Ball and socket joint. The ball and socket joint (or spheroidal joint) is a joint in which the ball-shaped surface of one rounded bone fits into the cup-like depression of another bone.
The distal bone is capable of motion around an indefinite number of axes, which have one common center. It enables the bone to move in many planes (almost all directions). An enarthrosis is a special kind of spheroidal joint in which the socket covers the sphere beyond its equator. Examples Examples of this form of articulation are found in the hip, where the rounded head of the femur (ball) rests in the cup-like acetabulum (socket) of the pelvis, and in the glenohumeral joint of the shoulder, where the rounded head of the humerus (ball) rests in the cup-like glenoid fossa (socket) of the shoulder blade. It should be noted that the shoulder includes a Sternoclavicular articulation joint.
Human skeletal changes due to bipedalism.  Hip Knee
Lessons. A comparison of the Chimp, Human, and A. afarensis femur demonstrates a rounder femoral head and longer femoral neck length in bipeds.
The femur is a critical link between the pelvis, vertebral column, and the feet in a biped because all of the body's mass is transferred to the feet via this bone during standing and movement. The gluteal muscles that link the femur to the pelvis provide the propulsive force for locomotion. The rounded femoral head articulates with the pelvis at the acetabulum (hip joint). The femoral shaft is generally straight, ending in two bulbous condyles. These are larger and more elliptical in bipeds compared to the relatively smaller and rounder condyles seen in quadrupeds. DER SPIEGEL 14/1966 - JESUS UND DIE KIRCHEN. Birth–death process. The birth–death process is a special case of continuous-time Markov process where the state transitions are of only two types: "births", which increase the state variable by one and "deaths", which decrease the state by one.
The model's name comes from a common application, the use of such models to represent the current size of a population where the transitions are literal births and deaths. Birth–death processes have many applications in demography, queueing theory, performance engineering, epidemiology or in biology. They may be used, for example to study the evolution of bacteria, the number of people with a disease within a population, or the number of customers in line at the supermarket.
When a birth occurs, the process goes from state n to n + 1. Monte Carlo method. Monte Carlo methods (or Monte Carlo experiments) are a broad class of computational algorithms that rely on repeated random sampling to obtain numerical results; typically one runs simulations many times over in order to obtain the distribution of an unknown probabilistic entity.
The name comes from the resemblance of the technique to the act of playing and recording your results in a real gambling casino. They are often used in physical and mathematical problems and are most useful when it is difficult or impossible to obtain a closed-form expression, or infeasible to apply a deterministic algorithm. Monte Carlo methods are mainly used in three distinct problems classes: optimization, numerical integration and generation of draws from a probability distribution. Astronomers discover complex organic matter exists throughout the universe. Astronomers report in the journal Nature that organic compounds of unexpected complexity exist throughout the Universe.
The results suggest that complex organic compounds are not the sole domain of life but can be made naturally by stars. Prof. Random walk. Example of eight random walks in one dimension starting at 0.
The plot shows the current position on the line (vertical axis) versus the time steps (horizontal axis). A random walk is a mathematical formalization of a path that consists of a succession of random steps. For example, the path traced by a molecule as it travels in a liquid or a gas, the search path of a foraging animal, the price of a fluctuating stock and the financial status of a gambler can all be modeled as random walks, although they may not be truly random in reality. The term random walk was first introduced by Karl Pearson in 1905. Random walks have been used in many fields: ecology, economics, psychology, computer science, physics, chemistry, and biology. Random walks explain the observed behaviors of processes in these fields, and thus serve as a fundamental model for the recorded stochastic activity.
Markov process. Markov process example Introduction A Markov process is a stochastic model that has the Markov property.
This undated image provided by the journal Science a picokeystone, extracted from an aerogel tile from the Stardust interstellar dust collector. Scientists said seven microscopic particles collected by NASA's comet-chasing spacecraft, Stardust, appear to. Special relativity. Special relativity implies a wide range of consequences, which have been experimentally verified, including length contraction, time dilation, relativistic mass, mass–energy equivalence, a universal speed limit, and relativity of simultaneity.
It has replaced the conventional notion of an absolute universal time with the notion of a time that is dependent on reference frame and spatial position. Rather than an invariant time interval between two events, there is an invariant spacetime interval. Relativistic Doppler effect. Diagram 1.
A source of light waves moving to the right, relative to observers, with velocity 0.7c. The frequency is higher for observers on the right, and lower for observers on the left. The relativistic Doppler effect is the change in frequency (and wavelength) of light, caused by the relative motion of the source and the observer (as in the classical Doppler effect), when taking into account effects described by the special theory of relativity. Maxwell's equations. Maxwell's equations are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics, and electric circuits. These fields in turn underlie modern electrical and communications technologies. Maxwell's equations describe how electric and magnetic fields are generated and altered by each other and by charges and currents. Kennedy–Thorndike experiment. Figure 1. The Kennedy–Thorndike experiment Improved variants of the Kennedy–Thorndike experiment have been conducted using optical cavities or Lunar Laser Ranging.
Ives–Stilwell experiment. Ives–Stilwell experiment (1938). "Canal rays" (a mixture of mostly H2+ and H3+ ions) were accelerated through perforated plates charged from 6,788 to 18,350 volts. The beam and its reflected image were simultaneously observed with the aid of a concave mirror offset 7° from the beam. (The offset in this illustration is exaggerated.) The Ives–Stilwell experiment tested the contribution of relativistic time dilation to the Doppler shift of light. The result was in agreement with the formula for the transverse Doppler effect, and was the first direct, quantitative confirmation of the time dilation factor. Since then, many Ives–Stilwell type experiments have been performed with increased precision. Together with the Michelson–Morley and Kennedy–Thorndike experiments, it forms one of the fundamental tests of special relativity theory. Other tests confirming the relativistic Doppler effect, are the Mössbauer rotor experiment and modern Ives–Stilwell experiments.
Michelson–Morley experiment. Figure 1. Michelson and Morley's interferometric setup, mounted on a stone slab and floating in a pool of mercury. The Michelson–Morley experiment was performed in 1887 by Albert Michelson and Edward Morley at what is now Case Western Reserve University in Cleveland, Ohio. It attempted to detect the relative motion of matter through the stationary luminiferous aether ("aether wind").
The negative results are generally considered to be the first strong evidence against the then prevalent aether theory, and initiated a line of research that eventually led to special relativity, in which the stationary aether concept has no role. [A 1] The experiment has been referred to as "the moving-off point for the theoretical aspects of the Second Scientific Revolution". [A 2] Cahier physique - physics workbook. PART I click here (from Copernicus to Newton) movie to watch: greatest discoveries in Astronomy from discovery channel (42 minutes)Willam Herschel He gave up music for astronomy.
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