%0 Journal Article %T A new theorem on the existence of the Riemann-Stieltjes integral and an improved version of the Lo¨¦ve-Young inequality %A Rafa£¿ M. £¿ochowski %J Mathematics %D 2014 %I arXiv %R 10.1186/s13660-015-0901-3 %X Using the notion of the truncated variation we obtain a new theorem on the existence and estimation of the Riemann-Stieltjes integral. As a special case of this theorem we obtain an improved version of the Lo\'{e}ve-Young inequality for the Riemann-Stieltjes integrals driven by irregular signals. Using this result we strenghten some results of Terry Lyons on the existence of solutions of integral equations driven by moderately irregular signals. %U http://arxiv.org/abs/1403.5413v4