Linear groups and distance-transitive graphs

A detailed treatment is given of the graphs on which a group with simple socle PSL(n, q) acts primitively and distance-transitively

A System Out of Breath: How Hypoxia Possibly Contributes to the Pathogenesis of Systemic Sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by vascular alterations and immunological disturbances and fibrosis, the order of which remains to be fully determined. Clinically, patients show clear signs of hypoxia in skin and internal organs. The low oxygen tension is potentially caused by a yet to be indentified circuitry involving the three features that typify SSc. In addition, once present, the hypoxia creates a vicious circle of ongoing pathology. In this paper, we provide an overview of the evidence that points towards the mechanisms causing hypoxia in SSc. In addition, data that suggest how hypoxia itself may orchestrate worsening of symptoms is presented. Altogether, it is clear that hypoxia is an important hallmark in SSc patients. By providing an overview of the mechanisms at play and the possible therapeutic avenues that have emerged, we hope to stimulate researchers to provide novel clues into the conundrum in SSc patients

Lie algebras and 3-transpositions

We describe a construction of an algebra over the field of order 2 starting from a conjugacy class of 3-transpositions in a group. In particular, we determine which simple Lie algebras arise by this construction. Among other things, this construction yields a natural embedding of the sporadic simple group \Fi{22} in the group $^2E_6(2)$.Comment: 23 page

The Line Emission Region in III Zw 2: Kinematics and Variability

We have studied the Ly-al, Hbeta, Halpha and Mg II2798 line profiles of the Seyfert 1 galaxy III Zw 2. The shapes of these broad emission lines show evidence of a multicomponent origin and also features which may be identified as the peaks due to a rotating disk. We have proposed a two-component Broad Line Region (BLR) model consisting of an inner Keplerian relativistic disk and an outer structure surrounding the disk. The results of the fitting of the four Broad Emission Lines (BELs) here considered, are highly consistent in both the inner and outer component parameters. Adopting a mass of approx. 2 E8 sollar masses for the central object we found that the outer radius of the disk is approximately equal for the four considered lines (approx 0.01 pc). However, the inner radius of the disk is not the same: 0.0018 pc for Ly-alpha, 0.0027 pc for Mg II, and 0.0038 pc for the Balmer lines. This as well as the relatively broad component present in the blue wings of the narrow [OIII] lines indicate stratification in the emission-line region. Using long-term Hbeta observations (1972-1990, 1998) we found a flux variation of the BEL with respect to the [OIII] lines.Comment: ApJ, accepted, 22 pages, 10 figure

Tuning adhesion failure strength for tissue-specific applications

Soft tissue adhesives are employed to repair and seal many different organs, which range in both tissue surface chemistry and mechanical challenges during organ function. This complexity motivates the development of tunable adhesive materials with high resistance to uniaxial or multiaxial loads dictated by a specific organ environment. Co-polymeric hydrogels comprising aminated star polyethylene glycol and dextran aldehyde (PEG:dextran) are materials exhibiting physico-chemical properties that can be modified to achieve this organ- and tissue-specific adhesion performance. Here we report that resistance to failure under specific loading conditions, as well as tissue response at the adhesive material–tissue interface, can be modulated through regulation of the number and density of adhesive aldehyde groups. We find that atomic force microscopy (AFM) can characterize the material aldehyde density available for tissue interaction, and in this way enable rapid, informed material choice. Further, the correlation between AFM quantification of nanoscale unbinding forces with macroscale measurements of adhesion strength by uniaxial tension or multiaxial burst pressure allows the design of materials with specific cohesion and adhesion strengths. However, failure strength alone does not predict optimal in vivo reactivity. Thus, we demonstrate that the development of adhesive materials is significantly enabled when experiments are integrated along length scales to consider organ chemistry and mechanical loading states concurrently with adhesive material properties and tissue response.National Science Foundation (U.S.) (Career Award)American Society for Engineering Education. National Defense Science and Engineering Graduate FellowshipNational Institutes of Health (U.S.) (Grant ERE GM 49039