Three waves of variation study

By Catharine Paddock PhD The ancestors of Native American populations from the tip of Chile in the south to Canada in the north, migrated from Asia in at least three waves, according to a new international study published online in Nature this week that involved over 60 investigators in 11 countries in the Americas, plus four in Europe, and Russia. In what they describe as the most comprehensive survey of genetic diversity in Native Americans so far, the researchers studied variation in Native American DNA sequences.

Three waves of variation study

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Because the phenomenon of rogue waves is still a matter of active research, it is premature to state clearly what the most common causes are or whether they vary from place to place. The areas of highest predictable risk appear to be where a strong current runs counter to the primary direction of travel of the waves; the area near Cape Agulhas off the southern tip of Africa is one such area; the warm Agulhas Current runs to the southwest, while the dominant winds are westerlies.

However, since this thesis does not explain the existence of all waves that have been detected, several different mechanisms are likely, with localised variation. Suggested mechanisms for freak waves include the following: According to this hypothesis, coast shape or seabed shape directs several small waves to meet in phase.

Their crest heights combine to create a freak wave. This results in shortening of wavelength, causing shoaling i.

GATE Coaching at Engineers Institute of India - EII The information carried by the signal has a certain bandwidth associated with it, and the carrier must have a channel width at least as great as the information bandwidth. For regular amplitude-modulated AM broadcasting the radio-frequency bandwidth must be twice the information-frequency bandwidth.
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The NLS can be used in deep water conditions. In shallow water, waves are described by the Korteweg—de Vries equation or the Boussinesq equation. These equations also have non-linear contributions and show solitary-wave solutions.

Radio technology | History, Principles, Types, & Facts | initiativeblog.com

As wind blows over the ocean, energy is transferred to the sea surface. When strong winds from a storm happen to blow in the opposing direction of the ocean current the forces might be strong enough to randomly generate rogue waves.

Theories of instability mechanisms for the generation and growth of wind waves—although not on the causes of rogue waves—are provided by Phillips [77] and Miles.

Principal lunar semi-diurnal constituent. In most locations, the largest constituent is the "principal lunar semi-diurnal", also known as the M2 (or M 2) tidal initiativeblog.com period is about 12 hours and minutes, exactly half a tidal lunar day, which is the average time separating one lunar zenith from the next, and thus is the time required for the Earth to rotate once relative to the Moon. Ultrasonics: Ultrasonics, vibrations of frequencies greater than the upper limit of the audible range for humans—that is, greater than about 20 kilohertz. The term sonic is applied to ultrasound waves of very high amplitudes. Hypersound, sometimes called praetersound or microsound, is sound waves of frequencies. The treatment of social meaning in sociolinguistic variation has come in three waves of analytic practice. The first wave of variation studies established broad correlations between linguistic variables and the macrosociological categories of socioeconomic class, gender, ethnicity, and age.

So each wave in the wave group become smaller because cold water holds more wave energy based on density. The waves are now spaced farther apart and because of gravity they will propagate into more waves to fill up the space and become a stable wave group.

If a stable wave group exists in cold water and moves into a warm water column the waves will get larger and the wavelength will be shorter.

Three waves of variation study

The waves will seek equilibrium by attempting to displace the waves amplitude because of gravity. However, by starting with a stable wave group the wave energy can displace toward the center of the group. If both the front and back of the wave group are displacing energy toward the center it can become a rogue wave.

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This would happen only if the wave group is very large. In this case, focusing is primarily due to different waves coming into phase, rather than any energy transfer processes.

Further analysis of rogue waves using a fully nonlinear model by R. Gibbs brings this mode into question, as it is shown that a typical wavegroup focuses in such a way as to produce a significant wall of water, at the cost of a reduced height.

A rogue wave, and the deep trough commonly seen before and after it, may last only for some minutes before either breaking, or reducing in size again.

Three waves of variation study

Apart from one single rogue wave, the rogue wave may be part of a wave packet consisting of a few rogue waves. Such rogue wave groups have been observed in nature. Bahram Jalali and other researchers at UCLA studied microstructured optical fibers near the threshold of soliton supercontinuum generation and observed rogue wave phenomena.

After modelling the effect, the researchers announced that they had successfully characterized the proper initial conditions for generating rogue waves in any medium.This second post, based on analysis of the British Election Study (BES) , looks at selected attitudes of religious groups in initiativeblog.com waves of panel data (conducted in, respectively, February-March and April-June ) have so far been made available from the BES for wider analysis.

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Radio technology: Radio technology, transmission and detection of communication signals consisting of electromagnetic waves that travel through the air in a straight line or by reflection from the ionosphere or from a communications satellite.

Learn more about the history, development, and principles of radio technology in this article. The treatment of social meaning in sociolinguistic variation has come in three waves of analytic practice.

The first wave of variation studies established broad correlations between linguistic variables and the macrosociological categories of socioeconomic class, gender, ethnicity, and age.

Rogue waves (also known as freak waves, monster waves, episodic waves, killer waves, extreme waves, and abnormal waves) are large, unexpected and suddenly appearing surface waves that can be extremely dangerous, even to large ships such as ocean liners..

Rogue waves present considerable danger for several reasons: they are rare, unpredictable, may appear suddenly or without warning, . The treatment of social meaning in sociolinguistic variation has come in three waves of analytic practice.

The first wave of variation studies established broad correlations between linguistic variables and the macrosociological categories of socioeconomic class, gender, ethnicity, and age.

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The British Election Study Religious affiliation and attitudes - British Religion in Numbers