Unique Behavior Research Articles

English

This paper reports details of phase transitions of a new generation “Tertiary Liquid Crystal System” (TLCS). This TLCS was made with a mixture of 5CB, 6CB, and 7CB liquid crystals. The TLCS was run in DSC to find changes taking place in its heat flow as a function of time and temperature analyzed with Logger Pro. The sample of TLCS was run from -40 °C to 80 °C with a 20 °C/min ramp rate in DSC. It was observed that the TLCS shows two phase transitions on heating and one transition on cooling. All these transitions were found to shift when compared to their single members. The unique behavior of TLCS is that it never shows crystallization in cooling, even though the sample was cooled to -40 °C. This indicated an increase in its Nematic range, making it more useful in the Liquid Crystal Display (LCD) field.

Fabrication of helix–fiber composites with mechanically coupled core-wrapping for programmable properties

Helix-fiber composites (HFCs), which involve wrapping a material around a flexible core, are of interest for intelligent stretchable functional materials or devices. Here, we reveal that mechanical coupling between the core and wrapping plays a critical role in controlling the structure and mechanical properties. Our results show that the mechanical properties of the HFC can be programmed by precisely tuning the mechanical coupling strength among them. Interestingly, the HFC also shows unique pseudo-elastic behavior under large strain due to the mechanical coupling effects. The HFC is demonstrated as an elastic metal conductor, programmable sensor, and finally as an elastic mold for structure transplantation by mechanically decoupling the elastomer core from the helix fiber. The results not only deepen the fundamental understanding of HFCs, but also may promote future structure-properties and fabrication studies on helix-structured functional composite and devices.

Non-associative learning behavior in mixed proton and electron conductor hybrid pseudo-diode

With inherent ionic priorities, mixed ion and electron conductor hybrid devices have been proposed for brain-inspired neuromorphic system applications, demonstrating interesting neuromorphic functions. Here, mixed proton and electron conductor (MPEC) hybrid oxide neuromorphic transistor is proposed by adopting aqueous solution-processed mesoporous silica coating (MSC)-based electrolyte as gate dielectric. With optical and electrical synergetic coupling behaviors, the device demonstrates typical synaptic responses and transition between short-term plasticity and long-term plasticity. With unique field-configurable proton self-modulation behaviors, a pseudo-diode operation mode is demonstrated on the MPEC hybrid transistor. Moreover, the device demonstrates interesting non-associative learning, including habituation and sensitization behavior. The results show that the proposed MPEC hybrid oxide neuromorphic transistor has great potential in the field of neuromorphic engineering and would have potential in the bionic visual perception platform.

Controlled drug delivery from chitosan-coated heparin-loaded nanopores anodically grown on nitinol shape-memory alloy

Nitinol (NiTi shape-memory alloy) is an interesting candidate in various medical applications like dental, orthopedic, and cardiovascular devices, owing to its unique mechanical behaviors and proper biocompatibility. The aim of this work is the local controlled delivery of a cardiovascular drug, heparin, loaded onto nitinol treated by electrochemical anodizing and chitosan coating. In this regard, the structure, wettability, drug release kinetics, and cell cytocompatibility of the specimens were analyzed in vitro. The two-stage anodizing process successfully developed a regular nanoporous layer of Ni-Ti-O on nitinol, which considerably decreased the sessile water contact angle and induced hydrophilicity. The application of the chitosan coatings controlled the release of heparin mainly by a diffusional mechanism, where the drug release mechanisms were evaluated by the Higuchi, first-order, zero-order, and Korsmeyer-Pepass models. Human umbilical cord endothelial cells (HUVECs) viability assay also showed the non-cytotoxicity of the samples, so that the best performance was found for the chitosan-coated samples. It is concluded that the designed drug delivery systems are promising for cardiovascular, particularly stent applications.

Control of chirality inversion kinetics of triple-helical metallocryptands

Abstract Dynamic helical molecules, which can undergo a reversible chirality inversion between the P and M forms, are useful as a platform for switchable chiral functional molecules. The chirality inversion of these molecules has been extensively studied. However, it has mostly been discussed from the viewpoint of the equilibrated P/M ratios before and after the inversion; control of the response speeds or kinetic profiles has rarely been explored. In order to construct helical structures with controllable kinetic profiles, triple-helical metallocryptands, LM3, have been designed and synthesized. These molecules can undergo a relatively slow dynamic P/M chirality inversion (helicity inversion) to produce an equilibrated mixture. The P/M equilibration was accelerated or decelerated based on the following two strategies. One is based on the guest binding in the cryptand cavity. The P/M racemization kinetics of LNi3 was significantly decelerated by recognition of guanidinium ion in the cavity. The other strategy is based on the ligand exchange reactions at the octahedral cobalt(III) centers in LCo3(amine)6. The P/M chirality inversion speeds were controlled by changing the initial and entering amine ligands. In addition, a unique transient chirality inversion behavior was observed when chiral amine ligands were removed from the metallocryptand by the ligand exchange reaction with piperidine.

Switchable Xe/Kr Selectivity in a Hofmann-Type Metal-Organic Framework via Temperature-Responsive Rotational Dynamics.

The development of adsorbents for Kr and Xe separation is essential to meet industrial demands and for energy conservation. Although a number of previous studies have focused on Xe-selective adsorbents, stimuli-responsive Xe/Kr-selective adsorbents still remain underdeveloped. Herein, a Hofmann-type framework Co(DABCO)[Ni(CN)4 ] (referred to as CoNi-DAB; DABCO = 1,4-diazabicyclo[2,2,2]octane) that provides a temperature-dependent switchable Xe/Kr separation performance is reported. CoNi-DAB showed high Kr/Xe (0.8/0.2) selectivity with significant Kr adsorption at 195K as well as high Xe/Kr (0.2/0.8) selectivity with superior Xe adsorption at 298K. Such adsorption features are associated with the temperature-dependent rotational configuration of the DABCO ligand, which affects the kinetic gate-opening temperature of Xe and Kr. The packing densities of Xe (2.886gcm-3 at 298K) and Kr (2.399g cm-3 at 195K) inside the framework are remarkable and comparable with those of liquid Xe (3.057gcm-3 ) and liquid Kr (2.413gcm-3 ), respectively. Breakthrough experiments confirm the temperature-dependent reverse separation performance of CoNi-DAB at 298K under dry and wet (88% relative humidity) conditions and at 195K under dry conditions. The unique adsorption behavior is also verified through van der Waals (vdW)-corrected density functional theory (DFT)calculations and nudged elastic band (NEB) simulations.

Investigation of the Mechanism of Powder Pool Coupled Activating TIG Welding

As a highly effective welding method, PPCA-TIG (Powder Pool Coupled Activating Flux–Tungsten Inert Gas) welding aims to achieve automated activation of TIG welding through the use of suitable activating fluxes. However, due to the unique transitional behavior of activating elements, the mechanism of PPCA-TIG is a little bit different from common activating TIG welding. In this research, a two-dimensional model is established to investigate the effect of four activating fluxes (TiO2, SiO2, MnO2, CaF2) on arc morphology and force. A series of welding experiments is performed to study the impact of the different activating elements on the molten pool. The results show that the increase in the penetration of TiO2 is related to the high arc temperature and great arc force and electromagnetic force in the molten pool. The problem of the softening of 3003 aluminum alloy welded joints is solved. Other activating fluxes are less effective than TiO2. The addition of calcium fluoride significantly affects penetration. The use of TiO2, SiO2 and MnO2 changes the molten pool viscosity and affects the molten pool oscillation, thus affecting the weld quality.

Identifying the unique behaviors embedded in the process of interprofessional collaboration in the ICU

ABSTRACT Interprofessional collaboration (IPC) is an important aspect of high-quality care in intensive care units (ICUs). The practice of IPC, however, is complex and the components that constitute IPC are not well defined. We sought to identify distinct behaviors embedded in clinician workflow that indicate engagement in the IPC process. We conducted a clinical ethnography in two ICUs in southeastern Michigan. From March 2017 to March 2019, we collected 31 hours of observations and completed 12 separate clinician shadowings and 12 interviews with ICU nurses, physicians, and respiratory therapists. We applied an iterative analytical approach to identify two types of IPC behaviors which we a priori labeled as “enablers” (i.e. the ways clinicians transition into or facilitate collaboration) and “collaborative activities” (i.e. behaviors clinicians use to directly collaborate with other professionals). 18 IPC behaviors were identified – ten “enablers” and eight “collaborative activities.” Specifically, the enablers include: active listening, approach, coordinating work, intraprofessional consultation, invitation, nonverbal accessibility, reflexive questioning, sending pages/call, validation, and verbal accessibility. The collaborative activities are: correction, fill in the gap, information exchange, negotiation, providing help, socializing, teaching/training, and troubleshooting. By identifying IPC behaviors embedded in clinician workflow, our results may support more focused assessments of IPC in practice and guide clinicians toward behaviors they can use to engage in the IPC process.

Investigation on the dynamic behaviors of single surface CO nanobubbles during CO2 electroreduction in ionic liquids

CO nanobubbles generated on the electrode surface affects inevitably the reaction performance during the electroreduction of CO2. Understanding the dynamic behaviors of single surface CO nanobubbles, especially on the onset stage (i.e., nanobubble nucleation), has been received wide attentions in recent years. However, it is a great challenge to detect the nanobubble nucleation and evolution behaviors in-situ due to the transitory and nanoscale nature of nanobubble. In this work, for the first time, a single-entity electrochemistry method was developed to generate the single CO nanobubbles exclusively and stably in ionic liquids (ILs) by CO2 electroreduction. The unique dynamic behaviors of CO nanobubble and special regulations were revealed by the recorded voltammograms, where the critical supersaturation and the energy barrier for the CO nanobubble nucleation are much lower than that of other gases in aqueous solutions, thus CO nanobubbles are easy formed in ILs systems. It is proved through the classic nucleation theory that the main control factor of CO nanobubble nucleation is the relatively low surface free energy in ILs systems. Furthermore, experiments and simulations simultaneously revealed that the nanoelectrode surface is partially covered by the CO nanobubble due to the slower reaction kinetics instead of CO2 diffusion rate. The insights gained have relevant implications in regulating the behavior of nanobubbles as well as the performance of CO2 electroreduction to CO.

Structural Characteristics of Reaction Tissue in Plants.

To maintain or adjust posture under the challenges of gravity and increased self-weight, or the effects of light, snow, and slope, plants have the ability to develop a special type of tissue called reaction tissue. The formation of reaction tissue is a result of plant evolution and adaptation. The identification and study of plant reaction tissue are of great significance for understanding the systematics and evolution of plants, the processing and utilization of plant-based materials, and the exploration of new biomimetic materials and biological templates. Trees' reaction tissues have been studied for many years, and recently, many new findings regarding these tissues have been reported. However, reaction tissue requires further detailed exploration, particularly due to their complex and diverse nature. Moreover, the reaction tissues in gymnosperms, vines, herbs, etc., which display unique biomechanical behavior, have also garnered the attention of research. After summarizing the existing literature, this paper provides an outline of the reaction tissues in woody plants and non-woody plants, and lays emphasis on alternations in the cell wall structure of the xylem in softwood and hardwood. The purpose of this paper is to provide a reference for the further exploration and study of reaction tissues with great diversity.

Light-Induced Bipolar Photoresponse with Amplified Photocurrents in an Electrolyte-Assisted Bipolar p-n Junction.

The p-n junction with bipolar characteristics sets the fundamental unit to build electronics while its unique rectification behavior constrains the degree of carrier tunability for expanded functionalities. Herein, a bipolar-junction photoelectrode employed with a gallium nitride (GaN) p-n homojunction nanowire array that operates in electrolyte is reported, demonstrating bipolar photoresponse controlled by different wavelengths of light. Significantly, with rational decoration of a ruthenium oxides (RuOx ) layer on nanowires guided by theoretical modeling, the resulting RuOx /p-n GaN photoelectrode exhibits unambiguously boosted bipolar photoresponse by an enhancement of 775% and 3000% for positive and negative photocurrents, respectively, compared to the pristine nanowires. The loading of the RuOx layer on nanowire surface optimizes surface band bending, which facilitates charge transfer across the GaN/electrolyte interface, meanwhile promoting the efficiency of redox reaction for both hydrogen evolution reaction and oxygen evolution reaction which corresponds to the negative and positive photocurrents, respectively. Finally, a dual-channel optical communication system incorporated with such photoelectrode is constructed with using only one photoelectrode to decode dual-band signals with encrypted property. The proposed bipolar device architecture presents a viable route to manipulate the carrier dynamics for the development of a plethora of multifunctional optoelectronic devices for future sensing, communication, and imaging systems.

Microencapsulated paraffin as a tribological additive for advanced polymeric coatings

Numerous tribological applications, wherein the use of liquid lubricants is infeasible, require adequate dry lubrication. Despite the use of polymers as an effective solution for dry sliding tribological applications, their poor wear resistance prevents the utilization in harsh industrial environment. Different methods are typically implemented to tackle the poor wear performance of polymers, however sacrificing some of their mechanical/tribological properties. Herein, we discussed the introduction of a novel additive, namely microencapsulated phase change material (MPCM) into an advanced polymeric coating. Specifically, paraffin was encapsulated into melamine-based resin, and the capsules were dispersed in an aromatic thermosetting co-polyester (ATSP) coating. We found that the MPCM-filled composite exhibited a unique tribological behavior, manifested as “zero wear”, and a super-low coefficient of friction (COF) of 0.05. The developed composite outperformed the state-of-the-art polytetrafluoroethylene (PTFE)-filled coatings, under the experimental conditions examined herein.

Competitive inhibition of a non-natural cofactor dependent formaldehyde dehydrogenase by imidazole.

To better understand the unique inhibitory behavior of a non-natural cofactor preferred formaldehyde dehydrogenase (FalDH) mutant 9B2. We described our serendipitous observation that 9B2 was reversibly inhibited by residual imidazole introduced during protein preparation, while the wild-type enzyme was not sensitive to imidazole. Kinetic analysis showed that imidazole was a competitive inhibitor of formaldehyde with a Ki of 16 μM and an uncompetitive inhibitor of Nicotinamide Cytosine Dinucleotide for 9B2, indicating that formaldehyde and imidazole were combined in the same position. Molecular docking results of 9B2 showed that imidazole could favorably bind very close to the nicotinamide moiety of the cofactor, where formaldehyde was expected to reside for catalysis, which was in line with a competitive inhibition. The mutant 9B2 can be competitively inhibited by imidazole, suggesting that cautions should be taken to evaluate activities as protein mutants might attain unexpected sensitivity to a component in buffers for purification or activity assays.

Capillary Assembly of Anisotropic Particles at Cylindrical Fluid-Fluid Interfaces.

The unique behavior of colloids at liquid interfaces provides exciting opportunities for engineering the assembly of colloidal particles into functional materials. The deformable nature of fluid-fluid interfaces means that we can use the interfacial curvature, in addition to particle properties, to direct self-assembly. To this end, we use a finite element method (Surface Evolver) to study the self-assembly of rod-shaped particles adsorbed at a simple curved fluid-fluid interface formed by a sessile liquid drop with cylindrical geometry. Specifically, we study the self-assembly of single and multiple rods as a function of drop curvature and particle properties such as shape (ellipsoid, cylinder, and spherocylinder), contact angle, aspect ratio, and chemical heterogeneity (homogeneous and triblock patchy). We find that the curved interface allows us to effectively control the orientation of the rods, allowing us to achieve parallel, perpendicular, or novel obliquely orientations with respect to the cylindrical drop. In addition, by tuning particle properties to achieve parallel alignment of the rods, we show that the cylindrical drop geometry favors tip-to-tip assembly of the rods, not just for cylinders, but also for ellipsoids and triblock patchy rods. Finally, for triblock patchy rods with larger contact line undulations, we can achieve strong spatial confinement of the rods transverse to the cylindrical drop due to the capillary repulsion between the contact line undulations of the particle and the pinned contact lines of the sessile drop. Our capillary assembly method allows us to manipulate the configuration of single and multiple rod-like particles and therefore offers a facile strategy for organizing such particles into useful functional materials.

Dynamic analysis of a tunable electromagnetic bistable system

Bistable structures exhibit a unique snap-through behaviour, which is widely used in different engineering disciplines. Some bistable systems have the ability to change dynamic characteristics such as the depth of the potential wells, distribution of the stable equilibrium points, and symmetry of the potential function, but only for the initial assembly. Therefore, this study presents a novel tunable electromagnetic bistable system (EBS), which can be adjusted online. An EBS is composed of a mechanical spring and an electromagnetic negative-stiffness unit in parallel. To characterise such a system, a static model was developed using the filament method, and the dynamic response was calculated using the harmonic balance method to better understand the EBS tunability. We conducted a series of studies aimed at revealing the effects of the geometric parameters, initial conditions, and excitation level on the dynamic characteristics. Finally, a switch between the interwell and intrawell oscillations of the actively tunable EBS was experimentally demonstrated, improving applications such as adaptive energy harvesting and active vibration control.

Surface morphology and cell viability of samarium (III) oxide/chromium (III) oxide/graphene oxide/polycaprolactone targeting wound dressing

Combinations of metal and lanthanide oxides have been done through casted films for potential medical applications. In this regard, samarium (III) oxide/chromium (III) oxide/graphene oxide (GO)/polycaprolactone (PCL) based films nano-composites (NCs) were fabricated, pointing their utilization as a biological scaffold for wound dressing purposes. Also, samarium (III) oxide and chromium (III) oxide have been merged as promising optical constituents due to their unique optical behavior. The structural and compositional examination of the studied NCs was executed by X-ray diffraction (XRD), Raman, and field emission scanning electron microscopy (FESEM). The Sm2O3/Cr2O3/GO/PCL NC exhibits a surface with a lower roughness degree owing to the presence of GO. Cr2O3 shows size reduction upon GO insertion to reach 1.2 μm as the average grain size, whilst Sm2O3 records an average grain size of less than 1 μm. As well, the polymeric nano-compositions exhibit variation in contact angle values that hit 29.76° ± 3.52° for Sm2O3/PCL, and 48.62° ± 1.37° for Sm2O3/Cr2O3/GO/PCL as the second lowest contact angle. The optical behavior contributes to absorption edge relocation along the x-axis from 1.7 eV for pure PCL, to 2.65 eV for Sm2O3/Cr2O3/GO/PCL. Regarding biological responses, the cell exposed to 2.5 μg/mL of Sm2O3/Cr2O3/GO/PCL shows cell viability of 119.31%, while 5 μg/mL hits 99.6%. Additionally, the resulting cell attachment micrographs show layers of fibroblast tissue, besides the proliferation and growth of cultivated cells. Thus, the Sm2O3/Cr2O3/GO/PCL scaffold provides 3D proliferation of fibroblast cells endorsing the wound healing process.

Electroreduction of CO2 in a Non-aqueous Electrolyte-The Generic Role of Acetonitrile.

Transition metal carbides, especially Mo2C, are praised to be efficient electrocatalysts to reduce CO2 to valuable hydrocarbons. However, on Mo2C in an aqueous electrolyte, exclusively the competing hydrogen evolution reaction takes place, and this discrepancy to theory was traced back to the formation of a thin oxide layer at the electrode surface. Here, we study the CO2 reduction activity at Mo2C in a non-aqueous electrolyte to avoid such passivation and to determine products and the CO2 reduction reaction pathway. We find a tendency of CO2 to reduce to carbon monoxide. This process is inevitably coupled with the decomposition of acetonitrile to a 3-aminocrotonitrile anion. Furthermore, a unique behavior of the non-aqueous acetonitrile electrolyte is found, where the electrolyte, instead of the electrocatalyst, governs the catalytic selectivity of the CO2 reduction. This is evidenced by in situ electrochemical infrared spectroscopy on different electrocatalysts as well as by density functional theory calculations.

Function of environment-derived male perfumes in orchid bees

Perfume making in male orchid bees is a unique behavior that has given rise to an entire pollination syndrome in the neotropics.1,2 Male orchid bees concoct and store species-specific perfume mixtures in specialized hind-leg pockets3 using volatiles acquired from multiple environmental sources, including orchid flowers.4,5 However, the function and the ultimate causes of this behavior have remained elusive.2,6 Although previous observations suggested that male perfumes serve as chemical signals, the attractiveness for females has not be shown.7,8 Here, we demonstrate that the possession of perfume increases male mating success and paternity in Euglossa dilemma, a species of orchid bees recently naturalized in Florida. We supplemented males reared from trap-nests with perfume loads harvested from wild conspecifics. In dual-choice experiments, males supplemented with perfumes mated with more females, and sired more offspring, than untreated, equal-aged, control males. Although perfume supplementation had little effect on the intensity of male courtship display, it changed the dynamics of male-male interactions. Our results demonstrate that male-acquired perfumes are sexual signals that stimulate females for mating and suggest that sexual selection is key in shaping the evolution of perfume communication in orchid bees.

Foraging distances, habitat preferences and seasonal colony performance of honeybees in Central European forest landscapes

Abstract Unmanaged forest is considered as native habitat of the Western honeybee Apis mellifera and is assumed to provide important pollen and nectar sources. However, resource supply might be spatially and temporally restricted in managed forests and landscape‐scale studies in European forest regions are currently lacking. Capitalizing on a unique communication behaviour, the waggle dance, we investigated honeybee foraging in a deciduous forest region in southern Germany. We analysed 2022 waggle dances performed by bees of 12 colonies placed in the centre of landscapes with varying degree of forest cover (50%–99% at a 2‐km radius) from March to August 2019, thereby identifying foraging distances and habitat preferences over almost an entire foraging season. By connecting dance information with colony weight recordings, we assessed the role of landscape composition and the contribution of different habitat types to colony weight gain. Foraging distances generally increased with the amount of forest in the surrounding landscape pointing to inferior food resources in the forest. Yet, this effect strongly depended on the season and was more pronounced for pollen than for nectar foraging. Even though colonies in forest‐dominated landscapes had to fly further, colony weight was not significantly affected by forest cover. Compared to expectations based on the proportions of different habitats, colonies foraged more frequently in grassland and cropland than in deciduous and coniferous forests, with late summer being an especially difficult period for pollen foraging in forests. During a phase of colony weight gain in early summer, the use of forests for nectar/honeydew foraging was close to the expectation, highlighting forests as an important complementary source of carbohydrates during short periods of the year. Policy implication. The ecological and economic value of managed forest as habitat for honeybees could be significantly increased by the continuous provision of floral resources, especially for pollen foraging. Therefore, we recommend diversifying forest stands with insect‐pollinated trees, permitting secondary successions in forest gaps, and at larger scales, creating forest landscapes with high habitat diversity. This will not only help native, wild‐living honeybees and beekeepers' colonies residing in forest areas but will also foster social bees in general.

Accurate Measurements and Simulations of the Evaporation and Trajectories of Individual Solution Droplets

A refined numerical model for the evaporation and transport of droplets of binary solutions is introduced. Benchmarking is performed against other models found in the literature and experimental measurements of both electrodynamically trapped and freefalling droplets. The model presented represents the microphysical behavior of solutions droplets in the continuum and transition regimes, accounting for the unique hygroscopic behavior of different solutions, including the Fuchs-Sutugin and Cunningham slip correction factors, and accounting for the Kelvin effect. Simulations of pure water evaporation are experimentally validated for temperatures between 290 K and 298 K and between relative humidity values of approximately 0% and 85%. Measurements and simulations of the spatial trajectories and evaporative behavior of aqueous sodium chloride droplets are compared for relative humidity values between 0 and 40%. Simulations are shown to represent experimental data within experimental uncertainty in initial conditions. Calculations of a time-dependent Péclet number, including the temperature dependence of solute diffusion, are related to morphologies of sodium chloride particles dried at different rates. For sodium chloride solutions, dried particles are composed of collections of reproducibly shaped crystals, with higher evaporation rates resulting in higher numbers of crystals, which are smaller.