Divergent and Similar Experiences of ‘Gating’ in South Africa: Johannesburg, Durban and Cape Town

The last 20 years has witnessed an explosion not only in the growth of private residential territories throughout the world, but also in the literature addressing them. The majority of research is centred on experiences in the United States and Latin America (although studies elsewhere are increasing) and suffers from a tendency to homogenise the processes and consequences of gating as synonymous whether experienced in Los Angeles, New York, Mexico City or São Paulo. Whilst axiomatic to state the unlikelihood of identical trends in such differing contexts, the absence of such a statement in the literature is significant. This paper addresses the social and spatial phenomenon of residential gated communities in three of South Africa’s major cities: Johannesburg, Durban and Cape Town. Detailed background and discussion regarding the development and experience of ‘gating’ in each city is analysed, emphasising the uniqueness of each city’s gating experience. These indications, that gating is not a universal experience despite some common themes, serve to counter the homogenous discourse in both popular and academic parlance throughout the world and within South Africa. In addition, particular concerns related to the growth of residential forms based on exclusion and privatisation within the South African context, are considered. In essence, we conclude that while ‘gating’ may be an individually rational decision in the context of South Africa’s growing crime, its collective consequences produce a divided city, at odds with post-apartheid ideals of unity and equality.     

Casein peptides with inhibitory activity on lipid oxidation in beef homogenates and mechanically deboned poultry meat

Bioactive peptides obtained by enzymatic hydrolysis of casein may have antioxidant activity. In this work, casein peptides were obtained using the proteolytic enzymes Alcalase and Flavourzyme. Casein was hydrolyzed for 4 h at 50 °C and pH 8, and the resulting peptides were analyzed. The enzymatic hydrolysis with Flavourzyme resulted in higher concentration of soluble protein and free amino acids, and produced peptides with lower molecular mass than those obtained with Alcalase, as observed by gel permeation chromatography and polyacrylamide gel electrophoresis. Casein peptides obtained with Flavourzyme also exhibited greater antioxidant capacity using the ABTS radical method. Casein peptides (20 mg ml⁻¹) effectively inhibited lipid peroxidation in ground beef homogenates and mechanically deboned poultry meat. Casein peptides may be useful in meat processing as another naturally occurring antioxidant, helping to prevent off-flavor formation in meat products and increasing shelf life.     

Tunable resonance transmission modes in hybrid heterostructures based on porous silicon

ABSTRACT: In this work, we report the experimental results and theoretical analysis of strong localization of resonance transmission modes generated by hybrid periodic/quasiperiodic heterostructures (HHs) based on Porous Silicon (PSi). The HHs are formed by stacking a quasiperiodic Fibonacci (FN) substructure between two Distributed Bragg Reflectors (DBRs). FN substructure defines the number of strong localized modes that can be tunable at any given wavelength and be unfolded when a partial periodicity condition is imposed. These structures show interesting properties for biomaterials research, biosensor applications and basic studies of adsorption of organic molecules. We also demonstrate the sensitivity of HHs to material infiltration.     

Microsporogenesis in tetraploid accessions of Brachiaria nigropedata (Ficalho & Hiern) Stapf (Gramineae).

The genus Brachiaria (Trin.) Griseb. has achieved considerable importance to cattle production systems, as a result of the good production and adaptation of a few cultivars to poor and acid soils of the Brazilian savannas. Many of its species and accessions are polyploid and apomictic, which limits direct hybridization. To assist the breeding program, cytogenetic characterization has been undertaken on the accessions of Brachiaria collection at the Embrapa Beef Cattle Research Center. In this study, chromosome number and meiotic behavior are reported for the Brachiaria nigropedata (Ficalho & Hiern) Stapf collection. The 20 available accessions are tetraploid (2n = 4x = 36). Chromosomes paired preferentially as bivalents, but quadrivalents were found in high frequencies in some cells. Meiotic behavior was, in general, irregular, and varied among accessions. Most accessions presented more than 20% of abnormal tetrads. The most common meiotic abnormalities were those related to irregular chromosome segregation due to polyploidy, leading to micronuclei formation in the tetrad stage. A low frequency of other meiotic abnormalities such as the absence of cytokinesis, chromosome stickiness, cell fusion, anaphase bridges, and chromosome transfer among microsporocytes were also recorded in some accessions. Limitations of these accessions for use in hybridization programs are discussed.     

Effective proximity retrieval by ordering permutations

We introduce a new probabilistic proximity search algorithm for range and K-nearest neighbor (K-NN) searching in both coordinate and metric spaces. Although there exist solutions for these problems, they boil down to a linear scan when the space is intrinsically high-dimensional, as is the case in many pattern recognition tasks. This, for example, renders the K-NN approach to classification rather slow in large databases. Our novel idea is to predict closeness between elements according to how they order their distances towards a distinguished set of anchor objects. Each element in the space sorts the anchor objects from closest to farthest to it, and the similarity between orders turns out to be an excellent predictor of the closeness between the corresponding elements. We present extensive experiments comparing our method against state-of-the-art exact and approximate techniques, both in synthetic and real, metric and non-metric databases, measuring both CPU time and distance computations. The experiments demonstrate that our technique almost always improves upon the performance of alternative techniques, in some cases by a wide margin.     

Interactive Dynamics of Cell Volume and Cell Death in Human Erythrocytes Exposed to α-Hemolysin from Escherichia coli

α-hemolysin (HlyA) of E. coli binds irreversibly to human erythrocytes and induces cell swelling, ultimately leading to hemolysis. We characterized the mechanism involved in water transport induced by HlyA and analyzed how swelling and hemolysis might be coupled. Osmotic water permeability (P_f) was assessed by stopped-flow light scattering. Preincubation with HlyA strongly reduced P_f in control- and aquaporin 1-null red blood cells, although the relative P_f decrease was similar in both cell types. The dynamics of cell volume and hemolysis on RBCs was assessed by electrical impedance, light dispersion and hemoglobin release. Results show that HlyA induced erythrocyte swelling, which is enhanced by purinergic signaling, and is coupled to osmotic hemolysis. We propose a mathematical model of HlyA activity where the kinetics of cell volume and hemolysis in human erythrocytes depend on the flux of osmolytes across the membrane, and on the maximum volume that these cells can tolerate. Our results provide new insights for understanding signaling and cytotoxicity mediated by HlyA in erythrocytes.     

Potential Food Applications of Biobased Materials. An EU‐Concerted Action Project

The objective of the study was to ascertain the state of the art with regard to the applicability of biobased packaging materials to foods and to identify potential food applications for biobased materials. The study revealed relatively few examples of biobased materials used as primary, secondary or tertiary packaging materials for foods. This is due to the fact that published investigations on the use of biobased materials are still scarce, and results obtained remain unpublished because of commercial pressures. The scientific literature contains numerous reports on applications of edible films and coatings to food but novel commercial applications of these are scarce. Based on information currently available on the properties of biobased packaging materials the study identified products in the fresh meat, dairy, ready meal, beverage, fruit and vegetable, snack, frozen food and dry food categories where conventional packaging may be replaced by biobased packaging.     

Physical and Mechanical Properties of Biobased Materials Starch,Polylactate and Polyhydroxybutyrate

Commercial and semi‐commercial biobased materials (Polylactate, PLA, polyhydroxy‐butyrate, PHB, wheat starch and corn starch) were investigated. Physical and mechanical characterisation (tensile strength, elongation, tear strength, compression, gas permeability (CO₂ and O₂) and water vapour permeability (WVP)) was examined. Tests on both films and cups show potential use of these materials for primary food packaging, especially PLA and PHB. An interesting O₂:CO₂ permeability ratio (1:7 to 1:12) was seen, which make these materials suitable for packaging of food with high respiration. The mechanical properties were comparable to conventional materials such as polyethylene (PE) and polystyrene (PS). The WVP measured on films ranged from 12.6 to 18.6 [g H₂O/(m² ? 24h)], and on cups the range was 2.2 to 10.5 [g H₂O ? 700 μm/(m² ? 24h)]. The WVP for the starch‐based materials seems to be the most crucial parameter, and needs improvement if these materials are to be used as food packaging.