Box complexes, neighborhood complexes, and the chromatic number

Lovasz's striking proof of Kneser's conjecture from 1978 using the Borsuk--Ulam theorem provides a lower bound on the chromatic number of a graph. We introduce the shore subdivision of simplicial complexes and use it to show an upper bound to this topological lower bound and to construct a strong Z_2-deformation retraction from the box complex (in the version introduced by Matousek and Ziegler) to the Lovasz complex. In the process, we analyze and clarify the combinatorics of the complexes involved and link their structure via several ``intermediate'' complexes.Comment: 8 pages, 1 figur

Efficacy and Safety Of Radiation Synovectomy with Yttrium-90

In this long term retrospective study of radiation synovectomy with Yttrium-90 (Y90), we evaluated the results of 164 applications in 82 patients with RA, OA with synovitis, ankylosing spondylitis and psoriatic arthritis. Radiation synovectomy with Y90 has an overall success rate of approximately 50% and is therefore an effective alternative to surgical synovectomy in chronic synovitis which fails to respond to conservative treatment. Elbow and knee responded significantly better than shoulder and ankle joints. Patients with radiological stages from 0 to 2 showed a significantly better success rate than those with stage 3 changes. In responders, repeat therapy for recurrence of symptoms or treatment of a symptomatic corresponding symmetrical joint is advisable. Repeat therapy in a previous non-responder is associated with an unacceptably high failure rate. Therefore, when a joint fails to respond after 6 months, arthroscopy should be performed to evaluate further treatment procedures. A successful result was found in only 11 of 25 joints treated with arthroscopic synovectomy followed by radiation synovectomy within 2 weeks, indicating no benefit of this combination

Alliance portfolios and value creation: Theory and empirical evidence from the global airline industry

Les carteres d'aliances importen? Com afecten els recursos als quals les empreses accedeixen per diverses aliances estratègiques simultànies amb socis diferents a la creació de valor i a l'apropiació de valor? Les carteres d'aliances expliquen l'heterogeneïtat entre empreses respecte del valor que capten quan entren en noves aliances estratègiques? Aquesta tesi doctoral es basa en la teoria dels recursos i en la bibliografia sobre el comportament estratègic i les dinàmiques competitives, i presenta un model teòric que es refereix a la creació de valor i l'apropiació en empreses que accedeixen a recursos a través de diverses aliances simultànies amb socis diferents. El model mostra que la creació de valor en les carteres d'aliances és una funció del valor creat per combinacions sinergètiques de recursos que impliquen recursos als quals tenen accés diferents socis, com també del valor destruït a causa de la incompatibilitat entre la combinació de recursos d'una empresa focal i els recursos dels seus socis. Sobre la base d'aquest model teòric, s'han desenvolupat diverses hipòtesis en un ambient marginal en què una empresa connectada multilateralment afegeix una nova aliança estratègica a la seva cartera d'aliances. Per comprovar aquestes hipòtesis, s'ha emprat la metodologia de l'event study i s'han utilitzat dades de la indústria de els línies aèries globals sobre acords de code share subscrits entre 1994 i 1998. Els resultats mostren que el mercat recompensa les empreses que formen aliances amb socis que tenen recursos complementaris i poden aportar recursos que no només es poden combinar amb els recursos propis de l'empresa sinó també amb els relacionals i que també són compatibles amb els dels socis que formen l'aliança. D'altra banda, els resultats també mostren que el mercat penalitza les empreses que formen aliances que aporten recursos incompatibles amb les carteres d'aliances, atès que creen un conflicte competitiu amb alguns dels socis existents. Els resultats de la part empírica d'aquesta anàlisi abonen la tesis que les carteres d'aliances afecten els resultats de les empreses que entren en aliances estratègiques. Aquest estudi conclou que els recursos als quals es té accés per mitjà d'aliances entre empreses s'han d'avaluar no tan sols per les seves característiques pròpies y diàdiques sinó també en el context de les carteres d'aliances.¿Importan los portafolios de alianzas? ¿Cómo afectan los recursos a los que acceden las empresas por varias alianzas estratégicas simultáneas con socios diferentes a la creación de valor y a la apropiación de valor? Los portafolios de alianzas ¿explican la heterogeneidad entre empresas con respecto al valor que captan cuando entran en nuevas alianzas estratégicas? Esta tesis doctoral se basa en la teoría de los recursos y en la bibliografía sobre el comportamiento estratégico y las dinámicas competitivas, y presenta un modelo teórico que se refiere a la creación de valor y apropiación en empresas que acceden a recursos a través de varias alianzas simultáneas con socios diferentes. El modelo muestra que la creación de valor mediante un portafolio de alianzas es una función del valor creado por combinaciones sinergéticas de recursos que implican recursos a los cuales acceden diferentes socios, así como del valor destruido a causa de la incompatibilidad entre la combinación de recursos de una impresa focal y los recursos de sus socios. Sobre la base de este modelo teórico, se han desarrollado varias hipótesis en un ambiente marginal en el que una empresa conectada multilateralmente añade una nueva alianza estratégica a su cartera de alianzas. Para comprobar estas hipótesis se ha empleado la metodología del event study, y se han utilizado datos de la industria global de las aerolíneas sobre acuerdos de code share suscritos entre 1994 y 1998. Los resultados muestran que el mercado recompensa a las empresas que forman alianzas con socios que tienen recursos complementarios y pueden aportar recursos que no sólo pueden combinarse con los recursos propios de la empresa sino también con los relacionales y que también son compatibles con los de los socios que forman la alianza. Por otra parte, los resultados también muestran que el mercado penaliza a las empresas que forman alianzas que aportan recursos que son incompatibles con los portafolios de alianzas, en el sentido de que crean un conflicto competitivo con algunos de los socios existentes. Los resultados de la parte empírica de este análisis abonan la tesis de que los portafolios de alianzas afectan a los resultados de empresas que entran en alianzas estratégicas. Este estudio concluye que los recursos a los que se accede a través de las alianzas entre empresas han de evaluarse no sólo por sus características propias y diádicas sino también en el contexto de los portafolios de alianzas.Do alliance portfolios matter? How do resources accessed from multiple simultaneous strategic alliances with different partners affect value creation and value appropriation? Do alliance portfolios explain heterogeneity across firms with respect to the value that they derive from entering into new strategic alliances? This dissertation builds on insights from the resource-based view of the firm and the strategic behaviour and competitive dynamics literature and advances a theoretical model that addresses value creation and appropriation in firms that access resources through multiple simultaneous inter-firm alliances with different partners. The model illustrates that value creation on the alliance portfolio level is a function of the value created from synergistic resource combinations involving resources accessed from different partners as well the value destroyed by incompatibilities between a focal firm's resource combinations and those deployed by its partners. Based on this theoretical model, empirically testable hypotheses are developed in a marginal setting, in which a multilaterally connected firm adds one new strategic alliance to its alliance portfolio. The hypotheses are tested using an event study method approach and data from the global airline industry on code share agreements formed between 1994 and 1998. The results show that the market on one side rewards firms entering into strategic alliances with partners that possess complementary resources and that contribute resources that cannot only be combined with firms' own but also existing relational resources and that are compatible with the firms' alliance portfolios. On the other side, results show that the market penalizes firms entering into alliances that contribute resources that are alliance portfolio incompatible in the sense that they create a competitive conflict with some of the existing alliance partners. The findings of the empirical part of this dissertation support the view that alliance portfolios affect the performance of firms entering into strategic alliances. This study concludes that resources accessed through inter-firm alliances should not only be evaluated on their standalone and dyadic attributes but also in the context of alliance portfolios

Using California’s Farmland Preservation Programs to Reduce Greenhouse Gas Emissions

California has long tried to preserve land devoted to agricultural production. Recently it became the leader in creating a statewide policy to reduce greenhouse gases. The State’s policy choices regarding farmland preservation and reducing greenhouse gas emissions are interrelated. California’s environmental and agricultural stakeholders point to the presence of three farmland conservation programs (and other programs and multiple policies throughout different codes) as encouraging the retention of agricultural land and thus resulting in less urban sprawl, less vehicle miles travelled, and less green house gases generated in the state. The purpose of this paper is to examine this claim and to tender an opinion on its validity. Offered also are suggestions on how to tie together better the dual goals of farmland preservation and greenhouse gas reduction in California. *The California Department of Conservation commissioned the production of this paper. The opinions expressed here are only my own and in no way represent the opinions of the California Department of Conservation. Al Sokolow, Larelle Burkham-Greydanus, Peter Detwiler, Fielding Greaves, Brian Leahy, Scott Limpach, and Charles Tyson offered helpful comments on an earlier draft. Any errors that remain are my own. This is a condensed version of Wassmer (2009)

Antigen-armed antibodies (AgAbs) in the treatment of Acute Myeloid Leukemia (AML)

Acute myeloid leukemia (AML) accounts for 80% of acute leukemia cases in adults and results from the accumulation of immature malignant myeloid progenitor cells at the expense of healthy differentiated counterparts. These cells invade the bone marrow, the blood and can also infiltrate organs in the periphery. While recent progresses in AML management moderately improved the survival of patients below the age of 65, about 70% of older patients succumb to the disease within one year after diagnosis. Therefore, the search for more therapeutic options in AML is imperative. In this doctoral work, a novel approach based on the AML-specific antibodies designed to deliver immunodominant Epstein-Barr virus (EBV) epitopes to AML tumour cells is assessed. These antigen-armed antibodies (AgAbs) target surface markers upregulated on AML cells, namely CD33, CD123, CLL-1 and FR-b. After receptor-mediated endocytosis, the viral epitopes included in the AgAbs are shuttled into the endosomal compartments of the target cells, where the epitopes can be processed for MHC class II-restricted presentation on the cell surface. In EBV-positive individuals (95% of the human population worldwide), circulating memory virus-specific cytotoxic CD4+ T cells can recognize the MHCII-bound peptides and mediate cell lysis. This strategy aims at boosting the low basal immunogenicity of AML blasts in order to redirect a potent anti-viral immunity toward these cancer cells. In vitro experiments with multiple AML cell lines demonstrated the potency of AgAbs to target the aforementioned surface marker, culminating in the presentation of epitopes at the cell surface. This led to a strong EBV-specific CD4+ T cell activation, characterized by IFNg and granzyme B secretion. These activated T cells were also capable of directly eliminating AgAb-treated AML cell line cells. Furthermore, AgAb-mediated T cell activation was shown to eliminate bystander malignant cells, probably through IFNg and TNF-a signaling. Ex vivo experiments with AgAbs showed a promising potential to stimulate EBV-specific memory CD4+ T cells from AML patients. Upon AgAb treatment, these cells proliferated and killed a substantial proportion of patient blasts. Finally, a murine model of AML was developed. AgAbs fused to murine cytomegalovirus epitopes potently expanded murine CD4+ T cells in vivo, culminating in a prolonged survival in AgAb-treated tumour-bearing mice. Altogether, the promising results from this study demonstrate the potential of AgAbs to redirect endogenous CD4+ cytotoxic T cells against AML cells loaded with EBV antigens, paving the way for future studies and clinical trials