Unique Behavior Research Articles

The Effect of Design and Fabrication Parameters on the Mechanical Properties of 3D Re-Entrant Honeycomb Auxetic Structures

In recent years, the potential of application of auxetic structures, with negative Poisson's ratio, is gaining interest due to the increasingly widespread use of additive manufacturing. Additive technologies allow the manufacture of lightweight and complex shapes, and among them, auxetic cellular three-dimensional structures stand out for their unique behavior and with applications of interest in fields such as aerospace, medical or construction engineering. In the present work, 3D re-entrant honeycomb auxetic structures are designed and manufactured with Stereolithography (SLA) and Fused Filament Fabrication (FFF) with different geometrical parameters to analyse their impact in the mechanical behaviour of these complex structures. To this aim, an Ultimaker S5 and a Formlabs Form3 printer, respectively, have been used. Design variations are approached considering the following parameters: the length of the vertical strut (H), the length of the re-entrant strut (L), the re-entrant angle between the re-entrant and the vertical strut (θ) and the diameter of the struts cross sections (d). The designed structures shape behavior is evaluated with mechanical tests including compression tests and digital image correlation technique, and numerical simulations, The results show that lower Poisson ratio’s values are identified with slimmer profiles and with higher effective lengths and, therefore, corresponds to slender struts. On the other hand, lower angles between vertical and oblique struts show lower Poisson ratios, associated to the load distribution and its effect on the structure’s node displacements.

DVT: a high-throughput analysis pipeline for locomotion and social behavior in adult Drosophila melanogaster

BackgroundDrosophila melanogaster is excellent animal model for understanding the molecular basis of human neurological and motor disorders. The experimental conditions and chamber design varied between studies. Moreover, most previously established paradigms focus on fly trace detection algorithm development. A comprehensive understanding on how fly behaves in the chamber is still lacking.ResultsIn this report, we established 74 unique behavior metrics quantifying spatiotemporal characteristics of adult fly locomotion and social behaviors, of which 49 were newly proposed. By the aiding of the developed analysis pipeline, Drosophila video tracking (DVT), we identified siginificantly different patterns of fly behavior confronted with different chamber height, fly density, illumination and experimental time. Meanwhile, three fly strains which are widely used as control lines, Canton-S(CS), w1118 and Oregon-R (OR), were found to exhibit distinct motion explosiveness and exercise endurance.ConclusionsWe believe the proposed behavior metrics set and pipeline should help identify subtle spatial and temporal differences of drosophila behavior confronted with different environmental factors or gene variants.

Spatial Tuning of Light-Matter Interaction via Strain-Gradient-Induced Polarization in Freestanding Wrinkled 2D Materials.

To date, controlled deformation of two-dimensional (2D) materials has been extensively demonstrated with substrate-supported structures. However, interfacial effects arising from these supporting materials may suppress or alter the unique behavior of the deformed 2D materials. To address interfacial effects, we report, for the first time, the formation of a micrometer-scale freestanding wrinkled structure of 2D material without any encapsulation layers where we observed the enhanced light-matter interactions with a spatial modulation. Freestanding wrinkled monolayer WSe2 exhibited about a 330% enhancement relative to supported wrinkled WSe2 quantified through photoinduced force microscopy. Spatial modulation and enhancement of light interaction in the freestanding wrinkled structures are attributed to the enhanced strain-gradient effect (i.e., out-of-plane polarization) enabled by removing the constraining support and proximate dielectrics. Our findings offer an additional degree of freedom to modulate the out-of-plane polarization and enhance the out-of-plane light-matter interaction in 2D materials.

Gastric aggregation of micellar casein powders induced by high hydrostatic pressure: Effect of serum Ca2+ level

Micellar casein (MC) has a unique gastric colloidal behavior in response to Ca2+ cross-linking, and its aggregation properties are closely related to pepsin and gastric acid. In this study, MC with different levels of colloidal calcium phosphate (CCP) was obtained by high hydrostatic pressure (HHP) at different pressures, followed by spray drying to obtain the powders. Different amounts of calcium chloride (exogenous Ca2+) were added to MC powders prior to in vitro simulated digestion to investigate the effect of exogenous serum Ca2+ levels on the aggregation behavior and the structure change of curds generated in gastric tract. The results revealed that HHP induced the emergence of more Ca2+-binding sites, thus Ca2+ was more likely to bind to MC matrix with low CCP levels. Meanwhile, high serum Ca2+ level provided more opportunities to form aggregates. The Highest pressure (500 MPa) with the highest Ca2+ level (5 mM) caused the lowest solubility aggregates, which were only 30% at the end of gastric digestion (120 min), half of the control sample (0 MPa with 0.15 mM Ca2+). The results of wide-angle X-ray scattering / small-angle X-ray scattering suggested that both pepsin and gastric acid-induced aggregation via Ca2+ as a bridge. For pepsin, Ca2+ cross-linked between para-κ-casein; For gastric acid, Ca2+ recombined phosphorylation sites and caused cross-linking of casein subunits.

Employees' Perceptions of the Mediating Role of Dogmatic Customers in the Relationship Between Brand Trust and Marketing Inspiration

The general objective of this study is to identify the importance of the dogmatic customer as a mediating variable between trust in the brand to achieve marketing inspiration. Among the recent topics as an independent explanatory variable, marketing inspiration as a responding variable, and the dogmatic customer as a mediating variable between them, the analysis was carried out by adopting a set of statistical tools that are commensurate with the purpose of the study, and the two statistical package programs (Smart PLS) were adopted, and the research included a number of conclusions: that the dogmatic customer The great impact on the unique and introverted behavior and that his ideas that he received from his narrow knowledge society towards building marketing inspiration for organizations. The research presented a set of recommendations based on the results that were reached.

Controlled Radical Polymerization Initiated by Solvated Electrons.

Solvated electron (esol - ) is highly reducing species and apt to initiate monomers via one-electron transfer reaction. Herein, utilizing the esol - solution of Na/hexamethylphosphoramide, radical and anionic initiations are observed respectively, which heavily depend on Na concentrations. Interestingly, this initiation system, in states of lower Na concentrations, higher molar conductivities and less paired esol - , give rise to a controlled radical polymerization (CRP) to yield polymers with predictable molecular weights and narrow molecular weight distributions (the lowest Ð = 1.25). This CRP presents unique behaviors, like solvent effect, electric field effect, and unusual copolymerization phenomenon. A semi-conjugated radical carrying a negative charge is proposed to be responsible for the CRP. This system gives a distinct way to regulate CRP from current CRPs, and offers new insights into the monomer initiation by esol - .

Annihilation-gamma-based diagnostic techniques for magnetically confined electron–positron pair plasma

Efforts are underway to magnetically confine electron–positron pair plasmas to study their unique behaviour, which is characterized by significant changes in plasma time and length scales, supported waves and unstable modes. However, use of conventional plasma diagnostics presents challenges with these low-density and annihilating matter–antimatter plasmas. To address this problem, we propose to develop techniques based on the distinct emission provided by annihilation. This emission exhibits two spatial correlations: the distance attenuation of isotropic sources and the back-to-back propagation of momentum-preserving 2 $\gamma$ annihilation. We present the results of our analysis of the $\gamma$ emission rate and the spatial profile of the annihilation in a magnetized pair plasma from direct pair collisions, from the formation and decay of positronium as well as from transport processes. In order to demonstrate the effectiveness of annihilation-based techniques, we tested them on annular $\gamma$ emission profiles produced by a $\beta ^+$ radioisotope on a rotating turntable. Direct and positronium-mediated annihilation result in overlapping volumetric $\gamma$ sources, and the 2 $\gamma$ emission from these volumetric sources can be tomographically reconstructed from coincident counts in multiple detectors. Transport processes result in localized annihilation where field lines intersect walls, limiters or internal magnets. These localized sources can be identified by the fractional $\gamma$ counts on spatially distributed detectors.

Evaluation of Stress Distribution in Platform Switch Short Dental Placed at Different Depths in D1 bone – An in Vitro 3D FEM Study

Context: FEA has been extensively used in implant dentistry to predict the biomechanical behavior of various dental implant designs, as well as the effect of clinical factors for predicting clinical success. Stress patterns in implant components and surrounding bone are well studied. Objective: To investigate the pattern of stress distribution in terms of equicrestal and subcrestal implant placement at various depths using short platform switching dental implants. Materials and Methods: 3D FEM of the mandibular anterior area was modelled with a uniformly cortical bone of 0.5 mm with an inner core of cancellous bone (FEM) using ANYSIS soft wear. Four implant modes were used with the following dimensions. Model 1. (6x4.6x3.5mm), models 2 (7.5x4.6x3.5mm), 3 (6x5.8x4.5mm), and 4 (7.5x5.8x4.5mm). For a realistic simulation, 100N and 200N of force were applied in axial and oblique directions (0°, 15°, and 30°, respectively). At different depths, both cancellous and cortical bone is evaluated for von Mises stress. Ten-noded tetrahedron components with three degrees of freedom per node are used to interpret translations on the x, y, and z axes. Results: Based on bone shape, force direction, and depth of implant placement, each of the five positions of platform-switched short osseointegrated implants examined by FEM simulations had a unique stress-based biomechanical behavior. Conclusions: Axial forces were less harmful than oblique forces. The cortical and cancellous bone experienced less stress because of the implantation of subcrestal implants. According to recent research, platform-switched short subcrestal implant models result in improved stress distribution around peri implant areas in D1 bone and the conservation of marginal bone loss.

Structural Design and Aeromechanical Analysis of Unconventional Blades for Future Mars Rotorcraft

The structural design of rotor blades with ultra-thin, unconventional airfoils is conducted in support of the NASA Rotor Optimization for the Advancement of Mars eXploration (ROAMX) project. The outer mold line was provided by NASA, and the internal structural design was developed at the University of Maryland using a CAD-based three-dimensional (3D) aeromechanical analysis. The main objectives of this paper are to document the unique aeroelastic behavior encountered due to the low Reynolds number (down to 15K) and high subsonic Mach number (up to 0.95). Four different blade designs are considered, with the pitch axis varied from quarter-chord to midchord to determine the effect of center of gravity (C. G.) offset on natural frequencies, blade deformations, root loads, and 3D stresses. Torsional stability is emphasized for each of the designs - especially important due to the low Lock number on Mars. The designs are first studied in vacuum, and significant reductions in root loads and 3D stresses are achieved by moving the pitch axis closer to midchord to reduce the C. G. offset. Next, the design with the pitch axis at 40% chord is selected for a lifting-line aeromechanical analysis. The blade control load, airloads, deformations, and 3D stresses are studied for steady hover. Dynamic control load and dynamic 3D stresses are studied for unsteady hover. Interesting elastic twist is observed due to the trapeze effect and propeller moment, in turn affecting the spanwise distribution of aerodynamic loads. The dynamic control load is found to increase significantly due to inertial coupling from the C. G. offset. The dynamic stresses also increase but still have factors of safety greater than two for both tensile and compressive stress.

Cryogenic impact fracture behavior of a high-Mn austenitic steel using electron backscatter diffraction and neutron Bragg-edge transmission imaging

A unique impact fracture behavior is found in a high-Mn austenitic steel (24Mn–4Cr-0.4C-0.3Cu) in this work. The steel exhibits concurrent twinning-induced plasticity (TWIP) effect and the transformation-induced plasticity (TRIP) effect. By analyzing the load-deflection curves recorded during Charpy impact testing, the resistance to crack initiation and propagation is quantified from the absorbed energy. The high-Mn steel demonstrates good resistance to crack initiation at 273 K and 77 K. However, as the temperature decreases from 273 K to 77 K, there is an accelerated transition from stable crack growth to unstable crack growth during impact, resulting in the deterioration of resistance to crack propagation. The plastic deformation of the impact-tested samples, especially in the region close to the crack-path profile was quantitatively analyzed using neutron Bragg-edge transmission (BET) imaging. The deformation zones, divided by using the width of the 200 Bragg edge, exhibit good agreement with the impact absorbed energy characteristics obtained from dynamic load-deflection curves. Moreover, the unstable growth transition point was roughly determined on the impact-tested sample. Then, the electron backscatter diffraction (EBSD) technique is employed to examine the deformation microstructure along the crack-path in the impact-tested samples. The results revealed the dual roles of TRIP effect in impact toughness of the high-Mn steel. On one hand, the TRIP effect plays a positive role in improving resistance to crack initiation and propagation. On the other hand, the excessive accumulation of brittle ε/α՛-martensite caused by the enhanced TRIP effect at 77 K leads to quasi-cleavage fracture, thereby playing a negative role. Finally, we discussed the prominent toughening mechanisms associated with the TWIP and TRIP effects, which greatly impact the impact fracture behavior.

Polymer Networks with Cubic, Mixed Pd(II) and Pt(II) M6L12 Metal-Organic Cage Junctions: Synthesis and Stress Relaxation Behavior.

Metal-organic cages/polyhedra (MOCs) are versatile building blocks for advanced polymer networks with properties that synergistically blend those of traditional polymers and crystalline frameworks. Nevertheless, constructing polyMOCs from very stable Pt(II)-based MOCs or mixtures of metal ions such as Pd(II) and Pt(II) has not, to our knowledge, been demonstrated, nor has exploration of how the dynamics of metal-ligand exchange at the MOC level may impact bulk polyMOC energy dissipation. Here, we introduce a new class of polymer metal-organic cage (polyMOC) gels featuring polyethylene glycol (PEG) strands of varied length cross-linked through bis-pyridyl-carbazole-based M6L12 cubes, where M is Pd(II), Pt(II), or mixtures thereof. We show that, while polyMOCs with varied Pd(II) content have similar network structures, their average stress-relaxation rates are tunable over 3 orders of magnitude due to differences in Pd(II)- and Pt(II)-ligand exchange rates at the M6L12 junction level. Moreover, mixed-metal polyMOCs display relaxation times indicative of intrajunction cooperative interactions, which stands in contrast to previous materials based on point metal junctions. Altogether, this work (1) introduces a novel MOC architecture for polyMOC design, (2) shows that polyMOCs can be prepared from mixtures of Pd(II)/Pt(II), and (3) demonstrates that polyMOCs display unique relaxation behavior due to their multivalent junctions, offering a strategy for controlling polyMOC properties independently of their polymer components.

Characterization of recycled concrete aggregate (RCA) particles for geotechnical engineering applications: Particle strength and interparticle contact behavior

Construction waste is a global issue, with billions of tons being generated due to the demolition and renovation of old structures. Recycling and reusing surplus waste material is imperative, and recycled concrete aggregate (RCA) has emerged as a promising “earthen” material for geotechnical engineering applications, such as backfill, ballast, or foundation soil. The cement mortar coating and the complex composition of the RCA particles are hypothesized to result in unique interparticle contact behaviors; thus leading to the crushable nature and distinctive mechanical properties of RCA on the macro-scale. The current study examines a representative fraction (1.18–2.36 mm) of RCA particles from Nanjing, China (NJ) and Sydney, Australia (SYD), with a particular focus on particle strength and interparticle contact behavior. The characterization of the particles includes their composition, microstructure, and micro-indentation hardness, which influence their strength and interparticle contact behaviors. The study found that the overall strength of the RCA particles was significantly lower than that of typical quartz sands, and the particles were highly deformable. Notably, a ductile type of failure under compression was observed in 6% and 14% of the RCA particles from NJ and SYD, respectively, which is uncommon in other granular materials. The interparticle normal contact stiffness of RCA particles was comparable with highly decomposed tuff granules, placing it in the lower range of geomaterials. The removal of the surface cement mortar coating was found to increase the contact stiffness and surface microhardness markedly. Additionally, multi-cycles of normal loading enhanced the Young's modulus of the contact. These results provide useful insights into the mechanisms of the stiffness and strength of RCA, and can serve as valuable reference for improving mechanical properties of RCA in future applications.

Boron-doped copper phenylphosphate as temperature-response nanosheets to fabricate high fire-safety polycarbonate nanocomposites

The application of polymer materials has provided the convenience and also bring fire risk and hazard due to intrinsic flammable property of polymers. Here we demonstrate a novel strategy using boron-doped copper phenylphosphate (BCuPP) nanosheets with temperature-response characteristics as only flame retardant for creating high fire-safety polycarbonate (PC) nanocomposites with excellent comprehensive performances. PC/BCuPP nanocomposites presents a good mechanical performance at room temperature due to the strong interfacial interaction between PC matrix and BCuPP nanosheets. Furthermore, BCuPP exhibits unique temperature-response behavior driven by fire, where fully molten boron oxide flows freely, followed by in-situ formed BPO4 to repair the defects to form a complete and continuous protective layer. So the temperature-response behavior endows PC/BCuPP nanocomposites excellent fire-safety performance with dramatical decrease in both heat release rate and total smoke production. This study offers a novel route only incorporating nanoparticles as flame retardant to create high fire-safety polymer nanocomposites.

The eccentric Koza–Lidov mechanism as the cause of exocomet transits of KIC 8462852

ABSTRACT KIC 8462852 is a star in the Kepler field that exhibits almost unique behaviour. The deep, irregular, and aperiodic dips in its light curve have been interpreted as the breakup of a large exocomet on a highly eccentric orbit whose post-disruption material obscures the star. It is hypothesized that a nearby M-dwarf, recently confirmed to be bound to the system, could be exciting planetesimals in a source belt to high eccentricities if its orbit is highly misaligned with the belt: an effect known as the ‘Eccentric Kozai–Lidov Mechanism’. To quantify how often this effect is expected to occur, this paper presents a Monte Carlo model of wide binary stars with embedded, misaligned planetesimal belts. These belts collisionally erode over time until they are excited to high eccentricities on secular time-scales by a companion star if its orbit is sufficiently misaligned. The large planetesimals then produce an observable dimming signature in the light curve for a set period of time which may or may not overlap with similar events. The model finds that, for dimming events that persist for 100 yr, the most likely companion stars are located at 102−104 au, the most likely belts are at 102−103 au and the system age is most likely to be 102−103 Myr. However, the probability of observing one or more stars exhibiting this phenomenon in the Kepler field is 1.3 × 10−3, such that it is unlikely this mechanism is driving the observations of KIC 8462852.

Highly Uniform DNA Monolayers Generated by Freezing‐Directed Assembly on Gold Surfaces Enable Robust Electrochemical Sensing in Whole Blood

AbstractAssembling DNA on solid surfaces is fundamental to surface‐based DNA technology. However, precise control over DNA conformation and organization at solid–liquid interfaces remains a challenge, resulting in limited stability and sensitivity in biosensing applications. We herein communicate a simple and robust method for creating highly uniform DNA monolayers on gold surfaces by a freeze‐thawing process. Using Raman spectroscopy, fluorescent imaging, and square wave voltammetry, we demonstrate that thiolated DNA is concentrated and immobilized on gold surfaces with an upright conformation. Moreover, our results reveal that the freezing‐induced DNA surfaces are more uniform, leading to improved DNA stability and target recognition. Lastly, we demonstrate the successful detection of a model drug in undiluted whole blood while mitigating the effects of biofouling. Our work not only provides a simple approach to tailor the DNA‐gold surface for biosensors but also sheds light on the unique behavior of DNA oligonucleotides upon freezing on the liquid‐solid interface.

Highly Uniform DNA Monolayers Generated by Freezing-Directed Assembly on Gold Surfaces Enable Robust Electrochemical Sensing in Whole Blood.

Assembling DNA on solid surfaces is fundamental to surface-based DNA technology. However, precise control over DNA conformation and organization at solid-liquid interfaces remains a challenge, resulting in limited stability and sensitivity in biosensing applications. We herein communicate a simple and robust method for creating highly uniform DNA monolayers on gold surfaces by a freeze-thawing process. Using Raman spectroscopy, fluorescent imaging, and square wave voltammetry, we demonstrate that thiolated DNA is concentrated and immobilized on gold surfaces with an upright conformation. Moreover, our results reveal that the freezing-induced DNA surfaces are more uniform, leading to improved DNA stability and target recognition. Lastly, we demonstrate the successful detection of a model drug in undiluted whole blood while mitigating the effects of biofouling. Our work not only provides a simple approach to tailor the DNA-gold surface for biosensors but also sheds light on the unique behavior of DNA oligonucleotides upon freezing on the liquid-solid interface.

Effect of high-temperature thermo-oxidation on the mechanical and electrical properties of phenylethynyl-terminated polyimide/carbon fiber composite

The thermal degradation behaviors of phenylethynyl-terminated polyimide and their carbon fiber reinforced composites (CFRC) are significant to be evaluated comprehensively as their high-temperature applications are gradually expanded. It is found that ether-containing thermoset polyimide (PI) film shows unique degradation behaviors near glass transition temperature (Tg). Though the triethylamine (Et3N) chemical imidization method is applied, the PI backbone shows thermal stability at 371℃ thermo-oxidation condition and the main degradation parts site at the curing structure. More aliphatic (CC) linkages will be formed in the thermo-oxidation process and they are ascribed to the further crosslinking behaviors of polyene structure. However, the PI film shows stable mechanical properties after thermo-oxidation. Meanwhile, the formation of an amorphous carbon structure is found after thermo-oxidation treatment, which endows the composite with enhanced electrical properties. Though the micro-cracking phenomenon happens at the matrix/CF interface of composite surface and thus degrades its mechanical properties, the in-plane longitudinal and transverse conductivity of the composite perform an increase, factors of 1.13 to 2.56×104 S/m and 2.28 to 454.8 S/m, respectively. Mechanism study indicates that the formation of amorphous carbon components is caused by the structural rearrangement of the degrading polyene curing structure and becomes more in the thermo-oxidation process, not affecting the backbone integrity and mechanical stability of the PI matrix. As a result, thermo-oxidation treatment degrades the mechanical properties of the composite, whereas the formed amorphous carbon component acts as a self-growing carbon-based nano-filling structure at the PI/CF interface and enhances the electrical contact of the carbon fibers.

Surfactant-Promoted Prussian Blue Analogues Fabricated Electrodes for Electrocatalytic Water Oxidation

Prussian blue analogues (PBAs) have unique structural and chemical behaviour and therefore have applications in various fields of catalysis as energy conversion materials for storage devices and molecular sensing. Herein we focused on the in-situ synthesis of three PBAs comprising cobalt hexacyanoferrate (CoHCF), nicke<l hexacyanoferrate (NiHCF), and cobalt-nickel hexacyanoferrate (CoNiHCF) through cation i.e. cetyltrimethylammonium bromide (CTAB) assisted drop cast method. The electrocatalysts were characterized through a multitude of spectroscopic techniques and were tested for water oxidation study. It was found that among the three electrocatalysts, CoNiHCF showed comparatively better catalytic performance with an overpotential value of 570 mV (at 1 mA cm-2).

Good Practices and Practical Considerations for Research with Perfluoroalkyl Substances

AbstractPer‐ and polyfluoroalkyl substances (PFAS) are a class of hazardous pollutant that are ubiquitous in our modern world. Current research is driven by an increased awareness and concern regarding the safety of PFAS for the general population, while tightening regulations have prompted the need for detection and quantification techniques from a wide range of matrices. PFAS are a group of molecules offering unique behaviours, hazards, and complications that are not obvious or readily apparent from reading the literature. These peculiarities can impede or convolute analyses when not considered in experimental design. Drawing on the knowledge of a range of literature sources, this tutorial review looks to highlight and amalgamate the valuable suggestions and methodologies currently available to enable successful PFAS research in any laboratory.

Assessing the vulnerability of endangered and endemic brooding sea urchin Cassidulus mitis in response to climate change: Impacts on larvae and settlers in the southwestern Atlantic

Echinoderms play important roles in marine ecosystems and exhibit high sensitivity to environmental changes. The echinoid Cassidulus mitis has been considered an endangered species due to its restricted geographic distribution and unique reproductive behavior, with an epibenthic lecithotrophic larva and offspring brooded among the female spines during initial development until the settler stage. We studied the effects of low salinities (30 and 26) and high temperatures (27 and 31 °C) on the early development of C. mitis in a predicted scenario of global climate change through four parameters: 1. survival and 2. chronology of larval development, and 3. survival and 4. growth of settlers. Both larvae and settlers of C. mitis can survive under these scenarios, probably due to the lecithotrophic and epibenthic larval characteristics and developmental strategies of this species. However, all experimental conditions affected at least one of the initial developmental studied parameters of C. mitis, potentially compromising the species' viability in a scenario of climate change.