This model is based on the in vitro skin model Skin2 [5] which had been discontinued in October 1996. It was further proposed by industry to apply the model in a tiered strategy to identify those chemicals that are predicted to be likely to be phototoxic in the 3T3-NRU-PT but are negative in vivo [6].
401(k) contribution rules. On a pretax basis, employees can't contribute above certain limits. In 2015, for instance, the limit is $18,000; those 50 and older can make additional catch-up contributions of $6,000.This money is not counted toward income, and all gains are tax-deferred. The limits are the same for Roth 401(k)s, though the contributions do count toward income and all gains are tax-free.But employees can sock away a lot more retirement cash if their company plan offers an after-tax option in a traditional 401(k).he limits are the same for Roth 401(k)s, though the contributions do count toward income and all gains are tax-free. But employees can sock away a lot more retirement cash if their company plan offers an after-tax option in a traditional 401(k).
Whereas a Roth 401(k) retirement plan is structured so you make contributions with after-tax dollars, a traditional 401(k) plan allows you to make contributions with pretax money.If you have the latter, your employer subtracts your contributions from your gross income before deducting the required taxes.ubtract your 401(k) contributions from gross income before calculating federal income tax â this is the only federal withholding tax that pretax 401(k) contributions are exempt from. For example, your gross salary for the biweekly pay period is $2,000 and you elect to defer 6 percent to your 401(k) plan.