I have a scientific collaboration with a senior scientist from a University in Europe. He agreed to work with me on the project and our roles were defined in the process(only supervision and minimal interaction from his side and active contribution from my side). Emails were received regularly from his side till December 22nd (prior to the holidays). After the holidays (on January 8th) I sent him the work that we agreed upon and he has to verify my conclusions and let me know whether I can proceed forward. Yesterday I emailed him inquiring whether his busy schedule has prevented him from responding to my document. Should I assume there is no further interest from his side or can I call him to find out what his thought process is ?