The Photoinduced Response of Antimony from Femtoseconds to Minutes.

As a phase change material (PCM), antimony exhibits a set of desirable properties that make it an interesting candidate for photonic memory applications. These include a large optical contrast between crystalline and amorphous solid states over a wide wavelength range. Switching between the states is possible on nanosecond timescales by applying short heating pulses.

Stable Millivolt Range Resistive Switching in Percolating Molybdenum Nanoparticle Networks.

To overcome the limitations of the conventional Von Neumann architecture, inspiration from the mammalian brain has led to the development of nanoscale neuromorphic networks. In the present research, molybdenum nanoparticles (NPs), which were produced by means of gas phase condensation based on magnetron sputtering, are shown to be the constituents of electrically percolating networks that exhibit stable, complex, neuron-like spiking behavior at low potentials in the millivolt range, satisfying well the requirement of low energy consumption. Characterization of the NPs using both scanning electron microscopy and scanning transmission electron microscopy revealed not only pristine shape, size, and density control of Mo NPs but also a preliminary proof of the working mechanism behind the spiking behavior due to filament formations.

Allelochemicals determine competition and grazing control in Alexandrium catenella.

The production of allelochemicals by the toxigenic dinoflagellate Alexandrium catenella is one of the suggested mechanisms to facilitate its bloom formation and persistence by outcompeting other phototrophic protists and reducing grazing pressure. In Southern California, toxic events caused by A. catenella and paralytic shellfish toxins (PSTs) regularly impact coastal ecosystems; however, the trophic interactions and mechanisms promoting this species in a food web context are still not fully understood.

Growth mechanism of oleylammonium-based tin and lead bromide perovskite nanostructures.

Metal halide perovskites, particularly using tin and lead as bivalent cations, are well known for their synthetic versatility and ion mobility. These materials possess intriguing ionic properties that allow the formation of 2D Ruddlesden-Popper (RP) and 3D metal halide perovskite nanocrystals (NCs) under similar synthetic conditions. We studied the synthesis mechanism of oleylammonium-based Sn and Pb bromide perovskites 2D Ruddlesden-Popper (RP) in comparison with the 3D CsPbBr and CsSnBr NCs.

PbI Passivation of Three Dimensional PbS Quantum Dot Superlattices Toward Optoelectronic Metamaterials.

Lead chalcogenide colloidal quantum dots are one of the most promising materials to revolutionize the field of short-wavelength infrared optoelectronics due to their bandgap tunability and strong absorption. By self-assembling these quantum dots into ordered superlattices, mobilities approaching those of the bulk counterparts can be achieved while still retaining their original optical properties. The recent literature focused mostly on PbSe-based superlattices, but PbS quantum dots have several advantages, including higher stability.

Prey group defense and hunting cooperation among generalist-predators induce complex dynamics: a mathematical study.

Group defense in prey and hunting cooperation in predators are two important ecological phenomena and can occur concurrently. In this article, we consider cooperative hunting in generalist predators and group defense in prey under a mathematical framework to comprehend the enormous diversity the model could capture. To do so, we consider a modified Holling-Tanner model where we implement Holling type IV functional response to characterize grazing pattern of predators where prey species exhibit group defense.

Atomically Resolved Phase Coexistence in VO Thin Films.

Concurrent structural and electronic transformations in VO thin films are of 2-fold importance: enabling fine-tuning of the emergent electrical properties in functional devices, yet creating an intricate interfacial domain structure of transitional phases. Despite the importance of understanding the structure of VO thin films, a detailed real-space atomic structure analysis in which the oxygen atomic columns are also resolved is lacking. Moreover, intermediate atomic structures have remained elusive due to the lack of robust atomically resolved quantitative analysis.

Giant electrostriction-like response from defective non-ferroelectric epitaxial BaTiO integrated on Si (100).

Lead-free, silicon compatible materials showing large electromechanical responses comparable to, or better than conventional relaxor ferroelectrics, are desirable for various nanoelectromechanical devices and applications. Defect-engineered electrostriction has recently been gaining popularity to obtain enhanced electromechanical responses at sub 100 Hz frequencies. Here, we report record values of electrostrictive strain coefficients (M) at frequencies as large as 5 kHz (1.

Metavalent or Hypervalent Bonding: Is There a Chance for Reconciliation?

A family of solids including crystalline phase change materials such as GeTe and Sb Te , topological insulators like Bi Se and halide perovskites such as CsPbI possesses an unconventional property portfolio that seems incompatible with ionic, metallic, or covalent bonding. Instead, evidence is found for a bonding mechanism characterized by half-filled p-bands and a competition between electron localization and delocalization. Different bonding concepts have recently been suggested based on quantum chemical bonding descriptors which either define the bonds in these solids as electron-deficient (metavalent) or electron-rich (hypervalent).

Thick Does the Trick: Genesis of Ferroelectricity in 2D GeTe-Rich (GeTe) (Sb Te ) Lamellae.

The possibility to engineer (GeTe) (Sb Te ) phase-change materials to co-host ferroelectricity is extremely attractive. The combination of these functionalities holds great technological impact, potentially enabling the design of novel multifunctional devices. Here an experimental and theoretical study of epitaxial (GeTe) (Sb Te ) with GeTe-rich composition is presented.

Realizing avalanche criticality in neuromorphic networks on a 2D hBN platform.

Networks and systems which exhibit brain-like behavior can analyze information from intrinsically noisy and unstructured data with very low power consumption. Such characteristics arise due to the critical nature and complex interconnectivity of the brain and its neuronal network. We demonstrate a system comprising of multilayer hexagonal boron nitride (hBN) films contacted with silver (Ag), which can uniquely host two different self-assembled networks, which are self-organized at criticality (SOC).

3D Nanostructuring of Phase-Change Materials Using Focused Ion Beam toward Versatile Optoelectronics Applications.

In recent years, phase-change materials have gained importance in nanophotonics and optoelectronics. Sizable optical contrast and added degree of freedom from phase switching drive the use of phase-change materials in various optical devices with outstanding results and potential for real-world applications. The local crystallization/amorphization of phase-change materials and the corresponding reflectance tuning by the crystallized/amorphized region size have potential applications, for example, for future dynamic display devices.

Effects of Intermixing in SbTe/GeTe Multilayers on the Thermoelectric Power Factor.

Over the past few decades, telluride-based chalcogenide multilayers, such as PbSeTe/PbTe, BiTe/SbTe, and BiTe/BiSe, were shown to be promising high-performance thermoelectric films. However, the stability of performance in operating environments, in particular, influenced by intermixing of the sublayers, has been studied rarely. In the present work, the nanostructure, thermal stability, and thermoelectric power factor of SbTe/GeTe multilayers prepared by pulsed laser deposition are investigated by transmission electron microscopy and Seebeck coefficient/electrical conductivity measurements performed during thermal cycling.

The effect of biomolecular corona on adsorption onto and desorption from a model lipid membrane.

The current lack of insight into nanoparticle-cell membrane interactions hampers smart design strategies and thereby the development of effective nanodrugs. Quantitative and methodical approaches utilizing cell membrane models offer an opportunity to unravel particle-membrane interactions in a detailed manner under well controlled conditions. Here we use total internal reflection microscopy for real-time studies of the non-specific interactions between nanoparticles and a model cell membrane at 50 ms temporal resolution over a time course of several minutes.

Creating two-dimensional solid helium via diamond lattice confinement.

The universe abounds with solid helium in polymorphic forms. Therefore, exploring the allotropes of helium remains vital to our understanding of nature. However, it is challenging to produce, observe and utilize solid helium on the earth because high-pressure techniques are required to solidify helium.

Bridging Theories for Ecosystem Stability Through Structural Sensitivity Analysis of Ecological Models in Equilibrium.

Ecologists are challenged by the need to bridge and synthesize different approaches and theories to obtain a coherent understanding of ecosystems in a changing world. Both food web theory and regime shift theory shine light on mechanisms that confer stability to ecosystems, but from different angles. Empirical food web models are developed to analyze how equilibria in real multi-trophic ecosystems are shaped by species interactions, and often include linear functional response terms for simple estimation of interaction strengths from observations.

Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films.

Integration of the prototypical GeSbTe (GST) ternary alloys, especially on the GeTe-SbTe tie-line, into non-volatile memory and nanophotonic devices is a relatively mature field of study. Nevertheless, the search for the next best active material with outstanding properties is still ongoing. This search is relatively crucial for embedded memory applications where the crystallization temperature of the active material has to be higher to surpass the soldering threshold.

Structural Dynamics and Tunability for Colloidal Tin Halide Perovskite Nanostructures.

Lead halide perovskite nanocrystals are highly attractive for next-generation optoelectronics because they are easy to synthesize and offer great compositional and morphological tunability. However, the replacement of lead by tin for sustainability reasons is hampered by the unstable nature of Sn oxidation state and by an insufficient understanding of the chemical processes involved in the synthesis. Here, an optimized synthetic route is demonstrated to obtain stable, tunable, and monodisperse CsSnI nanocrystals, exhibiting well-defined excitonic peaks.

Thickness-Dependent Crystallization of Ultrathin Antimony Thin Films for Monatomic Multilevel Reflectance and Phase Change Memory Designs.

Phase change materials, with more than one reflectance and resistance states, have been a subject of interest in the fields of phase change memories and nanophotonics. Although most current research focuses on rather complex phase change alloys, , Ge2Sb2Te5, recently, monatomic antimony thin films have aroused a lot of interest. One prominent attractive feature is its simplicity, giving fewer reliability issues like segregation and phase separation.

Mathematical models for dengue fever epidemiology: A 10-year systematic review.

Mathematical models have a long history in epidemiological research, and as the COVID-19 pandemic progressed, research on mathematical modeling became imperative and very influential to understand the epidemiological dynamics of disease spreading. Mathematical models describing dengue fever epidemiological dynamics are found back from 1970. Dengue fever is a viral mosquito-borne infection caused by four antigenically related but distinct serotypes (DENV-1 to DENV-4).