Global-scale interdecadal variability a skillful predictor at decadal-to-multidecadal timescales for Sahelian and Indian Monsoon Rainfall

In the present study, a sea surface temperature-based index named global-scale interdecadal variability (GIV) encompassing the combined variability of Atlantic multidecadal oscillation (AMO) and interdecadal Pacific oscillation (IPO) has been proposed. The warm phase of GIV exhibits a “cold AMO-like” pattern in the Atlantic basin and a “warm IPO-like” pattern in the Pacific basin. About 84% (R ~−0.914) of Sahelian and 42% (R ~−0.647) of Indian rainfall’s temporal variance is attributed to GIV, showing substantial improvement compared to the variance explained by AMO and IPO individually. The physical mechanism for GIV-rainfall teleconnection is related to a modification of the Walker circulation. Although there is a substantial degree of uncertainty in the current generation of state-of-the-art climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5), some still replicate the observed GIV’s spatial structure, its teleconnection, and associated physical mechanism. The results presented herein advance our knowledge about rainfall’s interdecadal variability and have imperative ramifications for developing skillful decadal predictions.

The Light Absorption Enhancement in Graphene Monolayer Resulting from the Diffraction Coupling of Surface Plasmon Polariton Resonance

In this study, we investigate a physical mechanism to improve the light absorption efficiency of graphene monolayer from the universal value of 2.3% to about 30% in the visible and near-infrared wavelength range. The physical mechanism is based on the diffraction coupling of surface plasmon polariton resonances in the periodic array of metal nanoparticles. Through the physical mechanism, the electric fields on the surface of graphene monolayer are considerably enhanced. Therefore, the light absorption efficiency of graphene monolayer is greatly improved. To further confirm the physical mechanism, we use an interaction model of double oscillators to explain the positions of the absorption peaks for different array periods. Furthermore, we discuss in detail the emerging conditions of the diffraction coupling of surface plasmon polariton resonances. The results will be beneficial for the design of graphene-based photoelectric devices.

On the Oval Shapes of Beach Stones

This article introduces a new stochastic non-isotropic frictional abrasion model, in the form of a single short partial integro-differential equation, to show how frictional abrasion alone of a stone on a planar beach might lead to the oval shapes observed empirically. The underlying idea in this theory is the intuitive observation that the rate of ablation at a point on the surface of the stone is proportional to the product of the curvature of the stone at that point and the likelihood the stone is in contact with the beach at that point. Specifically, key roles in this new model are played by both the random wave process and the global (non-local) shape of the stone, i.e., its shape away from the point of contact with the beach. The underlying physical mechanism for this process is the conversion of energy from the wave process into the potential energy of the stone. No closed-form or even asymptotic solution is known for the basic equation, which is both non-linear and non-local. On the other hand, preliminary numerical experiments are presented in both the deterministic continuous-time setting using standard curve-shortening algorithms and a stochastic discrete-time polyhedral-slicing setting using Monte Carlo simulation.

Dispersion Dynamics of Clustered Particles by Centrifugal Force

In this paper an approach is proposed to solve the problem of aggregation in nanomaterials through the mean of rotational separation aiming to quickly disperse clustered nanoparticles while not affecting their purity. If it is possible, this approach may replace the current mean of mechanical mixing, which may cause impurities issues. The hypothesis is that the centrifugal force due to rotational velocity acting on the nanoparticles can overcome the cohesive force between the nanoparticles, therefore dispersing the clustered nanoparticles. The experimental mean is to put different spheres connected by different types of glues imitating different nanoparticle clusters into centrifuges imitating the swivel plate. The results from both the theoretical model and the experiment show that for a cluster with a cohesive force of 1.75N, a rotational velocity of about 800rad./s is required to disperse the cluster. While for a cluster with a cohesive force of 0.25N and the same mass and position, a rotational velocity of about 150 rad./s is required to disperse the cluster. Except for the cohesive force, the mass and position of the nanoparticle on the swivel plate also have a large effect on the required rotational velocity. The observation of the physical mechanism of the dispersion has also shown that while using this way, the cluster is dispersed slowly with small parts separated from it. Therefore, this way can also eliminate re-clustering problems of nanoparticles.

Propagation of Thermohaline Anomalies and their predictive potential along the Atlantic water pathway

We assess to what extent seven state-of-the-art dynamical prediction systems can retrospectively predict winter sea surface temperature (SST) in the subpolar North Atlantic and the Nordic Seas in the period 1970-2005. We focus on the region where warm water flows poleward, i.e., the Atlantic water pathway to the Arctic, and on interannual-to-decadal time scales. Observational studies demonstrate predictability several years in advance in this region, but we find that SST skill is low with significant skill only at lead time 1-2 years. To better understand why the prediction systems have predictive skill or lack thereof, we assess the skill of the systems to reproduce a spatio-temporal SST pattern based on observations. The physical mechanism underlying this pattern is a propagation of oceanic anomalies from low to high latitudes along the major currents; the North Atlantic Current and the Norwegian Atlantic Current. We find that the prediction systems have difficulties in reproducing this pattern. To identify whether the misrepresentation is due to incorrect model physics, we assess the respective uninitialized historical simulations. These simulations also tend to misrepresent the spatio-temporal SST pattern, indicating that the physical mechanism is not properly simulated. However, the representation of the pattern is slightly degraded in the predictions compared to historical runs, which could be a result of initialization shocks and forecast drift effects. Ways to enhance predictions, could be through improved initialization, and better simulation of poleward circulation of anomalies. This might require model resolutions in which flow over complex bathymetry and physics of mesoscale ocean eddies and their interactions with the atmosphere are resolved.

The quantitative basis for the redistribution of immobile bacterial lipoproteins to division septa

The spatial localisation of proteins is critical for most cellular function. In bacteria, this is typically achieved through capture by established landmark proteins. However, this requires that the protein is diffusive on the appropriate timescale. It is therefore unknown how the localisation of effectively immobile proteins is achieved. Here, we investigate the localisation to the division site of the slowly diffusing lipoprotein Pal, which anchors the outer membrane to the cell wall of Gram-negative bacteria. While the proton motive force-linked TolQRAB system is known to be required for this repositioning, the underlying mechanism is unresolved, especially given the very low mobility of Pal. We present a quantitative, mathematical model for Pal relocalisation in which dissociation of TolB-Pal complexes, powered by the proton motive force across the inner membrane, leads to the net transport of Pal along the outer membrane and its deposition at the division septum. We fit the model to experimental measurements of protein mobility and successfully test its predictions experimentally against mutant phenotypes. Our model not only explains a key aspect of cell division in Gram-negative bacteria, but also presents a physical mechanism for the transport of low-mobility proteins that may be applicable to multi-membrane organelles, such as mitochondria and chloroplasts.

Robust Estimation Method Based on Function Model of Successive Approximation

In measurement practice, the residuals in least squares adjustment usually show various abnormal discrete distributions, including outliers, which is not conducive to the optimization of final measured values. Starting with the physical mechanism of dispersion and outlier of repeated observation errors, this paper puts forward the error correction idea of using the approximate function model of error to approach the actual function model of error step by step, gives a new theoretical method to optimize the final measured values, and proves the effectiveness of the algorithm by the ability of responding to the true values. This new idea is expected to be the ultimate answer of robust estimation theory.

Experimental Investigation on the Ranging Resolution of a FMCW Lidar

In some previous reports about frequency-modulated continuous-wave (FMCW) Lidar, observing the longer waveform of a de-chirped signal is considered an effective scheme for further improving the ranging resolution. In this work, the ranging resolution of a FMCW Lidar is experimentally investigated, and the feasibility of such a scheme is tested. During the experiment, a FMCW signal is generated via a Mach–Zehnder modulator in the transmitted port. In the received port, the de-chirped signal is extracted based on a homodyne detection scheme and is analyzed by an electrical spectrum analyzer. Two different methods are adopted to determine the ranging resolution. One is based on a single target, for which the ranging resolution is obtained through inspecting the shift of spectral peak position as the target moves. The other is based on two targets, for which the ranging resolution is acquired through inspecting the variation of spectrum distribution as the spacing of two targets changes. The experimental results demonstrate that extending the observed duration of the de-chirped signal cannot improve the ranging resolution, and the corresponding physical mechanism is revealed.

THEORETICAL SUBSTANTIATION OF THE PHYSICAL MECHANISM OF ULTRASONIC CAVITATION DESTRUCTION OF MACROMOLECULES

Многообещающее направление исследований, которое потенциально может служить базой для создания эффективной технологии управления свойствами полимеров – воздействие механическими колебательными возмущениями на высокомолекулярную среду. В реальных неотверждённых полимерах механические колебательные возмущения, как правило, представляют собой кавитационно-акустическое воздействие, т.е. линейные синусоидальные колебания, создаваемые в среде, инициируют вторичное явление – кавитационные пузырьки. Пузырьки при кавитационно-акустическом воздействии периодически расширяются и схлопываются, формируя микроударные волны. Таким образом, механические колебательные возмущения имеют две составляющие – линейная синусоидальная и нелинейная ударно-волновая. Основное воздействие на структуру полимеров оказывает ударно-волновая составляющая. Для реализации данного процесса с максимальной энергетической эффективностью необходимо выявить оптимальные режимы воздействия. Для выявления оптимальных режимов воздействия в статье теоретически обоснован физический механизм разрушения макромолекул, основанный на их соударении со скоростью, превышающей критическую за счёт формирования экстремальных условий по температуре и давлению в окрестности схлопывающегося кавитационного пузырька. A promising area of research that can potentially serve as a basis for creating an effective technology for controlling the properties of polymers is the effect of mechanical oscillatory disturbances on a high–molecular medium. In real uncured polymers, mechanical oscillatory disturbances, as a rule, represent a cavitation-acoustic effect, i.e. linear sinusoidal vibrations created in the medium initiate a secondary phenomenon - cavitation bubbles. Bubbles under cavitation-acoustic action periodically expand and collapse, forming micro-shock waves. Thus, mechanical oscillatory disturbances have two components – linear sinusoidal and nonlinear shock wave. The main effect on the structure of polymers has a shock-wave component. To implement this process with maximum energy efficiency, it is necessary to identify optimal exposure modes. In order to identify optimal exposure modes, the article theoretically substantiates the physical mechanism of destruction of macromolecules based on their collision with a velocity exceeding the critical one due to the formation of extreme conditions for temperature and pressure in the vicinity of a collapsing cavitation bubble.