Per què el cel és blau

i els núvols són blancs?

Archive for Novembre de 2010

A Healthy Brain Needs a Healthy Heart

Posted by Costa M. a 30 Novembre 2010


Could exercising regularly and not smoking help to delay dementia?

When the National Institutes of Health convened a panel of independent experts this past April on how to prevent Alzhei­mer’s disease, the conclusions were pretty grim. The panel determined that “no evidence of even moderate scientific quality” links anything—from herbal or nutritional supplements to prescription medications to social, economic or environmental conditions—with the slightest decrease in the risk of developing Alzheimer’s. Furthermore, the committee argued, there is little credible evidence that you can do anything to delay the kinds of memory problems that are often associated with aging. The researchers’ conclusions made headlines around the world and struck a blow at the many purveyors of “brain boosters,” “memory enhancers” and “cognitive-training software” that advertise their wares on the Web and on television. One of the panel experts later told reporters in a conference call that the group wanted to “dissuade folks from spending extraordinary amounts of money on stuff that doesn’t work.”

Image: Illustration by Ross MacDonald

 

But did the panel overstate its case? Some memory and cognition researchers privately grumbled that the conclusions were too negative—particularly with respect to the potential benefits of not smoking, treating high blood pressure and engaging in physical activity. In late September the British Journal of Sports Medicine published a few of these criticisms. As a longtime science journalist, I suspected that this is the kind of instructive controversy—with top-level people taking opposing positions—that often occurs at the leading edge of research. As I spoke with various researchers, I realized that the disagreements signaled newly emerging views of how the brain ages. Investigators are exploring whether they need to look beyond the brain to the heart to understand what happens to nerve cells over the course of decades. In the process, they are uncovering new roles for the cardiovascular system, including ones that go beyond supplying the brain with plenty of oxygen-rich blood. The findings could suggest useful avenues for delaying dementia or less severe memory problems.

Dementia, of course, is a complex biological phenomenon. Although Alzheimer’s is the most common cause of dementia in older adults, it is not the only cause. Other conditions can contribute to dementia as well, says Eric B. Larson, executive director of the Group Health Research Institute in Seattle. For example, physicians have long known that suffering a stroke, in which blood flow to the brain has been interrupted by a clot or a hemorrhage, can lead to dementia. But research over the past few years has documented the importance of very tiny strokes—strokes so small they can be detected only under a microscope after death—as another possible cause for dementia. Studies at autopsy of people who had dementia have detected many of these so-called microvascular infarcts either by themselves or along with the plaques and tangles more typical of Alzheimer’s in the brains of people with dementia. These findings suggest that most dementias, even those caused by Alzheimer’s, are triggered by multiple pathological processes and will require more than one treatment.

Proving that cardiovascular treatment is one of those approaches will take some doing. Just because microinfarcts may make dementia worse does not mean that preventing them will delay the brain’s overall deterioration. Maybe severe dementia makes people more vulnerable to microinfarcts. And just because better control of high blood pressure and increased physical activity seem to decrease a person’s risk of stroke, that does not necessarily mean they are less likely to suffer microinfarcts. Correlation, after all, does not necessarily imply causation. That scientific truism was the problem that kept bothering the panel of outside experts put together by the NIH. Thus, the expert panel concluded, with one exception, that “all existing evidence suggests that antihypertensive treatment results in no cognitive benefit.” Data showing the benefits of boosting physical activity in folks with confirmed memory problems were “preliminary.”

By Christine Gorman November 30, 2010  (Scientific American)

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WMO at UN Climate Change Conference (Cancun, Mexico)

Posted by Costa M. a 30 Novembre 2010


Like in the past, the World Meteorological Organization (WMO) will actively participate in the 16th session of the Conference of Parties of the United Nations Framework Convention on Climate Change (UNFCCC), which will be held in Cancun, Mexico, from 29 November to 10 December 2010.  WMO activities at this Conference will focus on the intensive work that is being undertaken to build the Global Framework for Climate Services (GFCS), which was decided upon by World Climate Conference-3 in 2009. A report on the GFCS will be made to the Conference in plenary session.

The WMO monitors climate change indices – over land, ocean and in the atmosphere – and the changes in the atmospheric concentrations of greenhouse gases, pollutants, ozone and other gases. National Meteorological and Hydrological Services of 189 countries contribute to its networks of systematic observations for monitoring the current climate, projecting the future climate, and for better understanding climate impacts. This scientific and technical information is the very basis for making efficient and sustainable decisions for mitigating, and adapting to, climate variability and change and for reducing vulnerability to extreme weather events.

As in previous sessions, WMO will contribute to the work of the UNFCCC Subsidiary Body for Scientific and Technological Advice (SBSTA). The 33th session, in Cancun, will be chaired by Mr Mama Konaté, Director-General of the Mali Meteorological Service and Permanent Representative of Mali with WMO, following his election at COP 15 as Chairman of SBSTA for two years.

A large number of Representatives of National Meteorological and Hydrological Services of WMO Members are expected at the Conference. A WMO position paper has been prepared. An informal meeting will be organized during the first week of COP-16 for the representatives from NMHSs to share information and discuss the position paper and the role of science in the ongoing negotiations.

Logo de la Organització Meteorológica Mundial (WMO)

 

Documentación en español de la ORGANIZACIÓN METEOROLOGICA MUNDIAL sobre el Papel de  los Servicios Meteorológicos e Hidrológicos Nacionales en la INTEGRACIÓN DE LOS SERVICIOS CLIMÁTICOS EN LA GESTIÓN DE LOS RIESGOS CLIMÁTICOS:

DOCUMENTO DE POSICIÓN DE LA OMM PREPARADO PARA APOYAR A LOS
SERVICIOS METEOROLÓGICOS E HIDROLÓGICOS NACIONALES CON VISTAS AL
16º PERÍODO DE SESIONES DE LA CONFERENCIA DE LAS PARTES EN LA
CONVENCIÓN MARCO DE LAS NACIONES UNIDAS SOBRE EL CAMBIO CLIMÁTICO
(Cancún, México, 29 de noviembre a 10 de diciembre de 2010)

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Quin estel mostra la llum del dia en què vas nàixer?‏

Posted by Costa M. a 30 Novembre 2010


“Una estrella es parte de ti, encuentrala”: així és com comença la introducció de la web que molt amablement m’ha descobert en Roger Arbusé. No sé si és gaire rigorosa, però almenys curiosa si que ho és, i bastant!

Només cal posar el dia del teu naixement i busca automaticament si hi ha un estel que estigui emetent actualment la llum del mateix dia en que tu vas nàixer: t’ho dirà i te’n donarà informació.

 

Star Merope (23 Tau) in Pleiades (M45). Author: Henryk Kowalewski. This file is licensed under the Creative Commons Attribution-Share Alike 2.5 Generic license.

I continua:

Entre los miles de millones de estrellas que hay en el cielo, hoy una te muestra la luz que nació el mismo día que tu naciste…

A pesar de la enorme velocidad de la luz (casi 300 000 kilómetros por segundo), pueden pasar muchos años desde que una estrella lanza su luz hasta que nos llega a la Tierra, hasta que realmente podemos verla. Hemos creído que sería un buen regalo para ti enseñarte cual es la estrella que lanzó su rayo de luz hacia la Tierra el mismo día que naciste. Sólo necesitamos que nos digas tu fecha de nacimiento.

This is a view of the largest stellar nursery in our local galactic neighborhood. The massive, young stellar grouping, called R136, is only a few million years old and resides in the 30 Doradus Nebula, a turbulent star-birth region in the Large Magellanic Cloud (LMC), a satellite galaxy of our Milky Way. There is no known star-forming region in our galaxy as large or as prolific as 30 Doradus. Many of the diamond-like icy blue stars are among the most massive stars known. Several of them are over 100 times more massive than our Sun. These hefty stars are destined to pop off, like a string of firecrackers, as supernovas in a few million years. This image, taken in ultraviolet, visible, and red light by Hubble's Wide Field Camera 3, spans about 100 light-years. The nebula is close enough to Earth that Hubble can resolve individual stars, giving astronomers important information about the birth and evolution of stars in the universe. The Hubble observations were taken October 20-27, 2009. The blue color is light from the hottest, most massive stars; the green from the glow of oxygen; and the red from fluorescing hydrogen. This file is in the public domain because it was created by NASA and ESA. Hubble material is copyright-free and may be freely used as in the public domain without fee, on the condition that NASA and ESA is credited as the source of the material.

Per saber-ne més:

Las estrellas brillan en el espacio y su luz, a pesar de la gran velocidad a la que se mueven, puede tardar años, siglos, incuso miles de años en alcanzarnos. De aquella estrella que ves ahí, en el cielo, nos está llegando ahora la luz que emitió hace quince años, y la luz de aquella otra quizá tenga cien, o mil años de antigüedad. ¿Qué edad tienes? ¿Hay en el cielo alguna estrella situada a la distancia justa para que la luz que nos llega hoy desde ella iniciara el viaje justo cuando viniste al mundo? La respuesta a esta pregunta la hallarás si Encuentras tu estrella.

La distancia típica entre un astro y otro es tan grande que la luz necesita muchos meses, incluso años, para salvarla. Esta página le ofrece todo un abanico de detalles sobre tu astro: nombres, brillo, color… incluso una fotografía y los datos necesarios para que puedas localizar la estrella en un mapa celeste, así podrás observarla, aunque puede que necesites un telescopio para ello.

Encuentra tu estrella y obsérvala. La luz que baña tus ojos partió de allí cuando nacías. La luz solar reflejada por la Tierra cuando naciste está llegando allí ahora. Imagina por un momento que alrededor a ese astro hubiera un planeta habitado por un ser inteligente, si estuviera apuntando hacia la Tierra con su telescopio, en este momento, estaría presenciando tu nacimiento.

Font:

http://delatierraaluniverso.cienciadirecta.com/encuentraTuEstrella.asp

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