The role of sodium silicate in newsprint deinking.

Thesis (M.Sc.)-University of Natal, Durban, 2003.Mondi Ltd. operates a deinking plant at its Merebank mill. The plant recycles 85 000 tons per annum of flat news and magazine to produce a furnish for its newsprint papermachines. A review of the relevant pulping and flotation chemistry literature revealed that the role played by sodium silicate appears to be multi-faceted and in some dispute. Sodium silicate has an undisputed role in pH buffering, hydrogen peroxide stabilisation and the prevention of fibre yellowing. However, its role in deinking is said to be that of an ink collector or alternatively an ink dispersant. The mill's own experience has shown that the sodium silicate plays a vital role in the deinking process. Sodium silicate's ability to disperse ink, both alone and in the presence of calcium ions and fatty acid soaps, was investigated using a model ink system. A representative newsprint ink base was dispersed in the laboratory under conditions similar to those encountered in a deinking pulper. The resultant dispersions were studied using turbidity and particle size analysis. The morphology of the ink particles was determined using a scanning electron microscope. Sodium silicate proved to be a poor disperser of ink particles, but nevertheless appeared to greatly influence the dispersing properties of the soap in the presence of calcium ions. The nature of the interactions between sodium silicate, calcium ions and the collector soap were studied in an attempt to elucidate the role of sodium silicate. A model system consisting of the sodium salt of collector soap, calcium ions and sodium silicate was studied under the conditions that prevail in a typical newsprint deinking pulper. It was found that the soap and the sodium silicate compete for the calcium ions, and sodium silicate showed a measurable chelating e:ffect on calcium ions. Thus, increasing levels of sodium silicate lead to an increase in the concentration of sodium soap in solution. It was hypothesised that this effect would lead to better dispersion of ink particles and improved deinking performance. This chelating effect was evaluated in laboratory deinking studies. Samples of newsprint were pulped in a 251 Lamort laboratory pulper under a variety of conditions, viz. with fresh water, with an excess of soap, with an excess of calcium, with and without sodium silicate. The pulps were floated in a 201 flotation cell. The brightness and colour of the unfloated and floated pulps were measured. The level of the final brightness after flotation was taken as a measure of deinking efficiency. The highest final brightness was achieved when there was an excess of sodium soap and a low Ca hardness in the pulper. Softening the water used in pulping without adding excess sodium soap did not significantly improve pulp brightness. The lowest final brightness occurred in the presence of an excess of calcium in the pulper. Calcium in the pulper in the presence of sodium silicate did not result in a significantly lower final brightness. The results support the hypothesis that sodium silicate sequesters the soluble calcium in a pulping system, thereby increasing the sodium soap concentration and the resultant deinking performance. Apart from sodium silicate's chief role as a peroxide stabiliser, the sequestering action on calcium appears to be its main mechanism of action in a deinking system. An appreciation of this role will facilitate the optimisation of deinking systems with respect to calcium hardness and silicate concentration. To this end it was recommended that the Merebank deinking plant should evaluate the use of water with a low calcium ion concentration and the addition of some soap into the pulper to improve their deinking plant performance

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Differences in lung function, bronchial hyperresponsiveness and respiratory health between elite athletes competing in different sports

The aim of this study was to examine lung function, bronchial hyperresponsiveness (BHR) and exercise-induced respiratory symptoms in elite athletes performing different sports. Norwegian national-team athletes (30 swimmers, 32 cross-country skiers, 16 speed-skaters, 11 rowers/paddlers, 17 handball players and 23 soccer players) completed a validated questionnaire, measured exhaled nitric oxide (FENO), spirometry, methacholine provocation (PD20met) and skin prick test. Three cut-off levels defined BHR; i.e. PD20met ≤2 µmol, ≤4 µmol and ≤8 µmol. Mean forced vital capacity (FVC) was highest in swimmers (Mean z-score[95%CI]  = 1.16 [0.80, 1.51]), and close to or higher than reference values according to the Global Lung Initiative equation, across all sports. Mean forced expiratory volume in 1 s (FEV1) was higher than reference values in swimmers (0.48 [0.13, 0.84]), and ball game athletes (0.69 [0.41, 0.97]). Mean forced expiratory flow between 25 and 75% of FVC (FEF25-75), and/or FEV1/FVC were lower than reference values in all endurance groups. BHR defined by ≤2 and ≤8 µmol methacholine was observed in respectively 50%–87% of swimmers, 25%–47% of cross-country skiers, 20%–53% of speed-skaters, 18%–36% of rowers/paddlers, and 0%–17% of the ball game athletes. Exercise-induced symptoms were common in all groups, most frequent in cross-country skiers (88%), swimmers (83%) and speed-skaters (81%).publishedVersio

Effects of formulation on the stability of green Cyclopia subternata extract during spray-drying and storage

Thesis (MSc Food Sc)--Stellenbosch University, 2016.ENGLISH ABSTRACT: Green Cyclopia subternata (honeybush) hot water extracts (GCSE) have potential as value-added functional food ingredients based on their anti-obesity and anti-diabetic properties. They are thus suitable for inclusion in reduced-kilojoule instant iced tea powder formulations. The aims of this study were to determine the effect of spray-drying, with and without carriers, on the stability of GCSE and the effect of product formulation and storage at different conditions on iced tea powder mixtures containing GCSE. GCSE was spray-dried without (control) and with added carriers, i.e. corn syrup solids (CS) and inulin (IN) at four treatment levels (0, 25, 50 and 75%). IN was selected for the final iced tea powder formulation due to its prebiotic properties, but solubility limited practical inclusion of IN in iced tea powder to levels of 25% (IN25). Six formulations (T1 = spray-dried GCSE; T2 = IN25; T3 = IN25 + sugar; T4 = IN25 + xylitol + stevia; T5 = T3 + citric acid + ascorbic acid; T6 = T4 + citric acid + ascorbic acid) were subjected to a six month shelf-life stability trial at ambient (25 °C/55% relative humidity (RH)) and accelerated (40 °C/75% RH) conditions. Physicochemical properties of the spray-dried and iced tea powders were characterised in terms of phenolic retention, moisture content (MC), water activity (aw), moisture sorption isotherms (MSI) and objective colour measurements. Isothermal microcalorimetry (IMC) was used to determine if the ingredients of mixtures interacted with one another and to assess the effect of raised RH conditions (25°C/55% RH and 40°C/75% RH) on the stability of the iced tea powders. Differential thermal analysis (DTA) was applied to measure the phase transition temperatures of the powders, X-ray powder diffraction (XRPD) measurements confirmed the crystalline or amorphous nature of the powders, and contact angle measurements indicated wettability of the powder. Spray-drying produced fine, light brown, amorphous and free-flowing powders. The MC and aw of the powders fell within the range of the monolayer moisture values calculated using the BET model from MSI data. IN and CS produced powders with similar characteristics and were compatible with GCSE, with the exception of mixtures containing 75% CS. Heating conditions during spray-drying had a negligible effect on the bioactive phenolic content and the free radical scavenging capacity of the extract. Therefore spray-drying was considered to be a suitable method of producing dried honeybush extracts. XRPD and DTA showed no significant phase transition for the iced tea powders during storage. IMC detected no incompatibilities between ingredients in the mixtures. Physicochemical characteristics of the powders remained stable and adequate phenolic retention was achieved at ambient temperature (25 °C). However, when the powders were stored at 40 °C, the presence of the acids caused drastic degradation of phenolic compounds and physicochemical changes resulting in prominent colour changes. IMC at 55% RH showed that amorphous powders (spray-dried extract and stevia) deliquesced. At 75% RH mixtures containing xylitol underwent deliquescence, while those with sugar remained stable. An iced tea powder containing GCSE should therefore be stored at ambient temperature in moisture impermeable packaging to ensure adequate stability.AFRIKAANSE OPSOMMING: Groen Cyclopia subternata warm water ekstrakte (GCSE) het potensiaal as waarde-toegevoegde funksionele voedsel bestandele gebaseer op hul anti-vetsug en anti-diabetiese eienskappe. Sulke ekstrakte is dus geskik om in ‘n verminderde-kilojoule kits-ystee poeier formulasie gebruik te word. Die doelstellings van hierdie studie was om die effek van sproeidroging, met en sonder draers, op die stabiliteit van GCSE te bepaal, asook die effek van produk formulasie en opberging by verskillende toestande op ystee-mengsels wat GCSE bevat te bestudeer. GCSE is gesproeidroog sonder (kontrole) en met draers, d.i. mieliestroop-vastestowwe (MS) en inulin (IN) teen vier behandelingsvlakke (0, 25, 50 en 75%). IN is gekies vir die finale poeier ystee formulasie weens sy pre-biotiese eienskappe maar oplosbaarheid het die byvoeging van IN in ystee-poeier beperk tot 25% (IN25). Ses formulasies (T1 = gesproeidroogde GCSE; T2 = IN25; T3 = IN25 + suiker; T4 = IN25 + xylitol + stevia; T5 = T3 + sitroensuur + askorbiensuur; T6 = T4 + sitroensuur + askorbiensuur) is onderwerp aan ‘n ses maande rakleeftyd studie by normale (25 °C/55% relatiewe humiditeit (RH)) en versnelde (40 °C/75%RH) opbergings toestande. Die fisies-chemiese eienskappe van die gesproeidroogde en ystee-poeiers is gekarakteriseer in terme van fenoliese behoud, voginhoud (VI), water aktiwiteit (aw), vog-sorpsie-isoterme (VSI) en objektiewe kleur metings. Isotermiese mikrokalorimetrie (IMK) is gebruik om te bereken of daar interaksie is tussen die bestandele van die mengsels, en om die uitwerking van opberging RH toestande (25 °C/55% RH en 40 °C/75% RH) op die stabiliteit van ystee-poeiers te bepaal. Differensiële termiese analiese (DTA) is gebruik om die fase oorgangs temperature van die poeiers te bepaal, X-straal poeier diffraksie (XRPD) meetings het die kristal- of amorfe-karaktereienskappe van die poeiers bevestig, en kontak-hoek metings het die benatingspotesiaal van die poeier aangedui. Sproeidroging het fyn, ligte-bruin, amorfe en vry-bewegende poeiers geproduseer. Die VI en aw van die poeiers was in die omvang van die monolaag voginhoud waardes, soos bereken met die BET model van die VSI data. IN en MS het poeiers met soortgelyke eienskappe opgelewer en het nie interaksie met GCSE getoon nie, behalwe in geval van mengsels met 75% MS. Die verhittingskondisies gedurende sproeidroging het ‘n minimale effek op die bioaktiewe phenoliese-inhoud en die vryradikaal blussings vermoë van die ektrak gehad. Daarom is sproeidroging aanvaar as ‘n effektiewe manier om gedroogde heuningbostee ekstrakte te vervaardig. XRPD en DTA het geen verskille in die fase oorgangs van ystee-poeiers gedurende opberging getoon nie, terwyl IMK het geen interaksie tussen bestandele van die mengsels getoon het nie. Die Stellenbosch University https://scholar.sun.ac.za v fisies-chemiese eienskappe van poeiers was stabiel en aanvaarbaare behoud van fenoliese verbindings is behaal by kamertemperatuur (25 °C). Opberging by 40 °C het egter getoon dat die sure drastiese afbreking van die fenoliese verbindings asook fisies-chemiese veranderinge veroorsaak. Die fisies-chemieses veranderings het kleur veranderings veroorsaak. IMK teen 55% RH het bewys dat amorfepoeiers (gesproei-droogde ekstrak en stevia) het vloiebaar geword. By 75% RH het die mengsels met xylitol ook vloeibaar geword, terwyl die met suiker stabiel gebly het. ‘n Ystee-poeier met GCSE moet dus by kamertemperatuur en in vog-ondeurlaatbare verpakking opgeberg word om stabiel te bly

Neural network modelling and prediction of the flotation deinking behaviour of complex recycled paper mixes.

Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2011.In the absence of any significant legislation, paper recycling in South Africa has grown to a respectable recovery rate of 43% in 2008, driven mainly by the major paper manufacturers. Recently introduced legislation will further boost the recovery rate of recycled paper. Domestic household waste represents the major remaining source of recycled paper. This source will introduce greater variability into the paper streams entering the recycling mills, which will result in greater process variability and operating difficulties. This process variability manifests itself as lower average brightness or increased bleaching costs. Deinking plants will require new techniques to adapt to the increasingly uncertain composition of incoming recycled paper streams. As a developing country, South Africa is still showing growth in the publication paper and hygiene paper markets, for which recycled fibre is an important source of raw material. General deinking conditions pertaining to the South African tissue and newsprint deinking industry were obtained through field surveys of the local industry and assessment of the current and future requirements for deinking of differing quality materials. A large number of operating parameters ranging from waste mixes, process variables and process chemical additions, typically affect the recycled paper deinking process. In this study, typical newsprint and fine paper deinking processes were investigated using the techniques of experimental design to determine the relative effects of process chemical additions, pH, pulping and flotation times, pulping and flotation consistencies and pulping and flotation temperatures on the final deinked pulp properties. Samples of recycled newsprint, magazines and fine papers were pulped and deinked by flotation in the laboratory. Handsheets were formed and the brightness, residual ink concentration and the yield were measured. It was determined that the type of recycled paper had the greatest influence on final brightness, followed by bleaching conditions, flotation cell residence time and flotation consistency. The residual ink concentration and yield were largely determined by residence time and consistency in the flotation cell. The laboratory data generated was used to train artificial neural networks which described the laboratory data as a multi-dimensional mathematical model. It was found that regressions of approximately 0.95, 0.84 and 0.72 were obtained for brightness, residual ink concentration and yield respectively. Actual process data from three different deinking plants manufacturing seven different grades of recycled pulp was gathered. The data was aligned to the laboratory conditions to take into account the different process layouts and efficiencies and to compensate for the differences between laboratory and plant performance. This data was used to validate the neural networks and select the models which best described the overall deinking performances across all of the plants. It was found that the brightness and residual ink concentration could be predicted in a commercial operation with correlations in excess of 0.9. Lower correlations of ca. 0.5 were obtained for yield. It is intended to use the data and models to develop a predictive model to facilitate the management and optimization of a commercial flotation deinking processes with respect to waste input and process conditions

Business as usual -small and micro enterprise support versus traditional business practices in Western Namibia

Magister Artium (Development Studies) - MA(DVS)This research describes the current situation of small and micro enterprises (SME) in Western Namibia, its problems and constraints, but also its potential for growth and its capacity for absorption of the unemployed particularly in the informal sector. The thesis addresses a set of problems, especially regarding research in the region, impact of apartheid rule on SMEs as well as lack of business acumen on micro level and the new government SME support strategy which is ignoring traditional differences in business practices on macro level

Unveiling the Dark Side of Fintech: Challenges and Breaches in Protecting User Data in Indonesia’s Online Loan Service

he rapid evolution of information and communication technology has driven diverse business and financial practices. Indonesia is at the forefront with high engagement in fintech online lending services, presenting challenges in safeguarding user data despite these platforms' convenience. This research aims to analyze the intricacies of protecting the personal data of users of online lending services in Indonesia and highlight the obstacles faced in this process. Using a normative legal approach combined with descriptive data analysis, this research examines the protection mechanism from the perspectives of users and online loan service providers. The research concluded that users should verify the legitimacy of online loan service providers by ensuring proper registration with the Financial Services Authority (OJK) of the Republic of Indonesia. In addition, users should carefully scrutinize and understand the terms and conditions of personal data protection before agreeing to an online loan agreement. Second, the main problems qualified as obstacles in this research related to the effectiveness of personal data protection in the context of online lending are at least influenced by three main elements that influence each other, especially those related to legal substance, legal structure, and legal culture. Based on this doctrine, it is found that in addition to legal uncertainty related to the guarantee of personal data protection rights on the one hand, on the other hand, the absence of specialized institutions related to personal data protection is one of the factors that affect the ineffectiveness of personal data protection in Indonesia related to online loans

Effect of interchain coupling on conducting polymer luminescence: excimers in derivatives of poly(phenylene vinylene)

Optical excitation of a chain in a polymer film may result in formation of an excimer, a superposition of on-chain excitons and charge-transfer excitons on the originally excited chain and a neighboring chain. The excimer emission is red-shifted compared to that of an on-chain exciton by an amount depending on the interchain coupling $t_\perp$. Setting up the excimer wavefunction and calculating the red shift, we determine average $t_\perp$ values, referred to a monomer, of 0.52 eV and 0.16 eV for poly(2,5-hexyloxy $p$-phenylene cyanovinylene), CN-PPV, and poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-1, 4 p-phenylene vinylene], MEH-PPV, respectively, and use them to determine the effect of interchain distance on the emission.Comment: 10 pages, RevTeX, 1 PS figure, replaced version of cond-mat/9707095, accepted for publication in Phys. Rev. B, Rapid Communicatio

Identification of microRNA-mRNA functional interactions in UVB-induced senescence of human diploid fibroblasts

BACKGROUND: Cellular senescence can be induced by a variety of extrinsic stimuli, and sustained exposure to sunlight is a key factor in photoaging of the skin. Accordingly, irradiation of skin fibroblasts by UVB light triggers cellular senescence, which is thought to contribute to extrinsic skin aging, although molecular mechanisms are incompletely understood. Here, we addressed molecular mechanisms underlying UVB induced senescence of human diploid fibroblasts. RESULTS: We observed a parallel activation of the p53/p21(WAF1) and p16(INK4a)/pRb pathways. Using genome-wide transcriptome analysis, we identified a transcriptional signature of UVB-induced senescence that was conserved in three independent strains of human diploid fibroblasts (HDF) from skin. In parallel, a comprehensive screen for microRNAs regulated during UVB-induced senescence was performed which identified five microRNAs that are significantly regulated during the process. Bioinformatic analysis of miRNA-mRNA networks was performed to identify new functional mRNA targets with high confidence for miR-15a, miR-20a, miR-20b, miR-93, and miR-101. Already known targets of these miRNAs were identified in each case, validating the approach. Several new targets were identified for all of these miRNAs, with the potential to provide new insight in the process of UVB-induced senescence at a genome-wide level. Subsequent analysis was focused on miR-101 and its putative target gene Ezh2. We confirmed that Ezh2 is regulated by miR-101 in human fibroblasts, and found that both overexpression of miR-101 and downregulation of Ezh2 independently induce senescence in the absence of UVB irradiation. However, the downregulation of miR-101 was not sufficient to block the phenotype of UVB-induced senescence, suggesting that other UVB-induced processes induce the senescence response in a pathway redundant with upregulation of miR-101. CONCLUSION: We performed a comprehensive screen for UVB-regulated microRNAs in human diploid fibroblasts, and identified a network of miRNA-mRNA interactions mediating UVB-induced senescence. In addition, miR-101 and Ezh2 were identified as key players in UVB-induced senescence of HDF