A comparison was undertaken between two machines that utilise accelerated methods to measure oxidative stability: the Rancimat (Metrohm, Switzerland) and the single channel chemiluminescence instrument (ACL Instruments, Switzerland). The results from the machines showed good correlation for the measurement of the oxidation induction time of corn oil. For the ACL Instrument, the effect of the sample holder material (aluminium or borosilicate glass) was also investigated and clear differences were noted. Finally, a stability study was carried out over a period of 6 months, with corn oil, stored in the dark at three temperatures: ~4, ~27, ~40 °C and it was observed that it was possible to track subtle changes in oxidative stability using chemiluminescence.

Chemiluminescence (CL) includes all luminescence phenomena resulting from chemical reactions therefore due to the fact that the oxidative degradation process of the organics is combined with the emission of light this method can be applied for investigating the course of the oxidation processes. Commonly applied methods of the investigation of the oxidation such as determination of oxidation induction time (OIT) or oxidation onset temperature (OOT) using Differential Scanning Calorimetry (DSC) or other conventional thermoanalytical methods are sometimes unsuitable for long-term prediction of oxidative behaviour because of the use of elevated temperatures during these experiments: the high temperatures may invoke reaction pathways which are different from those encountered under the conditions of use. Compared to DSC and other conventional thermo-analytical methods, CL offers interesting advantages: due to its much higher sensitivity, experiments can be performed at much lower temperatures i.e. closer to the application related conditions. This fact is of the importance for the characterisation of substances with low temperature melting points, glass transitions, etc. The outstanding baseline stability of CL is of great benefit when performing long-term experiments; moreover, the CL-signal is related exclusively to the oxidation processes and therefore is not superposed by the signals resulting from the other reactions, including phase transitions. In the present study we report on a new approach of kinetic analysis of the oxidation reactions of natural rubbers with and without stabiliser in an oxygen atmosphere at moderate temperatures using CL measurements carried out on a newly-developed instrumentation. The kinetic parameters of the oxidation process, calculated from the chemiluminescence’s signals by means of the differential isoconversional method of Friedman, were subsequently applied for the simulation of the rubber aging under different temperature profiles.

The decomposition in HTPB bonded HMX was characterized with two highly sensitive methods: heat flow microcalorimetry (HFMC) and Chemiluminescence (CL). The material is stabilized with a phenolic antioxidant. The heat generation (HFMC) rate was determined from 120 to 150 °C using a TAM™ microcalorimeter and the oxidation of the substance was followed by the CL emission between 100 and 140 °C directly from the solid state sample. The end of antioxidant activity results in both measurements sets in characteristic changes in the curves. Kinetic parameters were calculated applying Arrhenius parameterization for the times to the end of antioxidant activity and by applying modelling with an autocatalytic model extended by a side reaction, which is assigned to the antioxidant consumption. The evaluation with the characteristic times gives good agreement between the two methods; the modelling represents the different but supplementing probing of the two measurement methods.

A common scepticism towards the application of many materials in art or in conservation-restoration results from the fact that their long-term stability is unknown and difficult to predict. In the present study we report on a new approach of kinetic analysis of the oxidation reactions of natural rubbers with and without stabiliser in an oxygen atmosphere at moderate temperatures using chemiluminescence measurements carried out on newly developed instrumentation. The kinetic parameters of the oxidation process, calculated from the chemiluminescence signals by means of the differential isoconversional method of Friedman, were subsequently applied to the simulation of the rubber aging using different temperature profiles. The results are a first step towards the use of chemiluminescence to characterise the oxidative aging of rubber and predicting the lifetime of rubber items.

A 75-year-old woman presented at an outside institution with cholestasis following a cholecystectomy procedure, which started laparoscopically but had to be switched to open surgery as a sealed perforation of the gallbladder was detected during the operation. Generally, the anatomical situation was described as very difficult.

Structured packings are used increasingly ia liquid-liquid extraction column. A new packing structure called OPTIFLOW is introduced for distillation and absorption processes. On the pilot plant scale, single drops were investigated and compared to other packing materials with respect to break-up, drop rise velocity and mass transfer.

In order to apply models describing mixing and transport phenomena in natural systems, data of a very specific nature are required. The programme of an investigation undertaken for more than 2 years in the River Neckar has been determined to a large extent by the concept of a model developed in parallel. Prerequisites for the collection of in situ data include a specially equipped boat, which permits the collection of data by means of various electrodes as well as by sampling. The continuous measuring equipment as well as the sampling device are supplied by a continuous flow of water pumped into the laboratory installed on the boat. Samples are either analysed there, in an accompanying field laboratory ashore, or in the central laboratory of the research institute. The overall geometry of river cross sections was recorded by an echograph. Mesures in situ du transport de matières en particules dans les rivières RESUME Pour la description des phénomènes de transport et mélange dans les eaux naturelles on a besoin de données de nature tout à fait spécifique. Depuis plus de deux ans on fait des expériences et des analyses dans le Neckar. Parallèlement on a mis au point un plan qui sert de base pour ces expériences. Pour recueiller des résultats sur place on a besoin d'un bateau spécial qui fournit les renseignements soit à l'aide de différentes électrodes soit par la prise d'échantillon. L'eau courante qu'on fait venir sans cesse au laboratoire du bateau approvisionne les appareils qui font des mesures sans interruption ainsi que les prises d'échantillon. C'est là ou à l'institut de recherche qu'on examine les prises d'échantillon. La géométrie de la coupe transversale des cours d'eau est enregistrée à l'aide d'un écho-sondeur.

The significant processes controlling the fate of particulates are convection an dispersion on one hand, and sedimentation on the other hand. Due to inteparticulated reactions, larger aggregates can be formed from smaller units thus changing the sedimentation characteristics. These phenomena are summarized in a mathematical model whereby hydrodynamic effects as well as the control mechanisms of the dissolved phase are included. A relationship was derived on the basis of energy considerations leading to the formulation of a critical sedimentation velocity of the suspensa, which determines the transport capacity of the flowing system. The sedimentation term is calculated from the above discussed transport capacity, hydro-dynamic parameters and suspending media properties. Aggregation effects are taken into account as an increase of sedimentation velocities of the particles. The equations are solved in a particular computational routine such that the horizontal distribution of suspended solids in a natural system can be describe as function of the above discussed phenomena. The model was tested with in situ-measurements. It was found that the observed processes are described satisfactorily by this model.