The σ -convergence and σ -core of a real bounded sequence were introduced in [R. Raimi, Invariant means and invariant matrix methods of summability, Duke Math. J. 30 (1963) 81–94] and [S.L. Mishra, B. Satapathy, N. Rath, Invariant means and σ -core, J. Indian Math. Soc. 60 (1984) 151–158], respectively. In this work, we extend these ideas to double sequences. c © 2006 Elsevier Ltd. All rights r...

Introduction Almost 20 percent of the people in the work force are union members. Just in terms of numbers, trade unions are an important influence in the labor market and in the U.S. economy. Further, unions are widely believed to play a major role in determining workers' standard of living and how work is done and in affecting firms' profitability. Freeman and Medoff (1984) recently presented...

Vascular endothelial growth factor A (Vegfa) has important roles in endochondral bone formation. Osteoblast precursors, endothelial cells and osteoclasts migrate from perichondrium into primary ossification centers of cartilage templates of future bones in response to Vegfa secreted by (pre)hypertrophic chondrocytes. Perichondrial osteolineage cells also produce Vegfa, but its function is not w...

Carbon nanoparticles were synthesized from natural gas soot and functionalized with ferrocenyl moieties by using 4-ferrocenylphenyldiazonium as the reactive precursor. The incorporation of the ferrocenyl units onto the carbon nanoparticle surface was confirmed by varied spectroscopic measurements. For instance, in FTIR measurements the characteristic vibrational bands of the ferrocenyl and phen...