Numerical simulations of rotating sunspots

A numerical model of idealized, axisymmetric, rotating sunspots is presented. The model contains a compressible plasma described by the nonlinear MHD equations, with density and temperature gradients simulating the upper layer of the sun’s convection zone. The solution forms a central flux tube in the cylindrical numerical domain, with convection cells pushing the magnetic field to the axis. When the numerical domain is rotated with a constant angular velocity, the umbra rotates as a rigid body while the surrounding convection cells show a swirling, vortical flow. As a result, the azimuthal velocity and magnetic field have their maximum values close to the flux tube, inside the innermost convection cell

Towards reconciliation of structure with function in plasmodesmata—who is the gatekeeper?

Whilst the structure of higher plant plasmodesmata was first described by Robards (1963. Desmotubule—a plasmodesmatal substructure. Nature 218, 784), and despite many subsequent intensive investigations, there is still much that remains unclear relating to their ultrastructure and functioning in higher plants. We have examined chemically fixed plant material, and suggest that the conformational changes seen in plasmodesmatal substructure, particularly the deposition of electron-dense extra-plasmodesmal material, is linked to either manipulation of the hormonal balance (as in Avocado fruit), or of osmotic potential in leaf blade material. These changes result in the deposition of β 1,3-glucan (callose) at the neck region of these plasmodesmata. This electron-dense material is deposited at the neck region of plasmodesmata, and forms a collar-like structure. The formation of a collar is shown to be coupled with loss of lucence within the cytoplasmic sleeve. The formation of a collar at the plasmodesmatal orifice thus results in encapsulation and closure of the plasmodesmatal orifice. Closure of the orifice coincides with a loss of electron-lucence and a lack of resolution of the desmotubule. These ultrastructural changes are potentially significant and could contribute to, result in, or assist in the down-regulation of cell to cell trafficking via plasmodesmata

Plasmodesmatal frequency in relation to short-distance transport and phloem loading in leaves of barley (Hordeum vulgare). Phloem is not loaded directly from the symplast

We investigated the phloem loading pathway in barley, by determining plasmodesmatal frequencies at the electron microscope level for both intermediate and small blade bundles of mature barley leaves. Lucifer yellow was injected intercellularly into bundle sheath, vascular parenchyma, and thin-walled sieve tubes. Passage of this symplastically transported dye was monitored with an epifluorescence microscope under blue light. Low plasmodesmatal frequencies endarch to the bundle sheath cells are relatively low for most interfaces terminating at the thin- and thick-walled sieve tubes within this C3 species. Lack of connections between vascular parenchyma and sieve tubes, and low frequencies (0.5% plasmodesmata per μm cell wall interface) of connections between vascular parenchyma and companion cells, as well as the very low frequency of pore-plasmodesmatal connections between companion cells and sieve tubes in small bundles (0.2% plasmodesmata per μm cell wall interface), suggest that the companion cell-sieve tube complex is symplastically isolated from other vascular parenchyma cells in small bundles. The degree of cellular connectivity and the potential isolation of the companion cell-sieve tube complex was determined electrophysiologically, using an electrometer coupled to microcapillary electrodes. The less negative cell potential {average -52 mV) from mesophyll to the vascular parenchyma cells contrasted sharply with the more negative potential (-122.5 mV) recorded for the companion cell-thin-walled sieve tube complex. Although intercellular injection of lucifer yellow clearly demonstrated rapid (0.75 μm s-1) longitudinal and radial transport in the bundle sheath-vascular parenchyma complex, as well as from the bundle sheath through transverse veins to adjacent longitudinal veins, we were neither able to detect nor present unequivocal evidence in support of the symplastic connectivity of the sieve tubes to the vascular parenchyma. Injection of the companion cell-sieve tube complex, did not demonstrate backward connectivity to the bundle sheath. We conclude that the low plasmodesmatal frequencies, coupled with a two-domain electropotential zonation configuration, and the negative transport experiments using lucifer yellow, precludes symplastic phloem loading in barley leaves

Evaluation of the Impact of the Watu Ata Nature Reserve Policy Setting

The major theme of this paper is to evaluate policy impacts. This paper aims to evaluate the impact of the determination of the Watu Ata Nature Reserve using the evaluation criteria proposed by William N. Dunn: Effectiveness, Equity, Responsiveness and Appropriateness. As defined in RI Government Regulation No. 28 of 2011 Article 1, a nature reserve is an area which, due to its natural condition, contains unique plants and/or plant diversity along with natural phenomena and whose ecosystem requires protection and preservation efforts so that its existence and development can grow naturally. The Watu Ata Nature Reserve is one nature reserve area in the Ngada regency based on the Decree of Minister of Forestry No. 432/Kpts-II/92. The research method used is a descriptive qualitative study that employs a field study approach conducted in two villages, namely, Heawea Village and Inelika Village. These two villages have the biggest community's land in the Watu Ata Nature Reserve. The findings suggest that the Watu Ata Nature Reserve policy has had a negative impact on people living around the nature reserve area, particularly with respect to their loss of access to the cultivated land and cultural sites where they have built relationships with their deceased ancestors

The microstructure of plasmodesmata in internodal stem tissue of the Saccharum hybrid var. NCo376 : evidence for an apoplasmic loading pathway

The distribution, structure and functional state of plasmodesmata were investigated to gain a clearer understanding of the sucrose transport pathway to the storage parenchyma cells in stem tissue in Saccharum officinarum var. NCo376. Evidence from structural studies on sugarcane stems by electron microscopy indicated that there are numerous plasmodesmata from the vascular bundles through to the storage parenchyma cells in mature stem tissue. Our studies, supported by fluorescence microscopy and iontophoresis, indicate that there are functional plasmodesmata in the phloemunloading pathway from transport phloem tissue to the bundle sheath in Saccharum, which could support symplasmic transport; plasmodesmata outside of the sheath cells in the storage parenchyma appear to be constricted by sphincter-like structures within their neck regions. Staining with Aniline Blue revealed evidence of large callose deposits, which co-localized with plasmodesmatal aggregates in the walls of the storage parenchyma cells. This suggests that the sucrose transport into, and accumulation by, storage parenchyma of mature stem tissue is under apoplasmic control

"Be active!" Revisiting the South African Food Based Dietary Guidelines for activity

The objective of this paper was to review current evidence on physical activity for health in order to support the foodbased dietary guideline (FBDG) “Be active!”. Physical activity, defined as at least 30 minutes of moderate-intensity physical activity per day for adults, and 60 minutes for children and adolescents, is advised in the FBDG because of the role it plays in maintaining energy balance, improving body composition and promoting general health and wellbeing. The reviewed outcome measures are changes in physical activity patterns and the reported prevalence of noncommunicable diseases (NCDs) in South Africa. Despite the previous set of FBDGs, no improvements in physical activity, obesity or NCDs have been reported in South Africa. Recent literature emphasises the beneficial effects of physical activity on the reduction of risk factors associated with the prevalence of NCDs. Physical activity has a positive effect on appetite and weight control, insulin sensitivity, dyslipidaemia, hypertension, stress relief and burnout. Barriers that prevent children and adults from participating in regular physical activity have been identified, and recommendations how to overcome these have been made. It has been concluded that South Africans are not sufficiently physically active for their general health status to be improved. It is recommended that methods to promote physical activity at national, provincial, district and local level need to be developed, implemented and sustained

Learning Area Methodology B: Mathematics

Exam paper for second semester (Supplementary) Learning Area Methodology B: Mathematic

Phloem loading in the sucrose-export-defective (SXD-1) mutant maize is limited by callose deposition at plasmodesmata in bundle sheath-vascular parenchyma interface

Using Lucifer Yellow we have demonstrated that the phloem-loading pathway from the mesophyll to the bundle sheath-vascular parenchyma interface in Zea mays source leaves follows a symplasmic route in small and intermediate vascular bundles in control as well as in the green sections of mutant sucrose-export-defective (SXD-1) plants. In the anthocyanin-rich mutant leaf sections, Lucifer Yellow transport was prohibited along the same path, at the bundle sheath-vascular parenchyma interface in particular. Plasmodesmata at the latter interface in SXD-1 anthocyanin-rich leaf sections appear to be structurally altered through callose deposition at the plasmodesmal orifices. We suggest that a transport bottleneck at the bundle sheath-vascular parenchyma interface is thus orchestrated and regulated through callose formation, preventing symplasmic transport across this important loading interface