background preloader

Brane cosmology

Brane cosmology
Brane cosmology refers to several theories in particle physics and cosmology related to string theory, superstring theory and M-theory. Brane and bulk[edit] The central idea is that the visible, four-dimensional universe is restricted to a brane inside a higher-dimensional space, called the "bulk" (also known as "hyperspace"). Why gravity is weak and the cosmological constant is small[edit] Some versions of brane cosmology, based on the large extra dimension idea, can explain the weakness of gravity relative to the other fundamental forces of nature, thus solving the so-called hierarchy problem. Models of brane cosmology[edit] One of the earliest documented attempts to apply brane cosmology as part of a conceptual theory is dated to 1983.[5] The authors discussed the possibility that the Universe has dimensions, but ordinary particles are confined in a potential well which is narrow along spatial directions and flat along three others, and proposed a particular five-dimensional model. Related:  .caisson test.caisson test.caisson.caisson

Biofilm IUPAC definition Aggregate of microorganisms in which cells that are frequently embedded within a self-produced matrix of extracellular polymeric substance (EPS) adhere to each other and/or to a surface. Note 1: A biofilm is a fixed system that can be adapted internally to environmental conditions by its inhabitants. Note 2: The self-produced matrix of extracellular polymeric substance, which is also referred to as slime, is a polymeric conglomeration generally composed of extracellularbiopolymers in various structural forms.[1] Microbes form a biofilm in response to many factors, which may include cellular recognition of specific or non-specific attachment sites on a surface, nutritional cues, or in some cases, by exposure of planktonic cells to sub-inhibitory concentrations of antibiotics.[4][5] When a cell switches to the biofilm mode of growth, it undergoes a phenotypic shift in behavior in which large suites of genes are differentially regulated.[6] Formation[edit] Development[edit]

The Brane multiverse Bienvenue sur FORESTIA – un jeu de simulation forestière sur SCIENCE EN JEU Savais-tu que? Il faut 12 arbres adultes pour produire l'oxygène consommé par un humain en une année! Bienvenue sur FORESTIA, le jeu de simulation et de stratégie où tu aménages ta forêt! Viens relever le formidable défi de l’aménagement forestier durable! Dans cette nouvelle version de FORESTIA : Réalise des inventaires forestiers Approvisionne des usines à l’aide d’abatteuses multifonctionnelles Combats de terribles incendies de forêt Reboise ta forêt Effectue des coupes de jardinage Fabrique des objets dans tes usines Protège une section de forêt qui renferme un écosystème exceptionnel Sauras-tu atteindre l’équilibre social, économique et environnemental? Nouveaux guides pédagogiques et nouveau mini-jeu à découvrir! Ces guides s’ajoutent aux deux guides pédagogiques qui appuient déjà depuis plus d’un an son utilisation par les enseignantes et enseignants de géographie primaire (3e cycle) (Demandez le guide!) Science en Jeu inaugure une forêt… virtuelle

The Inflationary universe Cell migration Cell migration is a central process in the development and maintenance of multicellular organisms. Tissue formation during embryonic development, wound healing and immune responses all require the orchestrated movement of cells in particular directions to specific locations. Errors during this process have serious consequences, including intellectual disability, vascular disease, tumor formation and metastasis. Cell migration studies[edit] The migration of cultured cells attached to a surface is commonly studied using microscopy. Common features[edit] The processes underlying mammalian cell migration are believed to be consistent with those of (non-spermatozooic) locomotion.[3] Observations in common include: cytoplasmic displacement at leading edge (front)laminar removal of dorsally-accumulated debris toward trailing edge (back) Other eukaryotic cells are observed to migrate similarly. Molecular processes of migration[edit] Two different models for how cells move. Leading Edge[edit]

The quilted universe article - Réflexion philosophique sur la réalité Vous avez dit réalité ? Mais tout d'abord, qu'est-ce que la réalité ? Alors, hum, réalité. C'est ce qui est réel, vrai, et que l'on peut voir entendre ou toucher. Il me semble que c'est à cela que l'on pense tout de suite non? Regardons ce qu'en dit Encarta® tiens : "Ce qui existe". De son côté, Wikipedia® nous dit que "La réalité est dans l'usage courant tout ce qui existe. Si l'on admet donc que la réalité est ce qui existe, il nous faudra d'abord savoir comment l'on défini si quelque chose existe ou pas. Ce qui existe, ce serait ce qui est sensible par un ou plusieurs de nos 5 sens, parce que ce sont nos principaux moyens d'interaction avec notre environnement extérieur. La vue Sens de la vision. Dans les définitions habituelles de la vue, on nous dit que l'oeil sert à percevoir le monde extérieur. Arrêtons-nous sur cette conclusion un instant. D'ailleurs regardez la photo au début de cet article, vous voyez quoi? Conclusion : votre écran vous trompe. Autre exemple. La suite !

Eternal inflation Eternal inflation is predicted by many different models of cosmic inflation. MIT professor Alan H. Guth proposed an inflation model involving a "false vacuum" phase with positive vacuum energy. Parts of the Universe in that phase inflate, and only occasionally decay to lower-energy, non-inflating phases or the ground state. In chaotic inflation, proposed by physicist Andrei Linde, the peaks in the evolution of a scalar field (determining the energy of the vacuum) correspond to regions of rapid inflation which dominate. Alan Guth's 2007 paper, "Eternal inflation and its implications",[1] details what is now known on the subject, and demonstrates that this particular flavor of inflationary universe theory is relatively current, or is still considered viable, more than 20 years after its inception.[2] [3][4] Inflation and the multiverse[edit] Both Linde and Guth believe that inflationary models of the early universe most likely lead to a multiverse but more proof is required. History[edit]

Cell surface receptor The seven-transmembrane α-helix structure of a G-protein-coupled receptor Structure and mechanism[edit] There are various kinds, such as glycoprotein and lipoprotein.[1] Hundreds of different receptors are known and many more are yet to be discovered.[2][3] Almost all known membrane receptors are transmembrane proteins. Domains[edit] Like any integral membrane protein, a transmembrane receptor may be subdivided into three parts or domains. Extracellular domain[edit] Transmembrane domain[edit] In the majority of receptors for which structural evidence exists, transmembrane alpha helices make up most of the transmembrane domain. Intracellular domain[edit] The intracellular (or cytoplasmic) domain of the receptor interacts with the interior of the cell or organelle, relaying the signal. Signal transduction[edit] External reactions and internal reactions for signal transduction (click to enlarge) Signal transduction through membrane receptors usually requires four characters: See also[edit]

The Cyclic multiverse Agir en faveur de l’engagement et de la motivation des élèves Parmi les sept facteurs déterminants du climat scolaire, les stratégies pédagogiques sont favorables à l’engagement et à la motivation des élèves. S’informer “En ce qui concerne la relation pédagogique, le choix s’oriente vers un style qui promeut la coopération et évite les deux pièges bien connus de l’autoritarisme et du laisser-faire […]. L’adulte ne se défait pas de son rôle de leader mais il autorise et aide l’auto-organisation du groupe et l’autodiscipline du jeune en particulier par la négociation des règles de vie et le partage des responsabilités.” “Améliorer le climat passe par l’augmentation de l’identification collective dans les établissements, celle des professionnels comme celle des élèves.” Agir Un bon climat scolaire et le bien être à l’école, au collège ou au lycée, du point de vue des élèves, reposent sur un certain nombre de principes éducatifs et pédagogiques. Dans l’établissement Dans la classe Avec l’élève S'inspirer

Four-dimensional space In modern physics, space and time are unified in a four-dimensional Minkowski continuum called spacetime, whose metric treats the time dimension differently from the three spatial dimensions (see below for the definition of the Minkowski metric/pairing). Spacetime is not a Euclidean space. History[edit] An arithmetic of four dimensions called quaternions was defined by William Rowan Hamilton in 1843. This associative algebra was the source of the science of vector analysis in three dimensions as recounted in A History of Vector Analysis. Soon after tessarines and coquaternions were introduced as other four-dimensional algebras over R. One of the first major expositors of the fourth dimension was Charles Howard Hinton, starting in 1880 with his essay What is the Fourth Dimension? Little, if anything, is gained by representing the fourth Euclidean dimension as time. Vectors[edit] This can be written in terms of the four standard basis vectors (e1, e2, e3, e4), given by Geometry[edit]

Beautiful Mathematical GIFs Will Mesmerize You Digital artist and physics PhD student Dave Whyte is dazzling our computer screens with his mesmerizing GIFs that are the perfect marriage of mathematics and art. And we can’t stop watching them. Whyte shares his brilliant, procrastination-fueling creations on an almost daily basis on his Tumblr account, Bees & Bombs. Whyte studies the physics of foam and told Colossal that his first geometric GIFs riffed on computational modules that he was exploring as an undergraduate student. [Via Colossal, io9 and Bees & Bombs]

Simulated reality Simulated reality is the hypothesis that reality could be simulated—for example by computer simulation—to a degree indistinguishable from "true" reality. It could contain conscious minds which may or may not be fully aware that they are living inside a simulation. This is quite different from the current, technologically achievable concept of virtual reality. Virtual reality is easily distinguished from the experience of actuality; participants are never in doubt about the nature of what they experience. There has been much debate over this topic, ranging from philosophical discourse to practical applications in computing. Types of simulation[edit] Brain-computer interface[edit] Virtual people[edit] In a virtual-people simulation, every inhabitant is a native of the simulated world. Arguments[edit] Simulation argument[edit] 1. 2. 3. In greater detail, Bostrom is attempting to prove a tripartite disjunction, that at least one of these propositions must be true. Relativity of reality[edit]