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Contents contributed and discussions participated by Jac Londe

Jac Londe

Why is space three-dimensional? - 0 views

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    (Phys.org)-The question of why space is three-dimensional (3D) and not some other number of dimensions has puzzled philosophers and scientists since ancient Greece. Space-time overall is four-dimensional, or (3 + 1)-dimensional, where time is the fourth dimension. It's well-known that the time dimension is related to the second law of thermodynamics: time has one direction (forward) because entropy (a measure of disorder) never decreases in a closed system such as the universe.
Jac Londe

Eventbrite - Discover Great Events or Create Your Own & Sell Tickets - 0 views

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    Eventbrite brings people together through live experiences. Discover events that match your passions, or create your own with online ticketing tools.
Jac Londe

Low Budget Screen Printing: A Newbies' Guide - Go Media™ · Creativity at... - 2 views

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    When I first decided I wanted to to get into screen printing a few months ago, I really had no idea what was involved. I am an artist and I knew that I wanted to print my own designs but… Continue Reading »
Jac Londe

Sr2IrO4 - 0 views

setoftags physic science ondes
started by Jac Londe on 02 Nov 15 no follow-up yet
  • Jac Londe
     

    As it turns out, the new phase that the Hsieh group identified is precisely this type of multipolar order.


    To detect multipolar order, Hsieh's group utilized an effect called
    optical harmonic generation, which is exhibited by all solids but is
    usually extremely weak. Typically, when you look at an object
    illuminated by a single frequency of light, all of the light that you
    see reflected from the object is at that frequency. When you shine a red
    laser pointer at a wall, for example, your eye detects red light.
    However, for all materials, there is a tiny amount of light bouncing off
    at integer multiples of the incoming frequency. So with the red laser
    pointer, there will also be some blue light bouncing off of the wall.
    You just do not see it because it is such a small percentage of the
    total light. These multiples are called optical harmonics.


    The Hsieh group's experiment exploited the fact that changes in the
    symmetry of a crystal will affect the strength of each harmonic
    differently. Since the emergence of multipolar ordering changes the
    symmetry of the crystal in a very specific way-a way that can be largely
    invisible to conventional probes-their idea was that the optical
    harmonic response of a crystal could serve as a fingerprint of
    multipolar order.


    "We found that light reflected at the second harmonic frequency
    revealed a set of symmetries completely different from those of the
    known crystal structure, whereas this effect was completely absent for
    light reflected at the fundamental frequency," says Hsieh. "This is a
    very clear fingerprint of a specific type of multipolar order."


    The specific compound that the researchers studied was strontium-iridium oxide (Sr2IrO4),
    a member of the class of synthetic compounds broadly known as iridates.
    Over the past few years, there has been a lot of interest in Sr2IrO4
    owing to certain features it shares with copper-oxide-based compounds,
    or cuprates. Cuprates are the only family of materials known to exhibit
    superconductivity at high temperatures-exceeding 100 Kelvin (-173
    degrees Celsius). Structurally, iridates and cuprates are very similar.
    And like the cuprates, iridates are electrically insulating
    antiferromagnets that become increasingly metallic as electrons are
    added to or removed from them through a process called chemical doping. A
    high enough level of doping will transform cuprates into
    high-temperature superconductors, and as cuprates evolve from being
    insulators to superconductors, they first transition through a
    mysterious phase known as the pseudogap, where an additional amount of
    energy is required to strip electrons out of the material. For decades,
    scientists have debated the origin of the pseudogap and its relationship
    to superconductivity-whether it is a necessary precursor to
    superconductivity or a competing phase with a distinct set of symmetry
    properties. If that relationship were better understood, scientists
    believe, it might be possible to develop materials that superconduct at
    temperatures approaching room temperature.


    Recently, a pseudogap phase also has been observed in Sr2IrO4-and
    Hsieh's group has found that the multipolar order they have identified
    exists over a doping and temperature window where the pseudogap is
    present. The researchers are still investigating whether the two overlap
    exactly, but Hsieh says the work suggests a connection between
    multipolar order and pseudogap phenomena.


    "There is also very recent work by other groups showing signatures of
    superconductivity in Sr2IrO4 of the same variety as that found in
    cuprates," he says. "Given the highly similar phenomenology of the
    iridates and cuprates, perhaps iridates will help us resolve some of the
    longstanding debates about the relationship between the pseudogap and
    high-temperature superconductivity."


    Hsieh says the finding emphasizes the importance of developing new
    tools to try to uncover new phenomena. "This was really enabled by a
    simultaneous technique advancement," he says.


    Furthermore, he adds, these multipolar orders might exist in many more materials. "Sr2IrO4
    is the first thing we looked at, so these orders could very well be
    lurking in other materials as well, and that's exactly what we are
    pursuing next."



    Read more at: http://phys.org/news/2015-10-physicists-uncover-phase.html#jCp

Jac Londe

2015 - Learning brain - 1 views

started by Jac Londe on 01 Jun 15 no follow-up yet
  • Jac Londe
     
    Il existe une dichotomie très souvent utilisée pour caractériser les différences hémisphériques dans le traitement de l'information : l'hémisphère gauche serait plus efficace pour effectuer un traitement local et séquentiel de l'information tandis que l'hémisphère droit favorise un traitement holistique et parallèle. L'hémisphère droit serait aussi avantagé dans les traitements visuo-spatiaux et les émotions.
Jac Londe

visoft/jquery-rss · GitHub - 0 views

  • jquery-rss /
  • sdepold authored 2 years ago lib use instances + readme 2 years ago src fixed indexOf bug in ie 2 years ago .gitignore ignore node_modules 2 years ago CHANGELOG.md fixed indexOf bug in ie 2 years ago MIT-LICENSE license 2 years ago README.md added index and totalEntries 2 years ago index.html minfied version 2 years ago package.json fixed indexOf bug in ie
Jac Londe

Loi sur le droit d'auteur - 0 views

  • Loi sur le droit d’auteur1 - TITRE ABRÉGÉ 2 - DÉFINITIONS ET DISPOSITIONS INTERPRÉTATIVES 3 - PARTIE I - DROIT D’AUTEUR ET DROITS MORAUX SUR LES OEUVRES
  • PARTIE II - DROIT D’AUTEUR SUR LES PRESTATIONS, ENREGISTREMENTS SONORES ET SIGNAUX DE COMMUNICATION ET DROITS MORAUX SUR LES PRESTATIONS
  • PARTIE III - VIOLATION DU DROIT D’AUTEUR ET DES DROITS MORAUX, ET CAS D’EXCEPTION
  • ...6 more annotations...
  • PARTIE IV - RECOURS
  • PARTIE V - ADMINISTRATION
  • PARTIE VI - DIVERS
  • PARTIE VII - COMMISSION DU DROIT D’AUTEUR ET GESTION COLLECTIVE
  • PARTIE VIII - COPIE POUR USAGE PRIVÉ
  • PARTIE IX - DISPOSITIONS GÉNÉRALES
Jac Londe

Forbes list of billionaires - Wikipedia, the free encyclopedia - 0 views

  • 2013 1,426 $5.4 trillion 2012 1,226 $4.6 trillion 2011 1,210 $4.5 trillion 2010 1,011 $3.6 trillion 2009 793 $2.4 trillion 2008 1,125 $4.4 trillion 2007 946 $3.5 trillion 2006 793 $2.6 trillion 2005 691 $2.2 trillion 2004 587 $1.9 trillion 2003 476 $1.4 trillion 2002 497 $1.5 trillion 2001 538 $1.8 trillion 2000 470 $0.9 trillion$898 billion
Jac Londe

Ce poisson en armure qui tient tête aux piranhas | Passeur de sciences - 0 views

  • Ce poisson en armure qui tient tête aux piranhas
  • l'arapaima porte un gilet pare-dents. La preuve vient d'en être faite dans une étude américaine publiée en janvier par la revue Advanced Engineering Materials. Le titre – "Bataille dans l'Amazone : arapaima contre piranha" – résume bien l'approche que les auteurs, chercheurs à l'université de Californie, ont suivie : confronter les armes des piranhas, leurs dents, à l'armure de l'arapaima, ses écailles. Les premières sont impressionnantes, comme on peut le voir sur la photo ci-dessus. Même si la musculature de la bouche du piranha n'est pas particulièrement puissante, le poisson compense avec des dents aussi aiguisées que des lames de rasoir.
  • L'analyse a montré que cette zone de l'écaille est ondulée et que les bosses concentrent du calcium, ce qui explique la dureté de ce matériau bio-minéral. La partie cachée est, elle, plus mince et plus tendre. L'écaille est donc une superposition de deux épaisseurs, la première hautement minéralisée et la seconde faite de plusieurs couches de fibres de collagène. Ce matériau composite est donc à la fois très résistant en surface et flexible, une propriété indispensable à la nage du poisson. Les ondulations de la couche supérieure facilitent d'ailleurs cette flexibilité.
  • ...1 more annotation...
  • l'écaille d'arapaima appartient à cette classe de matériaux biologiques étonnants dont l'industrie pourrait s'inspirer (un "plagiat" appelé biomimétisme).
Jac Londe

We are living in a bacterial world, and it's impacting us more than previously thought - 0 views

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    ""The true number of bacterial species in the world is staggeringly huge, including bacteria now found circling the Earth in the most upper layers of our atmosphere and in the rocks deep below the sea floor," "
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    ""The true number of bacterial species in the world is staggeringly huge, including bacteria now found circling the Earth in the most upper layers of our atmosphere and in the rocks deep below the sea floor," "
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