Recall 1.1. The construction of the Steenrod squares and powers proceeds in the following steps 1. For a space X, the p-th cartesian power Xp is acted on cyclically by Z/p and it fits into a fibration Xp → EZ/p×Z/p Xp → BZ/p 2. If x ∈ H∗(X, Z/p), one defines u × · · · × u ∈ H∗(Xp, Z/p) and extends this class to ũ ∈ H(EZ/p×Z/p Xp; Z/p) by a construction on the chain level. 3. ũ is then pulled ba...

The repair of bleomycin-damaged DNA was examined in human fibroblasts isolated from patients having the disease xeroderma pigmentosum (XP). In normal fibroblasts, the appearance of low-molecular-weight DNA was observed in the presence of increasing amounts of the drug. The studies in XP fibroblasts produced results which differed from those obtained in normal cells in two ways. (a) Prelabeled X...

UVB radiation is the most mutagenic component of the UV spectrum that reaches the earth's surface and causes the development of DNA damage in the form of cyclobutane pyrimidine dimers and 6-4 photoproducts. UV radiation usually results in cellular death, but if left unchecked, it can affect DNA integrity, cell and tissue homeostasis and cause mutations in oncogenes and tumour-suppressor genes. ...

This paper reports on a project-oriented course using XP taught at The Johns Hopkins University during the Spring 2001 Semester. The class developed a Java IDE using XP practices.

Cells from patients with xeroderma pigmentosum complementation group D (XP-D) and most patients with trichothiodystrophy (TTD) are deficient in excision repair of ultraviolet (UV) radiation-induced DNA damage. Although in both syndromes this defect is based on mutations in the same gene, XPD, only XP-D, not TTD, individuals have an increased risk of skin cancer. Since the reduction in DNA repai...

The Adaptive Communication Environment (ACE) and The ACE ORB (TAO) are cutting edge, real-time software products that by nature support and grow from change. Therefore, eXtreme Programming (XP) would seem to be appropriate for these projects. In fact, their developers have been following many XP practices all along. We describe these practices here, and identify some that we do not follow rigor...

Let Γ be a discrete group, defined by a presentation P = 〈ai | rj〉, say, or as the fundamental group of a connected CW-complex X. Remark 1.1. Let XP be the CW-complex with a single 0-cell E , one 1-cell E i for each ai (oriented accordingly), and one 2-cell E 2 j for each rj , with attaching map ∂E j → X (1) P that reads off the word rj in the generators {ai}. Then, by the Seifert–van Kampen Th...

An unusual familial case of three sibs with a partial duplication of distal Xp sequences is described. The proband, an 18 year old boy, showed mental retardation, severe dysmorphic features, hypogonadotrophic hypogonadism (HHG), and hypoplastic external genitalia. His karyotype was 46,Y,inv dup(X) (p22.11-->p 22.32). The proband has two sisters each with the same inv dup(Xp) chromosome. Both si...

An ideal XP project is composed of stories defined by the customer that are of the right size and focus to plan and manage according to XP principles and practices. A story that is too large creates a variety of problems: it might not fit into a single iteration; there are a large number of tasks that must be coordinated; it can be too large to test adequately at the story/functional level; too...

SUMMARY Cell strains established from fibroblasts of 10 normal persons, 12 persons afflicted with xeroderma pigmentosum (XP), and 4 XP hétérozygotes have been used as hosts in studies on the repair of ultraviolet-irradiated human adeno-virus 2. The virus appeared most ultraviolet light sensitive when strains belonging to XP complementation Groups A and D were used as hosts, less sensitive whe...