9,713 research outputs found
Modulation of galactic protons in the heliosphere during the unusual solar minimum of 2006 to 2009
The last solar minimum activity period, and the consequent minimum modulation
conditions for cosmic rays, was unusual. The highest levels of galactic protons
were recorded at Earth in late 2009 in contrast to expectations. Proton spectra
observed for 2006 to 2009 from the PAMELA cosmic ray detector on-board the
Resurs-DK1 satellite are presented together with the solutions of a
comprehensive numerical model for the solar modulation of cosmic rays. The
model is used to determine what mechanisms were mainly responsible for the
modulation of protons during this period, and why the observed spectrum for
2009 was the highest ever recorded. From mid-2006 until December 2009 we find
that the spectra became significantly softer because increasingly more low
energy protons had reached Earth. To simulate this effect, the rigidity
dependence of the diffusion coefficients had to decrease significantly below ~3
GeV. The modulation minimum period of 2009 can thus be described as relatively
more "diffusion dominated" than previous solar minima. However, we illustrate
that drifts still had played a significant role but that the observable
modulation effects were not as well correlated with the waviness of the
heliospheric current sheet as before. Protons still experienced global gradient
and curvature drifts as the heliospheric magnetic field had decreased
significantly until the end of 2009, in contrast to the moderate decreases
observed during previous minimum periods. We conclude that all modulation
processes contributed to the observed increases in the proton spectra for this
period, exhibiting an intriguing interplay of these major mechanisms
Economic reforms and rising inequality in Panama in the 1990s
In the first years of the 1990s, Panama’ s economy strongly recovered from the deep crisis at the end of the previous decade. The government implemented a stabilization programme and initiated a reform process geared at economic liberalization in the spirit of those implemented throughout Latin America. The surge in capital inflows was the key factor underlying the boom in private consumption and in construction investment, which drove the high growth performance. This allowed for a reduction of unemployment and an increase of wage employment in the formal sector of the economy. Both these labour market outcomes were conducive of a reduction in urban poverty and inequality between 1991 and 1994. Growth slowed down and poverty stabilized during the period of economic reforms implemented between 1994 and 1998, but urban inequality increased again. Applying an innovative method of counterfactual microsimulations, the paper shows that the reduction of both urban and rural poverty and inequality between 1990 and 1997 was principally due to the macroeconomic effects that led to higher rates of economic participation and employment. This positive impact of macroeconomic effects was partially offset by that of the changes in the structure of the labour market, in particular the shift towards greater demand for skilled labour relative to unskilled labour and a rise in the share of informal sector employment. These labour market adjustments associated with the process of trade liberalisation and other economic reforms had the effect of a rise in inequality
THE ATTITUDES OF OLDER SOUTH AFRICANS TOWARDS EUTHANASIA
The purpose of this study was to determine the attitudes of older South African adults (65 years and older) towards euthanasia. The subjects of the study were people 65 years of age and older who resided in homes for the aged within the rural and urban areas of the Cape Town Metropolis. An equal number of subjects from the African, Coloured and European communities were randomly selected. A biographical questionnaire, the Euthanasia Attitude Scale and the Purpose In Life Test were administered. The influence of four variables – namely age, ethnicity, meaning in life and health – was investigated. A Pearson correlation coefficient analysis and a one-way ANOVA analysis were used. Age was the only variable found to have a significant correlation with euthanasia. The findings are discussed and certain recommendations are made
Arbuscular mycorrhizal fungi for the biocontrol of plant-parasitic nematodes: a review of the mechanisms involved
Arbuscular mycorrhizal fungi (AMF) are obligate root symbionts that can protect their host plant against biotic stress factors such as plant-parasitic nematode (PPN) infection. PPN consist of a wide range of species with different life styles that can cause major damage in many important crops worldwide. Various mechanisms have been proposed to play a role in the biocontrol effect of AMF against PPN. This review presents an overview of the different mechanisms that have been proposed, and discusses into more detail the plausibility of their involvement in the biocontrol against PPN specifically. The proposed mechanisms include enhanced plant tolerance, direct competition for nutrients and space, induced systemic resistance (ISR) and altered rhizosphere interactions. Recent studies have emphasized the importance of ISR in biocontrol and are increasingly placing rhizosphere effects on the foreground as well, both of which will be the focal point of this review. Though AMF are not yet widely used in conventional agriculture, recent data help to develop a better insight into the modes of action, which will eventually lead toward future field applications of AMF against PPN. The scientific community has entered an exciting era that provides the tools to actually unravel the underlying molecular mechanisms, making this a timely opportunity for a review of our current knowledge and the challenges ahead
The "quasi-stable" lipid shelled microbubble in response to consecutive ultrasound pulses
Controlled microbubble stability upon exposure to consecutive ultrasound exposures is important for increased sensitivity in contrast enhanced ultrasound diagnostics and manipulation for localised drug release. An ultra high-speed camera operating at 13 × 10 6 frames per second is used to show that a physical instability in the encapsulating lipid shell can be promoted by ultrasound, causing loss of shell material that depends on the characteristics of the microbubble motion. This leads to well characterized disruption, and microbubbles follow an irreversible trajectory through the resonance peak, causing the evolution of specific microbubble spectral signatures. © 2012 American Institute of Physics
Intestinimonas-like bacteria are important butyrate producers that utilize Nε-fructosyllysine and lysine in formula-fed infants and adults
Our study aim is to investigate the role of Intestinimonas, Nε-fructosyllysine (FL)-degrading bacterium, in infants and adults. We used lysine and subsequently FL in anaerobic serial dilutions of stools of infants and adults to enrich lysine and FL-degrading species. The fecal microbiota of adults were able to ferment lysine and FL to butyrate. Different groups of Intestinimonas spp. were detected from all lysine enrichments whereas the FL enrichments consisted of broader taxonomic groups with a reduced abundance of Intestinimonas-related species. Remarkably, the capability to degrade FL was only observed in formula-fed but not in breast-fed infants, which may relate to high contents of FL in formulas after thermal treatment. This possibility was supported by analyzing metagenomic datasets of 3-month and 4-month infants. Our data indicate the key role of Intestinimonas-like bacteria in FL degradation in formula-fed infants and adults as a profound example of adaptation of intestinal bacteria to dietary components.Peer reviewe
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