On difunctionality of class relations

For a given variety V of algebras, we define a class relation to be a binary relation R subset of S(2)which is of the form R = S-2 boolean AND K for some congruence class K on A(2), where A is an algebra in V such that S subset of A. In this paper we study the following property of V : every reflexive class relation is an equivalence relation. In particular, we obtain equivalent characterizations of this property analogous to well-known equivalent characterizations of congruence-permutable varieties. This property determines a Mal'tsev condition on the variety and in a suitable sense, it is a join of Chajda's egg-box property as well as Duda's direct decomposability of congruence classes.South African National Research FoundationNational Research Foundation - South AfricaCentre for Mathematics of the University of Coimbra - Portuguese Government through FCT/MEC [UID/MAT/00324/2019]European Regional Development Fund through the Partnership Agreement PT2020info:eu-repo/semantics/publishedVersio

A novel approach in the treatment of neuroendocrine gastrointestinal tumors: Additive antiproliferative effects of interferon-γ and meta-iodobenzylguanidine

BACKGROUND: Therapeutic options to effectively inhibit growth and spread of neuroendocrine gastrointestinal tumors are still limited. As both meta-iodobenzylguanidine (MIBG) and interferon-γ (IFNγ) cause antineoplastic effects in neuroendocrine gastrointestinal tumor cells, we investigated the antiproliferative effects of the combination of IFNγ and non-radiolabeled MIBG in neuroendocrine gut STC-1 and pancreatic carcinoid BON tumor cells. METHODS AND RESULTS: IFNγ receptors were expressed in both models. IFNγ dose- and time-dependently inhibited the growth of both STC-1 and of BON tumor cells with IC(50)-values of 95 ± 15 U/ml and 135 ± 10 U/ml, respectively. Above 10 U/ml IFNγ induced apoptosis-specific caspase-3 activity in a time-dependent manner in either cell line and caused a dose-dependent arrest in the S-phase of the cell cycle. Furthermore, IFNγ induced cytotoxic effects in NE tumor cells. The NE tumor-targeted drug MIBG is selectively taken up via norepinephrine transporters, thereby specifically inhibiting growth in NE tumor cells. Intriguingly, IFNγ treatment induced an upregulation of norepinephrine transporter expression in neuroendocrine tumors cells, as determined by semi-quantitative RT-PCR. Co-application of sub-IC(50 )concentrations of IFNγ and MIBG led to additive growth inhibitory effects, which were mainly due to increased cytotoxicity and S-phase arrest of the cell cycle. CONCLUSION: Our data show that IFNγ exerts antiproliferative effects on neuroendocrine gastrointestinal tumor cells by inducing cell cycle arrest, apoptosis and cytotoxicity. The combination of IFNγ with the NE tumor-targeted agent MIBG leads to effective growth control at reduced doses of either drug. Thus, the administration of IFNγ alone and more so, in combination with MIBG, is a promising novel approach in the treatment of neuroendocrine gastrointestinal tumors

A comprehensive overview of radioguided surgery using gamma detection probe technology

The concept of radioguided surgery, which was first developed some 60 years ago, involves the use of a radiation detection probe system for the intraoperative detection of radionuclides. The use of gamma detection probe technology in radioguided surgery has tremendously expanded and has evolved into what is now considered an established discipline within the practice of surgery, revolutionizing the surgical management of many malignancies, including breast cancer, melanoma, and colorectal cancer, as well as the surgical management of parathyroid disease. The impact of radioguided surgery on the surgical management of cancer patients includes providing vital and real-time information to the surgeon regarding the location and extent of disease, as well as regarding the assessment of surgical resection margins. Additionally, it has allowed the surgeon to minimize the surgical invasiveness of many diagnostic and therapeutic procedures, while still maintaining maximum benefit to the cancer patient. In the current review, we have attempted to comprehensively evaluate the history, technical aspects, and clinical applications of radioguided surgery using gamma detection probe technology

Global variability in leaf respiration in relation to climate, plant functional types and leaf traits

• Leaf dark respiration (Rdark) is an important yet poorly quantified component of the global carbon cycle. Given this, we analyzed a new global database of Rdark and associated leaf traits. • Data for 899 species were compiled from 100 sites (from the Arctic to the tropics). Several woody and nonwoody plant functional types (PFTs) were represented. Mixed-effects models were used to disentangle sources of variation in Rdark. • Area-based Rdark at the prevailing average daily growth temperature (T) of each site increased only twofold from the Arctic to the tropics, despite a 20°C increase in growing T (8–28°C). By contrast, Rdark at a standard T (25°C, Rdark25) was threefold higher in the Arctic than in the tropics, and twofold higher at arid than at mesic sites. Species and PFTs at cold sites exhibited higher Rdark25 at a given photosynthetic capacity (Vcmax25) or leaf nitrogen concentration ([N]) than species at warmer sites. Rdark25 values at any given Vcmax25 or [N] were higher in herbs than in woody plants. • The results highlight variation in Rdark among species and across global gradients in T and aridity. In addition to their ecological significance, the results provide a framework for improving representation of Rdark in terrestrial biosphere models (TBMs) and associated land-surface components of Earth system models (ESMs)

A categorical approach to lattice-like structures

Thesis (PhD)--Stellenbosch University, 2018.ENGLISH ABSTRACT : This thesis is a first step in a categorical approach to lattice-like structures. Its central notion, that of a majority category, relates to the category of lattices, in a similar way as Mal’tsev categories relate to the category of groups. This notion provides a context in which to establish categorical counterparts of various lattice-theoretic results. Surprisingly, many categories of a geometric nature naturally possess the dual property; namely, they are comajority categories. We show that several characterizations of varieties admitting a majority term, extend to characterizations of regular majority categories. These characterizations then show how majority categories relate to other well known notions in the literature, such as arithmetical and protoarithmetical categories. The most interesting results, from the point of view of the author, are those that concern decomposition and factorization. For example, every subobject of a finite product of objects in a regular majority category is uniquely determined by its two-fold projections – which can be seen as a certain subobject decomposition property. One of the main points of the thesis proves that in a regular majority category, every product of directly-irreducible objects is unique.AFRIKAANSE OPSOMMING : Hierdie proefskrif is ’n eerste stap na ’n kategoriese benadering tot roostersoos strukture. Die sentrale begrip daarvan, dié van ’n meerderheidskategorie, het betrekking op die kategorie van roosters, op soortgelyke wyse soos Mal’tsev-kategorieë betrekking het op die kategorie van groepe. Hierdie idee bied ’n konteks waarin kategoriese eweknieë van verskillende roosterteoretiese resultate gevestig kan word. Baie kategorieë van ’n meetkundige aard het die dubbele eienskap; naamlik, hulle is (co)meerderheids kategorieë. Ons wys dat verskeie karakters van variëteite wat ’n meerderheidstermyn toelaat, uitbrei na karakterisering van gereelde meerderheidskategorieë. Hierdie karakterisering toon dan aan hoe meerderheidskategorieë verband hou met ander bekende begrippe in die literatuur, soos Arithmetical en protoarithmetical kategorieë. Die mees interessante resultate, uit die oogpunt van die skrywer, is dié wat ontbinding en faktorisering betref. Ons wys dat direkte produkte erken ’n sekere unieke faktorisering stelling soortgelyk aan die universele algebraïese teendeel

The matrix taxonomy of finitely complete categories

This paper is concerned with the taxonomy of finitely complete categories, based on 'matrix properties' - these are a particular type of exactness properties that can be represented by integer matrices. In particular, the main result of the paper gives an algorithm for deciding whether a conjunction of such properties implies another such property. Computer implementation of this algorithm allows one to peer into the complex structure of the poset of `matrix classes', i.e., the poset of all collections of finitely complete categories determined by matrix properties. Among elements of this poset are the collections of Mal'tsev categories, majority categories, (finitely complete) arithmetical categories, as well as finitely complete extensions of various classes of varieties defined by a special type of Mal'tsev conditions found in the literature.Comment: 54 pages, 8 figure