On the survival probability of a random walk in random environment with killing

We consider one dimensional random walks in random environment where every time the process stays at a location, it dies with a fixed probability. Under some mild assumptions it is easy to show that the survival probability goes to zero as time tends to infinity. In this paper we derive formulas for the rate with which this probability decays. It turns out that there are three distinct regimes, depending on the law of the environment

Temporary fat storage, an adaptation of some fish species to the waterlevel fluctuations and related environmental changes of the Amazon river

Analysis of Amazonian freshwater fish exhibited great differences in water- and fat content. Migratory species which deposit huge amounts of eggs in a single spawning act accumulate at high water-level great amounts of fat in various parts of the body. Nonmigratory species which spawn small quantities of eggs several times per year show little or no seasonality in fat storage. Fat storage is related to the energy requirements of the species and is considered a very successful strategy by which many Amazonian fish species survive drastic environmental and related food supply changes, which are a result of the great monomodal waterlevel fluctuations of the Amazon and its big tributaries

Investigations on the ecology and production-biology of the "floating meadows" (Paspalo-Echinochloetum) on the Middle Amazon. Part 1: The floating vegetation and its ecology

Investigations on the "floating meadows" (Paspalo-Echinochloetum) of the vârzea- region of central Amazonia in the surroundings of Manaus were made from May 1967 until October 1968. The ecology of the dominating species Pasþalum reþens BERG, Pasþalum fasciculatum WILLD., Echinocltloa þoþstaclqta (H. B. K.) HITCCHKOCK, Leersia ltexandra Swart (Fam. Gramineae) and diverse subsidiary species (Oryza þerennis Moench, Hymeachne amþlexicaalis (Rudge) Nens, Panicum chloroticum Nens (.Fam. Gramineae), Scirþus cubensis Poepp Kunth. (Fam. Cyperaceae) etc., was studied in details. Regarding Pasþalum reþens Berg, various floating and one terrestrial forms of growth were observed. Further, quantitative investigations on primary production and the development of populations of this species were made. As shown by 4 Pasþalum reþens- populations which were growing under different environmental conditions, conclusions on age and rapidity of growth of the population could be drawn from the relation between quantity of stems and number of shoots. The preliminary conditions for a "secondary colonization" of floating populations by non-floating plants and the repercussions of such sort of colonization on the primary populations are discussed. The vârzea-waters are subdivided into 3 biotopes with regard to the floating vegetation, and the factors responsible for them are discussed: l) Bank- and sedimentation-zones in the Solimões-Amazon. Dominating species: Pasþalumfasciculatum, Pasþalum reþens, Echinocltloa poþstaclgta, 2) Vârzea lakes with high fluctuations of water level. Dominating species: Pasþalum fasciculatum, Pasþalum. reþens, Echinocltloa þoþstachya. Sometimes, however, as well all other mentioned species occur in masses. Biotope richest in species. 3) Várzea lakes with relatively little fluçtuations of water level. Dominating species: Leersia hexandra, Scirþus cubensis, Pasþalum reþens. Both the current-region of the Solimões-Amazon as a biotope of its own and the influence of black-water on the vegetation are discussed

Confidence Level Computation for Combining Searches with Small Statistics

This article describes an efficient procedure for computing approximate confidence levels for searches for new particles where the expected signal and background levels are small enough to require the use of Poisson statistics. The results of many independent searches for the same particle may be combined easily, regardless of the discriminating variables which may be measured for the candidate events. The effects of systematic uncertainty in the signal and background models are incorporated in the confidence levels. The procedure described allows efficient computation of expected confidence levels.Comment: 17 pages, 2 figures, LaTeX, program available at http://home.cern.ch/~thomasj/searchlimits/ecl.html one replacement to fix a typo in a UR

Searches at LEP

Searches have been conducted for a broad range of new phenomena by the four experiments ALEPH, DELPHI, L3, and OPAL, at LEP2. Each experiment contributes approximately 150 pb-1 of e+e- annihilation data with a mean sqrt(s) of 205.9 GeV in 2000 to these searches (data prepared for the September 5 LEPC meeting). The statistical procedure for setting limits and evaluating the significance of excesses observed in the data is reviewed. Search results are presented for the Standard Model Higgs boson, the neutral Higgs bosons in the MSSM, charged Higgs bosons, invisibly decaying Higgs bosons produced by Higgs-strahlung, and fermiophobic Higgs bosons. Search results are briefly summarized for gauginos, stops, and staus. The photon recoil spectrum is checked for hints of new physics.Comment: 31 pages, LaTeX, 14 figures. All figures are .eps files. Tables and figures are at the end of the note. This note is a conference proceedings submission for the 5th International Symposium on Radiative Corrections (RADCOR2K), Carmel, California, September 11-15, 2000 Replacement 12 January 2001 -- add some parentheses to Equation

Recent Heavy-Flavor Measurements from OPAL

A selection of recent heavy-flavor results from OPAL using the LEP1 data sample are presented. The average polarization of b baryons in hadronic Z^0 decay has been measured to be -0.56^{+0.20}_{-0.13} (stat.) +- 0.09(syst.) using semileptonic decays of Lambda_b baryons. A search has been conducted for the radially excited D*' and has produced a 95% CL upper limit on its production of f(Z^0 -> D*'+-(2629))xBr(D*'+- -> D*+- pi+ pi-) < 2.1x10^{-3}. Finally, the measurement of the product branching ratio $f(b -> Lambda_b)xBr(Lambda_b -> Lambda X)= (2.67 +- 0.38 (stat) ^{+0.67}_{-0.60}(syst.))% has been made. This measurement, along with an earlier measurement of the product branching ratio f(b -> Lambda_b)xBr(Lambda_b -> Lambda l X), has been used to compute an updated R_{Lambda l} = Br(Lambda_b -> Lambda l X)/Br(Lambda_b -> \Lambda X)= (8.0 +- 1.2 (stat.) +- 0.9 (syst.))%, consistent with the expected low semileptonic branching fraction of the Lambda_b inferred from its short lifetime compared to the other b hadrons.Comment: 9 Pages, LaTeX, 4 figures. Proceedings contributed to DPF'99, UCLA, Parallel session talk 3.0