Quasigroup

In mathematics, especially in abstract algebra, a quasigroup is an algebraic structure resembling a group in the sense that "division" is always possible. Quasigroups differ from groups mainly in that they need not be associative.

A quasigroup with an identity element is called a loop.

Definitions

There are at least two equivalent formal definitions of quasigroup. One defines a quasigroup as a set with one binary operation, and the other, from universal algebra, defines a quasigroup as having three primitive operations. We begin with the first definition.

A quasigroup (Q, ∗) is a set, Q, with a binary operation, ∗, (that is, a magma), obeying the Latin square property. This states that, for each a and b in Q, there exist unique elements x and y in Q such that both

hold. (In other words: Each element of the set occurs exactly once in each row and exactly once in each column of the quasigroup's multiplication table, or Cayley table. This property ensures that the Cayley table of a finite quasigroup is a Latin square.)

Loop (knot)

In reference to knots, loop may refer to:

References

Turn (biochemistry)

A turn is an element of secondary structure in proteins where the polypeptide chain reverses its overall direction. For beta turns go to Beta turn.

Definition

According to one definition, a turn is a structural motif where the C^α atoms of two residues separated by few (usually 1 to 5) peptide bonds are close (< 7 Å), while the residues do not form a secondary structure element such as an alpha helix or beta sheet with regularly repeating backbone dihedral angles. Although the proximity of the terminal C^α atoms usually correlates with formation of a hydrogen bond between the corresponding residues, a hydrogen bond is not a requirement in this turn definition. That said, in many cases the H-bonding and C^α-distance definitions are equivalent.

Types of turns

Turns are classified according to the separation between the two end residues:

In an α-turn the end residues are separated by four peptide bonds ().

In a β-turn (the most common form), by three bonds ().

In a γ-turn, by two bonds ().

Zulu (song)

"Zulu" is a 1981 dance single by British duo The Quick. "Zulu" was their most successful of three singles the group placed on the dance chart. The single went to number one for two weeks in October 1981. "Zulu" also peaked at number sixty on the R&B singles chart.

References

Pillow Pal

Pillow Pals were a line of plush toys made by Ty, Inc. during the 1990s. The toys were given their name because they were soft like a pillow, and were made with children in mind. Though many of them resembled certain Beanie Babies, those that did not share names with their Beanie Baby counterparts. Such Pillow Pals saw a decline in popularity in the late 1990s with the introduction of Beanie Buddies, which were also larger versions of various Beanie Babies. In January 1999, all Pillow Pals were redesigned, and their colors were changed. This line did not sell well, and was discontinued by Ty around the end of the year. Today, PillowPals LLC takes children's drawings and replicates them into 3D pillows.

At the time of the final retirement, Ty donated its remaining stock of pillow pals to the Ronald McDonald House to be distributed to sick children.

List of Pillow Pals

The following Pillow Pals were made during the 1990s:

After the 1999 redesign, the following Pillow Pals were made:

Zulu (surname)

Zulu is the surname of: