Thread-like Structures Research Articles

Van der Waals Effects on semiconductor clusters.

Van der Waals (vdW) interactions play an important role on semiconductors in nanoscale. Here, we utilized first-principles calculations based on density functional theory to demonstrate the growth mode transition from prolate to multiunit configurations for Gen (n = 10-50) clusters. In agreement with the injected ion drift tube techniques that "clusters with n < 70 can be thought of as loosely bound assemblies of small strongly bound fragments (such as Ge7 and Ge10 )," we found these stable fragments are connected by Ge6 , Ge9 , or Ge10 unit (from bulk diamond), via strong covalent bonds. Our calculated cations usually fragment to Ge7 and Ge10 clusters, in accordance with the experiment results that the spectra Ge7 and Ge10 correspond to the mass abundance spectra. By controlling a germanium cluster with vdW interactions parameters in the program or not, we found that the vdW effects strengthen the covalent bond from different units more strikingly than that in a single unit. With more bonds between units than the threadlike structures, the multiunit structures have larger vdW energies, explaining why the isolated nanowires are harder to produce. © 2015 Wiley Periodicals, Inc.

Scattering Function for Branched Wormlike Chains.

Wormlike or threadlike structures with local cylindrical geometry are abundantly found in nature and technical products. A thorough structural characterization in the bulk for a whole ensemble, however, is difficult. The inherent semiordered nature of the tortuous large-scale structure and especially the quantification of branching renders an assessment difficult. In the present work we introduce a hybrid function expressing the scattering intensities for X-rays, neutrons, or light in the small-angle regime for this system. The function is termed "hybrid" because it employs terms from different approaches. The large-scale structure is described via a Guinier term as well as a concomitant power-law expression in momentum transfer q taken from the so-called unified function. The local cylindrical shape, however, is taken into account through a form factor for cylinders from rigid-body modeling. In principle, the latter form factor can be replaced by an expression for any other regular body so that the new hybrid function is a versatile tool for studying hierarchical structures assembled from uniform subunits. The appropriateness and capability of the new function for cylindrical structures is exemplified using the example of a wormlike micellar system.

Comparison of the morphological characteristics of the threadlike structure observed in rat and swine

Comparison of the morphological characteristics of the threadlike structure observed in rat and swine

Protocol for Detecting the Primo Vascular System in the Lymph Ducts of Mice

The primo vascular system (PVS), which is the proposed conduit for the acupuncture Qi, is a complex network distributed throughout an animal's body. However, even with a microscope, it is not easily detectable because of its transparency. Thus, its existence is largely unknown in current anatomy. A convincing demonstration of its existence is needed. The lymph-primo vessel (PV), which is a subsystem of the PVS, is a very effective visual demonstration of the PVS. The lymph-PVS is a mobile threadlike structure floating in lymph ducts that has been observed in rabbits, rats, and mice by several independent teams. The involved techniques are novel and rather complicated; therefore, we have already provided detailed protocols for the surgery; for the injection of the staining dye; and for the detection, extraction, and identification of the PVS in rabbits and rats. However, the mouse is one of the most important laboratory animals used for various biomedical research purposes. For the convenience of researchers who wish to initiate the PVS experiments in mice, we provide a shortened version of the protocol, despite many similarities with previously published protocols. Thus, researcher can easily obtain the samples of the lymph-PVS of mice.

EFFECT OF ELASTICITY OF BOGER FLUIDS ON THE ATOMIZATION BEHAVIOR OF AN IMPINGING JET INJECTOR

Gelled propellants are of interest for rocket and ramjet propulsion systems because of their safety and performance benefits. During spray tests with doublets, such as on impinging jet injectors, it was observed that the breakup of the fluid sheet of several gels did not lead to the formation of droplets; instead, threadlike structures were formed. Such structures may cause a reduction in combustion efficiency and the accumulation of unburned material in the combustion chamber. The goal of the work presented here is to determine which physical properties influence thread formation. Spray tests were conducted with Boger fluids under atmospheric conditions concerning pressure and temperature with a like-on-like impinging jet injector. The range of injection velocities from 5 to over 70 m/s was studied. Images of the sprays were obtained with a shadowgraph technique. In order to obtain quantitative results from shadowgraph images, a code was implemented to determine a characteristic dimension of the threads. A clear correlation between the relaxation time, which is an indicator of the intensity of elastic effects, and the dimension of the obtained threads was observed. These results suggest that thread formation is caused by nonlinear elastic effects, while shear viscosity and surface tension do not seem to influence the formation of these structures.

Evidence for novel age-dependent network structures as a putative primo vascular network in the dura mater of the rat brain.

With chromium-hematoxylin staining, we found evidence for the existence of novel age-dependent network structures in the dura mater of rat brains. Under stereomicroscopy, we noticed that chromium-hematoxylin-stained threadlike structures, which were barely observable in 1-week-old rats, were networked in specific areas of the brain, for example, the lateral lobes and the cerebella, in 4-week-old rats. In 7-week-old rats, those structures were found to have become larger and better networked. With phase contrast microscopy, we found that in 1-week-old rats, chromium-hematoxylin-stained granules were scattered in the same areas of the brain in which the network structures would later be observed in the 4- and 7-week-old rats. Such age-dependent network structures were examined by using optical and transmission electron microscopy, and the following results were obtained. The scattered granules fused into networks with increasing age. Cross-sections of the age-dependent network structures demonstrated heavily-stained basophilic substructures. Transmission electron microscopy revealed the basophilic substructures to be clusters with high electron densities consisting of nanosized particles. We report these data as evidence for the existence of age-dependent network structures in the dura mater, we discuss their putative functions of age-dependent network structures beyond the general concept of the dura mater as a supporting matrix.

Identification of Primo-Vascular System in Abdominal Subcutaneous Tissue Layer of Rats

The primo-vascular system (PVS) is a novel network identified in various animal tissues. However, the PVS in subcutaneous tissue has not been well identified. Here, we examined the putative PVS on the surface of abdominal subcutaneous tissue in rats. Hemacolor staining revealed dark blue threadlike structures consisting of nodes and vessels, which were frequently observed bundled with blood vessels. The structure was filled with various immune cells including mast cells and WBCs. In the structure, there were inner spaces (20–60 µm) with low cellularity. Electron microscopy revealed a bundle structure and typical cytology common with the well-established organ surface PVS, which were different from those of the lymphatic vessel. Among several subcutaneous (sc) PVS tissues identified on the rat abdominal space, the most outstanding was the scPVS aligned along the ventral midline. The distribution pattern of nodes and vessels in the scPVS closely resembled that of the conception vessel meridian and its acupoints. In conclusion, our results newly revealed that the PVS is present in the abdominal subcutaneous tissue layer and indicate that the scPVS tissues are closely correlated with acupuncture meridians. Our findings will help to characterize the PVS in the other superficial tissues and its physiological roles.

0605 壁乱流における摩擦抵抗低減効果を有する蛍光修飾ポリマーの可視化

Skin-friction drag reduction effect by polymer additives in a turbulent channel flow is investigated by means of PIV and LIF measurements. We employed a fluorescently-labeled polymer in order to capture the polymer behavior in the flow. As a preliminary experiment, the fluorescently-labeled polymer is visualized in a rotating flow and compared with a dyed polymer. The fluorescently-labeled polymer shows to form thread-like structures for longer time than the dyed polymer. The PIV measurement of the turbulent channel flow with the dyed polymer shows the decrease of the Reynolds shear stress, which implies the skin-friction drag reduction.

Identification of a novel matrix protein that promotes biofilm maturation in Vibrio fischeri.

Bacteria form communities, termed biofilms, in which cells adhere to each other within a matrix, typically comprised of polysaccharides, proteins, and extracellular DNA. Biofilm formation by the marine bacterium Vibrio fischeri requires the Syp polysaccharide, but the involvement of matrix proteins is as yet unknown. Here we identified three genes, termed bmpA, -B, and -C (biofilm maturation protein), with overlapping functions in biofilm maturation. A triple bmpABC mutant, but not single or double mutants, was defective in producing wrinkled colonies, a form of biofilm. Surprisingly, the triple mutant was competent to form pellicles, another biofilm phenotype, but they generally lacked a three-dimensional architecture. Transmission electron microscopy revealed that the extracellular matrix of the bmp mutant contained electron-dense, thread-like structures that were also present in the wild type but lacking in syp mutant strains. We hypothesized that the bmp mutant produces the Syp polysaccharide but fails to produce/export a distinct matrix component. Indeed, a mixture of the bmp and syp mutants produced a wrinkled colony. Finally, BmpA could be detected in cell-free supernatants from disrupted pellicles. Thus, this work identifies a new matrix protein necessary for biofilm maturation by V. fischeri and, based on the conservation of bmp, potentially other microbes.

Rice SNF2 family helicase ENL1 is essential for syncytial endosperm development.

The endosperm of cereal grains represents the most important source of human nutrition. In addition, the endosperm provides many investigatory opportunities for biologists because of the unique processes that occur during its ontogeny, including syncytial development at early stages. Rice endospermless 1 (enl1) develops seeds lacking an endosperm but carrying a functional embryo. The enl1 endosperm produces strikingly enlarged amoeboid nuclei. These abnormal nuclei result from a malfunction in mitotic chromosomal segregation during syncytial endosperm development. The molecular identification of the causal gene revealed that ENL1 encodes an SNF2 helicase family protein that is orthologous to human Plk1-Interacting Checkpoint Helicase (PICH), which has been implicated in the resolution of persistent DNA catenation during anaphase. ENL1-Venus (enhanced yellow fluorescent protein (YFP)) localizes to the cytoplasm during interphase but moves to the chromosome arms during mitosis. ENL1-Venus is also detected on a thread-like structure that connects separating sister chromosomes. These observations indicate the functional conservation between PICH and ENL1 and confirm the proposed role of PICH. Although ENL1 dysfunction also affects karyokinesis in the root meristem, enl1 plants can grow in a field and set seeds, indicating that its indispensability is tissue-dependent. Notably, despite the wide conservation of ENL1/PICH among eukaryotes, the loss of function of the ENL1 ortholog in Arabidopsis (CHR24) has only marginal effects on endosperm nuclei and results in normal plant development. Our results suggest that ENL1 is endowed with an indispensable role to secure the extremely rapid nuclear cycle during syncytial endosperm development in rice.

A new user-adapted search haptic algorithm to navigate along filiform structures.

One of the mayor research challenges of this century is the understanding of the human brain. Regarding this field line, simulation based research is gaining importance. A large amount of money is being spent in huge international projects such as The Human Brain Project [1] and The Blue Brain [2]. The behavior of the brain and, therefore, the behavior of brain simulations depend to a large extend on the neural topology. Neural elements are organized in a connected, dense, complex network of thread-like (i.e., filiform) structures. The analysis of a computer-based simulation using just the visual modality is a highly complex task due to the complexity of the neural topology and the large amounts of multi-variable and multi-modal data generated by computer simulations. In this paper, we propose the use of haptic devices to aid in the navigation along these neural structures, helping neurobiologists in the analysis of neural network topologies. However, haptic navigation constrained to complex filiform networks entails problems when these structures have high frequency features, noise and/or complex branching nodes. We address these issues by presenting a new user-adapted search haptic method that uses the forces exerted by the users to infer their intentions. In addition, we propose a specific calibration technique to adapt the haptic navigation to the user's skills and to the data. We validate this approach through a perceptual study. Finally, we show in this paper the application of our method to the analysis of dense and complex filiform structures in the neurobiology context. Additionally, our technique could be applied to other problems such as electronic circuits and graph exploration.

Tailored design of electrospun composite nanofibers with staged release of multiple angiogenic growth factors for chronic wound healing

The objective of this research study is to develop a collagen (Col) and hyaluronic acid (HA) inter-stacking nanofibrous skin equivalent substitute with the programmable release of multiple angiogenic growth factors (vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF) and endothelial growth factor (EGF)) either directly embedded in the nanofibers or encapsulated in the gelatin nanoparticles (GNs) by electrospinning technology. The delivery of EGF and bFGF in the early stage is expected to accelerate epithelialization and vasculature sprouting, while the release of PDGF and VEGF in the late stage is with the aim of inducing blood vessels maturation. The physiochemical characterizations indicate that the Col–HA–GN nanofibrous membrane possesses mechanical properties similar to human native skin. The design of a particle-in-fiber structure allows growth factors for slow controlled release up to 1month. Cultured on biodegradable Col–HA membrane with four kinds of growth factors (Col–HA w/4GF), endothelial cells not only increase in growth rate but also form a better network with a thread-like tubular structure. The therapeutic effect of Col–HA w/4GF membrane on streptozotocin (STZ)-induced diabetic rats reveals an accelerated wound closure rate, together with elevated collagen deposition and enhanced maturation of vessels, as revealed by Masson’s trichrome stain and immunohistochemical analysis, respectively. From the above, the electrospun Col–HA–GN composite nanofibrous skin substitute with a stage-wise release pattern of multiple angiogenic factors could be a promising bioengineered construct for chronic wound healing in skin tissue regeneration.

Advection of shear-induced surfactant threads and turbulent drag reduction

Surfactant solutions containing wormlike micelles often show complex structural changes in laminar shear flow. These structural changes produce anomalous rheological phenomena in which the shear induced structure (hereafter SIS) increases the viscosity of surfactant solutions. In turbulent shear flow, dilute solutions of 5 nm diameter and micron length wormlike micelles reduce frictional drag. It has been speculated that this drag reduction is related to wormlike micelles or SIS, although to date there have been no studies that have made their direct link to drag reduction in turbulent flow. The mechanism of drag reduction and the role of the micellar structure remain unclear. Here, we identify SIS with a long (several centimeters), threadlike structure. The threads form a gel-like phase under shear, which is clearly separated from the surrounding fluid. The threads breakdown at high shear stresses and disappear at the same time as the drag reduction does. The correlation between the existence of surfactant threads and turbulent drag reduction is discussed.

Comparative floral structure and systematics in the balsaminoid clade including Balsaminaceae, Marcgraviaceae and Tetrameristaceae (Ericales)

Based on molecular phylogenetic studies, Balsaminaceae, Tetrameristaceae (including Pellicieraceae) and Marcgraviaceae form the strongly supported first branching clade in the asterid order Ericales. Marcgraviaceae and Tetrameristaceae were proposed to be closely related in pre-molecular studies, but the systematic position of Balsaminaceae has been controversial for some time and a relationship with the other two families was never suggested in pre-molecular/pre-cladistic times. However, interfamilial relationships in the clade are still unclear because of conflicting phylogenetic hypotheses from molecular analyses. In order to assess the validity of these molecular hypotheses from a morphological point of view, the floral morphology, anatomy and histology of Balsaminaceae, Tetrameristaceae and Marcgraviaceae are comparatively studied in detail. In addition, earlier literature is reviewed. The monophyly of the balsaminoid clade is strongly supported by floral structure, and a series of potential floral synapomorphies is identified for the clade. Prominent features shared by the three families include broad and dorsiventrally flattened filaments, thread-like structures lining the stomia of dehisced anthers, secretory inner morphological surfaces of the gynoecium, ovules intermediate between uni- and bitegmic, incompletely tenuinucellar ovules, fruits with persistent style and stigma, seeds lacking endosperm and several anatomical/histological traits. The families are also distinctive because the bracts and/or sepals are petaloid and nectariferous. Further, the floral structure supports a sister group relationship between Balsaminaceae and Tetrameristaceae rather than any of the other possible interfamilial relationships. These two families share a caducous calyx, post-genital fusion/coherence of filaments and ovary surface, latrorse anther dehiscence, commissural carpel lobes and ovules with a thickened funiculus and a constricted chalazal region. The occurrence of these features in Ericales is discussed. Future structural studies in other ericalean lineages and additional molecular studies are needed to further test these features with respect to their systematic value for the balsaminoid clade. Some may turn out to be true synapomorphies, whereas others may be recognized as plesiomorphies, as they may be more widely spread in Ericales than currently thought. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173, 325–386.

Primo Vascular System Floating in Lymph Ducts of Rats

An epoch-making development in the gross anatomy of the lymph system has emerged: the observation of the primo vascular system (PVS), which is a threadlike structure floating in lymph ducts. The PVS, which was proposed as the conduit for the acupuncture Qi, is a complex network distributed throughout an animal's body. The lymph-PVS, which is a subsystem of the PVS, is one of the most convincing visual demonstrations of the PVS. Because its existence is not easily demonstrated, even with a microscope, due to its transparency, in current anatomy its existence is largely unknown despite its potential significance in physiology and medicine. The lymph-PVS has been observed in rabbits, rats, and mice by several independent teams. Because the involved techniques are rather complicated, we provide detailed protocols for surgery, for injection of the staining dye, and for detection, extraction, and identification of the PVS in a rat.

The crystallization kinetics of potassium chloride in the presence of additives with common ions

In this study, the growth and dissolution rates of closely sized KCl crystals that were classified with respect to their separation voltages in an electrostatic separator were investigated in the presence of K2SO4, CH3COOK, NH4Cl and BaCl2 additives, having common cations or anions. Separation voltages were taken as a measure of surface potential. The experiments were carried out in a typical stagnant medium type single crystal measurement system.From experimental results it is observed that thread-like growth behaviors resulting from surface nucleation were dominant and dead zones where there was no growth or dissolution did always exist. For additives having common cation, it was found that the growth in the thread-like structure increases with the increase of surface potential. It was also found that, additives having common anions, initially led to decrease and neutralize the surface potential, then oppositely charged the crystal surface, when the crystal growth/dissolution behavior changes were considered. This study obviously proved that, crystal growth and dissolution behaviors can be controlled by changing the surface potentials of crystals by using additives having common ions.

ARE GIANT TORNADOES THE LEGS OF SOLAR PROMINENCES?

Observations in the 171 AA channel of the Atmospheric Imaging Assembly of the space-borne Solar Dynamics Observatory show tornadoes-like features in the atmosphere of the Sun. These giant tornadoes appear as dark, elongated and apparently rotating structures in front of a brighter background. This phenomenon is thought to be produced by rotating magnetic field structures that extend throughout the atmosphere. We characterize giant tornadoes through a statistical analysis of properties like spatial distribution, lifetimes, and sizes. A total number of 201 giant tornadoes are detected in a period of 25 days, suggesting that on average about 30 events are present across the whole Sun at a time close to solar maximum. Most tornadoes appear in groups and seem to form the legs of prominences, thus serving as plasma sources/sinks. Additional Halpha observations with the Swedish 1-m Solar Telescope imply that giant tornadoes rotate as a structure although clearly exhibiting a thread-like structure. We observe tornado groups that grow prior to the eruption of the connected prominence. The rotation of the tornadoes may progressively twist the magnetic structure of the prominence until it becomes unstable and erupts. Finally, we investigate the potential relation of giant tornadoes to other phenomena, which may also be produced by rotating magnetic field structures. A comparison to cyclones, magnetic tornadoes and spicules implies that such events are more abundant and short-lived the smaller they are. This comparison might help to construct a power law for the effective atmospheric heating contribution as function of spatial scale.

Self-assembly of two-patch particles in solution: a Brownian dynamics simulation study

We study the self-assembly behaviour of two-patch particles with D∞h symmetry by using Brownian dynamics simulations. The self-assembly process of two-patch particles with diverse patch coverage in two selective solvent conditions is investigated. The patchy particles in a solvent that is bad for patches but good for matrix form linear thread-like structures with low patch coverage, whereas they form 3D network structures with relatively high patch coverage on surface. For patchy particles in a solvent which is good for patches but bad for body, monolayer structures are obtained at high patch coverage, and some cluster structures emerge when surface patch coverage is low.

THE KARYOSPHERE IN LATE OOGENESIS OF FROGS

SUMMARY Late oogenesis of the lake frog Rana ridibunda Pallas, 1771 and Rana temporaria Linnaeus, 1758 was investigated by means of morphological and cytochemical methods. It was shown that in the period of late vitellogenesis during the autumn and winter months the nuclear structures (lampbrush chromosomes and multiple nucleoli) assemble in the centre of the nucleus occupying a large area (up to 180μ in diameter) and forming a karyosphere. Spherical nucleoli are located along the periphery of the karyosphere and they form the capsule of karyosphere. These nucleoli are supplied with thread-like granular structures. Nearer the centre of the karyosphere, typical lampbrush chromosomes are found. The centre of the karyosphere is occupied by a great number of polymorphous bodies and ring structures, containing DNA. Polymorphous bodies may reach from 5 to 30–50 μ in length and ring structures from 1 to 3 μ in diameter. It was shown that in the course of oogenesis the polymorphous bodies become substituted by th...

Water vapor nucleation on a crystal surface in a strong electric field

Water vapor nucleation at 260 K in a transverse electric field has been simulated by the Monte Carlo method under conditions corresponding to an internal wall of a spatially extended microcrack in a silver iodide crystal. The bicanonical statistical ensemble method has been employed to calculate, at the molecular level, the free energy of addition and the work of formation of dense phase nuclei in fields with different strengths. In a moderate field, the film mechanism of nucleation characterized by intense distortions on the film surface remains preserved. A domain structure of a film layer in contact with the surface exhibits a high stability with respect to an external field and remains preserved until the film is completely destroyed. In a strong electric field, the nucleation mechanism is fundamentally changed; i.e., the film is destroyed to yield threadlike structures. Therewith, the area of the contact with the surface drastically decreases. The orientation of nanothreads along the electric field lines overcomes a low free energy barrier. The point of equilibrium of nanothreads with vapor depends on the presence of hydrogen bonds, while their stability is determined by longer-range dipole-dipole interactions. The observed form of existence of the condensate as polarized nanothreads seems to be analogous to the superpolarized state previously revealed for water microdroplets, the transition to which has the character of the first-order phase transition.