An antibody ( Ab ), also known as an immunoglobulin ( Ig ), is a large Y-shaped protein produced by B-cells that is used by the immune system to identify and neutralize foreign objects such as bacteria and viruses.

" For example, 51 Peg Aa is the host star in the system 51 Peg ; and the first exoplanet is then 51 Peg Ab.

Benito states " With Enki it is an interesting change of gender symbolism, the fertilising agent is also water, Sumerian " a " or " Ab " which also means " semen ".

In the epic Enki and Ninhursag, Enki, as lord of Ab or fresh water ( also the Sumerian word for semen ), is living with his wife in the paradise of Dilmun where

Another example is the functor Rng → Ab which maps a ring to its underlying additive abelian group.

This is a functor which is contravariant in the first and covariant in the second argument, i. e. it is a functor Ab < sup > op </ sup > × Ab → Ab ( where Ab denotes the category of abelian groups with group homomorphisms ).

If f: A < sub > 1 </ sub > → A < sub > 2 </ sub > and g: B < sub > 1 </ sub > → B < sub > 2 </ sub > are morphisms in Ab, then the group homomorphism Hom ( f, g ): Hom ( A < sub > 2 </ sub >, B < sub > 1 </ sub >) → Hom ( A < sub > 1 </ sub >, B < sub > 2 </ sub >) is given by φ g o φ o f. See Hom functor.

If I is ordered ( not simply partially ordered ) and countable, and C is the category Ab of abelian groups, the Mittag-Leffler condition is a condition on the transition morphisms f < sub > ij </ sub > that ensures the exactness of.

is an exact sequence in Ab.

* A category is preadditive if it is enriched over the monoidal category Ab of abelian groups.

A preadditive category is also called an Ab-category, after the notation Ab for the category of abelian groups.

The most obvious example of a preadditive category is the category Ab itself.

If C and D are preadditive categories, then a functor F: C → D is additive if it too is enriched over the category Ab.

The latter example leads to a generalization of modules over rings: If C is a preadditive category, then Mod ( C ) := Add ( C, Ab ) is called the module category over C. When C is the one-object preadditive category corresponding to the ring R, this reduces to the ordinary category of ( left ) R-modules.

This is because the biproduct in well known preadditive categories like Ab is the direct sum.

Indeed, the term " zero object " originated in the study of preadditive categories like Ab, where the zero object is the zero group.

The preadditive categories most commonly studied are in fact Abelian categories ; for example, Ab is an Abelian category.

* Any ring R can be considered as a one-object preadditive category ; the category of left modules over R is the same as the additive functor category Add ( R, Ab ) ( where Ab denotes the category of abelian groups ), and the category of right R-modules is Add ( R < sup > op </ sup >, Ab ).

Because of this example, for any preadditive category C, the category Add ( C, Ab ) is sometimes called the " category of left modules over C " and Add ( C < sup > op </ sup >, Ab ) is the category of right modules over C.

The same can be carried out for any preadditive category C: Yoneda then yields a full embedding of C into the functor category Add ( C < sup > op </ sup >, Ab ).

The F1 offspring AaBb produces gametes that are AB, Ab, aB, and ab with equal frequencies ( 25 %) because the alleles of gene A assort independently of the alleles for gene B during meiosis.

Particular mention is made of the crown placed on Joash's head (), because it fitted exactly, showing that he was qualified for kingship ( Ab.

More precisely, Ab is a closed monoidal category.

Consider the category Ab of abelian groups and group homomorphisms.

The motivating prototype example of an abelian category is the category of abelian groups, Ab.

The category Ab, consisting of all abelian groups and their group homomorphisms, is a full subcategory of Grp, and the prototype of an abelian category.

* The formation of endomorphism rings can be viewed as a functor from the category of abelian groups ( Ab ) to the category of rings.

* Ab initio phasing or direct methods – This is usually the method of choice for small molecules (< 1000 non-hydrogen atoms ), and has been used successfully to solve the phase problems for small proteins.

* The inclusion functor Ab → Grp creates limits but does not preserve coproducts ( the coproduct of two abelian groups being the direct sum ).

However, although infinite direct sums make sense in some categories, like Ab, infinite biproducts do not make sense.

The masses of both A and B's companions ( Ab and Bb ) ( deduced by the sum total mass of the system minus the likely masses of Aa and Ba determined by their class ) indicate that they are probably MV stars ( red dwarfs ), Bb being on the cool end of the M spectrum, not much hotter than a brown dwarf.

* The inclusion functor Ab → Grp is fully faithful.

Ab initio methods are based entirely on theory from first principles.

Boniface changed the numbering of the years in the Julian Calendar from Ab Urbe Condita to Anno Domini.

Artist's impression of the sight from a ( hypothetical ) moon of planet HD 188753 Ab ( upper left ), which orbits a triple star system.

Ab Urbe condita is Latin for " from the founding of the City ( Rome )", traditionally set in 753 BC.

* Ab Urbe Condita, by Titus Livius ( around 59 BC-17 AD ), a monumental history of Rome, from its founding ( traditionally dated to 753 BC ).

This is a reference to the story of Verginia from Livy's Ab urbe condita ( c. 26 B. C .).

Roman Pompaelo was located in the province of Hispania Tarraconensis, on the Ab Asturica Burdigalam, the road from Burdigala ( modern Bordeaux ) to Asturica ( modern Astorga ); it was a civitas stipendiaria in the jurisdiction of the conventus of Caesaraugusta ( modern Zaragoza ).

Her story is told in the first book of Ab Urbe Condita of Livy and in fragments from Ennius, Annales and Fabius Pictor.

The phrase appears many hundreds of times in Roman political, legal and historical literature, including the speeches of Mārcus Tullius Cīcerō ( Tully ) and the Ab urbe condita libri (" Books from the Founding of the City ") of Titus Livius ( Livy ).

The account is from Livy's Ab urbe condita and deals with a point in the history of Rome prior to reliable historical records ( virtually all prior records were destroyed by the Gauls when they sacked Rome under Brennus in 390 BC or 387 BC ).

: Akiva, noticing a stone at a well that had been hollowed out by drippings from the buckets, said: " If these drippings can, by continuous action, penetrate this solid stone, how much more can the persistent word of God penetrate the pliant, fleshly human heart, if that word but be presented with patient insistency " ( Ab.

* Ab urbe condita, Latin for " from the founding of the city " ( of Rome ), used for calculation of dates.

The story of Terentilius comes to us from one source, Book III of Livy's Ab Urbe Condita.

The historical background and characters in the story are taken from Livy's Ab Urbe Condita ( written ca.

Weighting of the of resonance structures in terms of their contribution to the overall structure can be calculated in multiple ways, using " Ab initio " methods derived from Valence Bond theory, or else from the Natural Bond Orbitals ( NBO ) approaches of Weinhold NBO5, or finally from empirical calculations based on the Hückel method.

Ab initio-or de novo-protein modelling methods seek to build three-dimensional protein models " from scratch ", i. e., based on physical principles rather than ( directly ) on previously solved structures.

Although the Roman historian Livy ( 59 BC – AD 17 ) lists a series of seven kings of early Rome in his work Ab Urbe Condita, from its establishment through its earliest years, the degree to which the first four kings ( Romulus, Numa, Tullus Hostilius and Ancus Marcius ) are apocryphal is certainly open to question.

Some credit Hillel, and not his better-known namesake, with the authorship of the following maxims: " Separate not thyself from the community "; " Be not confident in thyself until the day of thy death "; " Condemn not thy neighbor until thou hast been placed in his condition "; " Use no unintelligible expressions assuming that ultimately they will be understood "; " Say not ' When I have leisure I shall study ': thou mayest never be at leisure " ( Ab.