Hasil untuk "Competition"

K. Lancaster

R. May, Warren J. Leonard

B. Menge

R. Deneckere, C. Davidson

D. Buss

James M. Utterback, Fernando F. Suarez

Why some firms die while others survive? Survival has long been recognized as a basic goal for a manufacturing firm. At least in the long term, survival should be related to various measures of performance, such as market share and profitability. Advocates of population ecology have argued that life chances of organizations are affected by population density at the time of founding. According to this argument, organizations founded during periods of intense competition will have persistently higher age-specific rates of mortality than those founded during periods with lower numbers of competitors. At least for the case of manufacturing firms, there may be more profound causes than competitive turmoil that explain a firm's survival chances. These have to do with the evolution of technology in an industry. Population density may only be a reflection of underlying driving forces based on technological change that determine the form and level of competition, the attractiveness of entry, and ultimately the structure of an industry.

J. Gurevitch, Laura L. Morrow, Alison Wallace et al.

Lawrence M. Ausubel

J. Tirole, J. Laffont

J. Lin, F. Cai, Zhou Li

A. Tsay, N. Agrawal

J. Michie, R. Burt

Rajesh K. Aggarwal, Andrew A. Samwick

Lode Li

S. West, I. Pen, A. Griffin

Joel Podolny

Yadong Luo

Marcel Dickmann, Ricardo Helm, Werner Egger et al.

We investigate the thermal evolution of implantation-induced defects in single-crystal CVD diamond using depth-resolved positron annihilation lifetime spectroscopy (PALS). Samples were implanted with 0.5MeV N+ ions at a fluence of 1×1014cm−2 and annealed between 600∘C and 1200∘C. We probe defect populations as a function of depth and quantify their types and concentrations. In the pristine material, small vacancies, predominantly divacancies, are detected at ∼ppm levels together with a low concentration of larger vacancy clusters. Nitrogen implantation increases the abundance of mono-/divacancies. In nitrogen-rich regions, fewer isolated vacancies are observed despite higher displacement damage. Upon annealing, small vacancies become mobile. In nitrogen-poor regions, they agglomerate and grow pre-existing clusters. In contrast, in nitrogen-rich zones, they are efficiently captured by substitutional nitrogen to form NV centers, which limits the formation of new vacancy clusters. At annealing above 1000∘C, positron annihilation occurs predominantly in perfect bulk or small open-volume defects consistent with NV center-related positron lifetimes. These results reveal a nitrogen content- and temperature-dependent competition between vacancy clustering and NV center formation.

Christoph A. Walser, Andrew M. Wymore, Travis K. Landon et al.

Regional climate change models for the Pacific Northwest, USA, predict increased summer streamflow intermittency. During low summer flows, fishes experience abiotic (e.g., low dissolved oxygen, high temperature) and biotic (e.g., competition, predation) stressors that can alter individual fish health, population persistence, and fish assemblage structure. In this observational study, we evaluated the impact of decreasing summer streamflow on water physicochemistry, macroinvertebrate abundance, and condition of resident (stream-dwelling) Columbia River redband trout (Oncorhynchus mykiss gairdneri) in Dry Creek, an intermittent stream in southwestern Idaho, USA. During the summer (June to September) of 2019, we used Onset®, HOBO® loggers to monitor stream temperature and dissolved oxygen at 30-min intervals in 10 study reaches within a 3.5 ​km stream section. Current velocity and habitat volume were measured weekly and drifting macroinvertebrates were sampled biweekly in each study reach. Redband trout were collected monthly and we used Fulton’s condition factor (K) as a surrogate for trout health. During the study period, current velocity and habitat volume decreased. Mean daily water temperatures (6.4–22.3 ​°C) were within the reported range for redband trout. However, in late summer, dissolved oxygen fell below the critical limit (5–6 ​mg/L) for salmonids. Macroinvertebrate drift density (number of macroinvertebrates/L) and macroinvertebrate drift biomass (mg/L) did not differ across summer months. However, macroinvertebrate drift rate (number of macroinvertebrates/15 ​min) was significantly lower in August than June or July (p ​< ​0.05). Median K for trout was lower in August (1.01) and September (0.91) than in July (1.25) (p ​< ​0.05). We propose that the decline in redband trout condition was because of intermittency-associated stressors (hypoxic conditions and decreased macroinvertebrate prey).

G. Kilduff, Hillary Anger Elfenbein, Barry M. Staw