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Modern demands for efficient, environmentally friendly, and self-powered devices have led to growing interest in piezoelectric polymers in the scientific community. In this paper, a ZIF-67 functionalized polyvinylidene fluoride/ tetrabutylammonium hexafluorophosphate tree-like nanofiber membrane (ZIF-67@PVDF/TBAHP-TLNMs) was developed as piezoelectric nanogenerator for energy harvesting. The ZIF-67@PVDF/TBAHP-TLNMs was prepared by in-situ growth of ZIF-67 on the surface of PVDF TLNMs, which demonstrated remarkable energy harvesting capabilities. The results indicated that the β-phase content of the in-situ growth of ZIF-67 reached 86.94 %, augmented the fiber's rotation radius, and elevated the electromechanical conversion efficiency. Notably, the short circuit current reached 3.87 μA and the output voltage exceeded 9.78 V, which was 10.7 times and 5.9 times higher than the electrical signal output of pure PVDF nanofiber membrane, respectively. Furthermore, the ZIF-67@PVDF/TBAHP-TLNMs exhibited exceptional mechanical properties, with an elastic modulus as high as 1.13 GPa, outperforming other nanofiber membranes and catering to the diverse requirements of wearable devices. During a 500 s test cycle, its layered structure remained intact, without any discernible damage or interlayer separation of the nanofibers. At the same time, the device exhibited high electromechanical conversion efficiency and a sensitive sensing function, which made it have broad application prospects in human motion monitoring and intelligent wearable devices. [Display omitted] [ABSTRACT FROM AUTHOR]

To have a uniform distribution of reactants is an advantage to a fuel cell. We report results for such a distributor with tree-like flow field plates (FFP). Numerical simulations have shown that the width scaling parameters of tree-like patterns in FFPs used in polymer electrolyte membrane fuel cells (PEMFC) reduces the viscous dissipation in the channels. In this study, experimental investigations were conducted on a 2-layer FF plate possessing a tree-like FF pattern which was CNC milled on high-quality graphite. Three FF designs of different width scaling parameters were employed. I–V curves, power curves and impedance spectra were generated at 70%, 60% and 50% relative humidity (25 cm2 active area), and compared to those obtained from a conventional 1-channel serpentine FF. It was found that the FF design, with a width scaling factor of 0.917 in the inlet and 0.925 in the outlet pattern, exhibited the best peak power out of the three designs (only 11% - 0.08 W/cm2 lower than reference serpentine FF). Results showed that a reduction of the viscous dissipation in the flow pattern was not directly linked to a PEMFC performance increase. It was found that water accumulation, together with a slight increase in single PEMFC resistance, were the main reasons for the reduced power density. As further improvements, a reduction of the number of branching generation levels and width scaling factor were recommended. Experimental analysis of width scaling factors in tree-like flow field patterns for polymer electrolyte membrane fuel cells. [Display omitted] • New PEMFC flow field (FF) designs were developed and tested. • Experimental analysis of width-scaling parameters in tree-like FF patterns. • Best design led to PEMFC performances within 11% of a standard serpentine pattern. • A decrease in FF width-scaling parameters led to improved PEMFC performance. • Water removal issue was found to be the largest contributor to lower power output. [ABSTRACT FROM AUTHOR]

The study took place at the Experimental Station of Pastures and Forages to evaluate the effect of the cut frequency (45 and 60 days) on forage yields of Moringa oleifera ecotypes Nicaragua and Criolla, with irrigation and organic fertilization, on fluvisol, in the Cauto Valley. A randomized block design with 2x2 factorial design and four replicas was used. The plants were cut 10 cm high from the ground, and variables plant height, shoot amount and thickness, number of leaves, leaf/stem ratio, total dry matter (DM) yields, and dry leaves and stems, were determined. Except for the number of shoots, all the variables were significant for the cutting frequency (P < 0.001). The number of leaves was the only variable with a difference for the ecotype factor (P < 0.05). The highest yields in total dry matter were achieved at 60 days (3.8 t.ha-1). However, the experiment only lasted 180 days with gradual reduction in production, caused by the competition between M. oleifera and invading graminaceae. The study concluded that the cutting frequency of 60 days produced increased yields of DM. However, the cutting height favored the presence of invading plants, with decreasing yields and sustainability of forage production.

Abstract A hierarchical MnO x @polyvinylidene fluoride (PVDF)/multiwalled carbon nanotubes (MWCNTs) tree-like nanofiber membrane (TLNM) was developed for dye degradation under natural sunlight irradiations, which was prepared by in situ hydrothermal growth of MnO x nanoflakes on the electrospun PVDF/tetrabutylammonium chloride (TBAC)/MWCNTs TLNM. The specific surface area of the MnO x @PVDF/MWCNTs composite catalyst was significantly enhanced by the tree-like structure and MnO x nanoflakes and the catalyst presented good absorption of both ultraviolet light and visible light. Noticeably, the MnO x @PVDF/MWCNTs TLNM exhibited excellent catalytic activity for several different dyes under sunlight and even in the dark condition. Electron spin resonance (ESR) technology and reactive oxidative species scavenging experiments demonstrated that superoxide radicals (O 2 −) was the major active ingredient during catalytic degradation process. More importantly, the capacity of manganese with three oxidation states (II/III/IV) could massively enhance the electron transfer and the synergistic oxidation of O 2 − and Mn(IV) accelerated the degradation of dyes. Meanwhile, MWCNTs act as electron transfer channels which could effectively facilitate the catalytic efficiency. This study will supply a new scheme for construction of new catalysts with enhanced catalytic activity in pollutant degradation under both sunlight and dark conditions. Graphical abstract Image 1 Highlights • A hierarchical MnO x @PVDF/MWCNTs tree-like nanofiber membrane was fabricated. • The catalyst showed excellent catalytic performance under both sunlight and dark. • The synergistic oxidation of Mn(Ⅳ) and O 2 − accelerated the degradation of dyes. • MWCNTs could serve as electron transfer channels and enhance catalytic activity. [ABSTRACT FROM AUTHOR]

The study took place at the Experimental Station of Pastures and Forages to evaluate the effect of the cutting frequency (45 and 60 days) on forage yields of Moringa oleifera ecotypes Nicaragua and Criolla, with irrigation and organic fertilization, on fluvisol, on the Cauto Valley. A randomized block design with 2x2 factorial design and four replicas was used. The plants were cut 10 cm from the ground, and variables plant height, shoot amount and thickness, number of leaves, leaf/stem ratio, total dry matter (DM) yields, and dry leaves and stems, were determined. Except for the number of shoots, all the variables were significant for the cutting frequency (P < 0.001). The number of leaves was the only variable with a difference for the ecotype factor (P < 0.05). The greatest yields in total dry matter were achieved at 60 days (3.8 t.ha-1). However, the experiment only lasted 180 days with gradual reduction in production, caused by the competition between M. oleifera and invading graminaceae. The study concluded that the cutting frequency of 60 days produced increased yields of DM. However, the cutting height favored the presence of invading plants, with decreasing yields and sustainability of forage production. [ABSTRACT FROM AUTHOR]

A smart tree-like nanofiber membrane with pH-responsivity was successfully fabricated by electrospinning poly(vinylidene fluoride)-graft-poly(acrylic acid) (PVDF-g-PAA). X-ray photoelectron spectroscopy, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller surface area measurement were employed to study the molecular structure and morphology of membranes. Through realizing protonation and deprotonation in response to the pH of the aqueous media, the as-prepared membrane is able to alter its wettability and conformation, resulting in the switchable surface oil/water wettability in the aqueous media. More importantly, the as-prepared membrane realized on-demand oil/water separation using gravity alone by switching the pH of the medium. Both separations exhibited excellent efficiency and flux which were attributed to the tree-like structure of the membrane. We believed that this smart membrane with such excellent controllable permeation has potential to be used for several applications, such as water purification, oil recovery and some separation systems. [ABSTRACT FROM AUTHOR]

We use recent developments in local entropy theory to prove that chaos in dynamical systems implies the existence of complicated structure in the underlying space. Earlier Mouron proved that if X is an arc-like continuum which admits a homeomorphism f with positive topological entropy, then X contains an indecomposable subcontinuum. Barge and Diamond proved that if G is a finite graph and f : G → G is any map with positive topological entropy, then the inverse limit space lim ← ( G , f ) contains an indecomposable continuum. In this paper we show that if X is a G -like continuum for some finite graph G and f : X → X is any map with positive topological entropy, then lim ← ( X , f ) contains an indecomposable continuum. As a corollary, we obtain that in the case that f is a homeomorphism, X contains an indecomposable continuum. Moreover, if f has uniformly positive upper entropy, then X is an indecomposable continuum. Our results answer some questions raised by Mouron and generalize the above mentioned work of Mouron and also that of Barge and Diamond. We also introduce a new concept called zigzag pair which attempts to capture the complexity of a dynamical systems from the continuum theoretic perspective and facilitates the proof of the main result. [ABSTRACT FROM AUTHOR]

The reproduction speed of a continuous-time branching random walk is proportional to a positive parameter λ. There is a threshold for λ, which is called λw, that separates almost sure global extinction from global survival. Analogously, there exists another threshold λs below which any site is visited almost surely a finite number of times (i.e. local extinction) while above it there is a positive probability of visiting every site infinitely many times. The local critical parameter λs is completely understood and can be computed as a function of the reproduction rates. On the other hand, only for some classes of branching random walks it is known that the global critical parameter λw is the inverse of a certain function of the reproduction rates, which we denote by Kw. We provide here new sufficient conditions which guarantee that the global critical parameter equals 1/Kw. This result extends previously known results for branching random walks on multigraphs and general branching random walks. We show that these sufficient conditions are satisfied by periodic tree-like branching random walks. We also discuss the critical parameter and the critical behaviour of continuous-time branching processes in varying environment. So far, only examples where λw = 1/Kw were known; here we provide an example where λw > 1/Kw. [ABSTRACT FROM AUTHOR]

A hierarchically Ag/nylon 6 tree-like nanofiber membrane (Ag/PA6 TLNM) was fabricated by adding tetrabutylammonium chloride (TBAC) and silver nitrate (AgNO3) into spinning solution via one-step electrospinning. TBAC presented in PA6/formic acid (HCOOH) spinning solution was able to cause the formation of a tree-like structure due to its space steric structure and the increasing of solution conductivity. Electrospinning solvent acted as a reducing agent for in situ conversion of AgNO into silver nanoparticles (Ag NPs) during the solution preparation. SEM, TEM, FT-IR XPS and XRD confirmed that Ag NPs were doped in the prepared nanofiber membrane successfully and the mechanical properties, pore size distribution and hydrophilicity of the membranes were investigated. The results showed that the tree-like structure improved the mechanical properties and hydrophilicity of the membrane while ensuring high specific surface area and small pore size. And the Ag/PA6 TLNM showed superior antibacterial properties against both E. coli and S. aureus compared with common Ag/PA6 nanofiber membranes (Ag/PA6 NMs). All of the results show that the Ag/PA6 TLNM would have potential applications in water purification. [ABSTRACT FROM AUTHOR]

A novel polyvinylidene fluoride (PVDF) tree-like nanofiber membrane (PVDF-TLNM) was fabricated by adding tetrabutylammonium chloride (TBAC) into a PVDF spinning solution via one-step electrospinning. The structure of the prepared membranes was characterized by field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) and pore size analysis, and the hydrophilic property and microfiltration performance were also evaluated. The results showed that the tree-like nanofiber was composed of trunk fibers and branch fibers with diameters of 100-500 nm and 5-100 nm, respectively. The pore size of PVDF-TLNM (0.36 µm) was smaller than that of a common nanofiber membrane (3.52 µm), and the hydrophilic properties of the membranes were improved significantly. The PVDF-TLNM with a thickness of 30 ± 2 µm showed a satisfactory retention ratio of 99.9% against 0.3 µm polystyrene (PS) particles and a high pure water flux of 2.88 x 104 L x m-2 x h-1 under the pressure of 25 psi. This study highlights the potential benefits of this novel PVDF tree-like nanofiber membrane in the membrane field, which can achieve high flux rates at low pressure. [ABSTRACT FROM AUTHOR]

A subset M of a continuum X is called a meager composant if M is maximal with respect to the property that every two of its points are contained in a nowhere dense subcontinuum of X. Motivated by questions of Bellamy, Mouron and Ordoñez, we show that no tree-like continuum has a proper open meager composant, and that every tree-like continuum has either 1 or 2 ℵ 0 meager composants. We also prove a decomposition theorem: If X is tree-like and every indecomposable subcontinuum of X is nowhere dense, then the partition of X into meager composants is upper semi-continuous and the space of meager composants is a dendrite. [ABSTRACT FROM AUTHOR]

This study investigated the influence of ZnO nanostructures on dye adsorption to increase the photovoltaic conversion efficiency of solar cells. ZnO nanostructures were grown in both tree-like and nanorod (NR) arrays on an AZO/FTO film structure by using a hydrothermal method. The results were observed in detail using X-ray diffraction, field-emission scanning electron microscopy (FE-SEM), UV-visible spectrophotometry, electrochemical impedance spectroscopy, and solar simulation. The selective growth of tree-like ZnO was found to exhibit higher dye adsorption loading and conversion efficiency than ZnO NRs. The multiple 'branches' of 'tree-like nanostructures' increases the surface area for higher light harvesting and dye loading while reducing charge recombination. These improvements result in a 15% enhancement in power conversion. The objective of this study is to facilitate the development of a ZnO-based dye-sensitized solar cell. [ABSTRACT FROM AUTHOR]

Abstract: A novel nanoporous tree-like SiO2 film was synthesized by a sol–gel assisted electrostatic spray deposition (SG-ESD) approach. The sol–gel process employed was better to create SiO2 with linear cross-link chains for the electrostatic spray deposition. From electron microscopic study, it was found that the as-deposited SiO2 films possess nanoporous tree-like morphology in macroscale; and monodispersed hollow nanoporous spherical structure in microscale. The formation of the nanoporous “tree” structure is related to the preferential landing of droplets on the substrate and the electrostatic repulsion force among landing droplets during the ESD process. The catalytic effect of hydrochloric acid in the sol–gel system contributes to the formation of the hollow and porous structured SiO2 spheres. The charge-discharge characteristics of the porous SiO2 as an anode for Li-ion batteries were briefly evaluated and good long-term cycle performance was reached. [Copyright &y& Elsevier]

We find a syntactic characterization of the class $\mathrm{\mathbf{SUB}}(\mathcal{S})\cap\mathrm{Fin}$ of finite lattices embeddable into convexity lattices of a certain class of posets which we call star-like posets and which is a proper subclass in the class of N-free posets. The characterization implies that the class $\mathrm{\mathbf{SUB}}(\mathcal{S})\cap\mathrm{Fin}$ forms a pseudovariety. [ABSTRACT FROM AUTHOR]

Abstract: A homeomorphism of a compactum X with metric d is expansive if there is such that if and , then there is an integer such that . A homeomorphism is continuum-wise expansive if there is such that if A is a nondegenerate subcontinuum of X, then there is an integer such that . Note that every expansive homeomorphism is continuum-wise expansive, but the converse assertion is not true. In this paper, we define the notion of closed subsets having uncountable handles and we prove that if is a continuum-wise expansive homeomorphism of a continuum X and X does not contain any subcontinuum having uncountable handles, then each minimal chaotic continuum of f is indecomposable. As a corollary, we obtain that if X is a k-cyclic continuum and X admits a continuum-wise expansive homeomorphism f, then each minimal chaotic continuum of f is indecomposable. [Copyright &y& Elsevier]

Abstract: Automated segmentation and analysis of tree-like structures from 3D medical images are important for many medical applications, such as those dealing with blood vasculature or lung airways. However, there is an absence of large databases of expert segmentations and analyses of such 3D medical images, which impedes the validation and training of proposed image analysis algorithms. In this work, we simulate volumetric images of vascular trees and generate the corresponding ground-truth segmentations, bifurcation locations, branch properties, and tree hierarchy. The tree generation is performed by iteratively growing a vascular structure based on a user-defined (possibly spatially varying) oxygen demand map. We describe the details of the algorithm and provide a variety of example results. [ABSTRACT FROM AUTHOR]

Abstract: In hierarchal organizations, for assigning tasks to the divisions of the organization some constraints must be satisfied. This article investigates one such problem in which there are k different tasks to be accomplished and each division’s performance on each task may be different and represented by a scalar value. In this article we formally introduce this real life decision problem, named as Maximum-Weighted Tree Matching Problem, and propose a genetic algorithm solution to it, and give some experimental results. [ABSTRACT FROM AUTHOR]

Abstract: We investigate the structure of the collection of terminal subcontinua in homogeneous continua. The main result is a reduction of this structure to six specific types. Three of these types are of one-dimensional spaces, and examples representing these types are known. It is not known whether higher dimensional examples having non-trivial terminal subcontinua and representing the three remaining types exist. [Copyright &y& Elsevier]

Abstract: We propose a new tree-like network model. Our results indicate that the tree-like model has a small-world effect with a small average path length and large clustering coefficient. Strikingly, our tree-like model is scale-free. We also add weight to the links following the network structure. With this adding-weight method, the weight of the nodes shows exponential growth, which is ubiquitous in social networks. [Copyright &y& Elsevier]

We show that certain tree-like continua, that can be realized as inverse limits on [ 0 , 1 ] with set-valued bonding functions, must have the fixed point property. In this class of tree-like continua, one result involves inverse limits for which the bonding functions are interval-valued and their graphs are trees, and another result involves inverse limits whose partial graphs are dendrites. [ABSTRACT FROM AUTHOR]

We consider generalized inverse limits of continua with bonding functions F n that have the projection of Graph(F n) onto the second (first) factor atomic and images (pre-image) of points are zero-dimensional. For such bonding functions we show that under some easily verified conditions that if the first (all) factor space(s) has a certain property then the inverse limit space must have this property. The properties considered include; hereditary decomposability, hereditary indecomposability, hereditary unicoherence, arc-likeness, and tree-likeness. We illustrate the theorems by several examples. [ABSTRACT FROM AUTHOR]

• A new hierarchical river coding method based on the river topology network. • Absorb the both advantages of tree-like and hierarchical river coding method. • Great flexibility to adapt to different basins with abundant or few river segments. • Apply for both of the simple binary-tree and the multi-river convergence situation. River network coding is important for hydrological model on the aspects of water cycles simulation, water resources evaluation and extreme hydrological events forecast. However, the existing river network coding methods had several disadvantages, such as, the river network coding structure is too complex to understand, the river network topology is difficult to identify, the river network coding capacity is limited. To overcome the above-mentioned shortcomings, this paper proposed a new topological and hierarchical river coding method based on the river network created by the DEM (Digital Elevation Method) data and ArcGIS software. This method systematically defines the river levels based on the hydrology structure from outlet to source. The river directly flows into the watershed outlet is river L1, the branch of river L1 with a certain catchment area is river L2, the branch of L2 with a certain catchment area is river L3, and so on. Secondly, we proposed a flexible coding scheme that encode the river segments with pure digital numbers hierarchically. Taking the two-digits scheme for example, the L1 river segments are coded with a sequence number, such as [01], [02], [03], [...]. The L2 river segments inherit the river code from the L1 stem river segment, add a serial of self-order numbers (01, 02, 03, ......) from the junction to the river source, and become [0101], [0102], [0103], [...]. The process of coding the river segments at subsequent level is similar. Finally, this new coding method was programmed in Matlab software, and successfully examined in the Amazon River basin, the world's largest watershed, as a case study. The results show that the new method is competent for easily controlling the river level and river segment density, flexibly adjusting the code digital numbers to fit different basins with abundant or little rivers, easily plotting the topological relationship, automatically encoding by computer program and easily understood. In a word, this study is a useful attempt to create new river network coding method, and it also has positive significance to promote the hydrological simulation research. [ABSTRACT FROM AUTHOR]

A novel polyvinylidene fluoride (PVDF) tree-like nanofiber membrane (PVDF-TLNM) was fabricated by adding tetrabutylammonium chloride (TBAC) into a PVDF spinning solution via one-step electrospinning. The structure of the prepared membranes was characterized by field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) and pore size analysis, and the hydrophilic property and microfiltration performance were also evaluated. The results showed that the tree-like nanofiber was composed of trunk fibers and branch fibers with diameters of 100-500 nm and 5-100 nm, respectively. The pore size of PVDF-TLNM (0.36 μm) was smaller than that of a common nanofiber membrane (3.52 μm), and the hydrophilic properties of the membranes were improved significantly. The PVDF-TLNM with a thickness of 30 ± 2 μm showed a satisfactory retention ratio of 99.9% against 0.3 μm polystyrene (PS) particles and a high pure water flux of 2.88 × 10⁴ L·m -2 ·h -1 under the pressure of 25 psi. This study highlights the potential benefits of this novel PVDF tree-like nanofiber membrane in the membrane field, which can achieve high flux rates at low pressure.