Weighting the structural connectome: Exploring its impact on network properties and predicting cognitive performance in the human brain.

Brain function does not emerge from isolated activity, but rather from the interactions and exchanges between neural elements that form a network known as the connectome. The human connectome consists of structural and functional aspects. The structural connectome (SC) represents the anatomical connections, and the functional connectome represents the resulting dynamics that emerge from this arrangement of structures. As there are different ways of weighting these connections, it is important to consider how such different approaches impact study conclusions. Here, we propose that different weighted connectomes result in varied network properties, and while neither superior the other, selection might affect interpretation and conclusions in different study cases. We present three different weighting models, namely, number of streamlines (NOS), fractional anisotropy (FA), and axon diameter distribution (ADD), to demonstrate these differences. The later, is extracted using recently published AxSI method and is first compared to commonly used weighting methods. Moreover, we explore the functional relevance of each weighted SC, using the Human Connectome Project (HCP) database. By analyzing intelligence-related data, we develop a predictive model for cognitive performance based on graph properties and the National Institutes of Health (NIH) toolbox. Results demonstrate that the ADD SC, combined with a functional subnetwork model, outperforms other models in estimating cognitive performance.

Fabrication of Poly(Lactic Acid)@TiO2 Electrospun Membrane Decorated with Metal-Organic Frameworks for Efficient Air Filtration and Bacteriostasis.

The development of high-performance filtration materials is essential for the effective removal of airborne particles, and metal-organic frameworks (MOFs) anchored to organic polymer matrices are considered to be one of the most promising porous adsorbents for air pollutants. Nowadays, most air filters are generally based on synthetic fiber polymers derived from petroleum residues and have limited functionality, so the use of MOFs in combination with nanofiber air filters has received a lot of attention. Here, a conjugated electrostatic spinning method is demonstrated for the one-step preparation of poly(lactic acid) (PLA) nanofibrous membranes with a bimodal diameter distribution and the anchoring of Zeolitic Imidazolate Framework-8 (ZIF-8) by the introduction of TiO2 and in situ generation to construct favorable multiscale fibers and rough structures. The prepared PLA/TZ maintained a good PM2.5 capture efficiency of 99.97%, a filtration efficiency of 96.43% for PM0.3, and a pressure drop of 96.0 Pa, with the highest quality factor being 0.08449 Pa-1. Additionally, ZIF-8 was uniformly generated on the surface of PLA and TiO2 nanofibers, obtaining a roughened structure and a larger specific surface area. An enhanced filtration retention effect and electrostatic interactions, as well as active free radicals, can be generated for the deep inactivation of bacteria. Compared with the unmodified membrane, PLA/TZ prepared antibacterial characteristics induced by photocatalysis and Zn2+ release, with excellent bactericidal effects against S. aureus and E. coli. Overall, this work may provide a promising approach for the development of efficient biomass-based filtration materials with antimicrobial properties.

Biomimetic grafts from ultrafine fibers for collagenous tissues.

BACKGROUND: The ligament is the soft tissue that connects bone to bone and, in case of severe injury or rupture, it cannot heal itself mainly because of its poor vascularity and dynamic nature. Tissue engineering carries the potential to restore the injured tissue functions by utilization of scaffolds mimicking the structure of native ligament. Collagen fibrils in the anterior cruciate ligament (ACL) have a diameter ranging from 20 to 300 nm, which defines the physical and mechanical properties of the tissue. Also, the ACL tissue exhibited a bimodal distribution of collagen fibrils. Currently, the ability to fabricate scaffolds replicating this structure is a significant challenge. OBJECTIVE: This work aims at i) measuring the diameter of collagens of bovine ACL tissue, ii) investigating the fabrication of sub-100 nm fibers, and iii) fabricating aligned scaffolds with bimodal diameter distribution (with two peaks) resembling the healthy ACL structure. It is hypothesized that such scaffolds can be produced by electrospinning polycaprolactone (PCL) solutions. METHODS: To test the hypothesis, various PCL solutions were formulated in acetone and formic acid in combination with pyridine, and electrospun to generate sub-100 nm fibers. Next, this formulation was adjusted to produce nanofibers with a diameter between 100 nm and 200 nm. Finally, these solutions were combined in the co-electrospinning process, i.e., two-spinneret electrospinning, to fabricate biomimetic scaffolds with a bimodal distribution. RESULTS: Electrospinning of 8% and 15% PCL solutions, respectively, resulted in the production of fibers with diameters below and above 100 nm. The combined scaffold exhibited a bimodal distribution of aligned fibers with peaks around 80 and 180 nm, thus mimicking the collagen fibrils of healthy ACL tissue. CONCLUSION: This research is expected to have a society-wide impact because it aims to enhance the health condition and life quality of a wide range of patients.

Inversion of magnetic diameter distribution of magnetic fluids under high and low temperatures.

The magnetic diameter is a crucial factor affecting the magnetic properties of magnetic fluids. The magnetic diameter distribution can be estimated based on the magnetic properties. However, the magnetic dipole interaction of magnetic nanoparticles (MNPs) and the variation of the magnetic diameter with temperature have received relatively little attention in previous research. Hence, this research proposes the AP-MMF1-L method to inverse the magnetic diameter which considers the magnetic dipole interaction and derives the magnetic diameter at different temperatures. Firstly, the AP-MMF1-L uses the least square method between the first-order modified mean-field Langevin function (MMF1-L) and the measured magnetization curve as the objective function. Meanwhile, the hybrid Artificial bee colony-particle swarm (AP) optimization algorithm is introduced to inverse the optimal magnetic diameter distribution. Secondly, the hydrodynamic diameter distribution experimental values are compared with the theoretical values, demonstrating the AP-MMF1-L method obtains accurate inversion results of the magnetic diameter distribution when compared to other models. Finally, the arithmetic mean of the magnetic diameter at different temperatures is investigated, revealing a decreasing trend as the temperature rises, approximately following a linear distribution. The AP-MMF1-L provides a novel and effective tool for accurately determining the magnetic diameter of the MNPs across various temperatures.

Optimizing Exosome Preparation Based on Size and Morphology: Insights From Electron Microscopy.

Extracellular vesicles (EVs), including exosomes, are crucial in intercellular communication, but differentiating between exosomes and microvesicles is challenging due to their similar morphology and size. This study focuses on multivesicular bodies (MVBs), where exosomes mature, and optimizes exosome isolation using transmission electron microscopy (TEM) for size information. Considering that EVs are nanocolloidal particles, a salt-free Bis-Tris buffer is found to maintain EV integrity better than phosphate-buffered saline (PBS). Dynamic light scattering (DLS) and TEM analysis confirm that intact exosome fractions under the salt-free Bis-Tris buffer condition exhibit polydispersity, including a unique population of <50 nm vesicles resembling intraluminal membrane vesicles (ILVs) in MVBs, alongside larger populations. This <50 nm population disappears in PBS or Bis-Tris buffer with 140 mM NaCl, transforming into a monodisperse population >100 nm. Immunoelectron microscopy also validates the presence of CD63, an exosome biomarker, on approximately 50 nm EVs. These findings provide valuable insights into exosome characterization and isolation, essential for future biomedical applications in diagnostics and drug delivery.

Study on the effects of stand density management of Chinese fir plantation in Northern China.

The aim of this study was to clarify the mechanism by which thinning alters stand structure and affects forest productivity by characterizing changes in stand quantitative maturity age, stand diameter distribution, structural heterogeneity, and forest productivity of Chinese fir plantations at different thinning times and intensities. Our findings provide insights into how the density of stands could be modified to enhance the yield and timber quality of Chinese fir plantations. The significance of differences in individual tree volume, stand volume, and timber merchantable volume was determined using one-way analysis of variance and post hoc Duncan tests. The stand quantitative maturity age was obtained using the Richards equation. The quantitative relationship between stand structure and productivity was determined using a generalized linear mixed model. We found that (1) the quantitative maturity age of Chinese fir plantations increased with thinning intensity, and the quantitative maturity age was much greater under commercial thinning than under pre-commercial thinning. (2) Individual tree volume and the proportion of medium-sized and large-sized timber merchantable volume increased with stand thinning intensity. Thinning promoted increases in stand diameter. pre-commercially thinned stands were dominated by medium-diameter trees when the quantitative maturity age was reached, whereas commercially thinned stands were dominated by large-diameter trees. The living trees volume will decrease immediately after thinning, and then it will gradually increase with the age of the stand. When the stand volume included both living trees volume and thinned volume, thinned stands increased stand volume compared with unthinned stands. In pre-commercial thinning stands, the greater the intensity of thinning, the greater the increase in stand volume, and the opposite was true for commercial thinning. (3) Thinning also reduced heterogeneity in stand structure, which was lower after commercial thinning than after pre-commercial thinning. The productivity of pre-commercially thinned stands increased with thinning intensity, whereas that of commercially thinned stands decreased with thinning intensity. (4) The structural heterogeneity of pre-commercially and commercially thinned stands was negatively and positively correlated with forest productivity, respectively. In the Chinese fir plantations in the hilly terrain of the northern Chinese fir production area, when pre-commercial thinning was performed in the ninth year to a residual density of 1750 trees per hectare, the stand quantitative maturity age was reached in year 30, medium-sized timber accounted for 75.2% of all trees, and the stand volume was 667.9 m3 per hectare. This thinning strategy is favorable for producing medium-sized Chinese fir timber. When commercial thinning was performed in year 23, the optimal residual density was 400 trees per hectare. When the stand quantitative maturity age was reached in year 31, large-sized timber accounted for 76.6% of all trees, and the stand volume was 574.5 m3 per hectare. This thinning strategy is favorable for producing large-sized Chinese fir timber.

Collagen Fibril Diameter Distribution of Sheep Anterior Cruciate Ligament.

The anterior cruciate ligament (ACL) tissue is a soft tissue connecting the femur and tibia at the knee joint and demonstrates a limited capacity for self-regeneration due to its low vascularity. The currently available clinical procedures are unable to fully restore damaged ACL tissue, and tissue engineering can offer options with a potential of restoring the torn/ruptured ACL by using biomimetic constructs that are similar to native tissue in terms of structure, composition, and functions. However, a model substrate to understand how the ACL cells regenerate the injured tissue is still not available. In this study, it is hypothesized that the nanofiber-based model substrate with bimodal and unimodal fiber diameter distributions will mimic the diameter distribution of collagen fibrils seen in healthy and injured sheep ACL, respectively. The aims were to (i) create an ACL injury in a sheep ACL by applying extensional force to rupture the healthy ACL tissue, (ii) measure the collagen fibril diameter distributions of healthy and injured ACL, (iii) fabricate polycaprolactone (PCL) nanofiber-based model constructs using electrospinning with diameter distributions similar to healthy and injured ACL tissue, and (iv) measure mechanical properties of ACL tissue and PCL electrospun constructs. The results showed that the fiber diameter distributions of PCL electrospun constructs and those of the healthy and injured ACL tissues were similar. The novelty in this investigation is that the collagen fibril diameter distribution of healthy and injured sheep ACL tissues was reported for the first time. The study is significant because it aims to create a model construct to solve an important orthopedic-related clinical problem affecting millions of people globally. The model construct fabricated in this work is expected to have an important impact on ACL regeneration efforts.

Research on Three-Dimensional Porous Composite Nano-Assembled α-MnO2/Reduced Graphene Oxides and Their Super-Capacitive Performance.

A series of three-dimensional porous composite α-MnO2/reduced graphene oxides (α-MnO2/RGO) were prepared by nano-assembly in a hydrothermal environment at pH 9.0-13.0 using graphene oxide as the precursor, KMnO4 and MnCl2 as the manganese sources and F- as the control agent of the α-MnO2 crystal form. The α-MnO2/RGO composites prepared at different hydrothermal pH levels presented porous network structures but there were significant differences in these structures. The special pore structure promoted the migration of ions in the electrolyte in the electrode material, and the larger specific surface area promoted the contact between the electrode material and the electrolyte ions. The introduction of graphene solved the problem of poor conductivity of MnO2, facilitated the rapid transfer of electrons, and significantly improved the electrochemical performance of materials. When the pH was 12.0, the specific surface area of the 3D porous composite material αMGs-12.0 was 264 m2·g-1, and it displayed the best super-capacitive performance; in Na2SO4 solution with 1.0 mol·L-1 electrolyte, the specific capacitance was 504 F·g-1 when the current density was 0.5 A·g-1 and the specific capacitance retention rate after 5000 cycles was 88.27%, showing that the composite had excellent electrochemical performance.

A biomimetic synthetic nanofiber-based model for anterior cruciate ligament regeneration.

Reconstructed ACL cannot completely restore its functions due to absence of physiologically viable environment for optimal biomaterial-cell interaction. Currently available procedures only mechanically attach grafts to bone without any biological integration. How the ACL cells perform this biological attachment is not fully understood partly due to the absence of appropriate environment to test cell behavior both in vitro and in vivo. Availability of biomimetic models would enable the scientists to better explore the behavior of cells at health and during tissue healing. In this study, it is hypothesized that the collagen fibril diameter distribution in rat ACL changes from a bimodal distribution in the healthy ACL to a unimodal distribution after injury, and that this change can be mimicked in synthetic nanofiber-based constructs. This hypothesis was tested by first creating an injured rat ACL model by applying a mechanical tensile force to the healthy ACL tissue until rupture. Secondly, the collagen fibril diameter distributions of healthy and injured ACL tissue were determined, and polycaprolactone (PCL) constructs were created to mimic the distributions of collagen fibrils in healthy and injured tissues. Findings reveal that the fiber diameter distribution of aligned bimodal PCL constructs were similar to that of the collagen fibrils in native ACL tissue. This study is significant because suggested bimodal and unimodal fibrous model constructs, respectively, represent a healthy and injured tissue environment and the behavior of ACL cells cultured on these constructs may provide significant input on ACL regeneration mechanism.

Number concentration dependence of ultrasonic disruption ratio of diameter-sorted microcapsules.

The use of ultrasound to destroy microcapsules in microbubble-assisted drug delivery systems (DDS) is of great interest. In the present study, the disruption ratios of capsule clusters were measured by observing and experimentally analyzing microcapsules with polymer shells undergoing disruption by ultrasound. The microcapsules were dispersed in a planar microchamber filled with a gelatin gel and sonicated using 1 MHz focused ultrasound. Different capsule populations were obtained using a filtration technique to modify and control the capsule sizes. The disruption ratio as a function of the concentration of capsules was obtained through image processing of the recorded photomicrographs. We found that the disruption ratio for each population exponentially decreases as the particle number concentration (PNC) increases. The maximum disruption ratio of the diameter-sorted capsules was larger than that of polydispersed capsules. Particularly, for resonant capsule populations, the ratio was more than twice that of polydispersed capsules. Furthermore, the maximum disruption ratio occurred at higher concentrations as the mean particle diameter of the capsule cluster decreased.

The Salem simulator version 2.0: a tool for predicting the productivity of pure and mixed forest stands and simulating management operations.

A growing body of research suggests mixed-species stands are generally more productive than pure stands as well as less sensitive to disturbances. However, these effects of mixture depend on species assemblages and environmental conditions. Here, we present the Salem simulator, a tool that can help forest managers assess the potential benefit of shifting from pure to mixed stands from a productivity perspective. Salem predicts the dynamics of pure and mixed even-aged stands and makes it possible to simulate management operations. Its purpose is to be a decision support tool for forest managers and stakeholders as well as for policy makers. It is also designed to conduct virtual experiments and help answer research questions. In Salem, we parameterised the growth in pure stand of 12 common tree species of Europe and we assessed the effect of mixture on species growth for 24 species pairs (made up of the 12 species mentioned above). Thus, Salem makes it possible to compare the productivity of 36 different pure and mixed stands depending on environmental conditions and user-defined management strategies. Salem is essentially based on the analysis of National Forest Inventory data. A major outcome of this analysis is that we found species mixture most often increases species growth, in particular at the poorest sites. Independently from the simulator, foresters and researchers can also consider using the species-specific models that constitute Salem: the growth models including or excluding mixture effect, the bark models, the diameter distribution models, the circumference-height relationship models, as well as the volume equations for the 12 parameterised species. Salem runs on Windows, Linux, or Mac. Its user-friendly graphical user interface makes it easy to use for non-modellers. Finally, it is distributed under a LGPL license and is therefore free and open source.

Collagen fibril diameter distribution affects permeability of ligament tissue: A computational study on healthy and injured tissues.

Background and objective In avascular or hypovascular tissues, elements required for maintaining tissue functions are recruited through diffusion, which is highly related with the permeability of the extracellular matrix in health and injury. Here, we investigate the effect of collagen fibril diameter distribution of bovine Anterior Cruciate Ligament (ACL) tissue on the hydraulic permeability of the matrix. Based on the fact that the diameter distribution is significantly different between healthy and injured ACL tissues, our study aims to investigate the effect of such variability on the hydraulic permeability. Methods Simulations are carried out in 3D geometries reconstructed from actual collagen filament/fibril diameter distributions obtained from healthy and injured tissue samples (n=3). The fluid flow through the fibrous tissue is modeled based on Eringen's theory of micropolar fluid flow to determine the effects of vortex viscosity (m) and spin gradient viscosity (N) on hydraulic permeability. Results Computational results indicate that the hydraulic permeability of models which are replicates of healthy ACL tissues is higher than that of the injured, indicating that the filament size distribution might play an important role on fluid and nutrient transport through ligament tissues. Conclusions These findings underscore the need for increased attention on replicating the diameter distribution of healthy collagens in tissue engineering scaffolds and allowing adequate supply of elements through permeation during ACL reconstruction procedures.

[Spatial distribution pattern and scale effect of secondary forests in Daxing'anling, China]. / å¤§å ´å®‰å²­æ¬¡ç”Ÿæž—ç©ºé—´åˆ†å¸ƒæ ¼å±€åŠå ¶å°ºåº¦æ•ˆåº”.

We examined the spatial distribution patterns and their scale effects of different tree species (Larix gmelinii, Betula platyphylla and others) and different size classes of trees (1-5) of natural L. gmelinii secondary forest (LF), natural B. platyphylla secondary forest (BF) and the mixed secondary forest of both species (MF) in Daxing'anling. The results showed that among the three forest types, LF was the only one type reaching a good state of regeneration, while other two forest types were poorly regenerated. For different forest types, the abundance of seedlings and saplings in the regeneration layer were significantly different from that of the tree layer, and the diameter distribution (except for LF and BF) and height distribution of trees in each forest type were not reasonable, indicating that all the three forest types belonged to unstable communities. At species level, the spatial distributions of main species in each plot were mainly clumped. The five indicators used in this study varied significantly with the scales, which mainly focused on the linear increases (40%), the power increases (22%) and the negative quadratic polynomials (20%), respectively. For different size classes, significant clumped distributions were observed for the regeneration levels (1-3), while the spatial distribution of tree layers (4-5) usually fluctuated distinctly among various distribution patterns. The scale effects of different size classes were mainly dominated by the linear increases (44%), the power increases (15%) and the negative quadratic polynomials (12%). For each forest type and sampling scale, the cluster degrees of trees decreased significantly with increasing tree sizes. Within each forest type, the pattern size of non-dominant species was significantly larger than that of dominant species, while the pattern size of regeneration layers was significantly larger than that of tree layers.

Integrating floc, aggregate and carrier to reap high-quality anammox biofilm.

This work investigated the effects of integration of floc, aggregate and carrier (IFAC) on anammox biofilm quality and development mechanisms. The IFAC system harvested high-quality anammox biofilm with a reduction of 60% in the formation period, an increment of 282.14%~397.26% in mechanical stability, an enhancement of 10.18 ~ 21.56% in ecological stability and an improvement of 9.44%~46.18% in abundance of the phylum Planctomycetes. Aggregates enabled carriers to accumulate initial biomass efficiently and equipped biofilm with additional joint forces. Floc promoted accumulation of terminal biomass, enhanced ecological stability by improving community diversity and raised abundance of the phylum Planctomycetes by assisting anammox consortium settlement. A model of the development procedure of high-quality anammox biofilm was established and a strategy for pre-designing the IFAC system to reap high-quality biofilm was proposed. We expect our findings to provide theoretical guidance for designs and applications of anammox process with excellent stability.

Electrospun Jets Number and Nanofiber Morphology Effected by Voltage Value: Numerical Simulation and Experimental Verification.

Electrical voltage has a crucial effect on the nanofiber morphology as well as the jet number in the electrospinning process, while few literatures were found to explain the deep mechanism. Herein, the electrical field distribution around the spinning electrode was studied by the numerical simulation firstly. The results show that the electrical field concentrates on the tip of a protruding droplet under relatively low voltage, while subsequently turns to the edge of needle tip when the protruding droplet disappears under high voltage. The experimental results are well consistent with the numerically simulated results, that is, only one jet forms at low voltage (below 20 kV for PVDF-HFP and PVA nanofiber), but more than one jet forms under high voltage (two jets for PVDF-HFP nanofiber, four jets for PVA nanofiber). These more jets lead to (1) higher fiber diameter resulting from actually weaker electrical field for each jet and (2) wide distribution of fiber diameters due to unstable spinning process (changeable jet number/site/height) under high voltage. The results will benefit the nanofiber preparation and application in traditional single-needle electrospinning and other electrospinning methods.

[Quantitative evaluation for separation of water-soluble and water-insoluble particulate matter on leaf surface of tree species: Taking five tree species as examples.] / 植物叶片表面水溶与非水溶性颗粒物滞纳量分离定量评估­­ä»¥5ç§æ ‘ç§ä¸ºä¾‹.

To accurately and quantitatively evaluate the mass and particle size distribution of water-soluble and water-insoluble particulate matters (PM) on the surface of tree leaves, which would help to improve the accuracy of quantitative assessment of the retention ability of urban trees to atmospheric particles, we collected leaf samples from three broadleaved tree species [Ginkgo (Ginkgo biloba), Chinese scholar tree (Sophora japonica) and weeping willow (Salix babylonica)] and two conifer species [Chinese pine (Pinus tabuliformis) and China savin (Sabina chinensis)] 14 d after the rain (rainfall>15 mm). The PMs retained on leaves were collected by a succeeding procedure of washing + brushing (WC+BC) and ultrasonic cleaning (UC). Then, the extracts at each step were divided into water-soluble and water-insoluble PMs through centrifuge. The mass of water-soluble and water-insoluble particles were dry weighted. Then, the water-soluble and water-insoluble particles were dissolved by anhydrous ethanol and deionized water to measure the particle size distribution. The mass of water-soluble and water-insoluble particles with different particle sizes was calculated. Results showed that the mass (proportion) of water-soluble PMs retained on leaf surfaces of broad-leaved and conifer species were 480.61 (52.3%) and 438.91 (47.7%) mg·m-2, respectively, while that for water-insoluble PMs were 97.93 (12.0%) and 715.84 (88.0%) mg·m-2, respectively. The particle size distribution of water-soluble particles on the leaves of the five tree species showed the unimodal curve with mean size of 40.36 µm. Water-insoluble particles on leaves showed multimodal distribution, with mean size of 105.65 µm. S. japonica and G. biloba had higher PM retention ability in regions suffering with more water-soluble PM pollution, while S. chinensis had higher retention ability to water-insoluble PMs.

Statistically Rigorous Silver Nanowire Diameter Distribution Quantification by Automated Electron Microscopy and Image Analysis.

Silver nanowire (AgNW) diameters are typically characterized by manual measurement from high magnification electron microscope images. Measurement is monotonous and has potential ergonomic hazards. Because of this, statistics regarding wire diameter distribution can be poor, costly, and low-throughput. In addition, manual measurements are of unknown uncertainty and operator bias. In this paper we report an improved microscopy method for diameter and yield measurement of nanowires in terms of speed/automation and reduction of analyst variability. Each step in the process to generate these measurements was analyzed and optimized: microscope imaging conditions, sample preparation for imaging, image acquisition, image analysis, and data processing. With the resulting method, average diameter differences between samples of just a few nanometers can be confidently and statistically distinguished, allowing the identification of subtle incremental improvements in reactor processing conditions, and insight into nucleation and growth kinetics of AgNWs.

Along-axon diameter variation and axonal orientation dispersion revealed with 3D electron microscopy: implications for quantifying brain white matter microstructure with histology and diffusion MRI.

Tissue microstructure modeling of diffusion MRI signal is an active research area striving to bridge the gap between macroscopic MRI resolution and cellular-level tissue architecture. Such modeling in neuronal tissue relies on a number of assumptions about the microstructural features of axonal fiber bundles, such as the axonal shape (e.g., perfect cylinders) and the fiber orientation dispersion. However, these assumptions have not yet been validated by sufficiently high-resolution 3-dimensional histology. Here, we reconstructed sequential scanning electron microscopy images in mouse brain corpus callosum, and introduced a random-walker (RaW)-based algorithm to rapidly segment individual intra-axonal spaces and myelin sheaths of myelinated axons. Confirmed by a segmentation based on human annotations initiated with conventional machine-learning-based carving, our semi-automatic algorithm is reliable and less time-consuming. Based on the segmentation, we calculated MRI-relevant estimates of size-related parameters (inner axonal diameter, its distribution, along-axon variation, and myelin g-ratio), and orientation-related parameters (fiber orientation distribution and its rotational invariants; dispersion angle). The reported dispersion angle is consistent with previous 2-dimensional histology studies and diffusion MRI measurements, while the reported diameter exceeds those in other mouse brain studies. Furthermore, we calculated how these quantities would evolve in actual diffusion MRI experiments as a function of diffusion time, thereby providing a coarse-graining window on the microstructure, and showed that the orientation-related metrics have negligible diffusion time-dependence over clinical and pre-clinical diffusion time ranges. However, the MRI-measured inner axonal diameters, dominated by the widest cross sections, effectively decrease with diffusion time by ~ 17% due to the coarse-graining over axonal caliber variations. Furthermore, our 3d measurement showed that there is significant variation of the diameter along the axon. Hence, fiber orientation dispersion estimated from MRI should be relatively stable, while the "apparent" inner axonal diameters are sensitive to experimental settings, and cannot be modeled by perfectly cylindrical axons.

Properties of natural rubber reinforced with cellulose nanofibers based on fiber diameter distribution as estimated by differential centrifugal sedimentation.

Cellulose nanofibers (CNFs) with different degrees of fibrillation are prepared by the mechanical fibrillation of kraft pulp using wet disk milling, and dispersions of the prepared CNFs were subjected to differential centrifugal sedimentation (DCS) in order to estimate the diameter distributions of the CNFs. The low-fibrillated CNFs (fiber diameter (d): >10 µm) had a weak reinforcing effect on natural rubber (NR), while the medium-fibrillated CNFs (d: 0.1-10 µm) dramatically improve the initial modulus and decrease the elongation at break. The high-fibrillated CNFs (d: <0.1 µm) enhanced the tensile strength even further while maintaining the elongation at break. The reinforcing mechanism of the NR composites reinforced by the CNFs (NR-CNFs) was confirmed by field-emission scanning electron microscopy imaging, dynamic mechanical analysis, and toluene uptake measurements. It was concluded that these characteristic mechanical properties of the NR-CNFs were determined by the morphologies of the CNFs. The branching structure of the medium-fibrillated CNFs affected high improvement of the initial modulus, and the network formed by the high-fibrillated CNFs were involved in enhancement of the tensile strength without compromising viscoelastic properties. Understanding the effect of their diameter distribution can potentially reduce the production cost of CNFs and thus expand their applicability.

Will forest size structure follow the -2 power-law distribution under ideal demographic equilibrium state?

Scaling relations formed in forest development processes are fairly important for understanding and predicting forest dynamics. During self-thinning of a relatively even-sized forest, tree abundance will decrease with an increase in average tree size, forming the size-abundance relation (SAR); while for a size-structured forest under the demographic equilibrium state, the frequency of trees also varies with size classes in a similar, decreasing pattern, manifesting as the size-frequency distribution (SFD). In the metabolic scaling theory (MST), the two scaling relations are considered to be consistent. However, in this paper, we proved that SFD can never be equivalent to SAR unless the growth rate of tree diameters is a constant. The reason derives from the time differences of transition between different size classes, which are influenced in SFD maintenance but not in SAR formation. Demographic equilibrium of a size structured forest requires a different resource allocation among different size classes at the same time, which contradicts the resource conservation during SAR formation in the self-thinning process. Consequently, if the rate of resource use per individual scales as a +2 power with its diameter according to MST, which led to the -2 power SAR, SFD can never be a -2 power-law distribution. The previous confusion between SFD of a size-structured forest and SAR formed during self-thinning processes may lead to many misunderstandings and unreliable predictions on forest structure and dynamics.