I have some human adipose tissue samples. -80 C went down on us over the weekend. We are unsure of how long the freezer was actually down for. When we got it back on the outside thermometer on the door read -6 C. I am worried that these tissue samples are compromised. I am mainly concerned if whether or not it would be ethical to still use these samples in my study. It took a year to collect these samples. Are they totally gone? How can I check their viability?