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  2. List of space groups - Wikipedia

    en.wikipedia.org/wiki/List_of_space_groups

    The possible screw axes are: 2 1, 3 1, 3 2, 4 1, 4 2, 4 3, 6 1, 6 2, 6 3, 6 4, and 6 5. Wherever there is both a rotation or screw axis n and a mirror or glide plane m along the same crystallographic direction, they are represented as a fraction or n/m.

  3. List of nearby stellar associations and moving groups

    en.wikipedia.org/wiki/List_of_nearby_stellar...

    This is a list of nearby stellar associations and moving groups. A stellar association is a very loose star cluster, looser than an open cluster. A moving group is the remnant of such a stellar association. [1] Members of stellar associations and moving groups share similar kinematic properties, as well as similar ages and chemical composition.

  4. QRS complex - Wikipedia

    en.wikipedia.org/wiki/QRS_complex

    Diagram showing how the polarity of the QRS complex in leads I, II, and III can be used to estimate the heart's electrical axis in the frontal plane. The QRS complex is the combination of three of the graphical deflections seen on a typical electrocardiogram (ECG or EKG). It is usually the central and most visually obvious part of the tracing.

  5. QRS complexes - Wikipedia

    en.wikipedia.org/?title=QRS_complexes&redirect=no

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  6. Lorentz group - Wikipedia

    en.wikipedia.org/wiki/Lorentz_group

    The quotient on projective space leads to a quotient on the group SL(2, C). Finally, these two can be linked together by using the complex projective vector to construct a null-vector. If is a CP 1 projective vector, it can be tensored with its Hermitian conjugate to produce a Hermitian matrix. From elsewhere in this article we know this space ...

  7. Timeline of knowledge about galaxies, clusters of galaxies ...

    en.wikipedia.org/wiki/Timeline_of_knowledge...

    5th century BC – Democritus proposes that the bright band in the night sky known as the Milky Way might consist of stars. 4th century BC – Aristotle believes the Milky Way to be caused by "the ignition of the fiery exhalation of some stars which were large, numerous and close together" and that the "ignition takes place in the upper part of the atmosphere, in the region of the world which ...

  8. Representation theory of the Lorentz group - Wikipedia

    en.wikipedia.org/wiki/Representation_theory_of...

    Representation theory of groups in general, and Lie groups in particular, is a very rich subject. The Lorentz group has some properties that makes it "agreeable" and others that make it "not very agreeable" within the context of representation theory; the group is simple and thus semisimple , but is not connected , and none of its components ...

  9. ST segment - Wikipedia

    en.wikipedia.org/wiki/ST_segment

    In electrocardiography, the ST segment connects the QRS complex and the T wave and has a duration of 0.005 to 0.150 sec (5 to 150 ms). It starts at the J point (junction between the QRS complex and ST segment) and ends at the beginning of the T wave.