Environmental Variation, Stochastic Extinction, and Competitive Coexistence

Understanding how environmental fluctuations affect population persistence is essential for predicting the ecological impacts of expected future increases in climate variability. However, two bodies of theory make opposite predictions about the effect of environmental variation on persistence. Single‐species theory, common in conservation biology and population viability analyses, suggests that environmental variation increases the risk of stochastic extinction. By contrast, coexistence theory has shown that environmental variation can buffer inferior competitors against competitive exclusion through a storage effect. We reconcile these two perspectives by showing that in the presence of demographic stochasticity, environmental variation can increase the chance of extinction while simultaneously stabilizing coexistence. Our stochastic simulations of a two‐species storage effect model reveal a unimodal relationship between environmental variation and coexistence time, implying maximum coexistence at intermediate levels of environmental variation. The unimodal pattern reflects the fact that the stabilizing influence of the storage effect accumulates rapidly at low levels of environmental variation, whereas the risk of extinction due to the combined effects of environmental variation and demographic stochasticity increases most rapidly at higher levels of variation. Future increases in environmental variation could either increase or decrease an inferior competitor’s expected persistence time, depending on the distance between the present level of environmental variation and the optimal level anticipated by this theory

Factors that influence transition to advanced roles by RN to BSN nurses, in three selected hospitals of Central-Uganda

Background Despite the global rise in the number of nurses upgrading from Registered Nursing (RN) to a Bachelor of Science in Nursing (BSN), studies have indicated that successful role transition is difficult once the nurses return to their previous workplaces. Guided by the Transitional Theory, this study investigates the factors that influence the transition from basic to advanced roles among RN to BSN nurses in Uganda, Africa. Methods This study employed a descriptive correlational design. Using convenience sampling, fifty-one (51) RN to BSN nurses completed the semi-structured questionnaires. Results All the study participants (100%) described themselves as having transitioned from RN to BSN role. In bivariate linear regression, personal factors that were found to predict successful role transition included holding a managerial role, being aware and prepared for the role transition, and positive role transition experiences. Role transition motivators that predicted successful role transition included: job promotion, internal desire for self-development, and career development. One community factor – that is the support of doctors/physicians during the RN to BSN transition – predicted unsuccessful role transition. Societal factors deterring successful role transition included lack of support from other colleagues and the perception that BSN learning was not applicable to the RN clinical setting. In multivariate linear regression, only sub-scales of personal factors such as advanced skills mastery and positive personal experiences predicted successful role transition. Conclusion The study suggests that personal factors influence successful role transition more than external factors

Conformational Preferences of 3-(Dimethylazinoyl)propanoic Acid as a Function of pH and Solvent; Intermolecular versus Intramolecular Hydrogen Bonding

The conformational equilibrium of 3-(dimethylazinoyl)propanoic acid (DMAPA, azinoyl = N^+(O^−) has a weak pH-dependence in D_2O, with a slight preference for trans in alkaline solutions. The acid ionization constants of the protonated amine oxide and carboxylic functional groups as determined by NMR spectroscopy were 7.9 × 10^(−4) and 6.3 × 10^(−6), respectively. The corresponding value of K_1/K_2 of 1.3 × 10^2 is not deemed large enough to provide experimental NMR evidence for a significant degree of intramolecular hydrogen bonding in D_2O. Conformational preferences of DMAPA are mostly close to statistical (gauche/trans = 2/1) in other protic solvents, e.g., alcohols. However, the un-ionized form of DMAPA appears to be strongly intramolecularly hydrogen-bonded and gauche in aprotic solvents

Experimental Demonstration of an Allee Effect in Microbial Populations

Microbial populations can be dispersal limited. However, microorganisms that successfully disperse into physiologically ideal environments are not guaranteed to establish. This observation contradicts the Baas-Becking tenet: ‘Everything is everywhere, but the environment selects’. Allee effects, which manifest in the relationship between initial population density and probability of establishment, could explain this observation. Here, we experimentally demonstrate that small populations of Vibrio fischeri are subject to an intrinsic demographic Allee effect. Populations subjected to predationby the bacterivore Cafeteria roenbergensis display both intrinsic and extrinsic demographic Allee effects. The estimated critical threshold required to escape positive densitydependence is around 5, 20 or 90 cells ml-1 under conditions of high carbon resources, low carbon resources or low carbon resources with predation, respectively. Thiswork builds on the foundations ofmodern microbial ecology, demonstrating that mechanisms controlling macroorganisms apply to microorganisms, and provides a statistical method to detect Allee effects in data

Recent Legal Literature

Pomeroy: Equity Jurisprudence and Equitable Remedies, 3rd ed.; Ware: Roman Water Law, translated from the Pandects of Justinian; Scott (ed.): Cases on Quasi-Contracts; Woodruff: Selected Cases on the Law of Quasi-Contracts; Clark and Skyles: A Treatise on the Law of Agency; Clark and Marshall: A Treatise on the Law of Crimes; Hill: Lincoln the Lawye

Note and Comment

Repeals by Implication - Prohibition in Michigan - At the November election of. 1916 the people of the state of Michigan ratified the following amendment to the constitution of that state: The manufacture, sale, giving away, bartering or furnishing of any vinous, malt, brewed, fermented, spiritous or intoxicating liquors, except for medicinal, mechanical, chemical, scientific or sacramental purposes shall be after April thirty, nineteen hundred eighteen, prohibited in the State forever. The Legislature shall by law provide regulations for the sale of such liquors for medicinal, mechanica, cheinical, scientific and sacramental purposes

Intraaortic balloon pumping for cardiac support: Trends in practice and outcome, 1968 to 1995

AbstractObjectives: A total of 4756 cases of intraaortic balloon pump support have been recorded at the Massachusetts General Hospital since the first clinical insertion for cardiogenic shock in 1968. This report describes the patterns of intraaortic balloon use and associated outcomes over this time period.Methods: A retrospective record review was conducted.Results: Balloon use has increased to more than 300 cases a year at present. The practice of balloon placement for control of ischemia (2453 cases, 11.9% mortality) has become more frequent, whereas support for hemodynamic decompensation (congestive heart failure, hypotension, cardiogenic shock) has been relatively constant (1760 cases, 38.2% mortality). Mean patient age has increased from 54 to 66 years, and mortality has fallen from 41% to 20%. Sixty-five percent (3097/4756) of the total patient population receiving balloon support underwent cardiac surgery. Placement before the operation (2038 patients) was associated with a lower mortality (13.6%) than intraoperative (771 patients, 35.7% mortality) or postoperative use (276 patients, 35.9% mortality). Independent predictors of death with balloon pump support were insertion in the operating room or intensive care unit, transthoracic insertion, age, procedure other than angioplasty or coronary artery bypass, and insertion for cardiogenic shock. Independent predictors of death with intraoperative balloon insertion were age, mitral valve replacement, prolonged cardiopulmonary bypass, urgent or emergency operation, preoperative renal dysfunction, complex ventricular ectopy, right ventricular failure, and emergency reinstitution of cardiopulmonary bypass.Conclusions: Balloons are being used more frequently for control of ischemia in more patients who are elderly with lower mortality. An institutional bias toward preoperative use of the balloon pump appears to be associated with improved outcomes. (J Thorac Cardiovasc Surg 1997;113:758-69

Book Reviews

If there is a living American qualified to prepare material for the student of future interests probably law teachers would agree that Professor Kales is the man. He has written a book on Future Estates in Illinois which has made a distinct impression on the law of that state and is recognized elsewhere as a sound and scholarly treatise. He has taught the course on future interests and illegal restraints at Northwestern University Law School for many years, and last year gave the same course at Harvard

Book Reviews

Professor Husband\u27s book deals with two problems, the date of the trial and crucifixion of Jesus, and the legal aspects of the proceedings against him. In both divisions of the subject his conclusions are novel and are supported by able argumentation