Thyroid cell growth: sphingomyelin metabolism as non-invasive marker for cell damage acquired during spaceflight

Prolonged spaceflights are known to elicit changes in human cardiovascular, musculoskeletal, and nervous systems, whose functions are regulated by the thyroid gland. It is known that sphingomyelin metabolism is involved in apoptosis (programmed cell death) of thyroid cells induced by UVC radiation, but at present no data exists with regard to this phenomenon, which occurs during space missions. The aim of this study was to analyze, for the first time, the effect of spaceflight on the enzymes of sphingomyelin metabolism, sphingomyelinase, and sphingomyelin synthase, and to determine whether the ratio between the two enzymes might be used as a possible marker for thyroid activity during space missions. Both quiescent thyroid cells and thyroid cells stimulated to proliferate with thyrotropin (TSH) were cultured during the Eneide and Esperia missions on the International Space Station. The results show that during space missions the cells treated with TSH grew only 1.5?±?0.65-fold and, thus, behave similarly to quiescent cells, while on the ground the same cells, maintained in experimental conditions that reproduced those of the flight, grew 7.71?±?0.67-fold. Comparison of the sphingomyelinase/sphingomyelin-synthase ratio and the levels of Bax, STAT3, and RNA polymerase II in proliferating, quiescent, pro-apoptotic, or apoptotic cells demonstrated that thyroid cells during space missions were induced into a pro-apoptotic state. Given its specificity and the small amount of cells needed for analysis, we propose the use of the sphingomyelinase/sphingomyelin-synthase ratio as a marker of functional status of thyroid cells during space missions. Further studies could lead to its use in real time during prolonged spaceflights.     

Landing system verification based on petri nets and a hybrid approach

One of the most important activities of control system design is its verification. Verification ensures that the controlled system will behave as expected under any circumstances it may operate. In this context, the purpose of this paper is to introduce a new method for the verification of aircraft control systems. The focus of this method is on aircraft systems that are characterized as hybrid, i.e., that merge continuous and discrete dynamics. The method proposed is divided into two main parts: the system modeling and the verification of behavioral properties. In the first part, Petri net, differential equation systems, and object oriented concepts are used concurrently in order to model complex hybrid systems. In the second part, the distributed nature of the model is explored in order to decompose a complex verification problem into series of simple local problems. Linear logic is used as a basis of a theorem-proving approach for the verification from the discrete-event point of view. The verification method has been applied to a number of case studies. Among them is the landing system of a military aircraft, which is described in this paper