" For a detailed description of the differences between fermions and bosons, see the article on identical particles. In the Standard Model, the theory of the electroweak interaction (which describes the weak and electromagnetic interactions) is combined with the theory of quantum chromodynamics . All of these theories are gauge theories, meaning that they model the forces between fermions by coupling them to bosons which mediate (or "carry") the forces. The Lagrangian of each set of mediating bosons is invariant under a transformation called a gauge transformation, so these mediating bosons are referred to as gauge bosons. The bosons in the Standard Model are: Unsolved problems in physics: Parameters in the Standard Model: What gives rise to the Standard Model of particle physics? Why do its particle masses and coupling constants possess the values we have measured? Does the Higgs boson predicted by the model really exist? Why are there three generations of particles in the Standard Model? Is the Standard Model reality, a good approximation to reality, or fatally flawed? Photons, which mediate the electromagnetic interaction. W and Z bosons, which mediate the weak nuclear force Eight species of gluons, which mediate the strong nuclear force. Six of these gluons are labelled as pairs of "colors" and "anti-colors" (for example, a gluon can carry "red" and "anti-green". Model Boat Plan) The other two species are a more complex mix of colors and anti-colors. The Higgs bosons, which induce spontaneous symmetry breaking of the gauge groups and are responsible for the existence of inertial mass. "

" It displays the time and is done; it does not wait for events. For more information, see: Event-driven_programming Implementations The pattern was first described in 1979 by Trygve Reenskaug, then working on Smalltalk at Xerox research labs. This original implementation inspired many other GUI frameworks such as: The NeXTSTEP and OPENSTEP development environments encourage the use of MVC. Cocoa, based on these technologies, also uses MVC. Microsoft Foundation Classes (MFC). The Java Swing GUI library. More recently there have been attempts to apply MVC architectures for web-based interfaces. Scale Model Boat In the design of web applications, MVC is also known as a "Model 2" architecture in Sun parlance. Complex web applications continue to be more difficult to design than traditional applications, and MVC is being pushed as a potential solution to these difficulties. "