Stretching of polymers around the Kolmogorov scale in a turbulent shear flow

We present numerical studies of stretching of Hookean dumbbells in a turbulent Navier-Stokes flow with a linear mean profile, =Sy. In addition to the turbulence features beyond the viscous Kolmogorov scale \eta, the dynamics at the equilibrium extension of the dumbbells significantly below eta is well resolved. The variation of the constant shear rate S causes a change of the turbulent velocity fluctuations on all scales and thus of the intensity of local stretching rate of the advecting flow. The latter is measured by the maximum Lyapunov exponent lambda_1 which is found to increase as \lambda_1 ~ S^{3/2}, in agreement with a dimensional argument. The ensemble of up to 2 times 10^6 passively advected dumbbells is advanced by Brownian dynamics simulations in combination with a pseudospectral integration for the turbulent shear flow. Anisotropy of stretching is quantified by the statistics of the azimuthal angle $\phi$ which measures the alignment with the mean flow axis in the x-y shear plane, and the polar angle theta which determines the orientation with respect to the shear plane. The asymmetry of the probability density function (PDF) of phi increases with growing shear rate S. Furthermore, the PDF becomes increasingly peaked around mean flow direction (phi= 0). In contrast, the PDF of the polar angle theta is symmetric and less sensitive to changes of S.Comment: 16 pages, 14 Postscript figures (2 with reduced quality

Consumo e produção de leite de vacas mestiças Lactantes em pastejo de Capim-Elefante (Pennisetum purpureum Schum.) sob duas doses de Nitrogênio.

Foram estimados a produção de leite, o consumo voluntário de matéria seca e a taxa de passagem da FDN no trato gastrintestinal em quatro épocas do ano (julho, outubro, janeiro e março), de vacas mestiças, sob pastejo de capim-elefante, submetido a doses de 300 e 700 kg de N/ha/ano. Utilizou-se o pastejo rotativo com três dias de ocupação e 30 de descanso, empregando-se 36 vacas lactantes mestiças H ´ Z, numa lotação de 6 vacas/ha, sendo a estimativa de consumo e a taxa de passagem determinadas em apenas 24 animais. Para a coleta de extrusas foram utilizadas duas vacas esôfago-fistuladas. O consumo foi estimado usando-se a relação produção fecal : indigestibilidade dos alimentos. A produção fecal foi estimada utilizando-se a FDN da extrusa marcada com dicromato de sódio fornecida em dose única. O consumo de MS total não foi afetado pelas doses de nitrogênio, nem por épocas, registrando-se valores médios diários de 10,9 e 10,5 kg de MS/vaca para as doses de 300 e 700 kg de N/ha/ano, respectivamente. Entretanto, o consumo de MS do capim-elefante foi afetado por doses de N e épocas, observando-se valores de 6,5 e 5,6 kg/vaca/dia para as doses acima. O capim-elefante teve uma participação média na matéria seca total ingerida, de 26,0% (julho/outubro) e 84,0% (janeiro/março). A produção diária de leite não foi afetada por doses de nitrogênio, observando-se produções médias de 11,6 e 12,3 kg de leite/vaca/dia, para as doses de 300 e 700 kg de N, respectivamente.bitstream/CPAF-RO-2010/13299/1/bpd58-capimelefante-.pdfParceria Embrapa Agrobiologia

Macrostructural aspects in oral narratives in Brazilian Portuguese by left and right hemisphere stroke patients with low education and low socioeconomic status

Objective: Individuals with a stroke in either the left (LH) or right hemisphere (RH) often present macrostructural impairments in narrative abilities. Understanding the potential influence of low education and low socioeconomic status (SES) is critical to a more effective assessment of post-stroke language. The first aim was to investigate macrostructural processing in low education and low SES individuals with stroke in the LH or RH or without brain damage. The second aim was to verify the relationships between macrolinguistic, neuropsychological, and sociodemographic variables. Methods: Forty-seven adults with LH (n = 15) or RH (n = 16) chronic ischemic stroke and 16 matched (age, education, and SES) healthy controls produced three oral picture-sequence narratives. The macrostructural aspects analyzed were cohesion, coherence, narrativity, macropropositions, and index of lexical informativeness and were compared among the three groups. Then, exploratory correlations were performed to assess associations between sociodemographic (such as SES), neuropsychological, and macrostructural variables. Results: Both LH and RH presented impairments in the local macrostructural aspect (cohesion), while RH also presented impairments in more global aspects (global coherence and macropropositions). All five macrostructural variables correlated with each other, with higher correlations with narrativity. Naming was correlated with all macrostructural variables, as well as pre-stroke reading and writing habits (RWH), showing that higher naming accuracy and higher RWH are associated with better macrostructural skills. Conclusion: The present results corroborate the role of the LH in more local processing and the RH in more global aspects of discourse. Moreover, the study highlights the importance of investigating discourse processing in healthy and clinical populations of understudied languages such as Brazilian Portuguese, with various levels of education, SES, and reading and writing habits

The spectral variability and magnetic field characteristics of the Of?p star HD 148937

We report magnetic and spectroscopic observations and modeling of the Of?p star HD 148937 within the context of the MiMeS LP at the CFHT. Thirty-two high signal-to-noise ratio circularly polarised (Stokes V) spectra and 13 unpolarised (Stokes I) spectra of HD 148937 were acquired in 2009 and 2010. A definite detection of a Stokes V Zeeman signature is obtained in the grand mean of all observations (in both LSD mean profiles and individual spectral lines). The longitudinal magnetic field inferred from the Stokes V LSD profiles is consistently negative, in contrast to the essentially zero field strength measured from the diagnostic null profiles. A period search of equivalent width measurements confirms the previously-reported 7.03 d variability period. The variation of equivalent widths is not strictly periodic: we present evidence for evolution of the amount or distribution of circumstellar plasma. Interpreting the 7.03 d period as the stellar rotational period within the context of the ORM, we have phased the equivalent widths and longitudinal field measurements. The longitudinal field measurements show a weak sinusoidal variation of constant sign, with extrema out of phase with the H{\alpha} variation by about 0.25 cycles. The inferred magnetic configuration confirms the suggestion of Naz\'e et al (2010), who proposed that the weaker variability of HD 148937 as compared to other members of this class is a consequence of the stellar geometry. Based on the derived magnetic properties and published wind characteristics, we find a wind magnetic confinement parameter \eta\ast \simeq 20 and rotation parameter W = 0.12, supporting a picture in which the Halpha emission and other line variability have their origin in an oblique, rigidly rotating magnetospheric structure resulting from a magnetically channeled wind. (Abridged.)Comment: 13 pages, MNRAS. Version 2, small change to Fig. 1

Rotation, spectral variability, magnetic geometry and magnetosphere of the Of?p star CPD -28 2561

We report magnetic and spectroscopic observations and modeling of the Of?p star CPD -28 2561. Using more than 75 new spectra, we have measured the equivalent width variations and examined the dynamic spectra of photospheric and wind-sensitive spectral lines. A period search results in an unambiguous 73.41 d variability period. High resolution spectropolarimetric data analyzed using Least-Squares Deconvolution yield a Zeeman signature detected in the mean Stokes V profile corresponding to phase 0.5 of the spectral ephemeris. Interpreting the 73.41 d period as the stellar rotational period, we have phased the equivalent widths and inferred longitudinal field measurements. The phased magnetic data exhibit a weak sinusoidal variation, with maximum of about 565 G at phase 0.5, and a minimum of about -335 G at phase 0.0, with extrema approximately in phase with the (double-wave) Halpha equivalent width variation. Modeling of the Halpha equivalent width variation assuming a quasi-3D magnetospheric model produces a unique solution for the ambiguous couplet of inclination and magnetic obliquity angles: (i, beta) or (beta, i)=(35 deg,90 deg). Adopting either geometry, the longitudinal field variation yields a dipole polar intensity Bd=2.6\pm 0.9~kG, consistent with that obtained from direct modelling of the Stokes V profiles. We derive a wind magnetic confinement parameter eta*\simeq 100, leading to an Alfv\'en radius RA\simeq 3-5~R*, and a Kepler radius RK\simeq 20~R*. This supports a physical scenario in which the Halpha emission and other line variability have their origin in an oblique, co-rotating 'dynamical magnetosphere' structure resulting from a magnetically channeled wind. Nevertheless, the details of the formation of spectral lines and their variability within this framework remain generally poorly understood.Comment: 18 pages, accepted by MNRAS Replaced 28 March 2015 to include corrected figure 10 (see MNRAS erratum to this effect

The VLT-FLAMES survey of massive stars: constraints on stellar evolution from the chemical compositions of rapidly rotating Galactic and Magellanic Cloud B-type stars

We have previously analysed the spectra of 135 early B-type stars in the LMC and found several groups of stars that have chemical compositions that conflict with the theory of rotational mixing. Here we extend this study to Galactic and SMC metallicities with the analysis of ~50 Galactic and ~100 SMC early B-type stars with rotational velocities up to ~300km/s. The surface nitrogen abundances are utilised as a probe of the mixing process. In the SMC, we find a population of slowly rotating nitrogen-rich stars amongst the early B type core-hydrogen burning stars, similar to the LMC. In the Galactic sample we find no significant enrichment amongst the core hydrogen-burning stars, which appears to be in contrast with the expectation from both rotating single-star and close binary evolution models. However, only a small number of the rapidly rotating stars have evolved enough to produce a significant nitrogen enrichment, and these may be analogous to the non-enriched rapid rotators previously found in the LMC sample. Finally, in each metallicity regime, a population of highly enriched supergiants is observed, which cannot be the immediate descendants of core-hydrogen burning stars. Their abundances are, however, compatible with them having gone through a previous red supergiant phase. Together, these observations paint a complex picture of the nitrogen enrichment in massive main sequence and supergiant stellar atmospheres, where age and binarity cause crucial effects. Whether rotational mixing is required to understand our results remains an open question at this time, but could be answered by identifying the true binary fraction in those groups of stars that do not agree with single-star evolutionary models (abridged).Comment: Accepted paper - 86 pages with tables and figure

Loss of KMT2C reprograms the epigenomic landscape in hPSCs resulting in NODAL overexpression and a failure of hemogenic endothelium specification

Germline or somatic variation in the family of KMT2 lysine methyltransferases have been associated with a variety of congenital disorders and cancers. Notably

NGC 1624-2: A slowly rotating, X-ray luminous Of?cp star with an extraordinarily strong magnetic field

This paper presents a first observational investigation of the faint Of?cp star NGC 1624-2, yielding important new constraints on its spectral and physical characteristics, rotation, magnetic field strength, X-ray emission and magnetospheric properties. Modeling the spectrum and spectral energy distribution, we conclude that NGC 1624-2 is a main sequence star of mass M {\simeq} 30 M{\odot}, and infer an effective temperature of 35 {\pm} 2 kK and log g = 4.0 {\pm} 0.2. Based on an extensive time series of optical spectral observations we report significant variability of a large number of spectral lines, and infer a unique period of 157.99 {\pm} 0.94 d which we interpret as the rotational period of the star. We report the detection of a very strong - 5.35 {\pm} 0.5 kG - longitudinal magnetic field , coupled with probable Zeeman splitting of Stokes I profiles of metal lines confirming a surface field modulus of 14 {\pm} 1 kG, consistent with a surface dipole of polar strength >~ 20 kG. This is the largest magnetic field ever detected in an O-type star, and the first report of Zeeman splitting of Stokes I profiles in such an object. We also report the detection of reversed Stokes V profiles associated with weak, high-excitation emission lines of O iii, which we propose may form in the close magnetosphere of the star. We analyze archival Chandra ACIS-I X-ray data, inferring a very hard spectrum with an X-ray efficiency log Lx/Lbol = -6.4, a factor of 4 larger than the canonical value for O-type stars and comparable to that of the young magnetic O-type star {\theta}1 Ori C and other Of?p stars. Finally, we examine the probable magnetospheric properties of the star, reporting in particular very strong magnetic confinement of the stellar wind, with {\eta}* {\simeq} 1.5 {\times} 10^4, and a very large Alfven radius, RAlf = 11.4 R*.Comment: 17 pages, MNRAS accepted and in pres

T-bet-mediated differentiation of the activated CD8+ T cell

The T-box transcription factor, T-bet promotes the differentiation of short-lived effector CD8+ T cells at the expense of central memory cells. How T-bet mediates these effects, and whether they are directly caused by T-bet alone are unknown, because expression of T-bet requires stimulation of the T cell by inflammatory and growth cytokines, which may have T-bet-independent functions involving T-cell differentiation. We developed an in vitro system of ectopic T-bet expression that avoids the effects of inflammatory cytokines to determine which aspects of the T-bet phenotype may be accounted for by T-bet alone. Ectopic T-bet expression by OT-I CD8+ T cells stimulated by the H2-Kb (SIINFEKL) complex and cultured with 2 ng/mL IL-2 induced a coordinated change in gene expression leading to down-regulation of CD127 and SOCS-1 and up-regulation of CD122 and IL-15 receptor α, switching the cellular survival cytokine from IL-7 to IL-15. T-bet expression and 2 ng/mL IL-2 also led to a capacity for IFN-γ and Fas ligand expression, confirming a role in eliciting these effector functions. Finally, ectopic T-bet promoted the expression of B lymphocyte-induced maturation protein 1 by OT-I cells in the presence of 20 ng/mL IL-2, providing a mechanism for the role of T-bet in driving terminal differentiation in concert with a high level of IL-2 receptor signalling