Timber harvest planning—A combined optimization/simulation model

A special cascading fixed charge structure can be used to characterize a forest management planning problem in which the objectives are to identify the optimal shape of forest harvest cutting units and simultaneously to assign facilities for logging those units. We describe a four-part methodology that has been developed to assist forest managers in analyzing areas proposed for harvesting. This methodology performs an analysis of harvesting feasibility, computes the optimal solution to the cascading fixed charge problem, undertakes a GASP IV simulation to provide additional information about the proposed harvesting operation, and permits the forest manager to perform a time-cost analysis that may lead to a more realistic, and thus improved, solution.     

OPEC versus the West: A robust equilibrium

Suppose that both OPEC and the West possess stocks of oil which can be extracted at constant and identical cost. Consumption takes place only in the West. Suppose, hypothetically, that the West behaves as a single agent and, more realistically, that OPEC does also. Each agent makes a strategic choice of the pattern of exploitation over time of its own reserve. The Nash equilibrium obtained is “robust” in that it is also a “Stackelberg equilibrium” in which each agent is “right for the right reason.” Further, the equilibrium obtained is equivalent to that obtained when Western oil companies constitute a competitive fringe to the OPEC monopoly.     

Correlates of burnout among public service lawyers

Several hypotheses suggested by the theoretical literature on burnout were empirically tested in an attempt to identify the organizational conditions associated with employee burnout. Public service lawyers in the U.S. (N= 391) completed a survey designed to assess (a) three components of burnout, namely, emotional exhaustion, depersonalization, and feelings of low personal accomplishment; (b) perceptions of several job conditions predicted to be associated these three components of burnout, including workload, role conflict, social support, decision-making policies, and autonomy; and (c) organizational commitment. Results indicate that emotional exhaustion is most strongly associated with role conflict and quantitative workload. Feelings of personal accomplishment were associated with supervisory social support and job level. Depersonalization was associated with role conflict and decision-making policies. Finally, each burnout component is significantly related to organizational commitment.     

CHANNEL FORM AND STREAM ECOSYSTEM MODELS1

A system is proposed to classify running water habitats based on their channel form which can be considered in three different sedimentological settings: a cobble and boulder bed channel, a gravel bed channel, or a sand bed channel. Three physical factors (relief, lithology, and runoff) are selected as state factors that control all other interacting parameters associated with channel form. When these factors are integrated across the conterminous United States, seven distinct stream regions are evident, each representing a most probable succession of channel forms downstream from the headwaters to the mouth. Coupling these different channel profiles with typical biotic community structures usually associated with each of the channel types should result in considerable refinement of the applicability of the River Continuum Concept and other holistic ecosystem models by realizing the nonrandomness of the effects of geo-morphology on stream ecosystems. Thus, this regional perspective of streams should serve to make persons concerned with water resources more aware of the geographical considerations that affect their study areas.     

Climate change and the geography of weed damage: Analysis of U.S. maize systems suggests the potential for significant range transformations

By the end of the century, climate change projections under a “business-as-usual” emissions scenario suggest a globally averaged warming of 2.4–6.4 °C. If these forecasts are realized, cropping systems are likely to experience significant geographic range transformations among damaging endemic weed species and new vulnerabilities to exotic weed invasions. To anticipate these changes and to devise management strategies for proactively addressing them, it is necessary to characterize the environmental conditions that make specific weed species abundant, competitive, and therefore damaging the production of particular crops (i.e. defining the damage niche). In this study, U.S. maize is used as a model system to explore the implications of climate change on the distribution of damaging agricultural weeds. To accomplish this, we couple ensemble climate change projections of annual temperature and precipitation with survey data of troublesome weed species in maize. At the state scale, space-for-time substitution techniques are used to suggest the potential magnitude of change among damaging weed communities. To explore how the geography of damage for specific species may evolve over the next century, bioclimatic range rules were derived for two weed species that are pervasive in the Northern (Abutilon theophrasti Medicus, ABUTH) and Southern (Sorghum halepense (L.) Pers., SORHA) U.S. Results from both analyses suggest that the composition of damaging weed communities may be fundamentally altered by climate change. In some states, potential changes in the coming decades are commensurate to those possible by the end of the century. Regions such as the Northeastern U.S. may prove particularly vulnerable with emerging climate conditions favoring few weed species of present-day significance. In contrast, regions like the mid-South are likely to experience fewer shifts even with a similar magnitude in climate change. By the end of the century in the U.S. Corn Belt, cold-tolerant species like A. theophrasti may be of minor importance whereas S. halepense, a predominantly Southern U.S. weed species at present, may become common and damaging to maize production with its damage niche advancing 200–600 km north of its present-day distribution.     

A post‐earthquake psychopathological investigation in Armenia: methodology,summary of findings,and follow‐up

The post‐earthquake psychopathological investigation (PEPSI) was designed to probe the short‐and long‐term effects of the earthquake in northern Armenia on 7 December 1988 on survivors' mental and physical health. Four phases of this study have been conducted to date, and, overall, more than 80 per cent of a sub‐sample of 1,773 drawn from an initial cohort of 32,743 was successfully followed during 2012. This paper describes the methodology employed in the evaluation, summarises previous findings, details the current objectives, and examines the general characteristics of the sample based on the most recent follow‐up phase outcomes. Despite a significant decrease in psychopathology rates between 1990 and 2012, prevalence rates of post‐traumatic stress disorder and depression among study participants in 2012 were greater than 15 and 26 per cent, respectively. The paper also notes the strengths and limitations of the study vis‐à‐vis future research and highlights the importance and potential practical implications of similar assessments and their outcomes.