Mehatronički sistemi traktora u funkciji savremene poljoprivredne proizvodnje

In past few decades significant changes happened in the field of technological development of agricultural tractors, leading to great improvements in different aspects of their operation. This is enabled, above all, by introducing of electronic control systems and their wide application in different systems of the tractor. Due to these changes, agricultural tractor has evolved from rough and robust heavy duty machine to high-tech system capable of executing fully new functions and achieving much higher level of overall working results. A several main examples can be named, such as greater energy efficiency, lower emission, greater quality of agro-technical operations, better soil protection and enhanced working conditions for human operator. New technologies, whose application has led to achieved results, are mostly based on mechatronic systems. This paper will give a basic overview of current achievements and discuss possibilities for future development, mainly focused on the tractor as mobile machine i.e. vehicle.U novije vreme došlo je do intenzivnih prodora u području tehnološkog razvoja poljoprivrednih traktora, što je dovelo do značajnih poboljšanja u svim aspektima njihove upotrebe. Dostignuti nivo razvoja u najvećoj meri omogućilo je uvođenje sistema elektronskog upravljanja i njihova široka primena na različitim sistemima traktora. Zahvaljujući ovim unapređenjima, traktor je od prvobitno relativno jednostavne i robusne mašine evoluirao u sofisticirani mobilni sistem visoke tehnologije sposoban za izvođenje potpuno novih funkcija i dostizanje znatno višeg nivoa sveukupnih rezultata rada. Ukratko se može navesti nekoliko najvažnijih primera, kao što su poboljšanje energetske efikasnosti, bolja zaštita zemljišta i okoline, povećanje produktivnosti i unapređenje kvaliteta agrotehničkih operacija, poboljšanje uslova rada rukovaoca itd. Nove tehnologije, čija primena je dovela do navedenih rezultata, pre svega su bazirane na mehatroničkim sistemima. U radu je, na osnovu istraživanja aktuelne literature, dat prikaz trenutnih dostignuća i pravaca istraživanja, i diskutovane mogućnosti daljeg razvoja. Zbog obimnosti tematike, rad je fokusiran prvenstveno na sam traktor kao mobilni sistem

Representation and similarity: Suarez on necessary and sufficient conditions of scientific representation

The notion of scientific representation plays a central role in current debates on modeling in the sciences. One or maybe the major epistemic virtue of successful models is their capacity to adequately represent specific phenomena or target systems. According to similarity views of scientific representation, models should be similar to their corresponding targets in order to represent them. In this paper, Suarez’s arguments against similarity views of representation will be scrutinized. The upshot is that the intuition that scientific representation involves similarity is not refuted by the arguments. The arguments do not make the case for the strong claim that similarity between vehicles and targets is neither necessary nor sufficient for scientific representation. Especially, one claim that a similarity view wants to uphold, still, is the following thesis: only if a vehicle is similar to a target in relevant respects and to a specific degree of similarity then the vehicle is a scientific representation of that target.Ethics & Philosophy of Technolog

Role of microRNA-23b in flow-regulation of Rb phosphorylation and endothelial cell growth

MicroRNAs (miRs) can regulate many cellular functions, but their roles in regulating responses of vascular endothelial cells (ECs) to mechanical stimuli remain unexplored. We hypothesize that the physiological responses of ECs are regulated by not only mRNA and protein signaling networks, but also expression of the corresponding miRs. EC growth arrest induced by pulsatile shear (PS) flow is an important feature for flow regulation of ECs. miR profiling showed that 21 miRs are differentially expressed (8 up- and 13 downregulated) in response to 24-h PS as compared to static condition (ST). The mRNA expression profile indicates EC growth arrest under 24-h PS. Analysis of differentially expressed miRs yielded 68 predicted mRNA targets that overlapped with results of microarray mRNA profiling. Functional analysis of miR profile indicates that the cell cycle network is highly regulated. The upregulation of miR-23b and miR-27b was found to correlate with the PS-induced EC growth arrest. Inhibition of miR-23b using antagomir-23b oligonucleotide (AM23b) reversed the PS-induced E2F1 reduction and retinoblastoma (Rb) hypophosphorylation and attenuated the PS-induced G1/G0 arrest. Antagomir AM27b regulated E2F1 expression, but did not affect Rb and growth arrest. Our findings indicate that PS suppresses EC proliferation through the regulation of miR-23b and provide insights into the role of miRs in mechanotransduction