Bundle Size Research Articles

Myosin activity drives actomyosin bundle formation and organization in contractile cells of the Caenorhabditis elegans spermatheca.

Stress fibers-contractile actomyosin bundles-are important for cellular force production and adaptation to physical stress and have been well studied within the context of cell migration. However, less is known about actomyosin bundle formation and organization in vivo and in specialized contractile cells, such as smooth muscle and myoepithelial cells. The Caenorhabditis elegans spermatheca is a bag-like organ of 24 myoepithelial cells that houses the sperm and is the site of fertilization. During ovulation, spermathecal cells are stretched by oocyte entry and then coordinately contract to expel the fertilized embryo into the uterus. Here we use four-dimensional confocal microscopy of live animals to observe changes to spermathecal actomyosin network organization during cell stretch and contraction. Oocyte entry is required to trigger cell contraction and concomitant production of parallel actomyosin bundles. Actomyosin bundle size, connectivity, spacing, and orientation are regulated by myosin activity. We conclude that myosin drives actomyosin bundle production and that myosin activity is tightly regulated during ovulation to produce an optimally organized actomyosin network in C. elegans spermathecae.

Internanofiber Spacing Adjustment in the Bundled Nanofibers for Sensitive Fluorescence Detection of Volatile Organic Compounds.

In this work, we report the fabrication of hierarchical nanofiber bundles from a perylene monoimide molecule that enable the sensitive detection of various inert volatile organic compounds (VOCs). We demonstrate that the internanofiber spacing of the bundles with appropriate packing interactions can be effectively adjusted by various VOCs, which is in turn translated into the dynamic fluorescence responses. Upon further decreasing the size of the nanofiber bundles, of which the internanofiber spacing is more favorably adjusted, enhanced fluorescence responses to various VOC vapors can be achieved. Our work presents a new protocol, i.e., translating the stimuli-responsive internanofiber spacing into fluorescence responses, to construct novel fluorescence sensors for various hazardous chemical vapors.

Microtubule Bundles in the Adult Cardiomyocyte

The role of Microtubules (MTs) in mechanosignalling and mechanical properties has seen a recent surge of interest among the cardiac and skeletal muscle community. We recently reported that MTs buckle and bear load during the cardiac cycle. This has a significant effect on contractile mechanics, suggesting that myocyte function is tunable by any regulatory pathway that alters the mechanical behavior of MTs. Other work ongoing in our lab indicates that a number of Microtubule Associated Proteins (MAPs) are robustly upregulated in human heart disease. Multi-MT assemblies or bundles associated with these and other MAPs have been observed and studied extensively in other contexts, including unicellular motile structures and neuronal axons, but have not been examined in cardiac myocytes. The number of MTs involved, their geometry and the relative abundance of such structures compared to isolated MTs have significant implications for the mechanical properties of a myocyte. Using targeted overexpression of several MAPs in adult rat cardiomyocytes, we examine the structure, magnitude and prevalence of MT bundles by electron microscopy. We find that single MTs are the most prevalent MT elements in the unmanipulated myocyte, accompanied by comparatively rare and small groupings of 2-3 MTs with wide spacing. MTs are preferentially located at the interface between myofibril and mitochondria. Manipulation of MT binding partners can modestly increase the size and likelihood of MT bundles, and also dramatically reduces the inter-tubule spacing to be in-line with canonical bundle spacing. When we further characterized the functional consequences of MT bundling on cardiac contractility, we were surprised to find that the promotion of bundling, at least with certain MAPs, does not appear to impair contraction by reinforcing compliant microtubules, but rather uncouples the MTs from the process of contraction-associated buckling.

Mechanics and Dynamics of Cation-Induced Actin Bundles

The assembly of actin filaments into bundles plays an essential role in mechanical strength and dynamic reorganization of cytoskeleton. Divalent counterions at high concentrations promote bundle formation through electrostatic attraction between charged filaments. Although it has been hypothesized that specific cation interactions may contribute to salt-induced bundling, molecular mechanisms of how salt modulates bundle assembly and mechanics are not well established. Here we determine the mechanical and dynamic properties of actin bundles at varying divalent cation concentrations. Using total internal reflection fluorescence (TIRF) microscopy, we measure the bending stiffness of actin bundles determined by persistence length analysis. We characterize real-time formation of bundles by dynamic light scattering intensity and direct visualization using TIRF microscopy. Our results show that divalent cations stiffen actin bundles and modulate time-dependent average bundle size. The work suggests that cation interactions serve a regulatory function in actin bundle mechanics and dynamics.

Large-Scale Bundle Size Pricing: A Theoretical Analysis

Bundle size pricing (BSP) is a multi-dimensional selling mechanism where the firm prices the size of the bundle rather than the different possible combinations of bundles. In BSP, the firm offers the customer a menu of different sizes and prices. The customer then chooses the size that maximizes his surplus and customizes his bundle given his chosen size. While BSP is commonly used across several industries, little is known about the optimal BSP policy in terms of sizes and prices along with the theoretical properties of its profit. In this paper, we provide a simple and tractable theoretical framework to analyze the large-scale BSP problem where a multi-product firm is selling a large number of products. The BSP problem is in general hard as it involves optimizing over order statistics, however we show that for large numbers of products, the BSP problem transforms from a hard multi-dimensional problem to a simple multi-unit pricing problem with concave and increasing utilities. Our framework allows us to identify the main source of inefficiency of BSP that is the heterogeneity of marginal costs across products. For this reason, we propose two new BSP policies called clustered BSP'' and assorted BSP'' that significantly reduce the inefficiency of regular BSP. We then utilize our framework to study richer models of BSP such as when customers have budgets and when there exists multiple customer types.

Mechanical agitation induces counterintuitive aggregation of pre-dispersed carbon nanotubes

Mechanical agitation is commonly used to fragment and disperse insoluble materials in liquids. However, here we show that when pristine single-walled carbon nanotubes pre-dispersed in water are subject to vortex-shaking for very short periods (typically 10–60s, power density ∼0.002WmL−1), re-aggregation counterintuitively occurs. The initial dispersions are produced using surfactants as dispersants and powerful tip sonication (∼1WmL−1) followed by centrifugation. Detailed imaging by light and electron microscopies shows that the vortex-induced aggregates consist of loose networks (1–102μm in size) of intertwined tubes and thin bundles. The average aggregate size increases with vortexing time in an apparently logarithmic manner and depends on the dispersant used, initial concentration of nanotubes and size distribution of bundles. The aggregation is, nonetheless, reversible: if the vortex-shaken dispersions are mildly bath-sonicated (∼0.03WmL−1), the flocs break down and re-dispersal occurs. Molecular insight for the mechanism behind this surprising phenomenon is put forth.

Internal structure and fatigue performance of quasi-unidirectional non-crimp fabric reinforced laminates

The aim of this work was to study the effect of stitch pattern and stitch tension on tension-tension fatigue performance of quasi-unidirectional non-crimp fabric reinforced glass-fibre/epoxy laminates. Internal structure variations of the laminates were characterised using cross-sectional microscopy imaging for the evaluation of fatigue test results. Reinforcements for the study were manufactured with three different stitch patterns and two different stitch tensions. Based on the results, the stitch pattern contributes to in-plane and out-of-plane waviness of fibres, as well as on the size and shape of the axial fibre bundles. The fatigue life and slope parameter of the fitted S-N curve were significantly dependent on the stitch pattern, while they were not dependent on the applied stitch tension.

Bundle-Pricing Decision Model for Multiple Products

Bundling is an efficient method to achieve business objectives in many industries. However decisions of bundle selection and pricing are complicated when multiple products are involved. In this paper, we investigate a bundle-pricing decision model for multiple products. With the objective to maximize the retailer’s profit, an integrated bundle-pricing model for multiple commodities is formulated as a Non-Linear Mixed Integer Program based on the framework of Stackelberg game. By adding auxiliary decision variables, this model is converted into a Mixed Integer Linear Program and solved by Cplex. Numerical experiments and sensitive analysis are conducted to provide managerial insights for bundling multiple products. It indicates that low consumption level consumers prefer bundles composed of more commodities with lower prices. The products with higher cost level should be bundled with smaller bundle size and higher prices.

Bundle Size Engineering of Single-Walled Carbon Nanotubes on Silica Nanoparticles

Small and large single-walled carbon nanotubes (SWCNTs) bundles from different-sized cobalt catalyst clusters have been synthesized and prepared through chemical vapor deposition (CVD) method by using Co-acetate ethanol solution with silica nanoparticles. By controlling concentration of Co-acetate ethanol solution (0.2 wt% and 0.4 wt%), various sizes and types of bundle of SWCNTs are grown on the silica nanoparticle substrates. Synthesized SWCNT’s diameter ranged from 0.92 nm to 1.63 nm, and chirality of SWCNTs and their electronic property from high concentration solution show diverse characteristics. In high concentration solution, the large number of cobalt clusters is induced to merge on the surface of silica nanoparticles and then lots of nucleation points are provided by cobalt clusters for growth of SWNTs. These results give us a promising path to selectively synthesize various types of SWCNTs with different shapes of merged cobalt catalyst. Engineering bundle sizes of SWCNTs can be promising key for diverse applications of carbon nanotubes.

Leaf anatomy of Acrocomia (Arecaceae): an additional contribution to the taxonomic resolution of a genus with great economic potential

Acrocomia is one of the most complex genera to understand in the Neotropical Arecaceae, and there is no consensus on the number of species in the genus. A comparative study of leaf anatomy was conducted on seven species of Acrocomia: one with a wide distribution in the Americas (A. aculeata), five endemic to different regions of Brazil, Bolivia and Paraguay (A. emensis, A. glaucescens, A. hassleri, A. intumescens and A. totai) and one endemic to Cuba (A. crispa). Characters that unify the species of Acrocomia include the following: epidermis covered with cuticle, hypodermis on both sides of the leaflets, non-vascular fiber bundles, and primary and secondary vascular bundles. The shape of the leaflet margin, the distribution of the primary vascular bundles and fiber bundles, the number of idioblasts with raphides and the size of the vascular bundles, along with other characteristics, were used to distinguish these species in Acrocomia.

Tracking of the inferior alveolar nerve: its implication in surgical planning.

The objective of the study is to assess the correlation between the mandibular canal tracing done on cone beam CT (CBCT) data, with the size, shape, and position of the neurovascular bundle (NB) obtained by magnetic resonance imaging (MRI). Six human cadaver mandibles were scanned with a CBCT Promax® scanner (Planmeca, Helsinki, Finland) and with an Ingenia® 3.0T MR system (Philips, Amsterdam, The Netherlands). The NB was segmented from the MRI dataset, while the mandibular canal (MC) tracing was done on the CBCT images. Quantitative 3D analysis was made for the full-segmented nerves and for three defined regions of specific clinical interest, namely angle, body, and mental region. From the 3D MRI analysis, the nerve thickness (for the angle, body, and mental region) ranges from 0.8 to 5.2mm, while the thickness of the mandibular canal tracing is approximately 2.00mm on both sides as chosen in the tracing software. The mean volume of the NB on the left is 828.49±215.54mm3 and on the right 792.98±264.57mm3. For the nerve tracing, the mean value is 351.92±16.42 and 339.69±16.12mm3 on the left and right sides, respectively. Wilcoxon signed-rank test showed significant differences between NB and MC volume measurements (p=0.0005). The Bland-Altman plots show an increasing slope for thickness and volume, indicating that the absolute differences between neurovascular bundle, estimated by MRI, and the mandibular canal, drawn on the CBCT images, increase with larger mean values. Surgeons should be aware of the shortcomings of nerve tracing in the different regions of the mandible. Tracing of the inferior alveolar nerve (IAN) underestimates shape and volume. Whenever nerve tracing instead of well-recognizable anatomical bony landmarks is used for surgical planning that need precision, a wider safe margin is recommended.

Characterizing dispersion and long term stability of concentrated carbon nanotube aqueous suspensions for fabricating ductile cementitious composites

This paper reports a systematic attempt of preparing concentrated aqueous suspensions (up to 0.3wt.%) of different types of carbon nanotubes (CNTs) using Pluronic F-127 for developing ductile cementitious composites. Single-walled and multi-walled nanotubes, both pristine and functionalized, were dispersed in water using a short (1h) and medium energy (80W) ultrasonication process using pluronic at high concentrations (above critical micelle concentration, 1–5wt.%) and also using sodium dodecylbenzene sulphonate (SDBS) for comparison purpose. The CNT suspensions were characterized for agglomerate area, particle size, zeta potential, extractability and long-term storage stability for a period over 4years. The optimum suspensions were used to fabricate cementitious composites and their fracture behavior was characterized. Experimental results suggested that the optimum pluronic concentrations (1% for 0.1% CNT, 5% for 0.2% and 0.3% CNT, all in weight percent) provided highly homogeneous CNT dispersion with very low area of agglomerates. The best dispersion quality was obtained with f-SWCNT/pluronic system, which provided very low agglomerate area (<0.5%), lower CNT bundle size, good quantity of well dispersed nanotubes (up to 50%) and excellent long term storage stability. Cementitious composites fabricated using SWCNT and f-SWCNT suspensions showed ductile fracture behavior and improvement in fracture energy up to 164%.

Details of the Collagen and Elastin Architecture in the Human Limbal Conjunctiva, Tenon's Capsule and Sclera Revealed by Two-Photon Excited Fluorescence Microscopy.

To investigate the architecture and distribution of collagen and elastin in human limbal conjunctiva, Tenon's capsule, and sclera. The limbal conjunctiva, Tenon's capsule, and sclera of human donor corneal buttons were imaged with an inverted two-photon excited fluorescence microscope. No fixation process was necessary. The laser (Ti:sapphire) was tuned at 850 nm for two-photon excitation. Backscatter signals of second harmonic generation (SHG) and autofluorescence (AF) were collected through a 425/30-nm and a 525/45-nm emission filter, respectively. Multiple, consecutive, and overlapping (z-stack) images were acquired. Collagen signals were collected with SHG, whereas elastin signals were collected with AF. The size and density of collagen bundles varied widely depending on depth: increasing from conjunctiva to sclera. In superficial image planes, collagen bundles were <10 μm in width, in a loose, disorganized arrangement. In deeper image planes (episclera and superficial sclera), collagen bundles were thicker (near 100 μm in width) and densely packed. Comparatively, elastin fibers were thinner and sparse. The orientation of elastin fibers was independent of collagen fibers in superficial layers; but in deep sclera, elastin fibers wove through collagen interbundle gaps. At the limbus, both collagen and elastin fibers were relatively compact and were distributed perpendicular to the limbal annulus. Two-photon excited fluorescence microscopy has enabled us to understand in greater detail the collagen and elastin architecture of the human limbal conjunctiva, Tenon's capsule, and sclera.

Chromosome mapping, molecular cloning and expression analysis of a novel gene response for leaf width in rice

Genetic analysis revealed that narrow leaf, small panicle, thin and slender stems as well as low fertility rate of an Indica rice variety were recessive traits and controlled by a single gene. Applying map-based cloning strategy, a novel narrow leaf gene, which was named nal11 was delimited to an interval of 58.3 kb between the InDel markers N10 and InD5016. There are 9 genes in the mapping interval, and only a heat shock DNAJ protein encode gene (Os07g09450) has a specific G to T SNP, which was occurred at the last base of the second exon of Os07g09450 in ZYX. 5′ and 3′ RACE result shown that there were two transcripts in NAL11, and the SNP in nal11 leads to a variable shear of mRNA. In addition, this type of mRNA alternative splicing together with a stop codon closely followed the SNP which caused termination of translation destroyed the DNAJ domain of nal11’s product. These results suggested that the heat shock DNAJ gene was most likely to be the candidate gene of nal11. The results of RT-PCR and real-time PCR further verified that the SNP in the ZYX-nal11 gene affects mRNA splicing pattern. Phenotype of ZYX may be caused by a statistically significant reduction in the total number of small veins in leaf, size and number of small vascular bundles and cells in stems, similar to several previous reported mutations. The basic molecular information we provide here will be useful for further investigations of the physiological function of the heat shock DNAJ gene, which will be helpful in better understanding the role of the DNAJ family in regulation of plant type traits such as leaf width of rice.

Bundle protocol for data delivery over highly asymmetric deep-space channels

Bundle Protocol is the main protocol of delay-/disruption-tolerant networking. Its store-and-forward mechanism and custody transfer option enable it to provide reliable file delivery services in a stressed communications environment. A typical application of Bundle Protocol is for data delivery in a deep-space communication environment, which is characterized by an extremely long signal propagation delay. However, little work has been seen in performance of Bundle Protocol transmission in deep-space communications. In this article, we present an overview of file transfer operation and performance of Bundle Protocol over a relay-based deepspace communication infrastructure characterized by highly asymmetric channel rates based on file transfer experiments. An optimal Bundle Protocol bundle size for the best transmission performance is also under investigation in this article.

Influence of Fiber Bundle Morphology on the Mechanical and Bonding Properties of Cotton Stalk and Mulberry Branch Reconstituted Square Lumber

The mechanical properties of natural fiber composites can be strengthened in the longitudinal direction if the fiber is formed in a parallel manner. Reconstituted cotton stalk lumber and mulberry branch lumber were fabricated using hot-press technology, and the effects of fiber morphology on their mechanical and bonding properties were investigated. The fiber bundle size had a great influence on the mechanical and bonding properties of the final products. The maximum specific modulus of rupture (MOR) and specific modulus of elasticity (MOE) of the reconstituted lumber were obtained for medium-size fiber bundles, and the maximum MOR and MOE of reconstituted cotton stalk lumber was 130.3 MPa·g-1·cm-3 and 12.9 GPa·g-1·cm-3, respectively. The maximum MOR and MOE of the mulberry branch lumber was 147.2 MPa·g-1·cm-3 and 14.7 GPa·g-1·cm-3, respectively. Mechanical interlocking structures in the lumber were observed via fluorescence microscopy, showing that phenol-formaldehyde adhesive had penetrated into several cell layers of the fiber bundle under heating and pressure. The adhesive penetration capacity was stronger when the fiber bundles were smaller in size and density. The reconstituted lumber fabricated from both materials exhibited excellent mechanical performance in the parallel direction. Therefore, reconstituted cotton stalk and mulberry branch lumber are attractive potential materials for the construction industry.

Effect of S doping on the critical current density and vortex dynamics in FeSe single crystal

We report a detailed study of the S doping effect on the critical current density, Jc, and vortex pinning in FeSe single crystal. The value of Jc for FeSe is found to be enhanced from ∼4×104A/cm2 at 2K under self-field to ∼6×104A/cm2 after S doping. Similar field decaying rates of Jc and the absence of fishtail effect in both FeSe and FeSe0.86S0.14 single crystals indicate the similar pinning mechanism for both crystals, i.e., the dominance of strong point-like pinning from nanometer-sized defects or imperfections. On the other hand, vortex dynamics study manifests that the S doping reduces the size of flux bundle and enhances the effective pinning energy, which may come from the lattice distortion caused by S doping.

ANATOMICAL AND MORPHOLOGICAL FEATURES OF STEMS AND LEAVES OF FILMY TYPES OF TRITICUM SPELTA L. AND T. DICOCCUM (SCHRANK) SCHUEBL.

Quantitative parameters of elements of the anatomical structure of the leaves and stems of two species of hulled wheats Triticum spelta and T. dicoccum in the phase of flowering – milky stage of plants that were grown under the same conditions were analysed. The aim of our study was to identify the characteristics of the internal structure of leaves and stems of cultural hulled wheat Triticum spelta and Triticum dicoccum , grown on the south steppe zone of Ukraine. The material for the research was fresh green leaves and shoots of winter wheat interstices of two types: T. spelta and T. dicoccum . Plants were grown in experimental plots of Selection and Genetics Institute - National Center of Seed and Cultivar (c. Odesa), the area which is located in the southern part of the Black Sea lowland in southern steppe areas in the Odesa region. To study the anatomical structure of the stem and leaves 5-7 plants of each species in the flowering stage – lactic ripeness were collected. Anatomical structure of plant material was studied in temporary preparations treated with a solution phloroglucine and 30 % hydrochloric acid. It was found that leaves of T dicoccum differed from T. spelta leaves by thicker mesophyll, loose arrangement of vascular bundles, fewer stomata. Stems of T. spelta are characterized by less wide ring of schlerenchyma with smaller vascular bundles than in T. dicoccum , and fewer vascular bundles in the parenchyma. Thus, in the investigated species of wheat there are some differences in the characteristics of the main elements of the anatomical structure of the stem, diameter, radius of cavity straw, the degree of mechanical tissue, the number of rows and the size of vascular bundles. Quantitative parameters of anatomical and morphological characteristics can be used to evaluate the genotype and physiological condition of plants.

Hydrodynamics and gas transfer performance of confined hollow fibre membrane modules with the aid of computational fluid dynamics

The use of gas permeable membranes for bubbleless aeration is of increasing interest due to the energy savings it affords in wastewater treatment applications. However, flow maldistributions are a major factor in the impedance of mass transfer efficiency. In this study, the effect of module configuration on the hydrodynamic conditions and gas transfer properties of various submerged hollow fibre bundles was investigated. Flow patterns and velocity profiles within fibre bundles were predicted numerically using computational fluid dynamics (CFD) and the model was validated by tracer-response experiments. In addition, the effect of fibre spacing and bundle size on the aeration rate of various modules was evaluated experimentally. Previous studies typically base performance evaluations on the liquid inlet velocity or an average velocity, an approach which neglects the effect of geometric features within modules. The use of validated CFD simulations provides more detailed information for performance assessment. It was shown that specific oxygen transfer rates declines significantly with increasing numbers of fibres in a bundle. However, the same trend was not observed when the fibre spacing is increased. A correlation was proposed for the prediction of the overall mass transfer coefficient utilizing the local velocity values obtained from the validated CFD model.

Enhanced carbon nanotube dispersion in 3YTZP/SWNTs composites and its effect on room temperature mechanical and electrical properties

In this work, several modifications of the colloidal processing technique and spark plasma sintering (SPS) to prepare yttria tetragonal zirconia composites (YTZP) with single walled carbon nanotubes (SWNT) have been tested with the aim of eliminating SWNT agglomerates. These modifications include high versus low energy ultrasonic agitation during colloidal processing, lyophilization of the 3YTZP/SWNT slurry and electrical insulation during sintering of the composites. Semi-quantitative microstructural characterization of the carbon nanotube distribution in the sintered composites showed that high energy ultrasonic agitation reduces drastically agglomerate size. Lyophilization of the mixed suspensions avoids SWNT bundle size growth. Combination of both produces an enhanced carbon nanotube network distribution along the grain boundaries (GB) due to the absence of carbon nanotube agglomerates and to a limited SWNT bundle size. This results in an increase of the real SWNT content in the GBs up to nominal SWNT content and therefore an enhanced SWNT efficiency in the composites. The agglomerate-free highly-dispersed composites exhibit a decrease in density together with grain size refinement, a decrease in room temperature hardness, an increase in flexural strength and a most significant increase in room temperature electrical conductivity. Improved SWNT distribution also lowers electrical percolation threshold to a very low level in SWNT ceramic composites, <1 vol% SWNT.