Pesticide Use in South Africa: One of the Largest Importers of Pesticides in Africa

South Africa is a diverse country, with a diverse environment that is home to more than 49 000 000 people. Pesticide usage is very often necessary to maintain both agricultural productivity as well as human health. The climatic conditions range from semi-tropic to semi-arid regions. Although the majority of the country has summer rainfall, the south western coastal region is predominantly a winter rainfall area. These variations in climate allows for a wide variety of crops, from tropical fruit to maize and tree plantations. Each individual crop is susceptible to a unique host of pests that in-turn require a unique mixture of pesticides to ensure the best resulting turnover. Currently, South Africa has more than 500 registered pesticides (Pesticide Action Network (PAN), 2010) and is one of the four largest importers of pesticides in sub-Saharan Africa (Osbanjo et al., 2002). In 2006 the import of insecticides, fungicides and herbicides that were packaged for retail totalled $ 170 056 000 the main import partners being Australia, China, Germany and the United States of America (USA) (International Trade Centre, 2011). These pesticides are used in almost every facet of our everyday lives; ensuring the quantity and quality of food we eat to managing the number of rodents and insects in our homes. Although it is evident that there is a vast amount of pesticides present in the South African environment, there is very limited data on the production of pesticides. The last published data indicates that in 2002 around 10 000 kℓ of liquid insecticides was produced exclusively for crop protection of which 43% consisted of organophosphates. During the same year 2 800-tonnes of solid insecticides were produced (Statistics South Africa, 2003). Although the usefulness of pesticides cannot be denied, the negative environmental and human health effects cannot be ignored. In South Africa, a number of environmental and anthropogenic factors have to be considered before the impact of large-scale pesticide use can be assessed. South Africa is a water poor country, with water resources being utilised to their maximum capacity. As discussed by Dabrowski et al. (2009), the trade-off between the economic benefits of exporting agricultural products has to be measured against the loss of water, not only through crop irrigation but also through water quality degradation. The article highlighted this aspect through the calculation of virtual water volumes. These calculated volumes indicated that to ensure sufficient dilution of all agrochemicals, to an acceptable water quality level (used in a typical farming situation applying current-use pesticides), was greater than the amount of water needed for irrigation. The seriousness of these scenarios is highlighted in literature where a diverse array of agricultural chemicals has been measured during run-off events, by once-off sampling and by water monitoring during the growing seasons. Detectable levels of atrazine, terbuthylazine, simazine, acetochlor (Du Preez et al., 2005), DDT and its metabolites, endosulfan, hexachlorocyclohexane (HCH), heptachlor, aldrin, dieldrin, endrin, chlordane (Fatoki et al., 2003), azinophos-methyl, chloropyriphos (Schultz et al., 2001; Dabrowski et al., 2002) prothiofos (Schultz, 2001), malathion, zendoxsulfan (Thiere &  Schultz, 2004), cypermethrin and fenvalerate (Bollmohr et al., 2007), to name a few, have all been measured in South African waters. Pesticides in the aquatic environment have the potential to affect all end-users, including both humans and wildlife. South Africa has the distinction of being one of the countries with the most species richness in the world. To date more than 900 bird species as well as over 200 mammals, call South Africa home. Of these mammals, seven species are endangered and 30 are vulnerable according to the 2004 IUCN red data list (IUCN, 2010). These endangered species include bats, moles, shrews and mice that are often insectivorous, thus increasing their risk of unintentional exposure to pesticides. Within avian populations, 11 species are listed as critically endangered and 43 species as vulnerable. The sensitivity of avian species to pollutants has been widely reported. With this unique diversity of species, South Africans have a responsibility towards maintaining the viability of ecosystems and natural habitats to ensure the continued existence of these creatures. This objective is not only morally relevant but also economically relevant especially in a country where tourism creates over 400 000 jobs and contributes approximately 8% to the GDP. Few studies have reported the levels of insecticides in wildlife species. However, pesticides have been detected in wild bird species (Van Wyk et al., 2001; Bouwman et al., 2008), as well as in indigenous fish species (Barnhoorn et al., 2009), indicating pesticide contamination within various habitats. This is of particular concern due to the health risks associated with many pesticides

Energy, interaction, and photoluminescence of spin-reversed quasielectrons in fractional quantum Hall systems

The energy and photoluminescence spectra of a two-dimensional electron gas in the fractional quantum Hall regime are studied. The single-particle properties of reversed-spin quasielectrons (QE$_{\rm R}$'s) as well as the pseudopotentials of their interaction with one another and with Laughlin quasielectrons (QE's) and quasiholes (QH's) are calculated. Based on the short-range character of the QE$_{\rm R}$--QE$_{\rm R}$ and QE$_{\rm R}$--QE repulsion, the partially unpolarized incompressible states at the filling factors $\nu={4\over11}$ and ${5\over13}$ are postulated within Haldane's hierarchy scheme. To describe photoluminescence, the family of bound $h($QE$_{\rm R})_n$ states of a valence hole $h$ and $n$ QE$_{\rm R}$'s are predicted in analogy to the found earlier fractionally charged excitons $h$QE$_n$. The binding energy and optical selection rules for both families are compared. The $h$QE$_{\rm R}$ is found radiative in contrast to the dark $h$QE, and the $h($QE$_{\rm R})_2$ is found non-radiative in contrast to the bright $h$QE$_2$.Comment: 9 pages, 6 figure

Branching Fractions for D0 -> K+K- and D0 -> pi+pi-, and a Search for CP Violation in D0 Decays

Using the large hadroproduced charm sample collected in experiment E791 at Fermilab, we have measured ratios of branching fractions for the two-body singly-Cabibbo-suppressed charged decays of the D0: (D0 -> KK)/(D0 -> Kpi) = 0.109 +- 0.003 +- 0.003, (D0 -> pipi)/(D0 -> Kpi) = 0.040 +- 0.002 +- 0.003, and (D0 -> KK)/(D0 -> pipi) = 2.75 +- 0.15 +- 0.16. We have looked for differences in the decay rates of D0 and D0bar to the CP eigenstates K+K- and pi+pi-, and have measured the CP asymmetry parameters A_CP(K+K-) = -0.010 +- 0.049 +- 0.012 and A_CP(pi+pi-) = -0.049 +- 0.078 +- 0.030, both consistent with zero.Comment: 10 Postscript pages, including 2 figures. Submitted to Phys. Lett.

Asymmetries between the production of D+ and D- mesons from 500 GeV/c pi- nucleon interactions as a function of xF and pt**2

We present asymmetries between the production of D+ and D- mesons in Fermilab experiment E791 as a function of xF and pt**2. The data used here consist of 74,000 fully-reconstructed charmed mesons produced by a 500 GeV/c pi- beam on C and Pt foils. The measurements are compared to results of models which predict differences between the production of heavy-quark mesons that have a light quark in common with the beam (leading particles) and those that do not (non-leading particles). While the default models do not agree with our data, we can reach agreement with one of them, PYTHIA, by making a limited number of changes to parameters used

Search for Rare and Forbidden Dilepton Decays of the D+, Ds, and D0 Charmed Mesons

We report the results of a search for flavor-changing neutral current, lepton-flavor violating, and lepton-number violating decays of D+, Ds, and D0 mesons (and their antiparticles) into modes containing muons and electrons. Using data from Fermilab charm hadroproduction experiment E791, we examine the pi,l,l and K,l,l decay modes of D+ and Ds and the l+l- decay modes of D0. No evidence for any of these decays is found. Therefore, we present branching-fraction upper limits at 90% confidence level for the 24 decay modes examined. Eight of these modes have no previously reported limits, and fourteen are reported with significant improvements over previously published results.Comment: 12 pages, 3 figures, LaTeX, elsart.cls, epsf.sty, amsmath.sty Submitted to Physics Letters

Search for CP Violation in Charged D Meson Decays

We report results of a search for CP violation in the singly Cabibbo-suppressed decays D+ -> K- K+ pi+, phi pi+, K*(892)0 K+, and pi- pi+ pi+ based on data from the charm hadroproduction experiment E791 at Fermilab. We search for a difference in the D+ and D- decay rates for each of the final states. No evidence for a difference is seen. The decay rate asymmetry parameters A(CP), defined as the difference in the D+ and D- decay rates divided by the sum of the decay rates, are measured to be: A(CP)(K K pi) = -0.014 +/- 0.029, A(CP)(phi pi) = -0.028 +/- 0.036, A(CP)(K*(892) K) = -0.010 +/- 0.050, and A(CP)(pi pi pi) = -0.017 +/- 0.042.Comment: 13 pages, 5 figures, 1 table; Elsevier LaTe

Measurement of the form-factor ratios for D+ --> K* l nu

The form factor ratios rv=V(0)/A1(0), r2=A2(0)/A1(0) and r3=A3(0)/A1(0) in the decay D+ --> K* l nu, K* -->K-pi+ have been measured using data from charm hadroproduction experiment E791 at Fermilab. From 3034 (595) signal (background) events in the muon channel, we obtain rv=1.84+-0.11+-0.09, r2=0.75+-0.08+-0.09 and, as a first measurement of r3, we find 0.04+-0.33 +-0.29. The values of the form factor ratios rv and r2 measured for the muon channel are combined with the values of rv and r2 that we have measured in the electron channel. The combined E791 results for the muon and electron channels are rv=1.87+-0.08+-0.07 and r2=0.73+-0.06+-0.08.Comment: 9 pages + 3 figures ; submitted to PL

Differential cross sections, charge production asymmetry, and spin-density matrix elements for D*(2010) produced in 500 GeV/c pi^- nucleon interactions

We report differential cross sections for the production of D*(2010) produced in 500 GeV/c pi^- nucleon interactions from experiment E791 at Fermilab, as functions of Feynman-x (x_F) and transverse momentum squared (p_T^2). We also report the D* +/- charge asymmetry and spin-density matrix elements as functions of these variables. Investigation of the spin-density matrix elements shows no evidence of polarization. The average values of the spin alignment are \eta= 0.01 +- 0.02 and -0.01 +- 0.02 for leading and non-leading particles, respectively.Comment: LaTeX2e (elsart.cls). 13 pages, 6 figures (eps files). Submitted to Physics Letters

Mass Splitting and Production of Σc0\Sigma_c^0 and Σc++\Sigma_c^{++} Measured in 500GeV500 {GeV} π−−\pi^- -N Interactions

From a sample of $2722 \pm 78$ $\Lambda_c^+$ decaying to the $pK^-\pi^+$ final state, we have observed, in the hadroproduction experiment E791 at Fermilab, $143 \pm 20$ $\Sigma_c^0$ and $122 \pm 18$ $\Sigma_c^{++}$ through their decays to $\Lambda_c^+ \pi^{\pm}$. The mass difference $M(\Sigma_c^0) - M(\Lambda_c^+$) is measured to be $(167.38\pm 0.29\pm 0.15) {MeV}$; for $M(\Sigma_c^{++}) - M(\Lambda_c^+)$, we find $(167.76\pm 0.29\pm0.15) {MeV}$. The rate of $\Lambda_c^+$ production from decays of the $\Sigma_c$ triplet is (22\pm 2\pm 3) {%} of the total $\Lambda_c^+$ production assuming equal rate of production from all three, as measured for $\Sigma_c^0$ and $\Sigma_c^{++}$. We do not observe a statistically significant $\Sigma_c$ baryon-antibaryon production asymmetry. The $x_F$ and $p_t^2$ spectra of $\Lambda_c^+$ from $\Sigma_c$ decays are observed to be similar to those for all $\Lambda_c^+$'s produced.Comment: 15 pages, uuencoded postscript 3 figures uuencoded, tar-compressed fil

The doubly Cabibbo-suppressed decay D+→K+π−π+D^+\to K^+ \pi^- \pi^+

We report the observation of the doubly Cabibbo-suppressed decay $D^+\to K^+ \pi^- \pi^+$ in data from Fermilab charm hadroproduction experiment E791. With a signal of 59 \pm 13 events we measured the ratio of the branching fraction for this mode to that of the Cabibbo-favored decay $D^+\to K^- \pi^+ \pi^+$ to be $B(D^+ \to K^+ \pi^- \pi^+) / B(D^+ \to K^- \pi^+ \pi^+) = (7.7 \pm 1.7 \pm 0.8) \times 10^{-3}$. A Dalitz plot analysis was performed to search for resonant structures.Comment: 10 pages, 5 eps figures, RevTe