A validation of the quadriphasic mixture theory for intervertebral disc tissue

The swelling and shrinking behaviour of soft biological tissues is described by a quadriphasic mixture model. In this model four phases are distinguished: a charged solid, a fluid, cations and anions. A description of the set of coupled differential equations of this quadriphasic mixture model is given. These equations are solved by the finite element method using a weighted residual approach. The resulting non-linear integral equations are linearized and solved by the Newton-Raphson iteration procedure. We performed some confined swelling and compression experiments on intervertebral disc tissue. These experiments are simulated by a one-dimensional finite element implementation of this quadriphasic mixture model. In contrast to a triphasic mixture model, physically realistic diffusion coefficients can be used to fit the experiments when the fixed charge density is relatively large, because in the quadriphasic mixture model electrical phenomena are not neglected

Development of a micro-optofluidic temperature sensor

A fluorescent micro-optofluidic temperature sensor is developed using a temperature sensitive dye. The sensor can measure temperatures in microregions up to 70 ºC and is applicable in lab-on-a chip devices. It is fabricated using soft lithography method and uses Rhodamine B dissolved in water as a temperature indicator

Development of a micro-optofluidic temperature sensor

A fluorescent micro-optofluidic temperature sensor is developed using a temperature sensitive dye. The sensor can measure temperatures in microregions up to 70 ºC and is applicable in lab-on-a chip devices. It is fabricated using soft lithography method and uses Rhodamine B dissolved in water as a temperature indicator

A validation of the quadriphasic mixture theory for intervertebral disc tissue

The swelling and shrinking behaviour of soft biological tissues is described by a quadriphasic mixture model. In this model four phases are distinguished: a charged solid, a fluid, cations and anions. A description of the set of coupled differential equations of this quadriphasic mixture model is given. These equations are solved by the finite element method using a weighted residual approach. The resulting non-linear integral equations are linearized and solved by the Newton-Raphson iteration procedure. We performed some confined swelling and compression experiments on intervertebral disc tissue. These experiments are simulated by a one-dimensional finite element implementation of this quadriphasic mixture model. In contrast to a triphasic mixture model, physically realistic diffusion coefficients can be used to fit the experiments when the fixed charge density is relatively large, because in the quadriphasic mixture model electrical phenomena are not neglected

Quantification of individual polysulfides in lab-scale and full-scale desulfurisation bioreactors

Environmental pollution caused by the combustion of fuel sources containing inorganic and organic sulfur compounds such as hydrogen sulfide (H2S) and thiols, is a global issue as it leads to SO2 emissions. To remove H2S from gas streams such as liquefied petroleum gas (LPG), biological processes can be applied. In these processes, polysulfide anions (S-x(2-)) play a significant role as they enhance the dissolution of H2S and act as intermediates in the biological oxidation of hydrogen sulfide ions to elemental sulfur. Despite their important role, the distribution of the various polysulfide species in full-scale biodesulfurisation systems has not yet been reported. With conventionally applied spectrophotometric analysis it is only possible to determine the total concentration of S-x(2-). Moreover, this method is very sensitive to matrix effects. In this paper, we apply a method that relies on the derivatisation of S-x(2-) to dimethyl polysulfanes. Owing to the instability of higher dimethyl polysulfanes (Me2S4 to Me2S8), standards are not commercially available and had to be prepared by us. We present a simplified quantification method for higher dimethyl polysulfanes by calculating high performance liquid chromatogaphy (HPLC) UV response factors based on the addition of internal standards. The method was subsequently used to assess the distribution of polysulfide anions in both a laboratory-scale and a full-scale biodesulfurisation unit. We found that the average chain length of polysulfides strongly depends on the process conditions and a maximum of 5.33 sulfur atoms per polysulfide molecule was measured. Results of this study are required by mechanistic and kinetic models that attempt to describe product selectivity of sulfide oxidising bioreactors

Industrial applications of new sulphur biotechnology

The emission of sulphur compounds into the environment is undesirable because of their acidifying characteristics. The processing of sulphidic ores, oil refining and sulphuric acid production are major sources of SO2 emissions. Hydrogen sulphide is emitted into the environment as dissolved sulphide in wastewater or as H2S in natural gas, biogas, syngas or refinery gases. Waste streams containing sulphate are generated by many industries, including mining, metallurgical, pulp and paper and petrochemical industries. Applying process technologies that rely on the biological sulphur cycle can prevent environmental pollution. In nature sulphur compounds may cycle through a series of oxidation states (-2, 0, +2, +4, +6). Bacteria of a wide range of genera gain metabolic energy from either oxidising or reducing sulphur compounds. Paques B.V. develops and constructs reactor systems to remove sulphur compounds from aqueous and gaseous streams by utilising naturally occurring bacteria from the sulphur cycle. Due to the presence of sulphide, heavy metal removal is also achieved with very high removal efficiencies. Ten years of extensive laboratory and pilot plant research has, to date, resulted in the construction of over 30 full-scale installations. This paper presents key processes from the sulphur cycle and discusses recent developments about their application in industry

A validation of the quadriphasic mixture theory for intervertebral disc tissue

The swelling and shrinking behaviour of soft biological tissues is described by a quadriphasic mixture model. In this model four phases are distinguished: a charged solid, a fluid, cations and anions. A description of the set of coupled differential equations of this quadriphasic mixture model is given. These equations are solved by the finite element method using a weighted residual approach. The resulting non-linear integral equations are linearized and solved by the Newton-Raphson iteration procedure. We performed some confined swelling and compression experiments on intervertebral disc tissue. These experiments are simulated by a one-dimensional finite element implementation of this quadriphasic mixture model. In contrast to a triphasic mixture model, physically realistic diffusion coefficients can be used to fit the experiments when the fixed charge density is relatively large, because in the quadriphasic mixture model electrical phenomena are not neglected