Humans are still evolving—and we can watch it happen | Science | AAAS Many people think evolution requires thousands or millions of years, but biologists know it can happen fast. Now, thanks to the genomic revolution, researchers can actually track the population-level genetic shifts that mark evolution in action—and they’re doing this in humans. Two studies presented at the Biology of Genomes meeting here last week show how our genomes have changed over centuries or decades, charting how since Roman times the British have evolved to be taller and fairer, and how just in the last generation the effect of a gene that favors cigarette smoking has dwindled in some groups. “Being able to look at selection in action is exciting,” says Molly Przeworski, an evolutionary biologist at Columbia University. The studies show how the human genome quickly responds to new conditions in subtle but meaningful ways, she says. Evolutionary biologists have long concentrated on the role of new mutations in generating new traits. Other researchers praise the new technique.
Finding faster-than-light particles by weighing them In a new paper accepted by the journal Astroparticle Physics, Robert Ehrlich, a recently retired physicist from George Mason University, claims that the neutrino is very likely a tachyon or faster-than-light particle. There have been many such claims, the last being in 2011 when the "OPERA" experiment measured the speed of neutrinos and claimed they travelled a tiny amount faster than light. However, when their speed was measured again the original result was found to be in error – the result of a loose cable no less. Ehrlich's new claim of faster-than-light neutrinos is based on a much more sensitive method than measuring their speed, namely by finding their mass. Skeptics of tachyons often cite conflicts with relativity theory. Several decades after tachyons were first proposed, and after many fruitless searches for them, three theorists Chodos, Hauser, and Kostelecky suggested in 1985 that they might be hiding in plain sight – specifically that neutrinos are tachyons.
Ils ont fabriqué un trou de ver... magnétique ! - Science-et-vie.com Les fans de Star Trek ou d'Interstellar connaissent bien ces étranges objets astrophysiques : les trous de ver relient entre eux deux points éloignés de l'Univers, à la faveur des plis de l'espace-temps, comme le prévoit la relativité générale théorisée par Albert Einstein. Qu'on emprunte un trou de ver, et on se retrouverait (théoriquement) dans un autre endroit et à une autre époque ! Dépassant ainsi, de fait, la vitesse de la lumière, limite infranchissable d'après la même théorie. Objet mythique en astrophysique, un trou de ver est un raccourci spatio-temporel Voilà des décennies que les physiciens donnent la chasse à ces formations si particulières, depuis qu'elles ont été décrites par Einstein et Rosen en 1936 (qui les appelaient "ponts"), puis par John Wheeler (qui baptisa les "trous de ver", wormholes en anglais) à la fin des années 50. Une sphère de métamatériaux forme le trou de ver magnétique Voyager dans le temps reste un rêve inaccessible —Fiorenza Gracci Au-delà du réel.
The LHC Disproves the Existence of Ghosts and the Paranormal In Brief Renowned physicist Brian Cox has claimed that the lack of any physical evidence being detected by the highly sensitive Large Hadron Collider disproves the existence of ghosts.Four in 10 Americans reportedly believe in ghosts, a figure that belies the lack of scientific evidence behind their existence. The LHC Looks like the Ghostbusters have some competition, and it’s renowned physicist and science communicator Brian Cox. But rather than bust some ghosts, it looks like he’s more in the business of destroying the idea of the paranormal entirely. He wasn’t just looking to spread some knowledge to the 4 in 10 Americans who believe in ghosts, though — he was sharing a simple conclusion he has reached by working with the Large Hadron Collider (LHC). The LHC is the largest and most powerful particle accelerator that humanity has ever built. No Evidence, No Ghosts Cox’s point relies heavily on the LHC’s ability to pick up the tiniest bursts of energy found in particle collisions.
Medical Xpress: Astrocytes found to keep time for brain, behavior Until recently, work on biological clocks that dictate daily fluctuations in most body functions, including core body temperature and alertness, focused on neurons, those electrically excitable cells that are the divas of the central nervous system. Asked to define the body's master clock, biologists would say it is two small spheres—the suprachiasmatic nuclei, or SCN—in the brain that consist of 20,000 neurons. They likely wouldn't even mention the 6,000 astroglia mixed in with the neurons, said Erik Herzog, a neuroscientist in Arts & Sciences at Washington University in St. Louis. The astroglia, or astrocytes, were passed over in silence partly because they weren't considered to be important. Then two things happened. So for a neuroscientist like Herzog, the obvious question was: What were the astrocytes doing in the SCN? Herzog answered the first question in 2005—yes, astrocytes have daily clocks—but then the research got stuck. Astrocytes clock in But that is exactly what they did.
Alcubierre Warp Drive Time Travel An Alcubierre Warp Drive stretches spacetime in a wave causing the fabric of space ahead of a spacecraft to contract and the space behind it to expand. The ship can ride the wave to accelerate to high speeds and time travel. The Alcubierre drive, also known as the Alcubierre metric or Warp Drive, is a mathematical model of a spacetime exhibiting features reminiscent of the fictional "warp drive" from Star Trek, which can travel "faster than light" (although not in a local sense - see below). The key characteristics of the application of Alcubierre warp drives for time control and time travel are presented in the picture below. This is followed by more detail describing the effect below. Alcubierre Warp Drive Description In 1994, the Mexican physicist Miguel Alcubierre proposed a method of stretching space in a wave which would in theory cause the fabric of space ahead of a spacecraft to contract and the space behind it to expand. Alcubierre Metric Mathematics of the Alcubierre drive
ADN, chromosomes, gènes : notions-clés ADN, chromosomes et gènes : le plan de notre organisme Le corps humain est constitué de milliards de ”cellules” comportant chacune un noyau. Ce noyau renferme toute notre information génétique. Celle-ci est contenue dans nos chromosomes qui contiennent eux-mêmes notre ADN. Qu’est-ce qu’un chromosome ? Les chromosomes sont constitués d’ADN qui porte les gènes (20 000 environ). Les 22 premières paires sont appelées autosomes. Qu’est-ce que l’ADN ? L’ADN, qui constitue nos chromosomes, porte les gènes (20 000 environ). Le gène est un morceau de cet ADN qui correspond à une information génétique particulière qui code pour une protéine unique. Le gène : pivot du bon fonctionnement de notre corps Les gènes indiquent à chaque cellule son rôle dans l’organisme. Une anomalie génétique (mutation ou anomalie chromosomique) peut perturber la fabrication des protéines. Une anomalie génétique n’aboutit pas toujours à une maladie. Attention, nous ne sommes pas « tout génétique » !
Quantum mechanics - Wikipedia Description of physical properties at the atomic and subatomic scale Quantum mechanics is a fundamental theory in physics that describes the behavior of nature at and below the scale of atoms.[2]: 1.1 It is the foundation of all quantum physics including quantum chemistry, quantum field theory, quantum technology, and quantum information science. Classical physics, the collection of theories that existed before the advent of quantum mechanics, describes many aspects of nature at an ordinary (macroscopic) scale, but is not sufficient for describing them at small (atomic and subatomic) scales. Quantum mechanics arose gradually from theories to explain observations that could not be reconciled with classical physics, such as Max Planck's solution in 1900 to the black-body radiation problem, and the correspondence between energy and frequency in Albert Einstein's 1905 paper, which explained the photoelectric effect. Overview and fundamental concepts Mathematical formulation . and , where Here .
Le génome de toutes les plantes à fleurs vient d'être reconstitué - Sciencesetavenir.fr ANCÊTRE. Il fallait y penser. Au vu des dizaines de génomes de plantes à fleur qui ont été décryptés depuis maintenant 17 ans (le séquençage du patrimoine génétique de la première plante Arabidopsis thaliana remonte à l'an 2000), pourquoi ne pas chercher ces gènes qui les réunissent toutes et permettrait ainsi de remonter au génome de leur ancêtre commun? Le résultat vient d'être publié dans Nature genetics. "Nous avons donc comparé les génomes de plantes qu'elles soient monocotylédones (les céréales) ou dicotylédones (légumineuses, crucifères, arbres fruitiers), expose Jérôme Salse, chercheur à l'Unité "Génétique, diversité et écophysiologie des céréales" conjointe à l'Inra et à l'Université de Clermont-Ferrand. Arbre généalogique (branches noires) illustrant l'évolution des génomes de plantes modernes à partir de leur ancêtre commun disparu (au centre). La plasticité génétique à l'origine du succès des plantes à fleur MUTATIONS.
The Phenomenon Of Light Generation Through The Crushing Of Materials Is Called? Answer: Triboluminescence The word might sound rather scientific, and maybe a little alien in nature (“triboluminescence” does sound a whole lot like a problem the crew of the Enterprise might run into, after all), but it’s a down-to-Earth phenomenon you may have even experienced yourself. Triboluminescence is light created when crushing, tearing, or other mechanical action triggers the breakdown of chemical bonds in a material (or when peeling adhesive tapes). A popular classroom demonstration of this phenomenon, for example, is to give students rolls of Wint-O-Green Mint Lifesaver candies, enter a darkened room, and then have the students—much to their delight—throw tons of the candies into their mouths and chomp on them vigorously with their mouths open. Human fascination with the phenomenon isn’t thanks to recent scientific discovery, however. Image courtesy of H.
Pourquoi parlons-nous avec les mains ? Pourquoi certaintes personnes ne peuvent-elles s’empêcher de remuer les mains en parlant ? C'est que, dans le cerveau humain, les zones du langage et celles des mouvements semblent liées. Par exemple, lorsque nous disons le mot « jeter », « prendre » ou « pousser », notre main est automatiquement impliquée de façon involontaire : la partie du cerveau qui pilote ses gestes est « préallumée » et commence à s’activer, que nous le voulions ou non. Ainsi, la plupart des verbes d’action entraînent, dans notre cerveau, une préparation de l’action de nos mains. Le neuroscientifique Nikola Vukovic de l’université d’Aarhus aux Pays-Bas a fait une expérience pour le montrer : en bloquant l’activité de la zone cérébrale commandant le mouvement des mains à l’aide d’ondes magnétiques qui brouillent le fonctionnement des neurones, ils ont ralenti la compréhension de mots désignant des verbes d’action.
Better Nuclear Power Through Ping Pong The lab is deep-space quiet. A long, narrow hallway hung with fluorescent lights extends to my left. Four or five doors interrupt the flow of drywall. A few of those doors are open, the occupants of the rooms within now out in the hall and staring, ears plugged in anticipation. A technician flips a small lever to activate the vacuum pumps on an 18-foot cannon that is tented in bulletproof polycarbonate. Advertisement - Continue Reading Below The pumps chitter away, sucking air from the barrel. The cannon is a prop, really—something to get potential investors excited about the technology. Conventional reactors use designs that remain basically unchanged since the 1950s. That's the secret to breaking the sound barrier with a ping pong ball: If any air were left in front of the ball, it would crush the ball under the force of the acceleration. What does any of that have to do with ping pong? Two Types of Nuclear Reactions Slow U-235 is the enriched uranium isotope. Fast
Medical Xpress: Electrical 'switch' in brain's capillary network monitors activity and controls blood flow All it takes is the flip of a protein "switch" within the tiny wire-like capillaries of the brain to increase the blood flow that ensures optimal brain function. New research has uncovered that capillaries have the capacity to both sense brain activity and generate an electrical vasodilatory signal to evoke blood flow and direct nutrients to nourish hard-working neurons. These findings were reported online in Nature Neuroscience. When there is an increase in brain activity, there is an increase in blood flow, says Thomas Longden, Ph.D., assistant professor of pharmacology at the Larner College of Medicine at the University of Vermont and first author of the study. "The area of the brain covered by the capillaries—the smallest blood vessels in the body—vastly surpasses the area covered by arterioles. This ideally positions them for monitoring neuronal activity and controlling blood flow." Explore further: A glitch in 'gatekeeper cells' slowly suffocates the brain