Activation energies as the validity criterion of a model for complex reactions that can be in oscillatory states

Modeling of any complex reaction system is a difficult task. If the system under examination can be in various oscillatory dynamic states, the apparent activation energies corresponding to different pathways may be of crucial importance for this purpose. In that case the activation energies can be determined by means of the main characteristics of an oscillatory process such as pre-oscillatory period, duration of the oscillatory period, the period from the beginning of the process to the end of the last oscillation, number of oscillations and others. All is illustrated on the Bray-Liebhafsky oscillatory reaction

Interpolatory Weighted-H2 Model Reduction

This paper introduces an interpolation framework for the weighted-H2 model reduction problem. We obtain a new representation of the weighted-H2 norm of SISO systems that provides new interpolatory first order necessary conditions for an optimal reduced-order model. The H2 norm representation also provides an error expression that motivates a new weighted-H2 model reduction algorithm. Several numerical examples illustrate the effectiveness of the proposed approach

Determination of phthalates in plum spirit and their occurrence during plum spirit production

Phthalates are ubiquitous environmental contaminants that, due to their lipophilicity, migrate more readily into beverages with higher ethanol content. The aim of this work was to study the occurrence of phthalates in samples during the plum spirit production and in the final product, plum spirit manufactured by registered producers from five European countries, using gas chromatography-mass spectrometry (GC-MS). A decreasing trend of mean values was observed for diethyl phthalate (DEP), di-iso-butyl phthalate (DiBP), and di-n-butyl phthalate (DBP) as the distillation process went on. Levels of benzyl-butyl phthalate (BBP) and di-(2-ethylhexyl) phthalate (DEHP) increased in the distillation phase compared to concentrations in the preceding phases. In commercial plum spirits, DEHP and DiBP were detected in the highest concentrations. Results also indicated that a moderate daily consumption of plum spirit does not pose a health risk regarding the Tolerable Daily Intake of BBP, DEHP, and DB

Influence of arginine vasopressin on the ultradian dynamics of Hypothalamic-Pituitary-Adrenal axis

Numerous studies on humans and animals have indicated that the corticotrophin-releasing hormone (CRH) and arginine vasopressin (AVP) stimulate both individually and synergistically secretion of adrenocorticotropic hormone (ACTH) by corticotropic cells in anterior pituitary. With aim to characterize and better comprehend the mechanisms underlying the effects of AVP on Hypothalamic-Pituitary-Adrenal (HPA) axis ultradian dynamics, AVP is here incorporated into our previously proposed stoichiometric model of HPA axis in humans. This extended nonlinear network reaction model took into account AVP by: reaction steps associated with two separate inflows of AVP into pituitary portal system, that is synthesized and released from hypothalamic parvocellular and magnocellular neuronal populations, as well as summarized reaction steps related to its individual and synergistic action with CRH on corticotropic cells. To explore the properties of extended model and its capacity to emulate the effects of AVP, nonlinear dynamical systems theory and bifurcation analyses based on numerical simulations were utilized to determine the dependence of ultradian oscillations on rate constants of the inflows of CRH and AVP from parvocellular neuronal populations, the conditions under which dynamical transitions occur due to their synergistic action and, moreover, the types of these transitions. The results show that under certain conditions, HPA system could enter into oscillatory dynamic states from stable steady state and vice versa under the influence of synergy reaction rate constant. Transitions between these dynamical states were always through supercritical Andronov-Hopf bifurcation point. Also, results revealed the conditions under which amplitudes of ultradian oscillations could increase several-fold due to CRH and AVP synergistic stimulation of ACTH secretion in accordance with results reported in the literature. Moreover, results showed experimentally observed superiority of CRH as a stimulator of ACTH secretion compared to AVP in humans. The proposed model can be very useful in studies related to the role of AVP and its synergistic action with CRH in life-threatening circumstances such as acute homeostasis dynamic crisis, autoimmune inflammations or severe hypovolemia requiring instant or several-days sustained corticosteroid excess levels. Moreover, the model can be helpful for investigations of indirect AVP-induced HPA activity by exogenously administered AVP used in therapeutic treatment

Probir na oštećenje sluha u predškolskoj/školskoj dobi

Komunikativne vještine u ranoj dječjoj dobi presudne su za zdravlje, edukaciju, odabir zanimanja i kvalitetu života. Pretpostavka za njihov razvoj je uredan sluh. Rana detekcija oštećenja sluha, putem probira, dovodi do povoljnih ishoda liječenja i rehabilitacije. U Europskoj uniji je u tijeku EUscreen vision&hearing projekt, u kojem sudjeluje i Hrvatska. Cilj studije je usporediti probir na oštećenje vida i sluha u svim zemljama Europske unije i izraditi priručnik, u kojem će se predložiti učinkoviti model, poštujući specifičnosti svake zemlje. U Hrvatskoj je, među prvima u Europi, 2002. godine započeo sveobuhvatni probir novorođenčadi na oštećenje sluha (SPNOS), koji se od 2005. godine provodi u svim rodilištima po istom protokolu, a koji nam omogućuje rano otkrivanje prirođenih i perinatalnih oštećenja. Prevalencija oštećenja sluha kod djece raste s dobi, te djeca s progresivnim, stečenim i oštećenjima s kasnijim početkom, ako nisu prepoznata, ulaze u obrazovni sustav s ozbiljnim deficitom. On se može manifestirati u jezičnim poremećajima, otežanom usvajanju čitanja i pisanja, poremećajima socio-emocionalnog razvoja, problemima u pažnji i ponašanju. Za sada u Hrvatskoj nije na nacionalnoj razini organiziran sveobuhvatni probir u predškolskoj dobi, već se provodi u 6. ili 7. razredu osnovne škole, prije opredjeljenja za odabir profesije. Preporučuje se poboljšanje postojećeg modela uvođenjem probira na oštećenje sluha prije početka obrazovanja, neposredno prije upisa u školu ili tijekom prvog razreda, “screening” tonskom audiometrijom od strane timova školske medicine. Predlaže se način izrade postupnika za provođenje probira, koji će uključiti i stvaranje baze podataka i način praćenja rezultata