Multiplicative Invariants and the Finite Co-Hopfian Property

A group is said to be, finitely co-Hopfian when it contains no proper subgroup of finite index isomorphic to itself. It is known that irreducible lattices in semisimple Lie groups are finitely co-Hopfian. However, it is not clear, and does not appear to be known, whether this property is preserved under direct product. We consider a strengthening of the finite co-Hopfian condition, namely the existence of a non-zero multiplicative invariant, and show that, under mild restrictions, this property is closed with respect to finite direct products. Since it is also closed with respect to commensurability, it follows that lattices in linear semisimple groups of general type are finitely co-Hopfian

Parallizable manifolds and the fundamental group

ntroduction. Low-dimensional topology is dominated by the fundamental group. However, since every finitely presented group is the fundamental group of some closed 4-manifold, it is often stated that the effective influence of π1 ends in dimension three. This is not quite true, however, and there are some interesting border disputes. In this paper, we show that, by imposing the extra condition of parallelizability on the tangent bundle, the dominion of π1 is extended by an extra dimension

Remote sensing and interdisciplinary approach for studying Dubai’s urban context and development

Outlining the different phases and features of the urban and socio-economic development of Dubai, this work is aimed at highlighting the potential of remote sensing and the interdisciplinary approach for the study of cities characterised by overwhelming growth processes. In this way Dubai represents an ideal laboratory since the processes that have been triggered in the last decades have radically modified the previous balances and layouts. Thus the image of a mirage city has been gradually diffused, a city where ambitious objectives can be achieved, targets reached that are difficult to pursue elsewhere, frenetic development processes realised, in a nevertheless increasingly delicate territorial-environmental fabric onto which such phenomena are grafted. The analysis of various remote sensed images, gathered over different periods of times, highlights a number of important aspects from the geological point of view, of the physical geography, the urban development and the direct growth in all directions, with a series of artificial islands and much publicised anthropic works

Syzygies and diagonal resolutions for dihedral groups

We describe the syzygies of dihedral groups of order 4n+

Diagonal resolutions for metacyclic groups

We show the finite metacyclic groups G(p, q) admit a class of projective resolutions which are periodic of period 2q and which in addition possess the properties that a) the differentials are 2×2 diagonal matrices; b) the Swan-Wall finiteness obstruction (cf [21], [22]) vanishes. We obtain thereby a purely algebraic proof of Petrie’s Theorem ([16]) that G(p, q) has free period 2q

Diversity of progeny from a single colony of Salmonella typhimurium after 19 months in sealed agar stabs

Abstract only availableRecent studies at the Cancer Research Center revealed numerous mutations in Salmonella typhimurium that had been sealed in agar stab vials and stored for over forty years. The bacteria that were conserved in over 20,000 vials were all progeny of the same S. typhimurium strain. However, they were not progeny from a single colony (thus, a single parental cell), but from cultures used in genetic studies in several laboratories. To continue the evolutionary and mutational study of S.typhimurium, a new set of 100 similar agar stabs were inoculated 19 months ago from a single colony (thus, a single parental cell), and sealed. Cells from this set were assayed to see if mutations had occurred. Through motility tests, colony growth on three media, re-streaking of unique colonies, and phage spot testing, genetic variability was observed after 19 months storage. In this amount of time enough mutation did occur to display diverse phenotypes among progeny of the single strain of S. typhimurium. To confront any concerns that the mutations may have been present 19 months ago, a -80 °C stock of the parent colony was used as a control. While the phenotypic changes were significantly less then the vials stored for forty years, it is obvious that 19 months was enough time for genetic variability to occur in S. typhimurium from a single parent. Support from Cancer Research Center. Special thanks to Dustin Newman and Alison Fea for technical instruction.Cancer Research Cente

The Way of Improvement Leads Home: Philips Vickers Fithian’s Rural Enlightenment

Offers a look at the life of Philip Vickers Fithian, a diarist from southern New Jersey, in an effort to assess the influence of the Enlightenment in the British American colonies. Profile of Fithian; His perception on personal morality and behavior; Political and social issues tackled in his journal; Efforts to reconcile the pursuit of Enlightenment self-improvement with passion and love for home