A physical model of cell metabolism

Cell metabolism is characterized by three fundamental energy demands: to sustain cell maintenance, to trigger aerobic fermentation and to achieve maximum metabolic rate. The transition to aerobic fermentation and the maximum metabolic rate are currently understood based on enzymatic cost constraints. Yet, we are lacking a theory explaining the maintenance energy demand. Here we report a physical model of cell metabolism that explains the origin of these three energy scales. Our key hypothesis is that the maintenance energy demand is rooted on the energy expended by molecular motors to fluidize the cytoplasm and counteract molecular crowding. Using this model and independent parameter estimates we make predictions for the three energy scales that are in quantitative agreement with experimental values. The model also recapitulates the dependencies of cell growth with extracellular osmolarity and temperature. This theory brings together biophysics and cell biology in a tractable model that can be applied to understand key principles of cell metabolism

Substructure of jets at HERA

The substructure of jets produced in an exclusive and a charm-induced dijet sample in photoproduction and in charged and neutral current interactions has been studied with the ZEUS detector at HERA. Jets were identified using the longitudinally invariant k_T cluster algorithm in the laboratory frame. The substructure of jets has been studied in terms of the jet shape and subjet multiplicity. Comparisons between the dijet sample and the quark-induced samples allow an extraction of the jet substructure for gluons. Leading-logarithm parton-shower Monte Carlo calculations give a good description of the differences between quark- and gluon-initiated jets. In neutral current interactions, the measurements have been compared to next-to-leading-order QCD calculations which are used to make a determination of the strong coupling constant, alpha_s.Comment: 4 pages, 11 figures, Contribution to the Proceedings of the PHOTON 2001 Conferenc

Self-organization in populations of competing agents

A population of heterogenous agents compeeting through a minority rule is investigated. Agents which frequently loose are selected for evolution by changing their strategies. The stationary composition of the population resulting for this self-organization process is computed analytically. Results are compared with numerical simulations of two different minority games and other analytical treatments available in the literature.Comment: RevTex, 4 pages, 1 ps fi

Studies of Inclusive Jet Production in ep Interactions at HERA

Inclusive jet production in neutral and charged current deep inelastic scattering, in photoproduction and the transition region has been studied with the ZEUS and H1 detectors at HERA. The measurements have been compared to next-to-leading-order QCD calculations which are used to make determinations of the strong coupling constant.Comment: 3 pages, 5 figures, Conference Proceedings EPS200

The Co-opting of Ethnic Studies in the American University: A Critical View

The birth of ethnic studies in the American university was accompanied by the politics and pedagogy of rage, pride, and mistrust for the then prevailing curricular academic structures and its tradition-bound, academically conservative gatekeepers. The campus take-overs, student demands, and confrontations were a common expression of the times, and concomitantly these were also shapers of the changing times. The presence or absence of ethnic minority faculty and students in our universities was and continues to be one of many indices by which we measure the willingness of this society to live up to its responsibility and promise to guarantee expanding educational opportunity for all. The creation of ethnic studies programs as a legitimate academic course of study in the university was one key part of that long range objective. Many universities now boast of departments and programs in Afro-American Studies, Puerto Rican Studies, Chicano Studies, Native American Studies, and other ethnic studies entities. Today\u27s student can leaf through the semester\u27s schedule of courses and choose from a wide array of ethnic studies offerings and think only of whether or not it fits into his/her program. Even traditional academic departments, formerly resolute in their refusal to include ethnic studies courses in their curriculum, now cross-list, and in many instances generate their own version of ethnic studies courses in direct competition with existing ethnic studies programs

Status of the LHCb detector

LHCb is an experiment dedicated to study CP violation and other rare phenomena in B mesons decays with very high precision. It is one of the four experiments that will operate at the 14Tev proton-proton Large Hadron Collider (LHC) at CERN in 2008. Here we briefly describe the current status of the experiment, as well as plans towards a future upgrade.Comment: 5 pages, presented at Lake Louise Winter Institute 200