According to ahmadreza estakhr model of quarks with integer electric charge, Up-type quarks have no electric charge (0), and only Down-type quarks could have electric charge of minus or plus one(-1 or +1). this is because of weak nuclear interaction between up-type quarks and W^{\pm}.U^0+W^+\to D^+. U^0+W^-\to D^-. only \Delta{++} is not consisted with estakhr's model. his idea is quark content of delta baryon is wrong.ref. http://bit.ly/1flU50Z