Ricci flow on open 3-manifolds and positive scalar curvature

We show that an orientable 3-dimensional manifold M admits a complete riemannian metric of bounded geometry and uniformly pos- itive scalar curvature if and only if there exists a finite collection F of spherical space-forms such that M is a (possibly infinite) connected sum where each summand is diffeomorphic to S2xS1 or to some mem- ber of F. This result generalises G. Perelman's classification theorem for compact 3-manifolds of positive scalar curvature. The main tool is a variant of Perelman's surgery construction for Ricci flow.Comment: 65 page

On the multi-periodicities in the X-ray dipper XB 1916-053

Using the Rossi X-ray Timing Explorer and the Nordic Optical Telescope we have obtained the highest ever quality X-ray/white-light high-speed photometry of XB 1916-053. We refine the X-ray period (P_X) to 3000.6+/-0.2s via a restricted cycle counting approach. Using our complete optical lightcurve, we have extended the optical period (P_opt) ephemeris by another 4 years, providing further evidence for its stability, although a slightly longer period of 3027.555+/-0.002s now provides a marginally better fit. Moreover, modulations at both P_X and P_opt are present in the optical data, with the former dominating the nightly lightcurves (i.e. a few cycles of data). We have also attempted to determine the ``beat'' period, as seen in the repeating evolution of the X-ray dip structure, and the variation in primary dip phase. We find that a quasi-period of 4.74+/-0.05d provides the best fit to the data, even then requiring phase shifts between cycles, with the expected 3.90d ``beat'' of P_X and P_opt appearing to be less likely. Finally, considering the nature of each of these temporal phenomena, we outline possible models, which could explain all of the observed behaviour of this enigmatic source, focusing on which of P_X or P_opt is the binary period.Comment: 22 pages, 17 figures (none require colour printing), accepted for publication in MNRA

Probing open- and closed-channel p-wave resonances

We study the near-threshold molecular and collisional physics of a strong $^{40}$K p-wave Feshbach resonance through a combination of measurements, numerical calculations, and modeling. Dimer spectroscopy employs both radio-frequency spin-flip association in the MHz band and resonant association in the kHz band. Systematic uncertainty in the measured binding energy is reduced by a model that includes both the Franck-Condon overlap amplitude and inhomogeneous broadening. Coupled-channels calculations based on mass-scaled $^{39}$K potentials compare well to the observed binding energies and also reveal a low-energy p-wave shape resonance in the open channel. Contrary to conventional expectation, we observe a nonlinear variation of the binding energy with magnetic field, and explain how this arises from the interplay of the closed-channel ramping state with the near-threshold shape resonance in the open channel. We develop an analytic two-channel model that includes both resonances as well as the dipole-dipole interactions which, we show, become important at low energy. Using this parameterization of the energy dependence of the scattering phase, we can classify the studied $^{40}$K resonance as broad. Throughout the paper, we compare to the well understood s-wave case, and discuss the significant role played by van der Waals physics. The resulting understanding of the dimer physics of p-wave resonances provides a solid foundation for future exploration of few- and many-body orbital physics.Comment: v4: new appendi

An XTE Archival Search for Coherent X-ray Pulsations in LMXB 4U 1820-30

As part of a large-scale search for coherent pulsations from LMXBs in the RXTE archive, we have completed a detailed series of searches for coherent pulsations of 4U 1820-30 -- an ultracompact LMXB with a binary period of 11.4 min, located in the globular cluster NGC6624. The short binary period implies any coherent signal would be highly accelerated, so we used phase modulation searches, orbital-parameter-fitting coherent searches, and standard acceleration searches to give significant sensitivity to millisecond pulsations. We searched, in four energy bands and at a range of luminosities, a total of 34 archival RXTE observations, 32 of which had on-source integration times longer than 10 ks, and some of which were made consecutively which allowed us to combine them. We found no pulsations. Using our phase modulation search technique, which we ran on all 34 observations, we have been able to place the first stringent (95% confidence) pulsed fraction limits of <~0.8% for all realistic spin frequencies (i.e. <~2kHz) and likely companion masses (0.02Msun <= M_c <= 0.3Msun). Using our orbital-parameter-fitting coherent search, which we ran on only 11 selected observations, we have placed a pulsed fraction limit of <~0.3% for spin frequencies <~1.25kHz and companion masses M_ <= 0.106Msun. By contrast, all five LMXBs known to emit coherent pulsations have intrinsic pulsed fractions in the range 3% to 7% when pulsations are observed. Hence, our searches rule out pulsations with significantly lower pulsed fractions than those already observed.Comment: 10 pages, 5 figures, published in ApJ, the text of this astro-ph version is now identical to the text of the published versio

NFIL3 Is a Regulator of IL-12 p40 in Macrophages and Mucosal Immunity

Regulation of innate inflammatory responses against the enteric microbiota is essential for the maintenance of intestinal homeostasis. Key participants in innate defenses are macrophages. In these studies, the basic leucine zipper protein, NFIL3, is identified as a regulatory transcription factor in macrophages, controlling IL-12 p40 production induced by bacterial products and the enteric microbiota. Exposure to commensal bacteria and bacterial products induced NFIL3 in cultured macrophages and in vivo. The Il12b promoter has a putative DNA-binding element for NFIL3. Basal and LPS-activated NFIL3 binding to this site was confirmed by chromatin immunoprecipitation. LPS-induced Il12b promoter activity was inhibited by NFIL3 expression and augmented by NFIL3-short hairpin RNA in an Il12b-bacterial artificial chromosome-GFP reporter macrophage line. Il12b inhibition by NFIL3 does not require IL-10 expression, but a C-terminal minimal repression domain is necessary. Furthermore, colonic CD11b+ lamina propria mononuclear cells from Nfil3−/− mice spontaneously expressed Il12b mRNA. Importantly, lower expression of NFIL3 was observed in CD14+ lamina propria mononuclear cells from Crohn’s disease and ulcerative colitis patients compared with control subjects. Likewise, no induction of Nfil3 was observed in colons of colitis-prone Il10−/− mice transitioned from germ-free to a conventional microbiota. In conclusion, these experiments characterize NFIL3 as an Il12b transcriptional inhibitor. Interactions of macrophages with the enteric microbiota induce NFIL3 to limit their inflammatory capacity. Furthermore, altered intestinal NFIL3 expression may have implications for the pathogenesis of experimental and human inflammatory bowel diseases

Alien knowledge: Preparing student midwives for learning about infant feeding-Education practice at a UK university

Infant feeding education forms a key element in undergraduate midwifery education in the UK. Students must be prepared to provide women with support and information to make appropriate health choices for themselves and their infants. However, student midwives may already have developed opinions about infant feeding prior to commencing a midwifery education programme. The education literature suggests that existing attitudes may present a barrier to learning for some students. This particularly applies to learning in relation to sensitive or emotionally laden subjects. A review of the literature was undertaken to identify potential teaching approaches which might help students to overcome barriers to learning. Following this the evidence was utilised at a UK university to develop activities which prepare student midwives for effective learning around infant feeding. Students enrolled in the midwifery education programme were introduced to a number of activities aimed at encouraging them to accommodate unfamiliar ideas or 'alien knowledge'. These included placing students in situations which challenged their ideas, as well as engaging in group discussions and reflective exercises. The impact of these educational interventions was identified through formative and summative assessment, and through evaluation of the teaching strategy at the end of the programme. This demonstrated that, amongst those students with previously negative attitudes towards infant feeding, there was a move towards more positive attitudes and a greater confidence in providing evidence based information to parents

Chaos in King's iterative family

In this paper, the dynamics of King's family of iterative schemes for solving nonlinear equations is studied. The parameter spaces are presented, showing the complexity of the family. The analysis of the parameter space allows us to find elements of the family that have bad convergence properties, and also other ones with stable behavior. (C) 2013 Elsevier Ltd. All rights reserved.This research was supported by Ministerio de Ciencia y Tecnologia MTM2011-28636-C02-02 and FONDOCYT 2011-1-B1-33 Republica Dominicana.Cordero Barbero, A.; García Maimo, J.; Torregrosa Sánchez, JR.; Vassileva, MP.; Vindel Cañas, P. (2013). Chaos in King's iterative family. Applied Mathematics Letters. 26(8):842-848. https://doi.org/10.1016/j.aml.2013.03.012S84284826

A meta-analysis of long-term effects of conservation agriculture on maize grain yield under rain-fed conditions

Conservation agriculture involves reduced tillage, permanent soil cover and crop rotations to enhance soil fertility and to supply food from a dwindling land resource. Recently, conservation agriculture has been promoted in Southern Africa, mainly for maize-based farming systems. However, maize yields under rain-fed conditions are often variable. There is therefore a need to identify factors that influence crop yield under conservation agriculture and rain-fed conditions. Here, we studied maize grain yield data from experiments lasting 5 years and more under rain-fed conditions. We assessed the effect of long-term tillage and residue retention on maize grain yield under contrasting soil textures, nitrogen input and climate. Yield variability was measured by stability analysis. Our results show an increase in maize yield over time with conservation agriculture practices that include rotation and high input use in low rainfall areas. But we observed no difference in system stability under those conditions. We observed a strong relationship between maize grain yield and annual rainfall. Our meta-analysis gave the following findings: (1) 92% of the data show that mulch cover in high rainfall areas leads to lower yields due to waterlogging; (2) 85% of data show that soil texture is important in the temporal development of conservation agriculture effects, improved yields are likely on well-drained soils; (3) 73% of the data show that conservation agriculture practices require high inputs especially N for improved yield; (4) 63% of data show that increased yields are obtained with rotation but calculations often do not include the variations in rainfall within and between seasons; (5) 56% of the data show that reduced tillage with no mulch cover leads to lower yields in semi-arid areas; and (6) when adequate fertiliser is available, rainfall is the most important determinant of yield in southern Africa. It is clear from our results that conservation agriculture needs to be targeted and adapted to specific biophysical conditions for improved impact