University of the Free State

About: University of the Free State is a education organization based out in Bloemfontein, South Africa. It is known for research contribution in the topics: Population & Photoluminescence. The organization has 8429 authors who have published 16531 publications receiving 240919 citations. The organization is also known as: UFS.

Rickettsia aeschlimannii: A new pathogenic spotted fever group rickettsia, South Africa.

Abstract: To the Editor: Spotted fever group rickettsiae are increasingly recognized as agents of disease in residents of and tourists to South Africa (1). To date, two species, Rickettsia conorii and R. africae, which cause Mediterranean spotted fever (MSF) and African tick-bite fever (ATBF), respectively, have been associated with human disease in the region; ATBF is more frequently associated with travel (1). As different antibiotic regimens are recommended for the two syndromes, differentiating MSF from ATBF is important. Increasing evidence shows that the syndromes can usually be differentiated through clinical manifestations and epidemiologic characteristics (1). We recently encountered a South African patient who, on returning from a hunting and fishing trip, discovered a Rhipicephalus appendiculatus tick attached to his right thigh and an eschar around the attachment site. The patient was aware of the risk of tick-transmitted disease; after removing the tick, immediately self-prescribed doxycycline. No further symptoms developed. However, as a precaution, the patient went to a local clinic, where a skin biopsy was taken from the eschar. This sample, together with the removed tick, was submitted to our laboratory. DNA extracts, prepared from an eschar biopsy and the tick, were incorporated into a polymerase chain reaction (PCR) assay specifically targeting a fragment of the rickettsial ompA (2). Sequence analysis of the amplification products showed both to be identical and to share >99% similarity with the ompA of R. aeschlimannii, a species not previously associated with human disease. Unfortunately, blood samples could not be collected at the time the patients first had symptoms; thus, investigation of a disseminated infection by PCR and serologic testing was not possible. Although genotypically indistinguishable organisms had previously been detected in Hyalomma marginatum collected in Portugal and Zimbabwe, R. aeschlimannii was first characterized following its isolation from H. marginatum ticks in Morocco (3) and recently in Niger (4). This encounter was the first demonstration of its presence in South Africa and in Rhipicephalus ticks. A lack of suitable clinical material prevented full evaluation of the pathogenic potential of R. aeschlimannii in this patient and prompt antibiotic intervention may have prevented evolution of the syndrome. Nonetheless, that R. aeschlimannii was transmitted to the patient and established a local infection leading to eschar formation provides clear, albeit preliminary, evidence of its virulence. Until further cases are encountered, allowing better characterization of the clinical manifestations associated with R. aeschlimannii infection and considering the agent capable of inducing either MSF or ATBF-like manifestations is crucial; neither of these syndromes can be associated with a specific causative agent without microbiologic identification. Our findings demonstrate that Rickettsia species first encountered in tick surveys are associated with human disease, and we should not assume that some Rickettsia species not have a pathogenic potential.

Leaf rust and stripe rust resistance genes transferred to common wheat from Triticum dicoccoides

Abstract: Linked leaf rust and stripe rust resistance genes introduced from Triticum dicoccoides protected common wheat seedlings against a range of pathotypes of the respective pathogens. The genes were chromosomally mapped using monosomic and telosomic analyses, C-banding and RFLPs. The data indicated that an introgressed region is located on wheat chromosome arm 6BS. The introgressed region did not pair with the ‘Chinese Spring’ 6BS arm during meiosis possibly as a result of reduced homology, but appeared to pair with 6BS of W84-17 (57% of pollen mother cells) and ‘Avocet S’. The introgressed region had a very strong preferential pollen transmission (0.96–0.98) whereas its transmission through egg cells (0.41–0.66) varied with the genetic background of the heterozygote. Homozygous resistant plants had a normal phenotype, were fertile and produced plump seeds. Symbols Lr53 and Yr35 are proposed to designate the respective genes.

A comparative study of convective fluid motion in rotating cavity via Atangana–Baleanu and Caputo–Fabrizio fractal–fractional differentiations

Abstract: In this paper, a fractal–fractional mathematical model of convective fluid motion in rotating cavity is investigated inside the ellipsoid with inhomogeneous external heating. The fractal–fractional differential operators namely Caputo, Caputo–Fabrizio and Atangana–Baleanu $${\mathcal{D}}_{\tau }^{{\epsilon }_{1},{\tau }_{1}}$$, $${\mathcal{D}}_{\tau }^{{\epsilon }_{2},{\tau }_{2}}$$ and $${\mathcal{D}}_{\tau }^{{\epsilon }_{3},{\tau }_{3}}$$, respectively, are used in the non-linear mathematical model of convective fluid motion in rotating cavity. The numerical algorithms have been generated in terms of newly presented fractal–fractional differential operators on the basis of Adams–Bashforth method to compute the approximate solutions explicitly. The equilibrium points and stability analysis of the fractal–fractional Atangana–Baleanu, Caputo–Fabrizio and Caputo differential operators in Caputo sense have been investigated for non-linear mathematical model of convective fluid motion in rotating cavity. The numerical solutions are simulated in three types of variations (i) presence of fractional parameter without fractal parameter, (ii) presence of fractal parameter without fractional parameter, and (iii) presence of fractal parameter as well as fractional parameter. The chaotic behavior of convective fluid motion in rotating cavity based on each fractal–fractional differential operator has been highlighted as (a) projection on the x–y plane, (b) projection on the x–z plane, (c) projection on the y–z plane and (d) projection on the $$xyz$$ plane in three dimensions.