-dimensional tropical climate model with fractional hyperviscosity. We establish the small data global well-posedness of solutions to this model with supercritical dissipation. Furthermore, we study the asymptotic stability of these global solutions and obtain the optimal decay rates by using energy method and the method of bootstrapping argument. </abstract>