Categoricity and Consistency in Second-Order Logic

We analyse the concept of a second-order characterisable structure and divide this concept into two parts—consistency and categoricity—with different strength and nature. We argue that categorical characterisation of mathematical structures in second-order logic is meaningful and possible without assuming that the semantics of second-order logic is defined in set theory. This extends also to the so-called Henkin structures.     

Adolescent Development and Youth Suicide

The adolescent years, being a period of unique developmental changes, are of great interest in understanding suicidal behavior. The occurrence of completed suicide by age in 1-year age groups in adolescence and young adulthood was studied via official Finnish mortality statistics and the population statistics. Suicide rates increased sharply by age during adolescence, starting somewhat earlier among boys than among girls. During the periods of rapidly rising and high suicide rates in the 1970s and 1980s among boys, the increase in suicide rates started at a younger age than during a spell of lower rates in the 1960s.