Powerfactorverbetering in elektrische netwerken: pf - verbetering onder niet sinus-vormige omstandigheden

Een BacheloreindProject over het verbeteren van de powerfactor in elektrische netwerken. Door een groter aantal frequenties in de spanning óf door bepaalde componenten in de belasting is er een compenserend gedeelte in het netwerk nodig en / of mogelijk. Met welke schakelingen, componenten en karakteristieke waarden dit gedaan kan worden, zal per situatie verschillen

Model order reduction of CFFLs: Methods of model order reduction for (families of) Coherent Feedforward Loops

Biochemical reactions play a crucial role and tell us many about the behavior of the biological regulation processes . We will apply several methods of order reduction to describe the overall dynamics in a more compact way. For modelling a set of biochemical reactions is rewritten as first order differential equations. This set of first order differential equations defines the state space model. This rewriting is based on mass-action kinetics and Michaelis-Menten (MM) theory. With the Stoichiometry matrix the conservation laws and flux distribution in steady state can respectively be deduced. The systems we are looking at can be distinguished in many different biochemical regulatory networks . Examples of these networks can be found in gene expression, protein production and/or hormone production. The system that includes all given biochemical reactions of the network can be seen as a Coherent Feedforward Loop or CFFL. In synthetic biology these CFFLs are studied to gain insight into the desired production/expression: think about medicine production, agriculture and manufacturing. In biochemistry mostly a set of biochemical reactions can be given as a family or combination of CFFLs. To realize this a so called AND-gate or toehold switch is used.First of all we use conservation laws to reduce the system in order equal to the dimension of the left nullspace. Afterwards we have the option to reduce the system even more by applying the Quasi Steady State Approach in a given network like the CFFL. This method suggests that some species concentrations will reach its steady states much sooner than other species concentrations (if we look at slow timescale). Therefore it is assumed that some species already have their steady state at the beginning of the experiment. This is the so called classical QSSA. Another way to reduce the system order is by applying the Kron reduction order method. This method assumes a complexes network that reduces the complexes and thus the number of species. Here the concept of complex balancedness will determine whether the steady states for both models will be the same. Eventually we will also deal with alternative modelling where the cycles and feedback mechanisms will be replaced by more simple ones. Then afterwards mass-action kinetics along with classical QSSA can be applied. To get an optimal reduction order model the way in which parameters within the model are estimated can be discussed by optimization techniques. Furthermore we will see how the system can be transformed if we also have to do with in-and outflows. It actually means that we will need to add an extra term . One term will be in matrix-vector form while the other method merely uses vector-scalar notation. We will also look at the relation between these two forms. A future challenge would be to make an auto based system that directly converts the given system into its reduced order form. Here the best reduction order model will be selected automatically and applied in the best determinedsequence.Mechanical Engineering | Systems and Contro

Exploring Hawaiian long-term insular geodiversity dynamics

The role of time is underrepresented in assessments of geodiversity. Hot spot islands are unique systems to explore long-term geodiversity dynamics. The geodiversity dynamics of seven Hawaiian Islands are analysed by a qualitative-quantitative assessment using a geodiversity index. As input, freely available geological, soil and hydrological datasets are used, along with topographic diversity variables calculated from a digital elevation model. Long-term geodiversity dynamics were evaluated through correlation of island age to geodiversity class and assessment of the role of each contributing variable to the geodiversity class. The results indicate that high geodiversity is positively correlated with increasing island age, while younger islands generally correlate with low geodiversity classes. This is explained by the high contribution of topographic variables, and to a lesser extent by hydrological development and soil formation over time. These findings suggest that geodiversity dynamics play an important role in the life cycle of hot spot islands

Decreased hypothalamic thyrotropin-releasing hormone (TRH) gene expression in patients with nonthyroidal illness

Changes in hypothalamus-pituitary-thyroid function occur in patients with a variety of illnesses and are referred to as the euthyroid sick syndrome or nonthyroidal illness (NTI). In NTI, serum concentrations of T3 decrease to low, or even undetectable, levels without giving rise to elevated concentrations of TSH. We hypothesized that decreased activity of TRH-producing cells in the paraventricular nucleus (PVN) contributes to the persistence of low TSH levels. To test this hypothesis, we collected a series of formalin-fixed, paraffin-embedded hypothalami of patients whose plasma concentrations of T3, T4, and TSH had been measured in a blood sample taken less than 24 h before death. Quantitative TRH messenger RNA in situ hybridization (intraassay coefficient of variation: 13%) was performed in the PVN. Total TRH messenger RNA in the PVN showed a positive correlation with serum T3 (r = 0.66; P < 0.05) and with logTSH (r = 0.64; P < 0.05), but not with T4 (r = -0.02; P = 0.95). This is the first study to correlate premortem serum concentrations of thyroid hormones with postmortem gene expression of identified neurons in the human hypothalamus. The results suggest an important role for TRH cells in the pathogenesis of NT

Extrahypothalamic vasopressin and oxytocin in the human brain; presence of vasopressin cells in the bed nucleus of the stria terminalis

In the present study, the distribution of extrahypothalamic vasopressin (VP) and oxytocin (OXT) in the human brain was investigated by means of immunocytochemistry. In the septum verum, few VP fibers were found in the nucleus septalis lateralis and medialis (NSL and NSM), and in the bed nucleus of the anterior commissure. Very few VP and OXT fibers were present in the amygdala and in the hippocampus, mainly around the rostral tip of the lateral ventricle on the level of the pes hippocampi. The locus coeruleus (LC) contained dense networks of VP fibers and, although to a lesser extent, OXT fibers over its entire rostrocaudal extension. VP-immunoreactive neurons were present in the bed nucleus of the stria terminalis in a number of subjects, while no OXT cells were found in this structure. Thus, the VP innervation of limbic structures in the human brain, in particular of the NSL, was found to be clearly less pronounced than in the rat brain. The VP innervation of the LC, by contrast, was denser in the human brain than in the rat brain. No sex differences were found in the VP innervation of the human brain. These findings stress the need for caution in extrapolation of data concerning peptidergic innervation of the rat brain towards the human brai