Using Multitrait-Multimethod (MTMM) Techniques to Examine the Convergent and Discriminant Validity of Social Disorder

Objectives: Disorder has been measured by various data sources; however, little attention has been given to comparing the construct validity of different measures obtained through various methods in capturing social disorder and related phenomena. Methods: The multitrait-multimethod approach was used to triangulate the consistency between social disorder, prostitution and drug activity across resident surveys, systematic social observations, and police calls for service data. Results: Prostitution and drug activity showed convergent validity, while there was little evidence that social disorder was consistently measured across the three methods. None of the three social problem measures showed high discriminant validity. Drug activity seems to have highest trait-specific discriminant validity across measures, and prostitution is the most identifiable measure across data sources. Social disorder was found to have low discriminant validity. However, the agreement between databases varies across the type of social problems. Conclusions: Social disorder appears to the most difficult concept to define and measure consistently. The lack of correspondence across data sources cautions against the use of a single source of information in studying disorder. Future studies should explore the factors that shape perceptions of disorder and how to best measure disorder to test the broken windows thesis and related concepts

Measurements of forces produced by the mitotic spindle using optical tweezers

We used a trapping laser to stop chromosome movements in Mesostoma and crane-fly spermatocytes and inward movements of spindle poles after laser cuts across Potorous tridactylus (rat kangaroo) kidney (PtK2) cell half-spindles. Mesostoma spermatocyte kinetochores execute oscillatory movements to and away from the spindle pole for 1–2 h, so we could trap kinetochores multiple times in the same spermatocyte. The trap was focused to a single point using a 63× oil immersion objective. Trap powers of 15–23 mW caused kinetochore oscillations to stop or decrease. Kinetochore oscillations resumed when the trap was released. In crane-fly spermatocytes trap powers of 56–85 mW stopped or slowed poleward chromosome movement. In PtK2 cells 8-mW trap power stopped the spindle pole from moving toward the equator. Forces in the traps were calculated using the equation F = Q′P/c, where P is the laser power and c is the speed of light. Use of appropriate Q′ coefficients gave the forces for stopping pole movements as 0.3–2.3 pN and for stopping chromosome movements in Mesostoma spermatocytes and crane-fly spermatocytes as 2–3 and 6–10 pN, respectively. These forces are close to theoretical calculations of forces causing chromosome movements but 100 times lower than the 700 pN measured previously in grasshopper spermatocytes