Closed form solution of nonlinear oscillation of a cantilever beam using λ-symmetry linearization criteria.

A mechanical system, in general, undergoes vibrational motion when the system is subjected to a tension or an external force. One of the examples of such a system is a cantilever beam when it is exposed to a bending action. When the tension is released, the cantilever beam suffers from the oscillations until the strain energy is totally released through the damping characteristics of the cantilever beam. Depending on the stiffness and damping factors of the beam, the vibrational motion can be non-linear; in which case, the analytical solution becomes challenging formulating the flexural characteristics of the beam. Although numerical solution for the non-linear problem is possible, the analytical solution provides useful information between the mechanical response and the cantilever beam characteristics. In the present study, the analytical solution of the non-linear equations governing the motion of the cantilever beam is presented. The governing equation is linearized incorporating the Lie-Tresse linearization method. The closed form solution for the displacement of the cantilever beam is reduced to a linear solution after introducing the appropriate beam characteristics. The dynamic behavior of the flexural motion due to non-linear and linear cantilever beams are compared.

Effect of pycnogenol on ethanol-related oxidative retinal injury: an experimental study.

OBJECTIVE: We aimed at determining the protective effects of Pycnogenol on ethanol-induced retinotoxicity in an experimental model. MATERIALS AND METHODS: 30 male Wistar albino rats were randomly divided into three groups: an untreated healthy control (HC group), a group in which only ethanol was daily administered for six weeks (EtOH group), and a group in which ethanol + 40 mg/kg Pycnogenol was daily administered orally for six weeks (PEtOH group). The same volume (0.5 ml) of distilled water as solvent was applied in the same manner to the rats in the HC and EtOH groups. With the rats in the PEtOH and EtOH groups, 32% ethanol at a dose of 5 g/kg was administered by oral gavage one hour after the application of pycnogenol or distilled water. At the end of the experimental period, tissue samples were obtained for biochemical examination of malondialdehyde (MDA) and total glutathione (tGSH) levels, and afterwards, the eyes were removed for histopathological examination. RESULTS: Histopathological evaluations in the EtOH group showed significant destruction of retinal tissue with marked edema, decomposition and degeneration in layers, polymorphonuclear cell infiltration, dilatation and congestion in blood vessels. However, it was observed that MDA values increased and tGSH values decreased in the EtOH group. In the PEtOH group, MDA values decreased and GSH values increased. Again, degenerative changes were considerably less in this group. CONCLUSIONS: In the light of biochemical markers and histopathological evaluations, it was observed that ethanol exposure caused a significant degeneration in the retinal tissue. It was found that Pycnogenol administration significantly reduced the destructive effects seen histopathologically. Biochemical results also coincided with other findings. It was concluded that ethanol-induced rethytosis can be prevented to a large extent by Pycnogenol administration.

Protective effect of adenosine triphosphate against sunitinib-related skin damage in rats.

Cutaneous side effects associated with sunitinib use are a major problem in patients receiving cancer treatment. The aim of this study was to investigate the protective effect of adenosine triphosphate (ATP) against possible skin damage resulting from sunitinib use in rats. Thirty Albino Winstar rats were divided into the following three groups: healthy controls (HCs, n = 10), sunitinib (SUN, n = 10), and sunitinib + ATP (SAT, n = 10). ATP was injected intraperitoneally at a dose of 2 mg/kg. One hour subsequent to the administration of ATP and 0.9% NaCl, the SAT and SUN groups were orally administered a dose of 25 mg/kg sunitinib to the stomach. Macroscopic evaluation of the skin indicated lower levels of skin damage in the SAT group than in the SUN group. As an indicator of oxidative stress, malondialdehyde (MDA), total oxidant status (TOS), and oxidative stress index (OSI) levels were significantly higher in the SUN group than in the HC group, while total glutathione (tGSH) and total antioxidant status (TAS) levels were significantly lower. However, MDA, TOS, and OSI levels were significantly lower in the SAT group than in the SUN group, while tGSH and TAS levels were significantly higher. Histopathological examination revealed keratin plugs with edema, vasopathology, and inflammatory cell infiltration in the SUN group. The SAT group showed less necrotic epithelium, keratin plugs, edema, and vasopathology than the SUN group. ATP can be effective in preventing skin damage caused by sunitinib use by reducing oxidative stress.

The effect of adenosine triphosphate on sunitinib-induced cardiac injury in rats.

In this study, we aimed to show the effect of adenosine 5'-triphosphate (ATP) on sunitinib-induced cardiac injury in rats. The rats (n = 30) were divided equally into three groups as sunitinib group (SG), sunitinib plus ATP group (SAG), and healthy group (HG); 2 mg/kg ATP was injected intraperitoneally (ip) to the SAG group. Same volume normal saline as solvent was administered ip to the other two groups. After 1 h, 25 mg/kg sunitinib was applied orally via catheter to stomach in the SAG and SG groups. This procedure was repeated once daily for 5 weeks. At the end of this period, all animals were sacrificed and their cardiac tissue was removed. Malondialdehyde (MDA), total glutathione (tGSH), tumor necrosis factor α (TNF-α), and nuclear factor κB (NF-κB) levels in rats' cardiac tissues and troponin I (Tp-I) levels in rats' blood samples were evaluated. Histopathological analysis was also performed in cardiac tissues of the animals. MDA, TNF-α, NF-κB, and Tp-I levels were higher in the SG group compared to the SAG and HG groups (p < 0.001). tGSH levels of the SG group were lower than the SAG and HG groups (p < 0.001). The structure and morphology of cardiac muscle fibers and blood vessels were normal in the control group. In the SG group, obvious cardiac muscle tissue damage with dilated myofibers, locally atrophic myofibers, and congested blood vessels were observed. In the SAG group, marked amelioration in these findings was observed. We showed this for the first time that ATP administration exerts a protective effect against cardiac effects of sunitinib.