8,540 research outputs found
Helminths in the hygiene hypothesis:Sooner or later?
There is increasing recognition that exposures to infectious agents evoke fundamental effects on the development and behaviour of the immune system. Moreover, where infections (especially parasitic infections) have declined, immune responses appear to be increasingly prone to hyperactivity. For example, epidemiological studies of parasite-endemic areas indicate that prenatal or early-life experience of infections can imprint an individual's immunological reactivity. However, the ability of helminths to dampen pathology in established inflammatory diseases implies that they can have therapeutic effects even if the immune system has developed in a low-infection setting. With recent investigations of how parasites are able to modulate host immune pathology at the level of individual parasite molecules and host cell populations, we are now able to dissect the nature of the host–parasite interaction at both the initiation and recall phases of the immune response. Thus the question remains – is the influence of parasites on immunity one that acts primarily in early life, and at initiation of the immune response, or in adulthood and when recall responses occur? In short, parasite immunosuppression – sooner or later
STOL aircraft transient ground effects. Part 1: Fundamental analytical study
The first phases of a fundamental analytical study of STOL ground effects were presented. Ground effects were studied in two dimensions to establish the importance of nonlinear effects, to examine transient aspects of ascent and descent near the ground, and to study the modelling of the jet impingement on the ground. Powered lift system effects were treated using the jet-flap analogy. The status of a three-dimensional jet-wing ground effect method was presented. It was shown, for two-dimensional unblown airfoils, that the transient effects are small and are primarily due to airfoil/freestream/ground orientation rather than to unsteady effects. The three-dimensional study showed phenomena similar to the two-dimensional results. For unblown wings, the wing/freestream/ground orientation effects were shown to be of the same order of magnitude as for unblown airfoils. This may be used to study the nonplanar, nonlinear, jet-wing ground effect
Design and in Vitro Evaluation of a New Nano-Microparticulate System for Enhanced Aqueous-Phase Solubility of Curcumin
Curcumin, a yellow polyphenol derived from the turmeric Curcuma longa, has been associated with a diverse therapeutic potential including anti-inflammatory, antioxidant, antiviral, and anticancer properties. However, the poor aqueous solubility and low bioavailability of curcumin have limited its potential when administrated orally. In this study, curcumin was encapsulated in a series of novel nano-microparticulate systems developed to improve its aqueous solubility and stability. The nano-microparticulate systems are based entirely on biocompatible, biodegradable, and edible polymers including chitosan, alginate, and carrageenan. The particles were synthesized via ionotropic gelation. Encapsulating the curcumin into the hydrogel nanoparticles yielded a homogenous curcumin dispersion in aqueous solution compared to the free form of curcumin. Also, the in vitro release profile showed up to 95% release of curcumin from the developed nano-microparticulate systems after 9 hours in PBS at pH 7.4 when freeze-dried particles were used.CONACYTCUPIAPharmac
Hubble Space Telescope Ultraviolet Imaging and High-Resolution Spectroscopy of Water Photodissociation Products in Comet Hyakutake (C/1996 B2)
Comet Hyakutake (C/1996 B2) provided a target of opportunity for performing a systematic study of water photodissociation products in which we obtained data from three instruments on the Hubble Space Telescope (HST). The HST Goddard High Resolution Spectrograph (GHRS) was used to measure the line profile of hydrogen Lyα (H Lyα) at six locations around the coma of the comet, ranging from the nucleus to a displacement of 100,000 km, and covering different directions compared with the comet-sun line. GHRS yielded line profiles with a spectral resolution (FWHM ~4 km s^(-1)) that was a factor of 2-3 better than any previous H Lyα or Hα ground-based measurements. The Wide Field Planetary Camera 2 (WFPC2) and the Woods filter were used to obtain H Lyα images of the inner coma. The faint object spectrograph (FOS) was used to determine the OH production rate and monitor its variation throughout the HST observing sequence. The GHRS H Lyα line profiles show the behavior of a line profile that is optically thick in the core for positions near the nucleus (<5000 km) and gradually becoming more optically thin at larger displacements and lower column abundances. A composite H Lyα image constructed from four separate WFPC2 exposures is consistent with the relative fluxes seen in GHRS observations and clearly shows the dayside enhancement of a solar illuminated optically thick coma. These data were analyzed self-consistently to test our understanding of the detailed physics and chemistry of the expanding coma and our ability to obtain accurate water production rates from remote observations of gaseous hydrogen (H) and hydroxyl (OH), the major water dissociation products. Our hybrid kinetic/hydrodynamic model of the coma combined with a spherical radiative transfer calculation is able to account for (1) the velocity distribution of H atoms, (2) the spatial distribution of the H Lyα emission in the inner coma, and (3) the absolute intensities of H and OH emissions, giving a water production rate of (2.6 ± 0.4) × 10^(29) s^(-1) on 1996 April 4
Secondary literacy across the curriculum: Challenges and possibilities
This paper discusses the challenges and possibilities attendant upon successfully implementing literacy across the curriculum initiatives – or ‘school language policies’ as they have come to be known - particularly at the secondary or high school level. It provides a theoretical background to these issues, exploring previous academic discussions of school language policies, and highlights key areas of concern as well as opportunity with respect to school implementation of such policies. As such, it provides a necessary conceptual background to the subsequent papers in this special issue, which focus upon the Secondary Schools’ Literacy Initiative (SSLI) – a New Zealand funded programme that aims to establish cross-curricular language and literacy policies in secondary schools
Micronutrient fertilization on a typic acrorthox at Manaus, Brazil.
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Phosphorus fertilizer placement and profitability.
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Lime requirements and downward movement of Ca and Mg.
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