Positive Branching Research Articles

Effects of Applied Voltage on Branching of Positive Leaders in Laboratory Long Sparks

AbstractPositive leaders branch less frequently than negative counterpart, and the physical processes and properties of positive leader branching remain a mystery. We investigated 10 m laboratory discharges under four positive voltages using a high‐speed video camera. Positive leaders differ from negative leaders by either directly splitting or connecting with floating bidirectional leaders to form branching, and the number of leader branches shows a positive correlation with the applied voltage, that is, the branched channels increased from 1 to 4 when the voltage increased by a factor of 1.5. Grounding points are positioned beneath the electrode and are more concentrated with lower voltage. During the stable progression of the leader, there is a slight increase in its development speed as the applied voltage rises. When the voltage is increased by 70%, the average breakdown time decreases by 40%. These characteristics provide insights into the branching mechanism of positive leaders.

The Combined Effects of Topography and Stiffness on Neuronal Differentiation and Maturation Using a Hydrogel Platform

Biophysical parameters such as substrate topography and stiffness have been shown independently to elicit profound effects on neuronal differentiation and maturation from neural progenitor cells (NPCs) yet have not been investigated in combination. Here, the effects of various micrograting and stiffness combinations on neuronal differentiation and maturation were investigated using a polyacrylamide and N-acryloyl-6-aminocaproic acid copolymer (PAA-ACA) hydrogel with tunable stiffness. Whole laminin was conjugated onto the PAA-ACA surface indirectly or directly to facilitate long-term mouse and human NPC-derived neuron attachment. Three micrograting dimensions (2-10 µm) were patterned onto gels with varying stiffness (6.1-110.5 kPa) to evaluate the effects of topography, stiffness, and their interaction. The results demonstrate that the extracellular matrix (ECM)-modified PAA-ACA gels support mouse and human neuronal cell attachment throughout the differentiation and maturation stages (14 and 28 days, respectively). The interaction between topography and stiffness is shown to significantly increase the proportion of β-tubulin III (TUJ1) positive neurons and microtubule associated protein-2 (MAP2) positive neurite branching and length. Thus, the effects of topography and stiffness cannot be imparted. These results provide a novel platform for neural mechanobiology studies and emphasize the utility of optimizing numerous biophysical cues for improved neuronal yield in vitro.

K-theoretic Catalan functions

We prove that the K-k-Schur functions are part of a family of inhomogenous symmetric functions whose top homogeneous components are Catalan functions, the Euler characteristics of certain vector bundles on the flag variety. Lam-Schilling-Shimozono identified the K-k-Schur functions as Schubert representatives for K-homology of the affine Grassmannian for SLk+1. Our perspective reveals that the K-k-Schur functions satisfy a shift invariance property, and we deduce positivity of their branching coefficients from a positivity result of Baldwin and Kumar. We further show that a slight adjustment of our formulation for K-k-Schur functions produces a second shift-invariant basis which conjecturally has both positive branching and a rectangle factorization property. Building on work of Ikeda-Iwao-Maeno, we conjecture that this second basis gives the images of the Lenart-Maeno quantum Grothendieck polynomials under a K-theoretic analog of the Peterson isomorphism.

Branche d’excitation collective du continuum dans les gaz de fermions condensés par paires : étude analytique et lois d’échelle

The pair-condensed unpolarized spin-1/2 Fermi gases have a collective excitation branch in their pair-breaking continuum (V.A. Andrianov, V.N. Popov, 1976). We study it at zero temperature, with the eigenenergy equation deduced from the linearized time-dependent BCS theory and extended analytically to the lower half complex plane through its branch cut, calculating both the dispersion relation and the spectral weights (quasiparticle residues) of the branch. In the case of BCS superconductors, so called because the effect of the ion lattice is replaced by a short-range electron-electron interaction, we also include the Coulomb interaction and we restrict ourselves to the weak coupling limit Δ/μ→0 + (Δ is the order parameter, μ the chemical potential) and to wavenumbers q=O(1/ξ) where ξ is the size of a pair; when the complex energy z q is expressed in units of Δ and q in units of 1/ξ, the branch follows a universal law insensitive to the Coulomb interaction. In the case of cold atoms in the BEC-BCS crossover, only a contact interaction remains, but the coupling strength Δ/μ can take arbitrary values, and we study the branch at any wave number. At weak coupling, we predict three scales, that already mentioned q≈1/ξ, that q≈(Δ/μ) -1/3 /ξ where the real part of the dispersion relation has a minimum and that q≈(μ/Δ)/ξ≈k F (k F is the Fermi wave number) where the branch reaches the edge of its existence domain. Near the point where the chemical potential vanishes on the BCS side, μ/Δ→0 + , where ξ≈k F , we find two scales q≈(μ/Δ) 1/2 /ξ and q≈1/ξ. In all cases, the branch has a limit 2Δ and a quadratic start at q=0. These results were obtained for μ>0, where the eigenenergy equation admits at least two branching points ϵ a (q) and ϵ b (q) on the positive real axis, and for an analytic continuation through the interval [ϵ a (q),ϵ b (q)]. We find new continuum branches by performing the analytic continuation through [ϵ b (q),+∞[ or even, for q low enough, where there is a third real positive branching point ϵ c (q), through [ϵ b (q),ϵ c (q)] and [ϵ c (q),+∞[. On the BEC side μ<0 not previously studied, where there is only one real positive branching point ϵ a (q), we also find new collective excitation branches under the branch cut [ϵ a (q),+∞[. For μ>0, some of these new branches have a low-wavenumber exotic hypoacoustic z q ≈q 3/2 or hyperacoustic z q ≈q 4/5 behavior. For μ<0, we find a hyperacoustic branch and a nonhypoacoustic branch, with a limit 2Δ and a purely real quadratic start at q=0 for Δ/|μ|<0.222.

Applicability Analysis of Directional Components in AC/DC Hybrid System

AC/DC hybrid power grids are more and more widely used in China, and the traditional relay protection directional components have experienced multiple misoperations. The adaptability of traditional directional components in AC / DC hybrid power grids is studied. Traditional direction components are based on fault sequence component network analysis. During the fault, the positive and negative sequence impedance of the AC-DC hybrid power grid is quite different, and the impedance angle of the line impedance and the equivalent impedance of the grid is no longer close to 90°. Misjudgment will occur in the direction component with sudden change, and performance cannot be guaranteed. As a result, directional elements based on the positive and negative sequence current branching coefficients being approximately equal are not suitable for AC/DC hybrid power grids. As for the directional element of the zero sequence principle, since the zero sequence network on the inverter side is relatively stable, its performance is reliable and it can operate correctly.

Sonine Formulas and Intertwining Operators in Dunkl Theory

Abstract Let $V_k$ denote Dunkl’s intertwining operator associated with some root system $R$ and multiplicity $k$. For two multiplicities $k, k^{\prime }$ on $R$, we study the intertwiner $V_{k^{\prime },k} = V_{k^{\prime }}\circ V_k^{-1}$ between Dunkl operators with multiplicities $k$ and $k^{\prime }.$ It has been a long-standing conjecture that $V_{k^{\prime },k}$ is positive if $k^{\prime } \geq k \geq 0.$ We disprove this conjecture by constructing counterexamples for root system $B_n$. This matter is closely related to the existence of Sonine-type integral representations between Dunkl kernels and Bessel functions with different multiplicities. In our examples, such Sonine formulas do not exist. As a consequence, we obtain necessary conditions on Sonine formulas for Heckman–Opdam hypergeometric functions of type $BC_n$ and conditions for positive branching coefficients between multivariable Jacobi polynomials.

First report of Dermatophilus congolensis infection in native Omani cattle.

Skin lesions were reported in a group of quarantined Omani native cattle for exportation purpose during January 2018. The skin lesions were reported in 17 animals out of 140 and were scattered over the head, neck, back and perineal region of the animals. Lesions varied from paint-brush matted hairs to wart-like lesions that are up to 2 cm in diameter. Skin scraping samples were obtained from the living animals and were directly stained with gram stain. Histologically, there was severe multifocal exudative dermatitis with hyperkeratosis. Dermis was infiltrated with neutrophils, mononuclear cells, and numerous branching filaments coccoid bodies. Bacterial culture on sheep blood agar revealed gray to white, beta hemolytic, raised and irregularly shaped colonies. Gram staining showed gram positive branching filaments with both transverse and longitudinal fragments formed from packs of coccoid cells confined with Dermatophilus congolensis. Animals were treated successfully with 3 doses of intra muscular injection of long-acting oxytetracycline with topical application of antibiotic spray. To the best of our knowledge, this is the first report of dermatophilosis in Omani cattle.

Development of Side Bidirectional Leader and Its Effect on Channel Branching of the Progressing Positive Leader of Lightning

AbstractFine time‐resolved images of the development of lightning bidirectional leaders below the cloud base were captured by a high‐speed camera in association with multiband electromagnetic field measurements. The bileaders tended to originate at a radial distance of about 200 m from a progressing positive leader channel, propagating more or less radially toward and away from the main channel. Significant asymmetrical channel extensions at opposite ends were clearly recognized. The positive ends of the bileaders propagated in single paths with average speed of 6.1 × 104 m/s, while the opposite negative end involved obvious branching and stepping propagation with average speed of 1.6 × 105 m/s. The bidirectional leaders eventually connected to the existing main positive leader, producing new branches of the flash. Another cause of positive leader branching was that the positive leader split at its head and developed into different branches synchronously, which were sometimes invisible but were revealed by recoil leaders.

Influence of photoionization rates on positive streamer branching in atmospheric air

Streamer is a strong ionizing region which advances very quickly in gases, liquids and solids. Streamer is a low-temperature plasma, which produces a variety of chemically reactive substances efficiently. So, streamer discharge has been widely adopted in industry. Furthermore, streamer is the initial stage of electric breakdown in long air gap. Studying the streamer discharge characteristics and its mechanism is the basis of external insulation in power transmission systems.Streamer branching is a significant characteristic during its development. Lichtenberg figure is the first clear recording of the filamentary structure of streamers. One of acceptable explanations is that the random fluctuations of the electron density ahead of streamer trigger branching. Furthermore, photoionization provides the necessary free electrons for the development of positive streamers. The experimental results show that the branching characteristics are closely related to the photoionization rate in streamer head. The streamer shows higher possibility of branching if the photoionization rate decreases. Since previous experiment is indirect evidence of this deduction, we turn to numerical models to study the influence of photoionization rates on positive streamer branching in atmospheric air. A three-dimensional particle-in-cell model with Monte Carlo collision (PIC-MCC) scheme called Pamdi3D (Teunissen J, Ebert U 2016 &lt;i&gt;Plasma Sources Sci. Technol.&lt;/i&gt; &lt;b&gt;25&lt;/b&gt; 044005) is employed in this paper. The development and branching of positive streamersin a millimeter-scale needle-plane gap are simulated at atmospheric pressure. Different streamer branching behaviors are investigated by artificially changing the nitrogen-oxygen ratio, the absorption cross section of oxygen, and the photoionization efficiency coefficient.The effects of different photoionization parameters are systematically studied. When the nitrogen-oxygen ratio, photon absorption cross section or photoionization efficiency coefficient are reduced, the streamer branching occurs earlier in three cases after reducing the photoionization rate. These results imply that the streamer shows higher possibility of branching if the photoionization rate decreases. When the streamer propagates in a non-uniform electric field region and the photoionization rate decreases to a certain value, it is believed that the seed electron distribution is more susceptible to random fluctuations. It will lead to instability in the space charge layer of streamer, thus causing the streamer to branch. Hence it is proposed that streamer branch will be triggered more easily if the photoionization rate in the streamer head decreases, in the case without considering other seed electron sources.

Effect of Voltage Rise Rate on Streamer Branching and Shock Wave Characteristics in Supercritical Carbon Dioxide

This paper reports on the dependence of voltage rise rate on positive streamer branching and shock waves in supercritical carbon dioxide. Voltages with rise rates of 0.21 and 4.5 kV/ns were applied to a needle-to-plane electrode. Prebreakdown phenomena involving streamer growth and shock wave propagation were observed by means of a shadowgraph method. The results show that the spread angle of the streamer at the needle tip under 4.5 kV/ns was nearly twice as large as that under 0.21 kV/ns. The discharge may initiate without density reduction due to electrostrictive force. While shock wave Mach number was little affected by the voltage rise rate, it increased by increasing the negative voltage peak. Consequently, the velocity of shock wave is presumed to be influenced by the population of the vibrational state of carbon dioxide.

Involvement of phosphoinositide 3-kinase class IA (PI3K 110α) and NADPH oxidase 1 (NOX1) in regulation of vascular differentiation induced by vascular endothelial growth factor (VEGF) in mouse embryonic stem cells.

The impact of reactive oxygen species and phosphoinositide 3-kinase (PI3K) in differentiating embryonic stem (ES) cells is largely unknown. Here, we show that the silencing of the PI3K catalytic subunit p110α and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 1 (NOX1) by short hairpin RNA or pharmacological inhibition of NOX and ras-related C3 botulinum toxin substrate 1 (Rac1) abolishes superoxide production by vascular endothelial growth factor (VEGF) in mouse ES cells and in ES-cell-derived fetal liver kinase-1(+) (Flk-1(+)) vascular progenitor cells, whereas the mitochondrial complex I inhibitor rotenone does not have an effect. Silencing p110α or inhibiting Rac1 arrests vasculogenesis at initial stages in embryoid bodies, even under VEGF treatment, as indicated by platelet endothelial cell adhesion molecule-1 (PECAM-1)-positive areas and branching points. In the absence of p110α, tube-like structure formation on matrigel and cell migration of Flk-1(+) cells in scratch migration assays are totally impaired. Silencing NOX1 causes a reduction in PECAM-1-positive areas, branching points, cell migration and tube length upon VEGF treatment, despite the expression of vascular differentiation markers. Interestingly, silencing p110α but not NOX1 inhibits the activation of Rac1, Ras homologue gene family member A (RhoA) and Akt leading to the abrogation of VEGF-induced lamellipodia structure formation. Thus, our data demonstrate that the PI3K p110α-Akt/Rac1 and NOX1 signalling pathways play a pivotal role in VEGF-induced vascular differentiation and cell migration. Rac1, RhoA and Akt phosphorylation occur downstream of PI3K and upstream of NOX1 underscoring a role of PI3K p110α in the regulation of cell polarity and migration.

Diagnosis of dermatophilosis in dairy cattle in Kerala, India

Skin scabs and scrapings from 82 dermatitis cases in dairy cattle were subjected to detailed bacteriological, mycological, parasitological and molecular studies. Microscopical examination of Giemsa or Gram’s stained smears of scab material from the lesions revealed characteristic gram positive septate branching filaments with typical tram track appearance suggestive of Dermatophilus congolensis in 72 samples (91.5%). Culture of scab materials in sheep blood agar under anaerobic condition yielded typical beta haemolytic colonies of D. congolensis in 75 samples, which were further confirmed by colony morphology, staining characters and biochemical reactions. Molecular confirmation of the isolates was carried out using polymerase chain reaction with primers based on 16S rRNA which yielded specific band of 500bp. The pathogenicity of the isolates was also proved by experimental inoculation into rabbits.

Investigation of grain competitive growth during directional solidification of single-crystal nickel-based superalloys

Grain competitive growth of nickel-based single-crystal superalloys during directional solidification was investigated. A detailed characterization of bi-crystals’ competitive growth was performed to explore the competitive grain evolution. It was found that high withdrawal rate improved the efficiency of grain competitive growth. The overgrowth rate was increased when the misorientation increased. Four patterns of grain competitive growth with differently oriented dispositions were characterized. The results indicated that the positive branching of the dendrites played a significant role in the competitive growth process. The effect of crystal orientation and heat flow on the competitive growth can be attributed to the blocking mechanism between the adjacent grains.

English

Primary cutaneous nocardiosis can present as an abscess or cellulitis with sporotrichoid morphology. Deep inoculation in the subcutaneous tissue can present as a mycetoma. Mycetoma over the elbow region is rare. We herein describe a case of primary cutaneous nocardiosis presenting as a mycetoma, caused by Nocardia asteroides. The patient had extensive keloidal lesions with few sinuses extruding serous discharge over the right forearm around elbow joint. Initially pus and later, the deep tissue biopsy samples were sent for culture and sensitivity, without suspecting nocardial infection. Gram stain of the pus showed few WBCs and occasional Gram positive branching filaments. Modified Kinyoun stain of the same revealed acid-fast filamentous structures. Culture of the tissue specimen yielded Nocardia asteroides. The patient responded well to a modified Ramam's regime. On follow-up, the patient showed no recurrence at 1 year. Our case demonstrates the need for focused clinical search with a high degree of suspicion, and appropriate laboratory procedures in the diagnosis and management of cutaneous nocardiosis.

English

A 60-year-old female patient presented with history of swelling over the right foot with multiple sinuses having seropurulent discharge. On gram stain -gram positive branching filamentous bacilli, (actinomycotic mycetoma) were demonstrated and was started on Welsh regimen, patient responded well with one cycle. This case is reported to emphasize the importance of laboratory diagnosis in the management and assessment of the prognosis of such cases.

Disseminated &lt;i&gt;Nocardia&lt;/i&gt; infection presenting as hemorrhagic pustules and ecthyma in a woman with systemic lupus erythematosus and antiphospholipid antibody syndrome

Nocardia is an opportunistic pathogen that can cause disseminated infection in immunocompromised hosts. The most common type of skin lesion reported with disseminated Nocardia is a subcutaneous nodule; however, there are reports with unusual cutaneous presentations. Long term corticosteroid treatment is one of the largest risk factors for developing disseminated Nocardia. Initial treatment is empiric as each strain has unique susceptibilities and it takes weeks to speciate and test sensitivities. A 66-year-old female on long term corticosteroids for systemic lupus erythematosus (SLE) and antiphospholipid syndrome presented with a polymorphous skin eruption and systemic symptoms concerning for infection. Especially concerning were areas of hemorrhagic pustules on the lower legs, and two ecthymatous lesions on the thigh. Tissue culture Gram stain revealed Gram positive branching filamentous rods concerning for Nocardia. The patient improved with empiric treatment. This case of Nocardiosis had unusual cutaneous findings that could have misguided the clinician, but the tissue culture and Gram stain proved to be useful for rapid diagnosis and proper treatment.

Structure of Population Inside Propagating Front

We study the long-time and long-range behavior of branching diffusion processes (starting with a single particle) in two different situations: when the branching potential has compact support and when the branching potential is constant. For compactly supported branching potentials we analyze the super-critical case where the total number of particles grows exponentially with positive probability. We study the asymptotics of the number of particles in different regions of space and describe the growth of the region occupied by the particles. For positive constant branching potentials we observe the intermittency effect: for the number of particles located at time t in a unit neighborhood of tv the kth moment grows exponentially faster than the kth power of the first moment as t→∞ provided that v ≠ 0 and k = k(v) is sufficiently large. Bibliography: 16 titles.

Unusual abdominal masses.

A 66-year-old afebrile man presented with a 10-day history of general fatigue. He had a history of autoimmune pancreatitis and tubulointerstitial nephritis diagnosed from a kidney biopsy of the left kidney. He had been treated with oral glucocorticoids (prednisolone 25 mg/day) for 3 months. He had normal hepatic function, renal insufficiency (creatinine 122 lmol/L) and a leucocyte concentration of 31.4 3 10/L with predominant neutrophils. There were no abdominal symptoms. An emergency computed tomography (CT) scan was performed to determine the cause of the inflammation. The CT scan revealed a large solid mass in the pelvis and a solid mass in the right retroperitoneal space (Figure 1A and B, indicated by arrows). Gram staining of the grey fluid aspirated from the right retroperitoneal mass (Figure 1C) revealed positive branching rods suggestive ofActinomyces (Figure 1D). We cultured the organism and identified Actinomyces. Intravenous cefotaxime was started, as our patient’s bacterium was ampicillin resistant, and treatment was continued for

An investigation of a recent outbreak of nocardioform placentitis caused abortions in horses

Nocardioform placentitis associated with gram positive branching actinomycetes caused a record number of abortions in mares diagnosed by the University of Kentucky Veterinary Diagnostic Laboratory (UKVDL) affecting the 2011 foal crop (2011 foal crop: the cohort of foals conceived during the 2010 breeding season). The goal of the present study is to make a comprehensive analysis of this outbreak in terms of frequencies of the bacteria causing nocardioform placentitis mediated abortions and to investigate the ages of fetuses, abortion months and breeding times. In the present study, characteristic slow-growing, pungent/soil odor gram positive branching actinomycetes were recovered in high numbers in placental specimens in 76 abortion cases diagnosed as nocardioform placentitis by pathologists. To determine the type of actinomycetes responsible for the abortions, PCR assays were performed on the gram positive branching bacilli. The most prominent actinomycetes species were Amycolatopsis spp. (37 cases, 48.7%) and Crossiella equi (C. equi) (22 cases, 28.9%). Six cases (7.9%) contained both Amycolatopsis spp., and C. equi. 10 isolates were unidentified by PCR assays and shown to have high DNA sequence homology to Streptomyces species, Microbacterium species, Nocardia species and Allokutzneria species, as evidenced by 16 rRNA gene sequencing and phylogenetic analysis. Nocardioform placentitis related abortions occurred mostly between December 2010 and April 2011 happening exclusively in the last trimester. Breeding time of aborted pregnancies ranged from March 2010 to July 2010, suggesting that if transmission of the actinomycetes agents occurred during breeding, it was not related to a specific season.

Controlling branching in streamer discharge by laser background ionization

Irradiation with a KrF laser controlled the positive streamer branching in atmospheric argon gas. This laser irradiation changed the amount of background ionization before the streamer discharge. Measuring the ionization current allowed us to evaluate the initial electron density formed by the KrF laser. We observed characteristic feather-like branching structure and found that it was only suppressed in the irradiated region. The threshold of ionization density which can influence the branching was evaluated to be 5 × 105 cm−3. The relationship between the size of avalanche head and mean distance between initial electrons explained this suppression behaviour. These experimental results support that the feather-like structure originates from the branching model of Loeb–Meek, a probabilistic merging of individual avalanches.