Project Size and Software Maintenance Productivity: Empirical Evidence on Economies of Scale in Software Maintenance

Although appropriate sizing of software projects is a concern in software development, Information Systems managers generally do not consider maintenance project size as a potentid influence on software maintenance productivity. This view ignores potential efficiency gains which may arise from proactive renovationstrategiessuchasbatchingsimilarmaintenancerequestsintolargerprojects. Inthisstudy,we explore the relationship between project size and productivity for software rmintenance projects at a major national mass merchandising retailer. Using a non-parametric methodology called Da& Envelopment Analysis (DEA) for estimating the functional relationship between maintenance inputs and outputs, we determine the most productive scale size for a set of maintenance projects at this organization. In addition, we also employ DEA-based heuristics to test for the existence of returns to scale for the projects. Our results indicate the presence of significant scale economies in these software maintenance projects. The most productive scale size is larger than 90% of the projects included in our sample. These results imply that there may be potential to increase productivity in software maintenance at this organization by grouping smaller modification projects into larger planned releases

Nonclassical binding of formylated peptide in crystal structure of the MHC class lb molecule H2-M3

AbstractH2-M3 is a class Ib MHC molecule of the mouse with a 104-fold preference for binding N-fonmylated peptides. To elucidate the basis of this unusual specificity, we expressed and crystallized a soluble form of M3 with a fonnylated nonamer peptide, fMYFINILTL, and determined the structure by X-ray crystallography. M3, refined at 2.1A˚resolution, resembles class la MHC molecules in its overall structure, but differs in the peptide-binding groove. The A pocket, which usually accommodates the free N-terminus of a bound peptide, is closed, and the peptide Is shifted one residue, such that the P1 side chain is lodged in the B pocket. The formyl group Is coordinated by His-9 and a bound water on the floor of the groove

The Specificity of Peptides Bound to Human Histocompatibility Leukocyte Antigen (HLA)-B27 Influences the Prevalence of Arthritis in HLA-B27 Transgenic Rats

Human histocompatibility leukocyte antigen B27 is highly associated with the rheumatic diseases termed spondyloarthropathies, but the mechanism is not known. B27 transgenic rats develop a spontaneous disease resembling the human spondyloarthropathies that includes arthritis and colitis. To investigate whether this disease requires the binding of specific peptides to B27, we made a minigene construct in which a peptide from influenza nucleoprotein, NP383-391 (SRYWAIRTR), which binds B27 with high affinity, is targeted directly to the ER by the signal peptide of the adenovirus E3/gp19 protein. Rats transgenic for this minigene, NP1, were made and bred with B27 rats. The production of the NP383-391 peptide in B27+NP1+ rats was confirmed immunologically and by mass spectrometry. The NP1 product displaced ∼90% of the 3H-Arg-labeled endogenous peptide fraction in B27+NP1+ spleen cells. Male B27+NP1+ rats had a significantly reduced prevalence of arthritis, compared with B27+NP− males or B27+ males with a control construct, NP2, whereas colitis was not significantly affected by the NP1 transgene. These findings support the hypothesis that B27-related arthritis requires binding of a specific peptide or set of peptides to B27, and they demonstrate a method for efficient transgenic targeting of peptides to the ER

Characterization of the Moraxella catarrhalis uspA1 and uspA2 Genes and Their Encoded Products

The uspA1 and uspA2 genes of M. catarrhalis O35E encode two different surface-exposed proteins which were previously shown to share a 140-amino-acid region with 93% identity (C. Aebi, I. Maciver, J. L. Latimer, L. D. Cope, M. K. Stevens, S. E. Thomas, G. H. McCracken, Jr., and E. J. Hansen, Infect. Immun. 65:4367–4377, 1997). The N-terminal amino acid sequences of the mature forms of both UspA1 and UspA2 from strain O35E were determined after enzymatic treatment to remove the N-terminal pyroglutamyl residue that had blocked Edman degradation. Mass spectrometric analysis indicated that the molecular mass of UspA1 from M. catarrhalis O35E was 83,500 ± 116 Da. Nucleotide sequence analysis of the uspA1 and uspA2 genes from three other M. catarrhalis strains (TTA24, ATCC 25238, and V1171) revealed that the encoded protein products were very similar to those from strain O35E. Western blot analysis was used to confirm that each of these three strains of M. catarrhalis expressed both UspA1 and UspA2 proteins. Several different and repetitive amino acid motifs were present in both UspA1 and UspA2 from these four strains, and some of these were predicted to form coiled coils. Linear DNA templates were used in an in vitro transcription-translation system to determine the sizes of the monomeric forms of the UspA1 and UspA2 proteins from strains O35E and TTA24

Bub1-Mediated Adaptation of the Spindle Checkpoint

During cell division, the spindle checkpoint ensures accurate chromosome segregation by monitoring the kinetochore–microtubule interaction and delaying the onset of anaphase until each pair of sister chromosomes is properly attached to microtubules. The spindle checkpoint is deactivated as chromosomes start moving toward the spindles in anaphase, but the mechanisms by which this deactivation and adaptation to prolonged mitotic arrest occur remain obscure. Our results strongly suggest that Cdc28-mediated phosphorylation of Bub1 at T566 plays an important role for the degradation of Bub1 in anaphase, and the phosphorylation is required for adaptation of the spindle checkpoint to prolonged mitotic arrest