Par trichard le 9 Septembre 2013 à 11:15
Genetically modified foods have been demonized in recent years by health advocates and environmentalists alike. If we look at the history of food cultivation, however, it is apparent we've been eating them all along. SA editor Eric R. Olson explains.
Par trichard le 4 Septembre 2013 à 12:26
History of Earth is part of the universe's. The development of life on Earth is related to the particularities of the planet. Life emerges from inert nature. Living beings have a unique organization and operation. Their shapes show a huge diversity, variable over time, following the evolution.
L’histoire de la Terre s’inscrit dans celle de l’Univers. Le développement de la vie sur Terre est lié à des particularités de la planète. La vie émerge de la nature inerte. Les êtres vivants possèdent une organisation et un fonctionnement propres. Leurs formes montrent une diversité immense, variable dans le temps, au gré de l’évolution.
§ Où la vie est-elle possible ?
présentation des planètes avec Celestia : http://www.ikiru.ch/celestia/index.php?menu=divers&ssmenu=educatif
prendre en note -> tableau de comparaison des planètes : rayon + T°K
4X2=8 planètes : MeVeTeMa JuSaUrNe
Whole sun imaged for the first time : http://www.newscientist.com/blogs/nstv/2011/02/whole-sun-imaged-for-the-first-time.html
Activité2/ Comparaison des planètes de notre système solaire / tableau
Logiciel Planète 3D / Perez : http://svtolog.free.fr/article.php3?id_article=274
site sur le Syst sol : http://system.solaire.free.fr/sommaire.htm
compléter tableau de comparaison des planètes : distance au soleil / température de surface / présence d'atmosphère / composition, ...
explore solar system : http://www.bbc.co.uk/solarsystem/
Système solaire, étoile, planète gazeuse ext, planète rocheuse int, ceinture d'astéroïdes, comète.
Par trichard le 9 Juin 2013 à 18:49
<iframe frameborder="0" width="480" height="270" src="http://www.dailymotion.com/embed/video/xxfst6?&syndication=115573"></iframe><br /><a href="http://www.dailymotion.com/video/xxfst6_la-surconsommation_webcam" target="_blank">La surconsommation</a> <i>par <a href="http://www.dailymotion.com/rikiai" target="_blank">rikiai</a></i>
Par trichard le 18 Avril 2013 à 11:42
- 18 April 2013
- Magazine issue 2913. Subscribe and save
- For similar stories, visit the Editorials Topic Guide
Lab-grown organs could be a boon for those on transplant waiting lists – but they also raise ethical questions
THE first heart transplant, back in 1967, was as shocking to some people as it was wondrous to others. The use of parts from one person to heal another – especially culturally resonant parts from dead donors – was a viscerally unsettling prospect.
Today, most of us consider a transplant to be a boon, albeit one that can only be granted to a limited number of people. Despite concerted efforts to increase the supply of donor organs, waiting lists are still lengthy in many places. What a further boon it would be, then, if we could make as many organs as we needed.
In this respect, the successful implantation of a lab-grown kidney in a rat this week is good news. Researchers are working hard to make the same techniques work with other organs – and in humans (see "Lab-grown kidney blazes trail for bespoke donor organs").
Even if all goes smoothly, it will be a long time before we take the first step: renewing donated organs that would otherwise go to waste because they are unsuitable for would-be recipients or in poor condition. These organs could be made viable by stripping them of donor cells, then recoating them with a patient's own.
This will not in itself solve the organ shortage. In the US, for example, around 18 per cent of donated kidneys go unused. Adding these to the 18,000 transplants conducted each year won't eliminate the 100,000-strong waiting list, although it will save many lives.
There is an alternative, albeit more distant. We could harvest organs from animals (most likely pigs) which can be stripped and then "humanised". If it works, this could let us meet the demand for organs in its entirety.
Would patients, and society, accept this? Almost 20 years ago, a front cover of asked: "Will a pig's heart end up in you?" That question remains open, as direct transplantation of major organs across species boundaries still hasn't been made to work.
But millions of people today do have body parts derived from pigs, such as heart valves and hernia patches. Pragmatism has won out over squeamishness, and acceptance will probably keep growing. The time may well come when the transplant of an animal's heart, too, seems more wondrous than shocking.
boon1.something to be thankful for; blessing; benefit.2.something that is asked; a favor sought.
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