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New learning strategies try to extend the use of common devices among students in physics lab practices. In particular, there is a recent trend to explore the possibilities of using smartphone sensors to describe physics phenomena. On the other hand, the study of the moment of inertia by the use of the torsion pendulum is a typical example in the first courses of fundamentals of physics. This example allows the exploration of harmonic motion, Newton's second law, the moment of inertia theory, and the parallel axis theorem all in one. Here, we report the use of the accelerometer sensor of a smartphone to visualize and demonstrate the parallel axis theorem in a torsion pendulum.

A certain HLA-DQA2 locus TaqI fragment, DX alpha"U", has been reported to be associated with insulin-dependent diabetes mellitus (IDDM). Reports of various studies in this vein have ranged from stating that the association of DQA2"U" with IDDM exists even among subjects positive for HLA-DR3 and -DR4 to stating that the association of DQA2"U" with diabetes can be attributed to linkage disequilibrium between the DQA2"U" and some component(s) on the affected haplotypes. Using a synthetic 97-base probe corresponding to a portion of an intron of DQA2, in a Southern blot analysis of IDDM and control subjects from Wisconsin, we were able to confirm the association of DQA2"U" with diabetes. However, among DR3 subjects there was no significant association between DQA2"U" and diabetes (p = 0.26). Although there was a (nonsignificant) association of IDDM with DQA2"U" among DR4-positive subjects (p = 0.14), this can be completely attributed to linkage disequilibrium between DQA2"U" and DQw8. We also sequenced most of the second exon (corresponding to the alpha 1 domain of the DQA2 glycoprotein) from five individuals that were homozygous for either DQA2"U" or DQA2"L." The only polymorphisms observed were a "silent" mutation at position 36 and one example of a difference that would result in a change of amino acid at position 41.

We performed a multiple-affected-sib study to determine if T-cell receptor alpha-chain alleles affect susceptibility to insulin-dependent diabetes mellitus. Restriction fragment length polymorphisms were used to follow the segregation of allelic T-cell receptor alpha complexes within the families. The segregation of T-cell receptor alpha alleles in 29 multiplex families revealed no significant tendency for affected sibs to share T-cell receptor alpha-chain alleles more often than would be expected by chance alone (p greater than 0.2). In contrast, the same type of analysis for HLA alleles easily detected the well-known linkage of insulin-dependent diabetes mellitus susceptibility to the HLA complex (p = 0.003). We suggest that the importance of HLA alleles in insulin-dependent diabetes mellitus susceptibility and the lack of importance of T-cell receptor alpha alleles result from the different strategies by which HLA and T-cell receptor molecules achieve antigen-binding diversity: multiple loci and allelic diversity in the case of HLA; combinatorial, junctional, and N-region diversity in the case of the T-cell receptor. In this paper we also describe three new restriction fragment length polymorphisms of the T-cell receptor alpha complex and a new method for testing the significance of linkage in multiple-affected-sib studies.