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In the present work, molecular dynamics simulations were used to investigate the impact of the tool microstructure on the wear behavior of ferrite workpiece during nanoscratching. The tool microstructure was modified by varying the carbide (cementite) contents. The simulation results show that dislocations are the primary mechanism for plastic deformation of the workpiece material. It is found that total dislocation length varies significantly depending on the carbide content in the tool. Furthermore, other tribological phenomena were also observed to depend on the carbide contents. For example, the average value of frictional forces decreased while the normal force increases with increasing carbide contents, and hence the friction coefficient was decreased. Additionally, the shape and size of lateral and frontal pileups are lowered. The structural analysis of the pileup region reveals the loss of long range order and start of amorphisation. The temperature distribution of the pileup regions showed an increase of the pileup temperature when carbide is added into tool. The wear volume is considerably reduced when the carbide content increases. The average scratch hardness was found to decrease and the result was analyzed with the theoretical Taylor hardening model.

Curcumin exhibits anti-cancer properties manifested by activation of pro-apoptotic signaling. We have demonstrated earlier that apoptosis of HL-60 human leukemia cells induced by curcumin is controlled by ceramide generated by neutral sphingomyelinase (nSMase) which contributes to sphingomyelin synthase (SMS) inhibition favoring accumulation of ceramide in cells. Here we report that the activity of nSMase, ceramide accumulation and death of HL-60 cells are inhibited by overexpression of Bcl-xL or Bcl-2 proteins, while down-regulation of nSMase interferes with degradation of Bcl-2 but not Bcl-xL. Activation of nSMase in curcumin-treated cells requires the activity of apoptosis initiator caspase-8 and executioner caspase-3, whereas nSMase depletion prevents activation of caspase-3, but not caspase-8. These data place nSMase activation downstream of caspase-8 and Bcl-xL and indicate a mutual regulation between nSMase and caspase-3 activity on one hand, and Bcl-2 level on the other hand in curcumin-treated cells. The activation of nSMase and ceramide accumulation also depended on the depletion of glutathione. The depletion of glutathione required the activity of caspase-8 and caspase-3 as well as the down-regulation of Bcl-2 and Bcl-xL. Together, the data indicate a crosstalk among Bcl-2, Bc-xL, caspases and glutathione during curcumin-induced apoptosis and point to the superior role of caspase-8 activity, Bcl-xL down-regulation and glutathione depletion in the pro-apoptotic cascade leading to nSMase activation and generation of ceramide.

Curcumin exhibits anti-cancer properties manifested by activation of pro-apoptotic signaling. We have demonstrated earlier that apoptosis of HL-60 human leukemia cells induced by curcumin is controlled by ceramide generated by neutral sphingomyelinase (nSMase) which contributes to sphingomyelin synthase (SMS) inhibition favoring accumulation of ceramide in cells. Here we report that the activity of nSMase, ceramide accumulation and death of HL-60 cells are inhibited by overexpression of Bcl-xL or Bcl-2 proteins, while down-regulation of nSMase interferes with degradation of Bcl-2 but not Bcl-xL. Activation of nSMase in curcumin-treated cells requires the activity of apoptosis initiator caspase-8 and executioner caspase-3, whereas nSMase depletion prevents activation of caspase-3, but not caspase-8. These data place nSMase activation downstream of caspase-8 and Bcl-xL and indicate a mutual regulation between nSMase and caspase-3 activity on one hand, and Bcl-2 level on the other hand in curcumin-treated cells. The activation of nSMase and ceramide accumulation also depended on the depletion of glutathione. The depletion of glutathione required the activity of caspase-8 and caspase-3 as well as the down-regulation of Bcl-2 and Bcl-xL. Together, the data indicate a crosstalk among Bcl-2, Bc-xL, caspases and glutathione during curcumin-induced apoptosis and point to the superior role of caspase-8 activity, Bcl-xL down-regulation and glutathione depletion in the pro-apoptotic cascade leading to nSMase activation and generation of ceramide.

Abstract In the present study two species were selected based on their highest presence values to study the response to the severe drought conditions in desert: these were Zilla spinosa and Leptadenia pyrotechnica. The results showed that soil water content and organic matter of Wadi El-Assiuty were very low over the study period. The estimated pH values in the soil solution at the different studied stands tended to be slight alkaline. Total soluble salts were generally higher during summer versus winter. The water content in the studied plants increased significantly during summer. The selected species increased their content of chlorophyll a and b in summer. The stability index of chlorophyll a and b was significantly higher in summer than that estimated in winter. Calcium and magnesium were accumulated in considerable amounts. Ca+2 was the main accumulated cation whereas its concentration were higher than magnesium. Z. spinosa accumulated more sulphates in summer than in winter. Phosphates appeared in low amounts in all the investigated plants. In L. pyrotechnica tissue, Na+ concentration correlated negatively with those found in soil during summer. In winter Na+ and SO4 correlated positively and K+ correlated negatively in Z. spinosa. The studied species showed slightly increase in soluble sugars accumulation. Soluble protein content in Z. spinosa and L. pyrotechnica decreased significantly during winter season. Amino acids content was low and varied between the two investigated species. It seemed that the Z. spinosa is better adapted than L. pyrotechnica to drought conditions, prevailing in the area under study. This judgement can be concluded by the average metabolic potentiality in the species, whereas soluble metabolites (soluble sugars and soluble proteins) were relatively much higher than in the case of L. pyrotechnica.

Abstract In the present study two species were selected based on their highest presence values to study the response to the severe drought conditions in desert: these were Zilla spinosa and Leptadenia pyrotechnica. The results showed that soil water content and organic matter of Wadi El-Assiuty were very low over the study period. The estimated pH values in the soil solution at the different studied stands tended to be slight alkaline. Total soluble salts were generally higher during summer versus winter. The water content in the studied plants increased significantly during summer. The selected species increased their content of chlorophyll a and b in summer. The stability index of chlorophyll a and b was significantly higher in summer than that estimated in winter. Calcium and magnesium were accumulated in considerable amounts. Ca+2 was the main accumulated cation whereas its concentration were higher than magnesium. Z. spinosa accumulated more sulphates in summer than in winter. Phosphates appeared in low amounts in all the investigated plants. In L. pyrotechnica tissue, Na+ concentration correlated negatively with those found in soil during summer. In winter Na+ and SO4 correlated positively and K+ correlated negatively in Z. spinosa. The studied species showed slightly increase in soluble sugars accumulation. Soluble protein content in Z. spinosa and L. pyrotechnica decreased significantly during winter season. Amino acids content was low and varied between the two investigated species. It seemed that the Z. spinosa is better adapted than L. pyrotechnica to drought conditions, prevailing in the area under study. This judgement can be concluded by the average metabolic potentiality in the species, whereas soluble metabolites (soluble sugars and soluble proteins) were relatively much higher than in the case of L. pyrotechnica.