Computation of confined swirling flow using RNG and k-epsilon turbulence models

In this work we numerically model isothermal turbulent swirling flow in a cylindrical burner. Three versions of the RNG k-epsilon model are assessed against performance of the standard k-epsilon model. Sensitivity of numerical predictions to grid refinement, differing convective differencing schemes and choice of (unknown) inlet dissipation rate, were closely scrutinised to ensure accuracy. Particular attention is paid to modelling the inlet conditions to within the range of uncertainty of the experimental data, as model predictions proved to be significantly sensitive to relatively small changes in upstream flow conditions. We also examine the characteristics of the swirl--induced recirculation zone predicted by the models over an extended range of inlet conditions. Our main findings are: - (i) the standard k-epsilon model performed best compared with experiment; - (ii) no one inlet specification can simultaneously optimize the performance of the models considered; - (iii) the RNG models predict both single-cell and double-cell IRZ characteristics, the latter both with and without additional internal stagnation points. The first finding indicates that the examined RNG modifications to the standard k-e model do not result in an improved eddy viscosity based model for the prediction of swirl flows. The second finding suggests that tuning established models for optimal performance in swirl flows a priori is not straightforward. The third finding indicates that the RNG based models exhibit a greater variety of structural behaviour, despite being of the same level of complexity as the standard k-e model. The plausibility of the predicted IRZ features are discussed in terms of known vortex breakdown phenomena.

Identification of protein interaction regions of VINC/NEAT1/Men epsilon RNA

The virus inducible non-coding RNA (VINC) was detected initially in the brain of mice infected with Japanese encephalitis virus (JEV) and rabies virus. VINC is also known as NEAT1 or Men epsilon RNA. It is localized in the nuclear paraspeckles of several murine as well as human cell lines and is essential for paraspeckle formation. We demonstrate that VINC interacts with the paraspeckle protein, P54nrb through three different protein interaction regions (PIRs) one of which (PIR-1) is localized near the 50 end while the other two (PIR-2, PIR-3) are localized near the 30 region of VINC. Our studies suggest that VINC may interact with P54nrb through a novel mechanism which is different from that reported for protein coding RNAs. (C) 2010 Federation of European Biochemical Societies. Published by Elsevier B. V. All rights reserved.

Modular design of synthetic protein mimics. Crystal structure of two seven-residue helical peptide segments linked by .epsilon.-aminocaproic acid

Two seven-residue helical segments, Val-Ala-Leu-Aib-Val-Ala-Leu, were linked synthetically with an epsilon-aminocaproic acid (Acp) linker with the intention of making a stable antiparallel helix-helix motif. The crystal structure of the linked peptide Boc-Val-Ala-Leu-Aib-Val-Ala-Leu-Acp-Val-Ala-Leu-Aib-Val-Ala-Leu-OMe (1) shows the two helices displaced laterally from each other by the linker, but the linker has not folded the molecule into a close-packed antiparallel conformation. Two strong intermolecular NH...O = C hydrogen bonds are formed between the top of the lower helix of one molecule and the bottom of the upper helix in a laterally adjacent molecule to give the appearance of an extended single helix. The composite peptide with Boc and OMe end groups, C76H137N15O18.H2O, crystallize in space group P2(1) with a = 8.802 (1) angstrom, b = 20.409 (4) angstrom, c = 26.315 (3) angstrom, and beta = 90.72 (1)degrees; overall agreement R = 7.86% for 5030 observed reflections (\F(o)\ > 3-sigma(F)); resolution = 0.93 angstrom. Limited evidence for a more compact conformation in solution consistent with an antiparallel helix arrangement is obtained by comparison of the HPLC retention times and CD spectra of peptide 1 with well-characterized continuous helices of similar length and sequence.

Isolation and characterization of DNA polymerase epsilon from the silk glands of Bombyx mori

The silk gland of Bombyx mori, an endomitotically replicative tissue shows high levels of DNA polymerases alpha, delta, and epsilon activities. The ratio of polymerase alpha to that of delta plus epsilon is maintained at 1.1 to 1.3 in both the posterior and middle silk glands for the entire duration of late larval development. The three activities copurify in the initial stages of fractionation through phosphocellulose and DE52 but polymerase alpha gets resolved from the others on hydroxylapatite column. Separation between polymerase delta and epsilon is achieved by chromatography on QAE-Sephadex. DNA polymerase epsilon is a heterodimer comprising of 215- and 42-kDa subunits. The activity is maximum at pH 6.5 and the Km values for dNTPs vary between 3-9 microM. The enzyme possesses an intrinsically associated exonuclease activity which functions in the mismatch repair during DNA synthesis. Both polymerase and 3'-->5' exonuclease activities are associated with the 215-kDa subunit. By itself, DNA polymerase epsilon is processive and the catalytic activity is not enhanced by externally added bPCNA (Bombyx-proliferating cell nuclear antigen, an auxiliary protein for DNA polymerase delta). The enzyme resembles polymerase delta in having the exonuclease activity and in its response to aphidicolin or substrate analogs, but could be distinguished from the latter by its lack of response to the bPCNA and sensitivity to dimethyl sulfoxide. The two enzymes show partial immunological cross-reactivity with each other but no immunological relatedness to polymerase alpha. The absence of the repair enzyme DNA polymerase beta and the presence of substantial levels of polymerase epsilon in the silk glands suggest a possible role for the latter in DNA repair in that tissue.

The mean and turbulence structure simulation of the monsoon trough boundary layer using a one-dimensional model with e-l and e-epsilon closures

An attempt has been made here to study the sensitivity of the mean and the turbulence structure of the monsoon trough boundary layer to the choice of the constants in the dissipation equation for two stations Delhi and Calcutta, using one-dimensional atmospheric boundary layer model with e-epsilon turbulence closure. An analytical discussion of the problems associated with the constants of the dissipation equation is presented. It is shown here that the choice of the constants in the dissipation equation is quite crucial and the turbulence structure is very sensitive to these constants. The modification of the dissipation equation adopted by earlier studies, that is, approximating the Tke generation (due to shear and buoyancy production) in the epsilon-equation by max (shear production, shear + buoyancy production), can be avoided by a suitable choice of the constants suggested here. The observed turbulence structure is better simulated with these constants. The turbulence structure simulation with the constants recommended by Aupoix et al (1989) (which are interactive in time) for the monsoon region is shown to be qualitatively similar to the simulation obtained with the constants suggested here, thus implying that no universal constants exist to regulate dissipation rate. Simulations of the mean structure show little sensitivity to the type of the closure parameterization between e-l and e-epsilon closures. However the turbulence structure simulation with e-epsilon closure is far better compared to the e-l model simulations. The model simulations of temperature profiles compare quite well with the observations whenever the boundary layer is well mixed (neutral) or unstable. However the models are not able to simulate the nocturnal boundary layer (stable) temperature profiles. Moisture profiles are simulated reasonably better. With one-dimensional models, capturing observed wind variations is not up to the mark.

A k-epsilon model for turbulent weld pool convection in gas metal arc welding process

In this paper, we present a modified k - epsilon model capable of addressing turbulent weld-pool convection in a GMAW process, taking into account the morphology of the phase change interface during a Gas Metal Arc Welding (GMAW) process. A three-dimensional turbulence mathematical model has been developed to study the heat transfer and fluid flow within the weld pool by considering the combined effect of three driving forces, viz., buoyancy, Lorentz force and surface tension (Marangoni convection). Mass and energy transports by the droplets are considered through the thermal analysis of the electrode. The falling droplet's heat addition to the molten pool is considered to be a volumetric heat source distributed in an imaginary cylindrical cavity ("cavity model") within the weld pool. This nature of heat source distribution takes into account the momentum and the thermal, energy of the falling droplets. The numerically predicted weld pool dimensions both from turbulence and laminar models are then compared with the experimental post-weld results sectioned across the weld axis. The above comparison enables us to analyze the overall effects of turbulent convection on the nature of heat and fluid flow and hence on the weld pool shape/size during the arc welding processes.

Amine-functionalized multiwall carbon nanotubes impart osteoinductive and bactericidal properties in poly(epsilon-caprolactone) composites

Poly(epsilon-caprolactone) (PCL) is an aliphatic polyester widely used for biomedical applications but lacks the mechanical properties desired for many load-bearing orthopedic applications. The objective of this study was to prepare and characterize PCL composites incorporating multiwall carbon nanotubes (MWNTs) with different surface functional groups. PCL composites were prepared by melt-mixing with three different types of MWNTs: pristine (pMWNT), amine functionalized (aMWNT), and carboxyl functionalized (cMWNT). Melt rheology and scanning electron microscopy indicated good dispersion of the nanotubes in the matrix. Tensile strength and elastic modulus of the polymer was significantly increased by the incorporation of MWNTs and further enhanced by favorable interactions between PCL and aMWNTs. Thermal analysis revealed that MWNTs act as heterogeneous nucleation sites for crystallization of PCL and increase polymer crystallinity. Incorporation of functionalized MWNTs increased the surface water wettability of PCL. Osteoblast proliferation and differentiation was significantly enhanced on functionalized composites. aMWNT composites also exhibited the best bactericidal response. This study demonstrates that surface functionalization of MWNTs profoundly influences the properties of PCL and amine-functionalization offers the optimal combination of mechanical properties, osteogenesis and antimicrobial response. These results have important implications for designing nanocomposites for use in orthopedics.

Small strong epsilon nets

Let P be a set of n points in R-d. A point x is said to be a centerpoint of P if x is contained in every convex object that contains more than dn/d+1 points of P. We call a point x a strong centerpoint for a family of objects C if x is an element of P is contained in every object C is an element of C that contains more than a constant fraction of points of P. A strong centerpoint does not exist even for halfspaces in R-2. We prove that a strong centerpoint exists for axis-parallel boxes in Rd and give exact bounds. We then extend this to small strong epsilon-nets in the plane. Let epsilon(S)(i) represent the smallest real number in 0, 1] such that there exists an epsilon(S)(i)-net of size i with respect to S. We prove upper and lower bounds for epsilon(S)(i) where S is the family of axis-parallel rectangles, halfspaces and disks. (C) 2014 Elsevier B.V. All rights reserved.

epsilon-expansions near three dimensions from conformal field theory

We formally extend the CFT techniques introduced in arXiv: 1505.00963, to phi(2d0/d0-2) theory in d = d(0) dimensions and use it to compute anomalous dimensions near d(0) = 3, 4 in a unified manner. We also do a similar analysis of the O(N) model in three dimensions by developing a recursive combinatorial approach for OPE contractions. Our results match precisely with low loop perturbative computations. Finally, using 3-point correlators in the CFT, we comment on why the phi(3) theory in d(0) = 6 is qualitatively different.

Gamma -> Epsilon Martensite Transformation and Twinning Deformation in fcc Cobalt During Surface Mechanical Attrition Treatment

The deformation microstructure of face-centered cubic cobalt subjected to surface mechanical attrition treatment was studied as a function of strain levels. Strain-induced gamma --> epsilon transformation and twinning deformation were evidenced by transmission electron microscopy and were found to progress continuously in ultrafine and nanocrystalline grains as the strain increased.

Completions of epsilon-dense partial Latin squares

A classical question in combinatorics is the following: given a partial Latin square $P$, when can we complete $P$ to a Latin square $L$? In this paper, we investigate the class of textbf{$epsilon$-dense partial Latin squares}: partial Latin squares in which each symbol, row, and column contains no more than $epsilon n$-many nonblank cells. Based on a conjecture of Nash-Williams, Daykin and H"aggkvist conjectured that all $frac{1}{4}$-dense partial Latin squares are completable. In this paper, we will discuss the proof methods and results used in previous attempts to resolve this conjecture, introduce a novel technique derived from a paper by Jacobson and Matthews on generating random Latin squares, and use this novel technique to study $ epsilon$-dense partial Latin squares that contain no more than $delta n^2$ filled cells in total.

In Chapter 2, we construct completions for all $ epsilon$-dense partial Latin squares containing no more than $delta n^2$ filled cells in total, given that $epsilon < frac{1}{12}, delta < frac{ left(1-12epsilonright)^{2}}{10409}$. In particular, we show that all $9.8 cdot 10^{-5}$-dense partial Latin squares are completable. In Chapter 4, we augment these results by roughly a factor of two using some probabilistic techniques. These results improve prior work by Gustavsson, which required $epsilon = delta leq 10^{-7}$, as well as Chetwynd and H"aggkvist, which required $epsilon = delta = 10^{-5}$, $n$ even and greater than $10^7$.

If we omit the probabilistic techniques noted above, we further show that such completions can always be found in polynomial time. This contrasts a result of Colbourn, which states that completing arbitrary partial Latin squares is an NP-complete task. In Chapter 3, we strengthen Colbourn's result to the claim that completing an arbitrary $left(frac{1}{2} + epsilonright)$-dense partial Latin square is NP-complete, for any $epsilon > 0$.

Colbourn's result hinges heavily on a connection between triangulations of tripartite graphs and Latin squares. Motivated by this, we use our results on Latin squares to prove that any tripartite graph $G = (V_1, V_2, V_3)$ such that begin{itemize} item $|V_1| = |V_2| = |V_3| = n$, item For every vertex $v in V_i$, $deg_+(v) = deg_-(v) geq (1- epsilon)n,$ and item $|E(G)| > (1 - delta)cdot 3n^2$ end{itemize} admits a triangulation, if $epsilon < frac{1}{132}$, $delta < frac{(1 -132epsilon)^2 }{83272}$. In particular, this holds when $epsilon = delta=1.197 cdot 10^{-5}$.

This strengthens results of Gustavsson, which requires $epsilon = delta = 10^{-7}$.

In an unrelated vein, Chapter 6 explores the class of textbf{quasirandom graphs}, a notion first introduced by Chung, Graham and Wilson cite{chung1989quasi} in 1989. Roughly speaking, a sequence of graphs is called "quasirandom"' if it has a number of properties possessed by the random graph, all of which turn out to be equivalent. In this chapter, we study possible extensions of these results to random $k$-edge colorings, and create an analogue of Chung, Graham and Wilson's result for such colorings.

Synthesis and micellization of star-like hyperbranched polymer with poly(ethylene oxide) and Poly(epsilon-caprolactone) arms

Novel star-like hyperbranched polymers with amphiphilic arms were synthesized via three steps. Hyperbranched poly(amido amine)s containing secondary amine and hydroxyl groups were successfully synthesized via Michael addition polymerization of triacrylamide (TT) and 3-amino-1,2-propanediol (APD) with feed molar ratio of 1:2. H-1, C-13, and HSQC NMR techniques were used to clarify polymerization mechanism and the structures of the resultant hyperbranched polymers

Study on the Cell Structure and Compressive Behavior of Biodegradable Poly(epsilon-caprolactone) Foam

Biodegradable poly(e-caprolactone) (PCL) foams with a series of controlled structures were prepared by using chemical foaming method. The cell morphology was detected by scanning electron microscope (SEM). The compressive behavior of the foams was investigated by uniaxial compression test. The effect of density and structural parameters on the foam compressive behavior was analyzed. It was found that the relative compressive modulus has a power law relationship with relative density. Increasing of both the cell wall thickness and the cell density lead to higher compressive modulus of the foam; however, the cell size has no distinct effect on compressive behavior.

Rhythmic Growth-Induced Ring-Banded Spherulites with Radial Periodic Variation of Thicknesses Grown from Poly(epsilon-caprolactone) Solution with Constant Concentration

Birefringent ring-banded spherulites with radial periodic variation of thicknesses were grown from poly(epsilon-caprolactone) (PCL) solutions under conditions for which the Solution concentration was held constant during the whole development of the morphology. The as-grown ring-banded spherulites were investigated by optical (OM) and atomic force (AFM) microscopies, by transmission electron microscopy (TEM) of samples sectioned parallel to the plane of film, and also by electron diffraction (ED) and grazing incidence X-ray diffraction (GIXD) techniques.

Rare-Earth Metal Bis(alkyl)s Supported by a Quinolinyl Anilido-Imine Ligand: Synthesis and Catalysis on Living Polymerization of epsilon-Caprolactone

The tridentate ligand N-(2-((2,6-diisopropylphenylimino)methyl)phenyl)quinolin-8-amine (HL) was prepared. Treatment of HL with 1 equiv of Ln(CH2SiMe3)(3)(THF)(2) afforded the corresponding rare-earth metal bis(alkyl) complexes LLn(CH2SiMe3)(2)(THF)(n) (Ln = Sc, n = 0 (1); Y, n = 1 (2); Lu, n = 0 (3)) in high yields. Variable-temperature H-1 NMR spectral analysis showed that these complexes were fluxional at room temperature. Complexes 1 and 3 were THF-free, where the metal center adopted a square-pyramidal geometry, while in 2 the metal center generated a distorted octahedral geometry owing to the coordination of a THF molecule.