200 research outputs found
3-Point Functions in N=4 Yang-Mills
Three-point functions of analytic (chiral primary) operators in N=4
Yang-Mills theory in four dimensions are calculated using the harmonic
superspace formulation of this theory. In the case of the energy-momentum
tensor multiplet anomaly considerations determine the coefficient. Analyticity
in N=2 harmonic superspace is explicitly checked in a two-loop calculation.Comment: This file requires the feynman.tex macro Some references are adde
Moisture source and diet affect development and reproduction of Orius thripoborus and Orius naivashae, two predatory anthocorids from southern Africa
The effect of moisture source and diet on the development and reproduction of the pirate bugs, Orius thripoborus (Hesse) and Orius naivashae (Poppius) (Hemiptera: Anthocoridae) was examined in the laboratory. Both species had been collected in and around sugarcane fields in South Africa. Supplementing eggs of the flour moth Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) with a green bean pod as a moisture source yielded better nymphal survival and faster development, as compared with free water encapsulated in Parafilm, suggesting that the predators may extract extra nutrients from the bean pod. The impact of two factitious foods and moist honey bee pollen on developmental and reproductive parameters of both predators was also investigated. The overall performance of both Orius species on E. kuehniella eggs and cysts of brine shrimp, Artemia franciscana Kellogg (Crustacea: Artemiidae) was better than on pollen. Nonetheless, a pollen diet alone allowed 66 and 78% of the nymphs of O. thripoborus and O. naivashae, respectively, to reach adulthood. Overall, developmental and reproductive performance of O. thripoborus on the tested diets was superior to that of O. naivashae. The implications of these findings for the mass production of these predators and their potential role in biological control programs in southern Africa are discussed
Non-Perturbative Green's Functions in Theories with Extended Superconformal Symmetry
The multiplets that occur in four dimensional rigidly supersymmetric theories
can be described either by chiral superfields in Minkowski superspace or
analytic superfields in harmonic superspace. The superconformal Ward identities
for Green's functions of gauge invariant operators of these types are derived.
It is shown that there are no chiral superconformal invariants. It is further
shown that the Green's functions of analytic operators are severely restricted
by the superconformal Ward when analyticity is taken into account.Comment: 17 pages, plain tex. Some conjectures that were in the original paper
are clarifed in the light of more recent work to which we give references.
See Note added for detail
Host-parasitoid interactions of Eldana Saccharina (Lepidoptera: Pyralidae) in Cyperus Papyrus.
Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1994.Since becoming a pest in graminaceous crops in Africa, the African sugarcane
stalkborer Eldana saccharina Walker has been the subject of much study. Its
very cryptic habits have precluded more commonly available control measures
being used against it. Biological control is regarded as a viable control option,
but the apparent paucity of parasitoids in graminaceous crops leads to E.
saccharina being regarded as lacking parasitoids, and thus not a good candidate
for biological control in the classical sense. In contrast, this project argues that
interactions in indigenous hosts of E. saccharina had been ignored, and that
classical biocontrol principles and basic ecological theory could be applied by the
discovery, collection and introduction of parasitoids from its indigenous habitat
to its newly adapted habitat, sugarcane.
The habitat offered by Cyperus papyrus L. was shown to be heterogenous both
temporarily and spatially. Umbels, from young through mature to senescent,
were available in the same proportion for colonisation throughout the year.
Umbels with sexual reproductive stages (seeds) were present from early spring
into late summer, and provided an additional component to the already
heterogenous environment. Young umbels, in addition, developed from rhizomes
in an environment regarded as sub-optimal for photosynthesis, until they reached
the canopy.
All stages of umbels were attacked by E. saccharina, but larvae were only found
in rays of umbels and in the apex of the culm, which was the meristematic area
for rays, both high nutrient areas. Young umbels were never found with borer
pupae, only smaller larvae, indicating that E. saccharina development matched
growth of young umbels until they reached canopy height. Also, the majority of
borings found were occupied, indicating that infestation of young umbels was
recent. All stages of E. saccharina development were found in mature umbels,
which were also most abundant at anyone time. Numerous empty borings were
found in addition to those occupied, indicative of past occupation by E. saccharina. Very few young larvae were found in old umbels, the majority of life
stages found being pupae or empty pupal cases, and also many empty borings,
showing that old umbels were not suitable for E. saccharina development.
A guild of parasitoids which comprised Orgilus bifasciatus Turner, the most
common parasitoid of small and smaller medium E. saccharina larvae, Goniozus
indicus Ashmead the most common parasitoid of larger medium and large larvae,
and an entomogenous fungus Seauveria bassiana (Sals.) Vuill. attacking all life
stages of E. saccharina was found. Three uncommon parasitoids of smaller
saccharina were also found, viz. Sassus sublevis (Granger), Iphiaulax sp. and
Venturia sp. The former three natural enemies were instrumental in depressing
a major outbreak within two months of it being observed and then maintaining
the host population at a lower level in C. papyrus. G. indicus and B. bassiana
were most effective during the summer and autumn months, and O. bifasciatus
most effective during the winter months.
This study supports the hypotheses that the apparent paucity of parasitoids and
lack of biological control success thus far against E. saccharina in sugarcane has
been because very little was known about its ecology and biology in its
numerous indigenous host plants, and that studies of the latter factors coupled
with ecological theory could enhance biological control programmes against this
borer. As more indigenous host plants are investigated in the same way as has
been done with C. papyrus, more will become known of natural enemies of E.
saccharina. Parasitoid guilds could be selected, even from rare parasitoids in the
more stable indigenous habitats, which would provide control in the unstable
habitat of sugarcane
Population dynamics of Eldana saccharina Walker (Lepidoptera: Pyralidae): application of a biophysical model to understand phenological variation in an agricultural pest.
Understanding pest population dynamics and seasonal phenology is a critical component of modern integrated pest-management programs. Accurate forecasting allows timely, cost-effective interventions, including maximum efficacy of, for example, biological
control and/or sterile insect technique. Due to the variation in life stage-related sensitivity toward climate, insect pest population abundance models are often not easily interpreted or lack direct relevance to management strategies in the field. Here we apply
a process-based (biophysical) model that incorporates climate data with life stage-dependent physiology and life history to attempt to predict Eldana saccharina life stage and generation turnover in sugarcane fields. Fitness traits are modelled at two agricultural locations in South Africa that differ in average temperature (hereafter a cold and a warm site).We test whether the life stage population structures in the field entering winter and local climate during winter directly affect development rates, and therefore
interact to determine the population dynamics and phenological responses of E. saccharina in subsequent spring and summer seasons. The model predicts that: (1) E. saccharina can cycle through more generations at the warm site where fewer hours of cold and heat
stress are endured, and (2) at the cold site, overwintering as pupae (rather than larvae) confer higher relative fitness and fecundity in the subsequent summer adult moths. The model predictions were compared with a large dataset of field observations from scouting
records. Model predictions for larval presence (or absence) generally overlapped well with positive (or negative) scout records. These results are important for integrated pest management strategies by providing a useful foundation for future population dynamics models, and are applicable to a variety of agricultural landscapes, but especially the sugarcane industry of South Africa
Operator product expansions in four-dimensional superconformal field theories
The operator product expansion in four-dimensional superconformal field
theory is discussed. The OPE takes a particularly simple form for chiral
operators, in and , and for analytic operators, in and .
It is argued that the Green's functions of such operators can be determined up
to constants.Comment: 9 pages, late
N=1 Superconformal Symmetry in Four Dimensional Quantum Field Theory
The implications of N=1 superconformal symmetry for four dimensional quantum
field theories are studied. Superconformal covariant expressions for two and
three point functions of quasi-primary superfields of arbitrary spin are found
and connected with the operator product expansion. The general formulae are
specialised to cases involving a scalar superfield L, which contains global
symmetry currents, and the supercurrent, which contains the energy momentum
tensor, and the consequences of superconformal Ward identities analysed. The
three point function of L is shown to have unique completely antisymmetric or
symmetric forms. In the latter case the superspace version of the axial anomaly
equation is obtained. The three point function for the supercurrent is shown to
have two linearly independent forms. A linear combination of the associated
coefficients for the general expression is shown to be related to the scale of
the supercurrent two point function through Ward identities. The coefficients
are given for the two free field superconformal theories and are also connected
with the parameters present in the supercurrent anomaly for supergravity
backgrounds. Superconformal invariants, which are possible even in three point
functions, are discussed.Comment: 53 pages, uses harvmac, revised version includes further corrections
and minor additions, version to be publishe
Exploring the role of sugarcane in small-scale farmers’ livelihoods in the Noodsberg Area, Kwazulu-Natal, South Africa
Participatory, mixed-methods research was conducted to study the role of sugarcane in small-scale sugarcane farmers’ livelihoods in the Noodsberg area, KwaZulu-Natal. Thirty-five farmers were visited at their homes and data was collected through semi-structured interviews, participatory sketch mapping, matrix scoring activities and informal field-based discussions. Results indicated that sugarcane was a key livelihood resource providing employment and income, and it generated more income than any other single agricultural enterprise. It was considered the most important crop in most households, even though it was grown within a diverse agricultural system including maize, beans, taro (amadumbe) and potatoes. Considering the important role of sugarcane as a cash crop in farmers’ livelihoods, further development of land to sugarcane in the Noodsberg area will continue to reduce poverty and improve the livelihoods of farmers.Keywords: farming systems, food security, poverty, rural development, small-scale growers, sugarcane
Acridid ecology in the sugarcane agro-ecosystem in the Zululand region of KwaZulu-Natal, South Africa
CITATION: Bam, A., Addison, P. & Conlong, D. 2020. Acridid ecology in the sugarcane agro-ecosystem in the Zululand region of KwaZulu-Natal, South Africa. Journal of Orthoptera Research, 29(1):9–16, doi:10.3897/jor.29.34626.The original publication is available at https://jor.pensoft.netGrasshoppers and locusts are well known crop and pasture pests throughout the world. Periodically they cause extensive damage to large areas of crops and grazing lands, which often exacerbate food shortage issues in many countries. In South Africa, acridid outbreaks rarely reach economic proportions, but in sugarcane plantations, localized outbreaks of native acridid species have been reported for the last eight years with increasing frequency and intensity in certain areas. This study was undertaken from May 2012 to May 2013 to identify the economically important acridid species in the sugarcane agroecosystem in these outbreak areas, to monitor seasonal activity patterns, to assess sampling methods, and to determine the pest status of the major species through damage ratings. Five acridid species of particular importance were identified: Nomadacris septemfasciata (Serville), Petamella prosternalis (Karny), Ornithacris cyanea (Stoll), Cataloipus zuluensis Sjötedt, and Cyrtacanthacris aeruginosa (Stoll). All species are univoltine. Petamella prosternalis was the most abundant species and exhibited a winter egg diapause, while N. septemfasciata, the second most abundant species, exhibited a winter reproductive diapause. Petamella prosternalis and N. septemfasciata were significantly correlated with the damage-rating index, suggesting that these two species were responsible for most of the feeding damage found on sugarcane. This study, for the first time, identified the acridid species complex causing damage to sugarcane in the Zululand area of KwaZulu-Natal, South Africa, and documented their population characteristics and related damage. These data are important information on which to base sound integrated pest management strategies.SASRINational Research Foundation of South Africahttps://jor.pensoft.net/article/34626/element/8/64680//Publisher's versio
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