The Brix-Free water capacity and sorption behaviour of fibre components of sugar cane (Saccharum officinarum).

Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2008.Milling data from sugar factories in Mauritius were examined from 1960 to 2004 to assess the trend in the quality of cane received at mills and the change in factory performance. A deterioration in overall quality was apparent due to the increased level of extraneous matter delivered in the cane supply. Comparison was made with available data from other countries in the world, notably those of South Africa and Australia. Controlled addition of extraneous matter to clean cane was effected under laboratory conditions to determine the relative impact of dry leaves, green leaves and cane tops on the quality of cane and the resulting juice, and to predict through derived equations, their impact on cane processing. The addition of dry leaves was found to have the most adverse effect followed by green leaves and cane tops. In the case of dry leaf addition to cane the detrimental effects were found to be masked by an increase in the concentration of solutes in the juice extracted. This phenomenon was thought to be due to the selective sorption of water (so-called Brix-free water) by dry leaves. To test this assertion, the sugar cane stalks of four different cane varieties aged 52, 44 and 36 weeks were separated into their component parts by means of a method devised in this work. There were nine component parts: stalk fibre, stalk pith, rind fibre, rind fines, top fibre, dry leaf fibre, dry leaf fines, green leaf fibre and green leaf fines which, on characterisation by Fourier transform infrared spectroscopy and scanning electron microscopy, were very similar except that stalk pith was more flaky and had a higher surface area than the others. Various analytical techniques were tested for the determination of Brix-free water. The most convenient method proved to be a refractometric method which was improved so as to be applicable to the wide range of cane components fibres studied. Statistical analysis of the Brix-free water content of the separated samples showed that when the combined effect of fibre and pith in the cane stalk of three ages was considered, the four cane varieties were not different. This was not the case for dry leaf, green leaf, top and rind. Of the nine cane components, stalk pith exhibited the highest Brix-free water value of about 20 g/100 g fibre, whereas all the other components exhibited values of about 15 g/100 g fibre, which are much lower than the traditionally accepted value of 25% for cane. The latter was found to be the fibre saturation point of bound water determined at 20 oC, which is the sum of dissolved and hydrated waters, and which is normally greater than the Brix-free water value as determined in this work. The water sorption characteristics of the various cane component parts were further investigated by making measurements to determine the equilibrium moisture contents at various water activity values. These data were used to construct adsorption isotherms. These were fitted to 17 existing isotherm models, of which two, namely, the Hailwood-Horrobin and Guggenheim-Anderson-de Boer models, gave the best fit. The sorbed water was subsequently characterised in terms of various parameters, namely, the monolayer moisture content, the number of adsorbed monolayers, the percentage of bound water, the total surface area for hydrophilic binding, the heats of sorption of the monolayer and multilayers, the net and total isosteric heats of sorption and the entropy of sorption. From the monolayer moisture content and the amount of “hydrated water” as calculated from the Hailwood-Horrobin model, it is clear that at EMC values between 0 and 5% (aw = 0 – 0.3), the non-freezable water is tightly bound to the surface of the fibre. The second region starts at EMC values from 5% to 10 – 15% (aw = 0.3 to 0.6 – 0.8) depending on the cane components, and the bound water in this region is termed the freezable water. The third type of water is essentially free water, it exists after the second region and ends at EMC values of about 25%. From this study, it is apparent that the Brix-free water as measured in this work measures the amount of water bound in the first two regions

Aspergillus fumigatus Specificities as Deduced from Comparative Genomics

International audienc

Analysing How People Orient to and Spread Rumours in Social Media by Looking at Conversational Threads

AbstractAs breaking news unfolds people increasingly rely on social media to stay abreast of the latestupdates. The use of social media in such situations comes with the caveat that newinformation being released piecemeal may encourage rumours, many of which remainunverified long after their point of release. Little is known, however, about the dynamics ofthe life cycle of a social media rumour. In this paper we present a methodology that hasenabled us to collect, identify and annotate a dataset of 330 rumour threads (4,842 tweets)associated with 9 newsworthy events. We analyse this dataset to understand how usersspread, support, or deny rumours that are later proven true or false, by distinguishing twolevels of status in a rumour life cycle i.e., before and after its veracity status is resolved. Theidentification of rumours associated with each event, as well as the tweet that resolved eachrumour as true or false, was performed by journalist members of the research team whotracked the events in real time. Our study shows that rumours that are ultimately proven truetend to be resolved faster than those that turn out to be false. Whilst one can readily seeusers denying rumours once they have been debunked, users appear to be less capable ofdistinguishing true from false rumours when their veracity remains in question. In fact, weshow that the prevalent tendency for users is to support every unverified rumour. We alsoanalyse the role of different types of users, finding that highly reputable users such as newsorganisations endeavour to post well-grounded statements, which appear to be certain andaccompanied by evidence. Nevertheless, these often prove to be unverified pieces of informationthat give rise to false rumours. Our study reinforces the need for developing robustmachine learning techniques that can provide assistance in real time for assessing theveracity of rumours. The findings of our study provide useful insights for achieving this aim

Analysis of discussion around rumours.

<p>Z-score values for the amount of discussion generated by different rumours, representing the extent to which different rumours spark discussion below or above the overall average. Red corresponds to false rumours, green to true rumours and yellow to unverified rumours.</p

Annotation structure.

<p>Diagram showing the structure resulting from the journalists’ annotation work. Rumour stories, represented by squares, can be one of true (green), false (red), or unverified (orange). Each of the rumour stories has a number of rumour threads associated with it (black lines). When a story is true or false, the journalists also picked, where available, one tweet as the resolving tweet within the story’s timeline.</p

Rumour resolution delays.

<p>Distribution of delays (in hours) in resolving false (red) and true (green) rumours. Horizontal lines represent 25, 50, and 75 percentiles.</p