Phytophthora Blight Of Pigeon Pea In India

Isolations were made from blighted pigeon-pea (Cajanus cajan) plants from different locations in India. A species of Phytophthora was consistently obtained from these locations and was proved to be the causal organism involved in the disease. Based on the sporangium shape and size, oogonium and oospore formation, temperature requirements, and pathogenicity tests, we have classified these isolates as P. drechsleri f. sp. cajani. The use of formae speciales was considered appropriate because of the specificity of these isolates to pigeon pea and Atylosia spp., wild relatives of the pigeon pea

Characterization of the proposed 4-α cluster state candidate in O 16

The O16(α,α′) reaction was studied at θlab=0 at an incident energy of Elab=200 MeV using the K600 magnetic spectrometer at iThemba LABS. Proton decay and α decay from the natural parity states were observed in a large-acceptance silicon strip detector array at backward angles. The coincident charged-particle measurements were used to characterize the decay channels of the 06+ state in O16 located at Ex=15.097(5) MeV. This state is identified by several theoretical cluster calculations to be a good candidate for the 4-α cluster state. The results of this work suggest the presence of a previously unidentified resonance at Ex≈15 MeV that does not exhibit a 0+ character. This unresolved resonance may have contaminated previous observations of the 06+ state

Isoscalar giant monopole strength in 58^{58}Ni, 90^{90}Zr, 120^{120}Sn and 208^{208}Pb

Inelastic $\alpha$-particle scattering at energies of a few hundred MeV and very-forward scattering angles including $0^\circ$ has been established as a tool for the study of the isoscalar giant monopole (IS0) strength distributions in nuclei. An independent investigation of the IS0 strength in nuclei across a wide mass range was performed using the $0^\circ$ facility at iThemba Laboratory for Accelerator Based Sciences (iThemba LABS), South Africa, to understand differences observed between IS0 strength distributions in previous experiments performed at the Texas A\&M University (TAMU) Cyclotron Institute, USA and the Research Center for Nuclear Physics (RCNP), Japan. The isoscalar giant monopole resonance (ISGMR) was excited in $^{58}$Ni, $^{90}$Zr, $^{120}$Sn and $^{208}$Pb using $\alpha$-particle inelastic scattering with $196$ MeV $\alpha$ beam and scattering angles $\theta_{\text{Lab}} = 0^\circ$ and $4^\circ$. The K$600$ magnetic spectrometer at iThemba LABS was used to detect and momentum analyze the inelastically scattered $\alpha$ particles. The IS0 strength distributions in the nuclei studied were deduced with the difference-of-spectra (DoS) technique including a correction factor for the $4^\circ$ data based on the decomposition of $L > 0$ cross sections in previous experiments. IS0 strength distributions for $^{58}$Ni, $^{90}$Zr, $^{120}$Sn and $^{208}$Pb are extracted in the excitation-energy region $E_{\rm x} = 9 - 25$ MeV.Using correction factors extracted from the RCNP experiments, there is a fair agreement with their published IS0 results. Good agreement for IS0 strength in $^{58}$Ni is also obtained with correction factors deduced from the TAMU results, while marked differences are found for $^{90}$Zr and $^{208}$Pb.Comment: 12 pages, 10 figures, regular article submitted to PR

Fine structure of the isoscalar giant monopole resonance in 58^{58}Ni, 90^{90}Zr, 120^{120}Sn and 208^{208}Pb

Over the past two decades high energy-resolution inelastic proton scattering studies were used to gain an understanding of the origin of fine structure observed in the isoscalar giant quadrupole resonance (ISGQR) and the isovector giant dipole resonance (IVGDR). Recently, the isoscalar giant monopole resonance (ISGMR) in $^{58}$Ni, $^{90}$Zr, $^{120}$Sn and $^{208}$Pb was studied at the iThemba Laboratory for Accelerator Based Sciences (iThemba LABS) by means of inelastic $\alpha$-particle scattering at very forward scattering angles (including $0\circ$). The good energy resolution of the measurement revealed significant fine structure of the ISGMR.~To extract scales by means of wavelet analysis characterizing the observed fine structure of the ISGMR in order to investigate the role of different mechanisms contributing to its decay width. Characteristic energy scales are extracted from the fine structure using continuous wavelet transforms. The experimental energy scales are compared to different theoretical approaches performed in the framework of quasiparticle random phase approximation (QRPA) and beyond-QRPA including complex configurations using both non-relativistic and relativistic density functional theory. All models highlight the role of Landau fragmentation for the damping of the ISGMR especially in the medium-mass region. Models which include the coupling between one particle-one hole (1p-1h) and two particle-two hole (2p-2h) configurations modify the strength distributions and wavelet scales indicating the importance of the spreading width. The effect becomes more pronounced with increasing mass number. Wavelet scales remain a sensitive measure of the interplay between Landau fragmentation and the spreading width in the description of the fine structure of giant resonances.Comment: 13 pages,7 figures, regular articl

Isospin mixing and the cubic isobaric multiplet mass equation in the lowest <i>T</i>=2, <i>A</i>=32 quintet

The isobaric multiplet mass equation (IMME) is known to break down in the first T = 2, A = 32 isospin quintet. In this work we combine high-resolution experimental data with state-of-the-art shell-model calculations to investigate isospin mixing as a possible cause for this violation. The experimental data are used to validate isospin-mixing matrix elements calculated with newly developed shell-model Hamiltonians. Our analysis shows that isospin mixing with nonanalog T = 1 states contributes to the IMME breakdown, making the requirement of an anomalous cubic term inevitable for the multiplet

Refuting the nature of the sixth 0+ Hoyle-analogue state candidate in 16O

A prominent candidate for a Hoyle-analogue state in 16O is the 0+ 6 state, previously observed at Ex = 15.097(5) MeV. This state is identified by several theoretical cluster calculations to be a good candidate for the 4-α cluster state, analogous to the Hoyle state in 12C. Whilst much theoretical work has been performed to reconcile a calculated α-cluster state with this resonance, the experimental information on this state remained very scarce. To investigate this state, the 16O(α, α') reaction was studied at θlab = 0° at an incident energy of Elab = 200 MeV using the K600 magnetic spectrometer at iThemba LABS. For the first time, the decay channels of the Ex = 15.097(5) MeV state were isolated using a large acceptance silicon-strip detector array at backward angles. The lineshapes of the states were analysed within a phenomenological R-matrix framework. Results indicate the presence of a resonance at Ex ≈ 15 MeV which does not exhibit a Jπ = 0+ nature

An integrated online radioassay data storage and analytics tool for nEXO

Large-scale low-background detectors are increasingly used in rare-event searches as experimental collaborations push for enhanced sensitivity. However, building such detectors, in practice, creates an abundance of radioassay data especially during the conceptual phase of an experiment when hundreds of materials are screened for radiopurity. A tool is needed to manage and make use of the radioassay screening data to quantitatively assess detector design options. We have developed a Materials Database Application for the nEXO experiment to serve this purpose. This paper describes this database, explains how it functions, and discusses how it streamlines the design of the experiment