1,745 research outputs found
Semisimple Varieties of Implication Zroupoids
It is a well known fact that Boolean algebras can be defined using only
implication and a constant. In 2012, this result was extended to De Morgan
algebras in [8] which led Sankappanavar to introduce, and investigate, the
variety I of implication zroupoids generalizing De Morgan algebras. His
investigations were continued in [3] and [4] in which several new subvarieties
of I were introduced and their relationships with each other and with the
varieties of [8] were explored. The present paper is a continuation of [8] and
[3]. The main purpose of this paper is to determine the simple algebras in I.
It is shown that there are exactly five simple algebras in I. From this
description we deduce that the semisimple subvarieties of I are precisely the
subvarieties of the variety generated by these 5 simple I-zroupoids and are
locally finite. It also follows that the lattice of semisimple subvarieties of
I is isomorphic to the direct product of a 4-element Boolean lattice and a
4-element chain.Comment: 21 page
Order in Implication Zroupoids
The variety of implication zroupoids was defined and
investigated by Sankappanavar ([7]) as a generalization of De Morgan algebras.
Also, in [7], several new subvarieties of were introduced,
including the subvariety , defined by the identity: , which plays a crucial role in this paper. Several more new
subvarieties of , including the subvariety of
semilattices with a least element , are studied in [3], and an explicit
description of semisimple subvarieties of is given in [5].
It is well known that the operation induces a partial order
() in the variety and also in the variety
of De Morgan algebras. As both and
are subvarieties of and the definition of partial order can be
expressed in terms of the implication and the constant, it is but natural to
ask whether the relation (now defined) on is
actually a partial order in some (larger) subvariety of that
includes and .
The purpose of the present paper is two-fold: Firstly, a complete answer is
given to the above mentioned problem. Indeed, our first main theorem shows that
the variety is a maximal subvariety of with
respect to the property that the relation is a partial order on
its members. In view of this result, one is then naturally led to consider the
problem of determining the number of non-isomorphic algebras in
that can be defined on an -element chain (herein called
-chains), being a natural number. Secondly, we answer
this problem in our second main theorem, which says that, for each , there are exactly nonisomorphic -chains of
size .Comment: 35 page
On Implicator Groupoids
In a paper published in 2012, the second author extended the well-known fact
that Boolean algebras can be defined using only implication and a constant, to
De Morgan algebras-this result led him to introduce, and investigate (in the
same paper), the variety I of algebras, there called implication zroupoids
(I-zroupoids) and here called implicator gruopids (I- groupoids), that
generalize De Morgan algebras. The present paper is a continuation of the paper
mentioned above and is devoted to investigating the structure of the lattice of
subvarieties of I, and also to making further contributions to the theory of
implicator groupoids. Several new subvarieties of I are introduced and their
relationship with each other, and with the subvarieties of I which were already
investigated in the paper mentioned above, are explored.Comment: This paper, except the appendix, will appear in Algebra Universalis.
25 pages, 4 figures, a revised version with a new titl
Recommended from our members
Hopanoid lipids may facilitate aerobic nitrogen fixation in the ocean.
Cyanobacterial diazotrophs are considered to be the most important source of fixed N2 in the open ocean. Biological N2 fixation is catalyzed by the extremely O2-sensitive nitrogenase enzyme. In cyanobacteria without specialized N2-fixing cells (heterocysts), mechanisms such as decoupling photosynthesis from N2 fixation in space or time are involved in protecting nitrogenase from the intracellular O2 evolved by photosynthesis. However, it is not known how cyanobacterial cells limit O2 diffusion across their membranes to protect nitrogenase in ambient O2-saturated surface ocean waters. Here, we explored all known genomes of the major marine cyanobacterial lineages for the presence of hopanoid synthesis genes, since hopanoids are a class of lipids that might act as an O2 diffusion barrier. We found that, whereas all non-heterocyst-forming cyanobacterial diazotrophs had hopanoid synthesis genes, none of the marine Synechococcus, Prochlorococcus (non-N2-fixing), and marine heterocyst-forming (N2-fixing) cyanobacteria did. Finally, we conclude that hopanoid-enriched membranes are a conserved trait in non-heterocyst-forming cyanobacterial diazotrophs that might lower the permeability to extracellular O2 This membrane property coupled with high respiration rates to decrease intracellular O2 concentration may therefore explain how non-heterocyst-forming cyanobacterial diazotrophs can fix N2 in the fully oxic surface ocean
Evaluando los niveles tróficos de dos tiburones oceánicos del Océano PacÃfico suroriental
Indexación: Web of ScienceStable isotope analyses for shortfin mako (Isurus oxyrinchus) and blue sharks (Prionace glauca) were conducted to assess their trophic position in two periods of time (before 1980 and after 2000) in the Southeastern Pacific waters (SEP). Both sharks showed that their trophic position decreased over time (P < 0.05). Many factors could be involved in this change such as dietary shifts, prey availability, or indirect fishing effects in SEP waters.RESUMEN. Para evaluar los niveles tróficos de los tiburones marrajo (Isurus oxyrinchus) y azulejo (Prionace glauca) en dos perÃodos de tiempo (previo a 1980 y posterior al 2000) en aguas del PacÃfico suroriental (SEP), se realizaron análisis de isótopos estables. Ambos tiburones mostraron un descenso del nivel trófico en el tiempo (P < 0,05). Varios son los factores que pueden estar involucrados en este evento, como los cambios dietarios, la disponibilidad de las presas o los efectos indirectos de la pesquerÃa en aguas del PacÃfico suroriental.http://www.lajar.cl/pdf/imar/v44n2/Art%C3%ADculo_44_2_25.pd
Extending the applicability of an open-ring trap to perform experiments with a single laser-cooled ion
An open-ring ion trap, also referred to as transparent trap was initially
built up to perform - correlation experiments with radioactive
ions. This trap geometry is also well suited to perform experiments with
laser-cooled ions, serving for the development of a new type of Penning trap,
in the framework of the project TRAPSENSOR at the University of Granada. The
goal of this project is to use a single Ca ion as detector for
single-ion mass spectrometry. Within this project and without any modification
to the initial electrode configuration, it was possible to perform Doppler
cooling on Ca ions, starting from large clouds and reaching single
ion sensitivity. This new feature of the trap might be important also for other
experiments with ions produced at Radioactive Ion Beam (RIB) facilities. In
this publication, the trap and the laser system will be described, together
with their performance with respect to laser cooling applied to large ion
clouds down to a single ion.Comment: 9 pages, 13 figure
- …