Scattering in three-dimensional fuzzy space

We develop scattering theory in a non-commutative space defined by a $su(2)$ coordinate algebra. By introducing a positive operator valued measure as a replacement for strong position measurements, we are able to derive explicit expressions for the probability current, differential and total cross-sections. We show that at low incident energies the kinematics of these expressions is identical to that of commutative scattering theory. The consequences of spacial non-commutativity are found to be more pronounced at the dynamical level where, even at low incident energies, the phase shifts of the partial waves can deviate strongly from commutative results. This is demonstrated for scattering from a spherical well. The impact of non-commutativity on the well's spectrum and on the properties of its bound and scattering states are considered in detail. It is found that for sufficiently large well-depths the potential effectively becomes repulsive and that the cross-section tends towards that of hard sphere scattering. This can occur even at low incident energies when the particle's wave-length inside the well becomes comparable to the non-commutative length-scale.Comment: 12 pages, 6 figure

Spectrum of the three dimensional fuzzy well

We develop the formalism of quantum mechanics on three dimensional fuzzy space and solve the Schr\"odinger equation for a free particle, finite and infinite fuzzy wells. We show that all results reduce to the appropriate commutative limits. A high energy cut-off is found for the free particle spectrum, which also results in the modification of the high energy dispersion relation. An ultra-violet/infra-red duality is manifest in the free particle spectrum. The finite well also has an upper bound on the possible energy eigenvalues. The phase shifts due to scattering around the finite fuzzy potential well have been calculated

Species of Cercospora associated with grey leaf spot of maize

Grey leaf spot is a serious yield-reducing disease of maize (Zea mays) in many parts of the world where this crop is cultivated. The causal organism associated with the disease is Cercospora zeae-maydis. Two potential sibling species have been recognized as Groups I and II. The DNA sequences for the internal transcribed spacers (ITS1 & ITS2), the 5.8S rRNA gene, elongation factor 1-α, histone H3, actin and calmodulin gene regions suggest that Groups I and II are two distinct species. Furthermore, Cercospora zeae-maydis (Group I) can be distinguished from C. zeina sp. nov. (Group II) by its faster growth rate on artificial media, the ability to produce cercosporin, longer conidiophores, and broadly fusiform conidia. A PCR-based test that distinguishes the two species was developed using species-specific primers designed from the histone H3 gene

Eucalyptus microfungi known from culture. 1. Cladoriella and Fulvoflamma genera nova, with notes on some other poorly known taxa

A study of microfungi associated with living Eucalyptus leaves and leaf litter revealed several novel and interesting taxa. Cladoriella eucalypti gen. et sp. nov. is described as a Cladosporium-like genus associated with litter collected in South Africa, while Fulvoflamma eucalypti gen. et. sp. nov. is newly described from leaf litter collected in Spain. Beta-conidia are newly reported for species of Pestalotiopsis, namely Pestalotiopsis disseminata in New Zealand, and a Pestalotiopsis sp. from Colombia. Satchmopsis brasiliensis is reported from litter in Colombia and Indonesia, while Torrendiella eucalypti is reported from leaf litter in Indonesia, and shown to have a Sporothrix-like anamorph. Leptospora rubella is reported from living Eucalyptus leaves in Colombia, where it is associated with leaf spots of Mycosphaerella longibasalis, while Macrohilum eucalypti is reported from leaf spots of Eucalyptus in New Zealand

Comparison of the updated South African road safety assessment methods (sarsam 2022) with the South African road safety manual (sarsam 2012)

Papers presented virtually at the 41st International Southern African Transport Conference on 10-13 July 2023.The South African Road Safety Assessment Methods of 2022 (SARSAM 2022) replaced the previous South African Road Safety Audit Manual of 2012 (SARSAM, 2012). The SARSAM 2022 is part of the Technical Recommendations for Highways compiled under auspices of the Committee of Transport Officials (COTO), TRH 29. The Safe System Approach incorporates the principle that humans are frail and that the human body cannot withstand the kinetic energy that is transferred if a collision occurs without being killed or seriously injured. As such it is the responsibility of the road designer (authority) to design a road and road environment that is inherently safe. SARSAM 2012 was updated to incorporate the Safe System principles. The updated document now consists of three volumes which deals with Road Network Screening, Road Safety Inspections and Road Safety Audits. The accreditation of auditors by Engineering Council of South Africa (ECSA) has progressed and has now been incorporated in the updated methods. This paper highlights the substantial changes that occurred with the updated documen

Re-evaluating the taxonomic status of Phaeoisariopsis griseola, the causal agent of angular leaf spot of bean

Angular leaf spot of Phaseolus vulgaris is a serious disease caused by Phaeoisariopsis griseola, in which two major gene pools occur, namely Andean and Middle-American. Sequence analysis of the SSU region of nrDNA revealed the genus Phaeoisariopsis to be indistinguishable from other hyphomycete anamorph genera associated with Mycosphaerella, namely Pseudocercospora and Stigmina. A new combination is therefore proposed in the genus Pseudocercospora, a name to be conserved over Phaeoisariopsis and Stigmina. Further comparisons by means of morphology, cultural characteristics, and DNA sequence analysis of the ITS, calmodulin, and actin gene regions delineated two groups within P. griseola, which are recognised as two formae, namely f. griseola and f. mesoamericana

Cylindrocarpon root rot: multi-gene analysis reveals novel species within the Ilyonectria radicicola species complex

Abstract Ilyonectria radicicola and its Cylindrocarpon-like anamorph represent a species complex that is commonly associated with root rot disease symptoms on a range of hosts. During the course of this study, several species could be distinguished from I. radicicola sensu stricto based on morphological and culture characteristics. DNA sequence analysis of the partial β-tubulin, histone H3, translation elongation factor 1-α and nuclear ribosomal RNA-Internal Transcribed Spacer (nrRNA-ITS) genes were employed to provide further support for the morphological species resolved among 68 isolates associated with root rot disease symptoms. Of the various loci screened, nrRNA-ITS sequences were the least informative, while histone H3 sequences were the most informative, resolving the same number of species as the combined dataset across the four genes. Within the Ilyonectria radicicola species complex, 12 new taxa are delineated occurring on a diverse range of hosts, the most common being Cyclamen, Lilium, Panax, Pseudotsuga, Quercus and Vitis

Relativistic mean field formulation of clustering in heavy nuclei

Very little is known about clustering in heavy nuclei and in particular the interaction between the correlated cluster nucleons and remaining core nucleons. Currently the phenomenological Saxon-Woods plus cubic Saxon-Woods core-cluster potential successfully predicts the alpha decay half-life and energy band spectra of a number of heavy nuclei. This model, however, lacks a microscopic understanding of clustering phenomenon in these heavy nuclear systems. A fully relativistic microscopic formalism is presented, which generates the core-cluster potential by means of the McNeil, Ray and Wallace based double folding procedure. The core and cluster baryon densities are calculated by using a relativistic mean field approach. The Lorentz covariant IA1 representation of the nucleon-nucleon interaction is folded with the core and cluster densities. Theoretical predictions of the ground-state decay half-life and positive parity energy band of 212Po are obtained with the relativistic mean field formalism and which are compared to the results from the phenomenological Saxon-Woods plus cubic Saxon-Wood core-cluster potential and microscopic M3Y interaction

What is Johansonia?

The bitunicate ascomycete genus Johansonia is presently treated as a member of Saccardiaceae, a family regarded as incertae sedis within the Ascomycota. Recent collections on leaves of a leguminous host, Dimorphandra mollis, in Mato Grosso, Brazil, led to the discovery of a new species of Johansonia, described here as J. chapadiensis. Based on DNA sequence data of the nuclear ribosomal DNA (LSU), Johansonia is revealed to represent a member of Dothideomycetes, Capnodiales. Although its family could not be resolved, it clustered basal to Schizothyriaceae and Mycosphaerellaceae, and could well represent a species of Saccardiaceae. DNA sequence data of other members of Saccardiaceae would be required, however, to confirm this classification