Separate Filaments Research Articles

Control of Femtosecond Filamentation by Means of the Alignment of Gas Molecules by Short-Wavelength Infrared Laser Pulses

It has been demonstrated experimentally that both the single and multiple filamentation of a femtosecond laser pulse in gaseous nitrogen can be controlled by means of the nonadiabatic alignment of molecules by 1400-nm pulses. The spectral shifts and change in the duration of a pulse caused by changes in the refractive index in the revival regions of a rotational wave packet have been detected. The stable and reproducible localization of radiation into separate filaments with the subdiffraction divergence and broadening of the spectrum by more than an octave has been observed in the multiple filamentation regime upon the alignment of molecules in the direction perpendicular to the pulse polarization.

Endoplura jejuensis sp. nov. and Endoplura koreana sp. nov. (Ralfsiales, Phaeophyceae) from Korea based on molecular and morphological analyses

The crustose brown algal genus Endoplura has been known as a monotypic genus characterized by its intercalary plurangial reproductive structures composed of 2–4 separate parallel filaments terminated by 2–5 sterile cells and by containing several to many chloroplasts per cell. In this study, Endoplura jejuensis sp. nov. and E. koreana sp. nov. from Korea are newly described based on molecular and morphological analyses. Our phylogenetic analyses of the rbcL gene reveal that E. jejuensis sp. nov. and E. koreana sp. nov. are placed in the same clade with “E. aurea” from Japan with a strong bootstrap supporting value. E. jejuensis is characterized by small and light to dark brown crustose thalli of less than 1 cm diameter, tufts of hairs arising from the basal disc, plurangia composed mostly of two separate parallel reproductive filaments terminated by 2–4 sterile cells, and sessile unangia each with a single paraphysis. E. koreana is distinguished by olive or yellowish-brown crustose thalli of up to 3 cm diameter, tufts of hairs arising from the basal disc, and apical parts of erect filaments, plurangia with 2–5 separate reproductive filaments terminated by 2–8 sterile cells, and sessile unangia with 1–2 paraphyses. Our studies also show that “E. aurea” specimens from Japan may be recognized to be a different species from other Endoplura species.

Therapy with new generation of biodegradable and bioconjugate 3D printed artificial gastrointestinal lumen.

Objective(s):Many patients die due to vascular, gastrointestinal lumen problems, and coronary heart diseases. Synthetic vessels that are made of biodegradable-nanofiber polymers have significant properties such as proper biodegradability and efficient physical properties such as high strength and flexibility. Some of the best options for supporting cells in soft tissue engineering and design are applications of thermoplastic polyurethane polymer in the venous tissue. In this study, the first nanoparticle-reinforced polymeric artificial prosthesis was designed and tested to be used in the human body.Materials and Methods: In this study, artificial gastrointestinal lumen were fabricated and prepared using a 3D printer. To improve cell adhesion, wettability properties and mechanical stability of elastin biopolymer with magnetic nanoparticles (MNPs) as well as single-walled carbon nanotubes (SWCNT) were prepared as separate filaments. MNPs were made in 5–7 mm sizes and then examined for mechanical, biological, and hyperthermia properties. Then, the obtained results of the gastrointestinal lumen were simulated using the Abaqus software package with a three-branch. The results were evaluated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) for morphology and phase analysis. Results:The obtained results of the designed vessels showed remarkable improvement in mechanical properties of the SWCNT vessels and hyperthermia properties of the vessels containing the MNPs. The results of computational fluid dynamics (CFD) analysis showed that the artificial vessels had lower shear stress at the output. Conclusion:Five-mm MNP containing vessels showed noticeable chemical and biological properties along with ideal magnetic results in the treatment of thrombosis and vascular obstruction.

Fine Filament Structure of a Quiescent Solar Prominence

A theoretical model of a cold and dense isolated solar prominence is presented. The thermodynamic parameters of a filament (gas pressure, density and temperature) are calculated from a specified magnetic field structure. The filament lies above the photospheric polarization separation line and its magnetic field falls off rapidly with distance from the axis, so that the total electric current along the axis of the filament equals zero. The prominence has a helical magnetic field structure divided into separate thin filaments. The density and temperature distributions of the prominence derived from the equilibrium conditions for this kind of magnetic field correspond well to the known observed parameters.

Extracting Filaments Based on Morphology Components Analysis from Radio Astronomical Images

Filaments are a type of wide-existing astronomical structure. It is a challenge to separate filaments from radio astronomical images, because their radiation is usually weak. What is more, filaments often mix with bright objects, e.g., stars, which makes it difficult to separate them. In order to extract filaments, A. Men’shchikov proposed a method “getfilaments” to find filaments automatically. However, the algorithm removed tiny structures by counting connected pixels number simply. Removing tiny structures based on local information might remove some part of the filaments because filaments in radio astronomical image are usually weak. In order to solve this problem, we applied morphology components analysis (MCA) to process each singe spatial scale image and proposed a filaments extraction algorithm based on MCA. MCA uses a dictionary whose elements can be wavelet translation function, curvelet translation function, or ridgelet translation function to decompose images. Different selection of elements in the dictionary can get different morphology components of the spatial scale image. By using MCA, we can get line structure, gauss sources, and other structures in spatial scale images and exclude the components that are not related to filaments. Experimental results showed that our proposed method based on MCA is effective in extracting filaments from real radio astronomical images, and images processed by our method have higher peak signal-to-noise ratio (PSNR).

Annual Gametogenesis Patterns in Two High-Latitude Corals, Alveopora japonica and Oulastrea crispata, from Jeju Island, South Korea

Sexual reproduction in corals is pivotal for the survival of populations in the face of climate change. Off Jeju Island, which lies off the south coast of Korea, a high-latitude scleractinian coral, Alveopora japonica, has experienced a population explosion over the past couple of decades (at 5–15 m depths). A second species, Oulastrea crispata, which is generally present at high latitudes and extreme environments, has a stable population and dominates in the shallow subtidal waters of southern Jeju. This study examined the annual gametogenesis patterns of A. japonica off the north (33°24′N, 126°13′E) and south (33°14′N, 126°36′E) coasts of Jeju Island, and of O. crispata in the south. Histological analysis revealed that the oogonia and spermatogonia in A. japonica developed in separate mesenterial filaments, while the gonads in O. crispata developed in the same filament. Alveopora japonica had the same brooding period during late summer and early fall (Aug–Sep 2015) at both sites. The spawning period of O. crispata was also during late summer and early fall. Brooding in A. japonica was concordant with previous observations of its planula during the brooding period. This study provides the first data on the timing of reproduction of these two high-latitude corals from Jeju Island, which may help our understanding of the population dynamics of corals in other high-latitude environments.

Magnetic Islands and Current Filamentation in Tokamaks

It is well known that heat exchange between the hot plasma and solid wall of a magnetic fusion reactor (tokamak or stellarator) depends, to a great extent, on local disturbances of its magnetic configuration, which occur under the action of resonant magnetic perturbations. One possible reason for their development in tokamaks is splitting of an originally axisymmetric current channel into separate filaments. Among negative consequences of such filamentation, there are spatial modulations of the plasma density and temperature, which can considerably increase local heat loads on the tokamak intrachamber elements. This study draws attention to the fact that one of the most dangerous manifestations of current filamentation in tokamaks is the formation of so-called “positive” magnetic islands, which are clearly observed during the development of internal disruptions in the form of “hot spots”—local hot dense helical plasma structures formed in the central region of the plasma column just before the major disruption. An increase in the heating efficiency and improvement of plasma confinement within magnetic islands (which are, in fact, closed magnetic configurations) could explain energy balance in such structures. In this article, stability of such structures and possible sources of initial current disturbances initiating their formation are discussed as illustratively as possible on the basis the initial physical principles, which, in the author’s opinion, can be useful for the experimenters who start solving problems of plasma–wall heat exchange under real tokamak conditions. A number of the well-known experimental observations that can be explained in the framework of this concept are discussed. It is argued that the concept of positive magnetic islands makes it possible to interrelate the sequence of MHD events resulting in the tokamak major disruption.

Self-sustained volume discharge in mixtures of SF6 with hydrocarbons, hydrogen and deuterium for non-chain HF(DF) lasers

This paper reports on the comprehensive studies on a self-sustained volume discharge in SF6-based working media for electrochemical non-chain hydrogen fluoride (deuterium fluoride) lasers. The majority of the experimental results have first been obtained at various values of gas pressure for the discharge gaps with a large interelectrode distance, including plane electrode systems with a strong enhancement of the edge electric field. Some special features of the observed physical phenomena are explained using the developed adequate mathematical models. In particular, a radically new mechanism of the ionization instability in SF6-based mixtures at an intermediate pressure has been first considered and a relevant mathematical theory was developed. On this basis, the experimentally observable break-up of the discharge current into separate filaments in a laser-heated SF6-mixture was qualitatively explained. Some practical applications and recommendations have also been drawn from the performed studies.

Constraints on Cosmic-ray Acceleration Efficiency in Balmer Shocks of Two Young Type Ia Supernova Remnants in the Large Magellanic Cloud

Abstract We present results from an optical study of two young Balmer-dominated remnants of SNIa in the Large Magellanic Cloud, 0509−67.5 and 0519−69.0, in an attempt to search for signatures of efficient cosmic-ray (CR) acceleration. We combine proper motion measurements with corresponding optical spectroscopic measurements of the Hα line at multiple rim positions from VLT/FORS2 and SALT/RSS and compare our results to published Balmer shock models. Analyses of the optical spectra result in broad Hα widths in the range of 1800–4000 km s−1 for 12 separate Balmer-dominated filaments that show no evidence for forbidden line emission; the corresponding shock speeds from proper motion measurements from HST span a range of 1700–8500 km s−1. Our measured values of shock speeds and broad Hα widths in 0509−67.5 and 0519−69.0 are fit well with a Balmer shock model that does not include effects of efficient CR acceleration. We determine an upper limit of 7%/χ (95% confidence) on the CR acceleration efficiency for our ensemble of data points, where χ is the ionization fraction of the pre-shock gas. The upper limits on the individual remnants are 6%/χ (0509−67.5) and 11%/χ (0519−69.0). These upper limits are below the integrated CR acceleration efficiency in the Tycho supernova remnant, where the shocks predominantly show little Hα emission, indicating that Balmer-dominated shocks are not efficient CR accelerators.

OGT (O-GlcNAc Transferase) Selectively Modifies Multiple Residues Unique to Lamin A.

The LMNA gene encodes lamins A and C with key roles in nuclear structure, signaling, gene regulation, and genome integrity. Mutations in LMNA cause over 12 diseases (‘laminopathies’). Lamins A and C are identical for their first 566 residues. However, they form separate filaments in vivo, with apparently distinct roles. We report that lamin A is β-O-linked N-acetylglucosamine-(O-GlcNAc)-modified in human hepatoma (Huh7) cells and in mouse liver. In vitro assays with purified O-GlcNAc transferase (OGT) enzyme showed robust O-GlcNAcylation of recombinant mature lamin A tails (residues 385–646), with no detectable modification of lamin B1, lamin C, or ‘progerin’ (Δ50) tails. Using mass spectrometry, we identified 11 O-GlcNAc sites in a ‘sweet spot’ unique to lamin A, with up to seven sugars per peptide. Most sites were unpredicted by current algorithms. Double-mutant (S612A/T643A) lamin A tails were still robustly O-GlcNAc-modified at seven sites. By contrast, O-GlcNAcylation was undetectable on tails bearing deletion Δ50, which causes Hutchinson–Gilford progeria syndrome, and greatly reduced by deletion Δ35. We conclude that residues deleted in progeria are required for substrate recognition and/or modification by OGT in vitro. Interestingly, deletion Δ35, which does not remove the majority of identified O-GlcNAc sites, does remove potential OGT-association motifs (lamin A residues 622–625 and 639–645) homologous to that in mouse Tet1. These biochemical results are significant because they identify a novel molecular pathway that may profoundly influence lamin A function. The hypothesis that lamin A is selectively regulated by OGT warrants future testing in vivo, along with two predictions: genetic variants may contribute to disease by perturbing OGT-dependent regulation, and nutrient or other stresses might cause OGT to misregulate wildtype lamin A.

The catalytic stability of TiO2-shell/Ni-core catalysts for CO2 reforming of CH4

Bare and TiO2-coated Ni particles were used as catalysts for the CO2 reforming of CH4 (CRM) reaction at 800°C and TiO2 layers with two different thicknesses were prepared by atomic layer deposition (ALD). We focused on the deactivation mechanism of Ni-based catalysts upon long-term operation. All of the catalysts showed a decrease in the catalytic activity as a function of the reaction time for 160h, and the TiO2-coated Ni showed a less pronounced decrease in the catalytic activity in comparison to that of the bare Ni catalyst. The graphitic carbon layers that have been formed on the Ni particles during the reaction are suggested to be responsible for the deactivation and the additional TiO2 layer facilitated the formation of separate carbon filaments rather than the graphitic layer on the Ni, reducing the possibility of the deposited carbon layers to cover and poison the Ni active sites of catalysts. The fabrication of core-shell structures of metal and oxide by ALD can be a useful approach for the synthesis of heterogeneous catalysts, for which not only high activity, but also enhanced stability at an elevated temperature can be achieved.

Explaining the effects of processing on the electrical properties of PEDOT:PSS

By simultaneously measuring the Seebeck coefficient and the conductivity in differently processed PEDOT:PSS films, fundamental understanding is gained on how commonly used processing methods improve the conductivity of PEDOT:PSS. Use of a high boiling solvent (HBS) enhances the conductivity by 3 orders of magnitude, as is well-known. Simultaneously, the Seebeck coefficient S remains largely unaffected, which is shown to imply that the conductivity is improved by enhanced connectivity between PEDOT-rich filaments within the film, rather than by improved conductivity of the separate PEDOT filaments. Post-treatment of PEDOT:PSS films by washing with H2SO4 leads to a similarly enhanced conductivity and a significant reduction in the layer thickness. This reduction strikingly corresponds to the initial PSS ratio in the PEDOT:PSS films, which suggests removal and replacement of PSS in PEDOT:PSS by HSO4− or SO42− after washing. Like for the HBS treatment, this improves the connectivity between PEDOT filaments. Depending on whether the H2SO4 treatment is or is not preceded by an HBS treatment also the intra-filament transport is affected. We show that by characterization of S and σ it is possible to obtain more fundamental understanding of the effects of processing on the (thermo)electrical characteristics of PEDOT:PSS.

Puntalama İşlemi Parametrelerinin Sentetik Filament İplik Mukavemetine Etkisi

Intermingling is one of the best alternative methods to make the filament yarns more resistant against high volume stress. This technique has started to replace conventional methods such as sizing and twisting. The intermingling process mixes multifilament yarns along with entanglement points and open parts by turns throughout the length of the yarns. This process makes tensile value of multifilament yarns entirely different from the compo-nent of separate filaments. Knot numbers and stability are generally mentioned to describe the intermingling quality in a multifilament yarn. In accordance with these parameters, statistical results demonstrated that machine speed and yarn type have a statistically significant effect on the knot number and tensile strength; however singly machine speed parameter has no considerable effect on the tensile strength. This study tries to define the effect of commin-gling on the filament yarn strength.

Dust-acoustic filamentation of a current-driven dusty plasma

The thermal motion effect of charged particles in the filamentation of a current-driven dusty plasma in the dust-acoustic frequency region is investigated by using the Lorentz transformed conductivity of the dusty plasma components and the total dielectric permittivity tensor of the dusty plasma in the laboratory frame. Obtaining the dispersion relation for dust-acoustic waves and considering the filamentation instability, the establishment time of the filamentation structure and the instability development threshold are derived. Moreover, it is shown that the current layer divides into separate current filaments.

PENETRATING THE HOMUNCULUS—NEAR-INFRARED ADAPTIVE OPTICS IMAGES OF ETA CARINAE

Near-infrared adaptive optics imaging with NICI and NaCO reveal what appears to be a three-winged or lobed pattern, the "butterfly nebula", outlined by bright Br$\gamma$ and H$_{2}$ emission and light scattered by dust. In contrast, the [Fe II] emission does not follow the outline of the wings, but shows an extended bipolar distribution which is tracing the Little Homunculus ejected in $\eta$ Car's second or lesser eruption in the 1890's. Proper motions measured from the combined NICI and NaCO images together with radial velocities show that the knots and filaments that define the bright rims of the butterfly were ejected at two different epochs corresponding approximately to the great eruption and the second eruption. Most of the material is spatially distributed 10$\arcdeg$ to 20$\arcdeg$ above and below the equatorial plane apparently behind the Little Homunculus and the larger SE lobe. The equatorial debris either has a wide opening angle or the clumps were ejected at different latitudes relative to the plane. The butterfly is not a coherent physical structure or equatorial torus but spatially separate clumps and filaments ejected at different times, and now 2000 to 4000 AU from the star.

Detailed Analysis of the Dynein Stepping Mechanism using Multicolor Tracking

Cytoplasmic dynein is a motor protein that moves processively towards the microtubule minus end. To characterize dynein's step size at both limiting (5 µM) and saturating (1 mM) ATP concentrations, we have improved the temporal resolution of FIONA to 2 milliseconds and tracked the movement of single yeast cytoplasmic dynein motors, each labeled with one quantum dot. In contrast to kinesin, dynein's step size is highly variable, and backwards and sideways steps are frequently observed. As the tail domain takes ∼8 nm steps, the heads advance by taking both short (∼8 nm) and long (∼16 nm) steps. These data indicate that the heads do not move in a strictly alternating manner, as is the case with kinesin and myosin. To further characterize how the dynein heads move relative to each other, we have tracked the movement of both heads simultaneously. To precisely measure the head-head separation vector, we have developed novel small quantum dots (10 nm diameter) that specifically attach to each dynein head. The fluorescent signals of the differently-colored quantum dots attached to dynein are then registered with 2 nm precision. Using this technique, we find the heads to be widely separated, mostly in the off-axis, indicating that the two heads walk along separate filaments. Our two-color stepping data also show that the dynein heads advance mostly by taking alternating steps, as is the case with kinesin. However, the heads may also move independently of each other, and one head may take multiple steps before its partner moves forward. Both the leading head and the trailing head may initiate a step. Taken together, these unprecedented behaviors indicate that cytoplasmic dynein achieves processive movement via a mechanism unique among the molecular motors.

MULTI-STRAND CORONAL LOOP MODEL AND FILTER-RATIO ANALYSIS

We model a coronal loop as a bundle of seven separate strands or filaments. Each of the loop strands used in this model can independently be heated (near their left footpoints) by Alfv\'en/ion-cyclotron waves via wave-particle interactions. The Alfv\'en waves are assumed to penetrate the strands from their footpoints, at which we consider different wave energy inputs. As a result, the loop strands can have different heating profiles, and the differential heating can lead to a varying cross-field temperature in the total coronal loop. The simulation of TRACE observations by means of this loop model implies two uniform temperatures along the loop length, one inferred from the 171:195 filter ratio and the other from the 171:284 ratio. The reproduced flat temperature profiles are consistent with those inferred from the observed EUV coronal loops. According to our model, the flat temperature profile is a consequence of the coronal loop consisting of filaments, which have different temperatures but almost similar emission measures in the cross-field direction. Furthermore, when we assume certain errors in the simulated loop emissions (e.g., due to photometric uncertainties in the TRACE filters) and use the triple-filter analysis, our simulated loop conditions become consistent with those of an isothermal plasma. This implies that the use of TRACE/EIT triple filters for observation of a warm coronal loop may not help in determining whether the cross-field isothermal assumption is satisfied or not.

Cytoskeletal tropomyosin Tm5NM1 is required for normal excitation-contraction coupling in skeletal muscle.

The functional diversity of the actin microfilaments relies in part on the actin binding protein tropomyosin (Tm). The muscle-specific Tms regulate actin-myosin interactions and hence contraction. However, there is less known about the roles of the numerous cytoskeletal isoforms. We have shown previously that a cytoskeletal Tm, Tm5NM1, defines a Z-line adjacent cytoskeleton in skeletal muscle. Recently, we identified a second cytoskeletal Tm in this region, Tm4. Here we show that Tm4 and Tm5NM1 define separate actin filaments; the former associated with the terminal sarcoplasmic reticulum (SR) and other tubulovesicular structures. In skeletal muscles of Tm5NM1 knockout (KO) mice, Tm4 localization was unchanged, demonstrating the specificity of the membrane association. Tm5NM1 KO muscles exhibit potentiation of T-system depolarization and decreased force rundown with repeated T-tubule depolarizations consistent with altered T-tubule function. These results indicate that a Tm5NM1-defined actin cytoskeleton is required for the normal excitation-contraction coupling in skeletal muscle.

Dynamic movement of actin-like proteins within bacterial cells.

Actin proteins are present in pro- and eukaryotes, and have been shown to perform motor-like functions in eukaryotic cells in a variety of processes. Bacterial actin homologues are essential for cell viability and have been implicated in the formation of rod cell shape, as well as in segregation of plasmids and whole chromosomes. We have generated functional green fluorescent protein fusions of all three Bacillus subtilis actin-like proteins (MreB, Mbl and MreBH), and show that all three proteins form helical filaments underneath the cell membrane, the pattern of which is distinct for each protein. Time-lapse microscopy showed that the filaments are highly dynamic structures. A number of separate filaments of MreB and Mbl continuously move through the cell along helical tracks underneath the cell membrane. The speed of extension of the growing end of filaments is within the range of known actin polymerization (0.1 microm/s), generating a potential poleward or centreward pushing velocity at 0.24 microm/min for MreB or Mbl, respectively. During nutritional downshift and a block in topoisomerase IV activity, the filaments rapidly disintegrated, showing that movement occurs only in growing cells. Contrary to Mbl and MreBH filaments, MreB filaments were generally absent in cells lacking DNA, providing a further distinction between the three orthologues.

The intertidal marine lichen formed by the pyrenomycete fungus Verrucaria tavaresiae (Ascomycotina) and the brown alga Petroderma maculiforme (Phaeophyceae): thallus organization and symbiont interaction

The thallus formed by the marine pyrenomycete fungus Verrucaria tavaresiae and the phaeophycean alga Petroderma maculiforme was studied to elucidate the organization of the symbionts, determine the type of cellular contacts between them, and evaluate the status of the symbiosis as a lichen. Hand-sectioned and resin-embedded samples were examined with light and transmission electron microscopy. Within the uppermost portion of the cellular fungal tissue, separate algal filaments were arranged anticlinally. Protrusions of the fungal cell wall penetrated into adjacent algal walls but did not enter the cell lumen. A striking feature of these penetrations was the frequent separation of algal cell wall layers and insertion of fungal wall material between them. Algal filaments grew downward intrusively between fungal cells, often penetrating deeply into the fungal cell wall. Despite the exceptional nature of the phycobiont involved, the Verrucaria tavaresiae-Petroderma maculiforme symbiosis unequivocally fits the prevailing concept of a lichen. The distinctive interpenetrations observed between symbionts may be related to the integration of their different growth forms within a coherent tissue regularly subject to mechanical stresses. Periclinal cell divisions within and just below the algal layer may serve to replenish surface tissues lost to abrasion and herbivory.