Entropic exponents of grafted lattice stars.

The surface entropic exponents of half-space lattice stars grafted at their central nodes in a hard wall are estimated numerically using the PERM algorithm. In the square half-lattice the exact values of the exponents are verified, including Barber's scaling relation and a generalization for 2-stars with one and two surface loops respectively. This is the relation γ_{211}=2γ_{21}-γ_{20}, where γ_{21} and γ_{211} are the surface entropic exponents of a grafted 2-star with one and two surface loops, respectively, and γ_{20} is the surface entropic exponent with no surface loops. This relation is also tested in the cubic half-lattice where surface entropic exponents are estimated up to 5-stars, including many with one or more surface loops. Barber's scaling relation and the relation γ_{3111}=γ_{30}-3γ_{31}+3γ_{311} are also tested, where the exponents {γ_{31},γ_{311},γ_{3111}} are of grafted 3-stars with one, two, or three surface loops, respectively, and γ_{30} is the surface exponent of grafted 3-stars.

Numerical estimates of square lattice star vertex exponents.

We implement parallel versions of the generalized atmospheric Rosenbluth methods and Wang-Landau algorithms for stars and for acyclic uniform branched networks in the square lattice. These are models of monodispersed branched polymers, and we estimate the star vertex exponents σ_{f} for f stars, and the entropic exponent γ_{G} for networks with comb and brush connectivity in two dimensions. Our results verify the predicted (but not rigorously proven) exact values of the vertex exponents and we test the scaling relation [B. Duplantier, J. Stat. Phys. 54, 581 (1989)JSTPBS0022-471510.1007/BF01019770]γ_{G}-1=[under ∑]f≥1m_{f}σ_{f}for several acyclic branched networks in two dimensions.

Phase diagrams of confined square lattice linked polygons.

The phase diagrams of two models of two confined and dense two-dimensional ring polymers are examined numerically. The ring polymers are modeled by square lattice polygons in a square cavity and are placed to be either unlinked or linked in the plane. The phase diagrams of the two models are found to be a function of the placement of the ring polymers and include multicritical points where first-order and continuous phase boundaries meet. We estimate numerically the critical exponents associated with the phase boundaries and the multicritical points.

Price dynamics of red meat types in South Africa for the period 2013 to 2017.

The agricultural product market is changing from a producer-orientated to a more consumer-orientated market. Consumer rely on the classification system within the red meat types. Different red meat types and carcass classifications influence the prices of red meat. This study was conducted to determine the price dynamics of different red meat carcasses and carcass classes. It was theorised that the different red meat classification classes and number of carcasses sold influence the price and demand of red meats. It was also theorised that specific meat classes have a greater influence on meat prices and demand than others. The results of this study supports the hypothesis that red meat carcass type and specific meat classes within carcass type influence red meat carcass prices. There is a differentiation among classes in terms of the degree to which class influences price, since classes were identified that had no influence on price dynamics of other meat types.

Reply to "Comment on 'Osmotic pressure of compressed lattice knots' ".

The free energy of a model of uniformly weighted lattice knots of length n and knot type K confined to a lattice cube of side length L-1 is given by F_{L}(ϕ)=-1/Vlogp_{n,L}(K), where V=L^{3} and where ϕ=n/V is the concentration of monomers of the lattice knot in the confining cube. The limiting free energy of the model is F_{∞}(ϕ)=lim_{L→∞}F_{L}(ϕ) and the limiting osmotic pressure of monomers leaving the lattice knot to become solvent molecules is defined by Π_{∞}(ϕ)=ϕ^{2}d/dϕ[F_{∞}(ϕ)/ϕ]. I show that, under very mild assumptions, the functions P_{L}(ϕ)=ϕ^{2}d/dϕ[F_{L}(ϕ)/ϕ]|_{n} and Π_{L}(ϕ)=ϕ^{2}d/dϕ[F_{L}(ϕ)/ϕ]|_{L} are finite-size approximations of Π_{∞}(ϕ).

Osmotic pressure of compressed lattice knots.

A numerical simulation shows that the osmotic pressure of compressed lattice knots is a function of knot type, and so of entanglements. The osmotic pressure for the unknot goes through a negative minimum at low concentrations, but in the case of nontrivial knot types 3_{1} and 4_{1} it is negative for low concentrations. At high concentrations the osmotic pressure is divergent, as predicted by Flory-Huggins theory. The numerical results show that each knot type has an equilibrium length where the osmotic pressure for monomers to migrate into and out of the lattice knot is zero. Moreover, the lattice unknot is found to have two equilibria, one unstable, and one stable, whereas the lattice knots of type 3_{1} and 4_{1} have one stable equilibrium each.

Isolation of Cellulose Degrading Fungi from Decaying Banana Pseudostem and Strelitzia alba.

Cellulases are a group of hydrolytic enzymes that break down cellulose to glucose units. These enzymes are used in the food, beverage, textile, pulp, and paper and the biofuel industries. The aim of this study was to isolate fungi from natural compost and produce cellulases in submerged fermentation (SmF). Initial selection was based on the ability of the fungi to grow on agar containing Avicel followed by cellulase activity determination in the form of endoglucanase and total cellulase activity. Ten fungal isolates obtained from the screening process showed good endoglucanase activity on carboxymethyl cellulose-Congo Red agar plates. Six of the fungal isolates were selected based on high total cellulase activity and identified as belonging to the genera Trichoderma and Aspergillus. In SmF of synthetic media with an initial pH of 6.5 at 30°C Trichoderma longibrachiatum LMLSAUL 14-1 produced total cellulase activity of 8 FPU/mL and endoglucanase activity of 23 U/mL whilst Trichoderma harzianum LMLBP07 13-5 produced 6 FPU/mL and endoglucanase activity of 16 U/mL. The produced levels of both cellulases and endoglucanase by Trichoderma species were higher than the levels for the Aspergillus fumigatus strains. Aspergillus fumigatus LMLPS 13-4 produced higher ß-glucosidase 38 U/mL activity than Trichoderma species.

The effect of technology assisted therapy for intellectually and visually impaired adults suffering from separation anxiety: Conquering the fear.

Persons with an intellectual disability (ID) are at risk of developing separation anxiety (SA) and, if left untreated, this can be a risk factor for the development of psychopathology. The effects of an intervention, namely technology assisted therapy for SA (TTSA), were examined on the SA, challenging behavior, psychosocial functioning, and quality of life (QOL) experienced by moderate to mild intellectually and visually disabled adults. This study aimed to determine whether TTSA reduces SA and challenging behavior in persons with ID and visual impairment, and if this results in increased psychosocial functioning and QOL. A pre-experimental within-group design with randomized multiple baselines and staggered intervention start-points was used (n = 6). The variables were monitored with standardized instruments. The frequencies of each participant's use of the technology and the frequency and intensity of their behavior were recorded over time. Results indicate that the SA and challenging behavior experienced by the participants decreased significantly and their psychosocial functioning and QOL increased significantly. The conclusions are that TTSA has the potential to be a valid intervention to address SA in adults with visual and moderate to mild IDs.

Mean field analysis of algorithms for scale-free networks in molecular biology.

The sampling of scale-free networks in Molecular Biology is usually achieved by growing networks from a seed using recursive algorithms with elementary moves which include the addition and deletion of nodes and bonds. These algorithms include the Barabási-Albert algorithm. Later algorithms, such as the Duplication-Divergence algorithm, the Solé algorithm and the iSite algorithm, were inspired by biological processes underlying the evolution of protein networks, and the networks they produce differ essentially from networks grown by the Barabási-Albert algorithm. In this paper the mean field analysis of these algorithms is reconsidered, and extended to variant and modified implementations of the algorithms. The degree sequences of scale-free networks decay according to a powerlaw distribution, namely P(k) ∼ k-γ, where γ is a scaling exponent. We derive mean field expressions for γ, and test these by numerical simulations. Generally, good agreement is obtained. We also found that some algorithms do not produce scale-free networks (for example some variant Barabási-Albert and Solé networks).

Attachment relationships of preschool-aged children of mothers with HIV and HIV-related psychosis.

Children from mothers with HIV-related psychosis are frequently raised in challenging contexts, yet the extent to which these children grow up in insecure or disordered attachment relationships is unknown. Using the Strange Situation Procedure the distribution of attachment relationships of children from mothers with HIV and psychosis (n = 45) was compared with children from mothers with HIV without psychosis (n = 41). No significant differences in the distributions were found between the two groups and attachment was not associated with specific psychotic symptomatology. Security of attachment was associated with more people providing the mother with emotional support, but only in the psychosis group. Disordered attachment (24%) was more often found in the total sample than in studies with other normal and high risk populations. Recommendations were made for future research about factors facilitating resilience in the children and on interventions increasing emotional support for affected mothers.

Caregiver-mediated therapy for an adult with visual and intellectual impairment suffering from separation anxiety.

BACKGROUND: Separation anxiety among intellectually disabled (ID) persons with comorbid visual impairment could be rooted in a weak sense of person permanence. Technology-assisted Therapy for Separation Anxiety (TTSA) was used to address this problem. AIMS: The primary aim was to determine whether technology alone or including caregivers was the best option, and whether TTSA decreased separation anxiety and challenging behaviour. Also, how the caregivers and the client experienced TTSA. METHODS AND PROCEDURES: A pre-experimental, quantitative approach (AB1C1B2C2D) was used for this single-subject study. The frequency of the client's text messages was recorded daily. The variables were monitored with standardised instruments and caregivers rated the intensity and frequency of the client's anxious and challenging behaviour. The social validity was evaluated by means of questionnaires. OUTCOMES AND RESULTS: There was a significant decrease in the anxious and angry messages sent, and in anxious and challenging behaviour, in the phase in which the caregivers were included, compared with the phase in which technology alone was used. The client and the caregivers were positive about TTSA. CONCLUSION AND IMPLICATION: Technology and the caregivers reactions reduces the anxiety and challenging behaviour. It might also aid the acquisition of the concept of person permanence.

Optimization of carbon and nitrogen medium components for biomass production using non-Saccharomyces wine yeasts.

UNLABELLED: The impact of different nitrogen and carbon sources on biomass production of the non-Saccharomyces wine yeast species Lachancea thermotolerans, Metschnikowia pulcherrima and Issatchenkia orientalis was assessed. Using a molasses-based medium, yeast extract and corn steep liquor as well as ammonium sulphate and di-ammonium phosphate (DAP) as nitrogen sources were compared in shake-flask cultures. A medium with 20 g l⁻¹ sugar (diluted molasses) and 500 mg l⁻¹ total yeast assimilable nitrogen, from yeast extract, gave the highest biomass concentrations and yields. Invertase pretreatment was required for cultures of M. pulcherrima and I. orientalis, and respective biomass yields of 0.7 and 0.8 g g⁻¹ were achieved in aerobic bioreactor cultures. The absence of ethanol production suggested Crabtree-negative behaviour by these yeasts, whereas Crabtree-positive behaviour by L. thermotolerans resulted in ethanol and biomass concentrations of 5.5 and 11.1 g l⁻¹, respectively. SIGNIFICANCE AND IMPACT OF THE STUDY: Recent studies demonstrate that non-Saccharomyces yeasts confer positive attributes to the final composition of wine. However, optimal process conditions for their biomass production have not been described, thereby limiting commercial application. In this study, industrial media and methods of yeast cultivation were investigated to develop protocols for biomass production of non-Saccharomyces yeast starter cultures for the wine industry.

Student nurses' experience working with mentally challenged individuals in South Africa.

South African student nurses experience emotional discomfort that might influence their adjustment and coping while working with mentally challenged individuals. Adjustment and coping might impact on their mental health and support needed while working in this challenging context. Student nurses working with mentally challenged individuals experience emotional discomfort that may result in work-related stress. The experiences of student nurses working with mentally challenged individuals were explored and described as it may influence their adjustment, coping and result in work-related stress, impacting on their mental health. The study used a qualitative, explorative, descriptive, contextual research design with a case study as strategy. Thirteen student nurses from a specific higher educational institution in Gauteng, South Africa, participated in the focus group interviews. The researcher utilized reflective journals, a reflective letter, naïve sketches, drawings and field notes to collect data. Data analysis was done according to Tesch's descriptive method of open coding and theme analysis. A central storyline emerged where student nurses described working with mentally challenged individuals as a process of personal transformation that was initiated by an engagement on a deeper emotional level with these individuals. The process of personal transformation started a journey towards the discovery of meaning for the self, as student nurses. Student nurses working in challenging environments during their training may experience emotional discomfort and need additional support in coping and adjustment within this context. The nurse educator plays an important role in providing this support to manage work-related stress as well as in creating learning opportunities for the student nurses working in challenging contexts.

Cancer prevalence in 129 breast-ovarian cancer families tested for BRCA1 and BRCA2 mutations.

BACKGROUND: Women who carry germline mutations in the breast-ovarian cancer susceptibility genes, BRCA1 and BRCA2, are at very high risk of developing breast and/or ovarian cancer. Both genes are tumour suppressor genes that protect all cells from deregulation, and there are reports of their involvement in other cancers that vary and seem to depend on the population investigated. It is therefore important to investigate the other associated cancers in different populations to assist with risk assessments. OBJECTIVES: To assess the cancer risk profile in BRCA-mutation-positive and negative South African breast-ovarian cancer families, mainly of Caucasian origin. DESIGN: Descriptive study in which the prevalence of all cancers in the pedigrees of BRCA1- and BRCA2-mutation-positive groups and a group of families without mutations in either gene were compared with the general population. RESULTS: As expected, female breast and ovarian cancer was significantly increased in all three groups. Furthermore, male breast cancer was significantly elevated in the BRCA2-positive and BRCA-negative groups. Stomach cancer prevalence was significantly elevated in the BRCA2-positive families compared with the general population. CONCLUSIONS: These results can be applied in estimation of cancer risks and may contribute to more comprehensive counselling of mutation-positive Caucasian breast and/or ovarian cancer families.

Emergence and diversity of different HIV-1 subtypes in South Africa, 2000-2001.

HIV-1 is a major health problem in South Africa with an average prevalence rate of 29.1% in pregnant women and between 4.9 and 6.1 million people infected. Using env gp120 V3 serotyping and genotyping techniques 410 patient samples were investigated. Most of the samples were obtained from different clinics in the greater Cape Town area of the Western Cape Province in South Africa. These included an academic hospital, state and private clinics, an informal settlement, sex worker cohorts, and the blood transfusion services. RNA was extracted from plasma samples followed by RT-PCR and sequencing of the env gp120 V3 region. Sequence fragments were assembled using Sequencher V4.7 and subsequently codon aligned. Distance calculation, tree construction methods, and bootstrap analysis were implemented using MEGA version 4.0. Viral load measurements indicated that HIV-1 RNA levels from 74 samples were below the assay detection limit. Three hundred thirty-six samples were used for env PCR and sequencing and 320 were assigned to subtypes. The majority of the sequences were subtyped as C (n = 285, 89.0%). Other subtypes detected were subtype A (n = 10, 3.1%); subtype B (n = 22, 6.8%); one each of subtypes F1, G, U, and a CH recombinant. Whether this diversity will have major implications for HIV-1 evolution and vaccine development in this region remains undetermined.

Strong association of de novo copy number mutations with sporadic schizophrenia.

Schizophrenia is an etiologically heterogeneous psychiatric disease, which exists in familial and nonfamilial (sporadic) forms. Here, we examine the possibility that rare de novo copy number (CN) mutations with relatively high penetrance contribute to the genetic component of schizophrenia. We carried out a whole-genome scan and implemented a number of steps for finding and confirming CN mutations. Confirmed de novo mutations were significantly associated with schizophrenia (P = 0.00078) and were collectively approximately 8 times more frequent in sporadic (but not familial) cases with schizophrenia than in unaffected controls. In comparison, rare inherited CN mutations were only modestly enriched in sporadic cases. Our results suggest that rare de novo germline mutations contribute to schizophrenia vulnerability in sporadic cases and that rare genetic lesions at many different loci can account, at least in part, for the genetic heterogeneity of this disease.

Effect of pH, temperature and nutrient limitations on growth and leukotoxin production by Mannheimia haemolytica in batch and continuous culture.

AIMS: Quantification of the effects of pH, temperature and nutrient limitations on the growth and leukotoxin (LKT) production parameters of Mannheimia haemolytica in batch and chemostat culture. METHODS AND RESULTS: Mannheimia haemolytica strains OVI-1 and PH12296 were grown aerobically in two semi-defined media. In amino acid-limited cultures, the LKT concentration and yield in terms of biomass (Y(LKT/x)) were up to eightfold greater than in carbon-limited cultures. Supplementing amino acid-limited chemostat cultures with cysteine, glutamine, ferric iron and manganese further enhanced the Y(LKT/x) values up to threefold. Supplementation of an amino acid-limited batch culture of M. haemolytica strain OVI-1 with these nutrients resulted in an LKT concentration of 1.77 g l(-1) that was 45-fold greater than that obtained in RPMI 1640 medium. Aerobiosis enhanced LKT production. High acetic acid concentrations were produced under carbon-sufficient conditions. The highest maximum specific growth rates were recorded in the range of pH 6.8 to 7.8 and 37 to 40 degrees C. CONCLUSIONS: An amino acid-limited culture medium greatly improved LKT production in aerobic batch culture, which could be further enhanced by supplementation with cysteine, glutamine, ferric iron and manganese. SIGNIFICANCE AND IMPACT OF THE STUDY: It was demonstrated that LKT production by M. haemolytica could be dramatically increased through manipulation of the culture medium composition, which could benefit the production of LKT-based vaccines against bovine shipping fever pneumonia.

Serotyping and genotyping of HIV-1 infection in residents of Khayelitsha, Cape Town, South Africa.

It is estimated that between 5.5 and 6.1 million people are infected with HIV/acquired immunodeficiency syndrome (AIDS) in South Africa, with subtype C responsible for the majority of these infections. The Khayelitsha suburb of Cape Town has one of the highest HIV prevalence rates in South Africa. Overcrowding combined with unemployment and crime in parts of the area perpetuates high-risk sexual behavior, which increases exposure to infection by HIV. Against this background, the objective of this study was to characterize HIV-1 in residents confirmed to be seropositive. Serotyping was performed through a competitive enzyme-linked immunosorbent assay (cPEIA). Genotyping methods included RNA isolation followed by RT-PCR and sequencing of the gag p24, env gp41 immunodominant region (IDR), and env gp120 V3 genome regions of HIV-1. With the exception of a possible C/D recombinant strain, all HIV-1 strains were characterized as HIV-1 group M subtype C. One individual was shown to harbor multiple strains of HIV-1 subtype C. In Southern Africa, the focus has been to develop a subtype C candidate vaccine, as this is the major subtype found in this geographical area. Therefore, the spread of HIV-1 and its recombinant strains needs to be monitored closely.